8.5 compression- help a limey!
Thread Starter
Teching In
Joined: Nov 2002
Posts: 13
Likes: 0
From: UK
8.5 compression- help a limey! I've have a new LS1 crate engine and plan to add twin turbochargers and a liquid intercooler to give a streetable 500+ HP.
From what I've read on the board, the simplest and safest way to go is with a piston that gives a CR of about 8.5:1 with the stock 68cc heads.
Can anyone recommend a set of pistons for this?
Should I also fit stiffer inlet springs or will the stock springs be ok?
Will the stock crank and rods hold up if I keep the RPM to under 6000?
What total boost can I expect to have to run for my desired output?
Thanks Guys.
Great board!!
From what I've read on the board, the simplest and safest way to go is with a piston that gives a CR of about 8.5:1 with the stock 68cc heads.
Can anyone recommend a set of pistons for this?
Should I also fit stiffer inlet springs or will the stock springs be ok?
Will the stock crank and rods hold up if I keep the RPM to under 6000?
What total boost can I expect to have to run for my desired output?
Thanks Guys.
Great board!!
Re: 8.5 compression- help a limey! on my 512 rwhp turbo car i used JE pistons and eagle rods, stock crank resulting in a 9:1 CR, Id say its reliable as im only getting .97* KR
see thread for my build up details.
https://ls1tech.com/ubb/ultimatebb.p...=001138#000000
see thread for my build up details.
https://ls1tech.com/ubb/ultimatebb.p...=001138#000000
Re: 8.5 compression- help a limey! You can make 500 HP on a stock motor, but not the recommended setup.
I would stay above 9:1 if your after a street car type setup, part throttle/off boost performance will suffer on a stock head/cam low CR motor. Although not much, but it will be noticable.
If your after pistons, call/email Diamond Pistons. They are now making off the shelf FI pistons for the LS1 in stock bore sizes for use w/ stock rods. The rods themselves should be fine, but upgraded rod bolts are recommended.
You will have no problems w/ the crank, I still run a stock crank <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Depending on the size of the turbos, you should be in the 7 to 10 psi range for 500 RWHP. That's assuming stock heads/cam.
Be sure to have a fuel system capable of supporting the power your after. If in doubt, have too much fuel system. Being on the edge w/ the fuel delivery is disaster waiting to happen.
Good luck
I would stay above 9:1 if your after a street car type setup, part throttle/off boost performance will suffer on a stock head/cam low CR motor. Although not much, but it will be noticable.
If your after pistons, call/email Diamond Pistons. They are now making off the shelf FI pistons for the LS1 in stock bore sizes for use w/ stock rods. The rods themselves should be fine, but upgraded rod bolts are recommended.
You will have no problems w/ the crank, I still run a stock crank <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Depending on the size of the turbos, you should be in the 7 to 10 psi range for 500 RWHP. That's assuming stock heads/cam.
Be sure to have a fuel system capable of supporting the power your after. If in doubt, have too much fuel system. Being on the edge w/ the fuel delivery is disaster waiting to happen.
Good luck
10 Second Club
Joined: Apr 2002
Posts: 1,755
Likes: 2
From: Cincinnati, Ohio
Re: 8.5 compression- help a limey! Like y2khawk said, I would watch going too low on compression. I had my 382 done with appr. 9:0 comp. and it was kind of doggy down low (worse than the stock motor). I was able to lay in a lot of timing though without knock, It would pull strong once the revs were up. If your willing to sacrifice low end you could probably make more overall power with low compression and high boost. I didn't like the low end torque loss so I am going with more cubes and a 9:5 comp..
Thread Starter
Teching In
Joined: Nov 2002
Posts: 13
Likes: 0
From: UK
Re: 8.5 compression- help a limey! Thanks Guys. I guess it's striking that balance between upper and lower end power, which all depends on how I want it to drive.
I presume that the lighter the car, the less important the lack of low end power?
So what about the stock cam and injectors?
Will the cam work ok with the twin turbo set-up or is there too much over-lap?
Are the stock injectors up to the job of 10psi boost or will they need to be replaced?
Your help is really appreciated.
Tom.
I presume that the lighter the car, the less important the lack of low end power?
So what about the stock cam and injectors?
Will the cam work ok with the twin turbo set-up or is there too much over-lap?
Are the stock injectors up to the job of 10psi boost or will they need to be replaced?
Your help is really appreciated.
Tom.
Re: 8.5 compression- help a limey! cam wiil work, but if you want more aggresive power, might look into a new one. Youll definatly have to upgrade your fuel system, those whimpy 28lbs arnt good for much.
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Verdad Gallardo Re: 8.5 compression- help a limey! I am still on stock rails and stock regulator. Although i think i need to get a better regulator, it seem to dip in fuel pressure for a second under hard acceleration. they are not needed right away, but are good to have.
I have the 42lb SVO's.
I have the 42lb SVO's.