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

1 hp = 33,000 ft/lb/minute. Mr Watts calculated figure for how much work the average horse was capeble of in 8 hours. Its not exact its just a number that is generaly accepted as the norm. Horsepower is a nonsensicle measurement. However once it is accepted it can become a comparable factual figure.

One revolution of one pound at a one foot radius is 6.283 ft/lb (Pi x Diameter)

So 33,000 ft/lb/min divided by 6.283 ft/lb/rev, equals 5252 revolutions per minutes. So it takes 5252 rpm to achive 1 horsepower with a torque of 6.283ft/lb. simple maths.

Edited by Sprocket on 19th Aug, 2006.

Just think, your engine only converts about 30% of the heat in the fuel to power at the flywheel.

So there must be about 75kW of heat coming out of your exhaust and off the radiator!!!!

Hence Global Warming.

Most of the energy lost between the flywheel and the wheels is as heat. Thats why the gerabox has lots of fins on it.

Edited by Paul S on 19th Aug, 2006.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

thats what i am getting at, but 30kw?

No amount of fins on the gearbox is going to reject that amount of heat!

Edited by Sprocket on 19th Aug, 2006.

I knew I shouldn't have mention Global Warming. I just came back to delete it but TOO LATE. Bugger.

For what it's worth, I'm currently working in flood defence and use rainfall data to build hydrodynamic models of river systems. The data we used to use was based on the rainfall between 1940 and 1970. We are now using real rainfall data for 1940 to 2000 and it has gone up by 20%. that means in the last 30 years rainfall is 40% higher than in the previous 30 years.

Get your head out of the sand, it's happening.

Scares the shit out of me. I will either die of poverty or heat exhaustion.

Edited by Paul S on 19th Aug, 2006.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Im not getting drawn in to all this as its all bollox.

Next thing you know the 'ex purts' will be telling us that the earths crust solidified all those billions of years ago, was our fault, or the ice ages happened because we did something. What about the earth getting 10mm farther away from the sun every year. No one ever mentions the mass increase of population of the human race. Each human produces CO2 ALL THE TIME, that has to increase the CO2 emissions levels. Or, the dissolved CO2 in the depths of the oceans that gets released in one huge eruption out in the middle of no where, where they go undetected ( except that small vilige in the southern Americas, cant remember where exactly)

A human cyclist has been calculated to produce 32lbs of CO2 over 1000miles, an eficient car with 50mpg produces 500lbs over the same distance. However what the did not take into consideration is that cars turn off humans dont, granted at a much reduce emissions rate but the car produces nothing when not being used.

Not only this but humans also produce hydrocarbons too, ALL THE TIME

What happened to the hole in the ozone layer, you dont hear much about that these days. The biggest hole is yet to come. This is due to the life cycle of the CFCs. We are only starting to see the effects of these CFC gasses on the ozone layer fron 50 years ago when most of these gasses were introduced, there uses and volumes grew and the peak was in the eighty's when it was seen as a problem and they were than phazed out early ninety's.

Its still a problem but we dont hear dick about it.

I'll stop here, i said i wasnt getting involved.

lol

incidently , me and the wife watched 'The Day After Tomorrow', earlier.

Its all bollox, lol.

Edited by Sprocket on 19th Aug, 2006.

Let's get back on topic

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

right

oops!

Sound, heat, vibration...

I dont, half pisses as its my bday

Alex

AlexF

oh i give up

The drag of the transmission is power produced by the engine converted to heat by the inefficiency of the gearbox.

Sod this, off to bed early. MITP tomorrow.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Did any body study Quantum physics?lol

They should be able to help!

http://www.ftexploring.com/energy/first-law_p2.html

http://www.dynamometer.fsnet.co.uk/power-l...lywheel-BHP.htm

I'll ask a colleague on Monday about this guys. It's something I've not paid a huge amount of attention to previously, and now I'm spending time thinking about it, it's making less and less sence - but I know that there is NO WAY a transmission alone can take 30-hp just to turn it...

not even when its submerged in oil?

And theres the drop gears to draw off their share!

Alex

AlexF

First law of thermodynamics says that what goes in must come out.

So forgeting the fact that an internal combustion engne is less than %40 efficient, it produces power at the shaft. Calling this %100, as it passes throught the transmision ( that includes the transfer gears, cv joints and tyres) to the driven wheel where there is a loss. Now on my transmission with a 3.76:1 FD, new gearbox bearings through out, regreased CVs and wheel bearings, 175 50 13 tryes at 29psi, there was an indicated loss of 24bhp at the roller.

Now as stated this is 'absorbed' as heat, sound, and vibration. IMO vibration is unwanted movement withing the gearbox, this I am assuming gets absorbed, as heat, if it didnt it would still be vibrating. We have also realised that sound is only a small factor, which leaves the rest of the 'absorbed' energy as heat, this heat must disipate throught the gearbox oil, the cv joints and the tyres. Tyre temperature increases when run on the rollers a little more than it would on the road due to there being two contact patches, but not enogh that if you were to touch them they would burn your hand, same goes for the CVs. the majority of heat should be going into the oil.

On an oil cooler free engine, the only cooling effect of the oil is as it passes through the engine and the sump fins.

what needs to be calculated is the power absorbed by these components, and everything should add up to 24hp.

To be honest, it doesnt sound right that one third of produced power is wasted through absorption. pretty god dam ineffiecient.

Now, the more powerfull the engine, these losses should still work out similar maybe a litles more through a helical gearbox due to side loadson the thrusts. It should not be much more.

It just seems that these fly wheel figures that RR's give is still way off the mark as to what is actualy being produced. Yes they may be repeatable and used for comparisons but the actual power figures at the crank can only be measured on an engine dyno, compare this with the chassis dyno figures and this should give you the 'actual' drag, but then there is the matter of calibration of the different dynos to take into acount.

I will, when i get a chance, ask around at one of our jobs, Shell research at Stanlow, what the score is. one of the buildings we provide chilling for the test cells. This is a building with 16 fully equiped engine dynamometers running tests 24-7 on manufacturers engines. The also test the cv joints in a similar controlled environment. There is a road test department with chassis dynos, but i havent seen any of that, yet.

I'll see if i cant find anything out, dont know when i'll be back there.

I also found this, but its sunday and my head is fried truing to even understand the formula thats in there, never seen anything like it. http://www.hud.ac.uk/sas/trans/btac2002.pdf

Sprocket,

Thats an excellent interpretation of what happens.

In my experience, when I used to design steam turbo alternators for places like Stanlow, we always used to allow 98% efficiency for helical parallel shaft reduction gears. Thats 2% of the power transmitted lost as heat etc.

If you add up all the gear trains in a mini engine & gearbox, there are 5 in gears 1 to 3. Theres 10%!!! Less in top because the mainshaft drives straight through.

Also add up the windage losses for all the free gears and the diff spinning in oil, you start to understand why it could be quite high hp loss.

I agree with you that the only true way of reading flywheel horsepower is by an engine dyno.

The problem is that the dyno people know that customers will come back if you can quote a higher flywheel horspower than the next guy. Hence, as usual, commercialism clowds the reality.

Another thing to think about:

Your driving along a flat road at a steady 90mph. The engine is delivering 48hp at the wheels.

The heat in the fuel used is probably in the region of the equivalent of 150hp, 110kW, due to the inefficiency of the engine.

Where has the 48hp gone? The car has not gained any energy. It would gain potential energy going up a hill and it would gain kinetic energy if it were accelerating, but you're going along steady speed on a flat road.

That 48hp has been absorbed by the air due to the turbulence caused by the car.

So thats 110kW of energy just to move a mini along at 90mph and it all ends up in the atmosphere.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Lol and there we go on the Global warming

It's not the heat that causes Global Warming.

It's those dirty words again. Peter will be off on one soon

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i lost 5bhp's at the wheels when i went on the SAME rollers, 3 weeks apart, with the only difference being colder weather and new tires (same brand) on the front second time round. Pressures were set by me using the same attachment to my compressor. I still have graphs to prove

I've seen the future and tbh its Pie

there are too many variables involved to get a reliable accurate comparison on a set of rollers..

especially with gaps in time between tests, even a couple of hours could give a different result.

Edited by neil_g on 21st Aug, 2006.

Horsepower figures are all bollocks anyway, who cares as long as the engine is set up correctly.
My N/A shows 150 at Baldwins probably 135 at Southern Carbs but I dont care its set up and goes fucking fast.
Paul

I seriously doubt it!

Here for the craic..

Supercharged Arden powered