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Old 10-29-2011, 02:11 PM   #71 (permalink)
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two suggections for you...

Honda makes a 125 for the European market that is almost horizontal (known as an underbone engine) that is available with fuel injection. Or you could consider this kit Small Engine EFI Kit - Small Engine EFI | Engine control as a way of getting the fuel economy you're looking for.

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Old 10-29-2011, 03:25 PM   #72 (permalink)
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Vetter weighing in

RE EFI: My understanding is that EFI is mostly to meet governmental emission requirements. EFI improvements in performance are measurable at high altitudes. EFI improvements may - or may not - be measurable at very low RPM where atomization can be better with EFI. That said, without government interference, carbs are the choice of virtually all racers in virtually all races. They are my choice, too.

Has anybody done a side-by-side conversion test?

I invite you to take a look at the most recent Chapter in streamlining a Ninja 250 We have the body and tail complete. Alan Smith, the owner / builder is putting miles on it as I write. I will report his observations.

I also invite you to meet us in Las Vegas, Nov 20, 9 AM Sunday at the Las Vegas Red Rock Casino for a little 160 mile test of the road to Barstow. We can get to know each other over Chinese food after the ride.
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Old 10-29-2011, 05:41 PM   #73 (permalink)
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Hal - thanks for that EFI link. I've just checked out the site and it's just what I was looking for! The pricing looks reasonable too. If anyone has first-hand experience of the system I would like to get an opinion before purchasing.
My aim was always to upgrade the motor to FI when the initial testing is complete. I know I cannot hit my target 100mph without the 11.5hp that I calculated, and the power hike has to come from an engine rebuild with rebore to 100cc and other mods. However, I want to get the project "on the road" asap, so I will leave the engine standard initially. This means finishing the intake port to mount the std carb, even though I plan to junk it later.
Ref the 125 - this is where I should have started, but its too late now! I would be interested if anyone can tell me if the engine mounting points are interchangeable - that would mean less cutting an welding if I decided to upgrade at a later date. Craig(Vetter) always said he thought the 90 was a bit small, so I'm keeping an open mind until I get it running.

Craig - sometimes you really surprise me! I had imagined a "forward thinker" like yourself would be all in favour of EFI. Carbs may be the choice of a racer, but they have no place in modern vehicle technology. At best they are a blunt instrument which hits the target only by throwing-in fuel "and seeing what sticks".
EFI is actually the "racers choice" introduced in F1 in mid 80's long before govts even understood the potential gains. I doubt if any engineer who has installed a good "fully programmable" engine management system, and completed a calibration with the ease and accuracy available, would ever consider going back to carbs.
Your streamliner would probably benefit from EFI - think of all that foreign oil you are wasting!
I'd love to join you on your Vegas trip (Red Rock Casino Sunday 20th Nov - hope you don't mind the plug) but the bike's a long way from finished and I'm still on the wrong side of the pond. But, I'm gonna make myself a promise - I'll do one of your challenges, once I meet my own!
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Old 10-30-2011, 12:02 PM   #74 (permalink)
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Very cool project you have here! The link by Hal to the fuel injection for small engines, was exactly what I have been looking for for my X-Car power modules. That turbocharger at "Ecotrons" my be just the power adder you need, to get the HP for 100mph.
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Old 10-31-2011, 02:07 PM   #75 (permalink)
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Originally Posted by visionary View Post
Craig - sometimes you really surprise me! I had imagined a "forward thinker" like yourself would be all in favour of EFI. Carbs may be the choice of a racer, but they have no place in modern vehicle technology.
I'm glad you see it that way.
It's not just about how much fuel a vehicle consumes - it's also about what emissions it puts out.
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Old 10-31-2011, 02:47 PM   #76 (permalink)
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Originally Posted by visionary View Post
I think this carb location might give you significant problems, especially at small throttle opening when the fuel will want to pool at the bottom near the carb and not climb up the intake track into the cylinder.

No way to tuck it in under the seat or high off to one side close to the seat crossbar?

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Old 10-31-2011, 02:49 PM   #77 (permalink)
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Carbs are the choice of a racer?
Are you talking about NASCAR?
Indy cars have been EFI forever, at least 50 years.
Ask any early WW2 Sptifire pilot about the ME 109 on his arse with the DB 601 fuel injected inverted V12 engine. His only chance was a hard turn, to the right, that did not cause his fuel to slosh over to the side of the float chamber and starve his engine. The 109 had weak wings.
Ask any pilot of a B29 about the engine problems with that plane that were solved when they went to fuel injection on the exact same engine after the war.
Ask any Mercedes driver after 1955, or a Chrysler 300 after 1957.
Craig, I would suggest you find someone with a Honda CBR250R to try a similar configuration to the 250 Ninja that you are working with the owner on modifying. Mine (Honda) has averaged right at 84 MPG with no modifications. I would bet with your aero expertise it would easily top 100 MPG in your contest. With taller gearing it might get much higher.
Nissan went to EFI in their Z cars in 1975. The primitive Bosch derived FI allowed them to pass Federal emissions without any catalyst or even a EGR. Compared to the carburetors of the same era performance was outstanding.
Today everyone should look as Mazdas SkyActive fuel injection. Direct (into the combustion chamber) FI which actually has 5 separate injection pulses directly into the combustion chamber DURING THE COMBUSTION PORTION of the power stroke. By modulation of the fuel delivery while combustion pressures are at their peak, they can spread the power peak out over a much longer portion of the power stroke. This allows them to run 14 to 1 compression ratios on regular fuel.
None of that would ever be possible with a venturi controlled suction vaporization carburetor. The best bike carbs today are the constant velocity variable venturri setups. Based on the old SU types dating back to the 1930s they are very good at efficient delivery of fuel but when you add freezing temperatures they have serious icing problems that require preheating of the intake air for resolution. Lets not even consider the gross emissions problems from incomplete atomization of the fuel.
Not meant to be combative or a slam by any means, but fuel injection si the future. Carbs are history.

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Old 10-31-2011, 04:26 PM   #78 (permalink)
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Less hp with EFI

The February 2011 issue of Scoot Magazine has a pretty nice little story on p29 comparing the dyno results of a carbureted Vespa LX150 vs a factory injected LX150. I have asked their permission to reproduce the story. In the mean time, their dyno chart shows that the carb Vespa puts out more power all the way thru the curve, maxing out at 6.8 hp vs 6.42 hp for the injected version.

The article suggests that the injected LX150 burns less gas. Of course it would burn less gas. It produces less horsepower. It better complies with governmental regulations. It also costs $300 more.

Besides better performance at various altitudes, I have since discovered that EFI units are not affected by the wretched American gas that clogs tiny orifices. That could be good if you don't ride much.

Still... 6.8 hp is better than 6.42 hp.

If I get permission to show you their graph, I will post it.

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Old 10-31-2011, 04:33 PM   #79 (permalink)
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That the carb'd version puts out more HP vs EFI is NOT a result of it being carb'd; it's a result of the ways the two versions were tuned. It appears the EFI version was tuned to meet emissions standards.

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Old 10-31-2011, 07:42 PM   #80 (permalink)
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My understanding is that EFI is mostly to meet governmental emission requirements

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