WS6VERT

Hey guys, just wonderin around what compression ratio is the best to run a turbo on? I was thinking maybe 9.1 or possibly 8.1 cr. Also, would this be a good cam to run a turbo on and not bleed off boost? Stealth II 224/220, 0.581/0.581 116 lsa? Any suggestions on the cam specs would be nice, I want to try to keep the cam as stealthy as possible, but still have great hp gains. This is the MTI Stealth 2 cam that I hear is a magnificent cam. Thanks guys.

smokinHawk

iTrader: (48)

it really depends on what type of driving you do. if its going to be a street mostly id do 9:1. if mostly track with some street duty then 8.5:1, if an all out track HP monster then 8:1

that stealth cam sounds like it would work well with a turbo.

SSnakekiller

iTrader: (8)

I agree with smokinHawk on the CR. Just make sure you get it to at least 9.0, because when you want to run more boost in the future, a higher CR like 9.5 will limit that...

Most boosted cars I have seen and most cam companies will recommend 114LSA

smokinHawk

iTrader: (48)

114-116 would be a good lsa depending how high you want to rev it.

MECHAM

iTrader: (4)

for my sake.

114 lsa is a lower reving cam vs a 116 lsa?

Noyzee

iTrader: (37)

I would say to go 9-1 i wouldnt go less.
and i have a perfect FI cam for you, (for sale)
it is a 234/228 576/571 114lsa. It was ground for my old turbo set up and has about 300 miles on it.
either way id stay 114 or 116 and 9-1 cr jmo

WS6VERT

thanx guys, my car will be entirely a street car, there is no local track aroundabouts where I live so any sort of race setup wouldnt be practical. I think I'm going to go with the 9-1 cr and the Stealth II cam. Thanks once again.

smokinHawk

iTrader: (48)

on a 114 will make its peak power higher in the rev range then a 116
so the lower the lsa the higher it can rev (makes power at higher rpm)

WS6VERT

yes, but wont there be more of a lopey sound to that cam? I'm looking for a very smooth idling cam.

Pro Stock John

iTrader: (34)

I'm sure that 224/220/116 MTI cam would idle very smoothly. Heck I had a 232/232//116 cam that idled almost without tuning like five years ago.

98Zam

ok, i understand the lower cr because you can use more boost, but why would you only do 8:1 on a "track only hp monster car" why not a street car/when needed monster HP machine

basicly, im just wondering why you cant have the best of both worlds with a low compression ratio that allows more hp easier with boost increase, and low boost for "driving around". are their daily driving issues involved with the low compression?

ChevyNo1

The lower the compression the less low-end power you will have until the boost kicks in. So if you don't get serious boost until 3K, then the car will be doggy under that. I still decided to go for 8.7:1, which would work out pretty good.

Short Round

what kind of fuel will you primarily be running? what kind of duty? (street daily driver, weekend race car, full race car...)

V8_DSM_V8again

Street 9:1 to 9.5:1 depending on boost level and fuel used.

Gas race 7.5-8.5:1

If I was'nt going funky fuel I'd run 7.8:1 or so even on the street... Pre boost power on the V8's I have seen is so much better than a 2.0 fed by a T61 (That has lag.....) I rode in a single turbo V8 with a T76 and was like umm you call THAT lag......

Race alcohol 10-12:1

JoshuaGrooms83

iTrader: (2)

thought id dig this up a bit to get some up to date info.
im wondering about 9.5-9.7 CR since this is about what will put my 5.7 to with 317 heads if my math and data is correct.
with that said, would 9.5 be a safer range with 10psi fro my street car without compromising too much out of boost throttle response?

VincentT

I'm also wondering about this. I know meth is a great option to take care of detonation problems under boost when using pump gas. In fact, much of what I've heard runs along the lines of saying that meth is pretty much required with pump gas for anything 10psi of boost or more. But, if I'm going to get a forged rotating assembly anyway, why not get dished pistons to bring the CR down instead?

For instance, I run an LS6, which for my CTS-V Is 400hp stock with a 10.5:1 CR. If my math is right, dropping the CR even as drastically as down to 8.5:1 would only sacrifice around 25 hp with no boost. Is that loss of low end power the only problem when dropping the CR? If it is, it seems acceptable for a mainly street car on pump gas.

L92 fox

iTrader: (2)

My motor is 10 to 1 and with the cam it is still 8.8 to 1. I plan on running 15-16 psi on pump gas with meth. I don't see the reason to run a really low compression ratio like 8 to 1. It would feel like a dog out of boost. And I know people say you can run more boost with less compression but most people run factory cast heads that shouldn't be pushed past 20 psi in most cases.

Nitroused383 motor is 11 to 1 with 130000 miles on it an he made 700+ whp on pump gas I believe. My factory turbo f150 has 10 to 1 with 15+ psi, granted it uses direct injection but it is still on 93 octane.

godlyxdan

iTrader: (1)

To answer your "For Instance", no a 2 point drop in compression would net you a much bigger loss than 25hp. It would feel like a dog out of boost. General consensus says that CR in the 9's seems to be the best place to be for boost. Really depends on turbo specs, power your looking for, and boost you'll be running etc... But you'll hate 8's trust me

Ironmancan

My street car has 10.6 to 1 I had about 9.5 to one and I really like the additional compression it's noticeable to me. Not being a purpose built drag car I would keep as much compression as you can. Im seeing 741hp with 14 lbs of boost and meth. I will be mounting up some bigger turbos shortly and seeing what they will give me.

For a street car how much power do you want? 1k hp sounds nice but your not going to hook that kind of power or use it on the street so what's the point. I will need the additional power to run 200 in a mile event if it wasn't for that I would have stayed with the smaller turbos.

Obviously if we're talking a drag car the lower compression would be ideal. My street car acts like stock, no loss in low end performance and it's a lot of fun in boost. I'm limited in the kind of boost I can run but I'm ok with that. My .02 cents.

JoshuaGrooms83

iTrader: (2)

so the 9.5-9.7 CR with say a mild cam (224-228 range), T76 .81 AR rear mounted turbo, 10psi, premium gas, and 600 hp goal, would this be a decent street car with every so often track time?

also on a side question, how would the compression be affected with a 228R cam?