Distributor, Calling all L-Jet experts |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Distributor, Calling all L-Jet experts |
gfg3 |
Oct 5 2015, 01:00 PM
Post
#1
|
Never Too Old Group: Members Posts: 117 Joined: 5-January 15 From: Southern Virginia Member No.: 18,295 Region Association: None |
While I was trying to sort out possible vacuum leaks in my '75 1.8L FI (L-Jet) engine I noticed a couple of inconsistencies in the way the PO set up the system compared to what I believe is the correct vacuum setup:
1. The distributor in my car does not have any vacuum advance mechanism or vacuum hose connections. I thought all '75 EC code engines used vacuum advance. Am I wrong? 2. There is no vacuum line to the fuel pressure regulator. Normally there is a T in the line that connects the intake manifold with the decel valve and the fuel pressure regulator. Decel valve is hooked up correctly, but the fuel pressure regulator just has the in/out fuel lines, vacuum port is open. Can it work correctly like this? George |
Dave_Darling |
Oct 5 2015, 04:46 PM
Post
#2
|
914 Idiot Group: Members Posts: 14,991 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
The distributor part numbers sounds right. (That's a Bosch part number; there should also be a VW part number on it.)
Not all 75s had vacuum advance. All of the injected ones had vacuum retard. (I'm sure you don't have an AN-code carb'ed 1.8.) If you don't have the EGR system, then you probably never had a vacuum advance setup. The dashpot on the distributor may have a fitting on it for advance, but if so it was never hooked up. The L-jet is designed to have the fuel pressure referenced to the manifold pressure. So the port on the FPR should be hooked up to manifold vacuum. If it isn't, the fuel pressure will always be as high as it would at WOT, leading to a rich idle and part-load mixture. That may have been a band-aid for a lean mixture from vacuum leaks. --DD |
ChrisFoley |
Oct 6 2015, 11:20 AM
Post
#3
|
I am Tangerine Racing Group: Members Posts: 7,937 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
|
barefoot |
Oct 6 2015, 11:56 AM
Post
#4
|
Senior Member Group: Members Posts: 1,282 Joined: 19-March 13 From: Charleston SC Member No.: 15,673 Region Association: South East States |
If it isn't, the fuel pressure will always be as high as it would at WOT, leading to a rich idle and part-load mixture. I believe you have that backwards Dave. FP is higher at idle with L-jet set up correctly. Don't know about L-jet, but D-jet should have fuel pressure reg referenced to manifold pressure. This insures that the injectors see a constant pressure drop and fuel flow is metered solely by pulse width. Dave is correct that at idle with manifold pressure at a vacuum the injectors will see a greater pressure drop and higher fuel flow for a given pulse width |
ChrisFoley |
Oct 6 2015, 12:23 PM
Post
#5
|
I am Tangerine Racing Group: Members Posts: 7,937 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
|
Lo-Fi Version | Time is now: 15th June 2024 - 04:51 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |