[john marcella]

Originally Posted by Daniel Barton

and Chris yours is surely not the only time I've heard someone say they haven't seen it... Just because someone has not yet seen something sure doesn't mean it doesn't exist!

So with your experience , how often does this phenomenon occur? Because in my experience the topic only arises with subpar dyno sheets and or unexpectedly high dyno sheets.


And I myself have not seen a motor make more average power and not accelerate down the track faster.

[Daniel Barton]

I have been around dyno's for almost every day of the last 23 years, I have seen it more than 5 and less than 10 times that stick out in my mind. All where on fairly developed competition eliminator engines, all of which held the record in there respective classes at one time or another. Again, just because you have yet to see or recognize this does not mean it doesn't exist. I personally haven't seen the pyramids in Egypt, but I believe they exist. You guys may have not seen it strictly by a numbers basis, you aren't around the dyno enough yet.

[john marcella]

Originally Posted by Daniel Barton

I have been around dyno's for almost every day of the last 23 years, I have seen it more than 5 and less than 10 times that stick out in my mind. All where on fairly developed competition eliminator engines, all of which held the record in there respective classes at one time or another. Again, just because you have yet to see or recognize this does not mean it doesn't exist. I personally haven't seen the pyramids in Egypt, but I believe they exist. You guys may have not seen it strictly by a numbers basis, you aren't around the dyno enough yet.

Ok, i would not argue that. I can see it.

[john marcella]

But still why do you feel that the mph is more of a validation of hp than a dyno that is designed to do just that, when it seems clear that you do not factor all of the variables that come with a particular vehicle. Imo it would be almost impossible to " accurately" calculate the true or total CD of a particular vehicle unless you were Ford GM or Chrysler or had their resources.

[Daniel Barton]

Originally Posted by john marcella

But still why do you feel that the mph is more of a validation of hp than a dyno that is designed to do just that, when it seems clear that you do not factor all of the variables that come with a particular vehicle. Imo it would be almost impossible to " accurately" calculate the true or total CD of a particular vehicle unless you were Ford GM or Chrysler or had their resources.

Because it allows for the intangible of acceleration, which I have seen and believe to be a very real issue. I believe you can be fairly accurate with those variable without having those resources at the level we are dealing with. 169-170 is a far less issue than 210, 250,300, etc...

[john marcella]

Originally Posted by Daniel Barton

Because it allows for the intangible of acceleration, which I have seen and believe to be a very real issue. I believe you can be fairly accurate with those variable without having those resources at the level we are dealing with. 169-170 is a far less issue than 210, 250,300, etc...

Acceleration is et not mile per hour.

And so are we wasting our money on such things as front air dams, closing off the grill, $8000 transmissions ,ceramic bearings on the wheels and 3rd member and so on....?

Now with that said i am looking for a range of et and mph out of a car for a particular dyno sheet, every time. But not to validate dyno numbers. More to see what is left to chase in the car and set up.

[Daniel Barton]

I never said any of that is a waste of money or time. You ever seen a graph of a car in high gear that looks like a horizontal line? I have, wasn't my stuff but some strange things were done to the engine to show big power and not accelerate good, guess what? It would not mph anywhere near what the dyno showed for power to be. When someone is racing at this type of level I guess I might sometimes assume that the basic aero things have been addressed. Probably not always the safest assumption to make on my part but for the purpose of this discussion I don't believe we are wondering about 1 to 1 1/2 mph.

[Daniel Barton]

Also I might add that the engines ability to accelerate back from a launch or recover from a shift is what I am talking about, if you don't believe that this will have an affect on mph as well as et I believe that you are mistaken. It needs to accelerate hard from 0-1320.

[john marcella]

Originally Posted by Daniel Barton

Also I might add that the engines ability to accelerate back from a launch or recover from a shift is what I am talking about, if you don't believe that this will have an affect on mph as well as et I believe that you are mistaken. It needs to accelerate hard from 0-1320.

Agreed, but agian that would be an average power thing,and it should show that on the sheet.

[mike leech]

Originally Posted by Daniel Barton

I have seen it...

Originally Posted by Daniel Barton

for the purpose of this discussion I don't believe we are wondering about 1 to 1 1/2 mph.

So I'm curious about how many mph we are "wondering" about?

[Daniel Barton]

Originally Posted by john marcella

Agreed, but agian that would be an average power thing,and it should show that on the sheet.

Not 100 percent of the time...

[Daniel Barton]

Originally Posted by mike leech

So I'm curious about how many mph we are "wondering" about?

Clearly more than 1 to 1 1/2 like I said... We aren't talking about something that shows within 20 or 30 horsepower as that could be more easily excused away by aero issues, that is kind of my point.

[mike leech]

Ok.

[cosgrove]

Dyno operators know what the "expected" loss will be when increasing acceleration rates. A higher loss than expected could predict how an engine will perform on the track. Most of us, however, have much more important work to accomplish on our limited dyno time.

[john marcella]

Originally Posted by Daniel Barton

Not 100 percent of the time...

Hahaha voodoo.

So it has happened 5 to 10 times over every day of 23 years of dyno time, and you are making this big of a deal about it? I dont get it? Sounds like you have a taste for voodoo Kool Aid.

In the end we all have our own way, results are what counts(not methods) and those are found at the track, not dynos or flow benchs.

[Stan Weiss]

Originally Posted by Daniel Barton

I never said any of that is a waste of money or time. You ever seen a graph of a car in high gear that looks like a horizontal line? I have, wasn't my stuff but some strange things were done to the engine to show big power and not accelerate good, guess what? It would not mph anywhere near what the dyno showed for power to be. When someone is racing at this type of level I guess I might sometimes assume that the basic aero things have been addressed. Probably not always the safest assumption to make on my part but for the purpose of this discussion I don't believe we are wondering about 1 to 1 1/2 mph.

Originally Posted by cosgrove

Dyno operators know what the "expected" loss will be when increasing acceleration rates. A higher loss than expected could predict how an engine will perform on the track. Most of us, however, have much more important work to accomplish on our limited dyno time.

cosgrove,
He is talking about the opposite here. A very high load very slow acceleration rate condition.

Dan,
Was this a very small engine high lbs per ci type class?

Stan

[Motor Daddy]

Originally Posted by john marcella

Acceleration is et not mile per hour.

Acceleration is the rate of change of velocity.

See?

[John Langer]

It is all about acceleration. Would a motor with a very light piston,pin,rod combination accelerate faster then a motor with a very heavy piston,pin, rod combination? I'm not talking about gram differences but pounds. They could make the same power on the dyno since the dyno limits acceleration but one would go faster on the track. Same goes for cylinder head and intake design. Dynos limit the acceleration of a motor but the motor accelerates the car.

[John Langer]

Acceleration is also Newtons 2nd law of physics.

[Motor Daddy]

Originally Posted by John Langer

It is all about acceleration. Would a motor with a very light piston,pin,rod combination accelerate faster then a motor with a very heavy piston,pin, rod combination? I'm not talking about gram differences but pounds. They could make the same power on the dyno since the dyno limits acceleration but one would go faster on the track. Same goes for cylinder head and intake design. Dynos limit the acceleration of a motor but the motor accelerates the car.

The car limits the acceleration of the motor too, no? The air limits the car too, no? Gravity too? Friction? Rolling resistance from bearings? U joints/angle torques? ...

HP=Torque*RPM/5252
ET= What the timeslip indicates. (Note: A timeslip is a record of the past. It already happened and the time elapsed.) Knowing HP from ET is virtually impossible.