Boost limits... Engine efficiency...
01-22-2007, 03:29 AM
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Boost limits... Engine efficiency... New to FI but learnin' fast. I understand that the amount of boost you can run on an engine is based on the compression ratio and the effiecency. I am currently building a 96 Z28 LT1 M6. I will be running a set of Brodix RaceRite 200's that flow pretty well. Due to the 68 cc chambers this drops my CR down to 9.4:1 . Because of the LT1 reverse coolant flow I've been told 11-11.4:1 is the upper limit. Due to a number of reasons I will be driving the car WITHOUT the rear mounted turbo I am currently assembling. Will it be possible to dyno tune the engine to see how effecient the motor is before I add the turbo? This will let me know how high I can run my boost before I start doing bad things to the motor. Is there another way to determine my boost limits. When I add the turbo I will be switching the cam as well so that will change things. The cam I currently have has too much overlap. It's a 229/242 @ .050 and 110 lca. I am told this is way to much overlap for a turbo. Basically, I want to blow this baby as hard as I can without detonation. How do you guys figure this out? Also, how much does adding N20 change the equation? My other babys are bottle babys, this is my first FI but I was thinking a nice 75 shot would help cool the air AND give me more ponies!!! Thanx for all the help! Feel free to ask for whatever specks I did not include that will be needed. What cam specs work best with turbo setups?
01-23-2007, 05:02 PM
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LT1 guy here too. Most of the boosted LT1 crowd seems to hang out on CZ28...
Is the bottom end stock? Even at 9.4:1, you're looking at around 8-10psi max with a GOOD tune (no detonation and good A/F ratio) because of the stock craptastic pistons.
It won't hurt at all to drive around on that motor without the turbo. You'll see a loss of about 3% overall power going from stock 10.5:1 to 9.4:1 with no other changes. So, you'll lose in the neighborhood of 15-20rwhp which is not a big deal...
Nitrous and boost on a stock bottom end would be a no-no... Although, if you wanted to help spool that baby faster and get more low end while out of boost (or while waiting for it to spool), NX has a new boost-reference progressive nitrous controller. You can spray when boost is low to give that added umph and slowly take away spray as the boost increases.
Is the bottom end stock? Even at 9.4:1, you're looking at around 8-10psi max with a GOOD tune (no detonation and good A/F ratio) because of the stock craptastic pistons.
It won't hurt at all to drive around on that motor without the turbo. You'll see a loss of about 3% overall power going from stock 10.5:1 to 9.4:1 with no other changes. So, you'll lose in the neighborhood of 15-20rwhp which is not a big deal...
Nitrous and boost on a stock bottom end would be a no-no... Although, if you wanted to help spool that baby faster and get more low end while out of boost (or while waiting for it to spool), NX has a new boost-reference progressive nitrous controller. You can spray when boost is low to give that added umph and slowly take away spray as the boost increases.
01-23-2007, 07:29 PM
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Originally Posted by Snyper
what about 8.3:1? thats where ill be around with my pistons/heads..(also on an LT1) however the car will have the turbo on from the start...
Obviously every setup is different, so just use the numbers I'm throwing out as a reference. Stay away from detonation and lean conditions and see what she'll do.
