Anyone want to have a TB/inj. discussion?

[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