View Full Version : Mega-Squirt EFI (for A series engines?)

03-23-2010, 06:34 PM
Here is a note that I got from a buddy who has converted his early 70s BMW 2002 to Meqasquirt electronic fuel injection. The key item of interest for us folks with the A series engines with the siamesed intake ports is his observation that the new version looks like it'll work with our cylinder heads.

We have a '73 BMW 2002 with dual sidedraft Mikuni's that might be easier to convert to EFI than tune (when it comes home the highschool body shop in a year) and he and I have chatted and done some reading on various web-sites about going to EFI on a Bugeye (using either the SUs or a Weber DCOE as the throttle body), but that'll be a few years away as well. There's also a chap who builds machined aluminum EFI injectors that replace the tops of the larger SU carbs, but doesn't have anything for the smaller SUs that we use. Can't find his web-site at the moment, but his primary emphasis is on Triumphs, mostly the TR6 if memory serves.

Any uber-geeks out there that are wealthy and would care to do all the development work for the good of LBCs?



Hey guys, Finally It appears MegaSquirt V3 is out. Its a daughterboard upgrade, so I'll likely be applying it to my 2002, although it looks like the case is larger then my msII case.


Features include (with my notes)

(Based on full featured MS3+MS3X+V3.57)
Speed-density, alpha-n or MAF for fuelling calculations

16x16 fuel tables in 0.1% steps with true interpolation and movable rows/columns
16x16 spark tables in 0.1 degree steps with true interpolation and movable rows/columns
---> This is great, as you can get better tuning with higer resolutions

Wall-wetting transient fuel control for better driveability

---> also brilliant, there was initally some code added to do this (x-tau). It actually adjusts for fuel sitting on the walls of the intake.

On board datalogging to SDcard (max 333Hz sample rate)
Tuning by serial or built-in USB-serial port.

8 channels sequential fuel (hi-z injectors or low-z with external resistors)

--> Probably the most important innovation yet. Having full sequential injection means you could tune for each cylinder. Not a huge deal on our 2002s, but on some strange british non-cross flow heads (like what the minis have) this is a big deal. Also nice for race cars where you can put the injectors far away from the throttle plate for better atomization.

2 additional fuel channels (hi-z or low-z)
8 channels sequential spark (logic level output)

--> This is cool. Must mean that you can do Coil on plug rather easily.

6 channels mid current output for small solenoids or relays
2 'spare' conditioned 0-5V analogue inputs (+2 more raw)
Two wideband oxygen sensor input (external controller required)
(Up to eight widebands supported via external data capture)
GM-style stepper idle control
2 and 3 wire PWM idle control

Closed loop idle control
Closed loop mixture control - ideally with wideband
Closed loop boost control

--> All three are brilliant, and I'm looking forward to the closed loop mixture control the most.

Various boost control systems (gear, time, speed based)
Two stage variable nitrous control

2 step type launch control

--> Launch control might be nice for standing start races?

CAN communications to interconnect other Megasquirt products e.g.
transmission controller
Supports external data capture boards (e.g. for external EGT boards)
EGT data support (with external amplifier)
Staged injection
Dual fuel (e.g. LPG)
Table switching, (mainly for dual fuel use)
Water/Meth injection

Individual cylinder injector trim

--> This is kind of a big deal, mainly for
racing or siamese port engines (hint doug). I was thinking for racing sometimes you get a slightly lean or rich cylinder due to underhood conditions (like how #4 sometimes will be different because its in the back with no flow around the head to cool things)

Injector phase timing
Individual cylinder spark trim
Support for numerous OEM trigger wheel patterns.
Magnetic (VR), Hall, Opto crank sensor input
Magnetic (VR), Hall, Opto cam sensor input

I'm really kind of excited over this, it seems MS has matured quite a bit.

03-23-2010, 06:42 PM
Found the web-site for the aforementioned TR6 gearhead making EFI adapters for SU and Stromberg carbs:


03-23-2010, 08:00 PM
I would think that the simplest method would be to use motorbike throttle bodies. If a pair of TB's will support 180+ HP on a Ducati they would do the same in one of our engines. There are a number of folks in the UK running Suzuki Hayabusa TB's also, even GSXR600's have been used with success. If you buy a set of 4 off a wrecked bike you can use the two outer ones and they already have TPS installed on the throttle shaft. Depending upon the chosen manifold you may not even have to alter the spacing.

I currently am running Megajolt and plan to go with the MegaSquirt system in the future for the drivability and tuneability.

03-23-2010, 09:51 PM
Interestingly I was at a motorcycle shop today and the very first thing the guy said when he saw the carb was that I needed to get a Motorcycle Fuel Injection and do away with the carb. If I understood him correctly, he was talking about the merit of getting it from an older bike where the system was both more forgiving, simpler and self tuning. At that precise moment another employee started talking about his bike which he is converting to Megasquirt. I don't understand any of it but it sure sounds interesting.

A couple of years ago Practical Classics had two articles on FI for A series engines - I'm pretty sure I scanned them though I might have to dig out an old hard drive if anyone is interested.

03-23-2010, 10:56 PM
I'd be interested in the articles!

Here's a couple of web-sites that I got lost on, trying to do a bit of reading on A series EFI:


03-23-2010, 11:12 PM
You know a lot of people talk about all the supposed problems due to the siamesed ports on the A-series, but they seem to do pretty good with decent carbs. No reason that they should not do just as good if not better with FI. Sure it's not ideal, but it ain't a showstopper either. If a V8 can get away with an O2 sensor in each collector to read 4 cylinders with a Carb style throttle body and shared port intake runners why can't an A-series?

03-24-2010, 09:02 AM
An A-series *should* work fine with throttle body style injection IF you have stock manifold with the balance tube AND you set your injectors to fire 4 times per cycle.

Doug would like to inject using his DCOE. The manifold has no balance tube, so the likely hood of one cylinder running rich the other lean is greater.

Sequential injection would be essential for any port injection set up and would be very helpful for the set up Doug would like to create.

Doug, I am an uber-geek, but far from wealthy. I have a stock 1275 manifold and carb set sitting on my work bench. If you wanted to go stock with your carbs, I could develop the fuel injection adapters for you if you were willing to pitch in for materials and supplies.