FAST with two step rev limiter

[TURBO 6]

My car is somewhat bogging in the 60'. I went a 1.55 last time out but it seem to bog after I let off the t-brake. The only reason it went a 1.55 is because the track hooked real good. It looked like the car wanted to carry the wheels but it only jerked them off the ground.

Now the question I have is my acual A/F ratio is in the high 9's when the car did this. I noticed on a couple of data logs before I was using the two step that this didn't happen. It would launch and run close to the 'target' a/f ratio throughout the 60' and beyond. So what do you have to do to the VE table to get it to work with the two step? I already have the 02 sensor turned off until after I let off the t-brake. Target A/F ratio is in the 11.5 range which I know it can go leaner. Thanks for any suggestions.

 

[Reggie West]

How do you have the WB being switched on or off by the trans brake?

 

[TURBO 6]

It's not, the 02 sensor is enabled after the 3700 rpm rev limit in the two step. It'll probably clean up when I leave with more boost. I haven't tried to launch with more boost yet. Next time I gonna leave on 25#'s of boost. That should stop the bogging.

 

[Reggie West]

I dont think boost or lack of it is the problem.

With that cam you have, I would suggest leaving off the trans brake at 4500 rpms or better. This way you are leaving at peak torque and you dont drop much in rpms .

Just my 2cents

 

[Taffy]

What rpm is the 2 step at and what rpm does the O2 come on at?

Sounds like the richness caused by the 2 step is causing your 60 ft to bog. This is fixable though.

 

[TURBO 6]

Taffy, That's what I am thinking. 2 step comes on @3700 for now.

I am going to try more rpm's to see what happens before I start taking fuel out. What rpm and boost should i be launching with? The cam is a 214/210 atr roller with 1.65 rockers, if that matters.

 

[S2V6RACER]

I was about 4100 rpm with my stock block motor and that had a 218/212 roller with 1.55 rockers. It sounds like your VE's are too high in your 2 step range and as you get back into 02 correction. I would try dropping some ##'s in those cells on your 2 step rpm and come out a little leaner.

 

[TURBO 6]

That's the plan, after I try leaving on more boost without the two step. I want to see if in fact the two step is causing the bog. Then I'll know exactly what to do.

Wanna see a data log?

 

[Chuck Leeper]

2 step??

I think U will find that as the t/brake comes off, and the engine flashes the converter, the O2 correction will over shoot the target, and cause the A/F to go fat for a few frames....

Have you tried to leave it in closed loop, and then go to the correction limits and zero them for the rows that are in effect when on the brake?? BE SURE that the engine is HAPPY w/ the A/F map in that area before you do this.. IE: run the car without the 2 step on, and see what correction U R getting, correct to as close to zero as is possible, then do the above.....

Are you using the A/F and the timing to spool the turbo??

 

[TURBO 6]

Chuck,
I may be going to the track Wed. (weather permitting) and the first thing I'm gonna do is try to leave without the two step. If the car leaves good then I'm gonna set the two step at the rpm I left on the previous pass. Then I'll know for sure if the VE Table needs some adjustments.

I haven't started to fine tune the spooling. I've been tuning for the fastest mph then I was gonna work on the spooling issues. I'm trying to get max boost with zero correction on the top end then I try to get it to spool faster. Does the rich and retard method work?


I'm also interested to see what gains I get from 3" dp to a 3.5".
I hear 20hp at the wheels. I think I heard Red got that before.