Topic: Sigh..Inside Line Hyping the 2011 Mustang GT Horsepower...ERROR!!

[HeliDriver]

Here's an e-mail I received from Dynojet this morning:

Yes, gear ratio does matter, and ideally we suggest using the 1:1 ratio or as close as possible.

The simple reason is that in 1:1 your engines crankshaft and the  transmission should be running at the same ratio, thus the  most direct level of power delivery available.

The proof is simple to see, at the end of your run session, simply shift up or down a gear and make another quick pull. You may see a change in power.

There are some cases where this can be very dramatic, others not so much.

But the  1:1 gear ratio as a guideline is still preferred.
 

To me this implies that you could have more power loss by using a gear other than the 1:1, which AFAIK usually means that the input shaft is locked to the output shaft and not actually running through a gearset, hence the decreased loss.
Shifting up or down a gear means going through a gearset and accumulating more driveline loss, but how does it affect the  calculated power to read more as you are claiming?

Dynojet measures how much time it takes to spin a roller of a given weight.  When you use something other than 1:1, as you said there is a torque multiplication occurring through the gearset.  This skews the numbers.

I also interpreted the quote from Dynojet the same way blur did.

What about the example of two identical cars, identical engines, both with the transmission in a 1:1 gear, but one has a 2.83 rear end, the other has a 3.73. Obviously, there will be a big difference in the torque applied the roller, but I assume the dyno would still somehow spit out the same torque and HP numbers for each car?

[rrocket]

If I get a chance, I'll send Dynojet another e-mail.  All I know is...on all the dyno runs I've done (on a Dynojet) there is a variance if you are running anything other than 1:1, since AFAIK the dyno is calibrated at a 1:1 ratio.  Otherwise, why not always just do them in 2nd or 3rd...since the MPH you reach in those gears (55MPH+) are all you'd ever seen on the road.

I wish I could find a dyno sheet of a turbo diesel....I've seen one where same truck, same dyno, same session the TQ was 200+ TQ difference just by using a different gear.  And surely that's not from any drivetrain loss.  But again...turbos can behave a bit differently on the dyno.

[c2chung]

In their defense, I can't even think of another car that doesn't have fourth gear as 1:1. I am not sure but perhaps 6 speed FWD cars do not, but pretty much every 6 speed RWD car has two overdrives.

On the other hand, it's good to see Ford is finally putting a 6 speed in the GT, it's only about 15 years overdue.

If I remembered correctly, my E46 M3 comes with a 1:1 5th gear (4th at 1.23:1 and 6th at 0.83:1). FYI 

[No H2O]

On a Dynojet, it uses a mathematical equation based on the known weight of the rollers and acceleration of said rollers.

So I take it the Dynojet dyno cannot compute horsepower at a steady speed. I don't think I like their method. Problem with any other dyno is that it needs to be calibrated otherwise only a before-after comparison can be made.

[Triple Bob]

Here's an e-mail I received from Dynojet this morning:

Yes, gear ratio does matter, and ideally we suggest using the 1:1 ratio or as close as possible.

The simple reason is that in 1:1 your engines crankshaft and the  transmission should be running at the same ratio, thus the  most direct level of power delivery available.

The proof is simple to see, at the end of your run session, simply shift up or down a gear and make another quick pull. You may see a change in power.

There are some cases where this can be very dramatic, others not so much.

But the  1:1 gear ratio as a guideline is still preferred.
 

To me this implies that you could have more power loss by using a gear other than the 1:1, which AFAIK usually means that the input shaft is locked to the output shaft and not actually running through a gearset, hence the decreased loss.
Shifting up or down a gear means going through a gearset and accumulating more driveline loss, but how does it affect the  calculated power to read more as you are claiming?

Dynojet measures how much time it takes to spin a roller of a given weight.  When you use something other than 1:1, as you said there is a torque multiplication occurring through the gearset.  This skews the numbers.

So what happens if the final ratio isn't exactly 1:1, will every dyno test on that car either over or understate the power?

Somone draw me a engine/gearbox/final ratio diagram, I'm confused... 

[No H2O]

Somone draw me a engine/gearbox/final ratio diagram, I'm confused... 

OK...

[rrocket]

On a Dynojet, it uses a mathematical equation based on the known weight of the rollers and acceleration of said rollers.

So I take it the Dynojet dyno cannot compute horsepower at a steady speed. I don't think I like their method. Problem with any other dyno is that it needs to be calibrated otherwise only a before-after comparison can be made.

Correct.  WFO only.  Now with the Dynapak you can.  The Dynapak actually puts a load on each wheel, and can simulate regular driving conditions, going up a hill, towing a trailer etc..  They mount individual hydraulic motors on each wheel that provide resistance (load) to simulate real world..

[TopGun]

Has anyone said "Who Cares" yet?

[Snowman]

Has anyone said "Who Cares" yet?

 

[No H2O]

They mount individual hydraulic motors on each wheel that provide resistance (load) to simulate real world..

I wonder if they even bother to calibrate them periodically.