How much boost can I run...


Mar 11, 2002
Putting a new stock turbo w/ adjustable accuator on my 85 GN. In a completely stock setup, how much boost do you think I should be able to make on 93 octane w/out detonation?
Don't waste your time.....

Before you go touching the boost you need to upgrade the Fuel System....

Walbro 340M Fuel pump $100
Hot-Wire kit $60
Adj Fuel pressure reg $100

Then start to worry about boost.
Herb, I've had 5 I/C cars, this is my first hot air car. What kind of gains could I expect with those upgrades?
Once you have the basics taken care of you should be able to get around 15-16psi on pumpgas. For some reason me and my dad could run 20psi with a degree or so of knock only on the 1-2 shift. Don't know why but I've heard of other people being able to run a lot of boost on straight pumpgas with the hotairs. 20psi is about as far as you want to go or you will start slowing down even if it's not detonating. At that boost level at the end of the 1/4 mile the charge air would be around 320 degrees. With very basic mods like fuel pump, regulator, K&N, boost, and a chip you should be able to get into the upper 13s on street tire.
Most can't get more than 16-17# on the stock hotair setup without some detonation...If you have a good custom 84/5 chip(low timing) made, possibly 18# at the most...the stock turbo is good for the stock boost levels, but create way too much heat at higher boost levels...

Hope this helps...
The ONE time my boost gauge TOUCHED 16 psi, I got a single knock that sounded like my block was hit with a cannonball!

(of course, a hot 16 psi & 91 octane really don't go together very well...)
Don't ask me why but both me and my dad ran 19-20psi on the stock hotair chip on 92 octane. Like I said it would occasionally knock on the shifts but that was it. This was with 02s ~800mv. With the same 02s and an intercooler and downpipe it would knock at 17psi with the stock chip but it would be making a lot more power. Strange but I also have a friend with the same experience.
I've ran 19-20 psi easy on the street with pump gas with no knock, and 22-24 with mixed 110-112 cam2. I can work if the car likes you.:D