You said it best with one sentence!

 

I for one am going 10:1 with my 408. I am not sure if that is middle of the road or if it is considered high compression. But I do have specific reasons and needs for this choice, as well as enginering controls in place for it. It is true you are less likely to damage an engine due to detination with lower compression and high boost as compared to high compression and high boost. People just have different needs and goals, as well as driving habits that effect a decision on what compression to run. Realy there is nothing wrong with either aproach, as long as you also take into consideration what that aproach will require to make it succeed.

 

With race gas such as C16, and having more of a track car you don't have to worry about the sheer expense of always having C16 in your gas tank, I would say a higher CR for high boost is probably a good idea. Maybe 10:1 for 15-18#'s of boost for example.

But for the rest of us that normally drive our cars on the street every day, and want to be able to RELIABLY fill up at the gas pump and still run 18+#'s of boost without having to worry about detonation, a lower CR is really the way to go. Call me living in the dark ages, but the poll proves I am definatly not alone, and the polls parameters were even on race gas.

 

Yup this was my argument the whole time, either one will make allot of power and no way is the wrong way but just can be better which we are always wanting. Great things come with great risks of course though!

 

Kenny Duttweiler told me, Less compression, more boost.

If you want the best of both worlds for a track car, high compression and ALKY

 

Best of both worlds would be meth injection, C16, high boost, and a higher CR.

 

quit talking about lower compression and pump gas... 4 pages mentioning that and the guy wants opinions on RACE GAS aka NOT PUMP GAS

its about race gas here!! you can get away with more compression since race gas is less detonation prone. With proper tune, meth and intercooling, i THINK you can easily run 15-20lbs on a 9.5-10.5 to 1 motor as long as you use a high octane race gas. Maybe o-ring the block/heads and such because cylinder pressures will be very high

 

I AM THAT GUY!!



I agree to a certain extent, but maybe not that much. Anyways thats what the poll has been for from the beggining and the results show what the majority thinks. I agree that the majority is probably going on the safe side of things, or perhaps didn't read the first post before they polled, thinking it was on pump gas instead of race gas.

 

Safe is always good tho. Just goin by what i have seen from a few cars. Guys will fill up on race gas and run their race boost settings which can be 5-10psi more boost over street setups. i dont think 15-20psi is asking too much for a 9.5 to 1 engine on race gas.

I know a guy on another forum building a 30psi boosted F1 charged smallblock and he is around 8.5 to 1 compression but i believe he is using meth and pump gas. Makes sense to me you can add a point of compression and cut 10 psi boost easily with the added benefits of race gas. Meth for more safety if needed

edit: plus you can add a larger cam to help bleed off pressure and lower that dynamic compression. Bigger cam should help make more power anyway so possibly less boost can be used

 

If your going to use meth with race gas, and i'm assuming it would only be for the cooling affect than you don't want to run anymore than 110 octane. 116+meth will slow the burn down too much.

 

That would be the only real benefit to it, as the race gas already takes care of the octane and the methanol would simply be for cooling the IAT's.

 

Why not just some decent gas than and meth. Some use meth as their intercooler

 

8.8:1 Is my optimal choice.

Built many many incredible setups with that ratio. Great all around performance including a slight increase over the 8.5

-W

 

Ya I am beginning ot think thats what I should have went with instead of the 8.5 like you said jsut a tad better. Either 8.7 to 8.8 oh well, it should still be killer with a **** load of boost!

 

If you plan on running lots of boost, you'll need the help of an intercooler as well, as just the meth won't be enough. You might eek out another few pounds of boost by not doing an intercooler, but the meth simply cannot due what it can do with the aid of an intercooler.

I am running 8.8:1 in my car, and it would safely hold 22#'s of boost on pump gas. It is a good combo for someone who wants to make lots of boost on pump gas.

 

I'll admit I read the poll question and not your first post. LOL, with that being said.
11:1 - race only on C16 22-24# boost
9.5:1 - street/strip 91 octane 14-15#'s
8.5:1 - DD, occasional runs at strip. 12-14#'s 91 and 18-20 on race gas.

Mind you this is a bit on the safe side due to losing a LSx FI motor 4 years ago and 8000+ DA. Sorry about the altitude thing again.

-Tim

 

You should have went with 9.2


lol

 

Nahh, its cool no regrets. I will be able to turn the boost up even more and not have to worry about it. I am going for durability/longefity too I still think it will be great and glad I never went with 9.2 but maybe 8.7-8.8 which really isn't that much of a difference. This is my first serious build so I think its even better I went with this. If its not enough, LOL, I'll bump it next time but I am sure it will be. If I upgrade anything it will be the turbo and/or turbo kit

 

I was just funnin' with ya, lol. 8.5:1 is PERFECT if you ever want to turn the wik up to 20+ psi.

 

Yup I know, but you are right and thats one of the main reasons that made me decide on this. I wanted the most out of my system in terms of boost/power running the same octane all the time and I think that 8.5 was it.

The poll even makes me feel better about it too