I was reading in the Tech articles and I saw something about increasing the fuel pressure to 50 psi on a stock 350 tpi resulted in about a 58 ft-lb torque improvement and somewhere in the 30s for horsepower. Why do I find this hard to believe? If this is infact accurate, how much of an improvement would this make on my stock 305 TPI and how much would this part cost? Also, how much would my gas mileage decrease (since it seems obvious that it would)?

 

50 psi is too much for a stock 350 TPI but about right for a 305 (they have smaller injectors). They cost around $75-$100 I think and are more of a tuning tool than a bolt on. My gas mileage was not affected.

Danny T

 

That table in the tech data was copied from TPIS or some other parts pusher's book, and is a little unrealistic. They're probably forgetting the liquid nitrogen they used to cool the intake for the 50psi runs or something else exotic to get that big of a gain.

But to answer your question, yes they are a worthwhile tuning tool. However, don't fall into the trap of thinking there is a magic number you can set it to to get more performance. You adjust an AFPR at the track, or on a dyno, or some other controlled situation where you can monitor the performance change. And just like with setting timing, put it wherever you get the best performance. It's not unreasonable to find a couple tenths / mph just with basic tuning...

 

also if your going to get one theyre all the same except for the holley, which i recomend. i had a tpis and aanother one(forgot which one) and they were not accurate. holley has the best design with a turn dial. the others use a screw.

 

I agree with silverbullet on this one. I have the holley and that is the easiest one to tune by far. Also I agree with Ed as well. There is no magic number because I am actually running at 36 psi on my 305 with is actually below stock and I have some modifications done to my car. I have yet to get my injectors tested but I am thinking that the person that owned the car before my decided to put in 22#ers instead of stock 19's. You will need to hook up a scan tool while driving to find out exactly what the right pressure should be.

 

just out of curisoty, do you guys check your fuel pressure with the vaccum hose off or on? and what pressures do you have it set at?

 

Take the reading with the vacuum line off. Stock my 305 was 38psi, with the mods I have 40 seems to work best.

I'm gonna have to agree and say go for the Holley unit to, the others are crap. If you got the extra $$ for the Accel fuel pressure guage, go for it.