This statement is absolutely correct. You can throw in a 10lb spring and make no lower than 12.5 to 13lbs of boost off the wastegate. Change to say a much bigger cam or swap to a freer flowing head and you might actually see 10lbs off the wastegate. Just too many variables to really say for sure.

Decide if the car is going to run more pump gas than race gas and then go from there. You can always adjust the boost.

 

This thead has always said "race gas" from the beggining.

I think you guys are pretty much saying the same thing I am, just in a different way. Its simple, for a safe tune close to detonation but not reaching detonation you can go race gas, high CR, and low boost, or you can go race gas low CR, and high boost. Its really all about how you want to make the power. Yeah, a higher CR will yeild more power, but so will more boost.

 

Well run high compression and VP IMPORT. The tq and response would be unreal.

 

I voted for 9.1 since that's what I'm running....I think 8.1-9.5 you would be fine, good luck with your build...

 

Seems like the more cubes the higher CR you can get away with since it can flow more air. PSI is only a measure of resistance right, 15psi on a 346 compared to 15 psi on a 408 is just a tad different. It would be allot more difficult to hit a high hp number with a stock cube motor with high compression. Back of the cr a bit and turn up the boost and you are back in business.

Doesn't ProstockJohn run 8:1 on his 346 and close to 25psi? Not sure how much power he makes? I'm building my 370 right now with right on 8.5:1 and if it was a 408, which I already had it built to, it would be atleast 9:1-9.3:1. Running less boost but surely not less air

Jsut for you hard core racers this is a street car and not max performance otherwise it would have higher CR. Around 9.5 IMO I don't see the reason to go any higher at all with FI unless you have a hard core setup with the best gas out there but not my cup of tea.

 

You mean there's no reason to go higher than 8.5, or 9.5????

 

No I said 9.5 but thats just me and I am not the only one judging by the pole either. We are on the debate of CR with a ton of boost, I'm not speaking generally here on a specific basis. Trying to keep this puppy on track.

 

I'd shoot for 8.5 with 18+ psi.

 

I was always told to shoot for 8.5:1, so when this thread started I never even put much thought behind it and picked 8.5:1 It was instict.

It took me a few days to finally go back to my instict for my own car though, lol Thought too much about it, but am going 8.5 now and couldn't be happier about it, especially when I want to really crank on the boost.

My statement stands for higher CR and race cars though since they aren't being driven all the time, etc. Still though, not going to be able to boost it to the moon if the CR is too high. Thats why I said 9.5 max IMO when talking about big boost.

 

I thought your car was going to be primarily a street car. Since when do you need 20psi on the street?!??!??!?

 

I don't want to get the thread off track but I never did say that I will use 20psi on the street. You are putting workds into my mouth and obviously like to dispuit, which is fine. I stated that I'd like to run as much boost as possible on pump gas, and when the time comes to go to the track I can lean on the boost and turn on the meth kit JUST for insurance even though its probably not needed to an extent.

Primarily street cars are generally lower CR whether you want to believe that statement or not but I had more than enough reccommendations to believe otherwise. Simply not only for the safety factor when on pump gas but whenever you want more boost, which allot of the times happens in FI. With lower CR it enables the user to get the most out of his combo as long as the poer adder can efficiently support the power. Even whether its on pump or race gas IMO, when on the street do you really wanna be getting on it on a hot summers day with somewhat higher CR and decent ammount of boost? It only takes one bad pull if the detonations there and there go's head gaskets or even worse Of course if one's plans is to run lower boost on the street than ya, go with higher CR. What if you change your mind, I wouldn't want to be running race gas on the street. Have fun with that, LOL Yes meth works too but only to a point and I never believed relying on the kit. You can look at it as a band aid, what if it fails? Mix must be consistant, constant deteriorating of the system, etc, etc. If you don't mind checking its operation before you go for a drive everytime be my guest. Everyone's goals and needs are different right. World would be bored it everyone ran 8psi on a completely stock motor

 

i am going for 9-5-1 on mine

8-5-1 or 8-1-1 will accomodate a ton of boost though

 

You're funny man. This thread is a discussion about compression ratio so I'm not getting it off track discussing your planned compression ratio....and logic. I didn't mean to "dispute" you....but I do specifically remember you getting all excited about a 9.2ish comp ratio because you wouldn't need 1000hp on the street. Oh well.

 

You should ask yourself "how much boost do I plan on running?", then get the max safe CR figured out based on that number. The thread states 15-22#'s of boost on race gas. I would think on race gas somewhere around 9:1-9.5:1 would be ideal.

My personal car is setup at 8.8:1 and could easily support 22-24#'s on pump gas with the help from my FMIC and meth injection.

You want the ideal CR for the boost. If you aren't going to be running that much boost then you can up the CR, its basically that simple.

BTW, most guys don't need 400 RWHP for a street car, as at that power level its just excessive. 800 RWHP is pretty much along the same lines. But "yes" there are those of us with that RWHP/boost level for our street cars

 

Sorry that I took it the wrong way, just that sometimes it comes off the wrong way. I was looking forward to 9.3 CR and I think that up to 9.5 like I already said is great. I than thought to myself that I only wanna run pump and meth only when the boost is 15psi or so. I than concluded that it would be best to go with what I originally thought was the best for myself anyway. The lower CR will enable me to get the max out of my setup and with most. With the lower CR I am making up for it with the right cam, T/C and gears. I ended up gettin a custom one ground and its close to the smallest one that was specfied within my thread/poll(A tad bigger split) You've already had 8.5 and think that 9.2 would be better for you, and it probably will be. Especially with your larger cam unlike mine and dual nozzle meth kit. So have fun with it and look forward to you getting those slugs in when they come and posting how you made out.

 

Nicely said, that is what I was getting at. I mostly like the last phrase, some will argue that they can successfully drive a 750rwhp car on the street some say 650rwhp and some lower yet. I will find out what I like and slowly creep there. I will be able to do this with the same gas straight from the pump and my meth kit when I want to see its max I agree, if I was going to run race gas than it would be 9-9.5:1 Not sure about 22psi with 9.5CR though, think thats pushing it............ well for longevity anyways

 

I am going 10:1 to 10.25:1 in my build. Pump fuel too. No idea how much boost it will take to reach my goal, but 15 psi is not out of the question.

 

It all really depends on what kinda fuel you plan on using.

Philup Bridges runs like 10.4/1... something over 15psi for boost.. and lowtiming. Runs in the 8's.

This is on a LT1

 

I think that CR target will be good at your altitude. Good luck.

 

The reverse cooling helps that alot.

Thats why we can get away with 12.5-1 cr
with NA LT1's on pump gas.