PerformanceTrucks.net Forums - Not a truck. Not a GM. Supercharged & Nitrous BMW V8 T-bucket build.

The other DIY part of this build is the engine management, I want to take a minute to talk about my EFI controller of choice..and the history of how how I ended up there.

I've always had a personal interest in tuning, may it be carb & dizzy tuning or HPtuners. So when I started learning the in's & out's of tuning the OBD1 Bosch Motronic M3.3 system on the mid 90's BMW I had no idea what I was getting myself into.

Fished the 27c512 chip out of the BMW ecm, read the chip, saved the 64kb file of binary/hexcode.

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It took a couple years of learning but eventually I was able to identify roughly 60 or 70 control tables of the 130 some odd maps hidden in the code. But alot of tables & controls were unknown and unidentifiable.

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Last January I took the car to the Roadkill Zip-Tie drags in Tucson, had a ton of fun and met a ton of great people.

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But the car was slooow, like high 14's low 15's, when I got home I decided to convert the original Motronic EFI over to a standalone EFI that I would have full control over without any unknown variables.

I was looking at Megasquirt, too expensive. Haltech, way to expensive. EcuMasters, also waaay too expensive... then I stumble upon a budget, open source, D-I-Y fuel injection controller called Speeduino. It uses a readily available Arduino Mega2560. I believe the entire project was started simply because one dude in Australia wanted to see if he could run his 4cyl Miata off of an Arduino. It worked, not only worked but the system took off and others began to follow suit. Speeduino uses TunerStudioMS software (Megasquirt) but on it's own firmware so it doesn't share the same control tables as MS. Did I mention it's super budget friendly, I was able to get an Arduino Mega2560 and assembled Speeduino board for sub-$200U.S.

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The onboard MAP sensor is good up to 21psi of boost, it has 4 injector driver channels out and 4 5v ignition logic level out so it does need external coil drivers. In order to run a V8 the injectors are wired in pairs for semi-batch fire and ignition is run in waste spark.

Taking a look at my 4.4L short block before I bolted the heads on we see that (bank 1 left - cyls 1-4 / bank 2 right - cyls 5-8) the paired cylinders are 1 & 6, 2 & 8, 3 & 5, 4 & 7. While one cylinder is coming up on it's compression stroke the other is coming up on it's exhaust stroke. Having the spark plug fire every rotation simply means it'll spark while the exhaust valve is open and spent exhaust gases are leaving the cylinder, thus a wasted spark,

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Speeduino fires it's 4 channels consecutively so it's up to the installer to match it to firing order. Firing order on this engine is 1-5-4-8-6-3-7-2 so Channel 1 = Cyls 1 & 6, Channel 2 = Cyls 3 & 5, Channel 3 = Cyls 4 & 7 Chanel 4 = Cyls 2 & 8. Injectors are wired the same way.

On the mid 90's BMW I changed the "dummy" coil on plug ignition over to two waste spark 4 cyl coils driven by an MSD DIS-4 ignition box. The Speeduino triggers the MSD box.

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Speeduino runs in Speed Density (RPM vs MAP), or Alpha-N (RPM vs TPS) or Imap/Emap...which monitors both intake manifold pressure and exhaust pressure and calculates load based on the pressure differences between intake and exhaust. I use Speed Density but want to experiment with Imap/Emap in the future.

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Video of first fire up and test drive after install:

In the video you can also get a sense of the BMW V8's singing voice, to my ears it's a bit like a modular era mustang.

The system self tunes it's VE table based on wideband O2 input and has plenty of accessories & outputs like boost control, E-fan, 2step rev, 2 stage nitrous controls, flexfuel sensor & injector add tables for alcohol, variable valve solenoid controls...the list keeps going.

On my T-bucket project I am definitely sticking with the Speeduino but will maintain the coil on plug with two MSD dis-4 boxes to keep clutter & wiring down in the open engine compartment.
This is why it was important to me to use the early 4.0L OBD1 timing covers and front mount crank trigger, because I already knew how to wire up the variable resistance crank sensor and tune the Speeduino to run on that trigger & set up.