Need help Tuning for boost, timing, + afr with a wideband and afc.

[Grizzly Racing]

Vehicle: 91 GSX
Current mods are: small 20g, 95 pistons, FMIC, 750cc inj., DSMchip, webcams, AFC, and all supporting mods. 93 octane pump gas

I recently installed the wideband to use as a tool to do some fine tuning. I logged a pull in third gear and the wideband read from 11.88 - 12.08.

Should the AFR be consistant from low rpm to high rpm? Or should it be at one number at low rpm and then graduate to another number at high rpm?

Currently my boost is set to 26psi. Base timing is 3* BTDC and my timing on the logger reads 18* at WOT. This results in the 11.88-12.06 AFR reading using a AEM UEGO with 0 knock. AFC is zero'd out.

Before I had the wideband I set the timing to 5* and gots lots of knock, so I backed off the timing until the knock went away. This is how I ended up at 3*.

Now that I have the wideband should I put the timing back at 5* and add fuel to eliminate the knock while aiming for the 11.5 AFR that seems to be recommended?


Thanks for the help.

 

[jrohner]

I would aim for between 11 and 11.5:1 to start with, but if you are getting knockless runs leaner that's great. You say you have 95 pistons. They are 8.5:1 compression so you will be more limited on how much timing you can run. The 1g cars stock have pretty aggressive timing maps, where the 2g's have really conservative timing.

How much boost are you running? That means a lot for timing and afr's.

 

[snowborder714]

Always set your base time and fuel pressure before tuning.

On pump gas, I'd aim for 11:1. Your ratio will be leaner at the beginning of the run and progressively get richer until you hit full boost. Once you do, it should pretty much stay the same until you let off the gas.

Yes, you obviously want to get rid of the knock.

 

[JayRolla]

Sounds good, like they said tune too 11.1afr. You should be around 13.0 afr untill full boost hits then it should be solid. After getting the tune down, add boost till you knock and then back it up a little.

 

[Grizzly Racing]

I would aim for between 11 and 11.5:1 to start with, but if you are getting knockless runs leaner that's great. You say you have 95 pistons. They are 8.5:1 compression so you will be more limited on how much timing you can run. The 1g cars stock have pretty aggressive timing maps, where the 2g's have really conservative timing.

How much boost are you running? That means a lot for timing and afr's.

Boost is currently set to 26psi. I had it at 28-psi and was getting about 4 counts of knock so I backed it off to 26 psi and the knock went away. This was done before I got this wideband hooked up. Now that I have the wideband I think I am going to put the boost back up to 28 psi and add some fuel with the AFC.

The DSMchip is programmed for a 2g timing map and set for 43psi of fuel pressure.

Timing is reaching 18* at WOT. Do you think I should leave the base timing alone and work on 28psi and 11.5:1 AFR?

Based off the few replys I got it seems like I should have it a little lean down low and as the turbo reaches full boost I should be at that 11.5:1 ratio and hold that until redline.

 

[snowborder714]

Set base timing to 5* and shoot for an 11:1 A/F ratio. I feel 11.5:1 should only be for those running E85 or higher octane gas. That's a little too lean for me for running pump gas (although my tune does have a few spikes around 11.3 or 11.4, but I try to get rid of those).

 

[JayRolla]

Why you keep saying he should move base timing back to 5*. All that will do is cause him to have 20* or more at wot and I think his 18* is perfect.

I would tune to 11.1 on pump gas at the leanest. 10.9 afr is where I would stay on pump. Then add some more boost till you knock and I would say thats a good tune.

 

[snowborder714]

Doh! Forgot he can't control timing.

 

[JayRolla]

Doh! Forgot he can't control timing.

No problem, Im just used to the old school way of controlling timing with the CAS. SAFC all the way, . Im just a poor bastard.