Anyone want to have a TB/inj. discussion?

[uglyDougly]

  Admittedly an injector discussion could be percieved as a pi**ing contest, but is anyone game to share a little?

   Doug

[Vosselman]

Hi Doug,
That would be nice. But do you expect another result than you did when testing the Duc injectors. Or is the spread in delivered fuel not what you mean?

[uglyDougly]

  <Or is the spread in delivered fuel not what you mean?>

  It could be that and much, much more.

  Doug

[Scramjet]

I do not know if this is on topic but I do have a question regarding the TB/inj size for a 103" and 107" build.  It may kick off some discussion.

Looking at pulse width on a SERT data recording, what are you looking for to determine if pulse width is near maximum?

I typically have seen numbers in the 6-20 ms range.

ex. 103" with stock 46mm TB 3.9 gm/sec inj pulse width around 6-20 ms under load.
ex. 107" with SE50 TB 4.9 gm/sec inj pulse width also around 6-20 ms under load.

I have heard the number 85% at WOT thrown around.  85% of what.  Is the duty cycle maximum 100 ms?

What should a self tuner look for?

B

Edit: added examples

[uglyDougly]

  First you have to figure out cycle time.
  A cycle is two revolutions of a 4-stroke engine.

  RPM divided by 60 = RPS (revolutions per second)  (6000 RPM / 60 = 100 RPS)

  The time of one revolution = 1 divided by the RPS That will give you the time in seconds. (1 / 100 = 0.010 or 10 thousands of a second or 10 milliseconds)

  10mS X 2 = 20 mS

  85% of 20mS = 17mS

  At 3000 RPM the cycle time is 40mS (check my math) so 85% duty cycle is 34mS.

  The injector is just a solenoid, a doorbell chime mechanism. When you use someone's doorbell you don't notice that the striker hesitates for a couple milliseconds while the field builds up enough to move the core or striker.
  In an injector that millisecond matters. When you're trying to fire the thing once every two revolutions at 12,000 RPM 1 mS is 10% of the time available. at 6000 RPM it is still 5% of the time.
  This is referred to as 'dead time' and it is dependent on battery voltage. There is a table in the calibration that accounts for the variation in dead time thru the battery voltage range. It is part of every firing of both injectors.

  Let's not move on before this is covered to satisfaction?

  Doug

[FLTRI]

Doug,
Maybe it would be a good thing to address how a guy would be able to determine if what he has for injectors are big enough to do the job he's asking them to.
In other words there seems to be a lot of guys who buy bigger injectors because they went from and 88" engine to a 95" or even a 103" engine.
How does a guy know whether he needs bigger injectors or the ones he originally got in the bike are big enough?
Is there a way for him to make a self-determination or does he have to rely on propaganda and/or heresay?

[FLTRI]

Another question:
Since the economy is in a little funk right now, there are still guys who want more power from their bike but now think twice before pulling the wallet out for bigger TBs and want to know if they really need one.

Let's use what I consider the most common example:
Joe owns an '07 bagger. He likes to ride 100-600 miles per day on weekend trips that include back roads and interstates. He doesn't drag race the bike nor is he interested in revving the engine past about 4500-5000 when he's performance riding, mainly because it feels really good to him from 2000-5000 rpms and he doesn't feel there's a need to go any further into the higher rpms.

His bike came stock with a 96" (strokes 88") engine. He figures he can justify going to 103" simply because it only requires a big bore kit to buy and install, rather than a complete tear-down to install a stroker crank as it was with the 88" engines of the past.

He's looking for more bottom end torque and after researching here among other places and people opts for a Woods TW6-6.

He doesn't like the ear-piercing sound of some of the highest peak number producing exhausts, so he opts for a Supertrapp Supermeg because he can adjust the noise level himself before he has it tuned for best performance.

So now he has an engine that is bigger and produces more HP/TQ, so the next thing he naturally thinks about is the size of his intake (TB).

Based on this scenario will he benefit from a larger TB and if so how much and where will he experience the increase?

[axtell]

Is scary to think that 3/4 of the pulse width is directed @ a closed valve

[Scramjet]

  First you have to figure out cycle time.
  A cycle is two revolutions of a 4-stroke engine.

  RPM divided by 60 = RPS (revolutions per second)  (6000 RPM / 60 = 100 RPS)

  The time of one revolution = 1 divided by the RPS That will give you the time in seconds. (1 / 100 = 0.010 or 10 thousands of a second or 10 milliseconds)

  10mS X 2 = 20 mS

  85% of 20mS = 17mS

  At 3000 RPM the cycle time is 40mS (check my math) so 85% duty cycle is 34mS.

  The injector is just a solenoid, a doorbell chime mechanism. When you use someone's doorbell you don't notice that the striker hesitates for a couple milliseconds while the field builds up enough to move the core or striker.
  In an injector that millisecond matters. When you're trying to fire the thing once every two revolutions at 12,000 RPM 1 mS is 10% of the time available. at 6000 RPM it is still 5% of the time.
  This is referred to as 'dead time' and it is dependent on battery voltage. There is a table in the calibration that accounts for the variation in dead time thru the battery voltage range. It is part of every firing of both injectors.

  Let's not move on before this is covered to satisfaction?

  Doug

Doug,

Thank you.  That makes sense.

That tells me that at 6,000 RPM (an assumed rev limit) you should look for a injector pulse of no more than 17 ms.  If the injector pulse width is greater than 17 ms a larger injector (or increased fuel pressure) is needed?

At 3,000 RPM a pulse width of 34 ms calls for a larger injector?

Since my VE's are max at 3,000-3,500 RPM, that is where I should look for 85% duty cycle?

And at the rev limit for a reality check?

B

[uglyDougly]

   Good suggestions Bob.

 Injector sizing.

 The amount of fuel required is directly, inextricably tied to the amount of air the engine can process. (This, of course, assumes you actually have control of the fuel-air ratio.)

 Most Otto Cycle engines (spark ignited gasoline fueled) will use around 1/2 lb of fuel per HP per hour. A 40HP load should use 20 lb of fuel in 1 hour.

 The engineering community refers to this as Brake Specific Fuel Consumption. Now you see why injectors are often rated in lb/hr!?!?!?

 The grams-per-second value in the ECM Tuning Constants window of the Master Tune software describes the injector size for the equation that calculates injector pulse width.  When we're done figurin' how much fuel we need we'll convert from lb/hr to gr/sec.  Weight-to-weight/ time-to-time.

  Since the predominant device for measuring the output of our motorcycles is the chassis dynamometer we measure the power at the rear wheel. There are losses incurred through the drive-train.
  My injector spreadsheet assumes 15% loss from crank to rear wheel. This comes from the 101 HP Buell White Lightning which pretty consistantly showed 86 HP on a Dynojet dyno.
  Let's not get side-tracked with an argument about what the losses are, 15%?, 10%. For injector calculation where you don't want to run out of fuel, it works to be conservative or optimistic about the power you will make.

  For a 100HP build I assume 115 HP at the crank.
 A BSFC of .550 works and is more conservative for an air-cooled engine.
 Since we know about injector 'dead-time' it's obvious that at 6000 RPM with 20mS a dead-time of 1mS is 5% of that. There is some time for the injector to open and close also. That time remains constant whether you leave it open for 16mS or 3.5 mS as does the 'dead-time'.

 'They say' a duty cycle of 80% (some of 'them' say 85%) keeps you out of trouble with 'dead-time' and open-close time.
 At low RPMs 80% works fine, but it gets you deep in trouble at high RPMs.

 The problem, or so I've read is literally valve float. When the disc or pintle is between open and close and switched it will float and damage itself. Just like the poppet valves in our engines?

 115 HP X 1.15 + 115 HP @ the crank

 BSFC of .500 X 115HP = 57.5 lb/hr

 57.5 lb/hr divided by 80% Duty Cycle = 71.875 lb/hr

 71.875 lb/hr divided by two injectors = 35.9375 lb/hr injectors.

 The H-D Weber injectors from '02 -'06 flow 34 lb/hr at 3 Bar.

 The flow thru an orifice changes as the square root of the pressure differential.

 sqrt of 3 Bar(rating pressure) = 1.732,   sqrt of 4 Bar (H-D regulator) = 2

 2 divided by 1.732 = 1.155

 34 lb/hr X 1.155 = 39.26 lb/hr

 The Weber IWP 043 and IWP 162 flow enough.

  Let's see how the later injectors will work.

 The H-D PN 27625-06 injectors flow 28.5 lb/hr.

 28.5 lb/hr @3 Bar X 1.15 (flow increase with 4 Bar) = 32.78 lb/hr
 
 Go back to our requirement, 35.9375 lb/hr injectors

 We're 9% short, but it will work, maybe.

  I would guess you would be able to get the AFR you need at WOT until the PE-afr table kicks in, then you will not be at the target AFRs of that. But, then again, if you've just built your engine why would you want to kill all the power with too much fuel?
 That's my opinion showing!!

 Get it?  we'll cover this 'til it sinks in.

 Doug

[uglyDougly]

  Thanks for chiming in Ron.

  Way back in the VW Bosch CIS (that's the Constant Injection System) days, Bosch said they had tested the performance of Otto Cycle engines and there was no (maybe they said 'little' I don't remember) difference between short injector duration and constant injector flow.
  Those were pre-emissions days, so it probably does have an affect on emission, but not so much on power.
  Chris Schroeder of DTT, says you shouldn't have greater than 50% duty on 'Y' manifold engines. That would be from the fuel-sharing/robbing standoint. Any of us who have done custom calibrations, know that is not the practical limit. But, it probably doesn't make it easier to tune them well.

  But, if shorter duty cycle were critical for emissions why did the MoCo put in smaller injectors from '06 onwards.
  The emissions thing is way over my head.

  I have read (don't remember where) that spraying some fuel on a closed, hot valve works to help vapourize the fuel and Reggie has put a digital scope on one and says that the injector spray starts earlier with an increase in engine size in the ECM Constants section.
  That implies something, although I don't know what.

  Doug

[axtell]

My honest opinion is that there is probably very little over your head Ron

[Scramjet]

Am I running out of injector with my SE50 TB and 4.9 gm/sec injector on a 107" build?

A data run is attached.  At only 5108 RPM the pulse width is at 19.08 ms and the MAP reads 98.2.



[attachment removed after 60 days by system]

[-SeabrookTrickBagger]

Doug,

Hopefully, my question below does not divert your intended path in regard this discussion.

I find this part of your explanation of interest to me since it addresses reality of the HD FI engine:  The flow thru an orifice changes as the square root of the pressure differential.

  sqrt of 3 Bar(rating pressure) = 1.732,   sqrt of 4 Bar (H-D regulator) = 2

Would this be a fairly accurate calculation:  an injector flowed/rated at 6.1 gps at HD pressure would equate to about 5.7 at 3 bar?  I am not a mathematician and I only had one college level math course in quantitative math skills which was not enough.....  .

FWIW, the DTT TCFI does not ask for the pressure used to achieve a flow rate at the time you enter the injector flow rate (in grams per second) in parameters.  Since the "industry standard" appears to be 3 bar, then the 3 bar flow rate is used in this parameter for injector flow rate without any real thought.  When Schroeder was asked about this, he said it did not make any difference:  use 3 bar or HD pressure injector flow rates.  He probably meant it was "mot snix" as far as a street engine is concerned.

Of course, Schoeder is no dummy.  His printed recommended injector sizes for common plenum  Y manifolds is considered WAY too high in actual practice for engines which operate at rpms other than WOT, though.

[uglyDougly]

  Scramjet asked; 'Since my VE's are max at 3,000-3,500 RPM, that is where I should look for 85% duty cycle?'

   Your pulse width will be greatest at your torque peak, which is your Volumetric Efficiency peak.

  Hint: the fuel table is an analogue of the torque curve.

   But, as you start calculating cycle time you realize that time is the problem. At your torque peak you have lots of time realtive to your power peak.

  Guess what? The injector flow capability relates directly to max air-flow, max-power where time is getting short. That is where you should expect to run out of injector capability.
  If you're running out at the torque peak, and not at the power peak your torque is dropping off too fast by conventional IC engine standards, but it doesn't matter, you need larger injectors.

  If your torque drops off typically, it's all over already. Right now you're at 81% @ 5108 but it shouldn't get better.

   STB, my lb/hr numbers come from an injector flow bench. Here we go with the 'flow-bench', dyno, flow-bench, discussion.
   The short story is, if the numbers are repeatable you can work with them. In this case they fall close to the calculated gps and cc/min values given by the mfg.
  With injectors the point is to size them large enough to not run out of fuel. We could probably run up to 90% on a 6000 RPM engine, but if our values vary a little, why take a chance?

   About injector values in MT; The calculated Gr/Sec (gps) for the Weber IWP069 (yellow band)  is around 6.1. In fact they work better in the MT-RT-DL with a value more like 5.6-5.8.
   Why? We're using that number to manipulate the software to give us enough VE overhead to tune. And that is about H-D/Delphi assuming that these engines will never process as much air as you guys are getting them to.

   I can say 'you guys' 'cause I don't build H-D engines. If I need that done I'll just see Bob Wright.

  Quote from dirty Harry; 'a man's gotta know his limitations'

  Doug

[axtell]

Doug...Could you call me @ 1-800-704-3201 Ron

[Scramjet]

  Scramjet asked; 'Since my VE's are max at 3,000-3,500 RPM, that is where I should look for 85% duty cycle?'

   Your pulse width will be greatest at your torque peak, which is your Volumetric Efficiency peak.

  Hint: the fuel table is an analogue of the torque curve.

   But, as you start calculating cycle time you realize that time is the problem. At your torque peak you have lots of time realtive to your power peak.

  Guess what? The injector flow capability relates directly to max air-flow, max-power where time is getting short. That is where you should expect to run out of injector capability.
  If you're running out at the torque peak, and not at the power peak your torque is dropping off too fast by conventional IC engine standards, but it doesn't matter, you need larger injectors.

  If your torque drops off typically, it's all over already. Right now you're at 81% @ 5108 but it shouldn't get better.

  Doug

WOW, when I do the actual calculation using 6200 rev limit, VE relatively contant and AFR demand constant I get 100% duty cycle of 19.35 ms.

85% of 19.35 ms = 16.45 ms ------ I will be over well over 85% duty cycle and will be close to 100% duty cycle even before Power Enrichment starts droping the AFR to 12.5 over time at WOT.

Is this correct?

B

[ederdelyi]

These aren't bad for ball park figuring ... remember that you need to use crank power, not wheel power.

http://www.injector.com/injectorselection.php

http://www.rceng.com/technical.aspx



If you look around there are some on the net that use other methods to arrive at the figures, but they should all arrive at pretty much the same results. I have a fuel injector calculator tool from Performance Trends that is pretty nice, works well with my engine simulation software and gives the option several different methods of calculation. Just makes it easier, so you don't have to remember the formulas. I found HD's BSFC to run in the .55 to .6 range, getting them lower is a challenge, but it can be done.

[nc-renegade]

 
  I have read (don't remember where) that spraying some fuel on a closed, hot valve works to help vapourize the fuel

I think that has merit.

[uglyDougly]

   Rob's Dyno has my spreadsheet on his site;  http://www.robsdyno.com/injectors.htm
  Again, I did mine for some arbitrary loss factor for motorcycles.

  Scramjet, it depends on how fast your torque drops away after the torque peak.
 The pulse-width will be roughly 20% shorter if your torque drops 20% from 4000 to 6000, but the time decreases 33.3% from 4000 to 6000. Looks like a loosing proposition to me.

 Doug

[-SeabrookTrickBagger]

 
   STB, my lb/hr numbers come from an injector flow bench. Here we go with the 'flow-bench', dyno, flow-bench, discussion.
   The short story is, if the numbers are repeatable you can work with them. In this case they fall close to the calculated gps and cc/min values given by the mfg.
  With injectors the point is to size them large enough to not run out of fuel. We could probably run up to 90% on a 6000 RPM engine, but if our values vary a little, why take a chance?

  Doug

Thanks.  The correct factors were in your earlier post.  6.1 gps at 4 bar equals 5.3 gps at 3 bar, not 5.7 gps as I "guessed." 

[whittlebeast]

If you have Microsoft Excel this sheet will cover everything that you will ever need in calcing injector sizes.  It was developed when I was doing a 7000 RPM, 140 HP two stroke EFI motor.  In that case, I needed 800 cc injectors.

http://www.ncs-stl.com/fuel/ReqInjectors03.xls

Yellow cells are input cells and Red are critical output cells.  If you use the program MegaLogViewer to look at the data log you can turn on Duty Cycle 1 and Duty Cycle 2 and have the software calc it for you automaticly.  The first time you activate the function you will have to answer t questions.  I think the answers are .5 and 1 for a Harley.

Hope this helps and have fun tuning.

AW

[Scramjet]

AW,

Thanks for the info.

Some of this does not add up.  If you look at the numbers for the commonly used 4.9 gm/sec H-D injectors they can provide about 38.9 lbs/hr max.  That means that these injectors will not support most 107" (and above) builds.  They would run out of injector limits around  115 rear wheel HP (actual not corrected) or 130 crank HP (actual not corrected).

The contradiction is that many builds producing that kind of power are running those injectors.

B

[whittlebeast]

If you push the duty cycle to 90% and you use the opening time of .7 ms that the code appears to be using and things are fairly close.  If you do an o2 enabled SERT data log of one of these bikes at WOT and close to max RPM and email me the DM2 or DM3 file, I can post the duty cycle graphs along with lots of the other stuff we can see.

AW

[uglyDougly]

<4.9 gm/sec H-D injectors they can provide about 38.9 lbs/hr max. >

 I haven't memorized the SERT, MT injector values, but these look like the Weber Pico IWP043 and IWP162 (brown band and white band, pre '06)

 Bob Wright put together his own 95CI engine with K billet heads (seconds) an experimental TC3G cam, and a prototype 54mm TB.
 I tuned it and it made 117HP and the injectors where at 86% duty cycle.

 Doesn't look like there's any disagreement there?

 That would give you a couple percent overhead and if you revert the AFR table to values much richer than 13.2 it might not get you quite the fuel you expect.
 Even in that case it will make all of the power, just go a little lean , just a little, and they don't mind that on the top. (It speeds up the burn rate. Hint; RPM/time)

  When the numbers work out, there have to be other reasons or more to the story. That's where you have to be an expert interviewer to drag all of the information out into the light.

  If the pulse-width is known and it equals the time for a complete cycle, you're done! There is no more, and as the engine increases RPM there is less time, so less fuel.

  Detecting when the injectors are maxxed can be very difficult, until you look at the data.

 That's the reason I bothered to learn this stuff. It saves a lot of time.

 At the V-Twin Expo we (Ed Dahir and I) talked with a guy who's doing his own tuning. He's a Mechanical Engineer so he 'gets it', understands.
  He's using a Twinscan II+ and two O2 sensors to collect data. He was surprised to find out that there was a PE_AFR table that messes with the tuning AFRs. Unfortunately, he had already purchased the Super Pro Tuner which doesn't support access to the PE_AFR table. He understood the effect of that table and was disappointed that nobody else had pointed that out to him.
 He has a 117 with a stock TB and stock injectors.
 Since then Ed told him he needed larger injectors (stock '06 and later Delphi injectors are 24 lb/hr) and I told him he will need larger injectors, plus I informed him that the injectors H-D sell for the 50mm TB are only 28 lb/hr, which he had already ordered from a dealer.
 I offered to confirm the flow rate of whatever PN he ordered but he didn't get back to me.

 Test Time!!

 How much power will the 28 lb/hr injectors support?

 Doug

[Scramjet]

The SE50 TB comes with the 4.9 gm/sec injectors (HD PN 27797-07).  I calculate that to 38.8 lbs/hr at rated pressure.

B

[Scramjet]

If you push the duty cycle to 90% and you use the opening time of .7 ms that the code appears to be using and things are fairly close.  If you do an o2 enabled SERT data log of one of these bikes at WOT and close to max RPM and email me the DM2 or DM3 file, I can post the duty cycle graphs along with lots of the other stuff we can see.

AW

I will take you up on that.  May take a couple of days.

B

[Scramjet]

How much power will the 28 lb/hr injectors support?

Doug

I will take a shot at it.  About 102 HP (uncorrected) at the crank.

B

[uglyDougly]

   Scramjet that's as correct as you need to be to decide whether you need larger injectors.

  It's no like I'm an expert on this. You just don't want to start too close to the limit.

  I was mistaken, the stock H-D post '06 delphi injectors are 28 lb/hr, the SE50 injectors are 32 lb/hr both of these at 3 bar.
  When I put the right numbers into my spreadsheet I get the following.

 The S-E 27654-06 injectors will be flowing almost 38 lb/hr at 4Bar and that is good for 100 HP with a normal margin.

  Think that'll work on a 117?

  Doug

[ederdelyi]

Using two different methods (peak HP & BSFC, displacement & VE) I got 97.4 HP at a peak HP RPM of 6200 and 85% max duty cycle for a 28 lb/hr injector with 55 PSI fuel pressure ... 96 CI motor.

[uglyDougly]

  Ed, with the wrong data from me, you got the same answer as I did.(with the wrong data)

  If I may overstate, running out of fuel is the most common problem. Too much fuel is rare and just requires tuning to fix.

  Doug

[eddfive]

I have tuned several 117Ci motors.  I have them make 120-130HP typically.

130HP=36.13lbs/hr which equals 4.55gr/sec.
150hp=41.69lbs/hr which equals 5.25gr/sec

If it were my decision and I was buying injectors I would go with the 5.32gr/sec (this is what Marren sells)injectors so I had some head room and this would allow the Engine Parameters in all of the S/W tuners to be set at 117CI and then you could just adjust the injector values to get the VE values below the limit everywhere.  The 4.89gr/sec SE injectors would work but there may not be enough head room which would mean adjusting the Engine parameters. 

My question is do you think you can really get too big of an injector? 

[whittlebeast]

Here is a great bit of trivia

Did you guys know that (at least in a Sportster) if you put in identical VE tables front and rear, you will still get 55% of the fuel to the front injector and 45% of the fuel comes out of the rear injector.

BUT..  At wide open throttle the injectors get the same PW.

AW

[Scramjet]

Scramjet that's as correct as you need to be to decide whether you need larger injectors.

It's not like I'm an expert on this. You just don't want to start too close to the limit.

Doug

We spoke for while at the 2008 V-Twin Expo.  It convinced me that you are enough of an expert for me to listen and learn what I can learn.

I would like to investigate further with hard facts and data.  I am an engineer in the aerospace industry so I like to work from controlled experiments.  I will get a data run done with the VE, AFR and PE tables at their final settings and we all can look at the injector pulse width.  That is probably the best next step.

This has been some good info.  You can usually count on the technical community of people on HTT to spark a lively and informative discussion.

Thanks, B

[ederdelyi]

>>My question is do you think you can really get too big of an injector? <<

My non-expert opinion/answer:

Yes. A too large injector can cause low speed driveability/tuning problems. Very low duty cycles are not good, the injector dead time becomes a major portion of the duty cycle ... it's like trying to fill a water glass with a fire hose. This is actually a problem often encountered with Turbo/Supercharged EFI setups where high fuel pressure and large injectors are required by the engine when boost is present, but the engine needs far less fuel and fuel pressure when boost is not being generated and RPM is low. Some systems actually have variable fuel pressure regulation to help deal with the problem. Some use multiple injectors that are sized differently.

[FLTRI]

Along the same line, we have replaced over-sized injectors from bikes that customer's have installed and the bike picks up throttle response, and better overall drivability.
Another bigger is better mistake IMO.

[uglyDougly]

  Since all of the injector examples covered so far have been for injectors that are small or marginally small, and the fact that there are only a few injectors that will fit these applications, where is this problem of too large injectors rearing it's ugly head?

  Weber side-feed Red (H-D) or Green (Ducati), these are both 3 Bar applications, 31 lb/hr, approx. 86 HP

  Weber Pico IWP043 and IWP162, 34 lb/hr @ 3 Bar, 39 lb/hr @ 4 Bar,  approx. 106 HP

  Weber Pico IWP069 (yellow band) 48 lb/hr @ 3 Bar, 55.8 lb/hr @ 4 Bar,  approx. 150 HP

  Weber Pico IWP189 (purple band Ducati OEM 1098) 54 lb/hr @ 3 Bar, 62.51 lb/hr @ 4 Bar,  approx. 158 HP (80% duty cycle for 11,000 RPM)

  Weber Pico from V-Rod (haven't had a set on the flow-bench)  around 37.5 lb/hr @ 3 Bar, 43 lb/hr @ 4 Bar, approx.  116 HP

  Delphi H-D PN 27625-06, 28.5 lb/hr @ 3 Bar, 32.7 lb/hr @ 4 Bar,  approx. 88 HP


  Delphi SE 500 TB injectors, 32 lb/hr @ 3 Bar, 37.2 lb/hr @ 4 Bar,  approx. 100 HP


  Kuryakyn Delphi injectors ??

  The culprits must be the IWP069 unless someone has sourced the 1098 injectors from Competition systems.

  The example Ed gave for an engine that is running double the injector size because it is turbo-ed, has merit.
  Unfortunately, I don't see the IWP 069 causing any problems all by themselves. Maybe if they were put on a stock 65HP engine. And that would make Chris Schroeder happy at something under 45% duty cycle.

   The question has to be; In the example of the bike that 'we have replaced over-sized injectors from bikes that customer's have installed and the bike picks up throttle response, and better overall drivability' was the bike tuned completely before the injectors were replaced and tuned again after the smaller injectors were installed, or were the injectors replaced and then the bike tuned?

   It seems to me that too small is a frequently recurring problem but too big is a theoretical problem.

  Doug

[Steve Cole]

Has anyone bothered to check the spray patterns and spray angles of all these injectors? Just because you know what they flow doesn't mean its not too big or small as the angle and patterns have a lot to do with how it runs! Wall wetting and droplet size is a big issue when you talk about throttle response and low speed power (<4000 RPM).

[Scramjet]

 
Delphi H-D PN 27625-06, 28.5 lb/hr @ 3 Bar, 32.7 lb/hr @ 4 Bar,  approx. 88 HP

Delphi SE 500 TB injectors, 32 lb/hr @ 3 Bar, 37.2 lb/hr @ 4 Bar,  approx. 100 HP

Doug

Doug or Bob,

This still does not add up as a true ceiling for the above listed injectors.  Bob just tuned a 2007 with stock TB (and the stock 3.9 gm/sec injectors?) to 113HP/123TQ.  The correction factor is .96 so the uncorrected HP is even higher.

Bob, did you change the injectors?  It is Biggzed's build in the Dyno section.

I will try to get a data run tomorrow using the HD 4.89 gm/sec injectors in the stock SE50 TB for a reference point for pulse width.  I should be able to get a Dynojet 250i dyno run next week to follow it up.

B

[ederdelyi]

 
Delphi H-D PN 27625-06, 28.5 lb/hr @ 3 Bar, 32.7 lb/hr @ 4 Bar,  approx. 88 HP

Delphi SE 500 TB injectors, 32 lb/hr @ 3 Bar, 37.2 lb/hr @ 4 Bar,  approx. 100 HP

Doug

Doug or Bob,

This still does not add up as a true ceiling for the above listed injectors.  Bob just tuned a 2007 with stock TB (and the stock 3.9 gm/sec injectors?) to 113HP/123TQ.  The correction factor is .96 so the uncorrected HP is even higher.

Bob, did you change the injectors?  It is Mayor's build in the Dyno section.

I will try to get a to get a data run tomorrow using the HD 4.89 gm/sec injectors in the stock SE50 TB for a reference point for pulse width.  I should be able to get a Dynojet 250i dyno run next week to follow it up.

B

In the above examples from Doug, it appears he may be stating wheel HP figures.

If you use:

CrankInjHP ~= ((flow * dutycycle)/BSFC) * # cyls

then

Delphi H-D PN 27625-06, 28.5 lb/hr @ 3 Bar, 32.7 lb/hr @ 4 Bar

((32.7 *.85) *.55) *2 = 101 HP (crank) or roughly 86 HP (wheel)

using a 85% DC, a BSFC of .55, and ~15% drivetrain loss

Delphi SE 500 TB injectors, 32 lb/hr @ 3 Bar, 37.2 lb/hr @ 4 Bar

Should be ~114 HP (crank) or roughly 99 HP (wheel)

Using the same parameters

Unless I'm missing the boat (likely).

Could be that some of those bigger motors have better BSFC than the typical figures used to approximate the injector size needed. I agree with Doug that in most cases the available injectors are not grossly oversized for the applications being discussed here and should not be a major problem for low speed operation/tuning. The same 32 lb/hr injector example above when used on a motor with a .52 BSFC would yield 124 crank HP as the max with all other conditions the same.

Spray patterns and spray angles ... a factor to consider, no question. Again, the choices available for these engines seems somewhat limited from what I've been able to discover.

[uglyDougly]

  You're not missing the boat Ed, most of the injector calculators on the internet are for crankshaft HP. I'm using a spreadsheet that I did that compensates for the losses from the crank to the dyno drum. I've been using 15%
  Ron from Axtell told me that the losses are probably higher than 15% from crank to drum.

One other thing. A lot of injectors are rated at 3 Bar (kinda 'industry standard' thing I suppose) so my spreadsheet lists the 3 Bar rating but calculates differently depending on the fuel pressure entered.

  Scramjet, you accounted for that, but you're an engineer.

  So, I apologize for not putting all of the factors out there initially. I have probably made it more confusing than it has to be as I have referred to the 3 Bar ratings of a lot of the injectors.

  If I'm testing injectors, I can certainly see the spray patterns. The IWP069 is a pencil stream, definitely not a mist, and I'm sure that changes things. I only say 'I'm sure' rather than 'I know' because I don't pretend to be able to predict what and how much it will change.

   The IWP069 comes stock on the Ducati 748R and it's in a 'shower' position directly above the throttle blade (2-54mm throttles on a 45CI engine.)
   These things idle really poorly because the fuel puddles on the throttle blade and gets sucked around the perimeter at idle and they go rich momentarily when the throttle is cracked.

  I used the IWP069s on a 124 in '04 and it tuned and ran just fine.

   One customer put the K 120HP kit on a M-M bike and purchased a 56mm HPI TB with 4.5 Bar pressure regulator and the IWP069 injectors. The expectation was that it would make 120HP.

  When I calculated the injector requirement, I knew that the injectors were way larger than they needed to be. I installed a pair of IWP043 (probably from the 124 previously mentioned) and tuned it.
  Why was the injector capability so high? I could only venture a guess but it was probably because so many people were tuning those things with PCIIIs and the PCIII would need values in the 170% and 180% range when using the original cal for a 60HP engine. The PCIII sees the pulse-width coming from the ECU and changes it by percentage. A value of 0 on the PCIII map means that there is no change, 10 is 10% longer.
Dynojet may limit the total increase to something less than 99%. But I don't know off the top of my head, I don't use PCIIIs on Harleys and most other applications don't need mega adjustments.

  Anyway, calculating the requirement created a non-problem.

Doug

[uglyDougly]

  How about a wrap-up on the subject of injector sizing?

1) Determine the rear wheel HP of your build.
2) Multiply that by 1.15 or more to get crankshaft HP
3) Divide CS HP by the number of injectors to determine the HP per injector
4) Using a fairly conservative BSFC, like .550 lb/HP/hr, multiply the HP/inj X .55 to get the injector static flow requirement in lb/hr
5) Divide the static flow requirement by .80 which is the 80% duty cycle recommended to get the lb/hr you will want
6) Find the static flow or maximum flow rating of the injectors in question and determine at what pressure they are rated, typically 3 Bar
7) If the injectors are rated at your fuel pressure (3 Bar for M-M bikes, 4 Bar for Delphi) chose an injector that flows more than the calculated value 5) above
If the injector is rated at 3 Bar and you are using a 4 Bar Delphi system, multiply the 3 Bar rated static flow by the difference of the square roots of the two pressures, in this case it is 2 (sqrt of 4) divided by 1.732051 (sqrt of 3) = 1.154701
9) Then chose an injector that flows more than the calculated value

  Does that make sense?

  Doug

[ederdelyi]

Works for me, that's pretty much what I do now.

Wanna tackle TB sizing next? :>) I'll get the popcorn ready.

[Scramjet]

Doug et al,

Here is my data run from today.  I am running out of injector pulse width.  It is in the 19.6 ms range at 6,000 RPM.  That is a 98% duty cycle!  It appears that there is no headroom left which tends to support Doug's projections or at least this build seems to be at the limit of the 4.89 injectors.  BTW, I am hoping for TQ/HP in the 110-115 range with this build.

Screen shot attached.

B


calculations:

RWHP   115
CSHP   132.25
# of inj   2
hp/inj   66.13
BSFC   0.55
flow lb/hr   36.37
duty cycle   0.85
desired inj flow   42.79
      

   gm/sec   lb/hr
SE inj   3.9   30.93
SE inj   4.89   38.78
SE inj   5.3   42.03


[attachment removed after 60 days by system]

[ederdelyi]

Hey Doug,
I did want to ask you your opinion about injector flow testing. I know that the OEM flow tests are static tests (100% DC) and that the reason they are tested this way is to ensure that the orifices and pintle are properly machined. When you test for flow rates do you use static or pulsed testing? I've done it both ways, just curious how you do it.

[uglyDougly]

  Very interesting that you would ask Ed.

  My first introduction to an injector flow bench was when one was purchased by a shop where I worked. It was the ASNU.
  At that time the system could test at a variety of frequencies, (RPM/2) but not at static flow (WOT.)
  My experience with that made me ask how any manufacturer could sell a product with such a wide variation in performance. The pulsed flow of a bunch of injectors could vary by more than +- 10%.
  When I went to work at Silverback, Fred purchased a new ASNU bench and it supported a static flow test.
  Lo and behold a bunch of very un-matched injectors  were within about 1.5% at static flow.

  It's clear that the manufacturer uses the static flow spec to sell some kind of repeatability to another manufacturer, but in practice they are all over the map. The static flow spec has no bearing on the mode we are supposed to be operating these things.

  So, Scramjet, your injectors are probably well matched at 100% duty cycle but most likely, not well anywhere else.

  When I match a set, I test them at, at least 3 points within the operating range of the application. 600, 2500, 5000 for H-Ds and 2500, 5000, 10,000 for Ducatis.

   A friend of mine worked at the MoCo (his tele # is no longer in use?!?) but he told me that their cals are performed with matched-from-the-factory, calibration quality injectors.

   This says to me that no motorcycle that was sold by the MoCo or any other manufacturer for that matter, actually met the emission standards that they were certified for. It also explains why the MoCo added dual O2 sensors. It ain't 'cause they wanted to spend more $$$!!??

   Marty at Ducati Seattle just discovered that mis-matched injectors make an application with a single O2 sensor exhibit drivability problems. This was a year after he read my article on mis-matched injectors. I suppose he thought that it couldn't happen to him. He called me to tell me I was right!

   Ed, what's your experience testing injectors?

  Doug

[pikeslayer]

 At the V-Twin Expo we (Ed Dahir and I) talked with a guy who's doing his own tuning. He's a Mechanical Engineer so he 'gets it', understands.
  He's using a Twinscan II+ and two O2 sensors to collect data. He was surprised to find out that there was a PE_AFR table that messes with the tuning AFRs. Unfortunately, he had already purchased the Super Pro Tuner which doesn't support access to the PE_AFR table. He understood the effect of that table and was disappointed that nobody else had pointed that out to him.
 He has a 117 with a stock TB and stock injectors.
 Since then Ed told him he needed larger injectors (stock '06 and later Delphi injectors are 24 lb/hr) and I told him he will need larger injectors, plus I informed him that the injectors H-D sell for the 50mm TB are only 28 lb/hr, which he had already ordered from a dealer.
 I offered to confirm the flow rate of whatever PN he ordered but he didn't get back to me.

 Test Time!!

 How much power will the 28 lb/hr injectors support?

 Doug

Hey Doug & Ed.  Don here.  Just joined the forum.  Looks like a great forum.

Yeah, I ordered the SE 4.89 g/s.  Unfortuneately I took a somewhat un-technical approach.  I knew guys were able to tune 117"s with the old stock injectors (4.2 g/s).  So, I figured 4.89 would work for me.  Well, I gues we'll find out.  When I get them and install them I will do a data run and post it.

By the way, thanks a lot to you and Ed for all the help while I'm getting this 117" running.

[ederdelyi]

>>what's your experience testing injectors?<<

Well, like a lot of other things, I likely only know enough to be dangerous!

I don't own an injector flow bench (didn't sleep at a Holiday Inn either) but I have access to one, among some other neat stuff when I ask nicely.

My experience pretty much matches what you stated. It's how I got started on testing them and matching sets of injectors. I was having problems with tuning some hi-po V-8's and the light went on that the problems were injector related. It was an eye opener to find such a variance on a "precision" part. Since then, I flow test and match all injectors or pay to have it done if I can't do it myself.

[ederdelyi]

>>Hey Doug & Ed.  Don here.  Just joined the forum.  Looks like a great forum.<<

Welcome Don, yep, lots good folks here.

[uglyDougly]

  Hey Don, good to hear (see?) from you.

 
  Maybe it's just me getting old, but there seems to be a philosophical side to everything.

  Whenever you start to take a closer look at anything, but engines in particular you don't find out that it's going to be easier.
  Once you've looked and found the answer (it's harder), only denial will let you go backwards.

  I have resigned myself to the fact that if it ain't gonna be easier, at least with the knowledge, I can make it better.

   Doug

[uglyDougly]

  Here are two graphs of 4 1098 injectors that I just tested today.

  Hope it actually posts!!

  Doug



[attachment removed after 60 days by system]

[-SeabrookTrickBagger]

  How about a wrap-up on the subject of injector sizing?

1) Determine the rear wheel HP of your build.
2) Multiply that by 1.15 or more to get crankshaft HP
3) Divide CS HP by the number of injectors to determine the HP per injector
4) Using a fairly conservative BSFC, like .550 lb/HP/hr, multiply the HP/inj X .55 to get the injector static flow requirement in lb/hr
5) Divide the static flow requirement by .80 which is the 80% duty cycle recommended to get the lb/hr you will want
6) Find the static flow or maximum flow rating of the injectors in question and determine at what pressure they are rated, typically 3 Bar
7) If the injectors are rated at your fuel pressure (3 Bar for M-M bikes, 4 Bar for Delphi) chose an injector that flows more than the calculated value 5) above
If the injector is rated at 3 Bar and you are using a 4 Bar Delphi system, multiply the 3 Bar rated static flow by the difference of the square roots of the two pressures, in this case it is 2 (sqrt of 4) divided by 1.732051 (sqrt of 3) = 1.154701
9) Then chose an injector that flows more than the calculated value

  Does that make sense?

  Doug

BTW, thanks for the synopsis.  Yes, it makes sense.

[-SeabrookTrickBagger]

While we can do all the calculations we need to do, don't we need to consider the choices made by the ECU software creators?

I am still curious if the software creators for the FI ECUs somehow use a 3 bar or 4 bar calculation in their software:  did they choose one when they wrote the program?  In other words, if you put "5.3" in the parameter "gps injector size" slot, is the ECU making its calculations to achieve the HP you entered in parameters, say 135 CS HP, at 3 bar and adjusting the calculations for the specific bike the unit is installed in such as a delphi 58 to 62 psi bike?  In other words, does the ECU want you to enter industry standard, 3 bar, in the parameter slot of injector flow rate or the true operating pressure injector flow rate of your injector/bike?  I asked Schroeder about this, and he said "it does not matter."  Kinda think it does matter, BWTFDIK.  In my case, it is the difference between 5.3+ gps at 3 bar and 6.1 gps at 4 bar.  FWIW, the bike starts and runs a heck of a lot better using 5.3 than 6.1 numbers in parameters which leads me to think the DTT TCFI IId software is using 3 bar for its software calculations and MAYBE making software adjustments for the actual operating pressure of the specific bike (which adjustment would be nothing more than the square root calculation posted by Doug).  My injectors were flowed at 6.1gps at 58 psi by Marren.  Again, WTFDIK.

[-SeabrookTrickBagger]

Doug,

BTW, would using a .55 BSFC instead of .5 BSFC would, for example, be the difference between a 5.39 gps injector and a 5.91 gps injector or about 5 lbs/hr on a 137 CS HP engine?  FWIW, another posters suggested use of an 85% duty cycle splits the difference between these two "extremes."

[uglyDougly]

   STB, I don't know that Marren resizes them, but they do match them. Ed from The Dyno Difference, bought a set for his 124 and they rated them just like the Yellow IWP069s.

 The injector sizing in the software is used to calculate the pulse-width, smaller injector value, longer pulse-width and vice-versa, why Chris would say it doesn't matter, I don't know except that you really need to put the value range in that works.

 Right around the turn of the century (the most recent one) EMC used to resize the M-M side-feed Weber injectors for $69.
 The company traded hands (I think because the guy who was doing the resizing, disappeared) and the new ownership didn't like to do the old ones, but they were re-sizing the Pico injectors.

 I purchased a few of the last of the oversized side-feeds from them and then Dan Fitzmaurice sent me a box full of M-M crap with a few more of the O.S. ones.
 Because they were reamed with teeny-weeny carbide reamers, the pulsed flow of these things is all over the map. I'm not sure if I can even get a matched set for my own pile.

  I think everyone who's doing tuning these days (the ones who actually calculate the injector requirements) are using somewhere around 80%. 'They' have been saying that for years, whomever 'They' is.

 When I'm doing a bike that revs to 11,000 RPM I'll give myself more head-room but the reality is, you don't always have many choices. Adjustable fuel regulators work for that.

 The MotoGP bikes are using 10 Bar pressures and high flow peak-and-hold injectors to keep the duty cycle within acceptable limits at 20,000 RPM. They need 32 bit processors to break the time into high enough resolution at those speeds.

  STB, if you put the wrong numbers into an equation yo umay get the result you want but not the result you need.

  That .55 BSFC is about how efficient you designed your engine. If you can improve the BSFC by 10% that's good. That's not saying that I have any idea what the actual BSFC of the engines I'm tuning is, but 'They' say (this is the engineering fraternity) that .5 BSFC is near the best you can get with an Otto Cycle engine.

  The BSFC number has to know how much friction your engine has as well as the drive-train losses. Ron has an engine dyno and he has a good idea of what they make at the crank but he has to calculate what the friction losses are.

   Maybe the saving grace of this whole injector sizing thing (since we're really not accounting for a lot of the losses) is that the the Dynojet reads so high, the equation actually gets it close.

  Having absolutely no idea about most of what goes on with our engines, I'm constantly amazed at how well a few equations actually work.

 Doug

[-SeabrookTrickBagger]

Well said.

Marren did send flow sheets to me when I ordered the injectors at my desired flow rates at the desired pressure.  I don't know how they do it, but.........  .  I might take another look at that flow sheet.

Understood ------- about .5 and .55 BSFC.

[-SeabrookTrickBagger]

Since I don't do what you do for a living, making mistakes is part of my learning process.  As Brig. General Prather told me years ago:  It is not the mistakes you make son, it is how you recover. 

I certainly make at least my share of mistakes and I post many of them on this website for all to see.  Fortunately, or unfortunately, my mistakes are well thought out.  And, those mistakes lead to discovery of reality, as in this instance.

Injectors:  When I built my engine several years ago, I did all the calculations, fairly close to what Doug suggests.  I came up with a need for injectors at 6.1 gps, flowed at 58 psi which I figured was the right thing to do since that was HD fuel pressure.  I really did not know, but it seemed correct to flow them at that pressure.  No HD mechanic in this area knew HD FI from Shinola. 

I contacted Marren and told him what I wanted.  He told me the flow rate would be too high.  I suspected he was factorin' when he should have been usin' gazinta since the flow at 43psi would be lower than that at 58psi.  So, I told him thanks but do it anyway.  He told me he did:  I got flow sheets and injectors flowed at 58 psi with a yield of 6.1gps.   Since these injectors are "electrically controlled" I suspected you just changed the voltage or some such thing and the flow/output changed.  ......... the basis of my misunderstanding started here...... .

Today, I looked for my flow sheets.  I called Marren, too.  He sent injectors to me that are 5.29 at 43psi.  Upon this foundation of "error" I built my knowledge base:  injectors could be custom flowed.  I am not an engineer or a professional mechanic or tuner; just an afficianado with a bit of curiosity and scars on my hands, having left my flesh on engines from Briggs and Stratton up to blown alcohol engines, reminding me of why I do what I now do for a living even though my dreams at 8 years of age were to be a motorcycle mechanic.

I am pleased on several levels, one is Doug telling me that flowing injectors is largely a mechanical process and the other is that Marren did send what he knew to be the correct injectors to me since 6.1 gps flowed at 58 is about 5.3gps at 43psi even though he did not explain to me that he could not do what I asked him to do (0513HD).  (The flow sheets are a bit of curiosity, but I can live with them).  I am also pleased to learn a bit more about injectors even though all this learning is at some personal expense.  I guess "how you recover" is where it is at.

[uglyDougly]

   This has been a very civil discussion and interesting too. Remarkable.

   Thanks to everyone who offered info and questions.

   Ed, do you really want to talk about throttle size? Really?

    Doug

[ederdelyi]

Doug,
Well, I don't have a problem picking appropriate carb or TB sizes for a given application, but a lot of other folks sure seem to. Since the title was TB/inj I thought the next step would be TB size and it's effect on engine power/driveability ... it's up to the rest of those out there who may be lurking and hopefully learning.

I can easily let this thread go at this point with no problem :>)

[Scramjet]

What about the knock down, drag out TB thread that was just finished recently in the Twin Cam section?

The moderators just got done cleaning up the floors from that discussion.

I would hope this thread does not go there.

B

[ederdelyi]

Musta missed that one ... or ignored it. Like I said, I can easily forget I even mentioned it, I know how to size carbs and TB's. If the thread is really done maybe someone should ask that the thread be locked ... it's not my thread or my decision.

[uglyDougly]

  Cooler heads prevail.
  Let's call this a wrap?

  Doug

[ederdelyi]

 

[axtell]

chickens??

[uglyDougly]

  instigator!!