Prob been on here before but I thought it was kinda neat although prob not very accurate.
http://www.mk5cortinaestate.co.uk/calculator4.php
http://www.mk5cortinaestate.co.uk/calculator4.php
Hp Calc
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Grabbin' Asphalt
5 Year Member
Do the math for me, what's this thing claiming percentage wiseI've been lead to believe that a manual trans looses 12-15% to the rear wheels.
Grabbin' Asphalt
5 Year Member
for my 5spd it was 280/337= .830 so 1-.830= 17% loss ...i would say that's pretty darn close.
but little does that crank do-hicki know i gotta little "cool ram-air juice" to knock that % down a tad when i'm hitting the streets
but little does that crank do-hicki know i gotta little "cool ram-air juice" to knock that % down a tad when i'm hitting the streets
Grabbin' Asphalt
5 Year Member
The problem with trying to convert rwhp to flywheel hp is that each drivetrain is different so you can't assume that all RWD manuals have a drivetrain loss of 15% and that all RWD automatics have a loss of 20%. Losses of 15-18% for manuals and 20-23% for automatics were probably true on older vehicles.
The drivetrain loss of modern RWD manuals is probably more like 10-12% with a loss of ~15-17% for automatics. FWD cars have a ~5% smaller loss because there's no driveshaft and the drivetrain is more compact.
I've created a calculator that'll estimate rwhp from vehicle "race" weight and 1/4 mile trap speed, and it's probably the most accurate that you'll find:
http://www.angelfire.com/my/fan/WHPCalculator.htm
The drivetrain loss of modern RWD manuals is probably more like 10-12% with a loss of ~15-17% for automatics. FWD cars have a ~5% smaller loss because there's no driveshaft and the drivetrain is more compact.
I've created a calculator that'll estimate rwhp from vehicle "race" weight and 1/4 mile trap speed, and it's probably the most accurate that you'll find:
http://www.angelfire.com/my/fan/WHPCalculator.htm
The T5 has a drivetrain loss of ~13% so it's pretty close to more modern trannies.
The T5 is definitly not modern. Mine is 25 years old. LOL
The above calculator has manual drive train loss at right around 17.5%, not 13%. According to that calculator, my 285rwhp works out to be 335.
My math says 17.5% =334.87. I've always read and have been told 15-18%. So that sounds about right to me.
Anyway, Who cares what it makes at the flywheel. Wheel horsepower is all that matters in the big scheme of things.
That's one example but I meant any 3-speed auto or 4-speed manual tranny from the 60's & 70's (perhaps 80's too). The AOD/AODE also fall into that category despite being more "modern" 'cause they're little more than an old C4 with an overdrive gear.
285/335 = 0.85 so it's actually a 15% drivetrain loss for that calculator. That 15% figure probably applies to earlier 4-speed manual trannies. The T5 5-speed is a bit more efficient than that.
The same calculator also assumes a 17% drivetrain loss for a modern RWD automatic which is the same as what I mentioned previously.
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