My cam selection and calculations
My cam selection and calculations Here are the specs:
5.7L Stock LS1 shortblock
PRC Stage 2.5 5.3 heads with 59cc chambers
LS7 lifters, hardened pushrods, trunion upgraded rockers, ect ect
LS9 HG's
LS6 Intake manifold, P&P Stock TB, Big 4 inch intake, 85mm MAF
1 5/8 shorties, 2.25" off each header into single 3 inch, through a resonator and a flowmaster and then dual 2.5" out the back
Rock solid Tune via HPTuners
Occasional 100 shot Nitrous.
Desired Behavior:
Daily driver vehicle, needs to retain close to current mileage, lopey idle is alright as long as no surging in lower RPM's in 6th gear (I can tune alot of this out).
Based on my calculations, the Dynamic CR of the LS1 is ~7.00 +/- 0.10.
With the above mods I will have a Static CR of ~11.2:1
I am shooting for 8.2-8.3 Dynamic CR, leaving a small safety margin on the table. My exhaust system is shitty, comparatively to others, therefore I plan to hold the exhaust open quite a bit longer (split pattern cam). Additionally, some overlap is desired to keep my EGT's down.
As far as lobes go, I would like to stay away from anything too aggressive. I am going to choose my specs and then probably contact Cam Motion to have it cut using one of there lateest and greatest lobes, or Geoff to get the EPS lobes.
I am looking somewhere is the neighborhood of:
230/242 @ 0.050 in
ICL = 111
LSA = 114
Lift Undetermined
Results:
Dynamic CR=8.36, IVC=46 degrees ABDC @ 0.050 in or ~72 degrees ABDC @ 0.006 in, Overlap=8 degrees
Thoughts cam experts? Sell me a cam!
5.7L Stock LS1 shortblock
PRC Stage 2.5 5.3 heads with 59cc chambers
LS7 lifters, hardened pushrods, trunion upgraded rockers, ect ect
LS9 HG's
LS6 Intake manifold, P&P Stock TB, Big 4 inch intake, 85mm MAF
1 5/8 shorties, 2.25" off each header into single 3 inch, through a resonator and a flowmaster and then dual 2.5" out the back
Rock solid Tune via HPTuners
Occasional 100 shot Nitrous.
Desired Behavior:
Daily driver vehicle, needs to retain close to current mileage, lopey idle is alright as long as no surging in lower RPM's in 6th gear (I can tune alot of this out).
Based on my calculations, the Dynamic CR of the LS1 is ~7.00 +/- 0.10.
With the above mods I will have a Static CR of ~11.2:1
I am shooting for 8.2-8.3 Dynamic CR, leaving a small safety margin on the table. My exhaust system is shitty, comparatively to others, therefore I plan to hold the exhaust open quite a bit longer (split pattern cam). Additionally, some overlap is desired to keep my EGT's down.
As far as lobes go, I would like to stay away from anything too aggressive. I am going to choose my specs and then probably contact Cam Motion to have it cut using one of there lateest and greatest lobes, or Geoff to get the EPS lobes.
I am looking somewhere is the neighborhood of:
230/242 @ 0.050 in
ICL = 111
LSA = 114
Lift Undetermined
Results:
Dynamic CR=8.36, IVC=46 degrees ABDC @ 0.050 in or ~72 degrees ABDC @ 0.006 in, Overlap=8 degrees
Thoughts cam experts? Sell me a cam!
I'd go a little bit smaller, like a 226 intake duration and a 234 exhaust duration 114lsa +2, which would have 2* overlap, a IVC of 45* and a DCR of about 8.34 with having a SCR of 11.2 . I figured the DCR with the cam having Cam Motion cam lobes having a ramp rate of 55* which is what I was told it is by Cam Motion. As far as lift I'd keep it in the .590" to .615" range for the intake lobes to make the most of the flow potential of the heads, and .570"-.600" range for the exhaust lobes. With EPS lobe you're probably looking at a DCR around 8.5-8.6 with al else being equal minus the lobe ramp rates. FYI the DCR is only a guess since I'm not 100% sure of the ramp rates of the EPS lobes, which I believe are about 60-61. BTW with the Cam Motions lobes you can go with almost any lift you want.
Last edited by 99Bluz28; Nov 14, 2014 at 09:35 PM.
I have my specs dialed in and am now designing a lobe profile. I am curious as to what the EPS and Cam Motion lobes look like. Obviously this is now something available to the public and is their marketing leverage.
I am graphing lifter motion with respect to cam position to observe position, velocity, acceleration, and jerk to develop my own lobe profile. Additionally, rocker arm motion has been precisely measured. As the lifter motion actuates the rocker arm, the rocker ratio changes depending on its position, ultimately changing the motion of the valve. It is never a constant (i.e. 1.7, 1.8 etc). The lobe profile is created such that you know exactly where the valve is at any point in time. The inherent dynamically changing rocker ratio can cause some funky acceleration and jerk characteristics and be tuned out with the lobe profile.
Knowing the flow data for the cylinder heads, I can make a flow curve, and then calculate an estimated net flow versus cam position based on a given cam lobe profile. I can try and maximize net flow under the curve while smoothing the acceleration and jerk profiles of the cam lobe.
I am graphing lifter motion with respect to cam position to observe position, velocity, acceleration, and jerk to develop my own lobe profile. Additionally, rocker arm motion has been precisely measured. As the lifter motion actuates the rocker arm, the rocker ratio changes depending on its position, ultimately changing the motion of the valve. It is never a constant (i.e. 1.7, 1.8 etc). The lobe profile is created such that you know exactly where the valve is at any point in time. The inherent dynamically changing rocker ratio can cause some funky acceleration and jerk characteristics and be tuned out with the lobe profile.
Knowing the flow data for the cylinder heads, I can make a flow curve, and then calculate an estimated net flow versus cam position based on a given cam lobe profile. I can try and maximize net flow under the curve while smoothing the acceleration and jerk profiles of the cam lobe.
What exactly are you referencing when you say 55*, 60*, etc? Is this the degrees it takes to travel from something like 0.004 or 0.006 in lift (~point of valve to seat contact) to 0.050 inch lift?
