Caveman

Maybe the guys who have done the installation (owners or installers) can chip in on this point as it's pretty fundamental to whether this is cost effective or not. I love the idea of getting a (decent) power increase that can (relatively) easily be removed if I ever wanted to sell the car. I'm not looking for highest ever power gains, just something that gives a good increase.

Cheers,

David

GabiOsz

I am having a re-build soon what is involved in lowering the CR? can this be done without adding an SC immediately? or will that adversely effect the engine?

Caveman

I'm no mechanic but it sounds a bit risky from the point of no return!? (at least without spending a shed load more money to put the compression back up. What mileage have you done?

Cheers,

David

GabiOsz

I've done 80,000 but I have pingign and run on issues so I am having the re-bulid on account of that, just wondering what I could do while I'm at it, an SC has me tempted I just can't afford to to it at the moment and if lowering the CR is not a bad thing to do then maybe it's worth doing just in case.

Caveman

I'm on 85,000 but I haven't (touch wood; which now I come to think of it may sound quite amusing to our American cousins!) had any of that. Any idea why you are having the issues? I'm a bit cautious about lowering your compression and then waiting before fitting an SC as what if you had to sell the car in a hurry; you would be screwed! Most of the posts that I have read about the TPC SC suggest no problems with running it on an untouched car. NineMeister apparently fit the TPC kit so it may be worth contacting them?

Cheers,

David

GabiOsz

I don't really understand waht lowering the compression ratio invloves, a bit of a novice on the subject, could you enlighten me?

The pinging/pinking and run-on problems seem to be down to hot spots in the cylinders, either a pitted head or carbon buildup, which causes the problem.

willisit

Lowering the compression ratio can be done in a number of ways - usually it's the pistons (size/shape) - and the headgasket thickness.

Lowering it isn't a great idea unless it's being blown/turbo'd straight away. If you want more power N/A then the compression ratio is usually raised.

95beema

Dished pistons,Thicker headgasket.

GabiOsz

Ok, sorry, pig ignorant, but is Lowering the compression a case of making the cylingers bigger or smaller essentially?

mr_bock

The TPC SC kit is designed for the stock engine and 4 to 5 lb. boost. I was told by TPC that they have a customer with 130k miles on the SC. The only time you would need to lower the compression would be if you increase boost. As with most things, once you start increasing power, the weakest link becomes a risk. I was having some pinging and misfire codes, TPC said to change to Shell Premium gas..... no problems now!!!! I love the SC.

akolodesh

I would have no issues with adding the TPC SC to a street driven car. Even though its a roots style system (less thermal efficiency than centrifugal system) I wouldn't worry about it as a street car.
My concern has always been about the TPC system in a Track/Street car. Keeping the rpms up for a significant amount of time in a roots system worries me a bit.
I wonder if axillary oil cooling would be enough to counter the potential thermal issues. I also wonder if going with lower compression would do the trick in a track car. Now about 8.5:1 compression in a 3.8L kit?
Any thoughts?

KASH '95 993

mr_bock,

What brand of gas were you running before switching to Shell? I'm currently running BP and Mobil with no issues (10,000 on the SC so far with water injection @ 7psi). The power is unbelievable. Awaiting TT wing to install air/air intercooler.

As for the TPC set-up, the Split Second digi box is also programmed to retard the timing under boost conditions to further facilitate the higher CR...

GabiOsz,

Lowering your CR without immediate force induction will result in significant power loss. Also, pistons that are designed to lower compression ratio, typically have a deeper dish (top of the piston) to allow for a greater volume at TDC (fyi, CR is the ratio of the cylinder's volume at BDC divided by the volume of the combustion chamber at TDC).

Jean

Slightly

One of the debates I have with "SC'd" friends is whether their car is faster than a 993TT.

Since we have a few RListers with SC's here, would anyone mind posting a 60-130mph timed run please on the 993TT forum? It would be great to know whether you can beat a stock 993TT. If you have a G50/20 you should be able to shift one time less maybe, and get better timings. Please read the thread
Post your acceleration figures here

Any non Sc'd 993s are of course welcome too. For more accuracy, either a video or well calibrated G-tech or similar is preferable, all you have to do is go at full throttle from 20-30 mph or so and keep redlining until you reach 130mph, in a desert road of course!

Hope to see some of you guys there.