Good compression ratio for light boost or na?

 
Old 05-14-2018, 10:05 PM
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Default Good compression ratio for light boost or na?

My engine is a stock B20b bottom end and a stock GSR head. I know the gsr head is the higher compression of the two common VTEC heads to throw on there, but in not exactly certain of the CR they make together. I would guess around 10:1?

either way I'm looking to open up the engine and put in forged rods and pistons in preparation for boost down the road. But before that time I'd like to run the car na with the forged internals.

What compression ratio will allow me to run 8psi or less down the road on pump gas, but won't make the engine a total dog NA? Is stock the best middle ground? I'm I just dumb for trying to find this middle ground? Maybe I'm dumb for even wanting forged internals for 8psi or less?
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Old 05-15-2018, 02:19 AM
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Default Re: Good compression ratio for light boost or na?

Your consideration should be sleeves not compression on a forged b20 above the 400 crank.
8psi is easy on stock internals on any honda engine depending on turbo.
Its a difficult question unless you are sure on what hp youll want once you forge the engine.
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Old 05-15-2018, 03:43 AM
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Default Re: Good compression ratio for light boost or na?

B-Series calculator

You're welcome!

That will help you determine what and where. You need just supply the how.. Goals Goals Goals! Set your goals and plan your build accordingly. 10:1 compression is good, just requires a good tune. I'm running a boosted 10.5:1, so it's feasible. I've heard of a few even higher. Almost everyone will say psi means nothing as a general reference. 8psi varies from turbo to turbo. Why build it first and boost it later though? Do it all at once!
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Old 05-15-2018, 04:19 AM
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Default Re: Good compression ratio for light boost or na?

I do not plan to have it go 400 whp, but sleeves are going to be done as well but I didn't really have any question on that so I didn't mention it. I'm keeping it pretty mild, hp wise, and will definately be getting a good tune. So if that's achievable on pump gas I may stick with a somewhat higher cr like 10 or 10.5 like that. If I'm not looking to go above 350 whp is it silly for me to even be considering building the block up beyond stock?

The reason I'm not looking to do it all a once is multi faceted. Currently in California and a turbo would get me in trouble if a cop ever decided to look, but I'll be leaving here in a few months. And since the B20 ia stock, but I have a 8300 redline, I wanted to do arp rod bolts. But I figured taking the engine apart to do that seems kind of pointless if I'll be taking it all down again in a few months to do forged internals. So I want to open it just once, do the forged internals and sleeves that will prepare it for boost, but will also hold up better na under higher rpm. Then once I'm out of here I can boost it
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Old 05-15-2018, 06:24 AM
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Default Re: Good compression ratio for light boost or na?

Makes sense. From what I've read on here, 10:1 seems to be the acceptable trade-off between safety and pep out of boost.
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Old 05-15-2018, 07:37 AM
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Default Re: Good compression ratio for light boost or na?

-If your considering getting sleeved you can go up to 11.5:1 with forged internals on a 350 whp target.EDIT you can go more. But you must trust your tuner a lot.
A good example is a stock 11:1 F20C can go reliably 500 whp with a good tuner.
-If you could live with 300 to the crank(my personal preference,other may say 300 to the wheel...) i wouldnt forge it at all. Just get a mid sized turbo. Not a super torquey small one.
-If you really like the 350 to the tyre MAX idea and small budget. Id get 84.5mm, or 84mm if oval in non existent, nippon turbo pistons(they can handle 400whp...actually more than your stock sleeves will ever handle) and some cheap h-beams with arp2000.
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Old 05-15-2018, 10:26 AM
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Default Re: Good compression ratio for light boost or na?

I'm running a turbo 11:1 stock block F20B around 300whp. No issues. It's all in the tune.
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