Microsquirt Mexican EFI on my 1915cc

[jimmyhoffa]

It's been a while, but there's only one place to go when it's homebrew Aircooled EFI time, and that's right here.

I have a 1974 Chenowth 2RL which I have taken to driving to work, and the carb life is getting old. Here is the subject of this academic pursuit:




First off, I ended up trading another member on here some 40x35 heads straight up for most of the Mexi EFI setup, which was great for the both of us considering our power targets and current build needs. So the parts collection begins!

-Mexi EFI throttle body, center intake section, end castings, and fuel delivery
-Microsquirt with latest firmware
-Mario's external crank trigger
-Mario's IGN-4VW coil with built in drivers to play nice with MicroSquirt
-Mario's GM calibration IAT
-Mario's rough head temp/warmup sensor
-VW VR6 Injectors, ~200cc/min, adequate for my unrealistic 120HP maximum possible believable output
-Custom Surge Tank to house a Bosch 040 In-tank high performance fuel pump
-Modified current RJS fuel cell for surge tank return
-UMP intake system utilizing their Solex airbox - a DEAD MATCH for the Mexi TB!

Let's begin! Parts stash accumulates....




Mario's crank trigger showed up, I didn't find it difficult to fit with the help of my 78 year old lathe.


Drilled and tapped and secured with awesome little 4-40 TORX drive screws from McMaster. (NOT pictured, I replaced them later)


Now it was time to retire to the CAD computer to plan my surge tank design and program the CNC machine to make it. I wanted to integrate the Bosch 040 pump instead of the wildly more popular "044" due to it's relative affordability, built-in intake filter screen, and more than adequate horsepower support for everything but the most radical air-cooled VWs.


While I was at it, I also laid out a control box of sorts to contain the MicroSquirt and fuses in a sealed environment. We have a laser cutter at work so I utilized that to cut the backplane to mount the components.








The actual making of the surge tank was, as you might guess, far more brutal than expected. The CNC part was easy, but making the surface finish of the pump mount bore adequate to seal and perfectly round required me to make it a little small on the CNC machine, and then bore it painstakingly at home on my manual mill.








I had to make a mount, which compared to the level of detail required on the surge tank, was sort of a side project.


Then I sent everything off for anodize, machined the shell tube on my lathe, honed it and assembled!

[panel]

Wow that is so really cool stuff you've made ! Right on

[jimmyhoffa]

Thanks! I'm trying to keep this one moving to keep everyone's (and my) attention captured.

I try not to get too pedantic with the parts. I usually try not to "do things for the sake of doing them" when multiple solutions are commercially available, but the surge tank had a special calling to me. I wanted something compact, which meant using a pump with a filter inlet, so I didn't also have to package a filter internally. Off-road land is a dirty land, and I figure having things apart in a parking lot or working on something out in the dirt could potentially introduce contaminants that would recirculate through the fuel system if I had an unfiltered pump intake inside the surge tank, as many of them are designed. The 044 also draws notably more current than my 040 at most equivalent flow rates. This extra flow was of no benefit to me as I, and most of us, really just don't need that horsepower capability.

What I am doing with a cheap off the shelf components is the feeder pump to the surge tank. I considered both the Carter P60430 and carter P90091. A call to Carter confirmed that the pumps are identical internally except for their pressure valve, and both would be suited as low pressure feeder pumps to a surge tank. Naturally, I would have chosen the cheaper one, but first I thought I would attempt it with these Facet Posi-flows I had around. Their flow rate is more than sufficient for my horsepower, and since there will be very little restriction, they'll be able to flow very close to that maximum output.

Plumbing the surge tank looks like this:


I am fairly dissatisfied with the length of rubber EFI line and am looking at all my options. I'm thinking of machining custom fuel rails with AN fittings on the end to replace the plastic Mexi pieces, and then using a PTFE banjo-to-AN line in place of the long rubber one from the fuel pump.


Now, more on that UMP airbox. I had the filter and the intake scoop, so I just needed their Class 11 Solex intake box. It fits right on the Mexi throttle body and has a somewhat parabolic velocity stack built right in!






Until next time boys N gals.

[Schweg]

Your parts are very nice I hope to have a shop with half those capabilities and the know how to do it.

Are you running without a fan or tins?

[jimmyhoffa]

Thanks Schweg! I've worked really hard, like my entire life, to learn all this stuff. It's nice to finally slap all my half-baked abilities and ideas together to make something work! I will be running with fan and tins, I just had them off because I was mounting the coil and adding throttle cable provisions and the like.

Next up was satisfying the needs of each component by giving them power and signal wires, whether it be to or from. I went on eBay and ordered a bunch of color-coded GXL wire with that super temp resistant super abrasion resistant insulation. The wire handles very well. It holds shape without being too stiff, and the general bulk of the insulation is sort of a light duty strain relief in itself.




The MicroSquirt is sealed, but not SEALED sealed, so I wanted it to live inside of a control box with the totally unprotected fuse and relay block so I wouldn't have to worry. This is the real-life version of the box I designed earlier, brought to life, with a few tweaks!




Pulling the box with the whole engine harness off the engine takes all of 10 minutes, so I pulled it to tidy everything up and clean up a few loose ends in the control box.


Another pro tip for building control boxes and automotive wiring. Apparently a lot of circle track dudes already know about these, but a company called SEALS-IT (google them) makes a wide array of super high quality molded pass-thru grommets and other similar products. They are reasonably priced and when I say look them up, I MEAN IT!! They're awesome. They are also conveniently available on McMaster Carr, the same place my control box came from.




Lastly, I started in on the design of my single gauge pod for my AEM wideband and the Acceleration Enrichment and Cold Start LEDs.


This is designed to flow aesthetically with my dash, which I have already made and put into service.


Until next time ladies and gents.

[kangaboy]

With the way you're building this thing, tuning and tweaking it is going to be a breeze...looking forward to it. Perfect driving weather right around the corner!
I have a nice TD04 sitting on the work bench that would look lovely hanging off the back of that thing
I give it less than a year

[jimmyhoffa]

Haha I hear ya, I'd give it a little less than less than a year.

I didn't want to let the cat out of the bag, but let's just say I'm going to get two gauge mount plates laser cut, not one. The other one looks like this, and I wonder what gauge it might hold....

[Ol'fogasaurus]

Rails around here they took off the street a long time ago. In the fog and other low visibility settings they disappear plus they don't do well in wrecks and other things. They almost took buggies off the street too but so far they haven't.

Anyway thought point: mounting stuff on the upright(s) can cost you some visibility so be careful as it; like so many other things, this too can easily get out of hand. I've also noticed that not too many rails have sun visors .

Lee

[jimmyhoffa]

Lee, I hear you there. I 3-D printed the gauge mount plate and block, and it is definitely too big. I am going to have to reconsider the mounting provisions, likely resulting in a gauge pod on top of the center of my dash. It only blocks the view of my right front suspension then, which is unfortunate, but not mission-critical.

Since the 3-D printer works nearly for free, that leaves me to do other things.... and I'm pleased to say that the Chenowth has become somewhat self-aware! The intelligence level is still much more like that of an angry baby throwing food at the wall than a full-grown adult supporting a family with a stable career, but hey, self-aware is self-aware, right?

Wiring roughed in and terminated!


Another view:


And it's alive! Injectors go CLICK CLICK, it picks up crank signal, fuel pump relay provides power to fuel pumps. Throttle Pos. sensor works, and a Shop-Vac on the intake gives a vacuum fluctuation through the MAP input! All the signs of life are there!

[jimmyhoffa]

Instead of just being "alive" its ALIVE!! It started for the first time with the assistance of Kangaboy on here.

Here she is, idling off the ole' laptop. Tweaked idle and base timing a bit, just working through calibrating my AEM Wideband output to the MS.


I was overly pessimistic. Kangaboy tweaked for a second or two on the laptop, and I turned the key and it fired IMMEDIATELY. He seemed kinda sad that I didn't have the throttle cable done because I just figured it wouldn't work right away. So, I set about doing that. I used Kartek control cable and retainer clips, and it works very well!






Here's some shots of the current situation:

[whaczup]

Very impressed and inspired! Thank you!