Tuning Question

[pmcgrath]

Just got back from a quick test and tune run to try out my TA49 with my dual nozzle SMC kit. For my first 3rd gear blast I had my Capser's Thumbwheel on 22 degrees and with 24# boost I got 7 degrees of knock and my 02s were .937 ... ouch. Even running that rich it pulled really hard. Without changing a thing, I tried it again and the car started to shudder as the boost went up. Knocks were 21 and )2s were .990. For these runs I had the turn on point at 11 psi and pump speed was 8. I am using Bosch 868 (36#) injectors at 44 with vaccuum off. I'm using straight denatured and using the OTC 4000E to tune. I realize that the car was running very rich. Would that cause the shuddering? Any ideas why it would run pretty good on one run and then shudder the next? Should I start by adjusting my fuel pressure to get my 02s in an acceptable range and then see what happens. I know I'm probably going to have to lower my boost a little but it seemed like I was close on the fisrt run. I didn't get a chance to do any more tuning tonight ... had to put my daughter to sleep. Any thoughts or suggestions would be greatly appreciated.

Thanks,
Paul.

 

[pmcgrath]

Forgot to mention I'm running 91 octane gas.

 

[ES1]

Way to much knock.
Some cars can run high boost & timing with Alky, some can't.
What were you running before?
I would go up only 2-3 psi boost.

 

[turboost]

You may be drowning it in alcohol. The alcohol acts like a fuel and can richen the fuel. Try diluting it with distilled water. I use a 40% alcohol 60% water mix. If you have 2 nozzles shooting straight alcohol in there I would think that may be some of your problem. I have heard of too rich causing knock. Just a thought you could try.

 

[pmcgrath]

Thanks guys for the input. Today I put my thumbwheel back on setting 4 (20 deg) and lowered my fuel [ressure to 39 with line off. I had boost set on 21#. The pump speed was on 7 and alky turn on was 12 #. The result was .97 02s with 14 deg knock ... still way too much. The gas here can't be that bad. I tried putting the pump speed up as far as 9 with similar results. Funny thing was on prior run with identical settings I only had 3 deg knock with similar 02s. Maybe the dual nozzle setup is too much. How far can I back off on the fuel pressure? I was thinking of going back to the single nozzle setup and trying that. What do you think?

Thanks,
Paul.

 

[wicked6]

I agree with turboost. You sound like you are running too much alky. Alky will act like a 7th injector and in some cases one will run over rich and have the rich knock. I run 70%/30% alky/water. I used to run st8 denatured but never had the performance I was expecting. Since running the new mixture and bringing down my pump speed I had a new best time and mph. I run 22* and 25# boost, but I am still running rich. I need more tuning.

Try turning down the pump speed and only use one spray. I have a PTE52 and one nozzle and do not have a problem. Keep us posted.