L-jet Throttle body needed, or will D-jet work?

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tomcolitt

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Does anyone want to sell one and an L-jet fuel rail? Although I took a closer look at a d-jet throttle body I have and please correct me if I'm wrong. It looks to me as if I can accomplish the same thing with it? There is a port on it that connects to an air passage before the butterfly valve AND in between there is an air idle valve adjusting screw. So I could just eliminate the motorized idle air valve from the Motronic 1.3 and use a manual idle air adjustment screw similar to what I have on my 1984 Euro M30B34, which works great. It seems to me this would be the most elegant and original-looking solution in a Coupe? Does anyone have any objections, except that I wouldn't have any continual, automatic idle air adjustments which I don't need (since no AC or automatic transmission, etc...)

I'm also still trying to find out if the 1.3 harness needs to feed into the alternator wiring (blue wire?)... Does anyone have any wiring diagram that would help me to figure out how to wire the 1.3 harness to an e9? Most connections are clear to me, but a few seem different than on my 1.1...

Thanks, Tom
 
Here is the 1.3 schematic for you.
 

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You will need an additional air slide valve if you don't use an ICV
 
Excellent. Thanks Don. Why is the idle control screw that's in the d-jet throttle body not enough if I have two hoses attached to either side of it. One of them with the air pressure of the plenum (at the cold start valve) and the other just behind the butterfly valve, via a passage that is drilled across the venturi and connects to the adjustment screw and a port that appears to normally be closed off for D-jet. On my 1984 Euro 735i/ e9 conversion there is also just a manually adjustable idle air adjustment in the 3.2/3.5 manifold. This was the stock set-up for a 1984 735i. No other air slide.

The 1.3 motronic doesn't NEED any input from the ICV, does it? I think it also doesn't NEED an oxygen sensor connected, is that correct? I understand that was mostly to make the system most efficient for emissions....

Many thanks, Tom
 

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D-Jet vs. L-Jet throttle body for Motronic conversion

Sorry for the late reply Don as I've been trying to catch up and understand what I have. It's looks like my Euro 735i motor with the 061 ecu does have the additional air slide valve as you said, but it looks like I haven't been using that feature. I searched all over for the connector that is supposed to go to it and I can't find it, although I'm quite sure that the harness goes together with that ECU. I've been running it this way for quite a while now, but obviously it takes a little while for it to idle well until the engine warms up....

More importantly, if the idle air screw on a D-jet throttle body is not enough to control the idle air in all conditions (and also why does it pull that air from the valve cover breather?), is there a way of plumbing both the idle air (which is built into the D-jet throttle body) and the air slide valve together, using just a d-jet throttle body, some hoses and the Motronic ICV?

Or must I use the L-Jet throttle body that, I think, has an additional hose nipple on top of the throttle body to plumb the additional air slide valve, instead plugging the ICV into the side of the rubber boot, as on a true Motronic set-up. Is that correct?
 
The additional air valve operates on heat from the engine as well as electricity.
Yours appears to be broken. Throw it in the freezer for an hour, note the aperture and blow through it. Now connect to 12 volt battery source for a few minutes and note the aperture.
Blow through it again. If either the aperture doesn't change or you can always blow through it you consider it broken.
Motronics, ljets, and kjets all used these devices.
Motronic cars from Europe such as the 1986 745i did not use ICV's
You can be Euro Motronic and use an idle screw and no ICV
You will need a functioning warm up device though.

Your idle screw is open to the bottom of the front side of the throttle body and the valve cover.
It is a classic solution for emissions and idle control. Later versions used a vacuum hose and a bypass loop to the intake and an independent ICV.
 
FYI- ljet throttle bodies are all over the junkyards - I took one off the '76 530i in Fairfield yesterday. I see there is another at the oakland yard today. Cost at the bone yards run about 50 bucks and you have to pull it or pay to have it pulled.
Easier to buy one from double o2 salvage or Carl or Coupeking.
 
Hi Don

So are you saying I could not make a D-jet throttle body work properly with the Motronic 1.3 if I plumb in the ICV?

I have been searching for any L-jets at alll the SoCal yards for the past month. Not a single one...
 
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Djet throttle body doesn't work with later TPS.
Call one of the local sources and buy one.
Good luck with your project!
 
Thanks Don. I've been running my 1.1 Motronic with my d-jet manifold for years and the TPS bolts right on there. I just plumbed the ICV into a custom air fitting that I grafted into the rubber boot. Now, I'd like to eliminate that graft if I can come up with a more creative way to plumb in the ICV. I was thinking maybe a Y fitting at the valve cover breather. One goes to the spring loaded idle air screw in the d-jet throttle body and the other goes to one end of the ICV? The other end of the ICV goes to where the old D-jet cold start valve was mounted on top of the plenum? So far, I just though that out in my head tonight, but I'll take a look at it on the car tomorrow to see where I probably missed something. What do you think? Could that work?

Also, I have a black connector that goes to the thermostat housing as well as the blue one and I've noticed that most 1.3 guys only have the Blue connector. It seems like that should be the thermo time switch although I'm not finding that on your 1.3 diagram. Does the 1.3 need the Black connector and which of those two do I use for my temp gauge in the dash (from Memory Brown/ white?)....

And finally, again for the more original look, I wanted to keep using the 1.1 ignition coil on the 1.3 Motronic set-up. I can't imagine that the coil output would have changed much, although the appearance obviously did change a lot. Will that be ok?....

Thank you!
 
Since Motronic 1.3 uses no cold start injector there is no thermotime 8 second sensor..
Blue sensor is the 026 temp sensor and that leaves the gauge sensor. You need to decide which wire in the harness you will sub for the br/white wire
Motronic ecu's with no 02 sensor connected generate their own internal signal of .45 volts as a limp home model. You will get correct air fuel maps at WOT and during cold starts,
 
I like the LJet throttle body better...

The lump on the DJet throttle doesnt work for me - thats why I use the ljet version
 

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I'm glad to hear that you also leave the O2 sensor disconnected which is how I plan to run the 1.3 as well. I looked at the plumbing for the D-jet again today and the way I see it, hooking the ICV inlet straight to the valve cover breather and the ICV outlet to the former cold-start air fitting at the top of the log is should be basically the same as on the factory Motronic set-up, where they plug the ICV directly into the big air intake hose for the AFM, (which is directly connected to the valve cover breather hose as well).

Now, the only missing piece would be to connect my idle air screw at the very bottom of my d-jet throttle body to the same valve cover breather which isn't so easy because things are very tight down there. The big question for all of you now is: Does the idle air screw HAVE to go to the valve cover breather too, or can it draw it's air, lets say, straight from the atmosphere (i.e. nothing connected to the fitting at the idle air screw)? I'd love to discuss this with you, Don or anybody who can tell me if I'm getting something wrong. I think it would make for a nice e9 conversion to use the correct d-jet throttle body.
 
you could also look at Carls installation for the ICV- its hidden away under the C tubes.
 
I did see it, but he doesn't use a d-jet throttle body. I mostly wanted to hear if my logic was right, that it would work in principal. Also, have you used a 1.1 coil on a 1.3 system?...

Thanks, Tom
 
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