The great big Electronic Fuel Injection thread!


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Quite interesting. I'm wondering what means of adjustment they are using for the flex fuel detection. Either they have a sensor in the fuel line like passenger vehicles or they gave the EFI a lot of authority for making adjustments based on exhaust oxygen feedback. Delphi designed the EFI, so I wouldn't be surprised if they used one of their own fuel sensors.

Not that I want ethanol to catch on as a regular car fuel, but I do wish there was a station closer than 80mi.
Micro-technology with EFI gadgets could become an entirely new field for small engines. Tiny fuel injectors and feedback systems running on little more than just a few milli-amps.

RISC processors are used most often in engine controllers. You geeks might like Home - MIPS Technologies -MIPS Everywhere - MIPS Technologies to check out some cool engine controller stuff. Nothing there is small and cheap. In principle, an EFI system that's equivalent to a pocket calculator with capability and power draw looks very attractive, feasible, and cheap. Carbs are simple but just to a point.

A 16x16 fuel map, timing control, and DBW would be just toooooo cool as a bolt on upgrade!!!
I didn’t see this thread until I was just reading over one I started on "projects" section.

I was over reading your guys thoughts about EFI stuff, I wanted share some of my thoughts to. ( Sorry if this might seem long, I think its great information for topic )

On side note I just bought :weld::weld::weld:

SO haha! , this site will be my EFI project site, anyways...

The system I am designing is simple (so I like think). I would control both fuel and spark. Purpose behind controlling spark, was for fact I can slap a Ford EDIS unit on any motor and get a clean tach single back off of it, plus I can control timing advance/retard by yet another pulse back into the module.
This is optional to do, I wont get into this sense we are talking about just EFI.

What I want share light on is how the Fuel Injection would be working and exactly what hardware I am using.


Fuel Pump/Injectors/Regulator: GO look on ebay for any EFI'ed motorcycle, 1000CC bikes seem have EFI on them, I got my parts off a VR4? Honda something, for 20 bucks I got fuel pump, 4 injectors, fuel rail, fuel regulator. Now you cant beat that!, do math each 4 injectors in a 1000cc 4 piston engine, each injector can run a 250cc size motor no problem, and up to whatever god 10,000++ RPM. And fuel pump draws around ~3 amps? at 30psi...(note the injectors are TINY, great for mounting)

Air Meter: Ford Escort 1.9L (90~95) Mass Air Flow meter. These units come in there own housing, you can unscrew the two screws and take the meter off the housing, Its a 2-wire meter, if you look closely there is a little smaller metal tube the wires plug into besides the main opening on the housing, on my motor I machined my own 1" di housing and made a little 3/8's tube similar to one on real deal. I tested it, works great! on my 6.5 clone I get .8 volts at idle and 2.5 at wide open, what all that means? nothing just gives me analog voltage for measuring the engine load, of course when boosting I still have another 2.5 volts of air flow to go! :smile:

Temp sensors: anything can work here, coolant sensors, air temp sensors, as long as my computer can figure out hot between cold, thats the real main thing. They call this "Enrichments"

Throttle Position Sensor: Optional in my opinion, I don’t think these motors would need this, just richen the mixture a little and any tip-in throttle movements, motor wont lean out, yet you may still need one ...

Oxygen Sensor (O2): Optional, I doubt any O2 sensor could read gas correctly sense you are measuring just one piston, and at lower rpm you might read the atmosphere air outside the pipe and get misleading information.

Exhaust Gas Temp sensor (EGT): This is the way to tune a motor in my little world. You dial your motor to run at a certain temp, plus if you tune it wrong, the temp will be wrong (example run WAY hot). Also different types of fuel will tend to run at different temp's.

That’s it!!! well and fact you need a computer based controller to make it work, I think someone mentioned a analog based EFI controller, GOOD LUCK! BOSCH made one for BMW's and whatever else, monotonic something jet, bunch of transistors and resistors/caps, its not impossible, but I rather "flip bits" then try debug a analog circuit, any day! :hack:

I won’t get into to much detail about how EFI computer could or would work, basically you just have a 2d fuel and or spark map (engine load / engine rpm) and punch numbers in the "map" to tune it. Simple as that, then add your enrichments (throttle position/engine temp).

Agian this is just for information purpose, it sounds great and simple, I guess if I were to do it correctly, make a Clone Bolt on kit perhaps? and package it under 100 bucks ( which was the goal), it might seem attractive, I am leaving out more details about how end user would install/tune it , laptop?, programmer?, pre-programmed?, who knows... And another question might be where get the electrical power to run the system, go Google Li-Po batteries, great source of larger current power for low space/weight applications...

Great information Sean! It would be great to see more pictures of how people mounted the crank sensor, crank trigger wheel, and tps sensor if anyone has used them. I remember seeing some throttle bodies for motorcycles or something a while back that had built in injector bosses. Is this the normal case?
If I was going to use fuel injection on a small engine i would use MegaSquirt
I personly dislike megasquirt because fact (at time I had it) they never could get stable code, plus to many "people" always changing things, Plus its a little over kill for such a simple application...

And last, its no fun to "buy" already built hardware when its 100x times better to build it your self! :hammer:
Its not really that much over kill using MicroSquirt to run a small engine especially if you wanted to control the Ignition as well (no more stepped keys for advancing the timing), It also makes it a lot easier to tune the motor with there tuning program on a laptop after the system is installed.


Well-Known Member
The MS code still seems to change frequently, but most of the development effort appears to be going into the MS-II Extra code now that MSnS-E has been stable for quite a while. I expect official support to eventually dry up for the MS-I processor.

One big detriment(IMO) to MicroSquirt is that it has no onboard MAP sensor. That means using either an a GM style external MAP(which is ~$60-80 and almost as big as the whole Microsquirt) or rigging up your own pressure transducer with a similar transfer function as the supported sensors. I have two 400kPa MAP upgrades from DIYAutotune and the sensors are only ~.290" square.

On a side note, around Monday I'll post some photos of the EFI stuff I have. This afternoon I'm leaving foe the weekend and probably won't have time.
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No, none of the units with surface mount components(pcb v3.57 and Microsquirt) are available as a kits. I wish they were, though, even if smd parts are a PITA.
Your right Stang it is expensive, there was another guy MiniMs Website that made a smaller board for the Meagsquirt the circuit board was 3.4" x 5.2".
I've got a copy of the board design if anyone wants a copy (you were able to download it from the website)


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Cool. Is there somewhere you could host it in a zip file or do you prefer email? is a decent file hosting site.

I would probably ghetto fab my own with the "laser printer" pcb mask method. I wouldn't mind finding pcb files for the official MS boards too, but I think I would have to make my own since those boards are still in production.

My first "Production" printed circuit board I designed few years back was a copy of MS1 v2.2 board, but redeisgned for my PIC 877a chip, all the parts that are on the board layout are identical to the BOM from MS1, its more enough to drive a single piston motor IMO, still have TPS,O2,CLT,MAF/MAP inputs onboard. board is 3x2.5" and have enough extra space for addtional junk :weld:

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How nice, I've long since played with the idea of doing a very basic EFI using an arduino microcontroller. I'm already using it in a little hybrid project I'll be posting soon.

For the record, the analog system was called Bosch L-jetronic. Late model air-cooled volkswagens used them. They use a stupid vane thing that meters the incoming air, taking that out of its tube and modifying it might be able to trick it into working in a small system but how low it can go is questionable. i would not doubt if you have a knowledge of analog circuts and plenty of time to reverse engineer it, you could make it operate on whatever range you want.

It's been brought up before, injectors. 14# are huge. All of the EFI motorcycles I've looked at also have huge injectors as well. Does anybody happen to have any flow analysis data with injectors at very very short pulsewidths?