Z31 ECU MAF upgrade for L28ET 78 280Z

[rickyellow zee]

The details of my conversion are 78 280Z with 83 L28ET, 83 L28ET harness and distributor. ....Im going to be doing the conversion soon and have read the how to's regarding this swap and understand most of it but need clarification on the "MAF Position F/wire 12 r/w (for cleaning cycle) to 33 y/l wire from z harness". This was originally automatically controlled by the speed sensor on the Z31 and my 280z does not have one. First off what is this "cleaning cycle" and what should I do about this part of the wiring process? F wire 12R/W from MAF to where? Thanks

[rickyellow zee]

I figured I would just start a new thread instead of replying the the thread below as Im sure I will be needing more help.

[NewZed]

Should be enough in these two pictures.  Either use the ECCS wire, or hook up a switch and count - one one thousand.

[NewZed]

Actually there's still some figuring to do, but that should get you closer.

[NewZed]

I think that the diagram and test description imply that the ECCS sends 1 second of power through Pin 12 of the 20 pin connector which then passes through pins C and F of the MAFS, to ground.  But it may not be full battery voltage so a switch may not work.  Best to let the ECCS do it for you.

 

Basically, Pin 12 needs to be connected to either pin C or Pin F of the MAFS.  That wire 33 is probably connected to one of those.  

 

But it's unclear from the chart if all three conditions need to be met or just one.  Looks like all three but who knows.  So your question about if you need the speed sensor is still open.

[NewZed]

This is interesting.  Nissan rewrote the chart for 1987 MAFS self-cleaning operation.  Don't know if the chart was wrong or they changed the operation parameters.  I'm guessing that the 1984 chart was wrong and/or confusing.

 

You didn't say which Z31 you had so you'll have to draw your own conclusions.  Looks like the basic design is that it cleans the wire as long as three conditions are met - engine speed went above 1500 RPM, vehicle speed went above 12 mph, engine not overheating, and engine shut off normally.  As soon as the engine is turned off, it waits 5 seconds and cleans for one second.  So it looks like you need the speed sensor if you want the self-cleaning to work.

[NewZed]

Here's the two side-by-side.  Same parameters, just a better explanation.

[NewZed]

This may be why so many people seem to get this swap "almost right" as far as the way the engine runs.  A bunch of dirty MAFS wires out there.

[rickyellow zee]

Thanks for the reply! Lots to think about. So what I get from reading the diagrams is all 3 conditions need to be met to engage the power to heat the wire to 1000c. I need to find out what the voltage to the wire is and if its 12v then Im cool with wiring a switch and doing it manually. No problem there.

[NewZed]

Actually, you'd want to know how many amps the ECU lets pass through the wire.  There might be resistance on the ECU side and 12 volts direct from the battery might just burn the wire up.  But if there is resistance on the MAFS wire then it's probably controlled there and a switch would work.

 

That speed sensor controls other things also though, like fuel cut during deceleration.  Without fuel cut, you'll get the gassy smell.  Kind of defeating the purpose of a more modern system.  Look through the EFEC chapter and see how many things have "speed sensor" as a control parameter.  Actually, there's a table on EFEC-33 (1987) that shows 4 things that use the speed sensor.

[rickyellow zee]

Heres some good info on the swap. If you dont have all the sensors the ECU will be in limp mode and run off the second map which is less than ideal. I think ill hold off on this swap till I do more research.....read

 

 

The knock sensor, there again is another problem, along with the fuel temp sensor.
when you disconnect those sensors what you are doing is reverting the ECU to limp mode, meaning the basic program Nissan built into the software. This is not the ideal mode of operation for the ECU, and in my opinion you will not get the best results from the basic program, and that is the way the ECU will operate. If you look at the FSM and all of the inputs to the ECU, you need ALL of those inputs to make the ECU operate in its desigend and programed fashion. 
Nissan designed into the software basically two maps, the primary map that the car is designed to run on. The second MAP comes into play when you get knock and various sensor failures. So you are running on the secondary map from the ECU and it cuts back the timing, and makes the engine run in less then ideal performance to save the engine from basically blowing up because of incorrect fuel/air metering. 
On a second note, one of the things JWT does with their mods is to mirror image the secondary map with the primary map to vercome sensors like the knock sensors. Another thing that is done is to modify the map for the fuel sensor that basically disables the sensor by setting the trip point to a temp that it never becomes active in the management. 

here is a site that will give you ome valueable insight as to what Nissan did with their system <http://cherrypicker.tripod.com/turboupgradeforvg30dett/id10.html>
What you guys are doing is a very good idea, however to do the conversion properly you really need to do a complete swap, and make provisions for differences like theknock sensor for example. 

FINALLY:
What are the advantages of the Z31 ECU over the 280zx ECU. Well many things, but higher performance is not one of them. You will get better fuel mileage if done correctly because you are now dealing with a 16bit digital system in stead of an 8 bit analog system, so you get better resolution and management overall from the z31 ECU. You can program the unit, you cant do that with the 280 system for the most part. The system is newer and more accessable. You will get better bottom end then the 280 system, that was the first thing I noticed with my JWT system, and that was the biggest reason I changed out my stock system amoung other things. I HATED the bottom end of my stock system. 
Anyway, I just had to comment on the topic as I have read manyt times and no one has ever mentioned all of the sensor issue.