Tuning questions w/cam/header mods..

[Redline Motorsports]

Just finished a cam/header install on a 00' C5 MN6. I started with the idle and got it working great. We pulled the motor on the dyno with the stock timing table and had zero knock retard. The A/F was a bit rich but damn near matched the values in table {B3618} PE Modifier based on rpm. Can I assume that the IFR (which was stock) and the VE table values are pretty close? After seeing that they where close, I leaned down the PE table and got the AF where I wanted it. My main question is back to the stock timing table. If the motor didn't mind the stock timing table, should I call it quits?? The timing ended up around 28 degrees at full advance for most the WOT range. The car made 388 RWHP and 370 RWFT which I felt was pretty good with the stock heads, cats and stock LS1 intake.

What do you guys think? As a newbie I finally felt like I got a grip on this tune as it only took me 4 flashes for the idle and 3 for the WOT! LOL!! :lol:

Howard

[foff667]

its hard to tell if a ve is spot on doing the work on a dyno & I would more or less go on the #'s you see in the real world on the street...so to say the ifr & ve are on just because on the dyno your pe is close to matching doesnt mean too much in my eyes imo.

[Redline Motorsports]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

[Dirk Diggler]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

[Redline Motorsports]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

I thought that is what I was saying. :roll:

I like use the AFR value vs. the EQ ratio as it is easier for me to compare to the WB on the dyno. My point was that the commanded AFR was with .1 of the actual WB reading! How can that not represent an commanded vs. actual perfect condition??

[Blacky]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

Yes, the commanded value in the PE table(s) should match what you see on your WO2.

The narrow band O2's are not used to determine AFR at WOT. The commanded fuel in PE mode may be *way* off and the PCM would never know since it cannot and does not monitor any AFR's in PE mode. That's why you need a wide band.

The PE table(s) command the PCM to calculate the appropriate injector pulse width for the measured air mass in the cylinder. If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR.

There is one exception, if the long term fuel trims are positive when PE mode is activated, then the PCM (assuming that the engine is running lean due to +ve trims) will add extra fuel to the WOT commanded PE values. that's why people shoot for LTFT that are slightly negative - that will prevent the PCM from "compensating" for a lean condition.

Regards
Paul

[Dirk Diggler]

PE is a multiplier that represents a Commanded AFR. If you set your pe for 1.13 or 12.96 (samething) thru tuning your WB needs to read those values at WOT

I thought that is what I was saying. :roll:

I like use the AFR value vs. the EQ ratio as it is easier for me to compare to the WB on the dyno. My point was that the commanded AFR was with .1 of the actual WB reading! How can that not represent an commanded vs. actual perfect condition??

You're asking a question and you arent satisfied with my answer. When i read your post it seemed to me you were kinda confused about the functions of the pe table, so i answered the best way i felt fit. Sorry if it wasnt to your liking or redundant :roll: oh and i wouldnt be worried about .1

[jfpilla]

I thought I remember reading somewhere on this forum that the values in the PE modified (commanded AF) should match the actual WB readings. Isn't that parameter based upon a ratio off of 14.7 which the NB reads to determine WOT AFR?? EQ ratio of 1.00= 14.7 AFR if the tuning is close to be accurate?

Yes, the commanded value in the PE table(s) should match what you see on your WO2.

The narrow band O2's are not used to determine AFR at WOT. The commanded fuel in PE mode may be *way* off and the PCM would never know since it cannot and does not monitor any AFR's in PE mode. That's why you need a wide band.

The PE table(s) command the PCM to calculate the appropriate injector pulse width for the measured air mass in the cylinder. If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR.

There is one exception, if the long term fuel trims are positive when PE mode is activated, then the PCM (assuming that the engine is running lean due to +ve trims) will add extra fuel to the WOT commanded PE values. that's why people shoot for LTFT that are slightly negative - that will prevent the PCM from "compensating" for a lean condition.

Regards
Paul

Paul,
"If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR."

Did you leave out part of your point?
I think it should be pointed out that IFRs must be calculated properly. If the trims are set using IFRs then the commanded AFR will not match actual. Even after a well done tune the AFR will change based on weather.
So, how can .1 be measured and worried about. Also, I can't get my WB to measure that smoothly that I can tell .1.
It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

[GMPX]

It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

^^ You beat me to it.

Cheers,
Ross

[Blacky]

Paul,
"If the underlying values that the PCM uses to determine the air mass in the cylinder (i.e. VE, MAF, IAT ect), or the injector pulse width (i.e. IFR) then the actual WOT AFR will not match the commanded AFR."

Did you leave out part of your point?

No, I don't think so. I was just trying to say that the PE commanded AFR is based on calculations only (no feedback). So if the inputs that the calculations are based on (VE, MAF, IAT, IFR etc) are wrong then the final calculation will be wrong and always wrong. There is no trimming or learning based on any measured feedback.

I think it should be pointed out that IFRs must be calculated properly. If the trims are set using IFRs then the commanded AFR will not match actual. Even after a well done tune the AFR will change based on weather.
So, how can .1 be measured and worried about. Also, I can't get my WB to measure that smoothly that I can tell .1.
It would be nice if posters would say whether they are running with or without an MAF, when asking about tuning questions. :P
Joe

I agree with that 100%.

Paul