How much octane do I need to safely run 20 psi boost? I was running 118 on the dyno, but I think that is overkill$$$. I dunno if 100 will be enough, but what about 105 - 110?

 

Yeah I'd say regular av fuel would be fine. Only 20 psi dyno experience I've had they ran 106 av fuel and it worked great.

 

its all about timing anyway pull timing and use 93 or keep the timing use 100 or add timing and use 116 timing is whee power is made. race gas burns slower actually lowering performance in vehicles. same idea if you put 93 in your tercel. it will run worse because the maps are setup for 87.

 

ok cool, I think 100 will work fine. Several people said they use it for this boost

 

For anything over 17psi, I ONLY use C-16. Why risk it your motor and new turbo to save a $20 bucks? It ain't worth it.....

 

Silver nintey three, get water injection

20psi all day, have run up to 22psi on 98 RON (eqiv to your 94 or 93 MON ?) octane pump gas with lean a/f ratio !

It's different, and some people say it's wrong, but it does work........ I used to use aviation fuel before running WI, now I just fill up at any gas station and have nothing to worry about.

I got tired of thinking about what boost to run and whether I had enough race gas etc etc. Just an option for you to think about, not that I am trying to convert you

 

You can run as low as 91 ocatane on 20 psi. It's all about the timing and tuning maps. This what lots of guys in California have to do due to their low octanes there. If you car isn't a "weekend only" car, and you actually drive it around like a normal person does, then I'd say have it tuned for the highest octane you can commanly find in your area at the pumps (93?)

 

Sorry, no way in hell your running 20psi on 91octane. I don't give a **** how much timing you pull out.

 

Ya, maybe not quite 91 octane and 20 psi. Premium (93 octane) is definitely comman for guys to run 20psi on though.

 

If you say so.......but Im sure as hell not doin it.....

 

Me too !

Not without WI, those guys must be crazy, not saying it cant be done, but where is the saftey margin

 

how come other cars can run more boost on pump gas?

 

i'll soon run about 15+ PSI with 91, it's called water injection baby!

-mike

 

The reason I wanted to run 100 is because there is a gas station about 40 min from here that has it on pump for $3.99/gallon. I picked up 15 gallons the other day. There is also anothe rplace than sells up to c118 and is much closer, but they were closed that day. I'll probably pick up 5 gallons c118 and mix it with the 100.

 

I was just stating it can be done and can work good. I still would never do it - not much of a margin for safety like you guys said.
When I build my 20B in about 9 months, there won't be anything but 100 octane aviation fuel being fed to it.

 

Engine condition, engine type and model, compression ratio, timing, air/fuel ratio, ambient pressure and temperature, humidity, boost gauge error, intercooling, water injection, nitrous oxide, etc. IMO most of the info in this thread is going to be pretty much worthless to you except as a very basic guide.

 

Too true !

A majority of engine performance related shops and enthusiasts are not the most analytical people around & some plain dont want to know ! .....hence generalizations are abound

You realy need to look at all of the factors as stated by Evil Aviator to get an answer applicable to you.

 

I think he meant other types of cars (i.e., non-rotary)
My answer would be piston rings > apex/side seals as far as boosting goes.