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Hello! My name is Chas. I live in the south of The Netherlands close to the Belgium border and I am the proud and sometimes frustrated owner of a 1977 Datsun 280Z. It’s a 2.8Ltr straight six, hence the “280” in the name. Basically an early version of the 350Z and 370Z, the first being the 240Z in 1970.

My background is mechanical engineering with some electronical experience, mainly in process instrumentation, and Siemans S5, and S7 plc’s. My hobby lately seems to be, trying to get this thing running right.

You see the Datsun 280Z uses a primitive multi point fuel injection system commonly known as the Bosch L-Jetronic system although only the first two months of production used the Bosch ECU. After that Datsun and JECS copied most of the Bosch components. It’s basically a black box, and not much more than a multi-meter can communicate with it these days.

I have changed and repaired a lot of components in the EFI system, but the biggest problem is finding parts that are in good serviceable condition.
- The TIU (transistorized ignition unit) was causing trouble when it was hot so it’s now fitted with a GM 4-pin HEI module.
- Changed all the injector connectors and cleaned the injectors. Flow tested them on my own self-made flow bench.
- Re-calibrated the AFM. Previous owner played with the spring tension to correct a lean running problem. Everyone plays with the spring tension, even if it’s not the cause of the problem.
- Re-flowed the soldering joints on the ECU board. Solved some problems but not all.
- Swapped the ECU, the new unit had other problems, when back to original 
- Changed EFI relay for Porche equivalent.
- Fitted a resistor pod in the temperature sensor to ECU. Increasing the resistance in the temperature sensor richens the mixture. The ECU’s in the L-Jetronic tend to go lean with age.

I now have a problems with the EFI when its warm, but not all the time. Sometimes it will go all day without any trouble. The next day it’s nothing but trouble.
I have researched the idea of converting to a BMW 5 series EFI system, but I’m still left with an old (maybe not as old as the 280Z EFI) system with little to no tuning. Another alternative was one of the aftermarket DIY systems, but they are expensive and don’t other that much flexability.
That is when I discovered this site and been reading ever since. I still haven’t work out a plan yet, but just taking notes and deciding on what components to upgrade and which one to keep.

Well hope that makes some sence I have included some pages out of the manual and a drawing of the EFI circuit. The system is pretty much basic. Don’t worry if you can’t find the O2 sensor, it doesn’t have one.

That's a beautiful car, it's older older than me

mmm, not saying how old I am then

Once upon a time, I had a 86 300ZX, It was fun, but had to go when I went to college. Is that an escort service van in the background?

Some links that might be of interest.
http://rusefi.com/forum/viewtopic.php?f=4&t=454
http://rusefi.com/wiki/index.php?title=Manual:Hardware_Frankenso_board

Getting back to my problem at hand, I was looking at the "Frankenso 0.4 Full Bundle" and the "58 pin pigtail for the 64 pin connector" as a starting point. I will need to change some hardware on the engine itself to use it.

For example:
I would like to move from an AFM to MAP.
The throttle position sensor is a simple contact switch and only registers idle and full throttle. This will need changing. I would like to use something along the line of a 5 volt variable resistance 3-wire system.
The injectors are working ok so I would like to keep the original injectors and use a simultaneous injector pulse.
Still not sure what to to about the ignition system. The TIU (Transistorized Ignition Unit) can go, but I would like to retain the original distributor and maybe the pickup for the pulse. Later switch over to a three coil system using a wasted spark configuration, but that would be after it's up and running with most of the bugs out. That would be a long way down the testing track.
A lamba sensor. I would very much like to install a lamba sensor. Probably a bosch LSU 4.2 or a LSU 4.8.

Like I said. I have a lot to work out and I would like to have a good project plan before I start. Comes with the job.....
And I'd rather be in the group of five (or 19 running) and not the seventy odd, if you know what I mean.

kb1gtt wrote:Is that an escort service van in the background?

No it's not. Thats my next door neighbours fathers lingerie company http://www.aftereden.nl/. Some of my friends think he has the best job in the world. His car was in the garage the day I took that photo and he had the van from work. I didn't realise until everyone else noticed
Funny how everyone seems to notice that

How far down the rabbit hole are you willing to go?

Ignition could be done by adding a generic coil connecting it to the center of your distributor and using a J701 as the igniter. See reference pencil sketched schematic here
http://rusefi.com/wiki/index.php?title=Manual:Hardware#J701_NEON_engine_schematics

TPS with MAP is not really required, it could be done after it's operational.

Is this highZ injectors? AKA 1 amp per injector when turned on? Also are you saying you want one injector driver to drive 6 amps for 6 inline cylinders?

Oh, also currently programming a 314C-2 DP, if you can program these German things you can probably program anything They like their convoluted logic. I'm stuck doing it with Step7 as well, which makes it that much more fun.

We use SIPLUS S7-300 CPU 314C-2 DP and some other models with analog and digital I/O's and Profibus DP or sometimes PA interfaces. The SIPLUS can handle hash enviroments better. We use a lot of caustic soda and steam for sterilisation.
And programming, Its all german to me

kb1gtt wrote:How far down the rabbit hole are you willing to go?

Ignition could be done by adding a generic coil connecting it to the center of your distributor and using a J701 as the igniter. See reference pencil sketched schematic here
http://rusefi.com/wiki/index.php?title=Manual:Hardware#J701_NEON_engine_schematics

TPS with MAP is not really required, it could be done after it's operational.

Is this highZ injectors? AKA 1 amp per injector when turned on? Also are you saying you want one injector driver to drive 6 amps for 6 inline cylinders?

Oh, also currently programming a 314C-2 DP, if you can program these German things you can probably program anything They like their convoluted logic. I'm stuck doing it with Step7 as well, which makes it that much more fun.

Thanks for the info. I have seen similar stuff on the J701 igniter.
The 280Z came with two manufactures of injectors. DKS which are low impedance 1-5 ohms and JECS which were high impedance 12-16ohms. Im using Bosch which are origanally for a porche. Ill check the spec for them.

What I was meaning by simultaneous injector pulse was basically what the system does now. The six injectors are fired simultaneously by 6 "drivers". its not sequential. Im not looking for that last 1 percent power. Getting it to run reliably is my goal atm.

If you already have the individual injector control, sequential is probably easier than firing them all at the same time. I know Frankenso can do sequential, and if it can't already do the all at one time thing, then it would just a matter of software. I'm sure we would encourage sequential just for consistency sake, as well we are trying to focus our limited resources at some larger items.

Frankenso was designed for highZ injectors. I would expect the current and inductive energy of lowZ to create to much heat. However if you add a heat sink or can keep the drivers cold, it can probably handle lowZ.

Caustic soda and steam, sounds like fun. A significant part of my day job is best described as a spark plug in salt water. One of the byproducts is caustic soda in a reasonably low concentration dissolved in water. We use the stuff for potable water disinfectant.

The engine is now using Bosch 0 280 150 116 which have an impedance of 2.5ohm and the "Dropping resistors" have 6ohm. in series. That would give about 1.5amp.

I was planning on changing over to the bosch 0 280 150 762 and changing over to a fuel rail. They are also low impedance.
An alternative would be the Denso injectors 23250-74060 or the 195500-1970 (Mazda P/N:B6S7-13-250) for the MX-5 (Miata). They are 13.6ohm high impedance. I could also remove the dropping resitors and clean up that part of the engine bay.

Still working on a shopping list

Frankenso does not support lowZ out of the box, so either the resistor or highZ or else?

If you have that resistor pack thing in stalled, the 1.5A should be fine. It would be good, if you go native highZ as it would probably be easiest to get different injectors if you needed to adjust your flow rates or something like that some day. The resistor packs have a tendency to have some hot leads that tend to corrode a bit quicker, which means you more commonly have to do some service. However the resistor pack would work.

You are right about corroding connections. I also have problems with virtually anything the PO played with. Those dropping resistors were fairly common up to about 1984. Bosch used the on the L and LE Jetronic systems. All the Motronics have the highZ injectors.

I would like to buy the Frankenso 0.4 bundle with the pigtail, make my own harness and test it on the workbench. Adding more functionality as I go. I have a couple of complete efi systems spare to play with.

ChasNL wrote:I would like to buy the Frankenso 0.4 bundle with the pigtail

https://www.tindie.com/products/russian/frankenso-04-full-bundle/