3V vs 2V dyno sheets
Cargo Master
Joined: Jun 2010
Posts: 2,113
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From: Iowa
I don't have a dyno comparison but I do have a real world comparison of two similar trucks. Dad has a 00 F250 2V V10 with 3.73s and 31" tires and I have an 06 F350 3V V10 with 4.10s and 34.5" tires making the effective gear ratio almost the same. Towing the same 20k+ trailer or empty the 3v V10 walks away from the 2V V10 without bearing the skinny pedal.... The comparison is slightly skewed by a superior transmission behind the 3V.
I'd like to see a good dyno graph comparison of the two engines as well.
I'd like to see a good dyno graph comparison of the two engines as well.
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Cargo Master
Joined: Apr 2013
Posts: 3,087
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From: Central Florida
Real world is better than dyno sheets.
But your story has so many variables that I can't wrap my head around it. Are you pretty sure about the tires/gear ratio comparisons being "effectively the same"
And I forgot about the better transmissions. Transmissions are nearly as important as the engine in the butt-dyno. My E van has a 5speed automatic and it is markedly better than a 4 speed.
But your story has so many variables that I can't wrap my head around it. Are you pretty sure about the tires/gear ratio comparisons being "effectively the same"
And I forgot about the better transmissions. Transmissions are nearly as important as the engine in the butt-dyno. My E van has a 5speed automatic and it is markedly better than a 4 speed.
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Joined: Jul 2002
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From: Long Island USA
Gearing and tire size are a simple multiplication and/or division problem.
If you currently have a 4.30 rear gear, and 35" tires, and want to find out what "actual" gearing you'd get with 33" tires, do this:
current tire size divided by new tire size, and multiply by gear. So it's 35/33*4.30=4.56
Conversely if you have 33" tires and a 3.73 and want to go to 35", it's 33/35*3.73=3.516, so you'd have what amounts to a 3.52 (rounded up) gear.
So if your engine puts out 350ft/lbs when you slam on the gas, and you're in first gear of a 4R100 (2.71:1 in first), and we assume the torque converter isn't doing anything (which it does, actually), and the rear gear is 3.73, and the tire size is 33", you do this:
350*2.71*3.73*(12/33)=1286.5ft/lbs to the ground. Of course, there is loss to friction, and spinning up the gears/driveshaft/wheels/etc, but you get the idea.
Speeds, RPMs, all of that.
Same idea - if you're going 2000RPM at 70mph with a 3.73 gear, and you want to see what the RPM would change to with a 4.30, it's 4.30/3.73*2000=2305.63
Or if you change tire size from 33 to 35, and want to see what RPM you'll run at 70MPH, it's 33/35*2000=1885.7
If you currently have a 4.30 rear gear, and 35" tires, and want to find out what "actual" gearing you'd get with 33" tires, do this:
current tire size divided by new tire size, and multiply by gear. So it's 35/33*4.30=4.56
Conversely if you have 33" tires and a 3.73 and want to go to 35", it's 33/35*3.73=3.516, so you'd have what amounts to a 3.52 (rounded up) gear.
So if your engine puts out 350ft/lbs when you slam on the gas, and you're in first gear of a 4R100 (2.71:1 in first), and we assume the torque converter isn't doing anything (which it does, actually), and the rear gear is 3.73, and the tire size is 33", you do this:
350*2.71*3.73*(12/33)=1286.5ft/lbs to the ground. Of course, there is loss to friction, and spinning up the gears/driveshaft/wheels/etc, but you get the idea.
Speeds, RPMs, all of that.
Same idea - if you're going 2000RPM at 70mph with a 3.73 gear, and you want to see what the RPM would change to with a 4.30, it's 4.30/3.73*2000=2305.63
Or if you change tire size from 33 to 35, and want to see what RPM you'll run at 70MPH, it's 33/35*2000=1885.7
Last edited by krewat; May 23, 2016 at 12:38 PM. Reason: bad math }>
Cargo Master
Joined: Jun 2010
Posts: 2,113
Likes: 4
From: Iowa
Math show off, lol.
If you know or can actually remember the formula to use it is actually very simple, I have the memory of an earthworm for formulas although I can figure it out if I have enough time so to be honest I cheated and used a tire/gear Calculator.
Dad's and I are about as close to identical as you can get two different model year trucks, even inside the cab. When we were towing together with identical trailers (35' GN flatbeds with hay) the 3V walked all over the 2v for power. Don't get me wrong Dads truck did an awesome job.
If you know or can actually remember the formula to use it is actually very simple, I have the memory of an earthworm for formulas although I can figure it out if I have enough time so to be honest I cheated and used a tire/gear Calculator.
Dad's and I are about as close to identical as you can get two different model year trucks, even inside the cab. When we were towing together with identical trailers (35' GN flatbeds with hay) the 3V walked all over the 2v for power. Don't get me wrong Dads truck did an awesome job.
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Looking at it a different way, by dividing the tire sizes you are making a percentage (in decimals. .50 is 50%, .45 is 45% and so on) you then take that dived percentage (say you are going from 33 to 35tires) 33/35=.942 or about 94%. Multiplying any number by .94 will give you 94% of that number. So by going up in tire size from 33 to 35 you have cut your gear down to 94% of what it once was. In the case of the above 3.73 gear, the increases in tire size from 33 to 35 nets a new effective gear of 3.50.
Note: Krewat above has 3.52 which IS more accurate. My rounding to .94 (which was actually .94285) took it down to 3.50. If I use .94285 x 3.73, then I get 3.5168 which rounds to 3.52. Use Krewats equations to get the exact numbers. The purpose of this was to look at it from a different perspective to better understand how the math works.
Note: Krewat above has 3.52 which IS more accurate. My rounding to .94 (which was actually .94285) took it down to 3.50. If I use .94285 x 3.73, then I get 3.5168 which rounds to 3.52. Use Krewats equations to get the exact numbers. The purpose of this was to look at it from a different perspective to better understand how the math works.
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, 5-Star has dyno charts and tuning info for the V10 here:Got a 1997-2010 V10 6.8L? - 5 Star Tuning
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