twin vs inline?

[Kham]

so the twin has broader pwr band and inline has what kind? is it a fair analogy of inline to turbo car engine as twin is to non-turbo?

because i think a turbo engine output is a steep curve like half parabola curve and non-turbo engine is more linear?

[bigred875]

Kinda...I would say more like a twin is like a big bore muscle car...good on low end power and torque while an inline 4 is like a honda s2000 or something....not a whole not on the bottom end and torque but once it revs up into the power band it takes off...

[hohum]

Best way to put it is that twins have more torque in the low RPM's and they have lower top end RPM ranges and lose power in the upper RPM's, and spool up slowly.

Inlines have less torque down low, make all their power at the top end of the RPM scale, and spool up and down quickly.

The best way to describe it might be, an inline 4 revs and performs like a turbo car in that it makes all of its power at high revs. A twin performs like a truck, makes all its power at low RPM's.

Cheers,
Chris

[Kham]

good! i like turbo.

[hohum]

Heh, can't diss the low end torque, it makes for great fun screwing out of the end of turns, its really great fun, but it is different...

Last (running) bike for me was an SV650S, and it was a great little fun bike... unfortunately for me, I bought it before that model had nice things like EFI, fully adjustable suspension, etc...

Cheers,
Chris

[Stoneman]

The analogies are for the most part correct. But there ARE high revving V-Twins that still make decent power aobve 10K. That's about where my TL-R REALLY snaps to life. I'd reckon bikes like the Mille and the RC-51 would be similar...

But those are more the exception than the rule...

[hohum]

Actually, according to my buddy Jon (who still has his Mille for a month or so anyhow), the Mille starts to peter out in the high RPM range. The Tiller definitely is still hot at 10K, but its that 8K - 10K rush I loved on that bike... But one ride does not a perfect impression make!

Still, for the general rule, twins and inlines are very different beasts in pretty much every factor in power delivery.. twins kick you in the pants way lower in the RPM range than where inlines do, and inlines soar all the way to the rev limiter.

[bigred875]

Originally posted by hohum
... But one ride does not a perfect impression make!

Thanks Yoda

[hohum]

baha, thats funny, because thats exactly the smiley icon i wished there was, the yoda smiley

[stoinkythepig]

Big twins are (were?) only popular because AMA and World Superbike rules gave a 250cc advantage to twins in the past. Bike companies needed to sell them to compete in the class so they marketed them well and the bikes sold. IL4s make much more power (all things being equal) for the same displacement and weigh less. Big fours are in no way lacking in the torque department. They pull like crazy all over the rev band, they just pull harder up top than a twin, not less down low (unless you count <3500 RPM).

[hohum]

Originally posted by stoinkythepig
Big twins are (were?) only popular because AMA and World Superbike rules gave a 250cc advantage to twins in the past. Bike companies needed to sell them to compete in the class so they marketed them well and the bikes sold. IL4s make much more power (all things being equal) for the same displacement and weigh less. Big fours are in no way lacking in the torque department. They pull like crazy all over the rev band, they just pull harder up top than a twin, not less down low (unless you count <3500 RPM).

Yes, of course, but in the "butt dyno" sense, and when you look at dyno curves of torque on twins, what you tend to see is a line the seems to have a big exponential burst within a given RPM range and then level off, where as on the I4 you tend to see just an upward trending line, which in my impression is what always gave twins that kick in the pants feeling only to peter out, where as I4's just keep pulling and pulling, but without any dramatic peaks within a given RPM range..

[stoinkythepig]

Originally posted by hohum
Yes, of course, but in the "butt dyno" sense, and when you look at dyno curves of torque on twins, what you tend to see is a line the seems to have a big exponential burst within a given RPM range and then level off, where as on the I4 you tend to see just an upward trending line, which in my impression is what always gave twins that kick in the pants feeling only to peter out, where as I4's just keep pulling and pulling, but without any dramatic peaks within a given RPM range..

We are in agreement. High performance IL4s use gearing to take advantage of the much higher RPMs they can achieve with the same displacement, due to the shorter stroke (and therefore lower piston speed at any given RPM). In a roll on test, a GSXR1000 is gonna spank a TL1000, every time. It feels faster in every gear because it is. Big twins feel quick down low only because they typically peter out on top, if you have nothing else to compare it to, the low end feels impressive, until you take that GSXR for a spin...

There are some very short stroke twins out there that pull very hard on top, but they need titanium parts and such (749R, for instance) and cost an absurd amount of money ($22,000 for a bike that performs like last year's 600s...)

[Tarmac]

I know just enough about the difference to get me in trouble. So here it goes....

With a Twin, you have the space between your legs for a pretty decent sized piston, therefore big piston = more fuel & air in each chamber for combustion, hence: alotta bang per firing cycle and alotta more torque per cylinder. When most folks think of twins they think of big loud cruiser engines (harley, etc...) with big displacement pistons and alotta torque down low. I believe that, among other limitations of components/engineering/etc, since jamming all that fuel & air into large spaces takes more time than a smaller piston chamber, as the RPMS go up, they lose their efficiency quicker than those with smaller pistons.

Since an inline has to contain itself between your legs without getting too wide, it has a limitation of piston and chamber size. Even though it's four small against two big, the big generally wins in torque for lower RPMS....Generally. But, that small chamber size takes longer(ie: higher RPM's) to become less efficient then the big one's.

However, once you get into high performance engines that have significant engineering and materials, it seems things start to become more even in terms of torque and hp. Of course there are characteristics that follow each party, but I believe it get's a bit more cloudy. In MotoGP, where manufacturers have luxury of going either way, you still see a number of V's and a number of inlines...but remember a factory will generally lean towards what they're good at building (can u imagine Ducati trying to build an inline?).

Anyway, I'm bound to have let my imagination get the best of me above, but to answer your question in simple terms: yes, you generally get a steeper torque curve that lasts a bit longer when comparing well known street inline-4's and twins. Twins produce flat torque curves that drop before inlines. Inlines start lower and last a bit longer...but there are plenty of exceptions...

[Kham]

thanks everyone. crystal clear now. i'v have to test ride the twin sometime.

[SEVENSGT]

here goes, I know I'm gonna get shit for this but fuck it




the 2001 SV650s and the 2001 GSXR600, I don't have the articles anymore but I do remember how close they were in numbers, such as torque were the SVS had more then the gixxer, but the gixxer had almost(ALMOST) twice the HP. 0-60 test the SVS was only 3/10 of a second slower, but top gear roll ons the SVS was 2/10 quicker.... Now keep in mind this is how I remember it and I looked at these numbers eveyday for 1 year while riding my SVS... I can't compare big twins to litre bikes, but there must be something to it, right???

[Ducrappy]

Originally posted by Kham
thanks everyone. crystal clear now. i'v have to test ride the twin sometime.

You really should. They are a blast. Its much more fun with all of that torque riding through twisties on a twin than a bunch of horsepower for flying down the highway with an inline.

[busa413]

It's also going to depend on how the engine is set up, ie bore stroke etc. I'm going to compare the Hayabusa to the litre bike because it is the only thing I really am up to date power wise. The litre bikes have close the the same HP as the Busa. They also weigh between 80 and 100 pounds less. Now stock vs stock and mod vs mod the Busa is going to to a 1/4 mile quicker (with the same rider) than the litre bikes. How does it do this? It has 20 to 25 more ft/lbs of torque. It is also easier to launch, and up top it has better aeros. The Busa engine is also not designed as radical(not sure if that is a good word to use) as the new litre bikes, and this is why they make good HP numbers. Hell the manual even recommends to put regular gas in the Busa.

The Busa makes about 100 ft/llbs or torque, and it makes it pretty low in the power band.

To sum up what I am saying and I am not sure if I have strayed off topic here, the I4 can be made to have very good torque early. I am attaching a Dyno graph of a slightly modded(cammed and exhaust) Busa. The second one will be a low powered Turbo Busa(I mean low power by still very streetable). One more thing, because of how the Busa engine is made it reacts very well to mods, not to mention the lower end of the engine can take over 300HP without have to be changed from stock.

[brewmaster]

From a seat of the pants feel, the twins flat torque curve allows for a much different riding style. Twins (generally) allow you more room to error on gear selection into and out of turns. On the street this can make a big difference (on the track too if you are a novice, like me). A I4 with an experienced rider can take advantage of the HP it has. For me the twin fits my riding style very well. For many riders the lack of top end power is more of a disadvantage. So to muddy the waters even more, twins & I4's cater to different types of riders also.

[Degsy]

Originally posted by Stoneman
The analogies are for the most part correct. But there ARE high revving V-Twins that still make decent power aobve 10K. That's about where my TL-R REALLY snaps to life. I'd reckon bikes like the Mille and the RC-51 would be similar...

But those are more the exception than the rule...

That's because of the bore/stroke ratio. The more square (bore=stroke) a twin motor is, the more like an inline four it will perform. The longer the stroke compared to the bore, the more like a piece of crap (Harley) it will perform.

derek

[busa413]

Basically you can get even torque and HP out of certain bikes, you just have to keep the revs in a different RPM range. If you keep the revs up hi on an I4 you will have good power, where on a V-twin you can keep it down low. Either are good bikes. Even though I love the BUsa, I love the sound of the V-twin.

[Kham]

i like the v-twin sound on any sportbikes as well but not the potato sound on harley and that is mainly because of the pipe. correct?

[Degsy]

No, it's because of the firing order.

derek

[busa413]

Correct me if I am wrong, but the engines are a little differnt. The cyclinders are mounted at different angles on the Harley compaired to the Sport Bikes. The Cylinders on the Harley will be mounted at a 45 degree angle and on Sport bike it will be 90 degees, so this could also make a big difference in the sound.

[Ducrappy]

I know the 90 degree angle is found on the Ducati motors and is actually considered an L- Twin. The Aprilia cylinders are at a 60 degree angle but I don't know about the rest of the twins having no interest in Japanese twins. I read somewhere that the Harley motor actually fires both cylinders on the same revolution, creating that odd symmetrical sound.

[busa413]

Originally posted by A996S
The 90 degree angle is only found on the Ducati motors and is actually called an L- Twin. The Aprilia cylinders are at a 60 degree angle. I don't know about the rest of the twins, but I do know that all other traditional twins are less than 90 degrees. I read somewhere that the Harley motor actually fires both cylinders on the same revolution, creating that odd symmetrical sound.

I don't see how it would be possible for both cylinders to fire at the same time. It really just doesn't make sense, not sure were the hell you got that from, but I would double check that one. I also don't know where you got your information on the Ducati being the only one that has a 90 degree motor, both Suzuki and Honda use the 90 degree V-twin engine.