How much do you have to lower the compression ratio on a TT

[Andreas]

How much do you have to lower the compression ratio when converting a GTS to TT?

[RedGTS]

Opinions will vary, and they will vary in part based on what you're trying to do and the rest of your setup, but I would say at least to 9.0:1.

[BigCarrot]

I know at least one guy that I wouldn't ask!














I'm trying not to be an asshole anymore, but that was way to easy to resist!

[JID]

depends on your goals... if you are only running 5psi of boost, then BOOST the CR to 10.5:1 !

JD

[ROLLMODEL]

Originally Posted by BigCarrot

I know at least one guy that I wouldn't ask!














I'm trying not to be an asshole anymore, but that was way to easy to resist!

Alright, I'm going to have to say that was a 'gimme'.

[Tanked]

Currently most everyone uses 9:1.


However, in my last turbo car (92 Talon Tsi AWD)I was running 8:1 w/ 15psi of boost on pump gas...no water or meth.

[CHAD]

It really does depend on how hard you are going to push it. There is no magic compression ratio, stroke length, bore size, chamber volume, intake runner cc, etc. It ALL depends on the intended purpose.

I will say it can all be done with a piston swap, however. If you are going beyond the stock reciprocating assembly, you'll need all new parts and a tuner for guidance anyway.

[Doug Levin Motorsports]

... the quality of fuel, spark advance, street or strip, amount of boost, intercooler, play major roles when determining your static CR.

Don't be in such a hurry to knock too much compression out of a street driven LOW boosted vehicle. You'll end up with slow-responsive low/mid range power, however, top end power will be adequate. Track driven cars can utilize a lower CR because the power is usually set at full tilt.

Increased octane, along with a denser air charge allow for a slightly higher static CR with advanced timing.

Running a 9:1 compression ratio is usually "a happy medium" for street cars.

Consider running lower boost with more timing advance, rather than higher boost with less timing advance.

Hope this helps ...
Doug

[MacedoMS]

The above opinions are spot on, very much depends on the vehicle and it's purpose. Some Europeon vehicles run low boost and a high CR, but these units are pretty reliable and very well tuned. Fuelman's 99 Camaro runs a 10.5:1 CR @ 5 lbs. of boost non-intercooled and is relatively a daily driver. The secret ingredient is the tuning!

[JZ 97 SS 1500]

On most of our turbo engines we build we go for 8.5cr. Leaves you plenty of room for error and also you can crank the boost up a good bit with pump gas. With a big cube motor, low end suffers very little. An 8.0cr 488ci motor will still have tons of power...hehe