Engine questions
New Member
Joined: 12-13-08
Posts: 40
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From: Seattle
Just my 2 cents but, I would think you should be able to eliminate most if not all problems that would come up from raising the CR to a 10:1 by getting a proper tune and having the correct supporting mods for your set up. IE: bigger heat exchanger, Injectors etc....
Senior Member
Joined: 04-16-06
Posts: 15,224
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From: Schweinfurt, Germany
There is a lot of scattered mis-info in this thread.
I really dont know much about nitrous so I will skip that.
The 1400 HP Cobalt is running 10.8 compression and 40+ PSI. Higher compression doesnt mean you can not run boost or high boost. This is misleading information. There is a balance. You have to take more precautions WHEN boosting on high compression, such as cooling mods & higher octane.
Higher compression = more heat. Cooling mods will help immenesly and will help prevent knock. (New/Additonal heat exchanger, dual pass endplate, meth injection, etc..)
There is also no specific number that says you have to drop timing. 4 most common knock creators, too much timing, too little timing, too lean, too rich.
My personal suggestion would be to get your fueling correct first, if it is spot on, and you are still seeing knock, THEN adjust the timing little by little until you are no longer seeing knock. Dropping timing is not always the answer, because you can get knock from having the timing reduced too much.
As far as what you will need when doing the rebuild. Make sure you have all your gaskets/seals, rod bolts, crank bolts, head bolts, cam bolts, almost all the bolts are torque-to-yield on the 'important stuff'. I have speant 250$+ on bolts and gaskets when putting my LSJ back together.
FYI I will be running 10.5 comp pistons w/stock pulley... Long story on why, but the car should be running this weekend.
I really dont know much about nitrous so I will skip that.
The 1400 HP Cobalt is running 10.8 compression and 40+ PSI. Higher compression doesnt mean you can not run boost or high boost. This is misleading information. There is a balance. You have to take more precautions WHEN boosting on high compression, such as cooling mods & higher octane.
Higher compression = more heat. Cooling mods will help immenesly and will help prevent knock. (New/Additonal heat exchanger, dual pass endplate, meth injection, etc..)
There is also no specific number that says you have to drop timing. 4 most common knock creators, too much timing, too little timing, too lean, too rich.
My personal suggestion would be to get your fueling correct first, if it is spot on, and you are still seeing knock, THEN adjust the timing little by little until you are no longer seeing knock. Dropping timing is not always the answer, because you can get knock from having the timing reduced too much.
As far as what you will need when doing the rebuild. Make sure you have all your gaskets/seals, rod bolts, crank bolts, head bolts, cam bolts, almost all the bolts are torque-to-yield on the 'important stuff'. I have speant 250$+ on bolts and gaskets when putting my LSJ back together.
FYI I will be running 10.5 comp pistons w/stock pulley... Long story on why, but the car should be running this weekend.
Senior Member
Joined: 08-13-05
Posts: 5,733
Likes: 1
From: the glove
There is a lot of scattered mis-info in this thread.
I really dont know much about nitrous so I will skip that.
The 1400 HP Cobalt is running 10.8 compression and 40+ PSI. Higher compression doesnt mean you can not run boost or high boost. This is misleading information. There is a balance. You have to take more precautions WHEN boosting on high compression, such as cooling mods & higher octane.
Higher compression = more heat. Cooling mods will help immenesly and will help prevent knock. (New/Additonal heat exchanger, dual pass endplate, meth injection, etc..)
There is also no specific number that says you have to drop timing. 4 most common knock creators, too much timing, too little timing, too lean, too rich.
My personal suggestion would be to get your fueling correct first, if it is spot on, and you are still seeing knock, THEN adjust the timing little by little until you are no longer seeing knock. Dropping timing is not always the answer, because you can get knock from having the timing reduced too much.
As far as what you will need when doing the rebuild. Make sure you have all your gaskets/seals, rod bolts, crank bolts, head bolts, cam bolts, almost all the bolts are torque-to-yield on the 'important stuff'. I have speant 250$+ on bolts and gaskets when putting my LSJ back together.
FYI I will be running 10.5 comp pistons w/stock pulley... Long story on why, but the car should be running this weekend.
I really dont know much about nitrous so I will skip that.
The 1400 HP Cobalt is running 10.8 compression and 40+ PSI. Higher compression doesnt mean you can not run boost or high boost. This is misleading information. There is a balance. You have to take more precautions WHEN boosting on high compression, such as cooling mods & higher octane.
Higher compression = more heat. Cooling mods will help immenesly and will help prevent knock. (New/Additonal heat exchanger, dual pass endplate, meth injection, etc..)
There is also no specific number that says you have to drop timing. 4 most common knock creators, too much timing, too little timing, too lean, too rich.
My personal suggestion would be to get your fueling correct first, if it is spot on, and you are still seeing knock, THEN adjust the timing little by little until you are no longer seeing knock. Dropping timing is not always the answer, because you can get knock from having the timing reduced too much.
As far as what you will need when doing the rebuild. Make sure you have all your gaskets/seals, rod bolts, crank bolts, head bolts, cam bolts, almost all the bolts are torque-to-yield on the 'important stuff'. I have speant 250$+ on bolts and gaskets when putting my LSJ back together.
FYI I will be running 10.5 comp pistons w/stock pulley... Long story on why, but the car should be running this weekend.
cool the ait's you want, but the DCR on a 10.0 / 10.5 set up with even mild boost will be kr crazy.
you'll have to pull so much timeing out to safe, your egt's will go crazy.
with this little displacement you don't make horsepower on CR, its boost and timeing.
Cory (alpha) found this out first hand.
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