Cam Data from Well-Developed Engines

[hoffman900]

WAG

How chromosomes - XX or XY relate to camshaft selection.

Stan

Oh wow. We have advanced that far since I took a nap? How long was I gone? Lol

I'm really over this site. I don't know if it can be saved.

Gary, LSA is an average. Add up your ICL and your ECL and divide by two. That gives you your LSA.

LSA * 2 = c , a+b = c . Good luck figuring out what A or B is without knowing any of the other.

A camshaft with a LSA of 106* can have any of the following centerlines:
Intake Exhaust
98 114
99 113
100 112
101 111
102 110
103 109
104 108
105 107
106 106
107 105
108 104
109 103
110 102
111 101
112 100
113 99
114 98
115 97
116 96
117 95
118 94
119 93
120 92

If the cam is assymetrical, like Crane, Comp, Jones, Harold Brookshire / UD / Lunati, etc. all have in their catalogs, then this throws a bigger wrench into things.

[GARY C]

Yep!

[V Remian]

Bob, I understand your exasperation. Using myself as a proxy for the average or even sub-average intellect on this site, we know how separate the wheat from the chaff. After a while you know what screen names to pass over and dismiss out of hand. Don't give up on us!

[SchmidtMotorWorks]

I say it's interesting because during a wide open throttle power pull the computer chooses a much tighter LSA for the lobes it's given with the exception of the top of the power curve.

So you agree that rpm range comes into cam selection ?

Yes, I don't know anyone who said it didn't.

Can you expand on the role RPM plays in cam selection?

[Stan Weiss]

Since it looks like we are playing 20 question.

How does the change in RPM effect the lag time of the air flow in degrees of crank rotation?

Stan

[V Remian]

Drill baby, drill! Free exchange of ideas. I have high hopes for this exchange.

[GARY C]

So you agree that rpm range comes into cam selection ?

Yes, I don't know anyone who said it didn't.

Can you expand on the role RPM plays in cam selection?

The cam is just one part of the engine combo that needs to be factored in with heads, intake, compression, valve train, header and intent to name a few...

[paulzig]

I think the data we get from testing engine components especially cylinder head/induction might be inadequate for a more thorough analysis. We have 28"H2O on a flow bench, which might bear somewhat of a semblance to real world in the intake port but the exhaust is a different matter altogether and is nowhere 'real world'.

Does anyone think getting away from flow numbers and into CFD testing of induction is a better option, getting rid of the flow bench?

As long as the heads/induction system has been analyzed and deemed fit for the bore/stroke and RPM wouldnt we be in a better position to pick valve timing events?

[user-23911]

I like the title of this one.

"Cam data from well developed engines".


It's so easy, everyone can do it themselves (yes, I have) without having to ask any questions.

Just go find yourself a "well developed engine" at your local junkyard.
Turn the flywheel into a degree wheel.
Adjust the valve lash so it's zero or negative.
Use a dial gauge to measurevalve lift every X crank degrees.
Pull the cam, measure base circle and max cam lift.

4 important numbers, IO, OC, EO, EC.
ICL, ECL, LSA, overlap, they're nothing more than different combinations of those 4 numbers.
Once you've done that, you'll be asking even more questions, like.......... why isn't max lift half way between open and close?
How would you know if you've never made the effort to measure?



A flow bench is OK but full of limitations.
28 inches water, that's about 1 PSI.
Atmospheric pressure is more like 14.5 PSI so it's 1/14.5 away from reality at best.
A flow bench that works at atmospheric pressure drop would be a good upgrade.
Making more vac than 28 inches isn't really practical either.
Even a 2000W electric vac motor struggles to make 28 inch vac at max head flow, well it won't.
So you'd need other methods, like a turbo converted to a jet engine.

[cjperformance]

Given the roughly 30% difference in the values for the cams in the variety of engines, I think it is fair to say, that the best universal cam formula possible from a few engine parameters will be within 15% - 30% of optimum for some engines.

Ok lets just end this here , ^^^ its simple. If the magic LSA is 110* which is what I notice looking thru a catalogue then +/- 30% gives us an optimum range for LSA of 77* to 143* 'depending on engine design and use' !!
Solved

[Geoff2]

I am getting a headache....

[cjperformance]

I am getting a headache....

Oh yeah

[Orr89rocz]

Try getting a human without a human and let me know how that goes, it takes two humans by the way, we have over 7 billion tests confirming this study.
Not sure what multiplying the lobe separation by 2 has to do with it.

Because LSA is just half the sum of the ICL and ECL.

106 lsa can have the same cam lobes but on different centerlines and behave rather differently

106 lsa. 100 intake centerline. 112 exhaust centerline
106 lsa. 110 intake centerline. 102 exhaust centerline

You think those cams will behave same in the same motor?

[SchmidtMotorWorks]

The cam is just one part of the engine combo that needs to be factored in with heads, intake, compression, valve train, header and intent to name a few...

How do you use RPM to determine lift, duration and centerlines?

[Stan Weiss]

I like the title of this one.

"Cam data from well developed engines".


It's so easy, everyone can do it themselves (yes, I have) without having to ask any questions.

Just go find yourself a "well developed engine" at your local junkyard.
Turn the flywheel into a degree wheel.
Adjust the valve lash so it's zero or negative.
Use a dial gauge to measurevalve lift every X crank degrees.
Pull the cam, measure base circle and max cam lift.

4 important numbers, IO, OC, EO, EC.
ICL, ECL, LSA, overlap, they're nothing more than different combinations of those 4 numbers.
Once you've done that, you'll be asking even more questions, like.......... why isn't max lift half way between open and close?
How would you know if you've never made the effort to measure?



A flow bench is OK but full of limitations.
28 inches water, that's about 1 PSI.
Atmospheric pressure is more like 14.5 PSI so it's 1/14.5 away from reality at best.
A flow bench that works at atmospheric pressure drop would be a good upgrade.
Making more vac than 28 inches isn't really practical either.
Even a 2000W electric vac motor struggles to make 28 inch vac at max head flow, well it won't.
So you'd need other methods, like a turbo converted to a jet engine.

Joe,
Really?

NOT! I am sure you understand pressure deferential. To see the full 14.69 psi you would need absolute zero pressure / psi in the cylinder.

Also just what is the atmospheric pressure in the room when you are flowing the heads?

Stan