FI and Piston compression
10-20-2005, 06:57 PM
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FI and Piston compression
I am going to get a built engine. My goals are 500 whp. Would it be a problem to get 9.5 or 10 forged pistons and forged rods. What if i Cryo treated them would that help? I just don't want to loose low end torque. I know most people go with 8.6 or so but if the rods will handle it...
10-20-2005, 07:20 PM
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Originally Posted by beastie
I am going to get a built engine. My goals are 500 whp. Would it be a problem to get 9.5 or 10 forged pistons and forged rods. What if i Cryo treated them would that help? I just don't want to loose low end torque. I know most people go with 8.6 or so but if the rods will handle it...
10-20-2005, 07:21 PM
#3
nobody has done a built motor with the ST yet, be careful in choosing your compression, once you go sub 10:1 the turbo is gonna make less power than you are making right now. i brought this up a while back and some seem to think the turbo would need to be upgraded if going with a built low CR motor. APS says the turbo will flow enough for 650, but who knows since they wont release the turbo specs. id hate for you to spend that much money and only be able to get 50-75 more hp.
10-20-2005, 07:24 PM
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Originally Posted by tig488
nobody has done a built motor with the ST yet, be careful in choosing your compression, once you go sub 10:1 the turbo is gonna make less power than you are making right now. i brought this up a while back and some seem to think the turbo would need to be upgraded if going with a built low CR motor. APS says the turbo will flow enough for 650, but who knows since they wont release the turbo specs. id hate for you to spend that much money and only be able to get 50-75 more hp.
The difference due to compression is minimal..we're talking under 10whp between 10.3:1 and 9.5:1 and another 10whp going to 8.6:1.
10-20-2005, 07:26 PM
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Originally Posted by tig488
nobody has done a built motor with the ST yet, be careful in choosing your compression, once you go sub 10:1 the turbo is gonna make less power than you are making right now. i brought this up a while back and some seem to think the turbo would need to be upgraded if going with a built low CR motor. APS says the turbo will flow enough for 650, but who knows since they wont release the turbo specs. id hate for you to spend that much money and only be able to get 50-75 more hp.
10-20-2005, 07:51 PM
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I would not be so quick to jump on the stock block making 500 whp bandwagon. Yes it can do it - this does not mean it's ideal or that it will last
CR wise, go for something in the 9.0 range and you'll be good to go
CR wise, go for something in the 9.0 range and you'll be good to go
10-20-2005, 08:04 PM
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Originally Posted by Z1 Performance
I would not be so quick to jump on the stock block making 500 whp bandwagon. Yes it can do it - this does not mean it's ideal or that it will last
CR wise, go for something in the 9.0 range and you'll be good to go
CR wise, go for something in the 9.0 range and you'll be good to go
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10-20-2005, 08:27 PM
#8
Originally Posted by BriGuyMax
The difference due to compression is minimal..we're talking under 10whp between 10.3:1 and 9.5:1 and another 10whp going to 8.6:1.
im not saying stick with the stock block, not at all, i just said be careful in choosing a CR.
Last edited by tig488; 10-20-2005 at 08:30 PM.
10-20-2005, 09:31 PM
#9
I have similar goals(550-700hp) but plan on mixing race gas if I have to.
If you're using 91 octane, 9.5:1 should be more than enough reduction in compression for 500hp. The quality of any race piston is far superior & should last a lot longer than the stock pistons & rings. Any forged H beam rod can handle quite a beating and tend to be "overkill" but that's always a good thing.
I thermal barrier coated my 10.0 CP pistons. Well see how they do once I get a stupid crank sprocket(back order
).
If you're using 91 octane, 9.5:1 should be more than enough reduction in compression for 500hp. The quality of any race piston is far superior & should last a lot longer than the stock pistons & rings. Any forged H beam rod can handle quite a beating and tend to be "overkill" but that's always a good thing.
I thermal barrier coated my 10.0 CP pistons. Well see how they do once I get a stupid crank sprocket(back order
).
10-20-2005, 09:55 PM
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Originally Posted by Z1 Performance
I would not be so quick to jump on the stock block making 500 whp bandwagon. Yes it can do it - this does not mean it's ideal or that it will last
CR wise, go for something in the 9.0 range and you'll be good to go
CR wise, go for something in the 9.0 range and you'll be good to go
So we need resleeved blocks to be guaranteed reliability over 500whp??
I think you're confusing BLOCK with MOTOR.
10-20-2005, 10:02 PM
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Originally Posted by tig488
so thats an additional 2psi he gonna need to make the same power, and thats just to get back to baseline. and then he wants another 125hp, thats roughly 10-12 more psi. now youre talking about running a turbo at roughly 25psi, thats a lot for that small of a turbo and without knowing compressor maps for that turbo its hard to know whats gonna happen, it could be at the edge of its efficiency range already, who knows. dont think that you can just turn up the boost on the turbo that nobody knows anything about. its a lot easier just to up the boost on a TT.
im not saying stick with the stock block, not at all, i just said be careful in choosing a CR.
im not saying stick with the stock block, not at all, i just said be careful in choosing a CR.
Since when does 2psi only make 20whp on a VQ35?? Are you kidding?
And 10-12 psi for 125hp? What have you been smoking and where can I get it?
My baseline dyno was 243whp I now have nearly 200whp more on only 9lbs of boost. That's over 20whp per pound of boost. And my setup doesn't even breath that well with a small diameter borla TD exhaust, stock plenum and stock cams.
I put down 430whp on 9psi with an APS kit on a stock motor. A built motor Z (8.6:1 compression) with the same APS kit @ 9psi made 450whp with the same exhaust, and JWT cams. Take the cams away and he's about 10whp behind me. 10whp is NOTHING.
You are far far far overestimating how much of a difference a drop in compression ratio makes power wise. It's nowhere near what you seem to think. The advantages far outweight the slight power loss per pound of boost.
Futhermore with lower compression, you can advance timing far more than high compression so the power can be made back with timing advance alone.
Last edited by BriGuyMax; 10-20-2005 at 10:08 PM.
10-21-2005, 12:53 AM
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Originally Posted by BriGuyMax
Since when does 2psi only make 20whp on a VQ35?? Are you kidding?
And 10-12 psi for 125hp? What have you been smoking and where can I get it?
My baseline dyno was 243whp I now have nearly 200whp more on only 9lbs of boost. That's over 20whp per pound of boost. And my setup doesn't even breath that well with a small diameter borla TD exhaust, stock plenum and stock cams.
I put down 430whp on 9psi with an APS kit on a stock motor. A built motor Z (8.6:1 compression) with the same APS kit @ 9psi made 450whp with the same exhaust, and JWT cams. Take the cams away and he's about 10whp behind me. 10whp is NOTHING.
You are far far far overestimating how much of a difference a drop in compression ratio makes power wise. It's nowhere near what you seem to think. The advantages far outweight the slight power loss per pound of boost.
Futhermore with lower compression, you can advance timing far more than high compression so the power can be made back with timing advance alone.
And 10-12 psi for 125hp? What have you been smoking and where can I get it?
My baseline dyno was 243whp I now have nearly 200whp more on only 9lbs of boost. That's over 20whp per pound of boost. And my setup doesn't even breath that well with a small diameter borla TD exhaust, stock plenum and stock cams.
I put down 430whp on 9psi with an APS kit on a stock motor. A built motor Z (8.6:1 compression) with the same APS kit @ 9psi made 450whp with the same exhaust, and JWT cams. Take the cams away and he's about 10whp behind me. 10whp is NOTHING.
You are far far far overestimating how much of a difference a drop in compression ratio makes power wise. It's nowhere near what you seem to think. The advantages far outweight the slight power loss per pound of boost.
Futhermore with lower compression, you can advance timing far more than high compression so the power can be made back with timing advance alone.
Last edited by WA2GOOD; 10-21-2005 at 01:42 AM.
10-21-2005, 01:30 AM
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Originally Posted by BriGuyMax
Since when does 2psi only make 20whp on a VQ35?? Are you kidding?
And 10-12 psi for 125hp? What have you been smoking and where can I get it?
My baseline dyno was 243whp I now have nearly 200whp more on only 9lbs of boost. That's over 20whp per pound of boost. And my setup doesn't even breath that well with a small diameter borla TD exhaust, stock plenum and stock cams.
I put down 430whp on 9psi with an APS kit on a stock motor. A built motor Z (8.6:1 compression) with the same APS kit @ 9psi made 450whp with the same exhaust, and JWT cams. Take the cams away and he's about 10whp behind me. 10whp is NOTHING.
You are far far far overestimating how much of a difference a drop in compression ratio makes power wise. It's nowhere near what you seem to think. The advantages far outweight the slight power loss per pound of boost.
Futhermore with lower compression, you can advance timing far more than high compression so the power can be made back with timing advance alone.
And 10-12 psi for 125hp? What have you been smoking and where can I get it?
My baseline dyno was 243whp I now have nearly 200whp more on only 9lbs of boost. That's over 20whp per pound of boost. And my setup doesn't even breath that well with a small diameter borla TD exhaust, stock plenum and stock cams.
I put down 430whp on 9psi with an APS kit on a stock motor. A built motor Z (8.6:1 compression) with the same APS kit @ 9psi made 450whp with the same exhaust, and JWT cams. Take the cams away and he's about 10whp behind me. 10whp is NOTHING.
You are far far far overestimating how much of a difference a drop in compression ratio makes power wise. It's nowhere near what you seem to think. The advantages far outweight the slight power loss per pound of boost.
Futhermore with lower compression, you can advance timing far more than high compression so the power can be made back with timing advance alone.
I agree to an extent but you would need to make sure the turbo was still in its efficiency range. A turbo running out of that island isn't going to make as much power per PSI as it did while in it. WIthout a compressor map its hard to say what its doing now and what it would do by going any higher.
10-21-2005, 04:27 AM
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Originally Posted by Z1 Performance
I would not be so quick to jump on the stock block making 500 whp bandwagon. Yes it can do it - this does not mean it's ideal or that it will last
CR wise, go for something in the 9.0 range and you'll be good to go
CR wise, go for something in the 9.0 range and you'll be good to go
10-21-2005, 04:31 AM
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when someone says a stock block can handle 500 whp, most people will take that to mean an internally stock short block. I think (hope) you meant to say that for 500 whp, you need a built motor with forged pistons and rods.
Sleeves? I would not even bother touching the sleeves unless you are planning on boring the block - otherwise I would leave them alone
Sleeves? I would not even bother touching the sleeves unless you are planning on boring the block - otherwise I would leave them alone
10-21-2005, 08:30 AM
#17
regardless of what few high results have occured, theoretically speaking 1psi equals roughly a 10-15 hp gain. some cars respond different, ive had the vortech and my best results were about a 12hp gain per psi, now i have the single and the gains are about the same.
anyway, i wasnt trying to get in a debate about what gains are there, my point was stated in my initial post, the turbo probably isnt gonna flow enough cfm to provide a low CR engine the size of ours with gains worthy of a built motor. it more than likely will need to be upgraded.
anyway, i wasnt trying to get in a debate about what gains are there, my point was stated in my initial post, the turbo probably isnt gonna flow enough cfm to provide a low CR engine the size of ours with gains worthy of a built motor. it more than likely will need to be upgraded.
10-21-2005, 09:14 AM
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Iam stock internals, 525hp 11.0@125 for over 6 months, going to the track at least 3 times a month. Beating the crap out of it with no problems. Last night we took another 350z we built and it whent 11.14@121 tottay stock internals.
Yes stock engines can handle 500+ if it's tuned correctly.
Yes stock engines can handle 500+ if it's tuned correctly.
10-21-2005, 09:53 AM
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Originally Posted by fito
Yes stock engines can handle 500+ if it's tuned correctly.
If I were to ever consider going into my motor, at most I'd change out the pistons in exchange for ones with thicker ring lands & head and main studs for better clamping. Unless I planned on running 7500 RPM, rods in my opinion, aren't really necessary. Maybe just a shot peen and cryo temper process for them.
10-21-2005, 12:00 PM
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Originally Posted by WA2GOOD
Although you put it out there a little harsh (could have been nicer, LOL) I agree with you AGAIN on this, haha! Very abrasively put, but I do, once again agree with your statement,everything except the cams on the built motor making 30whp. I have never seen just cams add "30whp" on a built TT motor. But for the most part you are correct.