First Dyno Run
02-28-2005, 02:39 PM
#16
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My bone stock truck: 237/437
Another bone stock 2004 HO Dually that dynoed right after me: 237/437
Don't think they make that much of a difference.
Runs were on a dynojet in 12/03.
John
Another bone stock 2004 HO Dually that dynoed right after me: 237/437
Don't think they make that much of a difference.
Runs were on a dynojet in 12/03.
John
Originally posted by Don M
The dual wheels take away anywhere from 20 to 35 HP on a DynoJet. Add a transfer case and it gets worse. We have tested it all on the Dynojet. Its how fast you can spin the roller. The less weight you have to get spinning, the better.
The best truck to have for dynoing is a 2WD, single rear wheeler.
Oh big tall and heavy off road tires make it even worse.
Im stuck with a 4x4, Dually myself.
Don~
The dual wheels take away anywhere from 20 to 35 HP on a DynoJet. Add a transfer case and it gets worse. We have tested it all on the Dynojet. Its how fast you can spin the roller. The less weight you have to get spinning, the better.
The best truck to have for dynoing is a 2WD, single rear wheeler.
Oh big tall and heavy off road tires make it even worse.
Im stuck with a 4x4, Dually myself.
Don~
02-28-2005, 02:54 PM
#17
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We rarely agree, why should today be any different? 
Since I have the time to dyno my truck with both rear tires/wheels and with only one rear tire I can safely say the extra wheel hainging off changed things by 17 HP. That was at 430 HP.
The same day we had set of 315 tires and set of 265's. The 315's cost the truck 16 HP. Same truck ( a single rear wheel 99' at 495 HP ) made 511 with the 265's.
Both are 5 speed trucks.
Don~
Since I have the time to dyno my truck with both rear tires/wheels and with only one rear tire I can safely say the extra wheel hainging off changed things by 17 HP. That was at 430 HP. The same day we had set of 315 tires and set of 265's. The 315's cost the truck 16 HP. Same truck ( a single rear wheel 99' at 495 HP ) made 511 with the 265's.
Both are 5 speed trucks.
Don~
02-28-2005, 02:59 PM
#18
Registered User
Ok, so a truck making 430 hp saw 17 hp difference between having both rear wheels on each side and only having one. It's pretty safe to say that truck's wheels and tires had to accelerate a lot faster than the wheels and tires of a truck at stock power levels. That being the case, doing the same experiment on my stock truck should yield a power loss with the duals, but less than the loss the 430 hp truck experienced. Of course, all this matters very little once you get going down the road, because there is no rapid acceleration like you see on a dyno at road speed. You could try duals/singles on an eddy current dyno, one capable of holding the drum at a constant speed. You will see the "loss" drop to near zero with the dual wheels.
02-28-2005, 03:06 PM
#20
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Originally posted by PourinDiesel
Those numbers are fine.
Those numbers are fine.
You would be amazed at how much some dynos are different, and how some calibrations make different power.
20-30 HP +/- often isn't really +/-, it's dyno variance.
Also, the truck will make different power loaded vs unloaded, or with different EOT, IAT, gear, tire size, etc, etc, etc...
Using a superflow everyday (the ONLY way to dyno a diesel), I've always quoted out of silliness: "Your Dynojet is a Liar!"
Dyno runs are for comparison, and not for comparison from one dyno to another, but for the same vehicle or comparing different vehicles on the SAME dyno.
I might make 300 HP here, and billy bob made 320 on the other side of the country, but my truck might still be faster...
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