Originally Posted by Low_Cal

I assume this is throttle body fuel injection. Anyone know what sensors are used? Do these things typically have a MAF (Mass Airflow Sensor?) Thinking about building my own.

normally, yes. at least on a fourstroke.

AFAIK throttle position, manifold air pressure, temp ( head or exhaust), crank position, knock and mass airflow are the basic sensors needed for a simple FI setup.

A good place to start looking at DIY FI is the Megasquirt forms. or more specifically the Microsquirt.

I would think the biggest problem you will have is finding a low weight cost effective fuel pump and a way of regulating the fuel pressure.

Also a maf is most likely not necessarily required as a map sensor would do and a knock sensor is not required if the system is not controlling the cdi/ignition and even if it is its still something you could do without on a simple setup. O2 sensors also are not required, just refinements.

I would imagine off the top of my head a tdc, throttle position, map, intake air temp, engine temp would prob be enough to get a nice running motor but only if you can get a constant regulated fuel pressure linked to intake manifold pressure of course.

How does the still saw do it?, what pressure does it run on, I would imagine a bar of pressure would be required at least for a crude system and 3 bar for a more refined system. if I was thinking of doing this to one of my engines (im not) thats where I would look for inspiration.

The concept is good -price is bad.....
Spoke with the company that makes the EFI - it is aimed at the UAV market, not the hobbiest,
If you have $18k to spend ? go for it .....as that was the price that was quoted to me

sooner or later it will boil down .. when we see chain saw's weed wakers lawn mower's we are next in line for affordable injection systems

I'll keep my walbro, thanks.

I bet the small carburetor suppliers are developing FI as we type. They want to stay in business.

FI on small engines is extremely overrated IMO. The 4 stroke dirt bike market started going to FI in 2009 and it's not all it's cracked up to be. Cost of the bikes went up considerably and there's a whole new batch of expensive tools to buy just to be able to tune (yes, they still require tuning) and troubleshoot the system. I've replaced fuel pumps, fuel injectors, TPS sensors. Lots of electrical gizmos to to die or even worse, not completely die and just cause problems that take forever to find and fix. Give me a carb any day!

On the other hand, the throttle response on the fuel injected bikes is better and they do use less fuel. They are also less sensitive to temp and air pressure changes than a carb'd bike but in the end I don't think the pros balance out the cons. The carbs we use on these planes are extremely simple, relatively inexspensive, cheap to rebuild, and easy to work on. I'm sure the day will come but I think it will be years before someone comes up with an inexspensive, reliable FI system for these engines.

Originally Posted by ForsheeMS

FI on small engines is extremely overrated IMO. The 4 stroke dirt bike market started going to FI in 2009 and it's not all it's cracked up to be. Cost of the bikes went up considerably and there's a whole new batch of expensive tools to buy just to be able to tune (yes, they still require tuning) and troubleshoot the system. I've replaced fuel pumps, fuel injectors, TPS sensors. Lots of electrical gizmos to to die or even worse, not completely die and just cause problems that take forever to find and fix. Give me a carb any day!

On the other hand, the throttle response on the fuel injected bikes is better and they do use less fuel. They are also less sensitive to temp and air pressure changes than a carb'd bike but in the end I don't think the pros balance out the cons. The carbs we use on these planes are extremely simple, relatively inexspensive, cheap to rebuild, and easy to work on. I'm sure the day will come but I think it will be years before someone comes up with an inexspensive, reliable FI system for these engines.

You are most likely right...but who knows??