Anyone got any idea how much power loss there is through a (standard: 4-synchro, 3.44 open diff) mini transmission? I've heard figures anywhere between 30 and 50%. Going to get my car chassis dynoed at some point so curious what the hypothetical flywheel figure would be.

Thanks.

The 30-50% is often used as each gearbox varies a little bit just like each dyno varies . Probably just average it and say 40% loss and work the figure out from that , the estimated flywheel figure isn't going to be all that accurate anyway so a few % either way won't change much unless you have a super high performance engine .

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Thanks. Any thoughts on the theoretical figures some dynos give by allowing the rollers to slow down against the engine?

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Caring about your job is for people without lives.

Too many variables. Gearbox driveshaft output makes a difference, pot joints being better than hardies or ruber unis. Wheel sizes and tyre sizes will also play a role in power transfer. I heard diff types also having a role (quaife lsd versus std) In general people are seeing about 30% loss at the minimum

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Lillee - 1969 Morris Mini K

What type of dyno?

The reason why the Dyno Dynamics is so popular is simply because the correction factors & standardisation (i.e. all tests done in fourth gear, tyres all pumped to 32? PSI, etc) of the test means you can compare one dyno run to another on a different machine / day.

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Too many cars, and too little time.

Not sure yet! Got a specialist lined up, but don't know what he's got. The car is still up on blocks with a few crucial bits missing, anyway!

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Caring about your job is for people without lives.

That's what they lead you to believe. I bet a case of beer that you'll get 2 different figures for your car on 2 different days because the operator put his foot down differently on one day versus the other. I'm not joking...

Engine dyno is the only true repeatable measurement of hp

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Lillee - 1969 Morris Mini K

True enough, but short of pulling the engine out it's the best way of getting a power figure. Power ATW will be affected by other uncontollable factors too, e.g. wider/stickier tyres will rob measured power.

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Too many cars, and too little time.

It's a good tuning tool, that's about it. Good measurement of comparison HP if run on the same day by same operator. Other than that it's academic.

I refer to HP figures published from UK Mini managine's dyno shoot outs. I am sorry but no 1310 with twin 1 1/4 SUs with only a cam and exhaust mods can do 90hp atw. Sorry but no...

If you walk away with X hp on your rolling road dyno sheet, and another guy has X hp on his dyno sheet from 1 year ago, it means absolutely nothing. Yes if one says 100hp and the other says 28hp arguably the 100hp one is propably a faster car but by how much can be measured in only in aspragus

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Lillee - 1969 Morris Mini K

The more power you put through a gearbox the more power you lose as the internal friction will increase with load. It is not just a matter of turning a gearbox and measuring the force taken to turn it.

A wheel dyno is a tuning tool and not a measuring stick.

wide sticky tyres vs skinny crossplys
low pressure tyres vs high pressure
wheel alignment with excessive toe out/in vs set straight ahead-ish
worn gearbox/drop gear assys vs new-ish bearings/gears/shafts & well thrusted box
& how much or how tight/hard they pull/strap the car down on the rollers

all these things play """Significant""" roles in rolling road dynos

but my "Guestimation on the average mini would be --->
"""around 25%-ish-approx-maybe-ish"""

Big Grunt minis push gears & shafts harder into themselves & thrusts etc so they tend to loose a bit more, but then most sensible "Big-Grunt" car owners would fit C/R S/C gear kits to save loosing that little bit

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Thanks to all for the info RE the chassis dyno issue! FYI, the dyno is to be used for tuning purposes only (not barstool drag-racing) but I was curious if there was a uniform way to translate that into flywheel power...obviously not!

Not too concerned. After all, I tend to drive the whole car...not just the engine

BTW: Glad someone else is suspicious about those UK dyno-day figures. I'd almost believe them as flywheel figures, but ATW...no way!

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Caring about your job is for people without lives.

It`s all just a guestimation, no matter what dyno & no matter where it is

he """REAL""" test is a "Car-To-Car" race

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.