Honda GX31 - Smallest Squirt EVER?

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Gareth
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Honda GX31 - Smallest Squirt EVER?

Post by Gareth » Sat Jun 14, 2008 12:28 pm

Had some more success today when we upgraded our MS1 (2.2) to a MS2 Daughter board and connected it to the loom I'd made for our Honda GX31 4 stroke strimmer motor. After getting it warmed up on the carb, we switched fuelling to the injector and pulled the start cord. Not only did it run, but with a bit of weakening of the mixture (Tech Edge WBO2) it revved up pretty fine too (with some light load on it) and with further tweaks ran until the fuel tank was empty. OK so it's only used 60 cc of petrol and it's only 1.5 HP, but it ran! Got some issues that needs sorting, like the injector locks on sometimes when trying to start and floods the engine?? And the rpm reads double what it really is (wasted spark magneto sytem triggering a VR sensor).

Comments and suggestions welcome......

Thanks again to the MS community, this really is learning......

Gareth

sakais
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Re: Honda GX31 - Smallest Squirt EVER?

Post by sakais » Sun Jun 14, 2009 12:24 pm

Hi
I was wondering, what size fuel injector are you using?

Gareth
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Re: Honda GX31 - Smallest Squirt EVER?

Post by Gareth » Sun Jun 14, 2009 11:04 pm

The injector is a special unit made by Bosch for the competition - 10 grams/min. It is available from http://www.eshopsem.com/cataloguegb.php but they may not supply to you unless you are an entry. Depending on your engine size you may have some success with 'normal' motorcycle units although your idle may not be wonderful.

Good luck

Gareth

sakais
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Re: Honda GX31 - Smallest Squirt EVER?

Post by sakais » Wed Jun 17, 2009 2:20 pm

Thanks!
Also, do you have any recommendations for an off-the-shelf throttlebody? Or is fabrication the only way to go here?

Gareth
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Re: Honda GX31 - Smallest Squirt EVER?

Post by Gareth » Wed Jun 17, 2009 11:15 pm

We added a TPS to the existing carburettor on the GX31 by grafting a spindle onto the plastic throttle arm assembly - quite tricky. On My Honda 90 cc engine which has a slide throttle pulled by a cable (ex-motorcycle) I added a linear pot via a link to the throttle pedal. This works well enough although not as rugged as normal automotive stuff. I could take pictures if you want - email me direct to tsr@trinity.croydon.sch.uk and I'll get onto it if it helps.

It's all fairly crude, but it runs and on the Honda 90 at least is better than the carb in term of fuel economy.

What is your project?

Regards

Gareth

sakais
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Re: Honda GX31 - Smallest Squirt EVER?

Post by sakais » Tue Jun 30, 2009 8:12 pm

Thanks again for the info!
I am working on a project where I am going to attempt to fuel inject a gx25. I still havent picked out an engine management system but I was looking at the MS which is how I came across your post.
I am going to try to order a couple of those bosch injectors from shell which hopefully shouldnt be a problem.

I was thinking that in order to mount the injector, I would have to fabricate a new manifold so I might as well incorporate a throttle as well. I guess you somehow incorporated the injector into the carb manifold?

edwinjohn_perey
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Re: Honda GX31 - Smallest Squirt EVER?

Post by edwinjohn_perey » Mon Nov 02, 2009 6:50 am

glad to came across this post.. did you join the shell eco-marathon competition? we are joining the SEMasia this coming july.. how did your team do? we are thinking of using the honda gx31 engine.. thanks!

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