how many turns of rod is one PSI of boost(usually)


New Member
Nov 28, 2002
I have just started to mod and tune my 87 using TURBOLINK. I know all the theory behind what I'm doing just have no experience. I seem t get different boost levels once in a while, cant zero in on what I'm doing. So I cant get a handle on how many turns does what. And also what kind of O2 mv changes can I expect from fuel pressure changes. I just started tuning today, basically. I just put in a WALBRO 307, and hot wire, Thrasher 92, with sunoco 94. I had a faulty stock pump I guess, was pinging with stock actuator and the chip. The hot wire and and pump solved that. Then I put on the adjustable rod, first test hit 22.9 psi, turned the hell out of it, still get 21, now its almost as long as the stocker, and its still 17-19. And turning up the FP doesnt seem to do much. I'm getting it settled now, but what boost levels can I expect from stock injectors, and only 94 octane? STill get knock once in a while, but for most part, I am getting good mv's and very low KR around 17 psi.
1 turn on the rod is aproximately 1 pound of boost. With 94 & stock injectors I ran 15-17 pounds boost regularly.
with the stock turbo I used the term "a pound a round". Shorten one turn usually got you about 1psi boost
The Trasher chip you are using is throwing tricks at you. It has a fast spool feature that will cause a significant boost spike on a tight system. The more you crank the rod, the greater the spike.

Take my example, if memory serves correctly. Generally I would set the rod for about 17 lbs with 93 and a power plate (generally), this setting would spike to 18 and sometimes 19 before settling back to 17. Now, I have it set for ~20 (alky), but the spike sometimes hits 25 !!! (like a multiplier when you go up)

Set your FP to 45, then creep up on the boost (adjust, drive, adjust, drive)until you tickle KR. After you get the acceptable boost level (factoring in the spike), then try to back off the FP a bit at a time until O2's look good. Also remember that big changes in the weather can affect your settings.
THATS IT EXACTLY! I the boost spike thing. I thought it was me. And depedning on how I drive it it spikes alot or a little. I finally got it all set up with some long 2nd and 3rd gear pulls. things look great at around 15-16 psi, low 800's for mv's. But then every once in a while. If I do powerbrake launch, I can hit like 18 or so, and it pings through 1st gear. So I should set it up so these spikes in first only cause minimal knock, and then the rest should be fine? What would you allow it to do. Like 2 or 3 degrees of retard? I have heard some say, tolerate no knock. SO I guess I'm going to have to balance it a little. Because its a shame to only run like 15 psi, just so hard launches dont cause some knock. Plus its 94 octane with a 92 chip. Tthis is my first chip, I would like to try others, what cheaper chips do you recondmend for stock inj's. I want to go right to 50's soon. THANKS ALOT
Although there are many other out there, the only other chip I have tried is a Red Armstrong 93. It has slightly more timing, but no fast spool. The boost is rock solid. I have run my best times (stock trim) on this chip. It's better for power, but I keep the Thrasher for the anti-theft, general smoother driving characteristics, and smoother cold start.

The only problem with your plan to make an "acceptable spike" in 1st gear is that it limits you from a quick WOT from a roll. This is where I have seen my worst knock.

I am in the same boat as you on this one.
After trying every "cheap trick" I could think of, I ordered a boost commnder last week. I hope to have it in and tuned by this weekend and I'll report back. I have tried bleeders, relief valves (grainger), and any combination I could dream up just so I could keep running this damn chip, including a Thrasher 100. I even had a relief valve and the arm adjust to make the wastegate puck loose (literally flapping), but it still spiked a little with that slow spool. I believe that these methods, including the Thrasher, are more suited for bigger than stock turbos.

BTW, if you hear the knock, it's too much and likely greater than 8 degrees KR. I get a bit nervous at anything over 2.0, ESPECIALLY in 3rd gear.
thanks again...and yes I heard the knock a few times. And yes I was scared...T-link showed 17.9 degrees of retard @ 22.8 psi. on 94 octane. How this thing still keeps its coolant and oil separate is beyond me. My own stupid fault. But I have a propane kit to put on, that should do some good.:D