Tuning Advice: GM MAFT

[jfdid]

Hey guys...

I'm runnin a 16G on the stock IC, 680's, GM MAF(drawthrough), stock exhaust, IC pipes, new motor. Timing: 5 deg.

Anyways, I was at 15PSI, and the car was running very well....only 2 counts of knock in 5th gear WOT.

I upped the boost to 18PSI and it's knocking quite heavily(12 counts) now. I richened the WOT knob one click, and now the car's running much too rich, and suffering from Rich Studder. It seems I need some more adjustment in between...is this where the "fine/RPM tuning" side of the MAFT comes in?

The problem starts at about 1200HZ of airflow...pretty much right at the low cutoff for the WOT knob.

Is this tuneable? Would an exhaust help my cause? IC pipes? I'm planing on the exhaust/intercooler/pipes for the spring, but I don't know if they'll have an effect on this knock?

Is it just simply that I can't run this high boost on this car?
Thanks guys!

 

[jfdid]

Something else I thought of: What about the DIP switch for 3" or 3.5" or whatever...would that affect it?

 

[FASTSPOOLINGST]

no, you can get zero knock counts with just the normal mode. Only go to fine tuning once you get your boost set to where you want it and you are not getting any knock. then you will go fine mode and lean it out until you see knock in 2% increments.

My car was doing the same thing you are talking about. This may sound crazy, but I had to turn the knob to the lean side to get the knock to go away. i think i was getting rich knock. Cuz it was studdering and shit too and bogging down. I went 2 clicks lean on the wot knob and wallah! It ran like a champ and zero knock counts

 

[98spydert]

I don't think you can handle 18lbs on just a upgraded turbo and injectors. I'd either back off the boost until you get a full exhaust and intercooler or try the WOT mode and see if you can get that knock down with 2% or 4% more fuel. Any more than that and performance will most likely take a dive.

 

[jfdid]

Fastspooling: So it was knocking when it was bogging?

Obviously I have a fuel pump as well. Could 18psi be too much for my Walbro 190? I couldn't see that?

Would the exhaust have an impact on knock? How?

 

[FASTSPOOLINGST]

I think i suffered from the notorious rich knock.

your 190 is fine.

Stock SMIC and numerous pulls in a row on 18psi w/ a 16g. Sounds like heat soak to me.
You need to invest in a FMIC.

Why are u doing 5th gear pulls for tuning. Why not 3rd gear pulls, or 4th at most?

If you add fuel and it bogs, it is probably heat soak.

Record a log and post it.

 

[jfdid]

I'm tuning in 3rd 4th and 5th because I drive in those gears too. I don't want a car that runs good in 3rd, but then knocks to hell in 5th gear, cause that'd just blow some stuff up! And I've already done that.

Anyways, I'm going to try leaning it out a little bit, but not much, I don't want to risk some major problems.

I'll post a log up later tonight, one thing that you may think about is that my 02's are at like .94V, never dropping below .89v during a pull. I know you shouldn't tune with O2's, but, it should give me an idea.

Thanks again guys.

 

[jfdid]

Fixed: knock on wood

http://www.dsmtuners.com/forums/showthread.php?p=1198918