Forced Induction Superchargers | Turbochargers | Intercoolers

9.3 Compression?

Old Mar 22, 2006 | 04:05 PM
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Default 9.3 Compression?

think that is too high for a turbo set up? running no more than 15psi. and it is completly forged...rods, crank and pistions. will be running stock 6l heads and zo6 cam. let me know what you guys think
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Old Mar 22, 2006 | 04:23 PM
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Why not lower? What size cubes?
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Old Mar 22, 2006 | 04:32 PM
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stock cubes. its one that w2w has made up and i cant get them to change the pistons at least not yet. waiting to hear back from them. they its callies crank compstar ronds and mahle pistons. compression would be around 9.3-1. this way i wouldnt have to worry about the bottom end anymore. wanting to see what everybody thought about that compression. frcefed98 runs 9.1.
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Old Mar 22, 2006 | 04:44 PM
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With a VERY low compression (8.5?) on stock cubes (forged), I was told to expect reaching only 700 rwhp or so on pump... I really would like some input on your question so I can start buying parts already for my car...
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Old Mar 22, 2006 | 04:46 PM
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some body will chime in eventually with a good answer. i need to know asap.
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Old Mar 22, 2006 | 04:56 PM
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Well its not ideal having that much compression at all, I really like 8.5:1, my current motor is in the 9's but I am planning to replace the pistons and get myself around 8.0:1 this year.

Also, I don't think 8.5 should be considered "very low" for a F/I vehicle, it seems like a good solid number to run at.
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Old Mar 22, 2006 | 05:00 PM
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so really 9.3 is just too high? especially for 15psi?
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Old Mar 22, 2006 | 05:04 PM
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9.3 is good.. Are they using stock pistons.. and 6.0 heads?
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Old Mar 22, 2006 | 05:06 PM
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mahle pistons and stock heads. its in the sponsor sale section. callies crank, callies rods and mahle rings. and with 6l heads kevin said it would be around 9.3 to 1. so can i make it to 15psi on pump gas or not.
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Old Mar 22, 2006 | 05:08 PM
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Kaos, you're gonna get some answers. So, please don't mind if I start pm'ing you a bit, alright?
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Old Mar 22, 2006 | 05:11 PM
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Nothing wrong with 9.3:1 so long as you ease into the boost levels while keeping an eye on the O2's and KR. Utilize a dyno with a wideband O2 if possible. Once you find the limit of the psi on pump gas you could always adjust it a pound lower to be on the safe side. Then repeat the process with some high octane fuel or methanol injection for the track setup. I have seen folks with 9.5:1 run 26-28 lbs using a progressive methanol setup and pump gas, but keep in mind that this was done with an EXCELLENT intercooler and ignition as well as a turbo that was properly sized for the C.I.D. Hope this helps.

Jim C.

PS-Very good quench is part of the key to getting away with those compression ratios with a turbo.
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Old Mar 22, 2006 | 05:18 PM
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I run 9.4CR at 700 rwhp on pump gas at 12 psi.
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Old Mar 22, 2006 | 05:21 PM
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It'll be fine for your duties. You aren't shooting for 700+ RWHP.
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Old Mar 22, 2006 | 05:21 PM
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For the price of that 347, do it! 9.3:1 will be fine.
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Old Mar 22, 2006 | 05:32 PM
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Originally Posted by Tiago
I run 9.4CR at 700 rwhp on pump gas at 12 psi.
Cubes?
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Old Mar 22, 2006 | 05:52 PM
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I'm sure you ran past them the boost level? Just make sure that piston/rings is made for the boost. You could also run a different Cam that will bring down the DCR.
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Old Mar 22, 2006 | 09:30 PM
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15psi.. go for it. Run ARP head studs too.
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Old Mar 22, 2006 | 09:59 PM
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You'd be fine on 9.3 and a great tune at the power levels you want to run, head stud it like PSJ said.

My 9.1 is more like 8.1 due to us being up here a mile above sea level
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Old Mar 22, 2006 | 10:48 PM
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what would be max power on 9.3? with pump gas? without upgrading fuel system at the moment
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Old Mar 23, 2006 | 01:00 AM
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Im running 11psi on pump gas with 10.1 C/R Stock motor with no KR with around 13 degrees of timing. I think you might be able to get away with 15psi on pump gas with that C/R, but will most likely run low timing. My car gained 50rwhp by increasing 4-5 degrees of timing (100 mix with pump gas). So you will most likely need Alky to run 15psi on 9.3 C/R and some decent timing to make power. Just be careful when u tune it for the first time and monitor KR and A/F.
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