So I am starting my build. I talked to a few shops and one of them keep on telling me after 18 psi I will need racing gas. I dont think this is true being that there are people out there with 500+ hp still using pump gas. I wanted to go big this year but after hearing that I realize that it will be hard for me getting my hand on race gas. I go to school in the middle of no where. I was going for a gt40r but now i might end up getting a 35r and run around 18 psi. I tried to look around but couldnt find anything. I also wanted to know from users of the 40r or 35r when did you hit full boost on a 85mm block? Sorry about the lame question.. but anything will help.. thanks guys

 

The need for race gas has a few components to it. If a tuner is having problems controlling knock with pump gas and feels it is time to up to race gas, then that is the time. Factors include turbo size, amount of boost and most importantly compression.

 

Agreed,

I usually like to leave a bit of a buffer when tuning on pump, allowing for variations of octane at the pump. Never know when you might get some shitty gas. You really can't say per psi, it all comes to the limit when knock occurs. With that being said, 450whp in my experience is usually a good place to stop on pump.

 

hmm.. ic im looking to get cp 8.5-1 compression.. I was reading and found that higher compression will require race gas at a lower psi then low compression?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by litovi3tboi503 &raquo;</TD></TR><TR><TD CLASS="quote">hmm.. ic im looking to get cp 8.5-1 compression.. I was reading and found that higher compression will require race gas at a lower psi then low compression?</TD></TR></TABLE>

Yes, that is correct. Lower compression resists knock better than higher compression. So you have to run higher boost to get around the same cylinder pressures/temperature to achieve what higher compression does at a lower boost level.

 

ic ic.. thanks alot man..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93turbo16 &raquo;</TD></TR><TR><TD CLASS="quote">Yes, that is correct. Lower compression resists knock better than higher compression. So you have to run higher boost to get around the same cylinder pressures/temperature to achieve what higher compression does at a lower boost level.</TD></TR></TABLE>


I know this is correct from a bunch of research, but if it is that easy, than why cant a higher compression and lower PSI yeild the same power as a lower compresion higher boost motor can?

It just seems that low compresion high boost motors make power than the other way.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93supercoupe &raquo;</TD></TR><TR><TD CLASS="quote">


I know this is correct from a bunch of research, but if it is that easy, than why cant a higher compression and lower PSI yeild the same power as a lower compresion higher boost motor can?

It just seems that low compresion high boost motors make power than the other way.</TD></TR></TABLE>

At equal boost levels and a huge difference in compression they do make more or less power at the same boost. But most engines that are compared aren't that big of a difference in compression.

 

so ur saying the in-signifigance compression numbers arent worth the risk in gaining power.

gotcha.