VW Jetronic mechanical fuel injection swap

Build projects, things that guys have come up with to make a Pinz better (or worse?) and aftermarket add-ons.
AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

VW Jetronic mechanical fuel injection swap

Post by AudioNW » Tue Feb 25, 2020 2:18 pm

After too many carb issues I have decided to change over to injection. The older VW Jetronic system has caught my attention due to its simplicity and reliability, specifically in an application where water is often involved.I know there are plenty of reasons to go full EFI but this seems more appropriate for the vehicle to me. I've collected a few Jetronic bits and tech manuals to start planning.

Current plan is as follows-

Retain OEM sheet metal air box so it looks more stock.
Build new intake manifolds for injectors where old carbs are now.
Get VW fuel system parts and find suitable location for pump and accumulator.
Adapt VW throttle body to OEM air housing.
Relocate fuel filter for engine cover clearance.
Modify VW air box and move intake higher up like original.
Not modify engine cover or vehicle in any major way.

Attached are some pics of what's been done so far. Measurements were made of original carb and VW injectors and modeling has begun for prototyping one from plastic. My goal is to cast them out of aluminum later. I was able to get my hands on a good CIS basic system for fit testing. I printed a quick TB to intake boot adapter too, its a close fit if I'm going to clear the engine cover.
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jetronic1.jpg
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Joeri
Belgium
Posts: 53
Joined: Sun Jan 05, 2020 11:09 am

Re: VW Jetronic mechanical fuel injection swap

Post by Joeri » Wed Feb 26, 2020 1:14 am

Well....i have done this like 10 years ago.... so: i used the k- jettronic from a Volvo 2.3 l engine ( 740 , 760 serie) , i drilled the holes in the original intake manefolds pointing to the valves for the injectors , i frist tried the setup you have made out but found ut that the fuel was sprayed against the inside of the original intakes where the carbs are mounted on. Using the originele stock airbox dous not work....after trying manny times to get it running i ended up buying the k- jettronic Bosch book.....and after reading it i found out that the airbox above the operating valve ( the disc that controles the feul amount to the injectors) needs to have the same volume as the engine ....so the airbox here must have a volume of 2500cc.....this is verry important , i didnt know that and used the stock airbox.....if you do it will OR run on high revs.... but will be flouded on low rpms ( to much fuel) ....or you set it up that it will run on low rpms but dousnt get enough feul on high rpms.....so it will be or to lean....or to rich running.....that i why you need a airbox with the same volume as the engine. If you are using the cold start injector....you can just put a switch to activate that one. :roll:
Last edited by Joeri on Wed Feb 26, 2020 8:21 am, edited 1 time in total.

Joeri
Belgium
Posts: 53
Joined: Sun Jan 05, 2020 11:09 am

Re: VW Jetronic mechanical fuel injection swap

Post by Joeri » Wed Feb 26, 2020 1:40 am

This is a verry rare original k jettronic on a pinz ....built form the factory!!!!!!!!!! 8)

Image

AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Wed Feb 26, 2020 10:56 am

I was unaware of the air volume requirement. Thank you for the tip and the photo of how they did it. I got further on the manifold castings and still plan on testing the system, however, I won't spent the time making brackets/fuel lines quite yet just in case it doesn't work well in this configuration.

To clarify, are you saying the total volume of air between the intake valves and the control flap needs to equal 2500cc? Not using the stock airbox assembly would make it easier to fit the parts..And if the angle of the injectors isn't enough to keep fuel from running down the walls that's good to know as well.

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Mr Zero
United States of America
Posts: 103
Joined: Fri Dec 11, 2009 1:28 pm
Location: Las Vegas, Nevada

Re: VW Jetronic mechanical fuel injection swap

Post by Mr Zero » Wed Feb 26, 2020 11:17 am

I'm curious if in coming to the choice of the VW Jetronic if you considered the Goatwerks TBI setup, and if so what caused you to choose the Jetronic? There are quite a few folks here on the forum running the Goatwerks setup with solid results, myself included, so I'm honestly curious if you did consider the Goatwerks TBI setup then what did you consider to be the pros and cons of the 2 systems when compared.

Though it may sound like a loaded question, I've never come across the Jetronic before and am always interested in alternative solutions for improved Pinzgauer performance. :D

Joeri
Belgium
Posts: 53
Joined: Sun Jan 05, 2020 11:09 am

Re: VW Jetronic mechanical fuel injection swap

Post by Joeri » Wed Feb 26, 2020 3:11 pm

The airbox above the intake ( where normaly the injectors sit) has to be the same as the engine volume... i have tried the same setup like you are going but found out that with the k jettronic system the injectors are best placed just in front of the inlet valve.... i had mine on top of the original pinz intake manefolds ( where the carbs sit on) so they where placed on top of the airbox i made to replace the original airbox....on this airbox i had the trottle body/ valve mounted and the cold start injector. I later switched to a bigger airbox and put the injectors in the original pinz intake ....there' s not a lot space but it can be done.
Why i went for a k jettronic...tis a mechanicle fuelinjection system so no sensors or ecu Things to worry about and ones set up perfect its a reliable system...The only thing that is a weak point is it needs a electric high pressure fuelpump . :mrgreen:

Joeri
Belgium
Posts: 53
Joined: Sun Jan 05, 2020 11:09 am

Re: VW Jetronic mechanical fuel injection swap

Post by Joeri » Wed Feb 26, 2020 3:36 pm

As you can see in this picture the injector(7) sits in front of the intakevalve....this is so with all k jetronic systems :P

Image

AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Wed Feb 26, 2020 5:02 pm

The Goatwerks system is superior to Jetronic in every way I have no doubt. I'm trying this route for a few reasons- My Pinz spends half the year living outside and can get a bit wet. This situation isn't good for electronics and has already killed off my diesel heater. Also the time period of technologies is a pretty close match so it seems appropriate. I also don't drive it very often and I have time to learn new skills while tinkering. If this takes a year and doesn't work that's OK. I will have learned a lot along the way.The system is dead simple too. No laptop, no sensors, almost no electrical. Just two screws to adjust mixture and idle.

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Mr Zero
United States of America
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Joined: Fri Dec 11, 2009 1:28 pm
Location: Las Vegas, Nevada

Re: VW Jetronic mechanical fuel injection swap

Post by Mr Zero » Wed Feb 26, 2020 5:11 pm

Very cool, I'm intrigued! Please keep us up to date with your progress and results.

AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Wed Feb 26, 2020 8:22 pm

Full scale test print fits great. Now to modify the shapes for casting.
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firstPrint.jpg
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AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Mon Mar 02, 2020 2:24 pm

Got the patterns printed and tested the core with a mixture of sodium silicate and fine silica sand. This might just work out assuming things keep going as well as they have so far.
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AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Sun Mar 29, 2020 8:30 pm

OK,I had some time to move ahead. Casting was fun. I first tried investment casting and failed spectacularly! Next I went with the sodium silicate method with way better results. I'm new to casting and still learning a lot.Oh how I would love to have a mill. Most of the machining was done with a router and a drill press. They fit with a nice and snug seal on the intake boots as I hoped. I am temporarily broke due to my business being closed for coronavirus vacation so progress will be slower where new parts are required.. Anyway, here you go!
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pattern.jpg
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poured.jpg (1.61 MiB) Viewed 1990 times
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sand2.jpg (1.52 MiB) Viewed 1990 times

AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Sun Mar 29, 2020 8:37 pm

Todays progress.
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Hotzenplotz
Austria
Posts: 329
Joined: Wed Jan 18, 2012 9:07 am
Location: Vienna, Austria

Re: VW Jetronic mechanical fuel injection swap

Post by Hotzenplotz » Mon Mar 30, 2020 3:19 am

AudioNW

As far as I can tell you create replacement pieces for the carburators and install the injectors there.
The pic from Joeri shows the injectors much closer to the inlet valves.
I would machine down the inlet manifolds to create a flat surface, and cast small injector holders that can be bolted on to the original manifolds there.

Just my thoughts seeing the pics ...

I wish you success !
Cheers
Albert
========================
My Pinz has NEVER been with any army

AudioNW
United States of America
Posts: 16
Joined: Mon Feb 24, 2020 7:07 pm

Re: VW Jetronic mechanical fuel injection swap

Post by AudioNW » Sat Apr 04, 2020 5:37 pm

So far so good.Early this week I bench tested the system, cleaned the injectors, made a mason jar fuel tank, mounted up the manifolds and attached the TB with a plastic printed adapter to the oem accordion boot. It's not pretty or permanent yet in any way.

Today I recived the injector inserts in the mail and cobbled together the parts for a test. No cold start valve yet made idle on a cold engine difficult but that's ok. It runs! Now I'm off to make the TB mount and work out the bugs. Good thing I've got another month of COVID Sundays to work on it.

Heres a video of its second run. It shows promise :D

https://youtu.be/NzVLZfjGvpM


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