30-70 Times...

It's very relevant to how well an engine can shift the weight around it.

Or perhaps you'd like to try fitting the engine out of a Yamaha R1 into a Saab 9-3 2.0t given, unless I'm mistaken, both have around

If you could then let us all know afterwards how the Saab then performs, I'd be grateful.

-- JackH

-- JackH

It's very relevant to how well an engine can shift the weight around it.

Or perhaps you'd like to try fitting the engine out of a Yamaha R1 into a Saab 9-3 2.0t given, unless I'm mistaken, both have around

If you could then let us all know afterwards how the Saab then performs, I'd be grateful.

-- JackH

-- JackH

It would perform exactly the same.

You just have half the torqu at double the revs which then needs half the gearing so torque at wheels at any given roadspeed is the same.

Well go on then... go and perform the conversion to a Saab and see how well it drives afterwards. ;-)

Torque is relevant as well as outright BHP - the more torque you have over more of the rev range, the quicker you will accelerate, regardless of peak BHP.

-- JackH

-- JackH

As far as outright performance is concerned they would both perform the same.

the more torque you have

Wrong since the bike engine has more gears to allow it to stay in the highest bhp part of the power curve.

If you mean the saab has more torque at lower rpm meaning it will accelerate harder without having to change down a gear then that may well be true. But even then I would need to see power curves from both to be sure.

Remember that since the bike revs twice as hard the gearing is twice as low at any given road speed. So torque at the wheels is dfoubled.

You are confusing flexibility, or low rev power, or nice cuddly drivability with outright power. Power is directly comparable. Torque alone is meaningless as a comparison unless you also know the rpm (and therefore gearing required at any given roadspeed). The SHAPE of the power curve (or torque curve) is where you think the saab is better. But also remember that as well as having more gears that are closer together (meaning its easier to match the best part of the curve to the roadspeed) its also massively lighter. So it will accelerate better even with the same power/torque...

Like I say, go build one and then share the results... be sure to stock up on clutch plates for the R1 engine first though.

I'm not, you know.

You can have as much peak BHP or torque as you like at one given point, but the more torque you have available for more of the rev range, the more grunt / acceleration you have to play with over those particular revs... and you can then, as you've sort of touched on elsewhere in this message, gear something to get the best from it.

The SHAPE of the power curve is more suited to the application to which the car engine has been applied.

Agreed... so I wonder why it is that all car manufacturers have it so wrong in what they deem as suitable for fitment to their vehicles, engine wise. ;-)

Perhaps they should be fitting 15 speed gearboxes to bike engines to propel cars in future?

...if you can get it to pull away without burning the clutch out.

-- JackH

Simple physics and or years of experience tells me without having to build one. It may not help you but thats your problem!

In which case you are just plain wrong.

Wrong. POWER accelerates your car. It can make that power with lots of torque at low revs or very little torque at high revs. EG a typical car may have best torque at 2k revs. You still rev it harder than that to get best acceleration. Because its better to have less torque later in the rev range but more often! Since this gives greater total power.

POWER is directly comparable. In the same way as tons, or miles, or degrees C. Torque however tells you nothing on its own. A motor that revs to 10x as high with 1/10th of the torque will have EXACTLY the same effect on accelleration at any given roadspeed as the original with 10x the torque. Very SIMPLE physics dictates that. Unless you know the rate ate which your big torque figure is produced it means absolutely nothing. And once you do then you can simply calculate the POWER from it! Which is directly comparable.

Without seeing the graphs then I or you wouldnt know. And if it is which is very likely, then it still does not mean that the car would faster. It means as I said before that it may be more drivable or have better low rpm acceleration. It would still not out accelerate the bike engine when reved out properly through the (more) gears. The car would not accelerate faster. It would however be easier to drive fast. Which is the part where you were apparently confused and still are!

They dont. They build cars - even "fast" normal cars as a) grocery getters that your mum can drive b) easy and nice quiet low reving engines that dont scare the drivers c) to a price. Its easy to get a big cheap nasty engine to give power less so a bike type engine with 170bhp per litre without a turbo! d) noise emmisuions e) save the planet emmissions

A bike engine has much greater cost than a car engine due to its high performance light weight and development costs. A bigger car engine that needs a turbo to compete with it is cheap. Just a big block of iron/alloy with some holes bored in it. It doesent need to survive reliably at 13000 rpm so nasty cheap cast pistons, small heavy valves etc. Different markets.

But that wasnt your original point. You seemed to think that less torque at higher rpm was not going to accelerate your saab as fast. Well not only will it do it as fast it will be faster due to much less weight...

Emmissions, fuel economy, ease of use, cost, noise, etc as above. I never claimed it was a good idea just that it would propel your saab just as well. That was your original point or am I wrong?

Since its gearing will be half what the car engine needed then it would pull away just fine. It was designed to handle 170bhp regardless. And with lots of abuse. You only need about 15 to pull away.

That will be at the back wheels, not the crank. That's where it's important.

Bikes have reduction gearing and in the case of the R1 rev to a gazillion revs. That all helps to make the rear wheels numbers what they need to be.

My old ZX10 engine doesn't rev as high, but I don't doubt for a second that acceleration won't be a problem.

Well the smell of burning clutch when you tried to pull away having built one might finally get through to what few senses you have left.

(I presume the numerous bangs on the head you've had over the years haven't managed to knock your sense of smell out completely?).

Right in this particular instance, I'm afraid.

Yes, and the reason well sorted TDIs go so well is because although they have a relatively low rev range, they have a very broad spread of torque available over what revs they have got...

I could still have 173bhp in mine... but less torque available lower down the rev range meaning that unless the gearing was revised to suit, I'd almost certainly not get as much acceleration out of it - the power generated suits the gearing that comes with the car as standard.

To summarise, peak figures mean piss all to a certain extent - it's the available spread of BHP vs Torque that counts in the real world, given a manufacturer will have geared something to get the best out of the engine given the vehicle to which it's been applied.

Bolt an R1 engine as is (in terms of gearing etc) and as in something designed to shift 400kg of mass in total, max, into something that weighs upwards of 1.5 tons (no idea what a Saab with one driver weighs, but it has to be at least that if not more, depending on which era it was build), and it will struggle to get the car moving without excessive clutch slip and / or stalling.

Maybe not, but going back to the original argument, BHP on its own is of little consequence without knowing how much torque you have to play with and how heavy the article to be moved is, and over how much of the rev range the bulk of the torque is available.

That was the point I was making... clear enough for you now?

Rubbish. It's geared (as standard), to move say 275kg including a rider, off the mark... not 1.5 tons or thereabouts.

Not without much slipping of the clutch and / or stalling.

And with lots of abuse. You only need about 15 to pull away.

Not in something that weighs 1.5 tons... not unless you're going to fit a gearbox with a ridiculous amount of gears and a severely uprated clutch, together with a decent flywheel.

-- JackH

-- JackH

I was quoting for the original R1 which was 150bhp at the crank. The new ones are reportedly that at the back wheel, 180ish at the crank. :-)

Aye. Ideal for application in a s**te old family car. ;-)

Aye... because it's almost certainly got a broader spread of peak torque lower down.

The engine in that is almost certainly more suited to sticking in a lightweight kit car than an R1 one, I reckon... and now we all know why the Hayabusa / Blackbird lumps are popular for that kind of thing, don't we children? :-)

-- JackH

Well the smell of burning clutch when you tried to pull away having built one might finally get through to what few senses you have left.

(I presume the numerous bangs on the head you've had over the years haven't managed to knock your sense of smell out completely?).

No its because I understand physics. Its not an issue, in any case forms no part of the original argument. That was about torque.

Plus its poiuntless with you as you dont seem to be able to grasp basics and you change the rules and start going on about clutches and stuff.

I cant be bothered since you just cant understand well.

It also means that at the same ROADSPEED the torque is where it needs to be too.

It wont. Power is power.

My olde EFE suzuki made peak torque at 3800 rpm. But if I wanted to accelerate hard on the strip I changed at 9750 rpm. Because although there is LESS torque here its happening much faster and in the same LOW gear ratio compared to say a car.

Yep it is. With A further reduction in final drive ratio needed so that top rpm in top gear is about what you would expect at the cars expected top speed. Further increasing torque at the wheels at any given road speed.

It will need to because it doesent re as high needing taller gearing than an R1

Maybe you "rekon" but you "rekon" wrong. By the time you take into effect the extra reduction gearing the revier and more powerful motor is a better bet. Physics rather than your "reconing" says so. Power is DIRECTLY comparable and the R1 has a lot more.

and now we all know

Yes they are bigger. They have more midrange. They are more tractable at low revs, nicer to drive. They dont have much more power (if any) and they wont therefore go much faster. But as I said many times already a motor with more low down power is nicer and more civilised to drive. But thats not the same thing as better accelerating.

Which still has nothing to do with your original argument about torque and saying that the R1 motor would be slower.. You moved the goalposts because you are wrong.

It's very relevant to how well an engine can shift the weight around it.

Or perhaps you'd like to try fitting the engine out of a Yamaha R1 into a Saab 9-3 2.0t given, unless I'm mistaken, both have around

If they were geared right, and kept on the boil, they'd be the same.

Vauxhall Astra GSi vs Civic Type R - Astra has more low down torque, both have 197bhp and similar weight, but flat out, they have the same performance. Low down torque only matters for in gear tests, as long as the Honda is kept on the boil, it'll keep up. Launching is done at high revs, then just keep them there.

The R1 engine vs 1.8T was extreme, but if you had a clutch and gearbox that could take the abuse and if you managed to keep the revs up high, it would be the same flat out performance. It'd be an absolute pig to drive mind you except from in straight line drags heh.

Yes, very clear. Also wrong. What matters is the distribution of POWER with respect to rpm. The absolute value of torque is meaningless, because it is not a conserved quantity; it is mutable by gearing.

As an aside, the R1 produces peak power at 11000rpm, producing about

Given a reduction in gearing of about 3:1 compared to a normal car gearbox, but having 5 gears with the normal ~1.4:1 ratios between them, it would pull away easily and without significant clutch slipping - it would feel the same as a car pulling away at 1000rpm with 162lbft of torque to play with.

The original point I was making, and maybe I should have made it a bit clearer, is you can have two engines, both knocking out a peak figure of say 150bhp (hence why I picked the Saab and the R1), but without knowing how that peak is reached, I.E: by dynoing them and observing how much torque they've got and where in the rev range, you've no real idea about the spread of power the engine has.

Two engines that ultimately peak at 150bhp will not necessarily build to that figure (i.e: they won't have the same spread of torque), in the same way, and therefore will not necessarily provide the same acceleration as each other in the same application, no matter how well you match the gearing.

-- JackH

This doesn't need to be made any clearer, because it is trivially obvious.

What you actually said was that a smaller, higher revving engine wouldn't be able to accelerate a large, heavy car as well as a larger, lower revving engine. This is wrong - the suitability of an engine to do this depends on the *shape* of it's POWER curve, not the size of the engine or the absolute value of the torque it produces at the crank.

Trust me he wont get it.

Correct. But he STILL wont get it. Because he isnt capable.

So you'd think... except quite early on in this thread, I said this:

"Torque is relevant as well as outright BHP - the more torque you have over more of the rev range, the quicker you will accelerate, regardless of peak BHP"

Which bit of 'the more torque you have over more of the rev range' is it that you and the cretinous crip (1) been having trouble with exactly?

Well duh... see above, Lawrence Logic.

HTH

(1) He who seems to think almost every thread is a pissing contest that must be won at all costs, complete with moveable jumpers for goalposts, apparently.

-- JackH