ThisBlood147

Ok, I posted this in the General Tech section where it should be.....but got no usable input.

Ok, I had my first dyno done yesterday. I'll admit, I'm not very knowledgable about these dyno machines and such. So I have to ask, what is the difference between a Mustang dynamometer (which is what my car was done on) and a Dynojet? I know the mustang dyno's readout less than the dynojet, but what are each of these test machines measuring? And typically how much above a mustang dyno readout will a dynojet readout be?

And just to ask yet one more question....what do most of you guys quote for your hp ratings: mustang dyno numbers or dynojet?

drbobvs

This has been explained to me in grat detail about 3 times by Dan at Realspeed. And everytime, I completely forget what he said. Sorry.

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Sleeper05

a dynojet measures how fast the far spools up the roller versus how many times the engine turns over, and is very accurate at that. however, when you drive your car on the road, there are a number of forces like WEIGHT that are unaccounted for in the calculations. a mustang dyno "loads" the roller(s) based on the vehicles weight and other factors, which make it harder to spin the roller as fast, resulting in a lower reading by about 10% usually.

i go by my mustang dyno numbers because they are by far the most reliable and consistant across the board from shop to shop, and to real world driving. its also gratifying to beat a 350rwhp (or more) car and when they ask to say 300rwhp. i liken it to my days in car audio where i always rated a system by RMS (root mean square, aka "average continuous") power, and when it blew the crap out of a system with twice as much power (because the guy went by peak numbers instead), i would chuckle at the fact he had no idea how much power his amps actually put out.

this touches the surface of the differences, as i am not an expert on the detailed workings of both machines

GhostPony

The interesting thing I read recently in MM & FF about the Dynojet chassis dyno is that the horspower readings are based on an "estimated" mathematical calculation. Inventor was using his dyno to tune constant velocity carbs. He based his calculations on a Yamaha VMax 1100. He basically had his people wing a formula to have the dyno read the expected amount of horsepower, based on what he thought the Vmax was pushing out. All subsequent Dynojet models (bike & auto) use this same calculation he originally used on that Vmax.