turbo performance Options

[nsyr]

I know there a few people out there with turbo 4's. Does anybody have any performance or reliability figures.

[andys]

Pressurizing the intake overcomes those breathing limitations up to a certain point. one or two pounds of boost will make a surprizing difference on one of these cars. Figure at least 15 hp per pound of boost for the first few, then the increase starts to drop off. By the time you get over 5 psi you are prolly only going to be gaining around 10 hp max per pound of boost increase, maybe a little less. Above 7 the increase drops off more due to the efficiency of the turbo system and the heat of compression and the head design.

Sammy,

Well said (though I'm not sure about that 15HP/lb boost)! When I first started messing with turbo's some 35years ago, an engineer at Garret advised me that the most noticeable gains are the first 3 or 4 lbs boost, and that for a street car, that's usually plenty good enough. Go more, and things start getting increasingly more complex. As for intercooling.......low boost levels keep the heat of the intake charge low as well, so you can run comfortably without one (they are advantageous though). Another tip I got from a local Indy competitor way back when, was to not bring the boost in at too low an RPM, as it puts a tremendous amount of load dwell at poor rod angles.

This (to me) all centers around what you expect, and what you want coupled with a good measure of reality. If you want to build a techno wonder with all the (expensive) components and systems, it is do-able. If you don't want to go HP crazy, a nice safe and affordable system is very possible, IMHO.

Andy