Suzuki Burgman modification (aerodynamics + gearing mods)

[janvos39]

Today I finished the installation of the additional gear on the Burgman.
The pictures show how the gear is connected to the lever on the left hand side.
It only takes a thumb movement without taking my hand from the handle bar to shift up or down.
A first ride shows that shifting up is best done by approx. 45 mph.
Shifting back to low is best done at low speed of 25 mph to make it smooth.
Although also from very low speed it is possible to stay in second without hic ups of the engine.
First test on the highway gave a topspeed over 100 mph. Thats where I stopped , it ran out of scale. Gearing in total is 25% different from standard in combination with improved aerodynamics this made the improved topspeed. Although I am not going to use it in my daily travel to work, it is nice to know that you have some spare speed available under the right hand grip.
What it brings on FE is to be seen after some tank fills.

[The Atomic Ass]

I like the setup, but I certainly hope you are not a knee dragger.

[janvos39]

Good point Ass. I will modify to avoid damage at fast cornering.

[janvos39]

Above the first two tank fills with the additional gear on the Burgman.
MPG us . A big step forward in the FE. The new gear drops the rpm with 25%.
No change in driving style and same route.

[cvetter]

Gearing our engines up confirms what we all suspect. Run the engine slower, generate less horsepower, burn less fuel. I have studied your pics and I don't know how you have geared your Burgman up. If you cut new internal gears, what is all the external mechanism?
I'd love to understand what you have done...

[theycallmeebryan]

Originally Posted by cvetter

Gearing our engines up confirms what we all suspect. Run the engine slower, generate less horsepower, burn less fuel. I have studied your pics and I don't know how you have geared your Burgman up. If you cut new internal gears, what is all the external mechanism?
I'd love to understand what you have done...

Running longer gearing like this doesn't "generate less horsepower". In fact, it may be about the same, but more load. The increased efficiency effect is coming from lowering the rpms. The less the exhaust makes a pop, the less fuel is being burned.

You well know this craig!

[cvetter]

Well, I see these pictures but don't have a clue as to how this gears up the Burgman. And I am not certain about the connection between rpm and burning less fuel. I think there is a connection between producing less horsepower and burning less fuel. For example, I think the ideal situation would be this: Lets assume that the streamlined Burgman needs 15 hp to go 70 mph. Lets assume it is now geared so the engine turns about 3,000 rpm at 70. This is the time I think we need cut a new cam that maximises torque at 3,000 rpm.

I still don't understand what is going on different inside this Burgman. Is it posted somewhere?

Thanks

Craig

[dcb]

Originally Posted by theycallmeebryan

Running longer gearing like this doesn't "generate less horsepower".

It probably does make a lot less power than peak, but is more efficient at converting any fuel given to it into power, look at a typical bsfc chart:

Peak power for an engine is where torque*rpm is at a peak, probably up in the 5000 rpm range, but peak efficiency is where fuel consumption/power is at a minimum, around the 2500rpm range and 3/4 available torque.





Edit, also could use better understanding of the gearing change implementation too please.

[janvos39]

The streamlining of the burgman resulted in less needed power. This can be noticed on the amount of throttle which is needed for a certain speed. So by using less power at that speed the specific fuel consumption due to the lower load is less good. So overall gain is marginal as can be seen on the earlier tank fills. What happens by changing the gearing is two positive things concerning the FE. Lower rev means more load so specific fuel consumption gets better and due to the lower revs the engine losses are lower as well. Rule of thumb for these losses is that you loose 1 liter per hour fuel with 1000 cc engine at 1000 rpm. So my losses have gone down at 75 MPH from 0.385*6.548-0.385*5.098=0.558 L/hr
The engine in standard trim runs 6548 rpm at 120 km/hr . With this modification it is now 5098 rpm at 120 Km/hr.

[cvetter]

Yeah but what exactly did you do inside the engine to slow it down? What are the levers on your handlebar for?

Craig