D V Live now.

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digger
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Re: D V Live now.

Post by digger »

SchmidtMotorWorks wrote:
> [quote=digger post_id=928569 time=1667249333 user_id=6525]
> In fairness to DV I've only ever heard him say this "128" is for
> WOT performance (its a given in anycase) so those are moot points in the
> context
> [/quote]
>
> Wide open throttle or not, a cam design should be compatible wit the
> intended application, the typical DV book reader is working on street
> driven cars with a wide variety of exhaust and intake systems each changing
> the optimum LSA.

Last time i checked simply defining the LSA does not make a camshaft incompatible with a street engine. There is the ambiguous overlap portion of his method that will impact on these aspects such idle, part throttle, fuel economy etc
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Re: D V Live now.

Post by Tom68 »

digger wrote:
There is the ambiguous overlap portion of his method that will
> impact on these aspects such idle, part throttle, fuel economy etc


Yer, that's almost a better starting point, pick the idle quality you need (could be for track rules) there's your overlap decided, then build out from there until you reach your desired rev range.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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Re: D V Live now.

Post by SchmidtMotorWorks »

digger wrote: Tue Nov 01, 2022 2:54 am SchmidtMotorWorks wrote:
>
digger wrote: Mon Oct 31, 2022 4:48 pm > In fairness to DV I've only ever heard him say this "128" is for
> WOT performance (its a given in anycase) so those are moot points in the
> context
>
>
> Wide open throttle or not, a cam design should be compatible wit the
> intended application, the typical DV book reader is working on street
> driven cars with a wide variety of exhaust and intake systems each changing
> the optimum LSA.

Last time i checked simply defining the LSA does not make a camshaft incompatible with a street engine. There is the ambiguous overlap portion of his method that will impact on these aspects such idle, part throttle, fuel economy etc
For given durations and acceleration rates, LSA determines drivability.
DV said it is "the most important thing about spec'ing a cam"
The notion that 2 inputs determine the LSA (and that it is the most important thing about spec'ing a cam) is absurd.

The most important thing about spec'ing a cam is determining that it is compatible with the valve train.
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Re: D V Live now.

Post by skinny z »

Now this is a genuine question. Not some kind of bait so I'll ask the following:

The application is strictly drag racing. Drivability isn't so much a concern as is maximum output.
Overlap, duration, LSA, ICL, lift.
These are the elements of a cam spec as I understand them and how would you rate in order of importance?

The specifics of the profile itself, that is it's "intensity" can be part of another conversation if it can work that way.

I'm asking because I'd like to know more about it.
When I have another discussion with my cam guy, the better informed I am, the more satisfying the result might be.
Thanks in advance.
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Re: D V Live now.

Post by skinny z »

Just to clarify, I'm not asking for a spec as there isn't nearly enough info given.
Just some guidelines a guy could go by.
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Re: D V Live now.

Post by SchmidtMotorWorks »

skinny z wrote: Tue Nov 01, 2022 10:30 am Now this is a genuine question. Not some kind of bait so I'll ask the following:

The application is strictly drag racing. Drivability isn't so much a concern as is maximum output.
Overlap, duration, LSA, ICL, lift.
These are the elements of a cam spec as I understand them and how would you rate in order of importance?

The specifics of the profile itself, that is it's "intensity" can be part of another conversation if it can work that way.

I'm asking because I'd like to know more about it.
When I have another discussion with my cam guy, the better informed I am, the more satisfying the result might be.
Thanks in advance.
Knowing what acceleration rate your valve train can handle is primary because it determines the area under the curve and the operation range.

Once you know that you adjust the individual events to match the gas dynamics of the system.
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Re: D V Live now.

Post by skinny z »

That area under the curve would reference intensity then?
As in, seat numbers vs .050, .200, etc?
Fair enough. ( If I have that right).

That's something I wanted to talk about with Jones Cams.
I've a seat duration in mind for a hydraulic roller but I'm at a loss as to which of his profiles will live or die in this application.
Eg. 286 with 236@.050 or 286 with 224@.050.
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Re: D V Live now.

Post by SchmidtMotorWorks »

skinny z wrote: Tue Nov 01, 2022 10:40 am That area under the curve would reference intensity then?
As in, seat numbers vs .050, .200, etc?
Fair enough. ( If I have that right).

That's something I wanted to talk about with Jones Cams.
I've a seat duration in mind for a hydraulic roller but I'm at a loss as to which of his profiles will live or die in this application.
Eg. 286 with 236@.050 or 286 with 224@.050.
The area under the curve is computed by integration.

https://www.youtube.com/watch?v=FsC3do74UIo

Without expensive testing, your best path to know what your valvetrain can handle is to work with a cam designer (not a cam spec'er) that knows from experience.
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Re: D V Live now.

Post by skinny z »

That's the plan.
Thanks Mr S.
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Re: D V Live now.

Post by digger »

SchmidtMotorWorks wrote:
> [quote=digger post_id=928634 time=1667285684 user_id=6525]
> SchmidtMotorWorks wrote:
> > [quote=digger post_id=928569 time=1667249333 user_id=6525]
> > In fairness to DV I've only ever heard him say this "128" is for
> > WOT performance (its a given in anycase) so those are moot points in the
> > context
> > [/quote]
> >
> > Wide open throttle or not, a cam design should be compatible wit the
> > intended application, the typical DV book reader is working on street
> > driven cars with a wide variety of exhaust and intake systems each changing
> > the optimum LSA.
>
> Last time i checked simply defining the LSA does not make a camshaft incompatible
> with a street engine. There is the ambiguous overlap portion of his method that will
> impact on these aspects such idle, part throttle, fuel economy etc
> [/quote]
>
> For given durations and acceleration rates, LSA determines drivability.
> DV said it is "the most important thing about spec'ing a cam"
> The notion that 2 inputs determine the LSA (and that it is the most important thing
> about spec'ing a cam) is absurd.
>
> The most important thing about spec'ing a cam is determining that it is compatible
> with the valve train.

The method proposed determines LSA and then an overlap number is chosen which gives duration. So it is not choosing a duration and putting it on the determined LSA. There is a very clear distinction.
The notion that it doesn’t consider more than WOT is actually completely wrong once you consider the second part of the method.
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Re: D V Live now.

Post by skinny z »

FWIW:

DV states the following:
"There are 5 parameters to be addressed when selecting a cam for best performance.
In order of importance they are: overlap, lobe centreline angle (LCA/LSA), advance/retard setting, lift and duration."

The 128 rule is used to determine one parameter, that being the LSA, in a finite number of applications.

Make of it what you will.
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Re: D V Live now.

Post by SchmidtMotorWorks »

skinny z wrote: Tue Nov 01, 2022 8:04 pm FWIW:

DV states the following:
"There are 5 parameters to be addressed when selecting a cam for best performance.
In order of importance they are: overlap, lobe centreline angle (LCA/LSA), advance/retard setting, lift and duration."

The 128 rule is used to determine one parameter, that being the LSA, in a finite number of applications.

Make of it what you will.
That isn't what he originally claimed.
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Re: D V Live now.

Post by skinny z »

That was first published in 1999 in How to Build Max Performance SBC's on a Budget. The again in the 2nd edition published 2009.

My disclaimer: I'm not saying right or wrong. I'm just laying out some facts.

Now with this YouTube thing going on, there's so much information spilling out, I can't say I've bothered to keep up.
It's all quite different now.
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Re: D V Live now.

Post by digger »

SchmidtMotorWorks wrote:
> [quote="skinny z" post_id=928688 time=1667347468 user_id=6881]
> FWIW:
>
> DV states the following:
> "There are 5 parameters to be addressed when selecting a cam for best
> performance.
> In order of importance they are: overlap, lobe centreline angle (LCA/LSA),
> advance/retard setting, lift and duration."
>
> The 128 rule is used to determine one parameter, that being the LSA, in a
> finite number of applications.
>
> Make of it what you will.
> [/quote]
>
> That isn't what he originally claimed.

definitely the journalist side came out in that early video (i.e. misleading headline statements). Definitely did not do himself any favours.
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Re: D V Live now.

Post by skinny z »

What video are you referring to?
It could be a full time job keeping track and I'd rather not.

On a similar note, one of DV's cohorts has a channel now and he was recently extolling the virtues of a tighter LSA.
I watched until his 3 cam test proved flawed enough for me to bail.
Kevin
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