D-Jetronic Tech Web Pages

banders · Post by **banders** » Wed Jul 11, 2001 7:00 pm

I have a few D-Jetronic tech web pages at my site that might be useful to people here in this forum:

D-Jet Parts Table for Porsche 914's http://members.rennlist.com/pbanders/djetparts.htm

D-Jet Manifold Pressure Sensor Analysis http://members.rennlist.com/pbanders/ma ... sensor.htm

D-Jet ECU Analysis http://members.rennlist.com/pbanders/ecu.htm

Brad Anders

JGREENWOOD · Post by **JGREENWOOD** » Mon Jul 16, 2001 4:59 pm

pBANDERS...a NOTE. i AM NEW TO THIS SITE. Have been restoring strictly type 3 and 4 for 15 years. I have a 412 twelve two door 4-speed w/ stock injection (modified) putting out 102 horses on the dyno. Wonderful car! I read your tech notes on D-type press. sensor. I thought I was the only one around who had discovered what you know. One addition...The beutifully machined cover screw that plugs the back of the later model (diaphram type) pressure sensor, is actually the OUTER stop for the flex of the diaphram. It is not merely a cover. Without this stop screw, stopping the outward motion of the copper diaphram, the ecu over-enriches when the throttle is opened from a stopped position. The outer screw you speak of, is the inner stop for the diaphram deflection. Between the outer cap and the outer screw underneath it (which surrounds the inner screw) you are allowed to set the range and sensitivity of the flex of the copper diaphram which acts on the anaroid chambers.Setting the sensitivity of the flex of the diaphram is importent, if you have a high lift cam and a low vacume situation. This will be different for every engine.This is one of the downfalls of D-type tuning...this custom tuning was not done for every car from the factory. I have found that a good depth to start on the outer cover is...while the car is idleing, to screw it all the way in lightly, and screw out 3/4 turn...about .035-.040 by vernier. This copper diaphram, as you know,is the replacement for the full load switch of the ealier pressure switch on type 3. It effectively approximates an accelerator pump of a carberator.The type 4 D- type injection is very adjustable...if you know how. This copper diaphram...and its enrichment capabilities is the only reason that a vacume variable fuel pressure regulator can not be used on d-type. Now, if you go from a diaphram type press. sensor to an earlier, non-diaphram type...you can use a bosch 0005 type variable fuel pressure reg...w/ variable vacume. This gives you anywhere from 4-10 psi of fuel enrichment variation which replaces both the diaphram action, and the pressure switch action. I have also made numerous modifications to the trigger plate position and cam system of the p-series stock distributor. There are also some helpful valve position adjustments w/ high lift cams and stock injection that help. My engine: stock 8.2/1 domes w/stock 1.7 heads...decent port job...42x39 ATE valves..web cam grind#72 (for injection timing) w/486 lift...solid spacer 2-liter rockers w/10mm screws. Stock crank web lifters...stock rods...stock oiling system. Pertronix module, w, knology hot wire system. Numerous mods to fuel injection...mostley to mapping of pressure sensor settings, trigger plate position, fuel pressures, precise aiming of injectors etc.Also the restriction of the factory PCV valve is essential. It is opened due to a combination of blow by and vacume. It dumps directly into the area in the inatke distributor where it disturbs the vacume of the pressure sensor. On a high lift cam motor, this masquerades as a vacume leak. You can remove the rear cover of the pressure sensor adjusting screw and watch the in and out movement of the plate in relation to the operation of the PCV valve. The restricting of this PCV valve, along with a re-route of where it dumps in, alllowed fuel mixture tuning that gained 4 HP on the dyno. There are also a few minor mods to the throttle valve switch concerning the spacing of the cut-on contacts to allow faster closing off throttle to allow less of a flat spot. W7dtc 3 electrode plugs. I am getting 102 hp at 4200 rpm. Stock exhaust...ernst high flow unit. The stock transaxle (type 4) has the stock, 3.79/1.0 final drive....hot car! Also mods, to sensor II, I have substituted a variable 1300 ohm resistor to allow better hot weather tuning. I build harnesses w/ factory contacts and factory crimper, if you ever need help. Please call, I would love to chat.Ray Greenwood. 214 841 1066 [email protected]

pbanders · Post by **pbanders** » Tue Jul 24, 2001 7:35 pm

Ray,

Some really interesting info there! I'll be in touch with you sometime soon, I'm traveling for business right now.

I should have a new electrically-based MPS characterization technique up on my site within the next week or so.

Brad Anders

Va914 · Post by **Va914** » Wed Jul 25, 2001 6:07 am

What if any of the D-jet tech help pages and ideas will apply to the L-jet? Are there ay L-Jet pages like the one above?

Will a 2.0L D-jet work on a 1.8L? What parts are needed and is it worth it?

Thanks

Jim S. · Post by **Jim S.** » Fri Jul 27, 2001 7:58 pm

I have a late 72 T-3, the IM adjustment/potentiometer is not on the ECU but by the pressure sensor part #311-906-019 http://www.geocities.com/MotorCity/Shop ... otent.html has a picture. I bought the car without the potentiometer. can I make one with a variable resistor/ If yes what is the size.

pbanders · Post by **pbanders** » Sat Aug 04, 2001 10:25 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Va914:
What if any of the D-jet tech help pages and ideas will apply to the L-jet? Are there ay L-Jet pages like the one above?

Will a 2.0L D-jet work on a 1.8L? What parts are needed and is it worth it?

Thanks<HR></BLOCKQUOTE>

D-Jet and L-Jet are similar with the exception of the method of sensing load. I'd suggest that you get the Bentley Bosch Fuel Injection book (couple up on Ebay right now, or from Amazon) to compare the differences.

I'm not aware of any L-Jetronic pages like my D-Jet pages. Go to [url=http://www.rennlist.com,]www.rennlist.com,[/url] subscribe to the 914 mailing list, and find the info on Clay Perrine. He's our expert on 1.8L L-Jet engines.

Brad Anders

pbanders · Post by **pbanders** » Sat Aug 04, 2001 10:36 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Jim S.:
I have a late 72 T-3, the IM adjustment/potentiometer is not on the ECU but by the pressure sensor part #311-906-019 http://www.geocities.com/MotorCity/Shop ... otent.html has a picture. I bought the car without the potentiometer. can I make one with a variable resistor/ If yes what is the size.<HR></BLOCKQUOTE>

You need a potentiometer for this application, not a variable resistor. The schematic for the late 914 ECU's shows this potentiometer as being a 5k ohm pot. I don't know if it's linear or audio taper, but I'd suspect it's linear. Any quality pot should do, but personally, I'd use a small wirewound instead of a carbon track pot.

Brad Anders

ray greenwood · Post by **ray greenwood** » Wed Aug 08, 2001 12:59 pm

Not that I subscribe to sacrificing an operating ECU, but if you find a bad late model one...with the potentiometer on it...take it off and use it on the type III. It is the same model and is 5k. Ray

ray greenwood · Post by **ray greenwood** » Wed Aug 08, 2001 1:01 pm

Brad, when you get back to town...drop me a line. Love to chat. Ray