chassis dyno

[astikhossw]

Can anyone tell me if a chassis dyno multply the torque of the drive train and give you the results are does it some how give you the engine results.

[Mike Taylor 3601]

It gives power @ wheels ,I know on Dynojet they have setting that after pull put car in neutral and let driveline and dyno drum coast and it calculates % driveline uses. Dynojet told me figure 25% at least. If you have reverse pattern valve body don't attempt going back to neutral.
Mike Taylor3601
I looked at your post again I may have misunderstood your question chassis dyno calculates HP by how fast you accelerate the drum thats how they measure Dynojet has 3500lbs. drum.Engine dyno has whats called torque link attachted to dyno brake which calculates TQ.torque link is stretched and calculates TQ. from amount of stretch of tq link and converts HP from that,Super Flow now calls them load cells.

[Run to Rund]

Some chassis dynos measure torque and then calculate HP. The Dynojet measures HP directly, and uses the tach pickup to convert roller speed (which calculates mph) into rpm for torque. The Dynojet can be used for coast-down HP measurements and comparisons of the drag from different things like diff designs (e.g. 12 bolt vs. 9" ford), or lubricants.

[Mike Taylor 3601]

That's what I was trying to say but you did better job.
Mike Taylor3601

[Robert Swartz]

I'm curious about this. I have always been under the impression that you can't use a chassis dyno on a car with slicks? I may be completely wrong, since drag slicks grow, they would seem to be unstable on one of these rigs. Or am I completely out in left field?

[Robert Simpson]

I would like to know how a test is conducted on a roller dyno? For example a stocker with a loose converter. How do you run a test with reading down low, 3500rpm, on up with a converter that slips and flashes, etc? The couple operators I have spoken with around here have no idea what I mean, then again they mainly run imports and manuals.

[art leong]

Originally Posted by Robert Simpson

I would like to know how a test is conducted on a roller dyno? For example a stocker with a loose converter. How do you run a test with reading down low, 3500rpm, on up with a converter that slips and flashes, etc? The couple operators I have spoken with around here have no idea what I mean, then again they mainly run imports and manuals.

I have been there done that. The dyno results were basicly from 5500 up. They gave me the car back so lean at an idle to 5000 It would even start cold, But it made power at the high end.

[art leong]

Originally Posted by Robert Swartz

I'm curious about this. I have always been under the impression that you can't use a chassis dyno on a car with slicks? I may be completely wrong, since drag slicks grow, they would seem to be unstable on one of these rigs. Or am I completely out in left field?

Some chassis dyno tear up soft rubber slicks.

[Rob Petrie E395]

I dont know exactly how they work but my bracket car has been on a chassis dyno a bunch of times. Every time with the same Hoosier slicks that I race with at the same pressure I run down the track with and never a problem. I would think if you were trying stuff on the car to find more HP or TQ as long as you did not mess with air pressure it should repeat ok and you would be able to tell if the engine changes made a difference.

[Chris "drooze" Wertman]

Originally Posted by astikhossw

Can anyone tell me if a chassis dyno multply the torque of the drive train and give you the results are does it some how give you the engine results.

There are many different types of "Chassis Dyno's" just like engine Dyno's

There are "Inertia" Dynos which guess at HP and Torque based on calculations of what the drum weighs or resistance and how much it takes to do that, some very accuratley

There are "Load Brake" Chassis Dyno's or Hub Dyno's that bolt to the axle like a wheel would, some are Hydraulic Load brake Dynos, just like and engine dyno, these can be "hyperaccurate" as in seeing gap changes, Dynapac is one, and if you look at their site they have a listing of places here in the states that have em, they also have other advantages. You can actually simulate a "Pass" or Full accel ramp, they are also easier on the Chassis and "Safer" do a search on youtube for "Dyno Accidents" some are funny as hell, some very very sad (in loss of iron) These are much more accurate on torque, but calculate HP based on Torque (a mathmateical equation)

There are other types as well, but those are the main 2

Dono if that helps, my limits of knowlege on Car Chassis Dyno's