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View Full Version : Whats the highest compression on a NA SVX

Dessertrunner
05-23-2008, 05:58 PM
I have a question what is and what do we beleive is the highest compression we can get on a NA SVX on pump fuel?
Tony
RallyBob
05-23-2008, 07:31 PM
I have a question what is and what do we beleive is the highest compression we can get on a NA SVX on pump fuel?
Tony

Compression ratio, or cylinder compression?

FWIW, when my friend Jack was having his EG33-powered 2.5RS dynoed (stock engine internally), on US-spec 93 octane (RON + MON/2 method), the engine was completely tolerant of 42 degrees of ignition timing at all engine speeds. No power was gained or lost at higher settings, but it really didn't seem to matter if he had 34 degrees, 38 degrees, or 42 degrees...it did not 'ping'.

Now, with the altered camshafts and slightly higher compression from head milling in his current engine, it can tolerate close to 50 degrees before knock sets in. But, it loses power now after 38 degrees. Naturally, the higher overlap of the 'big' cams bleeds off some combustion pressures. Timing is set substantially higher than it was previously at lower rpm levels to somewhat compensate for the overlap, and to aid starting.

That said, I believe the chamber design to be fairly efficient.

I suppose I will find out when my other friend Andrew has me build his EG33 with 12:1 compression!

Regards,
Dessertrunner
05-23-2008, 07:49 PM
Bob when you build the 12:1 engine will you get new pistons?
RallyBob
05-23-2008, 07:55 PM
Bob when you build the 12:1 engine will you get new pistons?

New pistons. New rods. Off-set ground crank hopefully too. I'm looking for some added displacement, since it's basically 'free', given I have to replace all the reciprocating parts and grind the crank anyway. I may sleeve the block in order to increase the bore for better breathing/less shrouding.

Remember this is an entirely different build from Jack's car, so we're starting from scratch, and the budget will be a bit higher.
Dessertrunner
05-23-2008, 08:46 PM
What sort of budget do you expect?
RallyBob
05-24-2008, 09:30 AM
What sort of budget do you expect?

Well, I'm not sure really, but when I threw out a number of $8500 or so, he didn't blink an eye!:D
Dessertrunner
05-24-2008, 03:28 PM
Bob are you running a oil cooler on the Jack's engine.
RallyBob
05-25-2008, 11:05 AM
Bob are you running a oil cooler on the Jack's engine.

He has a Setrab oil cooler for the engine. He also has an Accusump.
A cooler and pump for the 5mt.
A cooler and pump for the rear axle (160mm).
An external electric water pump for the engine.
A cooler for the power steering.

So I guess he has most of the systems covered?:D Racing is indeed hard on the car!