1800 T4 D or Ljet injection?

[bushoarder]

Just got hold of a nice new NOS T4 1800cc 41x34 valves and have numerous bits of Djet and Ljet EFI systems.

I'm wondering if it's possible to fit either of these systems to the motor - wanna remain stock internals at the moment.

Would I find CIS better?

The application will be Cali conversion and fitted to a bug with a 901 gearbox. I will be using a plenum manifold of some sort and hope to use the stock throttle valve if using stock system.

look forward to your opinions / suggestions.

[Jadewombat]

Just got hold of a nice new NOS T4 1800cc 41x34 valves and have numerous bits of Djet and Ljet EFI systems.

I'm wondering if it's possible to fit either of these systems to the motor - wanna remain stock internals at the moment.

Would I find CIS better?

The application will be Cali conversion and fitted to a bug with a 901 gearbox. I will be using a plenum manifold of some sort and hope to use the stock throttle valve if using stock system.

look forward to your opinions / suggestions.

Read the sticky at the top of the page first, then write back if you have some more specific questions. Any of those three systems can work, Djet is probably the least likely route you'd want to go though.

http://www.shoptalkforums.com/viewtopic.php?t=114309

[raygreenwood]

I wouldn't necessarily say that D-jet is the least way you would want to go.....as it will run as well or better than L-jet.
CIS once tuned out will probably be the very best running hp and torque wise. D-jet will be the smoothest and L-jet the simplest to do....staying with the stock injections that is.

D-jet and CIS will be roughly the same difficulty to get tuned out...though there are more people that can help you on CIS...and CIS is a little less frustrating to tune.
That being said...manifold and TB sizing and ducting, and fuel system feeding are critical with CIS. Ray

[Questor]

From what I've read on other forums, L-jet seems to be more stable and easier to work with than earlier model D-jets.

I have a '74 T-4 1.8L to 2.1L that I'm rebuilding with the original EFI. Some of the problems that you may encounter are whether the ECM "brain" matches the EFIparts for a Bus, and whether or not you have the correct wiring harness.

Here is a brief list of '74 1.8L 412 T4 EFI parts and '76 Porsche 912 2.0L EFI parts. I hope this helps...

Regards, Steve
Cincinnati

VW 1974 412 1.8L L - Jetronic FI
Main Components Part Number (1)
Porsche VW Bosch
Fuel Pump 0 311-906-091D
Fuel Filter 0 311-133-511D
Fuel Pressure Regulator 022-906-035
Fuel Injector Valves 023-906-031B (Calif) 0 311-906-031B (non-Calif)
Fuel Injector Seats/Seals
Small FI Seal (Calif) 0 311-133-261
Large FI Seal 0 311-133-263
Thermo-time Switch 022-906-163A 0 311-906-163A
Cold Start Valve 022-906-171B
Cold Start Valve Gasket 026-906-179A
Air Flow Sensor 022-906-301
Auxiliary Air Regulator 022-906-045A
Head Temperature Sensor 022-906-111B
Throttle Valve Switch 022-906-111B
Electronic Control Unit 022-906-021 F 0 280 000 100
Injection Resistor Pack 022-906-079
Dual Relay 022-906-059

(1) Part numbers beginning with 923 are Porsche part numbers. Part numbers
beginning with 022 are Volkswagen part numbers. Part numbers beginning with
0, followed by a 3 digit number (0 311 906 041A) are Bosch part numbers.

Porsche 1976 912E 2.0L L - Jetronic FI
Main Components Part Number (1)
Porsche VW Bosch
Fuel Pump 923-601-111-00 0-580-463-010
Fuel Filter 923-110-176-00 0-450-905-001 0-450-905-062
Fuel Pressure Regulator 022-906-03 0-280-160-200
Fuel Injector Valves 923-606-109-00 0-280-150-105
Thermo-time Switch 923-605-101-00 0-280-130-214
Cold Start Valve 923-606-107-00 0-280-170-029
Air Flow Sensor 923-606-111-00 0-280-201-006
Auxiliary Air Regulator 022-906-045A 0-280-140-101
Temperature Sensor II 022-906-041 0-311-906-041A 0-280-130-012
Throttle Valve Switch 022-906-111-D 0-280-120-201
Electronic Control Unit 923-618-101-00 0-280-000-134
Injection Resistor Pack 0-280-159-001
Dual Relay 923-615-101-00 0-332-514-103/104/120

(1) Part numbers beginning with 923 are Porsche part numbers. Part numbers
beginning with 022 are Volkswagen part numbers. Part numbers beginning with
0, followed by a 3 digit number (0 311 906 041A) are Bosch part numbers.

[raygreenwood]

L-jet is no more or less stable...and actually has less tunability options than D-jet. People who say that L-jet is more stable.... rarely get into serious MPS and fuel supply tuning on D-jet...and patently refuse to swap from the miserable harness connector system of D-jet...to the superior dual cantilever connector of L-jet and all later cars.

In reality...the D-jet harness connectors ARE unstable because of age and vibration. The D-jet system itself is very stable.
Also since it uses a fixed fuel pressuer system....the quality of this fuel pressure and volume must be spot on.

The vast majority of differences in D and L jet regarding quality of running and stability have to do with so little information being out there regarding D-jet tuning.
But....L-jet may be simpler to find some parts f or and you may have more help available with it. Ray

[bushoarder]

thanks, all interesting reading. Still not sure which route to go, but one thing's for sure whichever system i use i'd planned on making new harnesses and adding more modern junior timer style connectors. most looms i have and have seen are pretty shagged and stiff.

The only connector that i think i need to keep is the ECU one. need to pull out the looms and look into this a bit further. I have tons of d and l jet injectors, thinking of getting one of those ultrasonic cleaners to clean em up - any experience?

[raygreenwood]

Yes, the L-jet dual cantilever connector (In the Junior timer family of AMP/Tyco) is the best. Its easy to do the injectors and trigger points conector of D-jet...harder to do the TVS and MPS...but doable if you are crafty.

There are two ways to do the D-jet ECU connectors. One is more tedious and difficult but is superb and better than factory....the other is simple but not quite as long term stable and uses part of teh original wire.

(1) Use small telecom style butt splice connectors. Snip the wire off of each ECU terminal. Carefully file the rear section until no more of the old crimp or old wire remains. Just a very even short "tang". make all 23 connectors very even. Use a micrometer. Thats the tedious part. The nusing the small telecom butt connectors and a high quality ratcheting crimper and a very small hex/coaxial coupler die (i can give you teh die #)....crimp the butt connector ferrule onto the tang on each connector. Then heat it lightly....then seal it with circuit board varnish. Crimp the new wires directly to the other end of the ferrule and heat shrink it. Superb.

(2) This method is to clip each terminal from the harness with the exact sameamount of factory wire left on each. Usually about 3". Then using the same telecom quality butt splice onnectors...crimp those ends onto the new wires.

I hate using any of the old wire...so I do the first one. Let me know if you need help. Ray

[bushoarder]

thanks Ray, much appreciated. Is it not possible to purchase the crimps that go into the ECU connectors? I found you can still buy the round 3pin connector that is used for the T25 idle stabilisation circuit from RS. I'm hoping some searching will yield the crimps so that I can use new wire throughtout - otherwise your method sounds favourable.

Not sure when I'll get round to the loom work - gotta make a whole new loom for the car too - I'm using a Golf 2 fuseboard with golf / 944 switchgear etc and new crimps, looms, connectors etc. I'm hoping to find a cheap supplier of the sureseal / GM weatherpack style connectors for some of the underbonnet and under car stuff. Hoping to make my car as reliable as possible.

[raygreenwood]

The D-jet ECU terminals are basically unobtanium. One person on either the samba of STF recently noted that they have come into alimited supply of them. They will go fast I'm sure. About 8 years ago AMP/Tycco had several thousand in stock but would not sell them because they were proprietary property of Bosch still. I don't know if that policy has changed or not.
My method of removing the old crimp and installing a new ferrule actually makes a stronger terminal and crimp....but its a bit of work.

The round pim terminals arenand replufgfor something like an idle stabilization circuit but are not reliable long-term for resistance critical items like injectors....though they certainly are no worse than the original D-jet female terminal. Just like the D-jet terminal....teh round pin style suffers from vibration and plugging wear.
Be careful when selecting waetherpack products. Only use the ones that have also been used on the European cars over the last few years. The terminals from about 2003 and down are not much better than standard D-jet. In just recent years, weatherpacck starting using decent designs of dual cantilever terminal. Ray

[Turbinepowered]

I dunno if anyone else has ever linked this, but I found this page here which gives DigiKey part numbers for the various locking tab and free standing crimp terminals in a VW... I found that enormously useful!

[raygreenwood]

I found the digikey website a while back and forgot about it. Thanks for posting it!
Its a killer source for the general harness and original component end D-jet terminals (not ECU ends). I have not had time to plug in the AMP part #'s for dual cantilever types to see if they carry any of those. A while back I made a crimp die for my Paladin frames by grinding off an existing pair of dies. Sadly....I lost that die set. The only place I see them in my 411/412 is on headlights. I should by another sacrifical die. When you need it you need. It.

[Piledriver]

The #1 thing I love about CIS:
If you run a late mode -E or -M meter, the only absolutely required wiring is for the cold start valve and the fuel pump.
You can make it entirely mechanical otherwise, and it can be adjusted to run awesome.

You cannot have wiring problems if there is no wire.

(A CIS idle air bypass helps too, but it only gets 12V, no signals)

[Turbinepowered]

I have not had time to plug in the AMP part #'s for dual cantilever types to see if they carry any of those.

Share those part #s? coworker's car is having a running problem with the injectors ('95 VW), always the same cylinder despite swapping the injectors about. The plug connectors are pretty nasty for that cylinder, so I'm thinking I might just use my lovely new crimpers to replace them...

[raygreenwood]

You might also check the coil. Does it have seperate coils for each cylinder or does it have wires to each plug from coils? I have to dig out the L-jet part number list this weekend. Ray

[Turbinepowered]

You might also check the coil. Does it have seperate coils for each cylinder or does it have wires to each plug from coils? I have to dig out the L-jet part number list this weekend. Ray

Single coil, it's an ABA powered early Mk3, still distributor fired.

Appreciate your finding those part numbers and posting them up, be a great addition to the part number base I'm looking to build up.