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On "Microsquirting" the Porsche 914 - Part 10, The Design Details

Part 10: The Design Details

Back to Part 9

So your first question will be, "can I do this?" Yes, you can. I did it and I'm not a professional mechanic, though I do have an engineering background and fairly solid mechanical and electrical skills from working on my own cars since high school.

Your second question is, "how hard is it?" Well, that depends on that skill level.

The majority of the components are bolt-on, such as the sensors - I tried as hard as I could to make it easy - but you'll need three basic abilities:
  • Ability to remove and install the engine.
The biggest issue here is access, with the hardest being getting to the back side of the fan housing to install the crank position sensor. I guess theoretically you could remove the front air cooling sheet metal and get to the front of the engine and remove it all while working from the underside. But having the engine sitting on your toolbox or on an engine stand makes the processes soooo much easier.

Removing and installing the 914 engine is really not that hateful. Basically, you remove the shifter rod, remove the eight bolts holding the CV axles to the transaxle, a couple wiring harness, clutch and throttle cables, four bolts holding the drivetrain to the car and it's out. I have the advantage of a lift at home so I raised the car and lowered the car down on my big 44" Harbor Freight toolbox, unbolted the four drivetrain mounting bolts, and lifted the car out of the way. Look for Series 9 Episode 5 of Wheeler Dealers where Edd China did it using a lift.

Without a lift you'll use a floor jack, and I recommend Tangerine Racing's lift plate.
  • Ability to do some minor fabrication skills or access to someone that can
You'll need to fabricate three plates: an aluminum plate to adapt the Bosch TPS to the D-Jet throttle body, another aluminum plate to adapt the IAT to the intake plenum, and one steel sheet metal plate to mount the coil (nix on that coil mount. See addendums). The designs for those are listed below. These can be done with a series of hand tools you may already have, or contact Chris Foley at Tangerine Racing; he's the one that made mine and can make them for you.

You'll also need to weld the O2 bung into the exhaust.
  • Ability to read electrical charts and fabricate the wiring harness
This one's the biggie. Fabbing the wiring harness will require the ability to read and understand (a generally-offered) electric design, specialty tools for crimping/terminating electrical terminals, and specialty tools for installing and removing electrical terminals.

I tried to find a business that would provide all this as a kit (including building the harness) but no one seemed interested. I'm guessing the volume would be too low to make it worthwhile. So I'll offer to you all of my design details and you can have at it.

I've been keeping track of everything in a spreadsheet: costs, part numbers, prices (but not time; per Wheeler Dealer rules that's "FREE"!!!) Blogger's vertical format doesn't lend itself to showing spreadsheets so I posted it on Google Docs. Grab that and follow along...

https://drive.google.com/open?id=1jVNLFQIDbmaDh81jwmIC3dq7t5Yz6RkA

But I bet you're looking for the bottom line on cost. I'll spoil it: I missed my target design cost of $1500, primarily for three reasons:
  • I did not plan for the costs of some out-sourced work;
  • I did not plan for the costs of required tools, mostly for electrical work;
  • I did not plan for the costs for all the electrical harness build stuff.
Total out-of-pocket costs were $1,719.79, including the costs of the electrical components. It does not include the costs of the tools, some electrical supplies, and the out-sourced work. Also, none of these prices include tax and shipping.

Outsourced Work

As described above, the out-sourced work done by Chris Foley at Tangerine was welding the O2 sensor bung into the exhaust and fabricating the mounting brackets for the IAT and TPS. How much of this you can do yourself will decide additional costs.

TPS mount was per EricP. Details available on his Microsquirt build thread on 914World. Chris Foley at Tangerine Racing has these designs, and I'm sure if you call him up he can fab something up for you. Or you can do it yourself like Eric did.

IAT mount is not drawn up, but it's a small plate with three holes, one big and one small. Chris has that, too (nix on that; see addendums, I moved it to the airbox).

Can you weld? If so, you've got that whole O2 bung thing figured out. If not, find someone who can. Chris installed mine in the rear muffler, after the two header tubes converge but before the muffler.

The steel flat-plate coil mount bracket is easy. Here's a link to a photo of my coil mount bracket. This one I did myself. It's a simply piece of sheet metal from Lowe's fabbed into a bracket with a hacksaw, drill, vice, and hammer. Easy to make.

3/28/22 edit: Please read the Addendum notes in Part 11. I found that mounting my coil in the location of the distributor got the coil too hot and I was experiencing misfires and failed a coil. I no longer recommend this spot for mounting the coil. I mounted mine on top of the fan housing, which resolved the problem.

One other part you're going to need for the electrical harness (presuming you use my design) is one of the factory T4 pin housings, also described as the "D-Jet interface plug". See description and photo in Part 6. These are not available for sale however there should be some floating around out there, as all 4-cyl 914s were shipped with them. You can also de-pin yours (mark the wire locations in case you want to go back) and re-use it; replacement electrical terminals are available from NAPA (see the parts list).

Optional Parts

Here's some optional, but recommended, parts for this project:
  • Throttle body gasket, Pelican, $6
  • Intake manifold gaskets (runners to head), 2 needed, Pelican, $18
  • Intake runner tubes (the block hoses on the runners) 914Rubber, $17
  • New 5/16" rubber fuel line, various sources
  • Stainless 5/16" fuel injector hose clamps, Amazon B073X2W399, $14
Recommended Electrical Supplies

...not included in price sheet. I consider them tools and supplies (and I have a lot left).
  • Cloth wiring tape, Amazon B07Y9VTPTF, $9
  • Scotch 33+ vinyl tape, Amazon B00004WCCL. $4
  • PET Expandable Sleeving 1/4", Amazon B07NZLR8HS, $8
  • PET Expandable Sleeving 1/2", Amazon B07P1QRLJ4, $9
I also used a Deutsch 3-pin, connector, DT06-3S-E004-Assy and DT04-3P-E004-Assy, to have a single-plug-connection for the wires that go through the rear bulkhead: the two reverse light wires and the starter solenoid wire. This gives me a one-plug disconnect for removing/reinstalling the engine.

But here's a top tip. Did you notice that I spec'd out each individual Deutsch connector in that spreadsheet? They add up to a strong number. You can reduce your costs on a lot of these Deutsch connectors by purchasing a couple of the kits I linked to in Part Six; that's what I did and reduced my connector cost by about $125. But there are a couple of caveats on doing so:
  • You will have to file down the pin housing "keys" in the Deutsch 8 connectors that go into the two bussbars; they are not keyed correctly for those;
  • You will not have unique pin housings when you use two of the same kind of connectors, such as the Deutsch-8. What that means is you need to ensure that you mark each so there's no confusion as to which plug goes where; plugging in the 12V Deutsch 8 into the other Deutsch-8 might blow out a bunch of sensors or maybe even the Microsquirt itself...so be careful.
Maybe you use the "A" and "B" keys for the Deutsch -8s, and those lesser-expensive kits for everything else? Your call.

Tools

I purchased the following tools, also not included in the price sheet:
  • Distributor drive puller, Amazon B07622JJYN, $21.27
  • Sargent Open Barrel Contact Crimp Tool, Amazon B00CIRFUMQ, $34.95
  • Deutsch terminal release tool, Amazon B00A6AS4G6, $26.07
  • Bosch terminal release tool, eBay 292357522562, $6.49
  • Deutsch Pick Removal Tool, Amazon B00O7S43AE, $12.65
  • USB-Serial Adapter, USB-2920, $22.49 at DIYAutotune
  • RS-232 extension cable, TuneCable6, $5.50 at DIYAutotune
  • TunerStudio MS Ultra, Tunerstudio.com, $99
I also bought the Eastwood Weatherpack crimper kit, PLA00010, for $86 but that's when I thought I was going Weatherpack on everything. The tool still works OK on Deutsch stamped connectors but I suggest it's redundant to the Sargent tool above. I'd suggest finding a good ratchet-action dual crimper designed for the Deutsch pins (or, even better, go with Deutsch barrel-type connectors).

I think that were I to do this all over again, I'd just do it with Deutsch barrel-type connectors. Love those things.

Wiring Harness Build

By far, other than working through the general design, the most difficult and time-consuming part of this project was fabricating the wiring harness. I've got half the battle fought for you: I've already done the design. Now you just need to fabricate it.

Wiring harness pics

Harness pics can be found in my Google Drive folder for this project.

Harness lengths chart

There is a worksheet in the Excel Workbook linked above, labeled "Wire Lengths." That chart shows distances between connectors, referencing the connector numbers as labeled in the "Wiring Harness Design Board" photo.

Connector Pinouts

There is a worksheet in the Excel Workbook linked above, labeled "Connector Pinouts." That indicates the wiring locations within each pin, referencing the connector numbers as labeled in the design board photo.

The Build

My suggestions.

Print out my wiring harness pic as large as you can, and tape it to the wall where you can easily glance at it.

Print out each and every one of Mario's wiring diagrams for the Microsquirt and tape them to the wall. If you don't have a color printer then bring them to FedEx Office or something and do them in color:

http://thedubshop.com/microsquirt/

Get a big piece of plywood, at least 4x4 if not bigger, and prop it up somewhere vertical where you can stand/sit/work comfortably. Use that design board photo above and my Excel spreadsheet to draw on that plywood, in 100% scale, exactly where these connectors will go. Write in the connector numbers and what they're for and drive a nail into each location where you can wrap wires ends there. Draw it out so you can run the wires to that location on the plywood. Resist the temptation to add too much length to each (though an inch or two won't hurt).

Add more nails where wires make turns so you can bend the wire there.

Next, decide where you're going to mount your Microsquirt. If you're going to the same place as I did, then no additional length will need to be added to the drawing. However, if MS will be somewhere else then you  will need to add that much length to the mounting point of the Microsquirt ECU. BTW, my wire harness was about 3-4 inches too long but still manageable, and it gave me plenty of slack to accomodate engine movement. I'd not change it if you're going to the same place.

After everything on that plywood is marked and nailed, review all the wires in the MS harness and split them between what you'll use, and what you'll not use. Take some painter's tape or Velcro strap to keep them separated. Check, recheck. Once you're satisfied that you've got it right then de-pin unneeded wires from the Amphenol connector and put them away in a safe place (they're easy to add back in later if you make a mistake, or change your mind, or want to add a feature.)

All set? OK. Drive a nail in the board where the Amphenol connector belongs and use a tye-wrap or Velcro strap or tape or something like that to secure the connector to that nail. That's "home base".

Now it's time to start running wires. Starting from sensors the far end and working inward, take each wire from the MS and route it to the appropriate components connector nail, one by one, bending around turns to that connectors and then. Wind a few turns around the nail then trim off the excess. Leave yourself some good slack as you'll tidy 'em up later but don't feel the need to make the wires either too slack or too tight. Make 'em just right.

Trust me, that first cut will take some courage, but it'll get better. At this point all you're really only risking the $79.95 MS long harness. Any terrible errors at this point can either be repaired, or the harness replaced.

After all the sensor/MS wires are done, then do the same for all the 5V power and grounds for the sensors, coming into and out of connector C4. Use the excess trimmed to run it to the other sensors from there.

A note on the sensor 5V ground wires. The MS uses the black/white for sensor grounds. However was not enough excess wire for me to use that color for all sensors grounds. So, you will see a note in my chart that I used some black same size wire that I had for the remainder. There's nothing wrong with that, as long as you notate it and ensure you keep track of it. And remember that MS also uses black for chassis grounds for things like the O2 controller, coil, and the MS itself. That is a distinctly different ground situation than the sensor grounds so don't get them confused. I probably should have bought some additional white/black wire to finish with but hey, "he was on a roll" and didn't want to wait.

Next. run the wires for all the 12V-powered components: injectors, coil, wideband. Those all home back to C3.

Once all wires are run, and you've double- and tripled-checked everything, now you can start working on trimming, stripping, and terminating wires. Don't worry about wrapping the harnesses in the sleeving yet, because you've bought the correct tools to de-ping the terminals which allows you to put the protectives sleeves on later...which you'll do when you're done terminating.

Trimming, terminating, sleeving done, grab some cloth wiring tape and wrap up the edges; try to get it as weather-resistant as possible (water loves to capillary to odd places).

All done? Grab a beer and enjoy your work. You deserve it.

Chassis Wiring

You'll note there's some wiring that needs to be done on the car for the MS to interface, on the car side of connector C2. Your C2 connector will have wires that needs to go to the T4 relay plate plug, tach to the T12 plug, and (optionally) the T12 plug for starter, oil pressure switch, and reverse lights. You'll also need to install a relay to take power from the battery and drive the aux relay. All that is in the chart.

You'll also need to install a Tach-A-Dapt behind the factory tach in order to get it to work, and a diode behind the gauges from the GEN light to the engine bay so that the engine turns off with the key.

I told ya: the hardest part is the wiring. But you're almost there.

Installation

OK, job well done. Install all the major components and sensors, ensure proper wiring protection from crimping, bending, chafing. Install the wiring harness and secure it properly. Look over your work and get ready to re-install in the drivetrain.

Note, you'll probably need to leave the injector rails off  for drivetrain installation, as the hoses stick out to far and will interfere with the body of the car. I'd suggest buying a set of the factory angled fuel injector hoses to assist with that.

Installed? Ok, turn the key on (but don't start it). Your first clue that things are likely good is that you'll hear the fuel pump run for a couple seconds then turn off. That indicates that the MS has power and that it is controlling the fuel pump. If that didn't happen then recheck everything.

Jump the fuel pump relay and check for fuel leaks. Crank it over to see if it cranks.

Tuning

I'm guessing you're aware that your Microsquirt likely does not have a configuration, yes? Without that, it won't start. I'm hoping you have a basic understanding of EFI and Microsquirt and can config the box to at least get things rolling. Here's some basic resources you'll need.

TunerStudio software. The tuning application. I purchased the TunerStudioUltra MS version to have full access to all features.

USB Adapter. The MS comes with the RS-232 tuning cable, but not too many laptops have RS-232 ports any more. Use this adapter to interface with your USB port.

Alternatively, use EFI's Bluetooth adapter. I bought this, too, and ran the MS cable through a firewall hole I drilled near the engine lid release cable. I then use Bluetooth on my laptop to connect to it.

Megalog Viewer. Reviewing all the logged data afterward to work on your tuning. I paid for the HD version.

For basic startup, go to Mario's TheDubShop pages and review the specs for each sensor. He lists in each how the products should be set up. I chose to pay Mario to give to me a basic startup file, but I've tweaked it quite significantly since then. I've also contracted PF Tuning to help me improve the file significantly.

Or, you can take it to someone that has access to all these tools, can configure the unit for startup and proper operation for you.

What Now?

As I write this, April 2020, we're in the midst of the COVD-19 lockdown. I've gotten out a few times to do some tuning and I really do like the way the car drives. Starts nice, drives smooth, shifts nice, snappy throttle, and if the VE chart is a good indication then the torque has been improved and moved upward around 750RPM higher (and I can feel it). That means better driveability and more horsepower. Once this breaks I'll be looking to take it to a dyno and get some hard numbers and finer tuning. I'll update info here as I have it.

I know this is but a shell of what you're looking for, but I hope it's a good start for you. I'll be re-reading and editing these posts for errors and clarifications, and I'll watch the comments section for questions.

If you're interested in trying it yourself, don't hesitate to give it a shot!

Greg

FAQs

Would you be interested in building a harness for someone?

I'm hesitant to do that for a few reasons: primarily, I'm not an automotive professional (though I believe I do professional-quality work); it could be a big liability for me if something goes wrong (what if someone sets their car on fire?) or I made a bad mistake and hurt something.

I can offer the design I have so you can use it as a baseline for yours.

Finally, and most importantly, it wouldn't be cheap. To motivate me to build one, I expect the price would exceed what you'd want to pay for it (and certainly more than what you can do it for yourself!) Maybe we can find a company that is interested in the work?

Would you be willing to consult/assist someone with theirs during their build?
Sure. Leave comments here and I'll respond when I can.

Can I have your msq file?

As with building a harness, there's liability involved. I'm concerned that someone may just dump the file into their own car and not use the tools to ensure it's applicable; a bad tune can wreck an engine. It's something we can discuss.

Do you know if anyone can offer this as a kit?

I hope to find someone someday, but I have not as yet. If you know anyone that's interested, I'll be glad to give them all my design details and history not included here, as well as offering consulting services to ensure they're successful with this design.

Go to Part 11, Addendums and Lessons Learned

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