Why did the 1.8 engines have L-jet? Options

[VaccaRabite]

Has there ever been a reason Porsche/VW speced L-jet injection for the 1.8 engines instead of D-jet like the 1.7 and 2.0 engines used?

Usually when manufactures do this there are financial reasons for the change. Either they have the same engine on other vehicles they produce, or its just cheaper to use whatever part is being used.

But Porsche didn't use the T4 motor on other cars at the time. And if it was cheaper, they would have done away with Djet on the 1.7 and 2.0. I don't think VW was using l-let at the time for the bus... but maybe?

There has to be a reason that Porsche wanted Ljet on the 1.8.

Zach

[technicalninja]

Progress...

The 1.8 was born AFTER Bosch created and de-bugged the L-jet.

The D-Jet was rare enough that I have never had to work on one and I believe that system did not go "World Wide".

The L-jet was the recipe that CREATED what we have today.

It went worldwide and although I have little Porsche experience, I have SHITLOADS of L-jet experience as Nissan jumped on the L-Jet bandwagon early.

If you're not constantly changing, you're stagnating, and the competition will leave you behind...

L-jet was the way forward IMO. (IMG:style_emoticons/default/ninja.gif)

[JamesM]

The D-Jet was rare enough that I have never had to work on one and I believe that system did not go "World Wide".

D-jet was on a TON of cars in the early 70s. Just not to many that people care about today.

BMW 3.0Si, 3.0CSi, 3.0 CSL
Citroen DS21, DS23, SM
Jaguar XJ12 XJ-S
Lancia 2000 HF Coupe, Berlina
Mercedes-Benz - To many to list
Opel Commodore GS/E, Admiral, Diplomat
Porsche 1.7, 2.0 (Of course)
Ranault 17 1.6 TS, Alpine A110 1.6, Alpine A310 1.6
Saab 99 E, 99 EA, 99 EMS
Volvo 142 2.0E 144 2.0 E 164 3.0 E, 1800 2.0E, 1800 2.0 ES
VW 411 1.7E, 412 1.7E, 1.8E 1600 1.8E

I would suspect @brant is correct and that it was a result of L-jet being a more modern system and VW updating their engine offerings.

D-jet "calculates" airflow by a Speed-Density calculation, that is it senses manifold pressure, air temperature, and RPM and applies those values to an ECU tuned to a specific engine configuration. Granted d-jet did this with very complicated analog circuits it is the same concept as Speed-Density base systems today. Basically a look up table that returns the predetermined amount of fuel based on the inputs. Some shortcomings of this sort of system ANY changes to the engine that impact airflow at a given RPM and load result in your mixture being off as the engine is flowing differently than the ECU was set to fuel. So displacement change, cam change, possibly exhaust changes and even engine wear over time will throw your mixture off.


L-jet actually measures the airflow via an early airflow meter so when conditions of the engine result in airflow changes at a given operating state you still have an accurate mixture as its measuring the airflow and not calculating it from a lookup table based on other factors.

I imagine Bosch and VW moved to it as a cleaner, more efficient way of fueling and the 914 got it as a result of the VW product offering changing.

But Porsche didn't use the T4 motor on other cars at the time. And if it was cheaper, they would have done away with Djet on the 1.7 and 2.0.

Porsche did actually wind up eventually doing away with D-Jet on other variants of the Type 4. The 1976 912 E got L-jet on the 2.0 Type 4 (914 motor) Had the 914 survived longer I suspect all motors would have received L-Jet. Suspect it didnt in 76 as the 76 cars were basically Porsche clearing out the remaining parts from 75.