Crazy idea from an electric boater... Fuel Injection?

[BACKEMF]

Hi there,

I'm only into electric rc boats but, I just had a thought. Has there ever been a fuel injection system for a gas or nitro engine or am I just a complete putz when it comes to fuel power.

It seems like a neat idea but, is it even possible on the small scale? Would it bring fuel engines to a higher level or am i just blowing smoke out my tailpipe?

Just curious???

 

[Tim_Duggan]

The problem is it's very difficult mapping with high performance two stroke engines using tuned pipe systems. Even in the heyday of 500cc GP bikes where the teams had mega dollars invested, they preferred carbs even though fuel injection was around. 4 strokes however are a very different story.

OS already make an injected 2 stroke aero engine but it uses a plain old fashioned muffler and low rpm.

 

[lohring]

We actually use mechanical fuel injection systems. In nitro (and a few gas) engines, the pipe pressure provides a fuel flow that's relatively proportional to the engines fuel demand. That, combined with various variable flow restriction valves in the carb, gives reasonable control, especially with nitro and alcohol fuels. It's tougher with gasoline because the fuel flow is much less at the same power level. The Walbro and similar pumper carbs are carefully designed to meter the fuel with venturi pressure and pump frequency (rpm) as inputs. These methods are a lot harder to adjust over a wide range, but are inexpensive and very well developed.

Finding a micro processor and very small injector that will work at the high frequency needed by our engines at a reasonable cost isn't easy. I'm sure lawn equipment engine manufacturers are working hard on the issue. In Europe, 50 cc scooters are using the Orbital fuel injection system. The big advantage is lower emissions, not more power. OS has built several nitro engines with simple electronic injection systems. I think the YS mechanical pressure system offers the same advantages at lower cost. These engines are relatively low rpm as well as four stroke which has half the injection events compared to our engines. I think cost will keep electronic fuel injection from being practical in small racing engines for some time.

Lohring Miller

 

[wayne middlemiss]

also if you refer to the range of 2 stroke outboard engines omc etc seadoo all those variants use mechanical injection / electronic .

for me i still prefered carby when i purchased 2 new 115 hp johnsons for my powercat based on economics of greater cost to buy and factor in the running cost economics fuel volumes per hour running time for the extra dollars and my answer to it was im better off with carby engines.

light weight , same power , less cost on purchase.

for the benifits of a little bit of extra fuel burnt.

 

[dwilfong]

Greg would you mind sharing some of what you have done so far?

 

[John Finch]

When I ran nitro engines for record trials a couple of decades ago there were some guys locally experimenting with this but could not keep the engines together. My view back then was.......I can barely keep the engines from blowing apart as it is, so why try to get more power. Using the tuned pipe we could get three stages on the pipe with the proper tuning of both the boat, pipe, and engine. We could certainly push the engines past their breaking point without any added help.

 

[Joe Warren]

One of the only 2 stroke Motor infested hobbies that we have a fixed orfice size for a carb w/venturi ........ and we squeeze the fuel off via 3rd channel lean till it Screams or Blows... or Both..... Even if we did read ex temps & know a idea number for correct Air/fuel mixture? Most would ingnore it for more speed...

 

[lohring]

Power isn't the main goal with electronic engine management. Its getting less expensive to make very complex electronic systems than precision mechanical systems. It was pointed out to me that the cost to produce an NC machine tool is less than the cost of old time mechanical machines when their cost is adjusted for inflation. My Subaru BRZ can get almost 36 mpg in highway driving and still have more power than I need. The vengine might last over 200,000 miles as well. The big outboards are just beginning to develop electronic engine management for two strokes. They can adjust not only fuel and ignition, but also oil and pipe length. It turns out that an oil injected two stroke can use less oil than a four stroke with a pressure lubrication system.

I think electronic engine management in our engines could make them easier to operate. Years ago I tried an exhaust gas temperature sensor that adjusted the needle. The idea was to prevent lean runs and set the needle right every time. I didn't have much luck with it and sold the system to Skip Wagner (of K& B) . Modern electronics could measure a lot more variables. The problem is the amount of development required. Our tiny market won't support that.

Lohring Miller

 

[John Finch]

That says it all Joe. I don't use the third channel fuel injector because I can't keep from leaning it out. No self control when it comes to speed. Got to see if it will take one more click!

 

[Joe Warren]

That says it all Joe. I don't use the third channel fuel injector because I can't keep from leaning it out. No self control when it comes to speed. Got to see if it will take one more click!

Also know as GREED!!!!!

 

[Joe Warren]

Seems we have most of the componets to make a Electronic fuel management system. . You will have to have a exhaust temp probe (Pyrometer).. it could trip a circuit to a servo to move till it reaches a desired seting or a manual stop. You could throw in rich and the Servo would move to a leaner location till it finds a desired exhaust temp. It would not have to be a close circuit. a servo hooked to a bob violet a exhaust pyrometer & a small circuit board could do the trick..... it would be nice if it could richen and lean the bob violet to maintain the desired exhaust temp......

 

[Duke Mordja]

If I remember right, there was a thread on IW that did that exact thing, but with head temperature that controlled a needle valve for water flow. Should be pretty much the same??

Very good idea.

 

[Jim Caldwell]

The head temp will be WAY too slow, been there done that and have the blown motors to prove it,EGT works very well HP gas motors.

 

[Duke Mordja]

The head temp will be WAY too slow, been there done that and have the blown motors to prove it,EGT works very well HP gas motors.

I agree that you would not want to control a fuel setting based on the head temp.

 

[dwilfong]

I built a water control system using the head temp and tested it. This was the first experiment on my list.

Got side tracked and set it all aside for a little.

Working on a carb to use with this set up to control the needle with a ex thermal coupler.

I now Tim was messing with the Nano and I have one also.

But learning and applying the code is a pain and don't have time to do it right now.

working on a flow bench about half way done and a Dino to run every thing on to tune it.

If there was only more time but that working for a living thing keeps getting in the way.

That and racing every month in are district in the high points series fills up my time.

You need the testing equipment to run the eng on a stand to get it going. On water testing takes to much time.

It can be done and work I am sure. But it takes time to do it. Really dose not involve much money if you don't count your time.

Pooling resource's is the best way to do it but most are very hush hush about what thy are doing.

My self I throw it out there for all to see.

"It's just a toy boat."

 

[lohring]

I've been following experiments by two stroke motorcycle engine builders for years. They're trying to use the Megasquirt throttle body injection as well as more sophisticated direct injection systems with ignition timing. Their problems are harder than ours because of the wide range road engines run. but the difficulties still apply. At the least you need to measure intake air flow (throttle position may be good enough) rpm, and exhaust gas temperature. It takes a lot of testing to build a map and a wide band O2 sensor really helps. Two stroke oil is hard on these sensors, though. Below is one quote on exhaust gas temperature that gives a small idea of the problems. We take for granted all the complicated things our simple mechanical carbs do, even if they're not perfect.

"But egt "normal" operation is overidden as soon as deto creates radicals in the combustion process, so it cant be used as a reliable input, to modify fuelling away from the tabled values.

This effect I saw in a PhD thesis I supervised, using the colour spectrum of combustion, via a piezo implanted in the chamber, to control efi.

All was fine, and worked perfectly, with a direct linear relationship, between the intensity difference of two ( infrared ) colour frequencies, and the resultant A/F ratio.

As soon as abnormal combustion occurred the algorithm used to predict A/F ratio was no longer true, and the efi would create spurious results.

Thus a combination of egt, deto, and head temp would appear to be the only way for reliable closed loop control without mass air flow as part of the input."

Lohring Miller

 

[dwilfong]

Lohring that is some great info.

As you said are boats don't run much of a spread in RPM. Thy don't have to run threw the gears to race.

Head temp controlled by the valve I designed would help keep the chamber at the proper temp taking one thing out of the equation. keeping the water temp control separate from the fuel mapping I think would simplify the equation.

Throttle position can be picked up off the servo. not sure if this would be needed till it is run on the bench to see what the ex temps do. Nitro in are small eng will react diffrent than larger gas eng.

The first step is to use a carb and 3rd channel needle to get the feel for every thing.

Gathering data is the first step. With out this it is a shot in the dark.

This is my game plan for future testing.

 

[Tim_Duggan]

Lohring that is some great info.

As you said are boats don't run much of a spread in RPM. Thy don't have to run threw the gears to race.

Head temp controlled by the valve I designed would help keep the chamber at the proper temp taking one thing out of the equation. keeping the water temp control separate from the fuel mapping I think would simplify the equation.

Throttle position can be picked up off the servo. not sure if this would be needed till it is run on the bench to see what the ex temps do. Nitro in are small eng will react diffrent than larger gas eng.

The first step is to use a carb and 3rd channel needle to get the feel for every thing.

Gathering data is the first step. With out this it is a shot in the dark.

This is my game plan for future testing.

This is the beauty of the arduino type boards. It supports multiple PWM inputs and can drive multiple outputs with PWM at the same time. Guess what our receivers talk to our servo's with? So essentially the throttle servo signal from the receiver is our TPS. (Throttle position sensor). The very same board can drive servo's also, so no need for extra circuits. Inputs other than PWM can be used as references also, so using a K type thermocouple for example for EGT or a thermistor for head temps are also useable.

Some of the arduino type boards popping up on kickstarter lately have some serious potential for us. Bluetooth RX and TX modules built in so no need for cable interface for loading code or retrieving logging data, and the size of a thumbnail for the whole controller. Can access them from a bluetooth cellphone without disturbing radio boxlids etc.

Will run happily off our RX pack voltages and are low current draw too.

As Dave has said, the problem is the time involved in logging the relevant data, writing the code, and then refining it. I got a little side tracked with this stuff and since moving house I haven't dug the stuff out of boxes.

 

[dwilfong]

Lohring that is some great info.

As you said are boats don't run much of a spread in RPM. Thy don't have to run threw the gears to race.

Head temp controlled by the valve I designed would help keep the chamber at the proper temp taking one thing out of the equation. keeping the water temp control separate from the fuel mapping I think would simplify the equation.

Throttle position can be picked up off the servo. not sure if this would be needed till it is run on the bench to see what the ex temps do. Nitro in are small eng will react diffrent than larger gas eng.

The first step is to use a carb and 3rd channel needle to get the feel for every thing.

Gathering data is the first step. With out this it is a shot in the dark.

This is my game plan for future testing.

This is the beauty of the arduino type boards. It supports multiple PWM inputs and can drive multiple outputs with PWM at the same time. Guess what our receivers talk to our servo's with? So essentially the throttle servo signal from the receiver is our TPS. (Throttle position sensor). The very same board can drive servo's also, so no need for extra circuits. Inputs other than PWM can be used as references also, so using a K type thermocouple for example for EGT or a thermistor for head temps are also useable.

Some of the arduino type boards popping up on kickstarter lately have some serious potential for us. Bluetooth RX and TX modules built in so no need for cable interface for loading code or retrieving logging data, and the size of a thumbnail for the whole controller. Can access them from a bluetooth cellphone without disturbing radio boxlids etc.

Will run happily off our RX pack voltages and are low current draw too.

As Dave has said, the problem is the time involved in logging the relevant data, writing the code, and then refining it. I got a little side tracked with this stuff and since moving house I haven't dug the stuff out of boxes.

I saw that board on kikstart it is the bomb. some one can wright the program and send it in a e-Mail and you can load it in the boat. also some one can see what your boat is doing over the phone as it is running.

the possibility's are end less with this setup.

 

[lohring]

I think the possibilities are great. I think the benefit will be an easier to run glow engine, not a more powerful one. As an aside, a friend of mine said that modern engine management systems on two stroke outboards rely mostly on fuel metering with ignition timing and not throttle opening to regulate power output. That means that engines can idle , though poorly, with wide open throttle bodies. That allows him to find a broken reed by sticking his hand into the intakes to feel which reed assembly has backflow from the broken reed.

I will be very interested in hearing how experiments with Arduino boards go. There is a lot of information on servo positioning with them. Collecting input data and outputting throttle and needle position should be straightforward. Finding the correct relationships will be the hard part. Trying with real engines, probably on a brake dyno, is the only way to find the answers.

Lohring Miller