Questions about David Vizard 128 Rule and Dyno Tests

[HQM383]

All the DV haters/detractors carry on about DV & his 128 rule, but as yet I have not seen ONE test that has disproven 128. Lots of noise & fluff. Nor have I heard of anybody who tested 19,000+ cam profiles, which is where the 128 rule originated.

DV has alway said his cam selection formulas are to select the ‘optimum’ cam.

Define optimum in this instance?

A guy who calls himself the 'Cattle Dog Garage' tested the 128 rule to see how good it was. It is a You Tube video, goes for 34 min [ not the 1hr + video ]. Sorry, do not know how how to link.

What was it tested against?
What was his test method?

https://youtu.be/E-1A2Sp7Axg?si=f1U6gcn-uamNnP1H

[bob460]

For the DV lover's........

https://www.youtube.com/watch?v=bgmgg-dpJsU

[steve cowan]

Sums it up in 2 minutes 37 seconds.

[HQM383]

For the DV lover's........

https://www.youtube.com/watch?v=bgmgg-dpJsU

https://youtube.com/clip/UgkxWc_X9YVvxg ... Ul0JEPqn2v

https://youtube.com/clip/Ugkxd76otsxTb6 ... Ry0dxypGjn

[rgalajda]

"ad nauseum". Use ad nauseam to describe something that's been repeated or discussed so long that you're sick of hearing about it.

Here"s another one.
Some people should carry a plant around to replace the oxygen they waste.

[hoffman900]

As a numbers / STEM guy, you can make a lot of different combinations of two numbers (IVO+IVC, EVO+EVC) have the same average (ICL, ECL), and THEN take the average of two averages (LSA).

LSA is an average of averages. It doesn’t tell you a lot and anyone’s knowledge of it is just being forced fed the same combinations of engines (383-400ci vintage 2 valve engines, around 10:1 compression, etc). In a knowledge vacuum, and if you had to restart, you would never teach yourself to look at the average of averages for trends.

Also, a lot of these dyno graphs start at 35-3600rpm and end at 6200-6500rpm. On a street engine, you’ve cut off nearly half the rpm range you’re going to see, and none of these tests consider part throttle.

[Stan Weiss]

Also, a lot of these dyno graphs start at 35-3600rpm and end at 6200-6500rpm. On a street engine, you’ve cut off nearly half the rpm range you’re going to see, and none of these tests consider part throttle.

Bob,
You say a lot. I say almost every dyno test no matter how the cam was selected is no more that a 3000 RPM sweep.

Stan

[hoffman900]

Also, a lot of these dyno graphs start at 35-3600rpm and end at 6200-6500rpm. On a street engine, you’ve cut off nearly half the rpm range you’re going to see, and none of these tests consider part throttle.

Bob,
You say a lot. I say almost every dyno test no matter how the cam was selected is no more that a 3000 RPM sweep.

Stan

You should measure how the engine is used.

Here is a BMW S1000RR chassis dyno graph from Akrapovic. On the street you’re in the 2000s. On a race track, you might be as low as 5-6000rpm in a tight corner.

I drew in what a 3500-6500rpm looks like.

43EA9010-A4C9-4AF8-BD79-7637084A5FF2.jpeg

Sure, everything to the right probably doesn’t matter, but left of those lines does for what applies to most people.

[Stan Weiss]

Bob,
I was talking engine dynos. Many here are running an automatic trans and with their loose convertors, I don't think you would get very much useful information at the low RPM on a chassis dyno.

Stan

[hoffman900]

Stan Weiss wrote:
> Bob,
> I was talking engine dynos. Many here are running an automatic trans and
> with their loose convertors, I don't think you would get very much useful
> information at the low RPM on a chassis dyno.
>
> Stan

There’s a bigger world out there than Turbo400s and lurching high stalls in autos

[Stan Weiss]

Stan Weiss wrote:
> Bob,
> I was talking engine dynos. Many here are running an automatic trans and
> with their loose convertors, I don't think you would get very much useful
> information at the low RPM on a chassis dyno.
>
> Stan

There’s a bigger world out there than Turbo400s and lurching high stalls in autos

Bob,
Yes it is true there's a bigger world out there. But I try to focus on what most people here on Speed Talk maybe dealing with.

Stan

PS - I would be interested to know how many people here would want to see the tech from a 24 hours of Daytona car versions a Drag Week car.

[skinny z]

In so far as 128 is concerned, and this is where I was called out by DV (although yet to receive a reply to his PM) , what IS optimum?

It's been asked more than once although there's only one person who can correctly answer that question.

Seems to me, right or wrong, that the emphasis has always been on torque production. WHERE that torque is produced is not part of the "formula". It's simply the most that can be had within the confines of the inputs.
Rev range would be engine component specific as the TM program would demonstrate by using the port CFM as a guide. Among others.
But torque production always seem to rise to the top when discussing DV and /or his methodology.

[skinny z]

As for Daytona vs Drag Week, I'm all ears.

[HQM383]

skinny z wrote:
> In so far as 128 is concerned, and this is where I was called out by DV
> (although yet to receive a reply to his PM) , what IS optimum?
>
> It's been asked more than once although there's only one person who can
> correctly answer that question.
>
> Seems to me, right or wrong, that the emphasis has always been on torque
> production. WHERE that torque is produced is not part of the
> "formula". It's simply the most that can be had within the
> confines of the inputs.
> Rev range would be engine component specific as the TM program would
> demonstrate by using the port CFM as a guide. Among others.
> But torque production always seem to rise to the top when discussing DV and
> /or his methodology.

Optimum

Let's say down here in the merry old land of Oz there are two guys building engines fit their cars. Both are 383 ci, both are using the same head, same compression ratio. Both cars are the same make and model of car and same transmission. One guy is setting up for 1/4 mile et and the other more street oriented. Guy 1 has 5.5k converter, 4.56:1 gears and 28" tire. Guy 2 has 4k converter, 3.7:1 gears and 26" tire. Are both of these guys 'optimum' cam the same cam?

[skinny z]

It's a fair bet that the rev ranges are different however they could very have the same LSA.
128 doesn't spec a cam, it determines a best lobe seperation. The rest of the spec comes from influences outside the 128. But the "rule" is built around CR, CoD of the intake valve (or valve diameter), CID.
At least that's how I understand it.
And I'll say it again, I'm neither here nor there on the viability of the rule. I'm just trying to relay the facts as I've observed them. Virtually that is.