Timing and/or Fuel adjustments per gear

[Black LS1 T/A]

The other thread about being leaner in lower gears is odd, to me, as my AFR is RICHER in lower gears, and leans out in the higher gears per RPM. This seems to be a natural occurrence of more fuel needed at that speed + the RPMs.

So, on a related question (I don't want to hi-jack his thread), if anyone can tell me how I could increase fuel specifically for each gear, I'd appreciate it.

Also, come to think of it, is there a way to change timing depending on the gear? I can handle more timing in the lower gears than the upper gears.

Also, I'd like LESS timing in 1st gear for a given RPM (to gain more street traction), yet full timing in 2nd (best pull), and a bit less timing in 3rd (more susceptible to KR). Though, I think what I REALLY need in 3rd gear is more fuel.

Is any of this possible?

Thanks!

[J 98ta]

It is REALLY sounding like it's IAT related now. IE: With a blower, your IAT's are climbing, and mine are dropping. We have opposite porblems. Hmmm. I know the MAF will use IAT, but I am in SD.(maybe you are too) :?

I wonder if it has anything to do with the B4901 Charge temp blending ? I never knew what this table does.

Sorry, I do not know how you could vary timing based on gear. Probably needs custom OS ?

'J

[caver]

The other thread about being leaner in lower gears is odd, to me, as my AFR is RICHER in lower gears, and leans out in the higher gears per RPM. This seems to be a natural occurrence of more fuel needed at that speed + the RPMs.

Maybe you have a fuel delivery problem? measure your fuel pressure, in a turbo application the turbo doe'snt spool up as well in the lower gears and so the pump has a easier time supplying fuel.

Dont know if you have a turbo but it's a thought.

[Black LS1 T/A]

The other thread about being leaner in lower gears is odd, to me, as my AFR is RICHER in lower gears, and leans out in the higher gears per RPM. This seems to be a natural occurrence of more fuel needed at that speed + the RPMs.

Maybe you have a fuel delivery problem? measure your fuel pressure, in a turbo application the turbo doe'snt spool up as well in the lower gears and so the pump has a easier time supplying fuel.

Dont know if you have a turbo but it's a thought.

Thanks!

Check my sig...

[caver]

Check my sig...

Promise to read all the way to the bottom in future :lol:

Centrifugal blower?

Seen similar things with Vortech blowers if the fuel pump is marginal.

[Black LS1 T/A]

At 6500 RPMs my IDC is about 80% to 85%. Even though I have two pumps and a boost referenced regulator, I still have some restrictive sections in my fuel route and I only have the Siemans 55# injectors.

That 422 at 12 PSI is thirsty! :twisted:

[kp]

I have 57lb siemans and I am at 95% DC at a solid 58psi so you have some room to go My car actually gets richer at high rpm in high gear, I have to pull timing up top to stop detonation fom the increased IAT, not from being lean. It happens to work out well though..

Is your a/f diving on a wideband or stock O2s?

[Black LS1 T/A]

...
Is your a/f diving on a wideband or stock O2s?

On the dyno.

At about 6300 RPMs, I can't keep it from rising unless I increase my base regulator pressure. With a 1:1 increase (lb fuel per lb boost), I was trying to keep it from rising too high at 12 to 13 PSI boost.

I hold it at 11.4:1 or so until about 6000 RPMs, and it begins to rise. By 6300 it is above 12.1:1

Also, the 422's torque curve hits hard and immediate, then only goes down-hill. Admittedly, downhill from 700+ RWTQ is a lot, but it doesn't seem to be particularly helpful without slicks. :(

This isn't my best 549hp/757tq dyno run, but the graph is easier to see, and I can't find the other one to re-scan it better. My belt was slipping and I was only making 9 to 10 PSI peak, here:



Heck, I'll put this other one up. I was about 11 PSI on this one. But, it's hard to read:

[Black LS1 T/A]

A better cam choice might turn this aspect of my situation around for me...

[kp]

throw some fuel at it via the PE, your pump wont keep up above 60psi most likely. Since your dynos are with the converter unlocked your RPM is way off so its hard to tell exactly where you need to change it. If you have your dyno files or you can get them send them to me and I'll put them in the new dynojet software that will show the proper RPM and torque, dynojet finally fixed their software about a year ago.

I have the same injectors you do and at 12:1 a/f they are at 97% @ 61psi at 600rwhp through my drivetrain - thats all they are good for unless you can run the fuel pressure higher but thats hard on that pump and I wouldnt trust it.

Belt slip? Havent heard that for a while, the SDCE thing fixed that absolutely 100% Its the only reason I have a LS1 F-body procharger still