Suzuki Burgman modification (aerodynamics + gearing mods)

[AaronD]

Originally Posted by janvos39

In every head design you have to choose the inlet channel so that at max. torque the inlet speed gets to mach 0.5 (approx 160 m/s at max pistonspeed position) for best performance. Honda made some publications on this subject with formulas added to calculate the best dimensions.

Must have to do with creating sufficient turbulence in the incoming charge for a fast burn then? I guess this is getting a little off topic though so I won't try to guess further.

Beautiful work on those 6 valve heads btw.

Aaron...

[janvos39]

Aaron if you like to read more on this subject, then try to get this paper. This explaines a lot.
regards Jan

SAE # 700122: 1970 - "Research & Development of High Speed, High Performance, Small Displacement Honda Engines"

[The Atomic Ass]

Originally Posted by janvos39

OK now that is just sillyness.

[janvos39]

OK for best FE there are probably 4 valves to much in this design. But nice is that the flow of air through this head is large at very low valve lift.

[The Atomic Ass]

Originally Posted by janvos39

OK for best FE there are probably 4 valves to much in this design. But nice is that the flow of air through this head is large at very low valve lift.

Does the lower valve lift translate into reduced parasitic losses through the camshaft for the same volume of air flow?

[janvos39]

That is a good question. I donot think the losses are reduced. There are 4 inlet valves now which represent a larger mass in total than with two inlet valves. So in total more springforce is needed to make the valves following the cam profile.

[AaronD]

So how has the mileage been lately with the new de-bored engine? Or has it been too cold to do much riding? it certainly has here. Will you have numbers before installing the smaller carb so you know what contribution each mod made?

Also, I recall you saying that you were going to add some weight to the new smaller pistons to keep everything in balance. Is that something that you will eventually remove, as well as rebalancing the crank at the same time, taking the same weight off the lobes on the far side? Or will it have to stay?

Last I was curious what your thoughts are about the CVT. Lots of people point to the inefficiency of the pinched belt as a source of loss, but they never couple it with the benefit of keeping the engine so close to its "sweet spot" for much of the time. The high mileage 250 Ninjas and Alert's Faired 125 Honda are all manual transmission, but many high mileage, small displacement stock scooters are CVT. Do you think the CVT on your Burgman is helping or hurting your mileage vs. a manual transmission?


Thanks in advance. Keep up the good work!
Aaron...

[janvos39]

Hi Aaron. Your gess about the weather is right. And when I start riding again I like to have some numbers on the performance with the large carburettor.

The weight for the balancing is added and I noticed no different vibrations. I leave it like this. Reducing the weight brings no big advantage at low revs.

I used the time in this winter to make drawings for an upcoming change. Adjustable inlet valve timing. Adjustable during riding. Like Toyota Prius. Early inlet valve opening and closing for low rev torque. Late closing to get carburettor backflow and have a better ratio of compression stroke vs power stroke. Like the Atkinson approah. More info will follow in due time.

On the CVT. I enjoy the characteristique during acceleration. Even with a high gear (starting in second in my case) acceleration is very well.
If you look at the efficiency of the CVT that is lower than manual transmission.
Info from various sources give efficiency of around 85 percent. Where manual transmission is between 95 and 98 percent. So probably a difference of 10 % in FE can be expected.
Somewhere in the future I will test that.
regards
Jan

[AaronD]

Originally Posted by janvos39

The weight for the balancing is added and I noticed no different vibrations. I leave it like this. Reducing the weight brings no big advantage at low revs.

I thought reducing rotating mass in the engine might have a meaningful benefit. I've heard of lightweight pistons, but admit that I didn't know why they'd be used.

Originally Posted by janvos39

On the CVT. I enjoy the characteristique during acceleration. Even with a high gear (starting in second in my case) acceleration is very well.
If you look at the efficiency of the CVT that is lower than manual transmission.
Info from various sources give efficiency of around 85 percent. Where manual transmission is between 95 and 98 percent. So probably a difference of 10 % in FE can be expected.
Somewhere in the future I will test that.

I've seen similar numbers for CVT vs Manual Transmission efficiencies, but it seems they are all measuring JUST the efficiency of the transmission itself. Since the CVT keeps the engine closer to an optimal RMP range though, there should be some gain in engine efficiency over an average driving cycle when using a CVT vs Manual (depending on when you shift perhaps). So it would be interesting to see what the efficiency is when including both engine AND transmission, instead of just the transmission.

Aaron...

[janvos39]

In this winter (which I hope will leave soon) I have exchanged the original Burgman screen by one of a race motor cycle. As you can see on the pictures. The top angle of the screen is more flat so airflow is directed more towards my helment instead of over my helmet. I hope that the frontal area is reduced a little by this modification.