Fuel injection

[moonbeamerll]

"If we were being rational we wouldn't be riding old motorbikes" Say it again!

[Garnet]

Seeing as many of us are prepared to fit different carbs and silencers to our bikes which involves much the same effort, I'm not sure that's a deterrent.

It's not the physical fitment of the injection that would be all that difficult. It would makeing the bike run afterward that would be the problem. (edit: Stock) Fuel injection is not user adjustable for mixture like a carb is.

You would never take a set of carbs off a 900 Duc and bolt them on to an R90/6 and expect it to run perfectly. You'd get a pocket full of jets and needles and settle into a couple of days of tunning. That is why you need an injection system that has the ability to be adjusted (like the SH) so you can make the bike tractable.

[Major Softie]

You would never take a set of carbs off a 900 Duc and bolt them on to an R90/6 and expect it to run perfectly. You'd get a pocket full of jets and needles and settle into a couple of days of tunning. That is why you need an injection system that has the ability to be adjusted (like the SH) so you can make the bike tractable.

Which CAN be done with the R850 system, but only by adding a Power Commander, which adds $300 -$600 dollars. But that works in conjunction with the FI computer on the bike, so don't forget that expense and mounting problem. Likely, the biggest expense is the one Vanzen is referring to, which is dyno time. Since you would be starting with a complete unknown, that would not be the "tweaking" that is involved when dealing with known bike/injection combos, so it could end up being a pretty big investment, and might make the whole thing approach the cost of the other system we're talking about. It might actually start off fairly close and only take a couple hours, but it's a complete crapshoot - no way to know.

[Rob Frankham]

Twas done on a R80 or a R100 (can't remember which) in a friends workshop... I saw it about 20 years ago... using R850 parts. Don't think they ever got it to run well.

Rob

[Major Softie]

Twas done on a R80 or a R100 (can't remember which) in a friends workshop... I saw it about 20 years ago... using R850 parts. Don't think they ever got it to run well.

Rob

But it was cool, right?

[Garnet]

I don't know how the Power Comander works. Does it give a portal into the control unit so that it can be re-maped or does it plug in between the harnes and the control unit (computer) and just trick the unit by giving different sensor readings to produce more power and throttle response? If it is the later, I'm not sure there will be enough adjustment to trick the system into work on anything as different as an airhead.

[R85/8]

...You would never take a set of carbs off a 900 Duc and bolt them on to an R90/6 and expect it to run perfectly. You'd get a pocket full of jets and needles and settle into a couple of days of tunning. That is why you need an injection system that has the ability to be adjusted (like the SH) so you can make the bike tractable.

That's true. Done that before, took a set of Mikunis off a T500 and improved my R75/5 out of sight.

My understanding is that the fuel injection gets its info from various sensors and operates with a preprogrammed computer ('map') depending on what the sensors tell it.

Chucking a few variable resistors into the line for each sensor would give a similar effect to having different jets. I'm assuming that starting with a system from a similar size engine would at least be close enough for it to run in the first place. A few plug chops and resistor tweaks would give some idea if you're heading in the right direction.

As I understand it a loop system varies the map, and some systems can 'learn'. The computer part of the system seems to be a closed book so that is the hardest part to crack, which is why I think the approach might be to 'fool' it with variable resistors.

I wonder if any of the electronic mags have published a DIY computer for a fuel injection system? At least with one of those there would be access to the software.

This is starting to sound like a winter project

Edit: off to read up on this http://www.megasquirt.info/

[Rob Frankham]

Chucking a few variable resistors into the line for each sensor would give a similar effect to having different jets. I'm assuming that starting with a system from a similar size engine would at least be close enough for it to run in the first place. A few plug chops and resistor tweaks would give some idea if you're heading in the right direction.

Got a nasty suspicion thats not going to work... I think as soon as you switch on, the ECU is going to 'think' Oh sh*t all the sensors are knackered and either do nothing or go into 'limp home' mode.

Besides, you're proposing an analogue solution to what is essentially a digital system. It reads a setting from a memory location dependant on the values received from the various sensors. A simple resistor in line with the sensor might conceivably work for one rev/load/throttle/temperature situation but not for all... or even probably any others. The only way to make the system work with another engine is to remap the memory... essentially overwrite all of the memory locations. On some ECUs this can be done simply by reprogramming the existing memory. On others you need to substitute a pre-programmed chip with the new values installed. Not sure about the 850 setup but I know the early K's needed a new chip.

I'm sure it could be done but whether any gain would be worth the hassle and the cost is a matter for you.

Rob

[the quinner]

Edit: off to read up on this http://www.megasquirt.info/

The "micro" version of MegaSquirt is what you want...MicroSquirt is pre-built in a more compact and fully potted enclosure...intended for motorcycle and powersport use.

There are plenty of other systems that would be very adaptable to an airhead...you can easily spend days reading info on the 'net. Haltech (who did the controller for the Luftmeister kit) is still around...etc. (aside: the Luftmeister "kit" was based on the Haltech F3 controller...you can still get wiring diagrams, the owner's manual and software from their website...you'll need a good DOS computer)

The hardest part of doing an EFI conversion on an airhead USED to be the additional power required. The controller, fuel pump and injectors can easily add 5-8+ amps of draw to the already marginal airhead charging system...Enduralast and Omega have solved that issue.

You can incorporate ignition into the mix (same controller) or treat it as a separate (but, of course related) system.

IF I were doing it...I'd use microsquirt to control both fuel and ignition...I'd incorporate throttle position, air temp, air pressure, cyl head temp. and lambda feedback. I'd use two Bosch ignition control units with built-in dwell triggered by the microsquirt to make a non-total-loss system.

For track use, the MAP sensor could be replaced by a MAF sensor and the O2 sensor feedback eliminated...but, the controller maps would have to be tweaked for ambient conditions for each outing. On a bike that will go up and down relatively big hills (relative to the change in altitude at a race track) and that will be ridden in varying weather, I'd want a MAP and O2.

I have everything but the MicroSquirt controller...and the time

[twist]

where do you guys learn all this stuff from? Gads! I hope this project continues because I really want to follow for curiosity's sake.