a little backfire issue

[12sec.5.3]

I'd like some of you guys to take a look at this file and see if you can help me figure out why I'm getting this extremely lean condition immediately when I hit 100% TPS. It clears shortly after but the backfiring into the intake is embarrassing and is getting to me. I've tried to richen up VE in the cells where it looks like the prob is according to the log but I could be way off.

[Taz]

Hello 12sec.5.3,

Post your tune when you get a chance ... the log is of more use when accompanied by the current tune.


Regards,
Taz

[12sec.5.3]

here's another

[12sec.5.3]

Pay no attention to the date

[WeathermanShawn]

So you are just hitting the throttle while the vehicle is stationary?

One of your Scans you never got up to operating temperature, so it stayed in cold-open loop. Does this ever occur when the vehicle is at normal operating temperature and moving, or only when your blipping the throttle at Idle?

A few more questions/points..

1. What is your actual engine size.
2. Are your injectors stock.
3. Your PE Mode Enable (TPS) B3616 is extremely high at 90%. That may be the main problem.
4. Looks like you have modified a lot of the Enrichment Tables. Is that when the problem started?

What else do we need to know to figure this out?

Your basic Tune is closed-Loop MAF-Enabled, with a lot of various tables modified from stock. If you had serial wideband I could see your AFR's, but I can't see your actual AFR on my logs..

We need more information..

[12sec.5.3]

370 ci, 42 lbs inj. L92 heads bunch of other crap. One of the logs was while it was cold and the other was warm. Should have been enough to put it in closed loop. They were all just idle but it does the same while driving on the street. I didnt change the PE enable to 90% TPS so maybe that could be contributing. The spark and most of the VE is done by Futral but I've been messing with 400-1600rpm from 65-105kpa cells to try and correct this issue. I've tried stock 6.0 VE's too but it's the same thing. The auto VE tuning was not working as planned for me so I've put that aside for a while. Its pretty stout besides that. Put down 422 rwhp with 31 lb injectors. Thanks in advance fellas.

[WeathermanShawn]

I would triple-check the Injector Flow tables for precise accuracy. Some of your Injector Flow Rates look quite low in your log, but its tough to tell unless you push it more on the RPM' and VSS.

Just for F.Y.I., its your MAF Airflow that will control the majority of your air fuel calculations, so concentrating on the VE may not get you anywhere. If you don't believe me, just add 10% to your MAF Calibration Table and see how your fueling increase ~10%.

If you can get a log at normal operating conditions and push it to 6000 Rpms, that might help. When you are just at Idle (Low VSS) your MAF will not push much air through it.

A good log with the right Pids would help. Trims, Airflow Pids, AFR (not voltage) will help. Check your Injector specs and add Airflow through the MAF..lower that darm PE Enable, that is way too high (IMO).

Looks like you have a nice set-up. Hopefully we can help.

[12sec.5.3]

Inj. flow rate is set at 41.9773. Changed my PE enrichment to 50% 0-2800 rpm, 40% 3200-4000 rpm, 30% 4400-7200rpm. I looked at a file from the new camaro and it was set at 30% through the whole rpm range which I find kinda low. I'm debating on increasing my MAF by 5-10% and try and work with it from there instead of going through the whole long process... What u think?

[WeathermanShawn]

It is always best to do a complete log that will show what your LTFT's are doing before a MAF adjustment. If your MAF Table has never been adjusted, then +5-10% is not unreasonable.

A good log, with PIDS not exceeding 24 channels with some Airflow Pids, AFR/EQ, LTFT's will help. A nice 30-45 minute run from Idle, cruise, and some WOT will tell the story.

I would be curious to see that lean spike. I could not see it on the log..any way you can post up a screen-shot? Either that or just re-do a log..:)..

[12sec.5.3]

I'll see about a screen shot bro. I've never attempted that before but yea the MAF settings are stock. I tried to monitor MAF and look in the tune while recording because it usually shows wt cells your pulling from but it's not doing it for some reason. I'll add 10% and see wt happens.

[swingtan]

+1 on the wide band O2 data. It might be a few things, but I'd like to see what the fueling does on an extended throttle opening (if safe to do so). It may be dynamics, PE ramp in rate or a few other things.

The MAF trace shows a significant dip when you got WOT, this may be a cause or a symptom though, as a backfire will slow the air speed past the MAF.

Simon.

[12sec.5.3]

Wells thanks for all the input. I added 10% to my MAF and with the other changes (PE @ TPS%). I think that did it! There's no hesitation or backfiring whatsoever... It evens feels a lil more spunky ;)

[12sec.5.3]

I'd prob be better off dialing in the MAF but if I can work around that I will

[12sec.5.3]

I don't know how to do a screen shot but if someone can explain I'd like to try.

[WeathermanShawn]

I usually use 'Microsoft Paint' to do attachments. But, I read through your log pretty good on this one.

Overall your Trims look real good. Like Simon stated perhaps your PE Ramp in was an issue when you were using 90% TPS opening. How was your WOT fueling? (my Scan Tool can't convert analog..).

One thing I noticed is that you have almost maxed out your MAF. 460 g/s! Wow, you must be pushing some HP. Maybe a bigger MAF..you're topping out.

As long as your PE Mode/WOT AFR looks good, and your current issue is solved..then good job! Your Tune looks a lot better.

Good luck.

[12sec.5.3]

Thanks man that's a relief to hear! WOT AFR is around 11.6-11.9 it jumps around a bit right now. I may try and get it closer to 12.3-12.6 if that's not too lean but it's pretty powerful now as it is. Might have to lean it out a bit during the warm weather.

[12sec.5.3]

I was curious so I went look it over and seen the highest MAF reading was 476 g/s. Wt do these stock MAF sensors top out at?

[WeathermanShawn]

I believe it is 511 g/s.

If you log MAF Frequency you can't get over 12,000 Hz. You'll hit that Frequency on a very cold day, with high pressure, near sea-level, and a lot of HP.

You are getting close..:grin:.