Cal

iTrader: (1)

Just wondering how to calculate DCR, and if I even have enough information about my cam to do so. All I know:
Intake: 235* duration @.050 with .602" lift
Exhaust: 240* duration @ .050 with .598 lift
LSA: 112*
Advance 2* ground in

The formula yields 12.5* intake/exhaust overlap.

I'm thinking knowing the DCR will help me determine how much more compression I could run with this cam. Motor stays pretty cool with 160 stat, lowered fan on temps, and electric water pump. 92 octane pump gas, elevation 4500 feet and low humidity (if that maters.)

tim99ws6

iTrader: (31)

http://www.smokemup.com/auto_math/dy...sion_ratio.php

Cal

iTrader: (1)

Looks like a cool calculator, but how do you get it to calculate? Do you have to log in?

tim99ws6

iTrader: (31)

O yea sorry, i think you have to register to the site, and then you can use their carious calculators and so on. I figured it's worth it, as there are a few helpful interactive calculators there.

tim99ws6

iTrader: (31)

I'm running 11.192:1 SCR, and 10.183 DCR with no ill effects. My motor runs cool, oil pressure has yet to dip below 40psi, and oil temp rarely has ever gotten above 190

Cal

iTrader: (1)

Good to hear you're able to run that SCR. I was thinking about trying something around 11:1, but I wanted to verify that would work well. I noticed the caluculator needs the intake closing time . . . do you know what it was for your cam? Unfortunately I didn't get a real cam card and TSP never sent me one like they promised.

tim99ws6

iTrader: (31)

yea, i knew what mine was. Unfortunately TSP did the same thing to me, so i had to go have the cam custom degreed in by a race shop(motor was out of the car) to get all the valve events on the cam.

You don't need to worry too much about your SCR as you do about your DCR. The size cam you're running though, i bet you're bleeding off quite a bit of compression with that thing. my heads are 60cc LS6 GMPP heads. I also have -1cc valve relief pistons

Cal

iTrader: (1)

OK I just got registered and got that calc going, pretty cool. Looks like SCR=DCR only if the intake closes at BDC, interesting. Makes sense. Yeah I think I could bump up the compression quite a bit from what I have now; still have stock LS1 heads with no valve reliefs in the pistons. I'm thinking of welding the chambers instead of milling the heads, and CCing them to about 11:1. That way I won't lose P2V and my pushrods will still be the right length, and ports will still match the intake.

BTW, did TSP have a compression ratio recomendation for your cam?

jrp

iTrader: (16)

you cant calculate with duration @ .050, you need .004/.006.

my SCR is 12.02 and my DCR is 8.49. stock DCR compression on an ls1 is ~7.0. Tim theres no way yours is 10.13 unless your using FI.

jrp

iTrader: (16)

cal guestimating on a few things i come up with 7.59 DCR.

Cal

iTrader: (1)

Ahh good to know, I was wondering about that!

Cal

iTrader: (1)

Thanks for the guestimation JRP! Sounds like I could run 11:1 SCR no problem then.

So if stock DCR is only 7:1, does that mean even an LS1 with the stock cam could run higher compression?

tim99ws6

iTrader: (31)

I thought that sounded extremly odd, but it was the best calculation tool i can find. Do you have a link, or can you post the formula to use to be able to find DCR for us JRP? I appreciate the help. The more i thought about it after posting that link(just found it this morning), the more i started to doubt it. Good thing you came in here and cleared it up.

Cal-TSP did no give me a recommended compression to run with this cam. Matter of fact, due to a mix-up with their cams, I acutally got a completely different grind cam than what i was supposed to get. No worries, it seems to be performing quite well on mail-order tune!!


Good luck with it Cal!