GHonda GX 35, Tuning help?

[BradenM]

Hi everyone;

First, a little background:
In my hiatus I have been racing/riding bikes in training for an event we have down under called the RACV Energy Breakthrough. I race this vehicle:

around a 1.2km street circuit for a continuous 24 hours with my team.
It's a recumbent tadpole trike, with 2 front and 1 rear (drive) wheel. This vehicle is a hybrid 1, which means it's powered by both a motor (electric petrol or diesel) and pedal power.
Currently we are using pocketbike 50cc 2 strokes with custom built expansion chambers. Very fast, however very inefficient. The aim of the event is to design and produce environmentally friendly hybrid technologies that could replace cars in the future that would be easily accessible to the average joe.

Heres the catch: 2 Strokes use a hella lotta fuel, and are inefficient compared to the below 4-stroke. There's Over 800m straights to use our fuel allocation of 3 liters on.
3 liters doesn't last 24 hours with a 2-Stroke (although, in fairness, no other vehicle can match the speed).

So we have this now:

It's a Honda GX35 OHC 360 degree inclinable 4-stroke. As far as drivetrain setup goes, thats childs play, but we are stumped on how to make it more efficient without compromising power or torque? We will also be adding electric start capability; something thats going to have to be ghetto-rigged to the recoil side..

Thanks in advance;
Braden.

 

[sideways]

make a free flowing exaust (no mufflers if you can), use the least restrictive air filter u can get(or no air filter if you want to risk it). Jet the carby to perfection once you've done that. Little things like filing down the screw that holds the throttle butterfly can make a difference. All of these things will not only increase the efficiency of the engine but the power too.

Depending on your budget you could get your camshaft reground for maximum efficiency but this will decrease the power of the engine.

I wouldnt bother with the electric start, instead make it so when you pedal it turns over the engine and starts it. I also dont think that the clutch that the engine comes with will have enough "bite" to work very well, if at all.

Good luck!

Hayden

 

[BradenM]

make a free flowing exaust (no mufflers if you can), use the least restrictive air filter u can get(or no air filter if you want to risk it). Jet the carby to perfection once you've done that. Little things like filing down the screw that holds the throttle butterfly can make a difference. All of these things will not only increase the efficiency of the engine but the power too.

Depending on your budget you could get your camshaft reground for maximum efficiency but this will decrease the power of the engine.

I wouldnt bother with the electric start, instead make it so when you pedal it turns over the engine and starts it. I also dont think that the clutch that the engine comes with will have enough "bite" to work very well, if at all.

Good luck!

Hayden

Thanks Hayden.
The budget is more or less unrestricted, and decreasing power really isn't much of an option.
With the pedal start on the motor, thats a good idea, but in practice, tuning the engagement speed, e.t.c. and then having some kind of disconnect (other then grounding plug wire, because you will still lose a small amount of fuel) would be mechanical, and mechanical things have to be spot on to last 24 hours.

We convert the engine to fixed drive, no clutch (or rather, clutch drum has material added to inside. engagement RPM of 1rpm). Then that runs through a custom 1 way clutch, allowing the bike wheel to coast independent of the engine, however as soon as engine is running power is contributed to the rear wheel. It's much more efficient over a 24 hour period then is a clutch setup. Every rotation of the engine contributes to the forward motion of the vehicle, and the vehicle can move forward without the engine rotating.

Thanks heaps for your suggestions! I'm compiling a list

Braden

 

[sideways]

hmmmm well i been thinking and you could do something like this

(sorry for the crappy diagram)

theres a chain inbetween the motor and the clutch coz whipper snipper motors crankshafts can break very easily so that will put as little strain on the crank as possible, you could adapt a small motorbike clutch too.

another idea, you could adapt a HUGE flywheel to it (on a jackshaft maybe?), i dont mean a flywheel from a brigs flatty or sumthing, more like the kind you find on hit and miss engines. then you could run the engine at like 500rpm with lots of torque but barely any power.

Hayden

 

[Rickracer]

The biggest change you can make to that motor is to increase the compression ratio, that will get you more power and efficiency out of every drop of fuel. You could also experiment with increasing the ignition timing. I'd also recommend cleaning up any casting flash in the intake and exhaust ports, rough up the intake slightly, polish the exhaust, backcut the valves, free flowing exhaust and air filter.

 

[BradenM]

Cool, thanks Rickracer, thats the kind of stuff i'm looking for.

Hayden, I'll take some photo's tomorrow of out drivetrain setup and post them here. It's very successful and efficient-not a single breakdown over any race we have done. I really appreciate the diagram

 

[garp]

My gearbox would be good in your application.
I also use a Honda, I'm interested in how you improve the efficiency. Great sport!

 

[redsox985]

Garp, may I direct you to the thread called Posting and You!. Being that this hasn't been touched since October 22, 2009, I feel safe to assume that the issue has been solved. Especially because it is a school related project. Thank you. It should brief you on basic forum "etiquette," the grammar end although, you have down pat.

 

[modelengineer]

If you have time and the skills converting it to fuel injected would make it much more efficient. If you use Megasquirt it shouldn't be too expensive, and you can fine tune the fuel map to run lean at certain revs to save fuel, etc.

The gearbox shown on this website is a good idea IMO, since chains are quite efficient. If you could encase the gearbox and run it in a very thin oil bath then you could use roller chains which are more efficient than an o-ring or x-ring chain. If you're just travelling at one speed most of the time though I would just use a single chain as it would have less energy loss.

*EDIT* Just read your post redsox. It's so annoying when people bump these ancient posts.

 

[r97]

rotary engine!!!!???????

 

[redsox985]

How about that H2O engine, eh? Or solar power. Batteries are heavy. I suggest nuclear power. EXTREMELY efficient and EXTREMELY powerful. Who wants to drive. How much does victory mean to you. 3 volumetric liters of nuclear fuel will get you FAR.