Inline 4s

Muffles, yes you misunderstood me. I wasnt saying the HP was more important than torque, in fact you could forget about that it was equally important, or as you pointed out revs were eqaully important as one is just a measure of the other two.

Tailing off is not so easy to quantify, its a matter of opinion and depends what the rider means by tailing off. Does the rate of acceleration decrease after 8k, yes it does, but it is still accelerating at a good rate and will continue to do so until it hits the red line. It doesnt suddenly die away to nothing, forcing to change gear like a lot of diesel engine do.

[Sid Squid]

Originally Posted by yorkie_chris

You could apply same arguments against fours and for sixes, and look how well they lasted

Very true, I limited my comments merely to the question asked - this is a big subject, we could go on for a loooong time. General speaking the reason, (as I am undoubtedly sure you well understand), for the lack of modern sixes is simply size, an inline six, a la CBX, Z13 and Sei is a silly configuration for a motorcycle engine, a V6 might be better though*, but law of diminishing returns etc means that fours have the best balance of P/V area and managability of fitting in a sensible shape/size chassis.
V6 Kawasaki 750/1000 would be fun though .

Originally Posted by yorkie_chris

More stuff

Also all true, but I didn't wish to get too technical and - as I am also sure you know well - was speaking in general terms, by which I mean two engines of similar capacity but of each configuration, twin and four, would, again very generally, have the dis/advantages mentioned. You could build a extra long stroke four or a ultra short stroke twin if you wished, but you'd possibly be compromising the better nature of each, and, dependant on the purpose to which the engine would be put, the strengths of various engine configurations have much to recommend them, or not, depending.

*I've been thinking about this and I can't remember a V6 motorcycle, with the exception of a Laverda which may have been a short lived endurance racer or perhaps just a prototype, anyway I have a dim recollection** of err... something. Probably.

** Generally I only have a dim recollection. at best, of yesterday.

[mikerj]

Originally Posted by fizzwheel

Thing is to compare the two.

8K in 6th on the SV, compared with 8K in 6th gear on the GSXR, the GSXR feels hell of a lot more eager at that point than the SV ever did. Just surges forward whereas the SV to me in comparision feels slow.

I think this is more to do with the fact that the GSXR is twice the BHP of the SV. Rather than comparing IL4 with a twin.

It's nothing to do with peak BHP at that point, and everything to do with gearing. The GSX-R has lower overall gearing in 6th than the SV (i.e. lower mph/1000RPM), so a greater torque multiplying effect which (more than) compensates for the lower torque the engine is producing. If you geared the SV the same as the GSX-R then the SV would pull harder - though it would then be revving it's nuts off when you reached a sensible cruising speed.

However, this is getting away from the original statement that the SV's acceleration is noticeably tailing off at 8k, when clearly a healthy one will only be down from peak torque by a gnats tadger and therefore still be pulling hard.

[fizzwheel]

I dont think theres alot in it if I have understood my google results.

GSXR 6th gear ratio = 5.424:1
SV 6th gear ratio = 5.331 :1

IIRC 7000rpm on the SV was near as damn it 100mph, I got a SP30 when I was running my GSXR in and had a 7000rpm limit, speed I got done for was 93.2mph.

[mikerj]

My Google results showed a substantial difference:

2005 GSX-R600 6.404:1

2003 SV650S 5.218:1 (5.337:1 for the naked version)

Perhaps the gearbox or final drive ratios on the GSX-R were changed a lot in different years?

[yorkie_chris]

try gearing commander for numbers like that

[fizzwheel]

Originally Posted by mikerj

Perhaps the gearbox or final drive ratios on the GSX-R were changed a lot in different years?

Possibly, but my ratio's are for the GSXR 750, but yours if for the 600.

I was comparing what the SV felt like to me with how the 750 feels in 6th gear...

My fault for not making it clear.

Originally Posted by mikerj

However, this is getting away from the original statement that the SV's acceleration is noticeably tailing off at 8k, when clearly a healthy one will only be down from peak torque by a gnats tadger and therefore still be pulling hard.

I'm a tad confused - are you saying the graphs I posted are not of healthy engines? I'm not saying there is a sudden drop at 8k, but yes indeed, it is dropping away to eventually finish around 10 lb-ft lower (~45 to ~35). If we're comparing the GSX-R at 8k the torque is flat/on the up at that point (haven't got graph up right now to see) so it's certainly going to feel like it's pulling harder. The thing is it's all relative to the acceleration you experienced up to that point. Up to 8k on the SV, you had better acceleration, so you feel like it tails away. Up to 8k on the GSX-R, you had worse/same acceleration so you feel it's either the same or better (and certainly doesn't tail away).

Originally Posted by muffles

Up to 8k on the SV, you had better acceleration, so you feel like it tails away.

Muffles, I don't think anybody is arguing which bike is faster at 8k.

And whether or not the graphs are of a healthy engine is pretty irrelevant, because they give you facts and figures on engine output, and tell you nothing about the real world connection between the rider, the throttle and the bikes real forward motion. That is influenced by gearing, aerodynamics, the weight of the rider, etc, etc. They can be used to support an argument about how the bike "feels", but they can't be used to define how the bike will feel.

People are debating the statement that the SV "tails away" after 8k. Therefore you need to define what you mean by "tails away"

(A) Doesn't pull any harder after 8k, but it's still accelerating the same.
(B) Doesn't pull quite as hard after 8k as it was before, but it's still accelerating well.
(C) A significant and noticeable drop in how hard the bike is pulling after 8k. Is not accelerating anymore, but maintaining the same speed.
(D) It's deceleration and loosing speed, best to change up gear if you don't want the guy behind up your ar$e
(D) Forget it, you hit a wall, the front forks take a dive, and you have to grab another gear quick.

All of the above scenarios could be true on a small capacity bike or a two stroke, or a diesel car or van.

On my SV it's somewhere between A and B, but I have no overwhelming feeling that I have to change up gear, the bike is still pulling plenty hard enough, from 8k right the way to the red line. I'm 16 stone BTW. I always have to add the caveat in these debates that my SV is geared down.

I have on the very odd occasion bounced my SV off the limiter, when was wringing it's neck and wasn't paying attention to the revs. This happened to me a couple of times after I changed to an aftermarket exhaust, because the exhaust note I had got used to warning me how hard I was revving the bike had changed. If the acceleration tailed away that badly after 8k, you'd never get the bike anywhere near the rev limiter without realising.

Originally Posted by -Ralph-

Muffles, I don't think anybody is arguing which bike is faster at 8k.

And whether or not the graphs are of a healthy engine is pretty irrelevant, because they give you facts and figures on engine output, and tell you nothing about the real world connection between the rider, the throttle and the bikes real forward motion. That is influenced by gearing, aerodynamics, the weight of the rider, etc, etc. They can be used to support an argument about how the bike "feels", but they can't be used to define how the bike will feel.

People are debating the statement that the SV "tails away" after 8k. Therefore you need to define what you mean by "tails away"

(A) Doesn't pull any harder after 8k, but it's still accelerating the same.
(B) Doesn't pull quite as hard after 8k as it was before, but it's still accelerating well.
(C) A significant and noticeable drop in how hard the bike is pulling after 8k. Is not accelerating anymore, but maintaining the same speed.
(D) It's deceleration and loosing speed, best to change up gear if you don't want the guy behind up your ar$e
(D) Forget it, you hit a wall, the front forks take a dive, and you have to grab another gear quick.

All of the above scenarios could be true on a small capacity bike or a two stroke, or a diesel car or van.

On my SV it's somewhere between A and B, but I have no overwhelming feeling that I have to change up gear, the bike is still pulling plenty hard enough, from 8k right the way to the red line. I'm 16 stone BTW. I always have to add the caveat in these debates that my SV is geared down.

I have on the very odd occasion bounced my SV off the limiter, when was wringing it's neck and wasn't paying attention to the revs. This happened to me a couple of times after I changed to an aftermarket exhaust, because the exhaust note I had got used to warning me how hard I was revving the bike had changed. If the acceleration tailed away that badly after 8k, you'd never get the bike anywhere near the rev limiter without realising.

I agree, between A & B. You're right I probably should have clarified better what I meant, I think I did that in my previous post but it wasn't as clear as you've stated it.

My original point was that yes the IL4 would be faster at 8k - this point only came about because I was countering the "twins are better because of the low down shove" point (as in - why is low down necessarily good? Why is high up not good? It's implicit that it's not good in that point). Point to point to point