I need you guys advise.

My LS/Vtec set up:

JE pistons Eagle rods new bearings and seals, and supertech springs, retainers and valves. I also have a cometic .030 headgasket and Web cams. My problem is I was building an all motor setup, but with my combo I didn't get the compression ratio I was hopping for, my comp ratio is about 11.3 to 1. If I change the head gasket, am I ok to boost, or do I need to change the pistons. I know its all in the tuning, but how safe would it be. This is also gonna be on 93 Octane. Thanks

 

comon guy someone has to have input.

 

i would personally change the pistons, but high compression is not necessarily a bad thing for a street car. on 93 octane, i would keep things simple and run lower psi levels to avoid detonation. x amount of psi will depend on the turbo, but at 11.3:1 compression and 93 octane, you are close to limits of forced induction. with a competent tuner, im sure he could make it safe by taking enough timing out. bad thing about that is it will raise your egt's a bit. i would just swap the pistons and get some 9:1-10:1

 

I've said this before and will say it again...maybe one day people will listen to me

You can run as high of compression as you want with a turbo setup <u>as long as</u> you have a high enough octane fuel to support it (and your power goals). My example of such an ocurrence would be diesel trucks. They run a compression in the 11-15:1 range and are turboed. Diesel fuel just has a much higher "octane" rating than does gasoline.

If you have access to something like E85 in your area, you could safely make well into the 400whp range with your current compression. I'm planning on a 9.8:1 with my new setup on E85 and still shooting for 450whp (on the stock sleeves).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Schister66 &raquo;</TD></TR><TR><TD CLASS="quote">I've said this before and will say it again...maybe one day people will listen to me

You can run as high of compression as you want with a turbo setup <u>as long as</u> you have a high enough octane fuel to support it (and your power goals). My example of such an ocurrence would be diesel trucks. They run a compression in the 11-15:1 range and are turboed. Diesel fuel just has a much higher "octane" rating than does gasoline.

If you have access to something like E85 in your area, you could safely make well into the 400whp range with your current compression. I'm planning on a 9.8:1 with my new setup on E85 and still shooting for 450whp (on the stock sleeves). </TD></TR></TABLE>

well said, however; he stated he will be using 93 octane.

 

even with higher octane, you'll hit a point of diminishing returns. The turbo will spool faster and you can have a fatter midrange....but......you're still trying to coax power from a smaller volume. And its less stable

when low compression/high boost and high compression/lower boost make the same power, the Low Compression/high boost has a larger volume to make it from.

you want 8 AA batteries in series making 12V or one car battery doing the same job?

 

With the thicker head gasket, you lose effective quench, vs changing the pistons, you shouldn't.
In some cases, the loss of quench increases the propensity of detonation, and thereby decreases octane tolerance/power production despite the lower static compression (endyn)
The b16 head doesn't have much quench though. The gsr head does.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Schister66 &raquo;</TD></TR><TR><TD CLASS="quote">My example of such an ocurrence would be diesel trucks. They run a compression in the 11-15:1 range and are turboed. Diesel fuel just has a much higher "octane" rating than does gasoline.
</TD></TR></TABLE>

I've never heard of a diesel having a compression ratio anywhere near 11:1. ? Way higher. But diesel is a totally different game, not really comparable to a gas motor. Esp considering boost capacity being almost limitless, there are guys hitting Insane amounts of boost with sequential turbos on those dodge 5.9 cummins trucks. 1400+ft lbs..

 

11:1 was a complete guess....but its significantly higher than what the OP is planning. I realize that diesel is a totally different game, but it does reiterate my point.

 

So if I decide to change the headgasket to a thicker one, What brand would you suggest? And what thickness?

 

Cometic .080" headgasket should bring your down to 9.9:1 which is A LOT safer.

 

I was told cometic only goes up to .074"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Schister66 &raquo;</TD></TR><TR><TD CLASS="quote">I've said this before and will say it again...maybe one day people will listen to me

You can run as high of compression as you want with a turbo setup <u>as long as</u> you have a high enough octane fuel to support it (and your power goals). My example of such an ocurrence would be diesel trucks. They run a compression in the 11-15:1 range and are turboed. Diesel fuel just has a much higher "octane" rating than does gasoline.

If you have access to something like E85 in your area, you could safely make well into the 400whp range with your current compression. I'm planning on a 9.8:1 with my new setup on E85 and still shooting for 450whp (on the stock sleeves). </TD></TR></TABLE>

14:1-20:1~ is about the norm give or take a little bit on the bottom and top
Cetane is used for rating diesel fuels "ignition lag"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quicksilver1689 &raquo;</TD></TR><TR><TD CLASS="quote">

14:1-20:1~ is about the norm give or take a little bit on the bottom and top
Cetane is used for rating diesel fuels "ignition lag"</TD></TR></TABLE>

I researched the compression after my post, but was too lazy at the time to change it. I didnt know the second part however...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">Cometic .080" headgasket should bring your down to 9.9:1 which is A LOT safer.</TD></TR></TABLE>
So a headgasket alone can lower it THAT much? because ive got no idea what my compression is but my head was machined .02-.04 on a SIR (10.6cr) so any idea what mine would be?
and all id have to do is get that headgasket and it would make it alright?

 

i would just change the pistons, its easy to do now.

diesel is completely different, its like compairing apples to oranges. diesel injects the fuel at the top of the compression stroke, they kinda use detonation to run the motor. diesel fuel also has a really low octane like 25 or somthing.

 

if you will be running pump gas 91-93 octane i say DONT do it!

 

What are your power goals, and what type of gas would you want to run? What are you using to tune the car and what type of cams are you running in your car? What kind of power did you make on just the motor in an all-motor setting? how much timing are you running now?

 

It can be done. You need to have the appropriate turbo setup to get the most out of it safely.. If your running 93 pump, then you'll be limited to how much boost you can get away with depending on cam selection, turbo selection, exhaust manifold selection<U></U>, but with all the right parts and an <U>EXPERIENCED TUNER</U> you should be able to make good power with your setup reliably on pump. If you run race gas, there is no issue. We made over 750 on our shop car with 11.5:1 compression and 28 PSi of boost. We were using race gas though of course. I've done a B17 GSR with cast OEM CTR pistons and stock rods on 93, he made over 350HP @ 12 PSI.

If you want some info on good turbo and cam selection for your setup let me know I'd be glad to make some suggestions.

 

b17 with CTR pistons is like 12.5:1 thats crazy that you could tune that on 93 AND make 350hp, very impressive...

 

He had the right cams, manifold and turbo for the setup..

 

As he said, it's easy when you knoe what your doing. If you don't pay some that does.