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I was afraid I was providing WG with erroneous info regarding rpm @ xx mph, so I posted to the CB1100 forum and asked if 2750rpm in 6th gear at 60mph was correct, and one of the moderators sent me the following info. Each had an accompanying dash photo which I didn't include here:MPH Gear Rpm55 6TH 250060 6TH 275065 6TH 300070 6TH 325075 6TH 350080 6TH 3750Bob
It sounds like a nice motor, sorta tuned like a twin. Hmmm
I'm curious to know how it is tuned like a twin. Do both sets of pistons reaching TDC together fire together (as opposed to the conventional one on compression, one on exhaust stroke), or is there some sort of crossplane crankshaft arrangement?I did a Google search, but just got confused.
I think what most of us would like to understand is how this engine design differs from most fours. It simply defies my logic of a typical 1100cc four.
It's very common for 4-cylinder Japanese bikes to have very good low and midrange torque. I recently rode a friend's Yamaha FZ6R, and it had amazingly good low end torque, and didn't require high revs for good acceleration.
Not intending to be obtuse, Kev. Just trying to understand how a four can emulate a twin.
How Jim? Explain the physics of an inline with redline to 1500RPM and one only to 8500RPM. I'm thinking it must be throw or weight?
I'm assuming you're not both just being obtuse but instead we're having a difference over a colloquialism.
I'd love to hear the argument that says a big bang four has more torque than a conventially fired at one every 180 deg.
The Honda doesn't emulate a twin; just a twin's most common operating configuration.
Aren't firing intervals on a Harley integral to the reasons they make so much torque so low on the range, like 2k on?
No, the long stroke and low RPM tuning is the reason. The firing interval is just an anomaly of the single pin design.
Harleys just appear to have lots of torque down low because they require a heavy flywheel because of the inherent unbalance and firing pattern. It reduces quickly as the revs increase, necessitating a gear change. A Guzzi motor has a much flatter torque curve that is maintained through the rev range.Not Harley bashing, I owned one for nine years.
There's a guy here in Victoria called Brad Black, an acknowledged expert. I'd be surprised if Roper doesn't know him. He told me once that an R1 Yamaha has more peak torque than a biggish Harley. Albeit at a monumentally higher figure, but anyway it's probably an easy thing to research, I never bothered.
Here's the torque curve of a Suzuki Hayabusa. It doesn't come on quite as low as the big twins, but it sure is broader.
There's no question from the dyno charts I've checked that Harleys produce a lot of torque and it starts down low.Just compare the dyno for an 883 to a V7 or FZ6. Or take a look at a 1200 Sporty torque comes on big and down low.I don't recall any Tonti Calis having similar torque numbers even if their charts were relatively flat.
Have you ever ridden a Cali 1400, Kev?
As a general rule I was always taught long stroke equals high low end torque and lower revs. Short stroke equals power in the upper rev range and higher revving motors. Some data...CBR600RR bore is 1.57 times the strokeBreva 1200 Sport bore is 1.17 times the strokeCB1100 bore is 1.09 times the strokeXL1200R bore is .92 time the strokeOf course intake length, cam lift and duration, head shape, number of valves, spark timing, exhaust restriction, and fly wheel size among other things can change characteristics to a point. But basic engine architecture is the starting point. Personally I like an over squared bore x stroke motor that will give me some revs. because I don't like short shifting as a general rule. The above number show why I like the 1200 Sport V twin motor so well. They love to rev!