2004 C5Z P59 Throttle Follower oddities

[LS6TrackAddict]

I've been working on cleaning up my "return to idle" from a free rev of the engine at a stop. I've got a bit of a RPM dip on the return to idle and I've been trying to attack the problem without much success.

Oddities/Questions:

• I've been unable to get a "delay" in the throttle follower. Setting the delay (to 1 sec, for example) in either "P/N" or "Gear" does not delay the decay of the TF airflow. Is this known/common on P59 C5 operating system? Is there something I'm missing?
  
  
• This one is a little less an "oddity" perhaps.. Doing some math to derive the decay rate I'm seeing in the logs, it appears the ECU is using the "Gear" tables (for both Delay and Decay?) despite the car being stationary and in Neutral. The calculated decay rate isn't a 100% match to the decay rate in the table, but I attribute this to the limited sampling rate of the logger as we are in the ballpark. Do these ECUs ignore the "P/N" Decay/Delay?

Attached is the Calibration:
read_01232024rev1.2.hpt

[ns158sl]

You are on the right track. Need to see a log to help diagnose.

[LS6TrackAddict]

You are on the right track. Need to see a log to help diagnose.

Here you go sir.

[edcmat-l1]

List all the vehicle mods otherwise no one knows what the tune file should even look like.

[edcmat-l1]

First off you can't run a GEN3 in "MAF only" mode. That doesn't work.

Second, it looks like by the VE table it has some amount of cam in it. If it does, the VE needs to be spot on and it will most likely run much better in speed density full time. That's just the way it is with these cars.

I'd setup the spark tables differently. Less idle timing and more over/under control.

Injector data has been changed. Everything but the transient. That's going to cause you some problems.

You get the fueling squared away, injector control, VE, and you should lessen the idle dip considerably without touching the TC and TF.

[edcmat-l1]

You are on the right track. Need to see a log to help diagnose.

Not really.

[Alvin]

I've been working on cleaning up my "return to idle" from a free rev of the engine at a stop. I've got a bit of a RPM dip on the return to idle and I've been trying to attack the problem without much success.

I would not be looking where you are looking to fix this. In fact I'd return them to stock.

This issue is normally caused by the engine returning to idle and going though a rich section of the VE table. VE tuning is critical on this if it has a cam.

You are patching this, not fixing it.. Its just going to compound problems later.

[aaronc7]

I second or third what's already been said. I had my 2003 C5 (now running a 2004 P59 PCM) tuned way back in the day and now that I've taken it on myself, I started from scratch and many of the tables that were touched or edited never really needed tweaked much, if at all. Getting good base fueling (VE/MAF) is key before tinkering with all of the other fueling modifiers. I have a mild cam (226/230), but still found VE only to run quite a bit smoother and more consistent. With a MAF was OK too, but I'm just picky I guess.

[ns158sl]

yeah no really, did not see that coming, lol. I just try to get people to post a tune and a log.

[SiriusC1024]

• This one is a little less an "oddity" perhaps.. Doing some math to derive the decay rate I'm seeing in the logs, it appears the ECU is using the "Gear" tables (for both Delay and Decay?) despite the car being stationary and in Neutral. The calculated decay rate isn't a 100% match to the decay rate in the table, but I attribute this to the limited sampling rate of the logger as we are in the ballpark. Do these ECUs ignore the "P/N" Decay/Delay?

It's a manual transmission.

[SiriusC1024]

DeatschWerks injectors?

[LS6TrackAddict]

Hey guys appreciate the response and input here. This is my first LS that I'm tackling so it's a bit of a learning curve. I'll try to clarify a few of the questions here.

I am at 4000-4200ft ASL for what that may be worth..

Here's what's done motor wise to the car at this point:

SLP Blackwing Filter w/ OEM MAF/Air Bridge
OEM 90mm LS2 TB unported
Mamo Ported FAST92 Intake
TFS 215cc CNC Heads
Cometic .040 Headgasket
OE LS6 Shortblock
Cam Motion Titan 3 Cam (224/228 113+3 .603/.595)
YellaTerra TFS 1.7 Roller Rockers
Kooks 1 3/4" LT w/ Catted X-Pipe and OE Ti Exhaust
Fuel Injector Clinic 365cc (40lb @ 58psi) Injectors
ATI 10% UD Damper
Mantic Twin Clutch

Again, I appreciate the responses here and willingness to provide some feedback/constructive criticism. So please don't be shy. I can handle it

@edcmat-l1 can you clarify a little bit on what you meant by "you can't run a Gen 3 in MAF Only mode"? As stated, this is my first LS, but I was under the impression you could effectively force the ECU to run MAF only as it is configured in the tune file attached in the original post. Can you expand a little and clarify what I'm missing or did I not implement the required changes appropriately to isolate the MAF?

I do not intend to run the car in MAF only mode in a end state. I do intend to likely run the vehicle with Dynamic Aiflow enabled as I figured that would provide the best overall driveability once MAF and VE were dialed. I can state that the MAF curve in the calibration file posted in the OP is pretty close within reason. However, I did a little further fine-tuning this AM (which I'll discuss further in a moment) to refine it further. I am pretty confident that the new tune file attached to this post has the MAF transfer function pretty well dialed (unless the VE table is still somehow in play if I understand your post correctly).

You also mentioned the VE table. I have spent a bit of time driving/logging and tweaking the VE table specifically. I wouldn't call it perfect yet, as I've only been doing street tuning. And it's a little hard to get a decent number of cell hits in some of the low RPM/high load and decel stuff (with DFCO turned off). But I have made a pretty decent attempt at getting it reasonably close. I feel it's within 5-8% most anywhere, given my wideband data and the driving I've done in OL. One area I believe could use some help is the 400 and 800 RPM columns. I have a little less confidence in those areas, but the car drives well and meets fueling targets within a few % under just about any driving condition.

I mistakenly did initially (previous to this tune) have 28deg idle timing to help get the idle undercontrol after the mods listed above were installed. Did them all at once (mistake..) so there's a bit of a learning curve to figuring this out. Anyway.. I could tell the car would benefit from less ignition timing at idle leaving more torque reserve to the adaptive (over/under) idle to control it. Pulled 5deg from there and that's where I've been the last bit. Works well, but I'll certainly take your consideration for even less into account and leaving more in reserve for the adaptive. What do you think would be an appropriate target for a combination such as mine? 20deg base?

Injectors as mentioned are Fuel Injector Clinic 365cc. I used their online injector data and did not see any change to any transient data listed in their data. Did I misinterpret or miss something?

@Alvin The area af the VE table where this occurs is, as mentioned above an area I admit probably isn't tip-top. I do have a installed wideband (not logged in the previous log) but I'll spend a little more time there and see what I can do.

I appreciate the guidance. I'm certainly all ears for anything you and others with more experience can share.

@SiriusC1024 I would have potentially thought with the trans not being in gear it might use those look-up tables but it appears I'm mistaken.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

Before I was able to log in to the forum and see the replies above I spent a little time in the garage this AM with a few fine tweaks to the MAF transfer function, some Idle Airflow tweaks, and then did some testing with the ETC Scalar value. I found an older post that had some data on the return to idle situation and thought I'd give it a go. I was able to virtually eliminate the Desired Idle Airflow - MAF/Dynamic Airflow discrepancy and that seemed to improve the idle dip a fair bit. It's not OEM perfect, but it's a noticeable improvement.

Again! Thanks everyone for your input!! I enjoy learning and sharing so thanks to you all for making that possible.

If one of you more experienced tuners would like to work with me on addressing the idle stuff here I'd be happy to compensate justly for your time. Please PM me if you'd like to work with me on dialing this in.01242024etcscalar240.hpl

[edcmat-l1]

I can be contacted via the email in my sig.

That's too much stuff to try and answer right now but the GEN3s don't run in "MAF only" like you can get away with in the GEN4s.

In manual trans cars the TC and TF don't really work.

It will run better in speed density.

You mentioned Mantic clutch. Is it a lightweight flywheel and/or clutch?

[LS6TrackAddict]

I can be contacted via the email in my sig.

That's too much stuff to try and answer right now but the GEN3s don't run in "MAF only" like you can get away with in the GEN4s.

In manual trans cars the TC and TF don't really work.

It will run better in speed density.

You mentioned Mantic clutch. Is it a lightweight flywheel and/or clutch?

It's a Mantic Twindisk clutch w/ their lightweight (16lb) flywheel. https://manticclutchusa.com/products...rvette-organic

[edcmat-l1]

Lightweight flywheels and clutches are a tuning nightmare in C5s.

[LS6TrackAddict]

Interesting. As the car sits - it has really good street manners/behavior. Car drives, cruises, handles stop-n-go traffic no stalling, no bucking even when cruising in 6th at near 1K RPM. I'm just nit-picking the slight dip on return to idle which isn't that bad when I dialed in the ETC scalar to minimize the Desired Idle Airflow - MAF/Dynamic Airflow error.

[edcmat-l1]

That's great. Congrats. They can be a real PITA to get to return to idle correctly with lightweight flywheels.

[gametech]

That's great. Congrats. They can be a real PITA to get to return to idle correctly with lightweight flywheels.

You really have to nail down the spark correction for those. The airflow corrections are like swinging a hammer at a mosquito.

[edcmat-l1]

You really have to nail down the spark correction for those. The airflow corrections are like swinging a hammer at a mosquito.

The rolling idle tables are the holy grail for these.

[Alvin]

You really have to nail down the spark correction for those. The airflow corrections are like swinging a hammer at a mosquito.

well said