L-jet on a 1.7 / 1.9 Options

[Literati914]

I've been kicking around what to do with the stock 1.7L, w/single progressive carb engine that came with the car that I've been messing with lately. Car's not been started since I got it, though I did hit the starter a couple of times and it sounded promising (dirty old fuel, tank, carb and fuel lines need attention). Anyway, I don't want to keep the single progressive carb for very long and was thinking of eventually getting dual webers or repros. But I've been offered an L-jet system from a 1.8L, for a good price and had some questions.

-Will it work with the stock 1.7L distributor?

-I've heard that it might run rich on a 1.7, and this offer does not include injectors - would just going with a set of stock 1.7 injectors eliminate that tendency and be the best bet?

-Also, I've had a brand new set of 96mm P/C's for 1.7 case in storage for a few years now.. I guess I could slap those on while I have the engine out for some engine bay touch up. Like I've mentioned in another thread, I hope to not have to split the case tbh. Would you guys bother and would this change which distributor and injectors you'd go with?

[brant]

The L jet and D jet parts don't interchange. The Djet is fired from the distributor and the L jet is not. you could run a 1.7/1.9 on either induction system, but think you need all of the components for that system to match (computer, distributor, mps, or flapper box)

[Literati914]

The L jet and D jet parts don't interchange. The Djet is fired from the distributor and the L jet is not. you could run a 1.7/1.9 on either induction system, but think you need all of the components for that system to match (computer, distributor, mps, or flapper box)

Yes, I assumed the D-jet and L-jet parts would not interchange. The offer includes the flapper box, computer, harness, etc. Ok so I guess it makes since for the distributor to be specific to the L-jet system.. the why of 1.7L injectors not working with the system in a 1.7L car is confusing to me (unless the elec. connectors are different). But that kinda makes no difference at this point since injectors would have to be purchased either way (I was only thinking of using 1.7 injector because in theory the volume would be better than the L-jet's 1.8 injectors). Then again, it may become a 1.9L, so. I understand L-jet is somewhat tunable in regards to A/F anyway, correct?

Also, if I'm not mistaken L-jet has no MPS, is that right? Does it have an AAR or anything else like D-jet has?

[fiacra]

The L jet and D jet parts don't interchange. The Djet is fired from the distributor and the L jet is not. you could run a 1.7/1.9 on either induction system, but think you need all of the components for that system to match (computer, distributor, mps, or flapper box)

Yes, I assumed the D-jet and L-jet parts would not interchange. The offer includes the flapper box, computer, harness, etc. Ok so I guess it makes since for the distributor to be specific to the L-jet system.. the why of 1.7L injectors not working with the system in a 1.7L car is confusing to me (unless the elec. connectors are different). But that kinda makes no difference at this point since injectors would have to be purchased either way (I was only thinking of using 1.7 injector because in theory the volume would be better than the L-jet's 1.8 injectors). Then again, it may become a 1.9L, so. I understand L-jet is somewhat tunable in regards to A/F anyway, correct?

Also, if I'm not mistaken L-jet has no MPS, is that right? Does it have an AAR or anything else like D-jet has?

L-Jet does not have an MPS, but does have an AAR. I'm not sure that grafting a L-Jet set up on to a 1.7 is that easy to do. I think other members have done it, but I can't remember who. As much as I prefer FI to carbs you might be better off going with the dual webers or equivalent as that seems like it would be the easiest way to go. Definitely would ditch the single carb set up.

If you are interested I think I have most of the components for a 1973 1.7 D-Jet system that I bought years ago. Off the top of my head I'm missing the MPS and the distributor, but might also be missing a few other bits? I'd have to pull it out of storage to see. Since I have a 1975 1.8 I'm always interested in L-Jet parts for that car, so the L-Jet system you have access to might be of interest to me. PM me if you have any interest in the D-Jet parts and I'll get an inventory of what I have.
.

[brant]

Ljet measures flow through the flapper box
Diet measures pressure (which mathematically) equates to flow through the mps

Injectors are different connectors
And more importantly the design of each of the two systems are inherently different in the theory of how the injectors work. Do not interchange.

I have a core set of ljet injectors for sale right now if you pursue l jet

Just sold an ljet distributor
And also do have an ljet throttle body (also different) if you don’t already have it

[StarBear]

Oh, not to mention different ecu (2 different ones - 74 6-pin air box and 75 7-pin air box)!

[Literati914]

The set that I've been offered has a harness and box (along with most of the other needed items), I will make sure they match before purchase.

But I would be going from a blank slate essentially. Any reason the harness wouldn't plug into a stock 1.7 relay board? What else would hold me up?

I can not really find much on conversions to L-jet - anyone know of a thread or two?

[porschetub]

The set that I've been offered has a harness and box (along with most of the other needed items), I will make sure they match before purchase.

But I would be going from a blank slate essentially. Any reason the harness wouldn't plug into a stock 1.7 relay board? What else would hold me up?

I can not really find much on conversions to L-jet - anyone know of a thread or two?

L-jet is pretty flexible to a point but don't believe you will an issue going to 1.9 ,the important thing is that the AFM air gate moving freely as they very prone to damage due backfiring .
If you download the 914 PET you will know all the parts you need ,its a great system but like any bad component is enough on its own to give a running issue .
Good luck ,cheers

[914werke]

(IMG:style_emoticons/default/agree.gif)

Ljet measures flow through the flapper box, Diet measures pressure (which mathematically) equates to flow through the mps

Injectors are different connectors (Not so much)
Do not interchange. (Agreed!)

To be specific D-Jet injectors are low impedance, while L-jet injectors are High impedance. If you note the L-jet system utilizes a "resister block" in series with the injectors that D-jet system dont.
In general L-jet was used widely on VW vehicles Buses in particular. Using the complete system from an OE 1.8L 914 on any T4 up to 2.1L should work w/o a lot of fiddling.
IME its only when you start changing to aggressive cams with significant overlap will you run into trouble with getting the AFM to play nice.
Vacuum is MUCHO important on this system & renewed seals are a must.

[Literati914]

Thanks for all the replies, it's good info on this system that I'm so unfamiliar with. D-jet I have messed with, and it was .. a bit of a struggle to make happy. But in the end, did work pretty well.

I keep hearing about the importance of not having a vac leak with L-jet, and apparently I really don't want it to back fire. I'll have to look for a vacuum diagram, unless someone has a good one to post?

[fiacra]

Thanks for all the replies, it's good info on this system that I'm so unfamiliar with. D-jet I have messed with, and it was .. a bit of a struggle to make happy. But in the end, did work pretty well.

I keep hearing about the importance of not having a vac leak with L-jet, and apparently I really don't want it to back fire. I'll have to look for a vacuum diagram, unless someone has a good one to post?

Jeff Bowlsby's website has some great information for you on L-Jet. Here's a link to the vacuum hose diagram. @wonkipop has a lot of expertise here as well. I have an all original unmolested 1975 1.8 so reach out for pictures if you need any. Good luck!

https://bowlsby.net/914/Classic/zTN_FI_Hose...L_Early1974.jpg

[Literati914]

Thanks @fiacra .

Hmm, looking at that picture.. two things: the Fuel Pressure regulator appears to be specific to L-jet (3-ports) and I'm wondering if it can be run at all with out the charcoal canister? Well my '73 is set up for the one on top of the tank, but.. could that one be used or would it be better to get the one for the engine bay (IMG:style_emoticons/default/idea.gif)

I'll take a look at Bowlsby's site, thanks.

[fiacra]

Thanks @fiacra .

Hmm, looking at that picture.. two things: the Fuel Pressure regulator appears to be specific to L-jet (3-ports) and I'm wondering if it can be run at all with out the charcoal canister? Well my '73 is set up for the one on top of the tank, but.. could that one be used or would it be better to get the one for the engine bay (IMG:style_emoticons/default/idea.gif)

I'll take a look at Bowlsby's site, thanks.

Yes, the fuel pressure regulator is specific to L-Jet. Here's a picture of a NOS one off my shelf in case that is of any help. Can't reference my car right now as it is at my second garage. Aftermarket and used are available, but Bosch is NLA. BusDepot carries a Brazilian made one that is probably decent quality. Stay away from the Chinese made knock-offs if you can. If you get to that point I'm sure I can dig up a decent used one for you from my stockpile.

Does the L-Jet set up come with the dual relay? They are available once again, but the supply comes and goes. You can reference my threads on the dual relay for more information and suppliers. It's not a cheap part to get and they are a weak spot in the system.

Not sure how to answer the question about the charcoal canister. I think wonkipop can. I don't see why you can't reuse your charcoal canister, but it's not something I've done any research on.

If you have access to it, the Bentley manual for late Beetles has a really nice section explaining L-Jet and the various components. I learned L-Jet on a Beetle and that was the most helpful and most succinct explanation that I found.

[JeffBowlsby]

Any reason the harness wouldn't plug into a stock 1.7 relay board? What else would hold me up?

The 914 LJet fuel injection harness does not connect to the relay board like the D-Jet cars do. You need the double relay, the specific 1.8L ignition harness, which hopefully has the thick cable that connects to the battery+ lug. Both harnesses are unique to LJet 914s.

Needless to say, an FI system in a box has implications that something in that box may or may not have had problems in the past. Best to know each required component of the FI system and how each functions, and be able to test its function if possible, before purchase. Or risk just paying good money for a defective part. Inspect the condition of every item, including the harnesses - if it looks like an old harness it may just be clump of old wires and not a functioning harness at all. Look for cracked casing and hardened wires where exposed, dirty/worn/broken off terminals & rubber boots, and any missing parts.

[wonkipop]

Thanks @fiacra .

Hmm, looking at that picture.. two things: the Fuel Pressure regulator appears to be specific to L-jet (3-ports) and I'm wondering if it can be run at all with out the charcoal canister? Well my '73 is set up for the one on top of the tank, but.. could that one be used or would it be better to get the one for the engine bay (IMG:style_emoticons/default/idea.gif)

I'll take a look at Bowlsby's site, thanks.

the first month or so of L jet production had the evap canister in the front trunk before switching to the engine bay location - and the D jet 2.0s for 74 switched to the engine bay can when the L jets did. makes no difference to the evap system.

an element of L jet system that may be required is the specific PCV valve which is incorporated in the oil filler cap. its a diifferent valve.. i'm not sure iif a D jet PCV valve works. maybe it does. have never looked at D jet system to know.

edit. there is a way to build the dual rela y out of 2 single relays if you have to. its documented on the Ratwell VW Bus website. i've stored it away as a file just in case i ever need it in the future (a time when dual relays are no longer available? (IMG:style_emoticons/default/sad.gif) )

[wonkipop]

as a comment. i would have thought L jet is perfectly capable of being adaptable to an engine in the 1.7 to 1.9 size range.

a former member here (an aussie) from brisbane fitted L jet to a 2.0 L engine.
he had one of the last 76 2.0 L D et 914s manufactured. think it might have even been the last day of production going off vin numbers. he got it working very well with the assistance of a retired VW mechanic friend of his. he sold the car a while back and i am not sure where it is now. probably still in brisbane with someone. he seemed to have no real problems with iit. he may have used a larger VW vanagon throttle body. and he may have played around with the AFM adjustments. not really sure. unfortunately he is not around anymore since he sold both of his 914s.

[wonkipop]

checklist of all the system components you need in the box of L injection oarts you got.

aircleaner and AFM with intake boot to throttle body.
air cleaner mounting bracket (mounts of LHS of engine bay chassis member).
throttle body and TPS (L jet specific ).
AAV valve and TTS (thermo time switch).
FPR.
decel valve (could be shared with D jet maybe not sure but probably is).
injectors (L jet specific). - shared with VW beetle from about 76 on i think. also 912E injectors are very close in spec.
cold start injector.
L jet EFI harness.
resistor pack + dual relay.
ECU.
intake plenum.
distributor. (injectors are fired off coil signal not distributor like D jet).
cooling fan with 7.5 deg before TDC marked (you can do this on any fan if you have to).
PCV valve oil filler (not sure but probably should be just to be safe).
CHT. (again not sure about that one).

a way to check the not sure about items is to compare and contrast the listings for 74 L jet components against 74 D jet and if they are L jet specific its going to be clear - ie CHT and decel valve).

100% accurate vac hoses for 74 are here.
http://www.914world.com/bbs2/index.php?sho...57407&st=40

for 75 are here.
http://www.914world.com/bbs2/index.php?sho...7407&st=280

other vac hose diagrams i have seen elsewhere on the internet are mish mashes. (IMG:style_emoticons/default/smile.gif)

in the main the differences are to do with emissions tuning.
in my view the 74 EC-B is the least compromised from that view point and the best stock set up. of course you don't have to do it exactly stock but thats another can of worms.

[Literati914]

Wow guys, great info - thanks for the help. @wonkipop thanks for that list and links too, all very helpful!