RR comparison N/A v S/C
Turbo Mini Forums

ha ha rebuild your gearbox, 40 Bananas is silly money

Edited by Sprocket on 23rd Aug, 2006.

Thats on the list..

Here for the craic..

Supercharged Arden powered

OK people, i have been to Shell research today and managed to speek to a guy that operates the chassis dyno for the emissions and environmental department.

Now I found out some very interesting stuff, that some of us may not be aware of. Take the information here within and use it at your own risk, i disclaim any responsability.

If the dyno is a single drum roller then the tyre pressures need not be altered, as this is as close a comparison to road conditions with only one contact patch.

If the dyno is a twin roller set up, then tyre pressures need to be increased 50% (this is the bit you use at your own risk, dependant on tyre choice) This should counter act the pinching effect of the twin roller set up as well as there being two contact patches rather than one.

Modern transmissions generaly have an aproximate 8KW power absorption, Thats 10hp. Taking into consideration that the tansverse A series box is not the best of design and one that is now 45 years old, transmission losses of, for example, 18hp are not un feaseble. Visard touches on this in TBASE and recons on 12hp for a well built gearbox.

So, for my own mind, i'd be happy with a transmission loss between 12 and 24hp. As for losses greater than this with a known good gearbox, there is a problem else where, such as binding brakes, megga soft tyres, or the like.

These losses should not increase much as once they add up thats it. Losses may well increase slightly in high power engines using helical gears due to the side loads generated withing the gear train, but this should only be another 2 or 3 hp.

Other things to remember is whether the RR operator has warmed up the rollers and done a run down of the rollers on its own to calculate any loss withing the 600 odd Kg of mass they have and entered that into the final calc.

Some may think its not worth bothering with, but if you want consistant and as accurate as poss figures that are some what repeatable to a degree then these little things should be taken into acount, where they can. LOL, i can envisage the face of the operator at Minisport when being asked to warm up and do a rundown on the rollers before a power run.

Find a slot on the rollers straight after some one had run before you, that way you know the system is somewhat warmed up.

Edited by Sprocket on 5th Sep, 2006.

heres some more info ,
i ran a sun ram 12 rolling rd test bed for a few years ,and this is my data as i remember it ..
the coast down method of measuring the losses SEEMED to give a good representation of what one would expect ,bear in mind this was a fully calibrated and set up rr . the lowest measured losses were on a 1969 cooper formula one car with a 3.1 alfa v8 ,known as the unfinished project ,that came from south africa , with wide high pressure tyres ,straight cut box ,it had 11 bhp. highest losses were from a astra at 55 bhp ,that had a caliper siezed on .. last year i calibrated a local 4 wheel drive sun ram 12 ,for a client ,and did an experiment to see if the 2 sets of rollers had the same losses ,and to see if they read 0 with no load ,....to do this i put my turbo 500 bike on the rollers ,sped up to about 70 mph ,and rode straight off the rollers ....
the result was one set read slightly higher than the other but niether read 0! i think i got a reading at 70 of 6 bhp ... o i put this down to bearing drag,windage .
incidentaly
at bout 11 at night i decided to see just how fast i could go and still get off the rollers on the bike ,

i got it up to 125 mph before launch ,...
that was quite a focussing moment ...


the ex sun rr engineer told me nobody has done this exp before ,and hed been wanting someone to do it for 30 years , he then made some derogatory comment on my sanity which dont need to be repeated .

Edited by robert on 5th Sep, 2006.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Top stuff, I recon this info should go into the FAQ before it gets lost

Anyone????

LMFAO

Not bringing this back up but read this on another forum

'keeping one mini on the road for 50 years would probably contribute less to global warming than the environmental damage caused by the manufacture of just one so called "green" new car...'

LOL, wonder how true this is

Edited by Paul S on 21st Sep, 2006.

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Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

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