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Thread: Drivetrain loss for dummies!!!!

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Posts: 21-26 of 26
2010-09-07 21:13:19
Originally Posted by BenFenner
keelay have you ever seen data from an engine on an engine dyno and then later seen the output as measured by a chassis dyno (with no other variables changed)? I'd love to hear about your data if you have any.

As for Ashton, he's a smart guy. I don't think you've given him enough credit. I'd have thought that same thing if I'd seen the data he's seen assuming the dynos are known quantities.

I have. The only one (I know I need more experience there...) But it was severely skewed. It was a mildly built 514 cadillac. Torque numbers were in the mid 700's and I want to say it sitting about 470ish hp. With a powerglide behind it, it was putting down something in the 410's (dynojet). That has been about 5-6 years ago, and I can't really remember exact numbers. I MAY be able to get you some data though from some people I brainstorm with. I will try sir

I have no doubt he's a smart guy, and it's been evidenced by his posts. He has the first few prerequisites necessary to be very good. He has an idea what's going on, and even formulates his own theories (which most people can't fathom, and just blindly sheepishly follow what they're told). He is receptive, and seems to have the capacity to accept other possibilities other than what he originally had thought. That's why I put that disclaimer in. I in NO way meant that in an insulting manner, and apologize if it came across as so. Also, given the data he's encountered, he's on the right track, just misguided a little. But given limited data, (and taking what others told him as fact) he's come up with his own idea, which is a BIG plus. If more people were as freethinking as he, we'd have some really bad ass stuff on the roads.
Good job for thinking for yourself. Don't be afraid to break the norm, and don't be afraid to be wrong. You can only learn from it. Which is the entire point of this whole hobby.
2010-09-07 21:17:41
Originally Posted by Ken's
I don't know much on this subject but, my good buddy with a 4g63 made 1100hp at the crank on an engine dyno, then made 810hp at the wheels. The car is a 70's monza with a powerglide and 6000rpm stall. He ran the same boost, but had to change the tune a bit from engine dyno to chassis dyno.

This is on instance where he was hoping for much better whp. He is taking it to the track tonight to hopefully run some mid to low 9's.

NOT to be a douche, but please do not bring in "my buddies" stuff in here unless you've had a hand in the build and KNOW the EXACT details of EVERYTHING involving the setup. We don't want to clutter this thread with speculation, and "I know someone that did it" or "I read on the internet..." bull crap.
Please keep this to FACTUAL circumstances that you are fully aware of all factors. If you built it or ran the dyno, then by all means share your experience. But if you were a fly on the wall while it was happening, or just saw a dyno sheet, don't add it here until you can give further in depth details.
Thank you, and I seriously don't mean to sound hateful, just don't want to clutter this thread.
Also, have fun at the track, and good luck with your 9sec goal. Stay safe bro!
2010-09-07 21:30:32
Thanks man. Thats why i made this thread to begin with. Its one of those subjects that has soo many variables mixed in that its hard. I just point out some obvious numbers that havent been known to be skewed or exagerated.

Motortrend is one of those that has been known to exagerate numbers and this is where the GTR example comes into play. They went on to say that because the GTR put down 431awhp that it has to be making in the neighborhood of 520-580 crank hp not the 480 crank hp it was claimed to have.

This was doing a 15% and 25% drivetrain loss addition to what it put down. Again where they think they get off just throwing out a 60hp difference like its nothing is beyond me and stupid at that and to say that because it performs soo well for its weight and hp that it must be making more power than what was advertised. 60hp isnt just somethign you toss around. I mean 60hp is a lot even at the 500hp mark. Its a big chunk of power. they throw it around like its lasily.

I can see exactly how the GTR has 480 crank hp and lays down 430-440awhp. Its got smooth lightweight components, top notch engineered awd system to make the most of all the power, and so on. I can see that it woud only lose 40-50hp through its drivetrain but to say its losing 150 is absolutely retarded. I think they did the same with the newer mustang gt when it came out as it was only rated at 350hp and was putting down 320hp to the rear wheels and motor trend went off saying i think its packing more punch than what they said it is.

That is all.
2013-03-05 05:25:25
Originally Posted by WingmanSR20
tl:dr: only way to know is to dyno it yourself. There's no 'magic formula'.

True that, it depends entirely on your'e running gear, which gearbox, auto or manual, what ratios, diff type, and ratios, bearing types, oil thickness etc.

I see what some people are saying with a power X drive train = a %, but an easy way to prove thats not a rule, if you had a parachute behind a car, at 50kmh you may need 200hp to pull it , but as speed increases so does the need for power due to drag,
as the drag becomes greater the percentage becomes higher. and so on.

but with a gearbox, and diff, its a constant drag, infact i would have thought it would be somewhat the opposite as when HP increases so does torque and with the same running gear higher HP would overcome some of the losses of a standard engine.
there is alot of factors in this equasion, when power ins increased so is the need for higher resistant parts which in turn would also create power loss.

I hear a ford 9" diff can rob up to 40 - 50hp, where as say a borg warner diff may only swallow up 20hp, an auto transmitiion has slipping parts, more complex workings as well as a torque converter which also swallows up hp compared to a manual gearbox.

just a few thoughts on this one, as said before, factors vary greatly, and putting a 20% blanket power loss across all vehicle running gears is downright idiotic and not mathematical.
2013-03-05 13:39:59
Way to add nothing but confusion and lies to this 3-year old discussion.
Last edited by BenFenner on 2013-03-05 at 13-41-37.
2013-03-05 18:07:05
LOL^^ I just read this entire post and didn't even notice it was posted 3 years ago till you said this. I just learned some good info I would of never found. :-)
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