2015 JEEP GRAND CHEROKEE 6.4L V8 WHIPPLE Acceleration problem - 05036071AF

[AUTOTECH]

Hello Everyone.

I've been struggling with this problem for few month already, Johan and MAS (still waiting from AJ) also tried to figure out this problem but no success.
I had a 2014 PCM that was Installed when first tuned the car and I did not had this problem, I had to replace the PCM to a 2015 version due to some other issues (non-tune related) and then this problem started.

Upgrades:
WHIPPLE 2.9L SC KIT+ INJECTORS
FUEL INJECTOR SET (EV6 90LB/HR SHORT)
FULL ARH EXHAUST SYSTEM
Fore Innovations L2 Dual Pump Fuel System.
MAHLE Forged Pistons
Molnar Rods
Calico Coated Bearings
Performance Camshaft - 6.4L VVT Apache MAX camshaft
Hellcat Lifters
ARP Head Studs
ARP Main Studs
Forged Pushrods
Head Gaskets
Fresh Timing Set
Fluids/Filter
ATI Super Damper Harmonic Damper\Balancer


The video attached describes the problem, Listen to the sound of acceleration, Wah wah wah wah...

non of the tuners were able the trace the source of the problem, I did my own research and tests and I'm pretty sure that this is a TB related:

I made Throttle specif log It seems to me that this problem is TB related.
It happens only on partial\deep acceleration (not WOT) throttle, between very calm easy daily driving to WOT, in WOT no problems.

I made 4 accelerations in the log:

1. 3rd gear from 30-60kmh fast acceleration - getting the wah wah wah problem and can see that:
Accelerator Position D (SAE) and Throttle Position (SAE) are NOT matching.

2. 3rd gear from 30-60kmh slow moderate acceleration - NO wah wah wah problem and can see that:
Accelerator Position D (SAE) and Throttle Position (SAE) are matching.

3. same as 1.

4 same as 2.

*in WOT - NO PROBLEM.



Please see ATTACHED log files.

[ElecTech]

The fact that your in closed loop under boost is probably not helping the situation. The fueling is lean and surging along with very low timing during that situation is compounding the problem. If you look at the O2 voltage during your wah wah, I think they correlate. You may need to work on your WOT fuel trigger points to get enrichment in sooner and then work on getting some timing in there.

[06300CSRT8]

Looks simply like your bypass is fluttering open and closed, resulting in fluctuating airflows and MAP readings, resulting in wild fueling. Not much you can do here, you are teasing the bypass to a above and below 0inhg signal source and has no choice but to open close. It is very difficult to apply that much throttle and not have it surge like that.

[06300CSRT8]

You can try to install the low vacuum bypass valve from Whipple, which will tend to stay open even in very low vacuum conditions, but will never stay open below 5-6inhg.

[AUTOTECH]

The fact that your in closed loop under boost is probably not helping the situation. The fueling is lean and surging along with very low timing during that situation is compounding the problem. If you look at the O2 voltage during your wah wah, I think they correlate. You may need to work on your WOT fuel trigger points to get enrichment in sooner and then work on getting some timing in there.

Hi Jaime Thank you for your help and response.
Before going farther in understanding what your explanation deeply, You are basically saying that it's not related to the TB?
Why the problem happens only in middle throttle angle low and WOT working fine.

[AUTOTECH]

You can try to install the low vacuum bypass valve from Whipple, which will tend to stay open even in very low vacuum conditions, but will never stay open below 5-6inhg.

Hi and Thank you.
My main concern is that the only thing that was replaced is the PCM, nothing else was changed or touched, coincidence?

[06300CSRT8]

Hi and Thank you.
My main concern is that the only thing that was replaced is the PCM, nothing else was changed or touched, coincidence?

The issue you are seeing can be helped somewhat with a tune, by reducing the pedal input versus throttle body opening keeping you no where near boost eve at say half throttle. The new PCM required a complete retune as it is an entirely different operating system and ECU. There is a chance whatever was done in your old 2014 ECU wasn't carried over to your new tune, or that the new PCM just doesn't have the ability to be tuned in the same manner.

[AUTOTECH]

The issue you are seeing can be helped somewhat with a tune, by reducing the pedal input versus throttle body opening keeping you no where near boost eve at say half throttle. The new PCM required a complete retune as it is an entirely different operating system and ECU. There is a chance whatever was done in your old 2014 ECU wasn't carried over to your new tune, or that the new PCM just doesn't have the ability to be tuned in the same manner.

I also think that and also was told that this issue need to fixed with DS CMR Software.

[Hemituna]

I also think that and also was told that this issue need to fixed with DS CMR Software.

Ummmm.....no, HPt is way, way, way, way, way better than DS on these.
My daily is a whippled 15 SRT Jeep, nearly same spec as OP.
Did it also go wah wah wah when I first tuned it.....yes it did (DS & HPt).
Is it fixable.....yes it is and DS & detuning it is not the answer.
At part throttle you can bump into tq and airflow limits in the torque modelling.
So telling the PCM about the huge airflows you are now using is not smart.
It will limit the TB opening to keep the numbers where it wants them.
If you reduce pedal vs TB it just dulls the thing till you go WOT.
If you increase pedal vs TB, it will surge as it opens, gets shut down, opens again, gets shut down again etc etc....
The whipple likes to be fed lots of air so we need to rein in the airflow numbers to keep the PCM happy.
I forget where now, but in some of the OS's there is an airflow table that won't allow you to go higher than 511 or something.
So I now use that number as a guide to the max and then the ETC functions just as it should, totally tunable.
Cam timing is really important too as OE has it moving all over the place..even more critical if you have an aftermarket cam.
Attached tune is an example of where the numbers end up...and this one has a 92mm Hellcat TB.

[AUTOTECH]

Ummmm.....no, HPt is way, way, way, way, way better than DS on these.
My daily is a whippled 15 SRT Jeep, nearly same spec as OP.
Did it also go wah wah wah when I first tuned it.....yes it did (DS & HPt).
Is it fixable.....yes it is and DS & detuning it is not the answer.
At part throttle you can bump into tq and airflow limits in the torque modelling.
So telling the PCM about the huge airflows you are now using is not smart.
It will limit the TB opening to keep the numbers where it wants them.
If you reduce pedal vs TB it just dulls the thing till you go WOT.
If you increase pedal vs TB, it will surge as it opens, gets shut down, opens again, gets shut down again etc etc....
The whipple likes to be fed lots of air so we need to rein in the airflow numbers to keep the PCM happy.
I forget where now, but in some of the OS's there is an airflow table that won't allow you to go higher than 511 or something.
So I now use that number as a guide to the max and then the ETC functions just as it should, totally tunable.
Cam timing is really important too as OE has it moving all over the place..even more critical if you have an aftermarket cam.
Attached tune is an example of where the numbers end up...and this one has a 92mm Hellcat TB.

Hello Hemituna, Thank you for your support.

glad to here about someone with the same setup, Are you that HPT can cover the needed maps that need to be fixed also in 05036071AF, it is the latest update form FCA.

[Hemituna]

Hello Hemituna, Thank you for your support.

glad to here about someone with the same setup, Are you that HPT can cover the needed maps that need to be fixed also in 05036071AF, it is the latest update form FCA.

Yes, done lots of these on all OS, nothing actually needs a fix, it just needs to be tuned correctly.
Don't worry, for a while there, I too thought all 2015+ PCM's couldn't be made to work!

[06300CSRT8]

Ummmm.....no, HPt is way, way, way, way, way better than DS on these.
My daily is a whippled 15 SRT Jeep, nearly same spec as OP.
Did it also go wah wah wah when I first tuned it.....yes it did (DS & HPt).
Is it fixable.....yes it is and DS & detuning it is not the answer.
At part throttle you can bump into tq and airflow limits in the torque modelling.
So telling the PCM about the huge airflows you are now using is not smart.
It will limit the TB opening to keep the numbers where it wants them.
If you reduce pedal vs TB it just dulls the thing till you go WOT.
If you increase pedal vs TB, it will surge as it opens, gets shut down, opens again, gets shut down again etc etc....
The whipple likes to be fed lots of air so we need to rein in the airflow numbers to keep the PCM happy.
I forget where now, but in some of the OS's there is an airflow table that won't allow you to go higher than 511 or something.
So I now use that number as a guide to the max and then the ETC functions just as it should, totally tunable.
Cam timing is really important too as OE has it moving all over the place..even more critical if you have an aftermarket cam.
Attached tune is an example of where the numbers end up...and this one has a 92mm Hellcat TB.

The 511 g/s is in the Engine Diag>General>Airflow Max RPM, and your attached tune maxes out at 999 in that table. You have 511g/s set at 1792 rpm, perhaps you mean to say at lower rpms to not exceed this value?

[Hemituna]

I found this way back when I was struggling to get the 15+ working right.
511 or 999, it's as though 511 is THE table limit
That one and similiar OS sometimes wont allow a greater value and even if you get it to take one in HPt (some will), it still doesn't seem to change the actual table limit.
Have even tried DS as that will allow any value, (thats how those big numbers got put in there)...but it made no change to the issue at P/T.
BUT, if you keep TB airflow numbers under that 511 threshold, the ETC now will do whatever you want within reason and still not surge.
Which means now you can get plenty of boost and tq at low rpm with just a lil pedal (totally tunable)
Like they should be when blown, not detuned and lazy to avoid surging etc.
It works on all OS that weren't originally blown including pentastar.(hellcat is exception obviously)
They all do it to a certain extent, some worse than others like the 15+ that sometimes surge badly (more so with a whipple), others are just plain lazy.
I may not be totally right, but just saying what I do to work past the issue.

The 511 g/s is in the Engine Diag>General>Airflow Max RPM, and your attached tune maxes out at 999 in that table. You have 511g/s set at 1792 rpm, perhaps you mean to say at lower rpms to not exceed this value?

[Stultzd]

Old post but I'm having this exact problem with my 2020 scat. 3.0 whipple with a 105 tb. Would you be able to tell me what I need to fix to smooth this out?

[LilSick]

you have a log?

and the tune?

[CaliberGuy05]

I have this problem as well but on my dodge caliber 1.8 ecm

[Stultzd]

you have a log?

and the tune?

I'll get one tomorrow

[Stultzd]

How do I upload it?

[LilSick]

click 'go advanced' >>>

and follow the attachment instructions