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Tuning Question

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pmcgrath

Member
Joined
May 24, 2001
Messages
55
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.
 
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.
 
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.:)
 
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.
 
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.
 
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