Looking over several NA .lt1 files, it seems like every one of them is subtracting fuel in the PEvsRPM table. I am just curios if its a rule of thumb to subtract fuel in the PE mode.

Is there any kind of general rule about O2 values corresponding with the A:F ratio? Ex: 900-999 = 12:1-13:1. Is there any way to get a (no matter how unprecise) measure of the A:F without strapping down on a dyno and plugging in a wideband?

Ryan

 

Interesting you should post such a question. Dan K and I are currently discussing this exact issue based upon a theory I have. With his permission I will post what we discussed.

What I did worked for me, but not all of the haze is lifted from this subject as far as I am concerned.

In a basic way to answer your qestions:

1. No

2. No. However there is VERY inexact way to determine if you are leaner or richer in one area compared to another using our O2's...but then again, lean or rich compared to what? So in essence until you wideband, forget it.

Hopefully this brings out someone who knows something different from me.

Ben

 

Hey Ben,

This is a little more technical than the "how do I change my MAF table" questions I had for you a while back .

The reason I ask is that so far my car is seeming to like more fuel (butt-meter). My timing was around 35-56* (in the table), but I was getting knock retard. Each time I have increased fuel, (PE table) the knock retard has decreased. All of this makes sense to me - the car was lean -> causing detonation. Adding fuels means richer a:f, cooler comb chamber -> reduced detonation. WOT O2 values are in the 910s, currently seeing about 6-8* of retard with 35-36* timing (in the table).

I have tried using a PE table for a similar setup as mine (one that decreased fuel), but I had very little luck with it (lots of knock retard). I started decreasing the timing to combat the KR and the car just felt weaker than I thought it should. This is why I'm going the other direction - more timing, more fuel (instead of less timing, less fuel). So far it seems to be working.

This is what prompted the question - Anyone get on a dyno and have to add fuel in the PE table?

Just curious, what did you do?

Ryan

 

Ah, I remember that MAF question.


in about the simplest of terms (which I now know was wrong to not explain it completely), I posted what I did there. However, let me get Dan K to sign off on us posting our discussion and it will make it crystal clear what you should be looking for and you can see if it works for you.

However, there is no subsitute for wideband testing.

As a comparison, I am at 31-33 deg advance in my car at the upper MAP/RPM range. For me, that is all it needed. I understand as a car becomes more efficient, it needs less timing (please others confirm this statement). This would make sense in my case.

What are your mods?

Ben

 

Doh, Dain Bramage! I looked at your website for your mods.

 

No drain bamage!

Basically all boltons (LTs, electric H2O)
235/242 .568/.592 cam
Stock heads

I haven't been able to really get on the right track with tuning just yet. I have been able to lose quite a bit of low rpm surge, and it idles perfect up to this point. Right now I would like to dial in the WOT a little bit more before I hit the dyno. IOW, I can't afford to spend 5 hours on the dyno making guesses.

Anxious to hear what Dan K has to say.

Ryan

 

Ryan would you like to look at my file, (OBDII) it was tuned on the dyno and my car made peak power at 13.4 or so if Im not mistaken...

 

I posted Dan K and my discussion. Check it out.

 

Why? I don't know anything.

First off, I don't have any pe vs rpm's that subtract fuel.
As far as O2's...if you really think you want to try and use them go ahead. I've added fuel to a car before and watched O2 voltage drop and the wideband verified that the actual fueling increased. I'm sure it has something to do with EGT and combustion chamber temp, but I have no proof of that.
In addition to that, a friend of mine bought a base tune from one of the popular LT1 mail order guys and it was so lean as rpm increased that O2 voltage would drop sharply. Way lean. On a wideband afr was around 15:1. Another friend had a base tune from the same place that had the maf tables changed from about 150 g/s and up. His car was between 14.5 and 14.7:1 on the wideband. For these 2 reasons, I really don't like the idea of a mail order base tune....but that's for another post.
I think what Ben is doing by verifying that cell 15 blms are around 128 takes out one of the variables in pe afr tuning. He is definitely on the right track.

If I were trying to do your car on the street, I would set your 90-100 map timing to where you get 38* of timing, as seen on a datalogger. Not what is in your tables.
Then I would keep adding fuel until knock goes away. I see no reason why you shouldn't be able to safely run that much timing. It really is a hit or miss way to do it, but should work fairly well.
But you may end up using less timing than that.

Just remember, that the richer you are the smoother that car should feel and the faster you might think it is. But that's not actually the case.

There really is no way do tune wot without a wideband and either dyno or track (to verify mph). Unless we can find a way to verify that Ben's way does work and is safe to use. : )

 

In this thread? I must be missing something...

PDM: Send that file to me if you don't mind. I'd appreciate it!

Edit...found it. I'm an idiot .

Ryan

 

I had been running a total of 38* timing at WOT (only specified 35 in the tables, have a mysterious 3* added somewhere), and had no knock at all.

PLUS, my PE/WOT fuel tables were signicantly leaned out.

So, I think this goes to show that if you need to ADD fuel to the STOCK tables, with less timing than I have, something might be wrong... but of course since your engine isn't stock, this all changes.

 

Right now I am running 15% in the coolant table across the normal range (160*-230*F), and about +5% from 3k-7k. This is with 35* in the timing table.

WOT O2 values are around 910, and I have no knock retard. However, the plugs were bright white! I'm am going to add fuel until the plugs are brown.

I started look at the plugs after each tune last week. IMO, it is much safer than using a logger to dial in WOT - Keep in mind both are valuable sources of info. The plugs don't lie and are very easy to read. Just don't burn your hands!

Ryan

 

I pretty much agree with what Dan said, except for one thing I didn't quite understand. He said "I would set your 90-100 map timing to where you get 38* of timing, as seen on a datalogger. Not what is in your tables." AFAIK, the datalogger is getting the timing it reports from the PCM. So what you see at WOT should be what is in the PCM, plus the 2-3 degrees of "mystery timing".

Rich Krause

 

Exactly. In order to hit 38* you should have 36* up to 4500rpm. At 4500 and 5000 you should have 35*. Then at 5500rpm and up you will have 34*.

 

what mystery timing are you all talking about?