dyno

[patrick cooper]

my vehicross 1997 3.2 jap model went on the dyno today i was running 285/85/16 bf goodrich mud train tyres and only produced 141.7 hp/5163 and 165lbf/ft/2854 rpm is this about correct as i have been reading that tyre size has a lot of diferance lowering the bhp as theirs a lot of weight in all that rubber and wots the total raito 6.328 mean on the dyno chart?

[tom4bren]

The weight of the tire isn't what's decreasing the dyno readings (well maybe a little). The larger tire is effectively changing the gearing of the vehicle. That's why a lot of off road rigs change the gears in their rigs when they run the big tires ... they are getting the power back to close (or better) than OEM specs.

The easy analogy is your speedometer. Running bigger tires means that your rig travels farther for each rotation of the tire, thus throwing off your speedometer (mine is off by 10% since I'm running 33x12.50's). Of course the torque and HP are similarly reduced.

I believe that the total ratio thing is that in the highest gear, the tires rotate 6.328 times for each rotation of the engine.

[Leon R]

The tire weight does matter, because that is how some dynos (DynoJet) create load

What brand dyno did you use? Was it a 4WD dyno? Did you have to do anything special to accommodate TOD?

[tom4bren]

Sorry, mine's never been on a dyno ... can't help you there. I was just wearing my Dr Sheldon Cooper hat for my response.

[SilverBullet75]

So that was your $.03 worth?
Get it? Penny... Penny... Penny

LOL I kill me.

[tom4bren]

ROFL

'Cept my Penny's name is Bren ... not sure how to factor that into the equation.

[Leon R]

Tom, the questions regarding dyno were addresses to Patrick

Different dyno brands tend to give you different figures. One really shouldn't quote dyno numbers without indicating what dyno was used.

[tom4bren]

Roger Leon ... Patrick?

[Vendetta]

Roger?


-V

[EVO]

Well we know who the Tuner Junkies are!! Just Joking! Dyno's from different manufacturers can and will read differently. Those of us motorheads have seen all kinds of different ones can attest Dyno's are great tuning tools for the tuner to benchmark the mods on a vehicle. That's why people will ask what kind of Dyno was she run on as some Dyno's consistently run on the high side. And some Dyno's make others cry!! LOL!!

[Leon R]

Patrick?

The original poster

I wonder how TOD behaves on AWD dyno?

[tom4bren]

The original poster

Yah, that was my feeble attempt at humor.

V got it ... rekin that doesn't say much for his sense of humor either.

[Leon R]

I think I get it .

THIS is how you report your dyno figures:

http://vehicross.info/forums/showpos...9&postcount=11



So looks like Patrick is only ~10hp off, which makes sense for a smaller engine.