Digital Fuel Injection for Chinese 2-stroke motorised bicycle engines

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Mechanical fuel pump... electric fuel pump would be a pain to use as you have to have variable fuel pressures.... 3 at idle at 6-10psi at WOT.
 
It's already been done - a company called Rock Solid Engines is selling nitrous kits for Chinese motorised bicycle engines and from memory it uses an electric fuel pump to spray in extra fuel metered to the nitrous delivery system.

I was looking at digital fuel injection as adding simplicity, not complexity as it could and would be a set and forget system in closed loop mode, i.e.


add a tuned pipe - wammo - the fuel injection system just compensates - no fuss

add a cylinder with different porting - the fuel injection system just compensates - no fuss

Add nitrous - the fuel injection system just compensates - no fuss

Change fuel type or density - the fuel injection system just compensates - no fuss


I've done some research and an Italian company (Bimota) made a 2-stroke 500cc v-twin sports bike.
It used fuel injection but wasn't very reliable as a first generation direct injection 2-stroke, but they made it work, when it was working.

Fabian
 
I was looking at digital fuel injection as adding simplicity, not complexity as it could and would be a set and forget system in closed loop mode, i.e.


add a tuned pipe - wammo - the fuel injection system just compensates - no fuss


Fabian

EFI doesnt exactly work like this though. You have to have a really intelligent ECU to do this... they cost in the upward thousands. Otherwise you have to actually sit down and program your fuel curves everytime you change something, as a 2 stroke motor works more like a supercharged motor than a N/A motor. Fuel injection is not as dummy proof as you'd think.
 
Numbness in the groin area can leave a man completely oblivious to risk. Only reason I can give.
 
Hi Foximus

It's probably becoming rapidly obvious that i know very little about the deeper technicial aspects of fuel injection.

I just made a bad assumption, that in this day and age of home computing power doubling every 18 months, that we would (by now) have ECU units capable of doing everything in "automatic mode" for a couple hundred dollars.

And i made a bad assumption, you just install the thing like a Chinese CDI unit - connect blue wire to blue wire and black wire to black wire and hit the button labeled "auto mode".

It's not as simple as i would have hoped it could have been.

Fabian
 
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The microcontroller isn't the expensive part of an EFI system. There was a similar thread a few weeks back about EFI for small engines. The chips were about a buck a piece in production quantities. The expensive part is the electric fuel pump, all the sensors and the injector itself.

If an enterprising person could invent a simple EFI setup that would run off of a magneto, be self contained, and cost less than $25 - they'd be an instant billionaire. As emission standards for small engines get tighter, first you'll see the two strokes go extinct (surpised to see them around now!), then the little four strokes will go away.

It'll be wimpy electric lawn mowers, string trimmers and electric "assisted" bicycles. Blech.
 
The microcontroller isn't the expensive part of an EFI system. There was a similar thread a few weeks back about EFI for small engines. The chips were about a buck a piece in production quantities. The expensive part is the electric fuel pump, all the sensors and the injector itself.

If an enterprising person could invent a simple EFI setup that would run off of a magneto, be self contained, and cost less than $25 - they'd be an instant billionaire. As emission standards for small engines get tighter, first you'll see the two strokes go extinct (surpised to see them around now!), then the little four strokes will go away.

It'll be wimpy electric lawn mowers, string trimmers and electric "assisted" bicycles. Blech.

All the more reason to strike hard in 2010!
 
well if it was set up to run in closed loop, the computer would make NO adjustments to the fuel injection. closed loop is a fixed setting. when it is in open loop, that's when it (and you) will make adjustments to the fuel curve. for example, when you first start your car on a cold morning the computer runs in open loop so that it can get the air temp, exhaust temp and all that, to adjust the fuel curve to make the engine run right.
once the engine is warmed up, it switches to closed loop. this is how and why fuel injection does not require a choke like a carb does.
also, if you add nitrous to a f.i. motor, the computer WILL NOT automatically add more fuel. if you add nitrous to a f.i. motor, you have to increase the size of the injectors, and add a secondary fuel line to add more fuel when the nitrous is activated. this second fuel line would be tapped into the return fuel line and would be hooked to a solenoid. when you push the nitrous button a nitrous solenoid and the seconadry fuel solenoid are activated, spraying both the nitrous and the fuel from the return line into the intake under pressure. the more nitrous you use, the more fuel you need to add. i think that the kits for these 2 stroke engines add a small enough amount of nitrous that you could get away with just running the carb a little rich to compensate for the extra fuel needed. i don't see you having to run a secondary fuel source into the carb. for the nitrous. now when you are talking a 200 horsepower nitrous set up, then it is crucial to add more fuel. the other thing about nitrous is that you actually need to retard the ignition timing 2-4 degrees and run a colder plug to make it most effective.
this is how it works on a 4 stroke v-8 anyway.

one thing taht got me wondering....aren't there some weedeater out right now that are 2 strokes with f.i. ?
if there is, one of those set ups would be the way to go.
if there are f.i. weedeaters, i can imagine that they are probably mechanical f.i. and don't need a computer. but the injector size may be too small, and they may not give enough fuel to an 80 c.c. motor. most weedeaters are 30-35 c.c.'s and running too small of an injector would make the motor run too lean.
just a thought.
 
I already have experience with electric lawn mowers, weed eaters, and leaf blowers. In my opinion they are not worth the price of the cardboard box they were packaged in.
The electric motors burn out way too easily.
The batteries loose capacity with each re-charge.
The better ones are heavier than their gas counterparts.
The cost of replacement batteries makes them a disposable commodity.
With the price, you are better off buying a new one rather than buying new batteries.
The "plug in the wall" corded ones are a pain to use.
While I have never accidentally mowed over the extension cord, I have had a few close calls.
Alot of folks are not as lucky, and many an extension cord has been chopped up.
I have never had a gas leaf blower catch fire while in use. I did have an electric one that did though.

And all of this is just my experience with the "new wave of outdoor technology".

Does anyone here have better experiences?
 
well if it was set up to run in closed loop, the computer would make NO adjustments to the fuel injection. closed loop is a fixed setting. when it is in open loop, that's when it (and you) will make adjustments to the fuel curve. for example, when you first start your car on a cold morning the computer runs in open loop so that it can get the air temp, exhaust temp and all that, to adjust the fuel curve to make the engine run right......

You've got it right, but reversed. In closed loop operation, the ECM takes input from all the sensors to fine tune the A/F ratio. Open loop operation is when your engine runs at pre-set parameters until the O2 sensors come up to temp, and the engine is warmed up.

But even in closed loop operation, an EFI setup is designed and optimized for a particular engine and can only "self adjust" within a certain range. So yes, you can make changes to the intake and exhaust on a car and the ECM will adjust. But if you make radical changes, you'll just set off the MIL (check engine light) when the ECM cannot compensate enough for the changes you've made. This is where the custom ECM's can let you tune outside the OEM parameters.

I already have experience with electric lawn mowers, weed eaters, and leaf blowers. In my opinion they are not worth the price of the cardboard box they were packaged in....

Amen brother!

Electric lawn equipment sucks. Overpriced, underpowered, short lived.

How many 10+ year old cordless electric mowers do you see out there.................
 
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