Snappy Makes Me Happy

[khp]

This is one of the things that I don't understand about the "V-twin guys" (yes, they're all guys): this thing (I'd call it an obsession) about the so-called "low and mid-range torque" of a V-twin.

Kai;

As one of these "guys" I like the fact that I can short shift entering a corner and let the twin's torque carry me out and thru what would have been an awkward shift moment.

 

The best example I can think of is the Bowl (or T-5) at Loudon where you descend downhill into a 180 degree turn and then climb back up the same slope you came down to enter into this 180 corner. Where it gets interesting is a kink as you approach the last quarter of the climb out which is just before the bike typically requires an upshift. If you had downshifted as you entered the Bowl you end up leaned over, up against the rev limiter when you apex the kink. An instructor told me to forgo the downshift at the base of the hill where you enter the bowl and use the twins torque to climb all the way out past the kink. I didn't think it would work but once I tried it I understood better why low end grunt can pay dividends.

Rain,

 

Why wouldn't you be able to do the same on an inline-4 (IL4) engine bike?

My point was mostly that from my observations, the IL4 engine provides just as much (or more) low end torque as a V2 engine.

 

Kai

[faffi]

Kai, comparing the SV to your YZF has far more to do about tuning than the number of cylinders. If you were both restricted to upshifting at 5000 rpm, the SV would walk all over your R6 because a 70hp 650 will make much more low-end power than a 110hp 600. Now, since the four can rev higher - both due to tuning and due to less stroke - you can gear it lower and as such have more torque at the rear wheel for any given gear and speed.

 

All things else being equal, a twin will always have a narrower powerband than a four. My CB400SF will pull smoothly from 1200 rpm in 6th gear. I can even use full throttle. And it revs to 12500 rpm. Try that with a 12k rpm Ducati! But perhaps a more fair comparison would be a current air cooled Ducati 1100 cc twin to that of an air cooled 1100 four. 30 years ago, the fours made more power over a wider range than the current Ducatis, albeit the latter will have peaks in the midrange surpassing the old Japanese UJMs. Still, fours will deliver useable power at lower rpm than the twin and is also able to rev higher reliably.

 

I dug out this old thing I made back in 2007, comparing a twin and a four of the same capacity. This is a comparison between the Suzuki 1400 and the Suzuki 1400. VS vs GSX. Twin vs Four. The Intruder had enough top gear lunge to stay with the old V-Max between 40 and 80 mph, so no slouch. Yet the four easily beats it from idle and up.

 

VS / GSX

 

No of cylinders: 2 / 4

CC: 1360 / 1402

Bore x stroke: 94 x 98 / 81 x 68

Carburation. 2 x 36mm CV / 4 x 34mm fuel injection

Weight wet: 260 kg / 260 kg

Payload: 200 kg / 200 kg

Max power measured: 66 @ 5000 / 110 @ 7000

Max torque measured: 108 @ 3000 / 128 @ 5000

Torque measured over 100Nm: 2500-4500rpm / 2000-7500rpm

Torgue measure over 110Nm: - / 2500-7000

rpm @ 100 kph: 3200 / 3090

Max theoretical speed at redline: 187 kph / 291 kph

Max theoretical speed at max power: 156 kph / 217 kph

 

PERFORMANCE

Max measured top speed: 167 kph / (230 kph claimed)

0-100kph: 5.2 / 3.0

0-140kph: 11.3 / 5.4

60-140kph in top: 10.1 / 8.9

Avg fuel consumption: 5.8 / 6.6

 

So it's pretty obvious that 4 cylinders makes the better motor. More flexible, greater rev range, more power everywhere.

 

I'd still take the twin, however, because I prefer the way singles and twins feels. But I would never pick fewer cylinders if I wanted optimum performance.

[khp]

Kai, comparing the SV to your YZF has far more to do about tuning than the number of cylinders. If you were both restricted to upshifting at 5000 rpm, the SV would walk all over your R6 because a 70hp 650 will make much more low-end power than a 110hp 600. Now, since the four can rev higher - both due to tuning and due to less stroke - you can gear it lower and as such have more torque at the rear wheel for any given gear and speed.

 

When comparing engine configurations, you quickly end up discussing "what is a 'fair comparison?"

 

Engine redlines are limited by the average speed of the pistons (around 22m/sec 72ft/sec), so comparing say 1500rpm of the XT600 engine with 1500rpm of an IL4 engine is not reasonable. My old faithful XT600Z had a redline of 7,000rpm; my R6 -08 has a redline of 15,500rpm.

 

An friend of a friend did a comparison some years ago where he scaled the RPM ranges of both V2 and IL4's to "100%" and showed that the IL4 had better power - basically everywhere.

 

(snippage)

So it's pretty obvious that 4 cylinders makes the better motor. More flexible, greater rev range, more power everywhere.

 

I'd still take the twin, however, because I prefer the way singles and twins feels. But I would never pick fewer cylinders if I wanted optimum performance.

So we agree -the IL4 is an overall better, more flexible engine. I absolutely agree on a lot of this is down to rider preference.

 

I mean, the sound of the Ducatis' are awesome (expect for the handful of bolts and nuts they throw into the clutch basket).

[faffi]

I never disagreed with you in principle, I just needed to correct you when it came to low end power between the two bikes you mentioned

 

We could just say that for any target in hp per cc, a 4-cylinder will make the target with less rpm and with more power from idle onwards than an engine with less cylinders. No contest. But the twin may still feel stronger.

[YellowDuck]

Well, to be honest, in my comment I wasn't really comparing my bike to an inline 4 of the same (or even similar) displacement (the racing orgs don't either!). And yeah, overall, even a 600-4 is going to be faster around the track than my 1000-cc air-cooled twin. But on corner exits, I have them with the torque - albeit with a 400-cc advantage! I was just pointing out that even though everyone knows that a Japanese 600 is (much) faster, it can be kind of fun to make them work for the passes by gapping them on the first part of the straight.

 

The lack of revs are definitely a disadvantage. There are some short straights where I need to grab a gear and then gear down again for the next corner, where the I-4 banshees just scream up to 14,000 rpm then close the throttle when it is time to slow down. On the other hand, if I forget a downshift I can usually chug through the corner at nearly the same speed, whereas on a 600 I would be just sitting there waiting for the motor to do something.

 

There are no displacement limits at trackdays. Why not ride something big, but simple and fun? I have no coolant to flush, and I can do a valve adjustment in my driveway in about at hour (there's only 4 of them, and no cam removal required. I don't even have to take the tank off). Plus, I bring joy to all of the pit wall spectators with the thundering sound of the thing.

 

Yes, I know it is an oddball choice...but I hope you can understand what I see in it.

 

 

[faffi]

YD, I can very well appreciate the satisfaction from beating faster bikes with your "ancient" ride. I know I giggled when leaving a Blackbird and an FJ1200 behind riding my old KZ400 twin. However, torque at the cank means nothing; only horsepower does, really.

 

Of course, your machine will make more torque than a 600. That comes from capacity. But since a 600 tuned for 120hp can rev way higher, the rider can come out of just about any corner with more power than your bike is capable of. And if it has more horsepower at the crank, it also has more torque at the rear wheel.

 

Your bigger engine may be easier to keep in the powerband and it may also be easier to get a good drive out of the turns, but the real reason why you beat the competition is because you ride better, not due to any torque your engine makes. The torque simply allows you to get the same job done with less rpm, getting the drive demand skill; throttle control, lines, gear choice etc.

[YellowDuck]

Your bigger engine may be easier to keep in the powerband and it may also be easier to get a good drive out of the turns, but the real reason why you beat the competition is because you ride better,

 

Well, I am certainly happy with that explanation!

 

Seriously, I totally understand what you are saying about engine hp, gearing and rear-wheel torque - I know the physics too and so can't argue with what you are saying in theory, but I am curious to know if it is quantitatively correct that a 600, ridden properly, will pretty much always be able to exit a corner with more rear wheel torque than my bike. It is not just about peak hp, but also the breadth of the rpm range over which that peak occurs (since you have to accelerate!). Not saying you are wrong, just that I think I will look at a few dyno graphs and try to figure it out numerically...

 

But I am still good with the "superior rider" explanation...

[YellowDuck]

Your bigger engine may be easier to keep in the powerband and it may also be easier to get a good drive out of the turns, but the real reason why you beat the competition is because you ride better,

 

Well, I am certainly happy with that explanation!

 

Seriously, I totally understand what you are saying about engine hp, gearing and rear-wheel torque - I know the physics too and so can't argue with what you are saying in theory, but I am curious to know if it is quantitatively correct that a 600, ridden properly, will pretty much always be able to exit a corner with more rear wheel torque than my bike. It is not just about peak hp, but also the breadth of the rpm range over which that peak occurs (since you have to accelerate!). Not saying you are wrong, just that I think I will look at a few dyno graphs and try to figure it out numerically...

 

But I am still good with the "superior rider" explanation...

 

 

Okay, looked at the graphs, did the math. You are 100% correct Eirik - an R6 rider who can keep it on the boil should leave me for dead exiting the corners pretty much every time.

[faffi]

Fark me

 

Told you you're a good rider