More octane vs cooler air

Dan B

Junior Member
To run max boost on stock setup (14.7 pounds?) without knock or without ecm pulling timing, what is better option between lowering air temps (better intercooling) or increasing octane (adding additive to 93 pump gas)?
 

Sy2623

Member
Octane, need to increase the fuel supply. A lot of good info and tech articles here on getting the most out of these trucks.
 

Dan B

Junior Member
Octane, need to increase the fuel supply. A lot of good info and tech articles here on getting the most out of these trucks.
Agree with the archived info, been reading quite a bit on here, I search both thru the search feature and thru Google using syty.net in the. search.

Are you saying stock pump and injectors don't provide enough fuel for stock boost? In an old thread in here someone wrote that back in 1991, the 91-93 octane that the stock chip was based on is closer to 97 octane in today's available fuel. I do supplement with rp max boost 8 oz to 10-11 gallons of 93 but got to thinking if I made intercooling improvements, would that allow straight 93 to more likely support 14-15 lbs boost (with out additive). Guess both would be best but then I could see myself getting greedy and screwing with 3bar map/chip. Injectors, exhaust, ultimately breaking things and parking it.
 
I'm fairly new to these trucks too and still learning but here's what I what I have experienced. Although I do have larger injectors and an upgraded fuel pump, it should not matter at stock boost. The stock system, although marginal, should supply enough fuel for stock boost levels regardless of the octane. The factory just did not put a system in that would support "turning it up". So, if your stock system is up to snuff you should have no problems with the amount of fuel at stock boost levels. This is where things such as a fuel pump hotwire kit can help your stock system perform it's best.

Not enough octane can definitely cause knock but it is not the only source. Running lean, too much timing, too hot of a spark plug, plug gap, carbon build-up, high air temps, engine temp, and mechanical problems (bearings, mounts, the exhaust system hitting the frame, etc.) can cause knock or be picked up by the knock sensor causing the computer to pull timing. The tricky part is figuring out just what is causing it but if you have a stock truck running stock boost, 93 octane fuel should not knock at 15 pounds provided it is a quality fuel and is accurately rated. I know sometimes fuel varies by region or time of year but 93 should be 93. It's not a Sy but on my Buick I wouldn't start seeing octane related knock until 17+ pounds on the stock turbo.

In my truck I run a Turbotweak chip with everything set to stock. I run pump 93 with no boosters and I get no knock at wot. I will occasionally get a couple of degrees retard due to transitional knock (going from cruise to wot or at the shifts) but it goes away immediately. Of course my truck is street driven and not tracked so no heat soak to deal with on my occasional wot runs. I have also heard that the fuel quality has changed and if you are still running the stock chip, the timing might be a little aggressive for today's fuel so that may be an issue. An aftermarket chip might help in that regards. Eric at Turbotweak would be the one to talk to about that to see if that could be an issue especially if your knock goes away with just the addition of octane booster.

HTH
 

Dan B

Junior Member
Hey thanks man, good reading rite there.. I'm lucky enough to have a babied low mile ty its so much fun to leave intersections straight or turning it flies.. Not gonna mess with it but will probably get a scanmaster (does it show boost?) Hot wire kit (on your recomendation) and continue to run max boost which in theory brings my octane up to 96
 
Scanmaster does show boost but I suggest a good mechanical boost gauge for accurate boost readings (a lot better than the stock system). I like the ScanmasterG better than the original Scanmaster. It is round and can mount in a pillar pod with the boost gauge. Makes them both seem like they belong there. I would consider getting a modern chip too. It can only help by giving you some tuneability and some more options working with the computer and maybe better drivability. No body can tell you've done it and It can be easily removed in just a few minutes if you need to return the truck to stock for some reason.
 

Dan B

Junior Member
Appreciate your suggestions I just might chip it someday but for now am inclined to stay stock and live with the limitations on the advice of a few seasoned members here with a ton of miles on their trucks.. I just love getting in it and reliving 1993 all over again a time men were still men, tough for me to think of messing with it and wrecking a good thing....for now
 
I understand your thinking but I don't consider anything that can be undone as easily as it is done and leave no trace, a mod. It's nothing that will change the feel of the truck, it's still going to be an early 90's GM S series truck, so it's nothing you should be afraid of doing. Either it helps or it doesn't. If it does help there goes your need to have to mix fuel additives in with every tankful. I don't know how much the Max Fuel costs but the savings may pay for the chip in short order. If it doesn't help, take it back out, no harm, no foul. You may lose a few bucks but you may be able to resell the chip and not lose much or it could be a good bonus for a new owner if you ever sell the truck.

Now I had to chip mine because I went with bigger injectors just incase I do want to turn it up a little in the future but while I'm running stock boost with the base chip program my truck feels just like it did before I made the changes.
 
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