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Old 08-16-2014, 11:55 AM   #1
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I'm going to rebuild my engine with forged internals but I don't know what is the "best" compression to choose for the pistons. I'm going to use a garret GT2860RS turbo with a sturovo manifold and 3" downpipe and exhaust, ev14 1000cc injectors, reverant ms3, FM IC. Powergoal is +300HP in a daily driver.

I'm thinking about the supertechs with wiseco rings or a complete wiseco set. The thing I read most was going for the CR 8.5's but I heard good things about higher compression turbo builds such as less oil and fuel consumption. What would the pro's and con's be? The pricedifference between the wiseco and the supertech isn't big so that should be an issue.
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Old 08-16-2014, 01:09 PM   #2
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What fuel?
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Old 08-16-2014, 01:36 PM   #3
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normal pump fuel, e85 is hard to get around here...
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Old 08-16-2014, 03:25 PM   #4
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You will need to stay around 8.5. When using pump gas you are detonation limited with regard to timing. If you go to, let's say 9.5 instead, you will not be able to use as much spark advance and will be far more likely to have detonation in your quest for the top side of 300whp. The compromised timing will mean that more of the power generating gas expansion will be going out of the exhaust ports and less will be used to push the pistons down. Different engines have different tendencies with regard to detonation and some will tolerate more compression without issue. Some are much worse and some are much better than ours.

And so you understand, it is possible to turn the boost up even higher without detonation when using 8 to 1 pistons than 8.5 to 1 pistons with the same timing.
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Old 08-16-2014, 03:29 PM   #5
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....at the expense of quite a bit of driveability
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Old 08-16-2014, 03:41 PM   #6
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You want Supertech 8.5:1 or 8.6:1 (whichever it is) forged pistons in a street car.
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Old 08-16-2014, 03:46 PM   #7
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/\ I agree. No lower than that, and no higher unless you have really good pump gas (93+)
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Old 08-17-2014, 02:37 PM   #8
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and what about the oilpump, its going to be a boundary pump but they got the shims options......dont know what they mean/do.....
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Old 08-17-2014, 03:10 PM   #9
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More shims is more better pressure. Depends on your needs. VVTeez?
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Old 08-17-2014, 03:24 PM   #10
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More shims mean more peak pressure, not more operating pressure. Operating pressure is determined by the volume coming into the engine from the pump versus the clearances within the engine that allow it to escape, and will vary by oil thickness. A race engine and a street engine will often be built with different tolerances and therefore the same oil pump will yield different operating pressures. It is unusual for an engine to operate at its relief pressure unless the oil is cold or thick for some other reason.
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Old 08-17-2014, 04:14 PM   #11
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Ok but why dont I take the one with the highest peak pressure? It seems the best way to go at no extra cost...
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Old 08-17-2014, 05:33 PM   #12
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Quote:
Originally Posted by tjeerd View Post
I'm going to rebuild my engine with forged internals but I don't know what is the "best" compression to choose for the pistons. I'm going to use a garret GT2860RS turbo with a sturovo manifold and 3" downpipe and exhaust, ev14 1000cc injectors, reverant ms3, FM IC. Powergoal is +300HP in a daily driver.

I'm thinking about the supertechs with wiseco rings or a complete wiseco set. The thing I read most was going for the CR 8.5's but I heard good things about higher compression turbo builds such as less oil and fuel consumption. What would the pro's and con's be? The pricedifference between the wiseco and the supertech isn't big so that should be an issue.
From my experience the Sturovo log manifolds will struggle past 260whp.

I use Wossner 9:1 pistons on 98 octane pump gas and 20psi. But I had to ditch the Sturovo log as it was flow limited and causing me to retard timing. His log's suit 250whp quick spooling GT2560 (max size) turbo's. My short tubular flows way better and has let me wind timing up.

Water injection will help with high power pump gas builds

Last edited by Lloyd_D; 08-17-2014 at 06:13 PM.
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Old 08-17-2014, 05:49 PM   #13
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What mani do you use now?
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Old 08-17-2014, 06:04 PM   #14
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Old 08-18-2014, 12:33 PM   #15
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Quote:
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Ok but why dont I take the one with the highest peak pressure? It seems the best way to go at no extra cost...
Why run a relief at all? Why not just pin it closed?

Because it is a safety valve designed to prevent damage and excess wear to the oil pump and crankshaft when the engine is cold and the oil is incredibly thick. It also helps to prevent seals from being blown out and tries to minimize the amount of trash being put into the engine by going through the oil filter bypass.

Again, the only time the relief is typically active is when the engine has not yet reached operating temperature unless you are using very thick oil or a high volume pump in a non-vvt application.

More pressure in the system than is needed to achieve proper lubrication robs horsepower.
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Old 08-18-2014, 01:22 PM   #16
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Quote:
Originally Posted by sixshooter View Post
Why run a relief at all? Why not just pin it closed?

Because it is a safety valve designed to prevent damage and excess wear to the oil pump and crankshaft when the engine is cold and the oil is incredibly thick. It also helps to prevent seals from being blown out and tries to minimize the amount of trash being put into the engine by going through the oil filter bypass.

Again, the only time the relief is typically active is when the engine has not yet reached operating temperature unless you are using very thick oil or a high volume pump in a non-vvt application.

More pressure in the system than is needed to achieve proper lubrication robs horsepower.
now I get it, so for normal use, no vvt, you don't need the shimms, heavy duty use, use shimms but you will get more wear.


Another question: supertech or wiseco?
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Old 08-18-2014, 01:38 PM   #17
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Supertech if it is a street car, beter metal alloys. You can search for the exact differences.
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