help tuning alcohol injection


Aug 7, 2001
I have a 1986 gn,160 thermostat,TH downpipe,no cat,2 1/2 ATR exhaust,Lubrant 94 octane street chip,ATR cool air induction,Walbro 307,hotwire,adjustable regulator,boost commander,SMC alcohol kit,TL as my scan tool,and I always run Sunoco 94 and xylene so I have 99.5 octane in the tank.I have been having a hard time tuning for proper 02's since the addition of the alcohol.I use denatured alcohol.Here is where I am at now.I have a base fuel pressure of 42 pounds,21 pounds of boost,alcohol turn on at 10 psi,and pump speed at 5 1/2 to 6.Until the addition of the TH downpipe I was able to run the pump speed at 7 1/2 but it would be sluggish at this pump speed with the TH downpipe.Go figure.Anyway my best run has been 12.62 with the majority of my runs being in the 12.7 to 12.8 range.Here is the problem,when I leave the line my 02's are in the 838 range but at the end of the run they are in the 780 to 790 range.I get 0 knock.If I turn the fuel pressure down I get 2 to 3 degrees of knock and my top end suffers 2 to 3 miles an hour.If I turn the fuel pressure down and the pump speed up I run no better.Now get this,I can run 18 pounds of boost without the alcohol and get no knock.I then set my fuel pressure at 43 pounds and my 02's are great the whole run.This is in the summer weather my fuel pressure may have to change as the weather cools but that is just a tuning issue.I can still get in the 12's at 18 pounds of boost.Some of you who have been running alcohol longer than me,what do you think moving my alcohol turn on point to 12 or 14 psi would do to my 02's?I understand it takes the pump 1/2 second to spool up and I don't want to detonate.Any and all responses will be appreciated.Bruce
I would try the turn on point around 14psi. If you turn fp down and get knock then turn up the pump speed on the alky.
Test and tune watch for knock.
I got an EGT gauge from Steve when i got the SMC alky kit.
The price was the best i found by far and it has a max hold so you don't have to watch it. This thing is great for fine tuning IMO.
My turn on point is 14 and pump speed 7-8 and other than the chip and boost commander we seem to have the same combo.
Well, all I can tell you is how mine is set up. Unfortunately, I use an OTC 2000 so I can only see one parameter at a time. I tune for 0-5 KR, basically, but check my O2s once that is established. My alky kit is home built with NOS nozzles, but your combo (and ETs!) doesn't really sound all that different than my GN's (see sig). What kind of MPH you running?

My turn on point is about 15 psi, my two jets total about .045" with 70% Isopropyl, I run 30# inj., I have to run up to 62 psi fuel pressure to get mid/high .800 O2s as my GN loves to run rich, straight 93 octane gas, 93 chip, and about 21-22 psi boost.

You "may" be able to run a little more pump speed if you raise your turn on point. It's my experience that you can get away with turning it on sooner with a faster spooling turbo, but that might not be optimal. If you can get away with running 18 psi without it, 15-16 psi turn on point might not be too bad. Once I installed my big IC neck, I could only run about 16-16.5 psi boost. I'm not sure about the "spool up time" of the pump. I plumbed a gauge inline with my kit, and it does take a split second to reach full pressure, but remember, there is alky being injected as soon as it reaches a pressure higher than the boost.

With 94 octane, I'd think the xylene may be overkill. Once, I threw some Xylene in with the 93 octane and my alky on 'cause I knew I wanted to crank up the boost and run my 100 chip. 25-26 psi with a stock turbo and no KR. Course, the car didn't go any faster than at 21-22, but I tried! Maybe with the denatured you're running richer than is indicated with O2s?? (many have said alky can throw off your O2s, but I can't say for sure)

Yes, I'll bet when it cools off this fall, you'll find you need more fuel and/or alky pressure! But man do these cars like that cool air!