Part throttle knock...help

[Gibby]

So, At idle and at WOT my trims are at a sweet 0.0

I have no KR when I have the pedal past 40% or in PE mode, even at WOT.

However when my engine gets nice and warmed up and I have the throttle at about 10-20% I am getting some nice KR readings anywhere from 0-3* This number is more apparent and also sometimes worse when going up hill.. My Trims are also reading lean under the same conditions... anywehre from 0 to + 8. I have reduced some timing.. I have lowered fan temps thinking maybe I was just getting too hot. I have done several Maf tunes... Please help... any advice is note worthy...

Edit: No vacuum leaks.. not to my knowledge anyways, I have sprayed starter fluid allover the engine and no signs of them...

[umrjmac]

vehicle info? log? tune?

help us help you

[Gibby]

Sorry bout that... 2002 grand prix GTP 75,000 mls..

Headers, 3.4, 1.84 RR, ported TB, AL 104's, CAI..

Car is not entering boost when KR is present.. I currently dont have a log file.. believe it or not whenever I am ready to go scanning it doesnt have this issue... lol I never seem to be ready to catch it..

[passingpower]

What does your PE enable HOT TPS vs RPM table look like? Also, next to that, there's an AFR / TPS modifier table… the proper name of which escapes me (as I wait for my baby daughter to go back to sleep while reading posts on my iPhone.) is that table still stock?

BTW, Congrats on your new assignment at GTPworld.net!

Ok, now that I'm awake and looking at VCMedit, sounds like your trims are mostly under control and you could benefit from some PE tweaking to cover the not quite boost region. What the L36 guys think of as "Power Enrichment". Not so much adding a heap of fuel, more like keeping it from starting so lean on tip in. First some questions.

How are you scanning KR/Boost? Aeroforce?
What values do you find in your PE Enable Delay vs TPS table?
What values do you find in your PE Enable TPS Hot table? @2k? @2.8k? @4k?
What values do you find in your PE Base AFR vs. ECT table @176˚-194˚?
Describe your PE Fuel Adder vs. RPM vs. Time table. Modified? smoothed? or is it ugly-stock? Any positive #s on that table?
What values do you find in your PE Fuel Adder vs. TPS table?
That last one is where I eliminated my flash knock. Stock keeps fueling too lean, too far up the throttle slope for good launch control.
How often do you see +8 LTFT? (For the time being let's assume that's just outlying data points, unless it's frequent.)

[Gibby]

Thanks!

Ok here it goes...

I am scanning with an aeroforce, I have my KR and LTFT's scanning when I drive, whenever the ltft's run lean from +3 to +10 I am seeing some KR, from 0 to 4

PE Enable Delay vs TPS table: Is zeroed out...

PE Enable TPS Hot: 40 acrossed the board

PE Base AFR vs. ECT: starting from -40 to 140 it goes as such.. 10, 11.2, 11.3, ", from 0-100 it is 11.4, and then 11.3 from there on out..

PE Fuel Adder vs. RPM vs. Time: This table is a zzp table that I have modified over my time of learning to tune, its only lean(positive) from 9.6,1600 and inwards..

PE Fuel Adder vs. TPS: Zeroed out..

I will go out and see if I can get a scan of this today... Thanks for the help so far!

[passingpower]

AFR adder is zero. Good, eliminated that as a cause. Try this:
make a cust PID using the same hist as the trims. (I'm pretty sure) Be sure it's RPM vs kPa. Use the TPS sensor as the input. Log your driving. See the throttle % under the 90 kPa column? Enter those values for their RPM in your Enable TPS Hot table.

Now, at all RPMs when you hit 90 kPa pressure, PE will become active instead of letting you ping until you reach 40%. Remember in those write-ups you read that told you to set this table to an arbitrary value for tuning and that you could fine tune it later? Well, now is later.

I'll let you know up front, setting mine like this made a big improvement but, at the same time, it knackered my city fuel economy. I modified those settings later to a little less agressiveness and got some mileage back.

If you're tuning a DD and care about the cost of gas, all the PE settings are a balancing act. You need to take them far enough to protect and then back them off to keep from wasting cash at the pump. LMK how it goes.

[Gibby]

Ok I will try that tonight or tomorrow, just so we are on the same page her is my current bin

[passingpower]

I'll check that out too. Tonight or tomorrow.

[99ssei]

AFR adder is zero. Good, eliminated that as a cause.

How is this a cause?

[passingpower]

Under stock conditions, This table will add to the PE commanded AFR so that the result is fairly close to stoich and will then richen as the throttle increases. This is most helpful on tip-in, before the time/RPM/AFR table can catch up. As we drop pully size, Not only does the total manifold pressure increase, it also ramps up sooner. We force higher cylider volumes at lower throttle positions which can give us a lean spike if the AFR adder table isn't adjusted to let the end AFR low enough to allow appropriate enrichment. Setting this table to all zero, at least for tuning, keeps it from interfereing with fueling calculations.

[99ssei]

I'm curious about this because I just installed a P&P Gen V w/ N*TB & LQ4 Maf and seeing PT KR but 0 KR beyond 3300 or so. My PE enable triggers around 28% TPS. If target AFR is 11.6, the table in question adds 2 to the 11.6 (13.6:1) up to 35% and then slopes down to 0 at 65%.

IMO...It's a really key table because that's what primarily defines the transition AFR between stoich and your target PE AFR, after all you can't go from 14.7 to 11.6 in an instant. Is there any data to verify either way?

[passingpower]

By your explanation, you know exactly what's goin' on.
Here's how I fixed my tip-in knock: In addition to the rest of post #6, I kept the AFR adder table stock under 15%. from 15-25 I sloped it down to zero so that it stops leaning the mix just as the PE is enabled under slight acceleration. By the time I reach moderate accel, the AFR has settled nicely. This scheme gives solid GO! while keeping my city economy from dropping through the floor.

For your second question, about the only thing I've read on this is a post by Eddie98. That got me thinking along these lines.

[99ssei]

I guess it all depends on when your PE enable table is set. For me, sloping the PE add vs. TPS @ 25% wouldn't make sense if PE isn't enabled until 28%.
Perhaps I should scale back the timing to coincide with the PE enable table...
In my example, start the sloping at 30% instead of waiting until 40 (stock)

[passingpower]

You're right. All these settings depend on each engines individual boost. Things like pully size, blower generation, porting, position of the boost bypass and SC settings in the PCM will ensure no two are alike. Happy tuning!