Out with the Megasquirt!, and in with.... Options

[JamesM]

and in with.... well... MORE MEGASQUIRT!!!!

Little back story here and then a bunch of pictures.

I have several 914s but the one I refer to as my "autocross car" (which started as my daily driver in the late 90s) has AFAIK been running Megasquirt possibly longer than any other 914 on the planet. For the last 17 or so years it has been the platform I have experimented on and in that time has seen at least 5 different Megasquirt configurations across 2 different motors. This ongoing project is one of the reasons I am so intimately familiar with both Megasquirt and D-jet as to date all the configurations I have ran in this particular car have done so using an unmodified d-jet wiring harness which required a good deal of study/reverse engineering.

At one point my focus was on making a completely stealth setup (looks exactly like a d-jet system) which I did, however as the Megasquirt feature set improved over the last 17 years and my focus moved more towards the overall performance of the system I kept hastily hacking in additional features (mainly having to do with the addition of full ignition control and O2 feedback) and an ancillary rats nest started to grow around my once stock looking system. Remembering what all extra wires plugged in where started to become tedious, especially if I would go extended periods without doing anything to them. With the desire to change/add additional elements to the system I decided I needed to just bite the bullet and build a whole new system from the ground up. Technically i have been planning (sitting on the parts) to do this for years but as the current system ran just fine it was lower on my priority list. The whole COVID situation has allowed me lots of time to get pretty much every other project done on all my other cars, so it was time to move forward with this one.

Details on the system coming out:
ECU: Completely custom (see homemade) ECU board based on the MS1 2.2 circuit design however I modified the injector circuits to supply a switched current rather than a switched ground in order to work with the D-jet harness, and then later retrofitted an MS2 CPU to expand the feature set.

Injectors: Stock 914 2.0 off a stock pressure regulator

Ignition: Full timing control currently triggered via Pertronix pickup modified with a pullup resistor in a stock distributor with a locked out mechanical advance. Output is then from the MS system to a Mallory 6AL CD box (this was a really easy way to trigger a coil from Megasquirt back in the day as it can take a logic level input)


The Goals of this project
1. Cleaning up the engine bay wiring and simplifying the connections (single harness plug to the stock relay board and thats it!)
2. Move to a 36-1 crank trigger
3. Add a 2nd MAP sensor for real time barometric correction (we have some high mountains around these parts)
4. Eliminate the distributor and CD ignition box
5. Swap the LC1 wideband controller for the newer(and smaller) LC2
6. Use a modern Fuel Injector with known voltage offset values (will get more into this later)
6.Stop using the d-jet harness (Will elaborate on this as well)


WHY???!?!
Back at the end of the 90s I was a d-jet purist, carbs to me have always been a step back and never an option for me, so when my d-jet system started acting up one of the things I did at the time was to purchase a new wiring harness made by a company called R.E.S. Systems. This was the only NEW replacement harness available at the time and is still an absolute work of art as far as i am concerned, overbuilt like no other d-jet harness you have ever seen. Needless to say it was not a piece I wanted to take off the car and replace with whatever homemade harness my limited experience could coble together at the time, so i invested time in figuring out how I could retrofit an MS system (also very new at the time ~2003) into an otherwise stock d-jet setup. Now, while doing this does result in a system that works as well as a good d-jet system I am here to tell everyone once and for all that D-jet does have some inherent faults with its design and that those faults become very apparent when you can see them in data logs and also when you realize that a lot of the known d-jet operational "quirks" follow you when running a modern ECU on the d-jet harness. The nicest d-jet harness in the world does not eliminate these issues, they are inherent in the design.
So in the interest of having the best running car possible a new design harness is needed, which is fine by me as i want to integrate everything into a single harness anyways.
Other things to come with the new build, modern 43 PSI injectors should atomize the fuel better, in addition having known voltage offset tables is mandatory to achieve the most consistant tune across all operating conditions. The change to the 36-1 crank trigger is for increased accuracy but also to improve ease of cold starts over the 4 tooth cam trigger.
Getting rid of the distributor was not mandatory but I had an idea for a new setup I wanted to try out, so its getting worked in the changes as well.

Had a week of vacation time to burn after Christmas that seemed like the perfect time to get this all done so...

on with the show...

[GregAmy]

Sounds like we're brothers from another mother...

I can't say enough how happy I am with the Microsquirt system I did last winter (with "bespoke" harness).

However, I'm now building an AW11 Toyota MR2 race car, and I am even more impressed at DIYAutotune's PnP system for it. I mean, it is seriously one well-thought-out bit of kit; I'm shocked that not all AW11 cars are running these ECUs. If we could only design and fab a PnP system for the 914 DJet harness... On the other hand, I can't leave well enough alone either: I've already ditched the AFM, added wideband, and I have COPs and a 36-1 coming in for it...

Subscribing! - GA


Edit: for future consideration, I am now using the 14Point7 Spartan 2 Lambda controller for my installs. Tighter install and has a much heartier lifecycle reputation than the LC2 (I've already replaced the O2 sensor in the LC2 in the street car). I get mine from a buddy, Conover Motorsports: https://www.raceconover.com/shop/spartan2

[JamesM]

Sounds like we're brothers from another mother...

I can't say enough how happy I am with the Microsquirt system I did last winter (with "bespoke" harness).

However, I'm now building an AW11 Toyota MR2 race car, and I am even more impressed at DIYAutotune's PnP system for it. I mean, it is seriously one well-thought-out bit of kit; I'm shocked that not all AW11 cars are running these ECUs. If we could only design and fab a PnP system for the 914 DJet harness... On the other hand, I can't leave well enough alone either: I've already ditched the AFM, added wideband, and I have COPs and a 36-1 coming in for it...

Subscribing! - GA


Edit: for future consideration, I am now using the 14Point7 Spartan 2 Lambda controller for my installs. Tighter install and has a much heartier lifecycle reputation than the LC2 (I've already replaced the O2 sensor in the LC2 in the street car). I get mine from a buddy, Conover Motorsports: https://www.raceconover.com/shop/spartan2

(IMG:style_emoticons/default/beerchug.gif) indeed brother! I kept an eye on your build when you posted it, I was impressed as a lot of people struggle with MS builds but it looked like you knew your stuff. Very clean.

Ill have to crack open that ECU I removed and show you what is inside. PnP to D-jet is basically what it is though, should plug into any d-jet car with minimal effort. I added other features later on hence the additional wires out the bottom, but it originally looked 99% like a d-jet ECU from the outside.
One issue with it though is it wouldn't be legal to sell as in its current state it violates the MS license agreement by running a custom PCB. The Microsquirt module used in the all the PnP systems these days wasn't around back when i built this thing so i just had to wing it. Somewhere on an old hard drive I have the gerber files for a PCB I designed using the MS 2.2 circuit diagrams that would have been a direct replacement replacement for the board in a d-jet ECU. I think I may have posted pictures somewhere on this board of it back in the day. Never went so far as to get it printed though due to all the legality questions (IMG:style_emoticons/default/biggrin.gif)

A similar thing could be done with a lot less effort and legally these days using a Microsquirt module on top of a breakout board to the d-jet harness, but knowing the limitations of the design of the d-jet harness itself and the fact that most peoples harnesses are pretty trashed at this point, I question if it would be worth it.... If you have to replace the harness anyways due to damage may as well replace it with something of a better design. Just my current feelings on it anyways after having ran with a d-jet harness for so long.

I have had various ideas and designs for PnP ECU replacements as well as PnP systems that involve harness replacement in my head for years, Im not in the parts supplying business though and really just get enjoyment out of coming up with this stuff. Sometimes I seed the ideas to others to let them run with it. There may or may not be a shop local to me now working on some other parts to facilitate easy Megasquirt conversions, at least for their customers cars, but i don't want to spill the beans and will let them speak to that if they want (IMG:style_emoticons/default/biggrin.gif)

[GregAmy]

...but knowing the limitations of the design of the d-jet harness itself and the fact that most peoples harnesses are pretty trashed at this point, I question if [a D-Jet PnP system] would be worth it.... If you have to replace the harness anyways due to damage may as well replace it with something of a better design. Just my current feelings on it anyways after having ran with a d-jet harness for so long.

That's where I was, too. Once I committed to needing a new harness, the possibilties opened up...and I suddenly found myself surrounded in wires and wire bits...

If we could find someone to fab up these harnesses - I have mine fully documented - these could be easy mostly bolt-on installs for someone else. But, as with you, I'm not in the parts business and I don't want to get into the biz of fabbing harnesses, I just couldn't do it at a price that would make sense to others.

- GA

[JamesM]

If we could find someone to fab up these harnesses - I have mine fully documented - these could be easy mostly bolt-on installs for someone else. But, as with you, I'm not in the parts business and I don't want to get into the biz of fabbing harnesses, I just couldn't do it at a price that would make sense to others.

- GA

I believe there is actually something in the works (or at least discussions of such) between a couple well known vendors on this front. I think some people are starting to realize that in addition to all the benefits, after market injection of some sort will eventually wind up being a necessary for most to keep their cars drivable.

Already seeing similar things in the Vanagon world where complete bolt on systems are available from vendors. I think once a 914 specific system is widely available and base maps exists for a standardized system out of the box that will have them already 90% dialed in after bolt on we should see a lot more interest and adoption. Interest for sure has already been picking up but the steep learning cure and fab work is a blocker.

[GregAmy]

I think once a 914 specific system is widely available and base maps exists for a standardized system out of the box that will have them already 90% dialed in after bolt on we should see a lot more interest and adoption.

Well, I hesitate to freely offer my tune, simply because of the risk of someone simply bolting on and walking away.

But my engine is a dead-stock "Lord knows how many miles" engines and mine is a solid, safe tune. If a vendor were to offer the same exact components as I am, I'd be comfy giving them this tune as a baseline for their products, even without wideband feedback for EGO correction.

The aftermarket for something like this is an oddball, as you always risk someone taking componentry made for a different config, bolting it on, and damaging something. Then they come back blaming you.

I'm having a 2056 built right now, so no more developement on the stock engine.

[JamesM]

I think once a 914 specific system is widely available and base maps exists for a standardized system out of the box that will have them already 90% dialed in after bolt on we should see a lot more interest and adoption.

Well, I hesitate to freely offer my tune, simply because of the risk of someone simply bolting on and walking away.

But my engine is a dead-stock "Lord knows how many miles" engines and mine is a solid, safe tune. If a vendor were to offer the same exact components as I am, I'd be comfy giving them this tune as a baseline for their products, even without wideband feedback for EGO correction.

The aftermarket for something like this is an oddball, as you always risk someone taking componentry made for a different config, bolting it on, and damaging something. Then they come back blaming you.

I'm having a 2056 built right now, so no more developement on the stock engine.

Yeah, the issue with supplying a tune to anyone now is the wide variance of hardware being used in builds. Even supplying just the VE table has its issues if everything else hasnt been done perfectly or some hardware variables (such as injector dead time) have been guessed. Im in the same boat as expecting smeones shared tune file to work out of the box at this point is a long shot. With a standardized hardware configuration on a stock motor or at least a motor that was built with the same specs as the one donating the tune, this would be more feasible.