Replacing Ljet with 1.7L Djet on ‘74 1.8L, Ljet in pieces (literally) and have full djet Options

[wonkipop]

Something strange about that intake boot. Doesn’t look the same as a ‘74 or ‘75 9141.8L intake boot.

think its a 1.8 boot, but its been sliced off just near the throttle body where it does upward bend. (IMG:style_emoticons/default/confused24.gif)

[GregAmy]

Never call out "Beetlejuice" unless you really want to talk to him... (IMG:style_emoticons/default/wink.gif)

Yes, I've laid out everything in the blog: philosophies, processes, tools, techniques, parts, wiring diagrams. So the general engineering is already there.

However, as I cautioned you via email, Jeff is spot-on that this is not a plug-n-play system (except for The DubShop's dual-TB setup) and this project does require a range of knowledge in terms of engineering/mounting the components, building a wiring harness, and subsequent tuning. I agree with his contention that fabbing something like this requires "...[skills] with custom fabrication, electronics and software and have significant hours available to...build a harness" (I have removed the "design" part, as I think I've done that for you.)

However, as Jeff implies, selecting and mounting the components was the easy part of the project. The most significant amount of time was spent designing and fabbing the wiring harness. I didn't keep track of hours, but I do recall wiring diagrams taped to all my cabinets around the garage pretty much all winter as I worked with the engine on the stand wiring it up, wire by wire, terminal by terminal, connector by connector. It being winter, with nothing else to do exept drink beer, helped a lot in my continuing the project to completion, and not having it become a garage queen (but there were moments...)

I will stray with Jeff that it requires "exceptional" skills, as I don't think I necessarily possess that, but it does require good skills. If we could find someone to fabricate wiring harnesses in bulk to my design, then this conversion would be dramatically easier (almost "easy"). But that's not something I'm interested in doing myself.

In the end, the Microsquirt is a good little system that, honestly, is only a few generations improvement from D-Jet. Both D-Jet and Microsquirt are "Speed Density" systems (L-Jet - "Luft" - is Mass Air Flow), both are batch injection (and MS does wasted spark), but what the MS offers is a better MAP sensor and finer-measurement TPS, wideband feedback, and user tunability.

But in the end, they're the same general technology...

Glad to help as I can...but you better really want to do it. - GA

[JeffBowlsby]

Hey Greg,

If the harness is the hardest part of the swap can you post a bit of information it, or links to previosu posts? Do you have a few photos depicting the overall layout and a few of the connections?

[GregAmy]

I'll PM you. But here's a link to the Google folder:

https://drive.google.com/open?id=17R-SCgJaH...v0GYk4MgYwoSayv

[emerygt350]

I have always wondered if you could just slap this kind of thing on that plenum and call it a win?

https://www.holley.com/products/fuel_system...l/parts/550-552

[ClayPerrine]

I have always wondered if you could just slap this kind of thing on that plenum and call it a win?

https://www.holley.com/products/fuel_system...l/parts/550-552

Yes, it would work, but no it will not work well. You end up with the same issues you get with the single Weber 2bbl carb. The runners are long enough that you get fuel dropping out of atomization, and that makes it run lean some times, and rich at others.


My opinion.. If you are going to the trouble to put aftermarket FI on it, then do it right. Don't do it half-assed. This would be half-assed.


Clay

[BeatNavy]

I'll PM you. But here's a link to the Google folder:

https://drive.google.com/open?id=17R-SCgJaH...v0GYk4MgYwoSayv

Greg, the only thing cooler than your MS build and the way you documented is that it's now causing Jeff to take a second look at it.

I didn't fab mine, although I've customized some of it. Planning and putting it together would have been a significant challenge, especially without others demonstrating how things can be done.

I ran D-Jet for several years and really enjoyed troubleshooting it and learning how it works. It is a cool setup, particularly for its era. With MS it's another level of tuning and learning that, if not state of the art, at least approaches that of modern cars. It's really helped me understand FI principles better.

It's your car, and you get to do whatever you want with it (IMG:style_emoticons/default/beer.gif)

[Van B]

Something strange about that intake boot. Doesn’t look the same as a ‘74 or ‘75 9141.8L intake boot.

think its a 1.8 boot, but its been sliced off just near the throttle body where it does upward bend. (IMG:style_emoticons/default/confused24.gif)

Nope. Its not correct for a 74 or 75 1.8L. The only difference between the two years is the top port on the boot. It was enlarged for 75. I'm certain that boot is not for a 914 1.8L. It does have a single vac TB though.

And it's not cut because I can see the mold seam.

Edit: Disregard the above. I looked at the first pic and it is definitely cut. @wonkipop is correct.

[JeffBowlsby]

Gents,

One of the major concerns with each of the aftermarket FI systems I have seen is the harness which needs to be custom designed and built for each vehicle application, and to accommodate its required parts which are also not commonly repetitive from vehicle to vehicle enough to be cost efficient. The wire terminals are what they need to be to match a component - everything else is pretty much up to be designed and custom fabricated. A customized, servicable, durable harness in our open-to-the-weather engine bays is a challenging thing to acheive, because it needs to:

1. Protect the contained and routed wiring from physical abrasion and thermal extremes. In many locations in the engine bay the harness lays directly on the engine. Factory harnesses do this effectively with heat shrink tubing, which provides a liquid tight assembly at every juncture. No wiring is left exposed unless it is not in a high heat location. A primary failure point of factory engine bay harnesses is the exposed ground wires, or where rubber boots have deteriorated leaving the wires exposed to heat and liquid contamination. What I generically call casing (i.e heat shrink tubing, slit corrugated tubing, PVC, braided sleeving, etc.) needs to be a watertight system once installed and some of the materials available and used for this purpose are not liquidtight.

2. Protect the electrical connections from contamination and provide stress relief at wires-to-component connections. A liquidtight sealed system = from the ECU to the last component. Most if not all the aftermarket solutions do not achieve this. Exposed wires galore. Individual seals on individual wires with some connector designs may help but they often do not provide adequate stress relief and typically leave a portion of the wiring exposed adjacent to the connector housing. Factory style rubber boots are designed to satisfy these two functions.

A part of this problem is the hardware provided on certain components - they are often but not always, computer type electronic parts adapted for the aftermarket FI. DB25-style connections and others, may not be inherently watertight and if so, should only exist in a weather-protected protected environment. That may be as simple as locating the ECU at an interior location (in the cabin for example) or building a separate watertight case if it must be in the engine bay.

[GregAmy]

(IMG:style_emoticons/default/agree.gif)

How much would a proper harness cost? I'd be your first customer! (IMG:style_emoticons/default/beerchug.gif)

[JeffBowlsby]

Not agreeing to design or build this but there are two main costs:

1. The constructed harness. Assuming the harness is a single design, no modifications for a standardized application, fuel only - then somewhere in the $600.-1,000. range feels about right as a ROM.

2. Cost to research, document and develop the harness design in every technical detail - from layout to parts selection, possibly engineering or at least design of adapters for the TPS and other component mounting brackets and template development. The upfront investment to purchase bulk materials to produce these in quantity. Assume at least 10 harnesses as an initial offering to amortize costs - my hunch is that finding 10 buyers will be a high hurdle to cross. Budget $3-5K for this front end effort feels about right as a ROM. Amortizing this front end cost over 10 harnesses could add $3-500 per harness, and thats only if 10 buyers are willing.

Add increased cost for customized options that some will undoubtedly want to include in their system - ignition control, locating the components differently, special cases for water sensitive components, etc. - or simply do not offer these options. Offering preprogrammed ECUs would be significant to organizing a viable system with wide appeal and plug N play capability for 914 applications.

[GregAmy]

...all the reasonable economic and financial decisions I have already made (Part 10 in the blog) choosing not to replicate it except for myself.

I'll give away the blueprints, but ya gotta build it yourself.

If you want a plug-n-play Megasquirt system, buy TheDubShop's option. It's a nice piece of kit, and all ya gotta do it bolt it in. I may end up doing just that for the street car, and transferring the D-Jet based system to the race car (SCCA reuqires use of stock throttle body). Or maybe I'll just build another one of these; I know the guy that's already done it...

- GA

[ClayPerrine]

There is also this option:

https://www.allzim.com/store/356-parts/efi-...ersion-faq.html


This is an EFI kit developed for the 356 engine. It would work on a 914-4 but you would have to do things like extend the battery lead, supply spark plug wires, intake manifolds (weber carb manifolds) and extend the fuel pump wire to the 914 relay board. It should start and run out of the box, but it will require tweaking for the larger displacement of the 914 motor. The harness is built with the proper weather tight connectors and proper strain relief incorporated into the harness.

I have actually driven a 356 with this kit installed. It is way better than carbs, and will start by turning the key through the window.

Aaron ( @partsguy22 ) is the person who did the development. I have been urging him to do a complete drop in for a 914. Honestly, I have seen how they are built. It is done right. I figure to install it and adapt it to an 914 would take about 10 hours of work.

Clay

[CSoso]

And…. After all that, the compression test came back with 90, 82, 76 and 56, 1-4 respectively. Based on that, it sitting for 10-12+ years and the unknown history - am going to go with a full rebuild. So much for a quick fix and go… I even found my old single 2-barrel progressive setup from the 90’s (not going to use it!)…. The L-Jet wiring harness doesn’t look horrible - not brittle, just dirty. Am cleaning and inventorying parts. Thanks for everyone’s inputs and great conversation/information!