Race gas & upping the boost??

[DrBrown]

Im just looking for a base guideline here. If my fuel system is prett ymuch maxed out on 7.5 psi can you run race gas and still be safer at say...8.5-9 psi?? I wanted to run 8.5 psi because my car really really likes it up there but I just wanted somewhat of a safety net for track use. So some people have told me to consider C16 or cam2 gas and just go nutts with more boost. But Im affraid that more boost still wont be safe since my stock fuel system is pretty near at max right now. About how many psi of boost can you increase by adding racing fuel of 100+ octane?? All opinions are welcome and I just wanted to get a idea since you all use race gas more then most people in my shoes. Thanks everyone!

Dan

 

[NOSLO2PT0]

The limiting factors will be your fuel pump and the strength of your rods. I've run 21psi on 110 race gas, using stock fuel injectors, no fuel control, and a Walbro 190lph, stock turbo, stock SMIC, with no problems. however, it says you don't have a DSM, so I don't know what kind of car we are dealing with. I would say that if it didn't come boosted from the factory, the RODS are going to be your limiting factor.

 

[Syndicate13]

Well since you don't have a DSM listed as your car then we can't really help much. It depends on your motor how much boost you can run. If the higher boost is causing you to get knock then yes, race gas will help alleviate the knock. But, if you are in danger of lifting the head or blowing a head gasket because of too much compression, then race gas will not help with that.

 

[DrBrown]

Thanks guys. I have a 95 Probe GT which includes a 2.5L 24-valve V6 with 9.1:1 compression ratio. Right now I have a 12:1 FMU running well over 100 psi of fuel on a 255 walbro pump with stock injectors and I will be adding a 7th injector into the intake stream. I actually need to turn the fmu down so the injectors arent past 100% duty cycle. So thats alot of fuel but the stock injectors are so crappy (220cc) that they dont supply the volume I need. I dont have any engine control yet so I cant get any knock sensor readings but I can say that the car did not knock, ping, or hesitate and ran marvelously on 8 psi before my bearings failed last night GRRRRRRR. I know my rods can handle well over 350 whp because its been done a few times on old motors. But my motor is my motor still. I am only pushing like 250 whp so I dont expect rods, pistons, or crank to be a problem. If anything its going to be old 102k mile of head gaskets But when I get my turbo back from the shop Im going to try 8 psi again and maybe add a mix of toulene...IF I can actually find some. But I have heard most hardware stores stopped carrying it We'll see.

So if I had a DSM running 15 psi on a 14b, stock smic, stock injectors, and upgraded pump as most people do...what would be the max boost you would recommend running with a 30% mix of race gas? Thanks again gents!

 

[nanokpsi]

Well, turning down the fmu will not lower injector duty cycle. It will just lower the amount of fuel that is injected each time the injector "fires". If your idc are that high your fuel system idc's already hurting. The only way you will be able to run more boost would be to use race gas and then lean it out. Race gas will let you run leaner so you can lower the duty cycles, then you can run a little bit mroe boost. In your case, If the injectors are that maxed out you probably won't be able to run much more boost.

If you are running that much on the fmu (12:1) then you should be able to lean out a little, giving your self a little more room. It's really hard to say not nowing what you tune with or where the tune is at currently. Hopefull I was of some help.