Compression,boost,cams,and power

[CRXSI91]

ok,we all know,the lower u drop your compression,the more power u lose...but in essence..the easier it is to tune your car for forced induction...now lets say..i want to put lower compression pistons in my b18b block..and then forged rods..then a block guard..or not even do the block guard...lets say i drop the compression to about 9:1...i know when not under boost my car wont be that quick...so is there anyway i can run crower stage 1 cams for my LS head,and gain back a little bit of power to hold out until full spool...or will running the stage 1's cut into the boost,overlaping the valves..cus i know people say "Run turbo profile cams"...but what is the main downfall of running NA (not all motor cams..na cams) cams when your boosting??? does it have a major effect on your psi? or can it be tolerated and make up for a little power loss?

 

[D See 2]

good question. i'm anxious to find out as well.

 

[posol]

lower compression is not "easier to tune". it just leaves a great margin for error. if you have a good tuner, and good tuning/efi fuel management, there is NO practical good reason to go low compression anymore unless you plan to run 23213123 psi.

the real issue here is that you are thinking about running a larger cam to make up for the lower compression. frankly, its not going to work as you think.

Cams require a certain compression range to work good and make power. if you go up with the cam, and down with the compression, you're going to lose even more power.
basically, what happens, is that you lower cyl. pressures.

 

[reckedracing]

lets say i drop the compression to about 9:1...

you know the B18B has a STOCK compression ratio of only 9.2:1...

you wanna run big boost drop it to 8:1 or something... .2 drop is nill...

and if you size the turbo right you should have full boost by 3500 ish?
and you will have some, but not full, boost before that...

 

[formby]

also you have a light crx with an ls; it has plenty of off boost power to launch the car...too much and you'll have no traction...if you want full boost faster get a smaller snail....remember that an ls has a low rpm range so you want power with in the range allowed....

 

[CRXSI91]

ahh ok...so what if i wanted to put stage 1 crower cams,and valvetrain inside of a b18b head right now..and do a valve job on the head,and maybe pnp it too..and then used that head for turbo..what would be the disadvantage/advantage of running that setup over running a turbo profile cam setup on the same b18b head?

 

[posol]

turbo cams generally use a larger lift, and near stock duration
na cams generally increase the lift a little bit, but offer much longer duration.

either way, when you go to a larger cam, you're going to want more effective compression.

 

[CRXSI91]

so basically..if i find a good tuner,that knows what they are doing..i can keep the compression on the LS motor to factory spec...throw some rods and pistons in there..and boost it,instead of dropping comp.,losing power,and having to gain it back with a turbo....makes good sense..

but what is the ratio of people lowering compression,to people keeping the compression factory spec on LS motors,and then boosting them? i mean i have two LS motors..but that doesnt mean im gonna be reckless,and boost the hell out of it and blow it up,cus i thought i could run high comp...

 

[reckedracing]

i honestly don't even think you need rods and pistons...
i think the main thing that will be holding you back is the sleeves...
you could run rods and pistons and your lower end will be stronger, but you're overlooking the sleeves that contain the combustion...
so you could either run the block stock... but if you're building the lower end you should prob go all out and make it bullet proof, then the skies the limit

what are your goals? whats your expected HP range?

 

[posol]

you'll break an LS rod before you crack a sleeve (assuming properly tuned).

300 whp is the safe limit for factory sleeves.

in building an LS block, i would look at 9.5-9.8:1 compression forged pistons, forged rods, plety of fuel, and plenty of control over it.

 

[CRXSI91]

Originally posted by reckedracing@Mar 17 2005, 09:34 AM
i honestly don't even think you need rods and pistons...
i think the main thing that will be holding you back is the sleeves...
you could run rods and pistons and your lower end will be stronger, but you're overlooking the sleeves that contain the combustion...
so you could either run the block stock... but if you're building the lower end you should prob go all out and make it bullet proof, then the skies the limit

what are your goals? whats your expected HP range?

[post=474689]Quoted post[/post]​

goals are 300 whp,expected hp range is about 250 275..i just want a street/track monster...QM times dont really interest me too much..just a normal 12 second pass..i mean i have two ls motors...so i have a little bit of security,but i still dont want to half ass my build,and end up wasting time..

 

[CRXSI91]

Originally posted by pissedoffsol@Mar 17 2005, 10:32 AM
you'll break an LS rod before you crack a sleeve (assuming properly tuned).

300 whp is the safe limit for factory sleeves.

in building an LS block, i would look at 9.5-9.8:1 compression forged pistons, forged rods, plety of fuel, and plenty of control over it.

[post=474731]Quoted post[/post]​

yea,im working on my fuel setup right now,probably gonna start off with the pump and injectors..im lookin into the walbro 255 lph,and some 440 cc injectors..i dont know if i should get some used dsm ones,or RC...