Post-Tune Engine Stutter at Peak Torque

[kefi]

im sure that is the injector duty cycle and not fuel pump

Shit, is it? Could you explain how you know? The injectors are the one area I'm really lacking on knowledge.

nvm i get it now

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[KTuner]

That's not fuel pump duty. If you're dropping pressure you have a problem or a custom tune where the tuner went too far without looking at that data for reference.

 

[AnotherFK8]

That's not fuel pump duty. If you're dropping pressure you have a problem or a custom tune where the tuner went too far without looking at that data for reference.

Is there any way to see the fuel pump duty cycle %? Or is the pressure reading sufficient data?

 

[boosted180sx]

Shit, is it? Could you explain how you know? The injectors are the one area I'm really lacking on knowledge.

i don't have any experience with ktuner but im pretty sure it is.
the value is about what you would see on injector duty cycle

The car can also see a slight pressure drop without you really hearing/feeling anything by increasing injector duration to compensate till a certain point.

 

[kefi]

Oh shit, I'm dumb. That's the INJECTOR duty cycle being charted. Sorry fam. When you guys were saying 'thats the injector duty' I thought you meant the injectors themselves were the problem.

Sorry for the ping, J. Thanks for being active in our community!

 

[AnotherFK8]

i don't have any experience with ktuner but im pretty sure it is.
the value is about what you would see on injector duty cycle

The car can also see a slight pressure drop without you really hearing/feeling anything by increasing injector duration to compensate till a certain point.

It is. Just worked it out against RPM and ignition pulse width, matches the "duty cycle". My bad!

 

[kefi]

Come to think of it, fuel pump duty cycle is something only Hondata has, unless something changed. Nonetheless, fuel pressure dropping like that is indicative of a problem.

 

[AnotherFK8]

Come to think of it, fuel pump duty cycle is something only Hondata has, unless something changed. Nonetheless, fuel pressure dropping like that is indicative of a problem.

Definitely looks that way. I'll reflash back to stock and see if the pressure is doing the same thing. Cheers again ?

 

[AnotherFK8]

Honda have just checked their internal recall system, no FP recalls on my car. Will be going back to the tuner ASAP.

 

[AnotherFK8]

Updating this thread as I go along for the benefit of the minor few that might run into the same problem as me.

Flashing back to stock brought about no stutter or click, though the datalog seems to suggest something different. At around 4280RPM I'm seeing a slight drop off of fuel pressure again (Honda have checked their internal system for F.P recalls, mine doesn't show as being one of them).

 

[bbp]

Hey guys,

Today I had my CTR tuned by a reputable U.K Honda tuner using Ktuner V1.2. End results were 386BHP and 353LBFT. During the post-tune street runs, the tuner noticed an audible/physical blip occurring at around 4200RPM, coinciding roughly with the peak torque point. Audibly it sounds like a click/hi-hat, almost like a small release of air. Physically it feels like a tiny stutter whilst going up the rev range. A week prior to the tune I had no choice but to fuel with 95 RON (91 RON US), the tuning team put it down to possibly having bad fuel not agreeing with the 98RON based tune. 95RON is the minimum suggested quality for the U.K.

Things Tried:
- Tune has been rechecked for inconsistencies. None found, tune is conservative and said to be safe.
- Flashing back to stock and retesting. No clicking or stuttering noted.
- Tank emptied as best as possible. Brimmed with 99RON, driven casually, then spirited, for 80+ miles in an attempt to flush remaining 95RON.
- Ktuner datalog shows a slight blip in AFR at suspect RPM (unbeknownst to me you have to actually save the log once you're done recording...doh...I will try again tomorrow and upload results along with dyno sheet). Regardless, AFR is always under 12, even during the blip.

Mods:
- HKS Legamax Exhaust.
- PRL HVI Intake (stock turbo inlet pipe).
- HKS Intercooler w/charge pipes.
- KTuner V1.2

Any help would be massively appreciated as always!

It's probably your VTEC crossover. Check your VTEC settings.

 

[Jpierro79]

Hey guys,

Today I had my CTR tuned by a reputable U.K Honda tuner using Ktuner V1.2. End results were 386BHP and 353LBFT. During the post-tune street runs, the tuner noticed an audible/physical blip occurring at around 4200RPM, coinciding roughly with the peak torque point. Audibly it sounds like a click/hi-hat, almost like a small release of air. Physically it feels like a tiny stutter whilst going up the rev range. A week prior to the tune I had no choice but to fuel with 95 RON (91 RON US), the tuning team put it down to possibly having bad fuel not agreeing with the 98RON based tune. 95RON is the minimum suggested quality for the U.K.

Things Tried:
- Tune has been rechecked for inconsistencies. None found, tune is conservative and said to be safe.
- Flashing back to stock and retesting. No clicking or stuttering noted.
- Tank emptied as best as possible. Brimmed with 99RON, driven casually, then spirited, for 80+ miles in an attempt to flush remaining 95RON.
- Ktuner datalog shows a slight blip in AFR at suspect RPM (unbeknownst to me you have to actually save the log once you're done recording...doh...I will try again tomorrow and upload results along with dyno sheet). Regardless, AFR is always under 12, even during the blip.

Mods:
- HKS Legamax Exhaust.
- PRL HVI Intake (stock turbo inlet pipe).
- HKS Intercooler w/charge pipes.
- KTuner V1.2

Any help would be massively appreciated as always!

You might be running out of fuel pressure. This will cause this also check for throttle closures. That’s close to the rpm I got them and had to change my boost curve cause the stock turbo is torque spiky at 4K. The throttle closure can happen from excessive air charge or loss pressure to save the engjne. Running 11.8 down low only allows about 24-25 psi max. You can’t run more than 210 percent aircharge at 11.8 on stock fuel system at 4000 rpm. Especially full bolt on cars.
Check pressure first than check aircharge tablle vs actual aircharge

 

[Jpierro79]

Jesus that post I made on tables and reductions is confusing.. to clarify:

There's three tables that limit boost:
1. Boost limit based on atmospheric pressure
2. Boost limit based on IAT2 temperature
3. IAT2 compensation for the atmospheric pressure table (the first table)

It will use whichever of the first two is lower at any point in time. Ideally, you aren't hitting the limits inside of the IAT2 table. If you aren't and are thus are using the limits from the atmospheric pressure table, the compensation from the third table kicks in, lowering the limits of the first table.

Note the large increase (in most spots) in limit on the PA table vs the IAT2 table:

These tables are largely responsible for the massive change in power from season to season. The boost limit keeps going up all the way down to 32F.

This is all unrelated to OP, though. OP probably is hitting fuel pump limit like Hondata said.

These charts will limit boost but using hondata ots these are not even close to stoping boost pressure. They are in total bar the lowest is 25 psi which is 2.73 and that’s at 90 degrees Celsius at 7000 rpm which that turbo can’t even put it out. The limiting tables are aircharge and iat reduction.
they say “boost control” not these charts. Only the factory tune uses these to limit it.

 

[AnotherFK8]

Just to update.

- Took the car back to the tuner to have the tune rechecked. Started afresh, couldn't find anything wrong with the tune. No fix.
- Swapped the ECU for another and retuned. No fix.
- Swapped wastegate actuator. No fix.
- Moved the VTEC to 3.8K, click and judder move also.
- The car is currently on a service plan and hasn't had an oil change in a while. Tuner suggested that the viscosity of the oil has gone and the click/judder is related to the VTEC pin firing across, not being cushioned by the oil??
- Had oil changed by Honda and had exhaust cam clearances checked per tuners request also. No issues.

The car is still juddering, though not as much as previous. Any further ideas?

 

[RnS6515]

I know this thread is a bit old but did you find out your problem?

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