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...

[JeffBowlsby]

Someone needs to speak up against what some may misperceive from some of the potentially misleading rhetoric of this thread. The passion shown for wanting to improve is interesting and admirable but comes with words of caution: Many things in this thread can be misinterpreted by those that may be lesser informed. They read words like these implying defects to the OEM systems and components:

"...Lots of advantages over stock d-jet injectors..."

"...but knowing the limitations of the design of the d-jet harness itself..." and "...Just my current feelings on it anyways after having ran with a d-jet harness for so long...".

And then surprisingly with caveats like "...One issue with it [the suggested 'improvements'] 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..."

There is nothing fundamentally wrong with OEM injectors, harnesses or other parts...although they may need maintenance replacement now or in the future like any car does. Millions of cars from that era were manufactured using these simple systems and components with many of these cars still roadworthy today.

Come down to reality gents. Acknowledge that you are merely exploring nuances, refinements and subtleties at a much more intricate level than D-Jet or L-Jet was ever intended to be, and that it does not functionally need to be. You can reengineer and refine and throw lots of R&D time and money into creating one-off 'betterments' that are interesting and may offer subtle improvements but are not essential to a correctly functioning, reliable, easy and economical to maintain TIV engine unless you just are interested in the exploration and process. Hats off to you for all it takes to pursue these efforts but don't pose them in the light of being desirable or essential to the masses, or worse that D-Jet/L-jet are somehow deficient, or less worthy than the improvements proposed.

Countless VWs, 914s, MBs, and other cars run these stock FI systems daily even today with their stock components and they work as intended. Maintenance replacements for everything are available unlike one off solutions that may need specialized or custom replacement parts that may not be available in the future - and someone knowledgeable to work on/maintain them.

The stock D-Jet (or L-Jet) are reliable, well-designed and built, and durable for what they were intended to do given the state of technology of the 70s for a production vehicle. Its much less expensive and time consuming to just maintain the stock system with stock parts for the average 914 owner who wants to just simply drive and enjoy their car.

Chasing the extreme may be OK for some to pursue but its not necessary or even desirable for the masses.

By the way...I agree with you on one thig that you are not comfortable with....loose that corrugated slit harness casing unless it is just for temp mock-up purposes, it does not protect against water getting into the harness and its electrical connections. The poly braid is no better and not suitable for our open engine bays. Use a sealed, heat-resistant casing...like the factory OEM heat shrink tubing or better.

[JamesM]

Hey Jeff! figured I would see you here eventually.

Was thinking about you while I was fighting to piece together a working D-jet system on my bumblebee a few months ago. Cant count the number of times I said "I wish i could just throw a Megasquirt system on this", but some things are to sacred. (IMG:style_emoticons/default/biggrin.gif)

D-jet is a fine system for what it is and has held up surprisingly well for 50 years now. I didn't start this post to debate that point. My commentary on this comes mainly from an analytical point of view and i dont believe anything stated here to be missleading Honestly I could probably spend hours going over the improvements in injection technology since d-jet but I'm not here to prove anything, just share in 914 adventures and discovery (though i will probably wind up going over a lot of the points eventually just because i love talking about this stuff)

You seem somewhat defensive every time this subject comes up and im not sure why as there are some non-debatable points on this matter that are just undisputable realities that we need to face. For instance:

311 905 301
280 160 001
311 906 081 A
022 115 542

Those part numbers and many others present a problem as to sustaining the operability of our cars long term if we remain on d-jet, that is just a fact of life. Aside from the car I enjoy experimenting on I have kept my other 914s all running d-jet to this day, but that road is getting real bumpy and we may be approaching the end. This isn't just about improving, there are many factors to take into account.

For instance (and i don't mean to get anyone riled up by i know this next statement probably will) Some people (particularly those selling engines and servicing customer cars) are starting to see d-jet as a potential liability at this point. Consider the fact that a Type 4 motor will run surprisingly well across a fairly wide range of fuel mixtures and timings, so well in fact that many wouldn't even realize something may be amiss with their car if they have not added multiple additional gauges to monitor. Unfortunately the actual AFR+timings needed that keep that same motor from melting down over the long run is a much narrower window. Its pretty well known at this point that due to the analog nature and design choices of d-jet your mixture is already drifting around quite a bit just in day to day operation, add to that 50 year old components to which new replacement parts are NOT available and you are basically gambling with your motors longevity. I wouldn't be speaking about this stuff if I had not seen it first hand. Was driving behind another member out to RRC a few years ago and got my car bathed in oil from his exhaust after his faulty 50 year old injection (that happened to be running well enough not to notice there was an issue) burned a hole through his piston in his recently rebuilt motor

I personally dont enjoy driving with one eye on the gauges at all time, I want to know my injection is doing what its supposed to be doing without me babysitting it.
You may call that nuances, i call it piece of mind. Really the only reason I am comfortable driving my d-jet cars across the country, is because I am completely comfortable with the fact that my motor may very well blow up before i get there. Not everyone can say that.

And all due respect but saying things like:

And then surprisingly with caveats like "...One issue with it [the suggested 'improvements'] 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..."

tell me that 1. You have absolutely no clue what we are talking about and 2. You just seem to be looking to troll this thread

And yes, d-jet does have fundamental deficiencies that go beyond the fact that its 50 years old and new parts are NLA, This is evidenced by ALL THE IMPROVEMENTS THAT WERE MADE TO BOSCH INJECTION SYTEMS OVER THE LAST 50 YEARS, not to mention the obvious fact that Bosch was attempting to chase down and correct issues with it throughout 914 production. Why do you think they added that knob to the ECU in 72 among other system corrections over the years? If you want to educate yourself on this matter you could start by reading up on why critical sensors shouldn't be grounded directly to the engine. I may get more into all of the other specific issues eventually but really not interested in spending any more time defending against a trolling at the moment.

Someone needs to speak up against what some may misperceive from some of the potentially misleading rhetoric of this thread. The passion shown for wanting to improve is interesting and admirable but comes with words of caution: Many things in this thread can be misinterpreted by those that may be lesser informed. They read words like these implying defects to the OEM systems and components:

"...Lots of advantages over stock d-jet injectors..."

"...but knowing the limitations of the design of the d-jet harness itself..." and "...Just my current feelings on it anyways after having ran with a d-jet harness for so long...".

And then surprisingly with caveats like "...One issue with it [the suggested 'improvements'] 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..."

There is nothing fundamentally wrong with OEM injectors, harnesses or other parts...although they may need maintenance replacement now or in the future like any car does. Millions of cars from that era were manufactured using these simple systems and components with many of these cars still roadworthy today.

Come down to reality gents. Acknowledge that you are merely exploring nuances, refinements and subtleties at a much more intricate level than D-Jet or L-Jet was ever intended to be, and that it does not functionally need to be. You can reengineer and refine and throw lots of R&D time and money into creating one-off 'betterments' that are interesting and may offer subtle improvements but are not essential to a correctly functioning, reliable, easy and economical to maintain TIV engine unless you just are interested in the exploration and process. Hats off to you for all it takes to pursue these efforts but don't pose them in the light of being desirable or essential to the masses, or worse that D-Jet/L-jet are somehow deficient, or less worthy than the improvements proposed.

Countless VWs, 914s, MBs, and other cars run these stock FI systems daily even today with their stock components and they work as intended. Maintenance replacements for everything are available unlike one off solutions that may need specialized or custom replacement parts that may not be available in the future - and someone knowledgeable to work on/maintain them.

The stock D-Jet (or L-Jet) are reliable, well-designed and built, and durable for what they were intended to do given the state of technology of the 70s for a production vehicle. Its much less expensive and time consuming to just maintain the stock system with stock parts for the average 914 owner who wants to just simply drive and enjoy their car.

Chasing the extreme may be OK for some to pursue but its not necessary or even desirable for the masses.

By the way...I agree with you on one thig that you are not comfortable with....loose that corrugated slit harness casing unless it is just for temp mock-up purposes, it does not protect against water getting into the harness and its electrical connections. The poly braid is no better and not suitable for our open engine bays. Use a sealed, heat-resistant casing...like the factory OEM heat shrink tubing or better.