Dynamic Compression question
Dynamic Compression question So I have been playing with the DCR calculators I have found online. I know many have ran 243 heads on a stock ls1 with a stock ls1 cam before and never had issues with anything but when I put the numbers into the Wallace calculator it spits out a DCR of 9.48:1. I am using 10.567:1 as the static compression ratio from the TSP SCR calculator and the 01-02 cam specs (I think I did it right and got 31 degrees ABDC and then added 16 to it as I saw in some older threads on here for the Wallace site). Most say to stick around 8-8.5:1 but how would a nearly full point higher number run ok in so many cars and never really have issues?
My reason for doing this is to find the sweet spot for a new set of heads for my car with the stock cam. I would prefer to stay stock cam for now and then carry the new heads over to a new build later on. I was originally wanting to get as much compression as possible now because that's free power but I am worried about the DCR with the stock cam specs.
My reason for doing this is to find the sweet spot for a new set of heads for my car with the stock cam. I would prefer to stay stock cam for now and then carry the new heads over to a new build later on. I was originally wanting to get as much compression as possible now because that's free power but I am worried about the DCR with the stock cam specs.
Do you know where online I can find the duration at .006? I’ve looked all over and the best I can find is an old post on performance trucks listing the intake valve closing at .004 and that gave them a DCR around the mid 6s on a stock lq4. I’m normally really good at finding obscure info online but I don’t think anyone has this info on a stock cam.
Depending on your cam ramp rate, you need to add 25-28* to your IVC @0.050 duration to obtain approx. @.006 duration.
I had the same issue with my Titan 4 camshaft.
What I did is contact cam manufacturer asking for @.006 cam duration specs.
It’s the best way for accuracy.
I had the same issue with my Titan 4 camshaft.
What I did is contact cam manufacturer asking for @.006 cam duration specs.
It’s the best way for accuracy.
Last edited by cino; Mar 26, 2022 at 02:14 PM.
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From: Carnation, WA
Exactly, "per ramp" to find total duration advertised. But to find approx. advertised IVC for dynamic compression calculator, add 25-28 to @ 0.050 IVC (depending on ramp rate).
I edited my post.
Knowing only duration and IVC @ 0.050, this formula can be used to calculate IVC @ .006 (advertised):
IVC= Intake duration @0.050 + ramp rate = total advertised duration / 2 + ICL - 180
Example: knowing IVC @.050 is 42 and intake centerline 109 degrees with 55 degrees ramp rate.
227+55=282/2=141+109=250-180=70 degrees IVC advertised
I edited my post.
Knowing only duration and IVC @ 0.050, this formula can be used to calculate IVC @ .006 (advertised):
IVC= Intake duration @0.050 + ramp rate = total advertised duration / 2 + ICL - 180
Example: knowing IVC @.050 is 42 and intake centerline 109 degrees with 55 degrees ramp rate.
227+55=282/2=141+109=250-180=70 degrees IVC advertised
