Suzuki Burgman modification (aerodynamics + gearing mods)

[AaronD]

Looks very good. Would be nice to know separately how the debored engine and windshield swap affected your mileage. Was it an easy swap, or required changes that make it hard to go back?

Any info yet on the variable valve timing project. That seems VERY interesting. I see Alert has spent his winter decorating and adding new mirrors, while Craig Vetter has tried to persuade Honda to sell him a 125 in the US (not available here now). I'm much more curious to see what's been on your drawing board while the snow flies outside.


Aaron...

[janvos39]

Aaron. I am making a set of gears for Craig Vetter. It is about time that he can show his potential with that streamliner.
I made the drawings for the parts of the variabel valve timing mechanism. Also here are some gears involved to make it possible. I made the gears already. Have to work now on the housing for the gears and the modification of the camshaft. I have to cut the intake cam looose from the camshaft and make the gears inbetween the inlet and the exhaust cam. I believe this is a little bit a cryptic explanation. But when I have pictures of the drawing and the parts it will become clear.

Changing the windscreen back is not easy. I know that every body likes to see the step by step approach proven by data. As long as I donot have a type of scangauge it will be difficult to get thoose data. So my philosophy is to try to head in the good direction. Looking at pictures in books like Hucho and try to copy some ideas. Although I am planning to get a data logging system which will record a number of functions, so that on the PC I can look back on it and try to figure out where to go next.

[AaronD]

I agree that its past due time for Craig to show what his nice streamlining has really done for that Helix. The stock CVT has been holding him back. Kudos to you for stepping up to give him a boost in the right direction.

And I agree with you 100% on the idea of keeping moving along in the right direction instead of delaying further progress in favor of logging data on each baby step. Way to keep plugging along.

Have you had any luck on the improvements you wanted to make on the smaller carb (from a 250cc wasn't it)? I was also curious what you thought about the idea of carb vs. fuel injection. Would probably have to start with a different donor engine, but have been reading good things lately about efficiency of small FI engines.


Aaron...

[janvos39]

The test with the two seizes of carburettors is not started yet. I did some initial test drives with the 36.5 mm bore carburettor(from the 385 cc engine). No problems in lack of torque ,so I will drive some kilometers to get FE numbers before switching to the 250 cc carb. (30.5 mm bore) This will be a drastic change in crosssectional area (70%)
See what that brings. I need to solve the linkage to the large carb from the ingition adjust lever. Do not know the details, but the lever has a switch linked to the ignitionbox. No more details in my documentation.This switch is not present at the small carb.Maybe somebody knows?

Fuel injection is the preferred way of feeding gasoline. Only feeds the engine when gas is needed. Off during engine braking.
And the control feedback loop with the oxygen sensor in the exhaust takes care of the variations in amount of filled air , better then a carb can.

[janvos39]

One of the many things I like to try is modifying the inlet valve timing during riding. I will test to find the best timing for FE. This can be early valve closing like the Metro XFi camshaft or late closing to create Atkinson effect like used on the Toyota Prius.
To be able to test that I am making a mechanism that allows timeshift from the handlebar.
I split the inlet cam from the camshaft and drive the inlet cam via a gear train from the rest of the camshaft. Now the cams run a different direction. By turning the housing of the gearset around the camshaft center I can change the inlet timing.



Here the gear set that goes into the housing.

[Christ]

Very impressive.

[AaronD]

Very nice. Can't wait to see how that works out. If I'm reading correctly, you're not changing the duration of the inlet valve opening, but the timing of when it opens/closes, right?

Speaking of gearsets, does Craig Vetter have his new CVT set installed yet? I haven't been following him lately.

Last, I've been looking at engine donors for a similar high mileage project and recently stumbled on the '09 Suzuki LTZ 400 ATV. It peaked my interest because its the smallest EFI engine I've been able to find. There is someone working on a bolt-on EFI replacement kit for GY6 engine (up to 250cc) carbs, but its not available yet. I thought the 400cc ATV might even be the same engine as your Burgman since they're both Suzuki, but a quick search on the specs shows its a 398cc engine with much different bore/stroke (90 x 62.6) than your '99 Burgman which was 385cc (83 x 71.2). I started looking at smaller Suzukis for a possible de-bore mod like you did, but before I get too far down that road I was curious how changing the swept volume would affect the EFI mapping and what it might take to adjust and retune that. If its too complicated/expensive, it might be worthwhile finding a different engine donor or sticking with the stock 400. I know that one of the advantages of EFI is that it auto adjusts for some changes (temp, elevation, etc.), but didn't know how it would behave if it was only working with 300 or 250cc instead of the 398 it was built for.

Any insight you can provide on how the EFI works or what it would take to modify it?

Thanks in advance,
Aaron...

PS. Sorry about this drifting off topic a bit, but the forum won't let me post PMs or e-mails without a higher post count, and I don't wast to throw meaningless posts in just to pad the numbers.

[janvos39]

Aaron. Indeed the mechanism I am making shifts timing during driving. I have no plan yet to also change cam duration, but that might come depending on the results.
Craig Vetter is doing a try out this week. You can follow his website chapter 33 on that.
On the EFI question here my thoughts. I think that the EFI delivers an amount of fuel based on the measurements of amount of air and the lambda sensor voltage.
So downsizing an engine should work with the EFI of a larger capacity engine.
I have somewhere on my long wishlist also an EFI system for my Burgman. Although with the large carburetter of the 385 cc on the downsized 300cc I run at this moment (after a first tank) 78 MPG. Probably I can improve on this.Aaron check your PM

[redyaris]

Do you have an update on the smaller carb on your 300cc motor? I see that Craig Vetter is at 90mpg with the new gears you made for him.

[janvos39]

Hi Redyaris.
I had a problem with the overruning gear in the gearbox. It didnot bloc anymore in one direction so I had to repair. I use only high gear at the moment.
Besides that I was also quite busy with making a special gearbox for a Toyota yaris for ralleye cross.
Indeed Craig has made a jump in his best MPG with the new gears.
The small carburettor is not yet tested. I am preparing a logging system that will log a number of functions of the Burgman during driving. On the carburetter I will place a potentio meter so I can read in the logfile the opening of the throttle.
Also position of the variable cam will be monitored and other obvious functions like revs speed temp of water