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

[VaccaRabite]

So L-jet was on VW buses and 412s starting in 1974.
So there it is. I thought VW was using D-jet on the late busses. But that's the business case for it.
I am very surprised that L-jet did not replace D-jet across the range if it was cheaper and better, but I suppose that the D-jet components had already been purchased and it made more sense to use them up.

Loving this thread on the 914s weird middle child.

Zach

[wonkipop]

So L-jet was on VW buses and 412s starting in 1974.
So there it is. I thought VW was using D-jet on the late busses. But that's the business case for it.
I am very surprised that L-jet did not replace D-jet across the range if it was cheaper and better, but I suppose that the D-jet components had already been purchased and it made more sense to use them up.

Loving this thread on the 914s weird middle child.

Zach

the answer to that one is not too difficult Vacca.

USA Fuel regulations. easy to forget but USA is introducing unleaded fuel way in front of other countries. The 2.0 L porsche tweaked 2.0 had already been developed with that in mind. it comes way after the VW 1.7 engine which dates from 1969.

there was always two versions of the 2.0
euro with 8.0:1 compression - ran on 95 RON.
USA with 7.6:1 compression - ran on 91 RON
the USA 2.0 was able to run on unleaded fuel from the get go.
unleaded when first introduced could only be formulated with a low octane rating.
compression ratios had to come down.
no need to rethink the 2.0L, they could just leave it alone until the end of its production run. it was a 914 only engine anyway. the numbers were not there to bother with deveioping a special engine with new injection. at best 10,000 engines in 73/74.

The 1.7 engine had higher compression than the 2.0
8.2:1 - ran on 98 RON. world wide.
and once they dropped the compression ratio for california in 73 it was a disaster.
horsepower dropped from half respectable 80hp to 73hp.

time line on fuel was -
in 73 all new cars in california had to be able to run on 91 RON unleaded.
rest of USA in 74.
and worse - in 75 california by law had restrictor in filler and would take only unleaded 91. (Suspect thats part of the reason for later plastic expansion tank on fuel tank - its designed with the restrictor in mind).

and VW production needs on the 1.7 (smaller engine) were much larger numbers. 412/914 + Bus for first time.
so that engine got reworked.
had to be bigger to compensate for lower compression for 91 RON.
+ the engine was going to go on in the bus at a minimum so they gave it the new EFI system.

gradually everything VW got the new system bit by bit including the beetle.

you can see the quandry for the last of the 412s in 1974.
the high compression 1.7 soldiers on with a 8.2:1 and will only take 98 RON.
could not be sold in california on fuel requirements alone.
and technically ought not to have been sold in rest of USA.
i suspect VW pulled the same trick as they did with the 76 914.
they probably only made it up until the end of calendar year 1973 which meant 1973 standards could be applied. technically it was likely a 73 for certification purposes but sold in showrooms as a 74 while stocks lasted.


here are the specs for the 74 412 from owners manual.




i suspect that no matter what D jet hit the wall emissions wise by 75.
the 76s never met 76 emissions standards and certification.
were sold as 76 model year but under the certification regime were classed as 75s if manufacture ceased by end of calendar year 1975 - which they did.

hence the 912E gets L jet. would probably have been too strangled dowb with D jet.
it is a certification standard 76 MY car.
as it was the L jet on the 912 copped a lot more gear on it than the last of the 1.8s.
smog pump for instance. no 914 L jet had a smog pump.


---------

and one last thing to bear in mind. L jet did not require payment of a royalty stream to bendix. not as far as i know. so bosch could turn that drip off once they finished with D jet.

far as i can work out last car to ever have D jet was the Jag V12. finished up in 1979.
probably went on that far because it was a specially developed developed system for 12 cylinders and they milked it for as long as they could. there was something funny about d jet that meant it worked in multiples of 4.
4 cylinders. 8 cylinders. 12 cylinders etc. jeff bowlsby would know exactly why that was.