89ProchargedROC

Sure you can....just take out maybe 1-2 degrees of TOTAL TIMING with the electromotive and on pump gas you wont have a problem

Its stated you gain 4% for every compression point so its safe to say the opposite is true also.Jim told me its much better to lower comp.than take out timing.

very true. It is better to lower compression but not in your case because you're not going to be running an enormous amount of boost. So therefore you wouldn't be taking out a lot of timing...like i said, maybe 1-2 degrees at most on the top end


8.1 is nothing,the smog motors from the 70s have comprssions like this ,Eclipse turbos run 7.8 to1 this is a 4 banger more than half the size of my motor,my friend has one,you dont notice anything,as with a Turbo Ta motor that another has transplanted in a 67 chevelle.They just get up and go.I will not run race gas on the street,to expensive,not worth it at all,at this power level,your car is a pig on gas anyway,and race gas doenst last long on the street.Im just going to let the boost do all the work

I just meant to run race gas AT THE TRACK. Then you could turn up the total timing and the boost and go A LOT FASTER

You cannot compare the effciency of different types of motors. In actuality, turbo buick V-6s can run MORE static compression than anything else because i remember reading a report that engineers came to a conclusion a V-6 has design for a turbo motor....hence why they run so well

You can do what you want but with an 8.0:1 compression....you'd be able to run A LOT of boost on pump gas which is fine if that is what you want to do. But more boost puts more strain on everything. If you had compression 8.0:1 i wouldn't be afraid to pump up the psi to about 20-23psi on pump gas

--For you application you should be getting the turbo that has the right efficiency range for your motor. What i mean is, if the turbo you are getting runs best around 15-17psi....make your compression as high as you can (with a little safety margin of maybe 0.5:1) and run pump gas. If the turbo runs best around 20psi...you get the idea

Also if memory serves me correct....dont you have like 9.4:1?

I dont think you can drastically alter your compression by a point and a half by cc the combustion chambers unless right now the are like 76cc...then maybe even a point is pushing it

Also, dont go band-aid and use thicker head gaskets. Not a smart idea. You will screw up the quench area on the motor and actually make your motor MORE PRONE TO DETONATION with LESS compression because the flame has so far to travel

just some more of my .02

TTA850

I'd drop the compression,it's proven you make more power with lower compression and more boost.

Response off idle has never been a problem for me and(thanks to a good intercooler)I can run 18-19#'s on pump gas although I usually leave it around 16.

The TE-64's sweet spot(so I've been told)is around 25-27psi.In which case he's better off with the lower compression,with 8:1 and some C16 he can wring out 28#'s at the track and cruise with pump gas and 18#'s on the street no problem.Maybe it's just me but I like to see the boost guage up there.

This I agree on,do it right.

One final thought,the Buick guys got lucky. After doing 3 3.8 turbo's I've found these motors have a poor oiling system,along with the tendancy to eat cams,blow the bottom end out(literally out the bottom),and heads with almost no meat that it's amazing they hold boost at all.

Steve

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1989 Turbo Trans Am's #124 and #850
1989 Turbo GTA,600hp 3.8L SFI TURBO
2001 Kawasaki ZX-6R
www.tta850.com

89ProchargedROC

then i guess he should drop the compression But by only milling the heads....he isn't going to drop a whole lot unless his cc size is like 64cc right now and *maybe* go up to about 72cc if that is possible with some porting

[This message has been edited by 89ProchargedROC (edited November 08, 2001).]

pontiac

i think compression ratio around 7:1 is still ok. my friend had a volvo with compression like that, T3, crazy cam (300+ degrees) and DFI. he got 300hp from rear wheels until they couldn't tied it up to dyno tight enough in order to avoid wheel spin. that car had only 2 liter engine and made high 12's with no traction.
engine worked just fine under 4000rpm, like any other volvo. after that needle of VDO meter jumped to 1.5bar (i don't know how much boost did he run). after that up to 6800rpm it was just whoo's and pop's

low compression ratio, crazy cam and lot of boost. that's recipie for nice streetable car.

-P

89ProchargedROC

like i said....you cant compare different motors like this.

They all have different effciencies that will make up for certain losses through technology

AdioSS

Sorry to bring this info back up, but, maybe it's time for a FAQ on this if there isn't one already?

Otherwise, this has been a GREAT thread with lots of info. I've been planning on some sort of power adder for my Caprice and the info here is helping me learn more and more!

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~ Cheston Phillips ~ =Impalaitis ~ = tri9_SS
'96 BBB Impala SS "ADIOSS" & '91 white Caprice 'n0n 9c1' w/L03

PROCHARGED89Z

Guido,you have to ask you father to admit you to the crazy house.That combo will be nuts,and when you turn it up with the M block,you had better start wearing depends on a daily basis.

On another note,I saw your cam specs,and my builde,.told me the cam I have know might be good enough. 220 intake 230 exhaust at .050. .510 lift on both ex and intake.Just wondering because I want this done right the first time.I was surprised to see a turbo mustang on his wall that he built the motor for.it runs in the 5.0 classes.Single turbo,347,10 inch tires,7.85 holy crap,and he told me since he switched over to single turbo he had made over 60 passes without even taking the heads off,before on the supercharger he told me(the engine builder)he had the motor apart every event and least once.

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Check out my Hompage,or the beginnings of one.355 dynoed at 400HP at 5800RPM & 410LBFT of TQ,on Motorhttp://www.procharged89z.cz28.com/index.html

B4Ctom1

hey you got the same k-member as me https://www.thirdgen.org/rides/index...ew&rideid=3980

ChillPhatCat

Manhattan WAS bought for $24!

BTW That is a monster turbo! I'm interested in what sort of Hp boost you'll be getting...

NICE!