MPG Transmission Mods

First topic message reminder :

Not wanting to hijack the 'Weight & MPG mods' thread I thought that I would put this out for discussion. Anyway, my 2¢:

The best mileage I ever got was when I was using a Sumitomo rear tire. The larger diameter of the tire altered the transmission ratio  to the point that my cruising RPMs dropped ~500 rpm. That was over and above the overall RPM drop already achieved by using 30gm Dr Pulley sliders.

All of that speaks to the fact that the major obstacle to better economy with the Silverwing is inefficiency of the CVT transmission. Transmission being the drive line beginning with the crankshaft output and ending with the rear wheel. There are plenty of 600-750cc motorcycles out there which consistently get better MPGs due to their geared transmissions.  

So the trick to better MPGs then is to reduce the CVT slippage and/or alter the transmission ratio. A Dr Pulley HiT Clutch reduces clutch slip by locking up the shoes to the clutch bell, and variator sliders alter the variator 'timing'. However there seems to be no way to reduce the belt slipping --which is the major inefficiency.

Aftermarket variators not only alter the variator weights 'timing' by changing the weight-ramp angle but may also alter the belt-face of the moveable pulley sheave. Traditionally those after market variators do not change the fixed sheave of the variator. So maybe it is possible to 'tune' the variator by altering the face of an OEM variator sheave and effect how the belt acts at various RPMs. And given that at cruising speed the belt is riding close to the maximum diameter of the drive pulley, then if the pulley could be altered so that the belt rides at the max diameter then the drive ratio should be reached at a lower RPM and/or the drive ratio changed. Much like changing to a larger sprocket on a chain driven motorcycle.

Tim

Those RPM@MPH figures are lower than the traditional figures I've seen mentioned.

Given your Engineering background it's a real shame that you can't get hold of a set of Dr Pulley sliding weights. They do effectively alter the angle of the roller ramps. It would be nice to get your take on them.

Notwithstanding dyno testing and engineering equations, ultimately scooter riding is a seat of the pants experience.

Tim

Cosmic_Jumper wrote:

Given your Engineering background it's a real shame that you can't get hold of a set of Dr Pulley sliding weights. They do effectively alter the angle of the roller ramps. It would be nice to get your take on them.

I'll have to compare with my wife's bike when I get a chance because I never did anything to hers.

I got a set of sliders in the variator on my Chinese scooter. If your original ramps and rollers are worn, then sliders are probably good idea because they renew performance without having to replace worn ramp or pulley half. I don't remember what the specs were on my Chinese scooter. The local scooter shop has a big tray with all kinds of rollers and sliders in it because people are changing them all the time in those Chinese rides. But he don't have any for Silver Wings.

You get 5mph more speed for only 200rpm more engine speed? That's 25mph per 1000 rpm. At 8500 rpm redline that would put you north of 150mph starting at 65mph and 4600rpm.   

LDB wrote:

You get 5mph more speed for only 200rpm more engine speed? That's 25mph per 1000 rpm. At 8500 rpm redline that would put you north of 150mph starting at 65mph and 4600rpm.   

That's assuming the engine would make redline on a balls-out run (it probably won't).

I took the torque sensor pulley off this morning to lubricate the bearings in there (should've done this the other day, and have to do my wife's too). The needle bearing was fine, but that little ball bearing on the outboard end had spun all the grease out of it with time and needed repacked.



It's too bad somebody doesn't make a full transmission "reprogramming kit" to change these things. It would be incredibly simple to do - either change the weight or springs in the clutch to make that engage when you want, and stay engaged at lower rpm. I managed to get some improvement in that with heavier rollers. But the place to do it is in the clutch.

And offer a kit with a different torque spring and roller weights to change the gearing profile to what the rider prefers. The rollers (or sliders) only accomplish half of what it takes to completely reprogram the gear ratio curve to either lower or higher ratios at a given engine rpm and road speed.

I believe Dr. Pulley makes all that stuff with their HIT modifiable clutch and their different slider weights.

Malossi makes an upgraded Driven Pulley torque spring, as well as an assortment of "heavier" clutch springs for the OEM clutch and different roller weights for the variator.

My wife and I went for a 64 mile ride this afternoon. We checked fuel mileage just for the heck of it. Her bike turns 300 more rpm's at highway speeds than mine does and she STILL gets better fuel mileage with her bike that I get with mine. Mine figured out to 52.7 and hers figured out to 53.5.

I think I may have figured out the key to getting better fuel mileage - lose about 65 lbs. LOL!

Chris go do the same 64 mile run with you on her bike and her on your bike. See if you get better milage or equal after the switch.

Long term, and Sturgis/Yellowstone in August and a run to Alaska in early Sept, plus all my other riding gives me 12,200 miles on those heavier rollers.

My conclusion in the long term is that they did absolutely nothing to enhance fuel mileage or highway performance. They make the engine run at lower rpm before the transmission shifts to high ratio, which for me makes the bike more enjoyable to ride. I never rode my other bikes around town in 1st and 2nd gear and I don't like an automatic transmission that does either. So that part I like.

But for those searching for that elusive fuel mileage - it didn't do it. The Silver Wing is a heavy bike for a 600. But that weight, despite hurting fuel mileage some, is well balanced and part of what makes it one of the best long distance touring machines I have ever ridden. Breakfast on the opposite coast? No problem. Let's roll. The fuel tank could stand to be a bit bigger, but even that is not a big problem because I don't mind getting off to stretch my legs a bit every 2-3 hours anyway.

So that's my long term report on adding weight to my variator rollers. The one and only thing it did was lower the engine rpm's a bit for normal city riding, and more positively lock the transmission into high ratio for highway riding, which for me is a desirable thing.