weird KR issues I cant figure out

[LETZRIDE]

car: 1996 3.8L camaro with a 97pcm, fully built heads/cam

Heres the issue, I've been running off just the VE tables for a year or so now with little/no issues. My KR has been under control maybe getting 0.5* under part throttle every so often...nothing major, and probably something unavoidable.

Now, I want to go back to a MAF based tune. I followed the Russ K guide and retuned my MAF and put a stock VE table back in. My fueling on the wideband looks great...right in at the low 14's at part throttle, and I haven't done WOT yet.

My problem is, I have HUGE amounts of KR with my maf tune even though my fueling and spark is the same as my VE based tune...even if I pull timing I get KR all over the place as high as 7* or more...I subtract timing and it's still going wild, I put the stock spark table in and still no help.

Why am I showing KR only when tuning off the MAF when fueling is ok? but I am not showing it with the VE based tune?...and FYI the VE tune still does show KR when I get it, as I have gotten 2*'s before when I bumped the spark a little higher in some categories.

Heres a copy of the MAF/MAP tune and a scan from each.

aug29kr is a scan with the MAF

aug30backtosd is a scan back with VE tune

SDbeforereversion2 is the VE tune

and the backtomaf is the MAF tune.

Thanks guys.


Attachment 30494

Attachment 30495

Attachment 30496

Attachment 30497

[Dr. Nopps]

I had that too. Check this out. Especially the tunes.
http://www.hptuners.com/forum/showthread.php?t=36003

[LETZRIDE]

I read through that, but my wideband is not reading too rich...its reading the same values as my VE tune, and on the same Spark table as my VE tune...so essentially everything should be the same no?

You would think 14.2-14.6 afr and 25* of timing in one tune that doesnt show kr, wouldnt show KR in another tune under the same fueling and spark conditions?

Are the KR sensors automatically desensitized if you fail the MAF?

[Dr. Nopps]

What spark table is being used on the VE tune? The high & low octane tables are based off of g/cyl which is calculated with the MAF sensor. How then could you have the same timing profile for both tunes? Sorry if this doesn't make sense. I also noticed you zero'd out your IAT Spark table. Aren't you afraid of not having a little protection there? TCS Max Torque table looks a little low in spots too.

[LETZRIDE]

I have the MAF set to fail, but it is still plugged in, so it actually still gets a reading. I can see on my tables as well as through my scan gauge that I am getting the same kinda timing in both cases.

In any event I also tried putting the stock timing table in when I tuned with the MAF and was still getting KR...and I took off up to 8*s over time in the effected cells with no change.

I'm not too worried about the IAT spark table, I want the car only to command what I say, not be jumping around...when it jumps around and adds timing on me is when I run into issues. Plus I have a scan gauge that alerts me when I do get KR

[Dr. Nopps]

O.K. Took a look at the aug29. MAF scan. I don't normally try to diag. or fix peoples cars online so you can consider yourself unlucky/lucky. Looks like your MAF readings are jumping WAY too high WAY too fast. Even with your mods, you shot to 8lbs/min instantly and were all over the place. Here's a copy of a scan. Look at the MAF readings to see what I mean. I don't know what could cause that on your car. Could be a bad sensor, I don't know if an air leak can do that.
Attachment 30530
Attachment 30531

[LETZRIDE]

I appreciate any help/suggestions

The cam is Huge (not the one listed in my sig) the current one sits in at about 230/240 duration .512/.512 lift and a 113LSA...heads are fully P&P'd with 1.9" manley valves and 1.57 exhaust valves. Compression is about 9:9:1

For what it's worth the MAP readings jump drastically as well, actually it is one of the main reasons I am thinking of going back to a MAF based tune, is because part throttle literally throws me to the far right side of the MAP cells. 25-30% throttle fuels off the same as WOT, so I end up getting 10AFR under part throttle at times which is frustrating because of my gas mileage loss.

I am wondering though...by failing the MAF does that desensitize the KR sensors? Maybe I'm just reading false KR with the MAF that is not being picked up when running my VE only tune if the sensors are dampened?

[LETZRIDE]

oh I also have 3200 stall converter in there, which probably contributes to air numbers bouncing around?

[Dr. Nopps]

To eliminate that as a variable (stall converter) while scanning, include a brief period of leaving it in neutral with light throttle application and mabey hold it at 12% or 15% TPS for a few moments. The MAF reading shouldn't jump around much but unfortunately in your case, probably will.

[LETZRIDE]

To eliminate that as a variable (stall converter) while scanning, include a brief period of leaving it in neutral with light throttle application and mabey hold it at 12% or 15% TPS for a few moments. The MAF reading shouldn't jump around much but unfortunately in your case, probably will.

I'll get that scan for you monday

[GeoJB]

I'm stock but it might answer your questions.
http://www.hptuners.com/forum/showthread.php?t=35950

Didn't look at your scan/tune. Is there any delay-space-between the KR, MAF settings and the PE settings Vs the throttle?
In other words have the MAF try to adjust for KR Just before the PE mode kicks in.

[tramotorsports]

Why did you put the VE table back to stock after you enabled the MAF? Why not keep the same VE table as SD? or recalibrate it correctly after you go back to MAF?

[LETZRIDE]

Sorry, hopefully I'll have the scan by tommorrow.

I put it back to stock because everyone who tunes the MAF has a stock VE table...not just that but I need to cheat to get the VE table to work...i.e many of my WOT cells are 200% and maxed out....so I think that might skew things...so I just left it stock.

[matt5112]

I was also under the impression these motors tend to run a little better with a proper VE tune as well as MAF tune.