After the last part of the week was stolen from me for work and the weekend and Monday fell to a stomach virus, I was definitely ready to cut some metal.

I pulled the fuel tank off the frame and drained it. I’m wondering why I completely filled it way back when. Now I have a really full 5 gallon can full of iffy gas. That’s a lot of mowing.

I first pulled the filler neck off. I found, not entirely to my surprise, that it was held by four sheetmetal screws and “sealed” with what appears to be Bondo.

With the filler neck off, I could photograph inside the tank. It’s not a happy sight. The outside of the bottom is somewhat pitted as well. Since it’s only about 16ga steel, there’s not a lot of material to corrode away. The entire bottom, if not the whole tank, should be replaced.

While I am formulating plan B to replace the bottom plate (or the whole tank), I will continue with plan A.

I marked and cut the hole for the pump and test fit it. I also cut a trial gasket.

I pulled off the old manifold (and, of course, the alternator) from the engine last night and verified some of the fit requirements. While I was in the pulling mood, I also pulled the distributor. There was quite a bit of corrosion around the distributor shaft. I suspect there may have been blasting soda left on the surface that, once it got wet, dissolved the protective coat of oil. In any case, it took substantial effort to pull out the distributor, but there appears to be no permanent damage.

The case stud that the manifold normally mounts to was missing. I recall before discovering that the threads are pretty bad in that case half. I spent a few minutes chasing the threads with a tap and installed a stud which should arguably have been there all along.

I painted the new manifold to match the rest of the engine. Once the EDIS system is in place, I will paint the oil pump block plate and the distributor plug to match.

Speaking of distributor plug, after a brief search, I found an online source [Boost Engineering, since closed] for one, as well as a ready to use trigger wheel/crank pulley.

I have several stock pulleys and a DIY AutoTune trigger wheel.

My plan was to mount the trigger wheel to a stock pulley, with spacers to lift it out from the surface. Since the center hole of the trigger wheel is too small for the head of the bolt and I don’t currently have an appropriate way to enlarge it, I would need to make it removable for access the the crank pulley bolt. Furthermore, I would need to carefully place the wheel very close to the precise angle in relationship with TDC and allow for both radial and angular adjustment of the pickup.

Well, this pulley fixes all those problems at once. It’s not particularly cheap at $135, but it’s a far more elegant solution than what I could make at home. The trigger ring is continuously adjustable, leaving me to be concerned primarily with radial adjustment of the pickup. I’m basically trading dollars for convenience and work time.

Similarly, while I could definitely have someone turn a distributor plug for me or even do my own with my drill press, this one will be here in a couple of days and I’m not sure I could have one made for the same money.

BTW, Boost Engineering [since closed ] also sells complete kits of either MegaJolt ignition only systems or MegaSquirt systems with all the ignition components (no EFI parts). Since I had most of my system components already, I didn’t need the whole shebang, but it’s cool to see someone offering it.

It took most of the day, but I wired the throttle body and reconfigured my original MegaSquirt ECU harness.

For the throttle body, I took the shortest two connectors from Buzz’s old harness and remade them, connecting one injector to each output and running separate power leads. When I originally made the old harness, I was not really aware of the needed seals. It doesn’t do much good to have a weatherproof connector without sealing around the wires. So even though the throttle position sensor (TPS) cable was a suitable length, I needed to cut the pins off anyway, so I rewrapped it in yellow heatshrink while I was at it. Astute observers will see an extra cable in the bundle, the one with the white connector. This is the currently unused factory subthrottle position sensor. It costs nothing to leave it there, just in case someone someday writes subthrottle support into MegaSquirt

On Buzz’s harness, the intake air temp (IAT) wiring was sort of an afterthought, so while the sensor was on the throttle body, it was connected through the frame harness. This time, it’s right there with the other throttle body connectors. Also, the old IAT and coolant temperature (CLT) were wired to the ECU in a 3 pin connector that shared grounds because those sensors both came in from the frame harness. In this case, one is on the TB harness and the other will be on the engine harness, so they will each have a two pin connector.

New to this lineup is the wiring for the idle air control (IAC) stepper motor. This was one of the modifications needed inside the shell, adding four wires. The pins are essentially randomly connected to the motor itself. Unless I was just EXTREMELY lucky, I will need to rearrange the pins before I can expect the motor to work.

While I had the DB37 shell open, I also made the injector leads into single 14ga wires instead of doubled 18ga.

As for the harness, it’s mostly like it was, except nicer. Some groups of wires are bundled together with expandable sleeving and all connectors have been remade with seals. Finally, connectors were added for the options applicable to this job that weren’t on Buzz, like the EDIS ignition system and a permanently connected wideband exhaust oxygen sensor.

In the old system, the wire labeling was very clear until the wires were handled. Wherever possible, I have relabeled the wires using white heatshrink tubing, written on with fine point Sharpie then covered with clear heatshrink. As I re-redo a couple of the connectors, I will relabel the lines I missed.

I have the throttle body adapted to the manifold in what I presume is very nearly final form.

The 95% completed adapter plate is the key to making this very nearly a bolt on conversion.

Sharp observers will see that I drilled the two inside holes incorrectly the first time. I had my template placed wrong. Luckily, there was still plenty of metal to thread into, though running the tap though was tricky. I had to run it forward all the way through and pull the shank of the tap though the back side of the hole. Attempting to turn it out backward made the tap cam into the erroneous hole and jam.

To truly finish the plate, I need to weld on a brace fro the throttle body, media blast the entire assembly and paint it with something fuel-proof, probably epoxy.

As a side note especially for anyone wanting to use this throttle body, get the stock mounting boots and O-rings. In my opinion, scratch fabricating something to fit is just not worth the effort. They are about $20 apiece from Kawasaki [part no 16065-0024]; I paid $20 for the pair on eBay. One online Kawasaki parts house sells the O-ring for $4.71 each, but I found an excellent equivalent O-ring at AutoZone for $0.99 each, FelPro part number 35087. It happens to be for the water outlet for a 91-95 Saturn 1.9L. Beware, however, my AutoZones tend to stock only one per store, so I had to go to two stores.

As for the rest of the intake manifold assembly, I have not placed it on the trike yet, but I have mocked it up in the level mounting position to see what the angle of the all components will be. As luck would have it, the rearward angle of the manifold and the rearward angle of mounting boots are the same, or at least close enough that I can’t tell. It remains to be seen whether I will have the throttle bodies mounted as shown or flipped around so the throttle cable approaches from the front.

A friend emailed me asking for clarification in the “big step” update:

Did you get the stepper motor working correctly? In the vid it went to full open then I wasn’t sure if that was the secondary’s @ 60% or the mains.

I replied:

Yes, working well. At least working as well as I can test with it removed from a running engine.

The video depicts the subthrottle’s opening all the way under MegaSquirt control. This, via the cam, opens the main throttle a bit. MegaSquirt then works it back towards about 60%, by which time the main throttle is closed, as I manually adjust the CLT knob on the stimulator. CLT is megaspeak for coolant temperature, intended to represent the running temperature of the engine.

The engine would (likely) not warm from freezing to 160F in 15 seconds, so the throttle would close in many smaller steps instead of the 3 or 4 big jumps shown here as I manually turn the CLT knob on the stimulator. Also, the actual throttle opening needed for warmup will probably be less than the full amount provided by the subthrottle cam. I wont know that for sure until it’s on the engine and the engine is running

Perhaps obviously, neither Buzz nor the VW have “coolant”, at least not a self-contained recirculating coolant. Sometimes people use oil temp for this, but the engine is usually well into operating temperature before the oil gets very warm. Cylinder head temperature is a better representation of CLT on aircooled engines. On Buzz, I JB Weld’d the CLT sensor between some cooling fins cylinder #2.

I was lucky that the fins on Buzz’s head were spaced similarly to the size of the default MegaSquirt CLT sensor. What’s more appropriate, especially for a VW, is something more like this cylinder head temperature sender which goes under the spark plug like a washer. Trouble is that this is a thermocouple, which produces a small voltage based on temperature. MegaSquirt wants a thermistor, which varies resistance according to temperature.

I may hack an IAT (intake air temp) sensor, which is electrically the same at the CLT, and see if I can get it crammed between some fins.

Another complication with the VW is that you not only have to deal with the cooling tins, but what they represent: cooling air forced over the cylinder head, cooling the fins while you’re trying to read their temperature.

Many months of sporadic research have not revealed a published flow rate for the injectors on my TB. I have am considering sending them to Witchunter Performance for cleaning (probably unnecessary) and more importantly, flow testing.

Sadly, it will run about $50 to clean and flowtest two injectors (or $30 for flowtest only) and return ship them, but that may turn out to be an investment in time and/or sanity saved.

I could save the money by robbing two injectors from Buzz’s old throttle body. They are known to be 245cc/min injectors. Preliminary experiments with settings on MegaSquirt, however, indicate a pretty low idle pulsewidth, just under 2 mS. Maybe I have something set wrong, but that’s not much margin below the recommended minimum of 1.7 mS.