tuning help - low speed bucking

[timmilot]

Hello All,

I'm hoping to get some help with my current setup. I originally had the car dyno tuned and have taken to see if I can get it to idle around any better.

Specs: 85mm Delphi maf, L92 intake, ls3 heads, 228@50 cam, LT's, NGK O2's on front O2, AEM wideband.

My understanding is AFR error % can go in as a multiplier to the VE table. I did a couple iterations of this without any real effect, and notice the STFT is 0%.

thanks for looking

Tim

[timmilot]

I'm stumped as to why it's staying in open loop, or at least no STFT values since there are readouts of the two O2's. The rear cat seems to show up in the DTC's when I open them in scanner.

Also, there is a P1637 immature, “Generator L-terminal circuit”, which will reappear on occasion. Is this reason to change the alternator yet?

[mowton]

Your Bank 1 O2 sensor is flat lined at 4XX mv. Any other DTC's than what you stated above? Is this a transplant engine, if so what setup and have you checked all the sensor wiring?. Double check the MAF setup (may want to try and re-enable the P0101, 102 and 103 DTC's to Mil on 1 error and re-enable the SES to see if you have a MAF fail. Not related, what injectors do you have?

To tune VE you need to fail the MAF and I usually set the High RPM disable to 8000.

Ed M

[timmilot]

Ed, thanks for the input.

I have LS3 injectors. It's running throttle by cable on an '02 Camaro computer.
It is a transplant, it's in a '95 RX7.
Front to back it's an 85 MM delphi MAF (5 wire truck maf), LS3 block and injectors, 24 tooth reluctor, I think LS2 cam sensor.
I'm not seeing high RPM disable in my options. The MAF fail high frequency is set at 13,500 Hz.

[timmilot]

Your Bank 1 O2 sensor is flat lined at 4XX mv. Any other DTC's than what you stated above? Is this a transplant engine, if so what setup and have you checked all the sensor wiring?. Double check the MAF setup (may want to try and re-enable the P0101, 102 and 103 DTC's to Mil on 1 error and re-enable the SES to see if you have a MAF fail. Not related, what injectors do you have?

To tune VE you need to fail the MAF and I usually set the High RPM disable to 8000.

Ed M

Ed, thanks again, this got me at least looking at the right area and found there wasn't continuity on the O2S low signal wire. Now I've got working NB O2's, STFT's going, etc., now on to getting some data and experience.

cheers
Tim

[xrelapse13]

Is your wideband accurate in this log? If so, it's pretty lean, which could cause surge as well. First thing is to get your fueling dialed in. Do this in open loop with the wideband. Once that is done run the Idle config to get your RAF correct and play around with the timing. Should be able to get a rock solid idle with that cam and perfect driveability.

link to Idle config thread: http://www.hptuners.com/forum/showth...e-(w-pictures)

[timmilot]

Thanks!

I'm finding I'll need a correction - the WB is about 2 ratio points high, i.e. indicating 16 at 14, etc. At least the WB gage seems to be at 14.7 when the NB's are at 0.5v approx. I did run the gauge ground to the HPtuners box, so I think now I'll have to adjust the offset accordingly.

[xrelapse13]

hmm, that's odd. I have an aem as well and at most its off by like .2-.4 which i just adjust in the set up. What is your AEM set up as in HPTuners?

[timmilot]

idle_1-26-14-5pm.hplidle_1-26-14-5pm.hpl

I'm adding the last log. I've got it in as the AEM wideband. I need to double check the gauge ground wire going to computer, I'd expect if they don't share a ground very directly, i.e. just through the ground from PCM there could be a potential difference, but not 100% where the difference is coming from. The only reason I'm inclined to believe the gauge is that it seems to be corroborated by the NB's but will have to check more.

[benno25]

I reckon the following are some ways to stop low speed bucking. Others, feel free to chime in and correct me. This is especially true for larger cams though.
Firstly. Delay your end of injection timing until your wideband stops getting richer. Maybe even go back a little from this point.
2nd. Get your car on a dyno to determine where MBT is.
3rd. Try commanding different AFRs and timing at places where the bucking occurs. Find the timing/afr that it occurs the least. Also, smoothing or flattening your VE and timing tables in these areas can help.
4th. If the car is still bucking and map is going all over the place. Try flattening the VE in this area and using the VE multiplier based on TPS to smooth things out a litte. This way the fuelling will stay consistant even though MAP is going all over the place.
5th, and the best solution in my opinion. Buy an ITB intake manifold and be done with it!! lol.

Cheers
Benno

[jamesmic]

I'm puzzled with reference to why its staying in open circle. The back feline appears to appear in the DTC's the point at which I open them in scanner.

[timmilot]

r9-3-2-02-2014 530pm.hplthanks for looking. the later log was after I got the O2's working. I'm posting the latest log from a recent tune.

I'm richening the VE and smoothing it next.

[timmilot]

Tim Milot.JPGr10_fxMaf.hptHi Benno
Thanks for your input, I'm somewhat new at this so I'm going to ask for a couple clarifications.
1.) When you say delay the end of injection timing until the wideband stops getting richer, what am I setting?
2.) I attached a dyno plot from when I got it tuned, and it runs mostly reasonably except around 1600-1800 RPM steady state.
3.) How do you command different AFR where bucking occurs? I seem to have a single commanded AFR, do you mean adjusting VE table?
4.) I have been looking at and smoothing the VE table, and plan to richen overall somewhat.
5.) Will throw ITB on it if all else fails I suppose that'd go with a full service tune somewhere ...
cheers

Tim

[xrelapse13]

Give this a try and let me know if it's better.

[timmilot]

Give this a try and let me know if it's better.

Thanks so much for posting!

I haven't had a chance to test yet but will update.

cheers
TIm