Running high impedance injectors on L-Jet intake
 

This probably won't apply to many, but just thought I'd pass this along for anyone swapping to an aftermarket ECU on a 16v car using an L-jet manifold. One of the issues/hassles is mounting newer, high impedance injectors. There have been some posts about folks drilling out the L-jet injector bosses to clear the wider pintle cap and seal of the later injector.

I happen to have the injectors out of my S4 and the injectors out of a 4.7 L-jet on the bench last night. I pulled the pintle cap, seal, and spacer off the 19lb injector from my S4, and did the same on an L-jet injector. The reach of both injectors was the same when measured with a caliper. I was suprised by this because the L-jet injectors appear to have a much longer reach due to the shape of the pintle cap. I pulled the pintle cap off the L-jet injector, and it fit perfectly on the S4 injector.

Here are some (crappy cell phone) pics:

http://i710.photobucket.com/albums/w...mporary-22.jpg

http://i710.photobucket.com/albums/w...mporary-23.jpg

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I've got a 4.5L K-jet in the track car, and have an L-jet manifold lying around. This will allow me to, with just a manifold swap, put in some late model injectors with L-jet pintle caps and I'll be good to run the MS 3.57 EFI.

I've sourced some L-jet pintle caps at injector-rehab.com (SKU: 2-103) that I think will work and will try out. Unless of course someone has a Porsche part number for it or knows of a source for the OEM part.

So here's the latest. These are 42lb bosch injectors (green giants).

Here's a shot with the stock pintle/seal/spacer, all of that removed, and with the low impedance pintel cap. There is an o-ring that goes around the low-z pintel cap which is not shown here.

http://i710.photobucket.com/albums/w...mporary-36.jpg

I didn't realize it at the time (as it wasn't mentioned in the ad), but the green giants are four hole injectors. My concern that the pintle opening would be too small in the low-z pintle caps was short lived, they were fine:

http://i710.photobucket.com/albums/w...mporary-28.jpg

Here's the injector in the runner. I transferred the big grommet that goes around the body of the injector that is held in place by a monster c-clip, and the o-ring that goes on the injector tip. It all fit together snugly:

http://i710.photobucket.com/albums/w...mporary-32.jpg

The reach is perfect, here's the 42lb bosch in the port:

http://i710.photobucket.com/albums/w...mporary-31.jpg

Here's the stock low impedance injector:

http://i710.photobucket.com/albums/w...mporary-35.jpg

Still working on getting the intake clean, there's a lot of sludge in the intake runners. Once that is done, I'll re-assemble, install the injectors, and see whether or not the stock S4 fuel rails will work. Hopefully I'll be able to use all of the stock stuff I have lying around as opposed to using aftermarket.

Excellent. Thanks you for doing this leg-work. I'll be doing this as well when I go to the MS3.

Adam, that looks very interesting.... do you know whether the later injectors would also fit the runners from the Euro 84-86 LH2.2 cars ?

I have a spare set of Euro runners, the hole for the injector is 14mm dia into the runner. is this the same as the L-Jet runner ?

John,

The euro injectors as the same style, and yes they work the same way.
The only difference is that the euro inj have the same barb as the L-jet for use with the rail, but they are high imp instead of low imp.

Also, to those of you wishing to run larger inj like adam is on the L-jet cars, you can do the pintle conversion as Adam has done (I've done it many times). And if you wish to retain the L-jet fuel rail, just put the inj in a lathe and machine the plastic off above the EV1 bosch connector, under it is steel with 2 ridges, you can simply slide the right size hose over it and then use fuel inj clamps on gates 30R9 hose and it will seal perfectly, and let you run larger injectors on an earlier car without needing a different fuel rail.
I have a set of S4 injectors I did this to and can take a picture later today.

Thanks Colin ! Is it possible to Dremel the groove for the big circlip in the newer injectors , to keep them located in the head ?

Any large body Bosch EV1 injector body already has everything needed for the large C Clip and rubber for retaining. The newer design slim line injectors though do not and require a new fuel rail.

It gets better Jeremy, when I'm done I'm going to road map the entire install. It's ridiculous how much time I've spent pouring over the megamanual and the ms3efi websites to figure out how all of this goes together for our application. I'm planning on posting pinouts, wiring diagrams, and part no's of all parts used to run EDIS-8 with knock sensors. Should save a lot of time for anyone looking to do the same.


The tip OD is the same, the problem is that the LH injectors have the pintle cap with the "brim", and the OD on that part of the pintle cap prevents the late model injector from getting enough reach down into the port of the L-jet runner. Not a problem with the LH runner as they were designed to use the later style injector. The current mod on the L-jet manifold is to drill out the injector port part way to allow clearance for the later model pintle cap.


That is the "downside", you need to use the series 2 body style injectors if you want to retain the stock holders (which I did). The circlip fits in the narrower waist portion of the injector. I'll post better pics later.

Interesting comment on the retaining the barb fittings with newer injectors Colin, what in the world made you curious (brave) enough to go looking for barbs under the molded plastic?

So here's the L-jet intake, with the high impedence injectors and the S4 frame rail.
Won't know for sure if the injector spacing will work for the frame raill until it's bolted onto the motor, but on the bench it looks pretty close.

http://i710.photobucket.com/albums/w...mporary-38.jpg

Adam,

Regarding the spinning them down, I was given that information by an injector company when I was looking for large HI inj.

Resurrecting this thread.
Anyone else out there do this mod where they added Design 2 injectors to a 16v manifold utilizing the 32v fuel rails? Adding hold-downs to the rails seems straight forward enough, I'm just wondering what's involved in making the hard fuel lines work? Any pics? TIA.

Thom,

I ended up installing an S4 motor so did not follow through on this project.

Thanks.