I've always wanted to know exactly how much compression you could run in a s50/50 street/race motor and get away with it. I know you would need a healthy cam with alot of overlap to be able to run big compression but the results would be crazy. Let me know what you guys think...
Phil

 

I don't see a problem with 12.5:1, if you run good gas in it. I'm planning on 12.5 when I stick the AFR's on there in late Jan. If I see that I'm getting some KR when I drive the car to work and back, I'll pull a little timing and have a "daily tune" and then I can flash a "track tune" into it when I get ready to race. I don't have a problem with mixing some 104 into my 93 every time I fill up either. I can buy the 55gal drums of it at a pretty good price.

 

I run 11.5 to 1 with a mti stealth 2 cam. I added a coating to the combustion chamber made by techline. Never have i had a lick of detonation with sunoco 94 gas. The tune is mail order from tsp.

 

Tangential question:

How are you guys planning on getting this compression? Domed pistons or milling heads?

When milling heads enough to get this compression, are there any valvetrain geometry issues to deal with?

Anyone considered meth or water injection (easy to control with the new HP Tuners).

Thanks
Ben

 

AFR 2x5's 12.9:1
244/250 112/112 XER
or
250/256 109/109 XER

 

 

What is the point in raising the compression if you are just going to use a cam with a bigger overlap. Esential you are raising the static compression but not changing the dynamic compression too much (depends on cam specs). I am also looking into raising the compression of my car when I do a h/c this winter. Right now I am looking at a target comp ratio between 11.5 and 12.0, I am not quite sure what cam I want but I am thinking something along the lines of a 227/230.

 

There are 2 guys around here and a few more in Tampa that run 12.0 all day long and never have problems.
That is in stock cubed cars and noone is using a cam bigger then 234/238

 

BIgger cam yeilds more top end power with less bottom end power, adding compression picks up the bottom end power lost and adds top end power.
Phil

 

Static compression is only 1 part of the story. You have to factor in dynamic compression based on your valve events that are dictated by your cam.

 

People have different thoughts on what they consider streetable. To me if I can drive to the grocery store or to work once in a while, I would consider the car streetable. I don't car about how many mpg I get on the highway.

Now when you are talking about whats the biggest CR that is streetable it really comes down to your fuel. Forget the size of the cam, even a huge cam will run in a motor on 93 gas, but for large CR motors you need high octane race gas.

My old motor was a 230/224 hydraulic motor 11.8 CR ran everyday on 93 gas.

I built up an extreme 346 with a big 245/256 .735/.735 solid roller cam and 13.5 compression. I wouldn't risk running anything less than C12, usually ran C16. Now I have driven on the street to the store etc or to local car club hangouts, however at the expense of $6.00 per gallon race gas.

My new motor is a 408 with a even bigger 275/286 .793/.793 solid roller cam with 14.5 compression, BIG CAM + BIG CR = lots of power. The flywheel HP is over 730hp NA. Of course I only run C16 in the car, but this motor idles better than my 346! I would gladly jumped in the car and drive around town. It would be expensive but could be done.

Back to my point...CR of 11.0 to 12.0 there is a little power gain but your maxing the limits of being able to pump gas. If you want big power go big CR, but you have to use good fuel which makes being streetable harder...

Lee

 

I'm mildly worried about running 10.8:1 in my small cammed motor. I'll have a DCR around 8.3. Heavy truck. Used for towing. etc. etc.

 

Turns out dynamic compression ratio is a bit of a straw man. Your dynamic compression ratio at idle is certainly lower than static, but once you get the RPM up and the acoustic and inertial effects kick in, your effective dynamic compression ratio can be greater your static compression ratio.

 

You mention that there is little power difference going from 11:1 to 12:1 but it can't run as well on pump gas. So what do you think is the ideal compression for the F13 230/232 on say a 112+2? This is what I think I am going with, and I thought about 10.8 or 11:1 was about as high as I should go. Can I go higher running on 92-93 pump gas (maybe occasional 91 since not all gas stations around here have 93)?

 

Guys we have tools now that allow us to run radical setups. I am a street racer. My compression could be MUCH higher if I wanted it to be because I use this simple tool called the Timing Tuner. Right now I am below 12.0:1 compression and I honestly think with the timing tuner I could run 13.5:1 compression with the timing reduced to like 15 to 18 on pump gas with no detonation, but for racing I could run race gas and put the timing up to 28 degree's and be fine..

The question is how radical do you want to go? My car with 13.5:1 compression and race gas would make some SERIOUS power and with reduced timing on pump gas I would still make between 530-550rwhp. Honestly I dont know why many do not do this.. I thought of this idea when FMS was building the SS, but I was afraid to be the pioneer. Maybe one day I will grow some ***** and go back and let Allan do what he really wanted to do

 

i'll have a 11:1 compression ratio with my new heads and a as yet undetermined cam(probably be in the 226-230dur. range). i'll use at least 93 octane.

 

Anyone have any before/after numbers when going to higher compression? Any idea how much is gained per 1 point of added compression?

thanks
Ben

 

what are some of the street car/ daily driver compression ratio?
is 11:1 and 11.5:1 with 92 octane fuel ok to run w/o ping ?
I know the new vettes are 11:1, but I only care about us
LS1/LS6 motors.
the guys with the above CR what spark plugs are you using ?

 

I run 11.7:1 right now and have no problems. The cam that I am running is 236/230 .601/.591 114. The only problem that I have is motor does not really like to run below 1500 rpm w/out a little lugging. Just run 93 octane in it and have not had any issues.

 

So it would be possible to run a 12:1 with a 228/228 .588/588 112 and still use 93 octane? Or could i run something higher with the use of the timing tuner?