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1981 VW Rabbit here for research (Build)

Posted: Wed Feb 17, 2021 5:39 am
by soultron
A few years ago a friend gave me an 81 Rabbit Mk1. Most of the general stuff you'd expect for a car this age.
The diesel engine died and I swapped it out for a 1.8 8v from an 87 MK2 but didn't have most of the fuel injection parts so I ran it on a carb for a while. After researching Speeduino I'm mostly sure this is a better route than trying to round up all the very old Bosch pieces.

The current goal is to start with just do fuel off MAP/TPS and work towards distributorless ignition with a trigger wheel.
Hopefully this is practical enough. I'm only collecting parts for now. I picked a fuel rail with regulator ( VW digifant stuff ) and fuel pump. I also have a trigger wheel and EDIS coil I got off a car I was scrapping. I see there are lost of options for assembled boards but one thing I need info about is harnesses to the ECU. I know I'd be splicing into my ends for sensors and such, but I'd like to not have to make the board end.
Either way, I'll be asking around and looking for existing info here during this journey.

Edited to add pic
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Re: 1981 VW Rabbit here for research

Posted: Wed Feb 17, 2021 7:05 am
by tigerstyle
Post pics of the project!

I'd try to straight to no distributer, and try and et the other sensors required working.
Ecu wiring is fine, lot's of good options for boards now, and adapters available etc, luxury of an old car is that you'll never be returning to stock ECU, so cutting the connector off is no loss.

Re: 1981 VW Rabbit here for research

Posted: Wed Feb 17, 2021 4:50 pm
by soultron
I added a picture. It's not a recent one.
I'm definitely upgrading the wiring. On top of the normal VW wiring problems, the PO took the original wiring all apart.
I'm reading about wasted spark and looking up a simple trigger wheel, but I might use the distributor signal to figure out what i'm doing.

Re: 1981 VW Rabbit here for research

Posted: Sat Feb 20, 2021 5:29 am
by soultron
I'm beginning with gathering parts.
Fuel stuff first.
Mk2 Golf throttle body. I have to attach a TPS to the throttle body, but there's a lot of threaded holes, so I can make a bracket.
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Mk1 intake manifold. It needs to be opened up for the bigger TB (technically the small side is more shrouded ). There's a few ports to plug, and I don't think I'll need the enrichment injector, but it can stay until I get a block off plate.
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Mk3 or so fuel rail. Need correct injector cups but should only have to drill and tap one hole for the bracket.
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The tank is a side exit so I'll have to get creative with the fuel lines. It already has a return line, but I'll have to make a bracket near the tank to hold the pump and filter.

Re: 1981 VW Rabbit here for research (Build)

Posted: Fri Mar 05, 2021 7:45 pm
by soultron
Changed the MK1 throttle linkage so it pulls in a better direction.
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Working on a TPS bracket. Not sure how much room I have but trying to make it compact. There's an Audi TB that is supposed to work and has a TPS but I had this laying around and wanted to try it.
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The car was a diesel so I have to make a bracket for the Fuel pump. ( though I could look for the factory one )
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And here's what I'm trying for the intake. It has a place for the IAT and hopefully sits in a suitable location. won't know till I pull the carburetor parts.
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And I finally ordered the ECU.

Re: 1981 VW Rabbit here for research (Build)

Posted: Fri Mar 05, 2021 10:08 pm
by Chris Wolfson
This engine was build for a long time. Dont waste time with modificatins on the manifold. There are electronic injection variante where all your parts fit and are positioned at the right places. The mechanical injected version you got is much rarer than the newer one!

Re: 1981 VW Rabbit here for research (Build)

Posted: Sat Mar 06, 2021 1:28 am
by soultron
Chris Wolfson wrote: Fri Mar 05, 2021 10:08 pm This engine was build for a long time. Dont waste time with modificatins on the manifold. There are electronic injection variante where all your parts fit and are positioned at the right places. The mechanical injected version you got is much rarer than the newer one!
Porting for this TB is a common upgrade ( Most plain Jane thing I'm doing here )
There is a vw fox specific intake that I wouldn't have to port for the TB ( have not found one yet) but other than that fitting some of the later parts is not always simple. I have the MK2 Golf manifold but I haven't seen a lot of Rabbit folks use that for swaps, so I figured it either doesn't work ( It points the opposite way than the original ) or is not work the trouble. The later cars have different engine bays and layouts so some stuff interferes.

Re: 1981 VW Rabbit here for research (Build)

Posted: Sat Mar 06, 2021 2:28 am
by Chris Wolfson
Where are you living that Golf 2,3,4 are so uncommon animals?

Re: 1981 VW Rabbit here for research (Build)

Posted: Sat Mar 06, 2021 4:27 am
by soultron
If it's not clear, here's what I'm explaining.
( there are pictures )
http://www.scirocco.org/tech/mk2/5000tb/5000tb.html

The fuel rail and injectors I'm using came from a later car ( Digifant ), but the later Golf counterflow intake manifold TB is on the right of the car. The Mk1 is on the left. There's more space for airbox, especially if you relocate the battery. Obviously the crossflow from later cars ( like the mk3 )intake wouldn't even fit. The Corrado and Fox intakes are on the correct side and already opened up for the TB but supposedly don't flow as well. I'm fine with using the parts I have if I can't find those for now.

Re: 1981 VW Rabbit here for research (Build)

Posted: Sat Mar 06, 2021 6:46 am
by Chris Wolfson
You seem new to the VW conversion community.
My comment was not about larger throttle blades, these do not help the engine at all, if you look for horsepower, by the way.
You are converting from mechanical K-Jetronic to a real Motronic. You need to fit electric injection valves, that do not fit your "K" manifold. You don´t need cold start valves and stuff.
I do not see your problem with the intake to the other side, this problem does not exist.
Maybe have a look at a picture of one of the many Golf I with a 16V engine