Camshaft Math - A little help with the calculations

[Sendero]

Finally, I got someone to take measurement of their stocck cams before they buttoned up their install. From what I understand this was taken with a degree wheel and the Ford cam tools for DOHC's.

Here is what he got:

Exhaust
open @.0001 117 atdc
open @ .050 150.5 deg. atdc
closed @ .050 15.0 deg. btdc
closed @ .0001 32 atdc

Intake
open @ .0001 18 btdc
open @ .050 15.5 deg. atdc
closed @ .050 140.0 deg. btdc
closed @ .0001 94 btdc

The @.0001 measurement is supposed to be total duration. The only problem is, I cannot calculate that with the degrees taken at ATDC and BTDC.

Here is what I know so far:

Intake Duration @ .050 - 206
Exhaust Duration @ .050 - 194
Valve Lift (Both) - .397
Intake Centerline - 114*
Exhaust Centerline - 114*
Lobe Seperation - 114*

I'm only missing the total duration. Could someone please point me in the right direction?

[86GT]

Below is what I got

[coupe]

It's got 30.5º advertised overlap...50º total overlap.
and yes: 284º intake 275º exhaust.

Lobe Separation Angle (LSA) is just an average of the Intake & Exhaust Centerlines.

[Sendero]

Originally Posted by 86GT

Below is what I got

How did you calculate that?

-and-

When is version 2.5.0.X going to be released? I only have 2.0.2.3.

For reference, look at the Stock DOHC Modular (4 valve) cams you already have loaded in the program. Those are the cams for the 99-02 Cobra C Head motors. I do know that we share the same centerlines and lobe seperation, but my cams have more duration both at .050 and total. But not as much total duration as you have there.







Sidenote: I have been working on this "project" for about 6 months. What annoys me most about all of this is that people I have talked to know what the specs are and won't just tell me. Its like they are some big secret. If I didn't depened on my car for daily transportation the cams would have already been pulled and measured. Sorry for the rant.

[coupe]

You need to tighten up the .001 duration and open up the .050 duration (to more like 215º and 270.º Then I would build a little less overlap into them, but still keep some. I can only think the 4-valve stuff likes the extra overlap; otherwise Ford would not have given so much...especially at .050. $ .02

[86GT]

Originally Posted by Sendero

Here is what he got:

Exhaust
open @.0001 117 atdc
open @ .050 150.5 deg. atdc
closed @ .050 15.0 deg. btdc
closed @ .0001 32 atdc

Intake
open @ .0001 18 btdc
open @ .050 15.5 deg. atdc
closed @ .050 140.0 deg. btdc
closed @ .0001 94 btdc

First off most cam specs reference intake events with BTDC (Before Top Dead Center) and ABDC (After Bottom Dead Center) and the exhaust events as BBDC (Before Bottom Dead Center) and BTDC (Before Top Dead Center). This means a few of your numbers need to be converted.

Lets use the intake event at 0.05 as an example, the value you have for the open event at is 15.5ATDC which is the same as saying -15.5 BTDC. The only thing that changes is the sign. The close event is at 140 BTDC which is the same as 40 ABC.

Now you can add the numbers together. Take the (-15.5) + 180 + 40 to get 204.5. You can now do the same to get the other events.

The overlap at 0.05 lift is 0 (intake opens ATDC and exhaust close BTDC) this means no overlap can exist.
The overlap at 0.001 lift is 48.75

Version 2.5 of the EEC Analyzer will have support for the Scan Tool which connects to the ODBII connector and will be able to log data. It is still a work in progress, but it will also be able to read DTC.

[Scothew]

I dont know anything about figureing this out, but glad your info gathering is coming along good Nathan.. Know you been working hard on it

[Sendero]

Originally Posted by 86GT

First off most cam specs reference intake events with BTDC (Before Top Dead Center) and ABDC (After Bottom Dead Center) and the exhaust events as BBDC (Before Bottom Dead Center) and BTDC (Before Top Dead Center). This means a few of your numbers need to be converted.

Lets use the intake event at 0.05 as an example, the value you have for the open event at is 15.5ATDC which is the same as saying -15.5 BTDC. The only thing that changes is the sign. The close event is at 140 BTDC which is the same as 40 ABC.

Now you can add the numbers together. Take the (-15.5) + 180 + 40 to get 204.5. You can now do the same to get the other events.

The overlap at 0.05 lift is 0 (intake opens ATDC and exhaust close BTDC) this means no overlap can exist.
The overlap at 0.001 lift is 48.75

Thanks Clint! I was on the right track, but wasn't sure if my numbers were correct. I had even drawn up a little diagram with the degree's marked on it.

[Sendero]

Had the wrong smilie in the first response.

[Wicked]

I know I'm late, but I got 284/275 as well.