I attended a dyno day and came 2nd in my class and 6th overall out of 56 cars, here is a pic of the results of 40 cars and the dyno graph, I snapped the dyno graph with my cell because I don't have a scanner, so the quality isn't good but I edited it a bit.
A Maha then?? One thing to watch is that dynos that determine the loss on their own sometimes do it via coastdown tests. That is flawed on an R since the Haldex goes to 0% coupling on coastdown.
A Maha then?? One thing to watch is that dynos that determine the loss on their own sometimes do it via coastdown tests. That is flawed on an R since the Haldex goes to 0% coupling on coastdown.
I think I am not sure what you saying
I am at the coast in any case or doesn't it matter? I see on the graph it also says there is a Ambient Correction of 1%
I am at the coast in any case or doesn't it matter? I see on the graph it also says there is a Ambient Correction of 1%
Dynos that determine the loss via some measurement typically do it by measuring the time it takes to coast down from a high speed to a low speed under no power and use that to come up with the parasitic loss in the drivetrain. With that loss %, they can take the TQ at the wheel and calculate the TQ at the crank.
The issue with the R is that under power, the Haldex can send 10 to 70+ % of the TQ to the rear axle but under coast down it sends 0%. The right angle gear set in the rear axle has loss but it will not be included in a coast down style measurement. Hope that helps you understand.
Yeah, higher is good but since the error is in a loss estimation the wheel HP remains the same. The bigger (more correct) number for crank HP is just useful for bragging (or advertising) rights. It means you started with more power but less of it got to the ground.
If it was that type of method, the loss % applied will be too low of a number and therefore your crank HP/TQ will be calculated low.
Not true. The driveline losses will be measured of both the front and the rear axle. Because there is no power transfer doesn't mean the rear doesn't have any resistance. The rear driveshafts, differential and input shaft will rotate. The cardan shaft will also rotate but the clutch isn't engaged.
What a MAHA type dyno does is measure drive at the front, drive at the rear, loss at the front, loss at the rear. In the end all is mixed and the result will come out.
Change to FWD only and the crank number output will be identical.
Like I said, these results replicate more or less what can be expected of a RON 95 measurement.
Johann, a rotating only bevel gearset does not have as much frictional loss as one transfering power. So although the delta may be small, there is a delta.
Proof can be found by driving a car with a worn ring/pinion. On acceleration and coastdown it'll howl like a wolf. Coast in neutral and it'll be very much quieter.
Johann, a rotating only bevel gearset does not have as much frictional loss as one transfering power. So although the delta may be small, there is a delta.
It is measuring so called negative power. the rolling resistance will load the drivetrain.
During a roll out you can see both axles being measured continuously.
Johann, a rotating only bevel gearset does not have as much frictional loss as one transfering power. So although the delta may be small, there is a delta...
Very true, Jim. That's why bevel gears get very hot only when transferring power, and why they are unsuitable for high power full-time rear bias application.
Does anyone know of an online photo or detailed drawing of the inside of the Volvo angle gear? Is it certain that it's a bevel design?
Tom.
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