Charge Dilution and PV

[UltraNutZ]

This is directly from one of their engineers at DynoJet.  Haven't seen this posted anywhere (I've been looking for 3+ days) so figured I would share.

This is in response to my questions about EGR/CDE changes to their tech support people.



In regards to the CDE (or EGR effect), there's no doubt that depending on the combination of parts, like exhaust, but more so cam shaft design has an effect on the "air and fuel charge" in the engine.. The air mass and fuel mass that should be occupying a certain percent of the engine volume is actually being displaced by EGR to some extent, and the ECM needs to know about this "charge dilution". Adjusting the CDE is tedious and time consuming, but it seems to help with transient fueling and leads to better response in those areas it affects.....which is below 60 Kpa.



We don't have any new tools or information on the "Charge Dilution Effect" / EGR effect at this time.  I hope to have some of the logic and math involved explained to me (from our engineers) in the very near future (See below).  With a better understanding of the underlying strategy, I believe we'll be able to use this calibration item more effectively to level out / smooth the VE surface below 60kpa.



Like I said, it's tedious and time consuming.  If you adjust the CDE, then you need to go and re-tune the VE values below 60kpa.  If you just tune the VE in the first place, and then manually fill-in / blend various areas, I think that's OK.....although a calibration engineer may disagree.  This gets the job done and taking the time to adjust the CDE *may* lead to some perceptible change in rider feel (ie. potentially a touch more torque), but it's not a difference that's easily identified (without a dyno and various instrumentation)..



Engineering notes:

Values in the CDE functions:

0 = 0%

256 = approx 2%



Anyway, very roughly, if you were at 50KPA and the table was set to 2%, then it would assume (60-50)*2%=20% of the charge was from EGR.   



So, I'm not an engineer or an expert, but here's my take on all of this.  Assume you tuned a bike with an aftermarket cam that had a fair bit of overlap, and the thus the potential to "dilute" your intake charge with EGR at low loads, for instance less than 60 KPA. OK, so you tune the bike using stock values that were derived from an OEM calibration engineer for the stock cam, and the you notice, "wow, my VE surface below 60 KPA looks a little choppy".  You want to "knock down" or "fill in" some of the high and low spots, so you increase or decrease the values in the CDE tables accordingly.



Picture, this......the throttle is partially closed, vacuum is relative high and KPA / MAP load is relatively low (below 60 KPA).  EGR present in the combustion chamber results in a richer AFR without the ECM injecting more fuel.  How?...well, the EGR is displacing oxygen and thus with the same amount of fuel delivered by the ECM, the resultant AFR is richer.  You could also look at this "if EGR is present in some appreciable amount, then the ECM needs to make adjustments, because at this time the engine's volume or size is "smaller".  To qualify "smaller" you must look at the equation to determine the VE of an internal combustion engine, and after all the math you end up with an "injection time requirement to achieve a desired AFR".  Again, if the cylinder has some amount of EGR in it, then it will run richer with all other things the same, so the calculation I just mentioned results in error.  We need a way to adjust this, and that's what CDE does.  A Harley doesn't have an EGR valve to control and if it did, the ECM would know it's position / relative flow and make adjustments to the calibration.  Changing the amount of EGR that gets into the cylinders by way of a cam change (regardless if you have an EGR valve), we can use the CDE tables as sort of an "EGR position / relative flow" in regards to how the ECM compensates for this condition.

[Karl H.]

If CDE/EGR leads to a richer mixture, why the hell don't the O2 sensors recognize and take care of that? Why is a correction table needed?

Why is the desription of CDE in WinPV different from what I read here?

Lots of questions...

Karl

[rageglide]

What Karl said.

Closed loop would adapt to meet the target AFR. 

My guess is that CDE is more effective when running Open loop because there's no feedback loop to adapt out the richness.

The "EGR" comments don't make sense because EGR is a totally different beast which comes into play above idle, reducing combustion temps and NOx.

[HD/Wrench]

As well  factor such as IVO IVC will effect this .. Look for the VE table to have some what of a flat area from 50-80 KPA if that is showing up then you are on the right track.. Use of the cam cruncher program will help with what you are dealing with as well. 

[1FSTRK]

If CDE/EGR leads to a richer mixture, why the hell don't the O2 sensors recognize and take care of that? Why is a correction table needed?

Why is the desription of CDE in WinPV different from what I read here?

Lots of questions...

Karl

The O2s detect oxygen level, they do not detect EGR or fuel.

[joe_lyons]

 the charge dilution effect or exhaust gas recirculation is just another calculation in the calibration . The o2 sensor will read whatever it reads but to help calculate the volumetric efficiency it will look at this table to help with its calculations.  All of the calibration are a little different along with the build itself but roughly a 10 percent change in the cde table will equate to a 10 percent change in the ve table but not always

[Frédéric CM]

is there any news about the CDE tuning ?

[joe_lyons]

"When adjusting the EGR table/s it will vary from bike to bike, build to build. As a general rule of thumb if you want to reduce the VE values in the lower RPM range (~0 - 2000) you would double the amount you want to drop in the EGR table. So if you wanted to drop the VE by 10% you would drop the EGR table 20%. In the mid RPM range (~2000 - 4000) it changes to triple, 10% VE needs 30% EGR change. In higher RPM areas it takes even more, 10% VE needs 40% EGR change."

I use this now and it works ok.

[Frédéric CM]

can't we use the CDE to "adjust" the close throttle MAP reading ?

[ben31]

It's an other way to tune the CDE as any CDE value change impact VE but also closed MAP value.

I'm also wondering which of
these methods is the more efficient.

But the point is: how can I find the good target values for closed throttle MAP ?

Envoyé de mon HTC One en utilisant Tapatalk

[joe_lyons]

Idle map should be somewhere in the 30-low 40 range

[ben31]

Yes but what about other rpm

Envoyé de mon HTC One en utilisant Tapatalk

[joe_lyons]

can't we use the CDE to "adjust" the close throttle MAP reading ?

There are other settings to help with the map reading at idle.  Let dynojet know what cams you have and they can make the changes.  It's just like the cam tune tables in TTS but called map tooth read in PV.

[HD/Wrench]

cam choice will effect that as well t/b plenum volume. my 124 with the 640 and 66 t/b will idle at 42 on avg at 550 feet

[joe_lyons]

Another setting that I set every single time that I tune a power vision is the map load bias table. This is essentially calibrating your map sensor to show and match what your ambient pressure is. The way to set this is to figure out exactly what your ambient pressure is for the time and day you go to make a recording, then go record a wide open throttle pull from 1500 RPM up to 6,000, then go alter the table to match what the reading should be.  (Changes are made in .01 Increments). Example - at 3000 rpm I recorded a map reading of 100kpa but I know my pressure at that time was 98 kpa so I go to the table and lower the value at 3000rpm by .02 to achieve a reading next time of 98 kpa.

[Frédéric CM]

IVC IVO is good, map load normalization is tuned (oscilliating from 0.95(@4000) to 1.05 (@6500)). I'm just trying to fine tune my bike and looking for a way to tune CDE.
Btw, tuning MAP load affect VE in what proportion ?

[joe_lyons]

IVC IVO is good, map load normalization is tuned (oscilliating from 0.95(@4000) to 1.05 (@6500)). I'm just trying to fine tune my bike and looking for a way to tune CDE.
Btw, tuning MAP load affect VE in what proportion ?

What are you asking on that last sentence?

[Frédéric CM]

sorry my English is not so good...

When you change the MAP load from 1.00 to 0.98, how il it affect the VE ?

I'm trying to tune the CDE to see how it affect my MAP reading at idle (42kpa), wich a little high isnt it ?
Or maybe it is caused by an incorrect IVC/IVO settings (30/8) for the 57H ?

Thanks

[joe_lyons]

What is your map load value at 1000 rpm?  42 is ok also but 35ish sounds more like it. 

You try to keep the map load reading of 1 at idle. 

IVO and IVC will not affect WOT.  Changing from a value of 1 to .98  should lower the WOT map value by 2 kpa (100->98).

Lower your IVC number and see what your idle map does. 

[Sunny Jim]

So Joe, chiming here, I read my map load normalisation which I understand to be similar to bias global. At 1000 rpm my ratio is 1.02 through to 2000 rpm. I have been trying to correct a rough idle issue on my 120r/ 660sm etc. I have auto tuned it several times with adaptive switched off and I have attempted to set the target afr higher and higher but I still get a richened fuel table at idle. I attempted to drop some points out of my warm up enrichment but I still see this anomaly with the rough idle.  My map is 35- 40 Kpa at idle( 1016 rpm. ) any thoughts?

[Frédéric CM]

What is your map load value at 1000 rpm?  42 is ok also but 35ish sounds more like it. 

You try to keep the map load reading of 1 at idle. 

IVO and IVC will not affect WOT.  Changing from a value of 1 to .98  should lower the WOT map value by 2 kpa (100->98).

Lower your IVC number and see what your idle map does.

This is my current Map Load table, wich achieve a nearly straight MAP at WOT accross the rpms range (corrected for barometric/elevation). I think i'm right here...
1000   1,00
1500   1,00
2000   1,00
2500   1,00
3000   0,98
3500   0,96
4000   0,95
4500   0,96
5000   0,97
5500   0,98
6000   1,02
6500   1,05
7000   1,00
7500   1,00
8000   1,00
8500   1,00
9000   1,00

Do you think the IVC number is incorrect for this cam ? If the IVC/IVO are good for this cam and work for everyone but me, then the problem may be elsewhere, like an intake leak ?

[hdmanillac]

 

TTS VTune 3 offers a CDE calculation algorithm for a while now . Why Dynojet is still not able to offer the same with it's PV ?

[HD/Wrench]

TTS VTune 3 offers a CDE calculation algorithm for a while now . Why Dynojet is still not able to offer the same with it's PV ?

The Vtune 3 does a fantastic job on EGR and timing as well .

[Gordon61]

Sorry to chime in but I've struggled with this for two years now!

I asked Dynojet again the other week about CDE tuning, because I think second to getting your IVO set correctly, it is a significant part of getting idle up to 2000 rpm (i.e. running around town) to run smooth rather than stuttering, surging, and jumping around like a lot of people get after putting cams in and running the so called auto tune bit of whatever little box they have.

Anyway, I got the very same answer as Ultra got two years ago! so I still don't think DJ know

Remember that PV users do not have IVO/IVC settings available in the WinPV software so we have to ask DJ or FM to set them for us but getting that right improves slow running hugely!! or it did for me anyway.

The Next thing I found was that CDE made a difference as well ...but, and to second what Frederic was asking ...we know WHAT it does ...but where is the how much to do it and where and to what end??  Either nobody knows (except Steve at TTS) or nobody is telling 

Regarding MAP - the MAP reading on a Power Vision is a calculation ...NOT a reading off the sensor (try logging MAP Value vs MAP Sensor Voltage  ) ...and... CDE tables are part of that calculation.

MAP at idle 40 - Increase CDE tables 0-2000 by 30% or so and (mine anyway) MAP at idle drops to 30  ...hopefully this is just a PV foible and the ECU is reading the voltage off the sensor directly but then again ...why? and what difference does it make? and what should it read?

With hindsight, I do wish I'd bought a TTS but I already binned an FP3 for the PV and I can't afford to buy a third!! and according to the blurb, they are all supposed to be diy tuners

(rant over  )

[joe_lyons]

CDE helps with valleys and peaks.  Also with abrupt percentage changes in VE from one cell to another vertically.

What did your VE numbers do when you lowered the CDE 30%?  I don't use it just to change MAP reading.