Small injector, about 9lbs per hour

For discussing injector selection, manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
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the bubbler
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Joined: Wed Oct 19, 2005 8:43 am

Small injector, about 9lbs per hour

Post by the bubbler »

Hello,

Any suggections for a donor for such a small injector?

The Honda pantheon scooter looks a good bet, but these are difficult to find (well, impossible) in bike breakers, as they are very new.

Any suggections?

Andy
PSIG
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Location: Poulsbo, WA

Post by PSIG »

If you look at some of the reference sites listed by Lance in the sticky (http://www.msefi.com/viewtopic.php?t=2576) you'll find several places to start your search. For example, on Stan Weiss' site, he lists several injectors in that range. As far as what makes and models you might find at the scrapyard, it shows some BMW's and Fords having Bosch and ND injectors around 12 to 13 lb/hr.

Using the calculator in the MegaManual, these will squirt about what you need at 20-25ish psig of fuel pressure. Depending on the application and injector placement this could work well. We are running a D16 Honda with only 16-18 psi fuel to oversize injectors with no ill side-effects.

Hope that helps,
David
the bubbler
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Post by the bubbler »

Thanks for the advice.

I want to port inject a 300cc 4-stroke single cylinder engine.

Does running a lower pressure have a detrimental effect on fuel atomisation?

Andy
PSIG
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Posts: 201
Joined: Fri Jun 11, 2004 11:02 pm
Location: Poulsbo, WA

Post by PSIG »

Pressure does affect atomization; but in my cleaning and testing ventures I have found that, with most port injectors, the atomization is not nearly as important as the injector placement, fuel impingement (will it hit the opposite wall or the back of the hot valve?), runner design, airflow and velocity factors. Others on this list have found similar results. Do your best to provide good placement for the injector and give it a whirl. Keep the above factors in mind. EFI is not as sensitive as most imagine.

Finally, if you pick-up one of the potential injectors and test it with varying pressure with a suitable fluid (mineral spirits works well) you can check the spray pattern and atomization for yourself and determine if it's what you want or need.

All of the answers you get will mean different things depending on the big question: What is the goal of this EFI project?

David
the bubbler
Helpful Squirter
Posts: 37
Joined: Wed Oct 19, 2005 8:43 am

Post by the bubbler »

Hi,

The engine is for a small BMW Isetta bubble car.

Original equipment is a small piston valved Bing carb with a 22mm choke, ignition is points based with mechanical centrifugal advance.

The engine produces 13bhp and about 14 lbs per ft of torque.

I would like to improve drivability of the car using more sophisticated fueling and mapped ignition, and also improve the torque figure so that I can pull a taller final drive easily.

Andy
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