mr slow

I have an 11.4 to 1 408 and I am wanting to put a blower on it. How do you think a D1SC with a stock keyed balancer around 10-12 psi would do? I don't want to run meth, I would like to stick with 93.

cmiller8006

Probably not going to happen

TheCartel

What's the cc of your current heads? Head swap to drop cr? More info man

mr slow

The heads are 68cc TEA stage 1, I'm running an .051 cometic gasket, and wiesco -3cc flat tops. At a 4.030 bore and 4.000in stroke that puts it close to 11.4 to 1. But I am just curious if it's possible, it doesn't have to be 10-12psi maybe just 8psi?

mr slow

I know I could open up the chambers some I think around 76cc?? Is about as much as they take ls3 heads. But I was just seeing if it was possible without having to do that or if anyone has done it. If not oh well

ajrothm

Not without a sh*t ton of meth... Or E85.

You'd have to pull so much timing out of that thing on straight 93 oct it would be a dog...and probably still yack head gaskets.

blown81bu

too high compression= broken pistons,smashed mains,detonation etc
thats why i run 9.5

mr slow

Okay that's what I wanted to know. I already knew the answer I just wanted to hear it that it's a bad idea lol I will just stick N/A for now and keep tweaking it and try to get more power out of it.

Patches

I have had multiple conversations with A&A, ECS and other top tuners and they all agree that level of compression is not a problem. In fact, they tell me the car will perform better off boost and that I can I can use less boost to generate the same amount of power as a lower compression setup.

cmiller8006

And as stated prior, you will need **** tons of meth or E85.

a/c man

Get a head porter to open up the combustion chambers up. Or you can change heads.

MMA FIGHTER2

Just run nitrous and be done with it

Pekka_Perkeles

That's offtopic.

Meanwhile: a stock 11.0:1 LS7 is just fine with some boost.

Or is it?

tlove32

I'm at 11.0:1 CR and 9-10psi of boost......but I run meth

Shoaf85

It will work but not on 93 IMO. Unless you run really low boost, however an E85 setup would be ideal and make great power.

MVP'S ZO6

What I'm about to say isn't calculated to the T nor is it intended to be an end all be all post but rather a guideline type of post with a little more than the typical internet belief of high compression and boost don't work and or you can't do it because you will blow your engine up.

The truth is, you can blow your engine up with a lot less if it isn't dialed in right. I don't think anyone will argue that.

Anyway,

The C6Z is 11 : 1 compression. They live fine with mild boost. (I consider 10-12 psi mild boost). One thing a lot of enthusiast tend to over look when deciding on static compression ratio and boost levels is What the effective compression Ratio of your engine will be. Yes EFFECTIVE compression ratio and STATIC compression Ratio are two totally different things. Effective compression ratio is dictated by Boost levels and Static compression Ratio and Atmospheric Pressure. STATIC is just what it sounds like. It's effected by engine component combo selection and it stays the same or STATIC.

With your given combo with an 11.4 : 1 static compression ratio @ 10 PSI boost, you should be yielding about 19.1 effective compression ratio. @ 12 PSI, your effective compression ratio should be about 20.7

To put that in perspective, the effective compression ratio of a C6Z @ 12 psi boost is about 19.98. That's less than 1 point difference in effective compression ratio between a typical C6Z and your combo. These are just ball park numbers, but it gives you an idea.

Another thing I'd like to point out is, my car has a static compression ratio of 9.5 : 1 and the current combo produces about 22 psi boost or so. That means my effective compression ratio is about 23.7 (Note, this is a full 3 points higher than what your effective compression ratio would be) I don't have an exotic combo, just an iron block with forged internals and aftermarket heads. Keep in mind I was actually able to run that amount of boost without any methanol at all as long as the timing was kept reasonable. (With that, I've also learned that what I thought was a reasonable amount of timing without methanol was actually a lot less than what my combo would take). The amount of timing you can add is definitely combo dependent. Each engine combo is different.

Another advantage to having a higher static compression ratio is that when the car is off boost, or in the lower boost region; It will generally have better performance. The power curve will be less peaky. I'd think this is a desirable characteristic in a street car where you may not always be in the upper part of the engine power band. The car will probably be more fun to drive too.

Bottom line, I'm with the guys at A&A and ECS, I wouldn't have a problem at all running 12 psi boost with a well built engine that yields a static compression of 11.4 : 1

Ps. If you do it, pin your balancer. It's cheap and easy to do.

mr slow

I appreciate the info and this is exactly what I was thinking. Don't you need to know my cam specs in order to figure out the effective ratio due to reversion from valve overlap and loosing compression when both valves are open?

But I agree with you about everything you said, this is why I ask. If a 9.0:1 motor on 22psi can survive why can't a 11.4:1 motor with 10-12 but like you said have better off boost characteristics because you aren't pulling all the power out of it by dropping the compression way down. Oh and I had a keyway cut into my balancer so I am good there.

mr slow

Plus if you are running a PD blower you shouldn't have to spin it as hard to make the same power(or whatever your goals are)as the other guys therefore reducing heat soak, which means power. That would ring true with a centri blower too whether it be a procharger/vortech or whatever. Spin it easier which makes it easier for the IC to cool the air charge thus resulting in a cooler air charge and more power right? Plus the equipment(the superchargers)last longer because you are not running them right at their limits.

MVP'S ZO6

Absolutely! My numbers were more of a ball park guesstimate and wernt meant to be set in stone or to be exact.

I think you got the point though. Mild compression and high boost live so high compression and mild boost as well and it will be more fun to drive. :-)

Frans96ss

High compression and boost go great with each other. just have to make sure your tune is spot on. Doing that on straight pump gas i doubt it but with meth it can be done. I have done it plenty of times and it makes GREAT power.