What compression ratio should I go with?

[turbovanman²]

The TIII has 8.5:1 doesn't it, should I aim for the same?

[86Shelby]

12:1 Utilize low boost for much higher than average psi/whp gains. ;)

I'd aim for something similar to stock compression. Though I wouldn't be afraid of a few points higher.

[turbovanman²]

So what is a stock TIII?

[Anonymous_User]

http://www.badassmopars.150m.com/RT.html

scroll down.

Says 7.8:1

Reliable information? Who knows.

[turbovanman²]

http://www.badassmopars.150m.com/RT.html

scroll down.

Says 7.8:1

Reliable information? Who knows.

Thanks, I thought it was alot higher, guess I'll aim for 8:1 unless anyone else has any other input?

[GLHNSLHT2]

maybe if you shot for 6.0:1 you won't blow it up Simon :) Sorry have to bust your chops

[88_pacifica]

Simon, what are your goals long term and do you want to run high boost-low compression, or low boost-high compression? The lower the compression, the more "tame" it is and "safe" obviously(you know that), but the better the turbo has to be(flow capacity). :D

[turbovanman²]

Well its a DD foremost and it would be nice to scoot along without alot of boost, if you know what I mean. I have a nice turbo, stage III wheel, 50 trim, .63 housing and a heavy van. I see some of the Neon hybrids and the 10 sec hybrids are around 8.5:1 thats why I am confused.

[88_pacifica]

Well its a DD foremost and it would be nice to scoot along without alot of boost, if you know what I mean. I have a nice turbo, stage III wheel, 50 trim, .63 housing and a heavy van. I see some of the Neon hybrids and the 10 sec hybrids are around 8.5:1 thats why I am confused.

Well, IIRC you have the auto trans which I'm sure, since you just rebuilt, you're going to keep. Now, I won't lie to you all, I'm not a TD authority by any means, but I'll give you the basics I've learned with my GN turbo experience. Those were very heavy, automatic trans cars, so IMO you focus on a lower compression, but a larger turbo/air-charge. But, those had cast heads, not aluminum, so you had to err on the "low side" because of heat/detonation. My GN is stock and stock compression was 8.5/1 OEM. Now, I would say that you would keep it there or a little lower because it will allow a lower octane gas in non-boost conditions. The aluminum head will shed heat(save gaskets) and if your not running alky you can boost away. Ken Duttweilers 1700 HP Gn had over 30#'s of boost, but low compression. It's much easier to change a piston than a head/block. People focus on boost too much IMO. How often in a true DD are we in boost? maybe 10-15% of the time. Gear it towards the DD side and CAPABLE of the high boost side. It's just like a cam. Go less than you think you should... just my .02. :)

[turbovanman²]

Thanks I love boost but boost uses fuel, if I can stay out of boost then I can up my fuel economy which I need, lol!

I'll shoot for 8.5:1 :thumb:

[88_pacifica]

Agreed, your absolutely right. Just be super careful not to get the "urge" to push it. I've seen an a$$load of pistons with holes in them! :D The secret is finding the happy medium. Most of the GN guys are looking for tq and not gas mileage.. :thumb:

[turbovanman²]

Agreed, your absolutely right. Just be super careful not to get the "urge" to push it. I've seen an a$$load of pistons with holes in them! :D The secret is finding the happy medium. Most of the GN guys are looking for tq and not gas mileage.. :thumb:

I am looking for both but with the superior TIII head, I will find both.

[88_pacifica]

I am looking for both but with the superior TIII head, I will find both.

Well, don't let it go to your "head" that the T3 head is "the most superior" either though... After all, it is just a "factory-style" head that has it's own bag of "weaknesses/problems." You already know all that though, so this should be a moot point. The grass ALWAYS looks greener...!! :D :thumb:

[turbovanman²]

Well, don't let it go to your "head" that the T3 head is "the most superior" either though... After all, it is just a "factory-style" head that has it's own bag of "weaknesses/problems." You already know all that though, so this should be a moot point. The grass ALWAYS looks greener...!! :D :thumb:

I don't mean that, I mean as in over 8 valve. It flow, chamber design etc are years ahead of our 8 valve stuff, :D

[88_pacifica]

very true... you've been around the block too, so you know what's up... I "concur" with your philosophy on that... :D :thumb:

[turbovanman²]

very true... you've been around the block too, so you know what's up... I "concur" with your philosophy on that... :D :thumb:

I've also broken a few blocks, :(

[mpgmike]

You might be surprised how much boost you can safely run with the chamber mods discussed in that other thread, Simon. The higher compression will be more forgiving than you might expect.

Mike

[turbovanman²]

I am going to stick with around 8.5:1, that should be more than enough, :nod:

[TurboJerry]

Stock compression ratio is 8.1:1......... And this *is* accurate.

[Speedeuphoria]

considering that you are comming from what?7.8:1CR? and an 8valve
Your going to spool 50trim like a mitsu:nod:
And hey if you need more or the turbo doesnt work out
Holset and call it a day

[turbovanman²]

considering that you are comming from what?7.8:1CR? and an 8valve
Your going to spool 50trim like a mitsu:nod:
And hey if you need more or the turbo doesnt work out
Holset and call it a day


Thats the plan, the stage III turbine will help alot, I just hope the turbo isn't badly damaged, the turbine wheel took a hit from the valve debris, :mecry:

[DodgeZ]

I like 12:1 always seem to get good power with that combo.

[turbovanman²]

I like 12:1 always seem to get good power with that combo.

Yeah, Ok Kevin, :ban: :lol:

[DodgeZ]

Yeah, Ok Kevin, :ban: :lol:

oh sorry, free bump.

[88_pacifica]

Yeah, Ok Kevin, :ban: :lol:

Now wait a sec... he's on a roll this week! :D :thumb:

[BadAssPerformance]

13.5:1 anything after that is diminishing returns ;)