Jeep Strokers

Ours is going to probably be more accurate.

Are you forgetting about any advance by chance?

If you have an accurate IVC value, its probably best to use that.


I guess its also possible that something is wrong .. but by now it has been tested pretty thoroughly... (unless people havent been reporting problems!)

Muad'Dib wrote:Ours is going to probably be more accurate.

Are you forgetting about any advance by chance?

If you have an accurate IVC value, its probably best to use that.


I guess its also possible that something is wrong .. but by now it has been tested pretty thoroughly... (unless people havent been reporting problems!)

Yes, I degreed my cam, so the IVC matches the cam card. The advance in ground into the cam.

dwg86 wrote:When using the CR Calculator, I end up with 2 different dynamic numbers using the IVC and the advertised duration methods. Using the IVC I get 9.24cr/8.66 dynamic cr. Using the advertised duration I get 9.24cr and 7.6 dynamic. I also went to http://www.kb-silvolite.com and used thier cr calculator and got 9.24cr and 8.09 dynamic...What gives? Which one is right?

Make sure you are using the "Advertised" intake valve closing event. NOT the 0.050"

lafrad wrote:

dwg86 wrote:When using the CR Calculator, I end up with 2 different dynamic numbers using the IVC and the advertised duration methods. Using the IVC I get 9.24cr/8.66 dynamic cr. Using the advertised duration I get 9.24cr and 7.6 dynamic. I also went to http://www.kb-silvolite.com and used thier cr calculator and got 9.24cr and 8.09 dynamic...What gives? Which one is right?

Make sure you are using the "Advertised" intake valve closing event. NOT the 0.050"

I used the advertised dur 260 with 112 lobe seperation.

What happens when you use the calculator from the following page?:

http://www.empirenet.com/pkelley2/DynamicCR.html

Better yet here is a direct link to the download:

http://cochise.uia.net/pkelley2/dcrvb6.zip

The numbers you get from pkelley's calc should be the same as ours.

It would also help me if you provided all the specs your punching it.

Thanks!

Its got to have something to do with the built in advance...

I think you still need to specify how much advance there is when punching in the Duration and the LSA. When using the IVC value, you dont factor built in advance.

Take the stock renix cam.

Duration = 270
LSA = 112
Advance / Retard = -8

IVC = 75

Punch in LSA / Duration with -8 retard, you will get the same result if you use the IVC with 0 retard / advance.

Here are the specs of my build
bore 3.915
stroke 3.895
rod 5.875
0 deck
gasket bore 4.0
gasket thikness .043
head cc 62.8
piston cc 21.6
advertised dur 260
lobe sep 112
IVC 37
advance 0

I had brought up this problem before. My suggestion was, if the IVC field is populated, to grey out the box for advance/retard.

3 degree advance ground into the cam

IVC is IVC, right? intake centerline + lobe seperation + degree of advance ground into cam is HOW you'd figure out IVC.

IVC is relative to what degree the crank is at when the intake valve seats. The crank doesn't know if its +/-4. Therefor when inputting IVC directly, built in timing should be included. Any plus or minus added after that would be added by an adjustable timing set.

Mgardiner1 wrote:IVC is IVC, right? intake centerline + lobe seperation + degree of advance ground into cam is HOW you'd figure out IVC.

IVC is relative to what degree the crank is at when the intake valve seats. The crank doesn't know if its +/-4. Therefor when inputting IVC directly, built in timing should be included. Any plus or minus added after that would be added by an adjustable timing set.

The Intake Valve Close (IVC) I got off my cam card. The IVC is 37 ABDC @ .050 at the lifter.

dwg86 wrote:

Mgardiner1 wrote:IVC is IVC, right? intake centerline + lobe seperation + degree of advance ground into cam is HOW you'd figure out IVC.

IVC is relative to what degree the crank is at when the intake valve seats. The crank doesn't know if its +/-4. Therefor when inputting IVC directly, built in timing should be included. Any plus or minus added after that would be added by an adjustable timing set.

The Intake Valve Close (IVC) I got off my cam card. The IVC is 37 ABDC @ .050 at the lifter.

Right... but that isn't what the calculator uses. YOu need the IVC at 0.003 (or less)

Mgardiner1 wrote:I had brought up this problem before. My suggestion was, if the IVC field is populated, to grey out the box for advance/retard.

But doing so would limit the calculator right? Its probably rare, but what if someone uses an adjustable timing set and only has IVC spec??

Cant you get IVC spec from the following?

IVOA (Intake Valve Opening Angle)
IVCA (Intake Valve Closing Angle)
I may change the calculator to only use IVC spec to limit these kinds of problems. If you dont know the IVC spec it will give it to you buy doing the calculations above, and entering that number in the IVC field for you... How does everyone feel about that?

On the Keith black calculator, it has you enter the IVC at .050 and add 15. When I use this calculator I come up with 8.089 DCR. I know my IVC is [email protected](that is what I degreed my cam at). I'm not trying to be argumentative, I'm just trying to figure out my correct DCR.