Would it make a difference in the HP if u dyno'd ur car on the second gear or the third gear?

AND why dont they do the dyno run at the First gear?

------------------
Gold CL-S with comptech headers, mufflers,Springs, V-AFC,AEM CAI. ACE hyper black Wheels 235-40-18ZR.
In the future..Supercharger or turbo if there is any.
Gtech run 0 to 60 in 5.41sec

My car pics are On http://albums.photopoint.com/j/Album...521&a=11013539

 

I know that this WILL matter in a turbocharched application because boost takes time to built. So having third gear in makes it easier for the engine to show its full potential since rpms are taking more time to raise than in 2nd or first.

In our case, I would think that 2nd gear would be fine. First would a little to dramatic because it loads up too fast and there might be slippage and other factors taht would steal HP. Third gear would probably not make much of a difference I would think either.

------------------
Gabriel
CL Type S

 

This is where engine dyno's are better at determining the exact HP.

On chassis dyno's, like the Dynojet many of us have used, measure hp at the wheels. It does this by calculating how quickly your car can accelerate a known weighted drum, what your wheels are on. It doesn't actually use a torque sensor (slip ring torque transducers, etc. are used in engine dyno's).

Gearing will have an effect on the numbers on a chassis dyno. This is why all chassis dyno's try and run the car in a gear that is closest to an overall ratio of 1:1. Lower gears, higher numerically, may show a higher than actual value and higher gearing the opposite.

So when comparing runs on a particular car, be sure both were done in the same gear.

BTW, 3rd is our closest.

 

So if i want to dyno my car again .. i should tell them to use the third gear.. because the first one was on the second gear.

------------------
Gold CL-S with comptech headers, mufflers,Springs, V-AFC,AEM CAI. ACE hyper black Wheels 235-40-18ZR.
In the future..Supercharger or turbo if there is any.
Gtech run 0 to 60 in 5.41sec

My car pics are On http://albums.photopoint.com/j/Album...521&a=11013539

 

Steve, Is there anybody out there that makes or is trying to make a version that does not use "spin-up" to measure power dynamically? I would think someone could build a unit with a set of strain-gauges hooked between a very light load roller (kill the dynamics) and get step-by-step torque readings and convert to hp (via the engine's rpm).

You are the car expert, does some one make it? If not is there a good reason not too?



------------------
2001 Satin Silver Cl-S w/ Navi.
Mud Guards.
Wheel locks
Toyo 235/45ZR17-97W*
T1S Proxies on Stock 17" CLS wheels
Gtech 1/8th tank 40F ~=6.1

 

Scalbert are you sure about that? That turning drum is all about torque in my opinion. Torque is power in a twisting mode (i know you know this) which looks like what that drum is doing. Even if it is measuring how fast your wheels are turning that drum, it is still a torque measure. No?



------------------
Gabriel
CL Type S

 

Here is a link to a dyno maker in New Zealand that "seems" to make a set of units that don't get messed up my wheel weight, etc. It looks like they can do static load measurement, 4 wheel drives, 2 wheel drives, etc. I think these guys are not depending on the acceleration of the drum (as so said by Steve). But they aren't DynoJet.

http://www.dynopack.co.nz/operation.html

Check out the lowest picture and caption:




[This message has been edited by EricL (edited 01-25-2001).]

 

Steve can probably answer best, but here is a link to a DynoJet info page. They use inertial measurement. So, they are not directly measuring the "force". They are measuring the acceleration of a drum. So, someone with 18" wheels (etc) will not get an accurate reading of HP/torque. You decide, here is the link:

DynoJet Theory

Check out the section heading: "Torque".

Anyway, Scalbert seems to be the new sensor master...



------------------
2001 Satin Silver Cl-S w/ Navi.
Mud Guards.
Wheel locks
Toyo 235/45ZR17-97W*
T1S Proxies on Stock 17" CLS wheels
Gtech 1/8th tank 40F ~=6.1

 

The idea of gearing is to make you existing power more useable. Why not have direct connections from the crank to the differential?? Because if you have to move along at any speed worth while, your final drive ratio wouldn't allow you to get off the line.

You never have as good of acceleration in 4th gear as in 1st, the reason is not all about drag. Much is still in that the lower gears provide more torque to the wheels.

This is not unlike the issue of wheel size. Go to an overall large diameter (regardless of weight) and your measured torque at any given RPM will be less:

Wheel&Tire Radius / 12 * Torque at Axle = Torque at Ground

The reason is that the final overall drive ratio has changed. Same applies in various gears, the over all ratio is different.

As for a chassis dyno that would be affected by gearing that I can't say. I have never seen one, but there are always engine dyno's, JK. That would be fun, yank the engine just to determine true crank HP...