Welcome back, dear reader. No doubt, you've been on the edge of your seat since my last post where I cryptically told you I had gone green. Well, it's true.You gotta reduce, reuse, recycle. I am reducing my carbon footprint by buying another junkyard engine from little Zachery's 1998 Ford Explorer. You remember little Zachery, Frank and Barb's boy... the one floating through life collecting misdemeanor charges and buying booze for high school kids. After the divorce, when barb took the Eddie Bauer Explorer, Frank was out of a vehicle for a while. Not that it mattered all that much anyway since Frank lived on a boat and didn't have a license because of the DUI. But eventually Frank picked up an XLT trim level Explorer with a big dent in the side. The original owner had put it into the guardrails on an onramp when the right rear firestone tire blew. Frank got a loan at the seedy dealership over off highway 19, and somehow paid it off without a visit from the dealer's in-house repo guy. And when Frank finally had enough credit to get a loan for his yellow convertible Corvette (who cares if you have a comb-over when it's blowing in the wind??) he handed the Explorer over to 19 year old Zachery. Amazingly, Zachery actually kept oil in the engine, but while he was in county for posession of controlled substances the Explorer got towed and eventually ended up being designated abandoned property. Since the interior smelt of cat piss and marijuana smoke it got sent to the wrecking yard. I hate to say it, mister small block Ford, you were probably better off in Zachery's hands.
So with a lead in like that, you'd naturally assume that we're going to talk about how I'm building this engine up for the Falcon. While that's a good guess, you'd be wrong. We're going to talk about Drive By Wire or Electronic Throttle Body systems.
Turn the clock back to 2020. I know that feels like a lifetime away, back before we all had the pleasure of knowing the name of Anthony Fauci, but way back then I had just installed the 5.oh into Grace and got a chance to try out the new intake. I always knew this intake would be overkill. Eight 52mm throttles are absolutely not necessary for a 300-ish HP engine, but we don't always do things because they make sense. After driving it, it was confirmed that the intake was a major mismatch with touchy driving characteristics. I looked at different ways to mechanically tune the progressivity of the accel pedal, but eventually came to the conclusion that conversion to drive by wire was probably the ideal solution. Not only can you control the relationship of accel pedal to throttle opening, this relationship can also be a function of engine speed, allowing you to shape your torque curve at every pedal position. You can also limit throttle opening when over-temp, or on loss of oil pressure, or implement an automatic rev-matching strategy for up- and down-shifts.
Drive by wire on Individual Throttle Body intakes like mine do exist, but they are pretty rare. They tend to fall into one of two camps: either very professional motorsports teams who spend a lot of money or low dollar tinkerers in their sheds. I knew that I was going to have to figure out a lot of this implementation on my own.
Currently Grace's engine control unit is a Megasquirt II. It's pretty flexible and capable, but it's also quite old. Megasquirt does not provide any support for drive by wire. There is a standalone drive by wire controller which can be used with Megasquirt, but it was about $500, and at that price point you are already halfway to a full ECU with DBW support. For a while I messed with making my own arduino powered DBW controller, but it was proving to be a lot of work and outside my pay grade. Somewhere along the line I stumbled across RusEFI, an open source ECU project that supports DBW.
Behold, the Frankenso
"FIRE EXTINGUISHER REQUIRED"
Powered by STM32 Discovery Board
Drive By Wire add-on board
Powered Up
DBW add-on installed, jumper wire spaghetti on the back.
I purchased the Frankenso (Frankenstein in a Denso form factor) back in May 2020. I began playing with it, and making errors right away. It seems I have to learn things the hard way. I fried a Discovery board along the way, as well as several other components in the power supply when I set the exposed circuit board on a metal surface while powered up. I am not a smart man. Thankfully there are generous people in the RusEFI community, and they helped me get it back up and functioning. It took much longer than it should have, but eventually in September 2021 I got a proof of concept up and running using the Frankenso ECU, an LS3 throttle body, and a BRZ accel pedal.
Once I had proved that I could indeed use this ECU drive a throttle body, I started modifying the throttle body housing so that it could be used in my application. To do this, I built a high precision particle board milling machine out of scrap wood and a $25 harbor freight router.
Step 1: stick the throttle body in a vise
Step 2: hack it in half
Enter the high precision milling machine
Step 3: Commence milling process
Step 4: remove a lot of material
Step 5: put it back together. Now you have a geared DC motor with redundant position sensors and a 10mm output shaft.
After I finished this modification I was quite pleased with myself. So pleased in fact that I did almost nothing on the project for months. In the meantime, I got a 3d printer and started to realize all the use cases. Most of the time I won't use it for a finished product, but as a rapid prototyping machine, it works quite well. I needed to make an adapter plate to mount this motor to the intake. I was sure that if I just tried to measure drill mounting holes, it would not fit well. At some point I realized I could have parts laser cut, but first I needed to validate my design. It became an iterative process: I measured the best I could, designed it in CAD, printed it in plastic, checked the fit, and went back to CAD.
Plastic Prototyping
CAD screenshot of the motor bracket
Eventually, I got something I was reasonably confident in and sent it to SendCutSend for production. This is a company that will take your CAD files, provide an instant online quote, produce and send parts to you, all for a reasonable price. I had four moderately complex parts cut out of aluminum all for $30. On top of that, they included a little pack of Sour Patch kids. That's what you call 5 star service.
Next I welded this bracket up, tapped a few holes, and put it together. It was looking absolutely mint, other than a few boogery welds. If there's one thing I've learned as a dad, it's that you can't be too afraid of a few boogers. Turds on the loose, now that's a different story (for a different time).
The lower bearing support was a 7 dollar robotics part.
The good welds which will of course, be on the underside of the bracket
Top side boogers
ETB motor in place
The test rig
Getting the throttle motor to actuate the throttle valves took a bit of monkeying around in the ECU settings but eventually I got it. I produced a proof of concept for a drive by wire ITB intake, and it only took like a year and a half! The throttle return springs are a bit strong for the motor, so it can only get to about 70% open. This should be remedied by reducing the preload on the springs, which I'll be testing shortly. I'll keep chipping away at this project an hour or two a night, a couple times a week, and dear reader, you can come along for the ride.
UPDATE: I made a short video to clarify exactly how this setup works. Maybe it will be of value to you.
