ECM Questions 240z to 280z/zx swap??

[Unfairlady]

Alright so this is my first Datsun. Bought it about two weeks ago and how I assumed I got a deal on it I was quickly reminded of why I hate buying modified cars. I'll explain it like this:

It's a 73 240z, I bought the car from a guy who said that the car had already been l28et swapped. He told me it used to run and that the cam gear had sheared off the previous motor and that he had just put this motor in he found in a savage yard from a 83 280zx turbo, and explained that he didn't have time for it anymore because he had another project he was too busy working on. I quickly looked over the car. saw it had a P90a head so I figured sure its a turbo head atleast, the car was low on rust, and the man seemed honest enough.

Well I got the car home on a trailer and started looking over everything. Started well enough but would act weird above 2500 rpm. I started look at everything and realized that the O2 wire wasn't going anywhere. So I started looking for the male plug in for 02 sensor. Can't find it. I start wondering if I'm blind and start looking up diagrams to see if I can find what color wire it is to see if somehow the wire got placed somewhere else by accident and somehow itd still start.

I finally got frustrated enough to check the ECM and found the tag:

Part no.: A11-600-000

Lot no.: 5Z12

For: L28

Boom. I look it up and from what I can tell the ECM is for a 75-78 NA l28 and then I start looking and come to find out these don't have O2 sensors (never had a car that wasn't carbed and didn't have a oxygen sensor)?? This is where I start to get lost.

I am beginning to think that the car was a l28 swapped car when he bought it. no turbo and this guy just threw a turbo l28 engine in it thinking he could just do that. plug everything in and "yay, I've got a turbo car" when he realized lifes not that easy he sold it.

Okay so....

That ECM Part no. is that specifically for a 75-78 l28 non turbo car?

Did they have oxygen sensors or not?

How can I tell what the AFM is for?

Whats the differences in the harness between a 75-78 l28 non turbo harness and a 83 l28et?

If this is a AFM and a ECU for a NA could I just throw a header on this engine and call it a day or would this be hell to make work with this ECU or what?

Anything could be helpfull.

I know this is a very open ended question in a way and I realize I am a noob and I did search but I am so confused with what I have at this moment I'm alittle lost on what even to search for...

Thanks for anything.

[Zed Head]

Yes, that is an early L28 ECU, for an NA car. Stock turbos did not show up until the 81 280ZX.

Oxygen sensors did not show up until 1980 in the 280ZX's.

The number for the AFM should be on the black cover or on a sticker on the AFM body.

The most noticeable difference is that the pin-out (where the electrcial connections go) is different. The connectors are similar but the wiring is totally changed. So if that L28 ECU is plugged in and running the engine, the car never had a turbo ECU. It would require the turbo EFI harness.

Some people do use the NA ECU and a rising rate fuel pressure regulator to allow a turbocharger to work without blowing up the engine. Which raises the question - is there actually a turbocharger? No offense, but it's not clear what you know and you did not mention one. The L28 NA ECU would probably run a turbocharged engine but it would not have any power under boost. Which kind of sounds like what you're describing.

I think that you would have to remove the turbocharger to get the engine to run more close to normal. But it will still be down a bit on power because the compression ratio is low, for the turbo. It could be done but it would be Z blasphemy.

In short, it sounds the guy might have swapped in a turbo engine like he said, got it to run using the NA electronics, but never installed the turbo electronics to make it run right. Which is about what he told you.

[Unfairlady]

Thank you that confirms what I was thinking and Yes it is turbod he pulled the engine from a 83 280zx turbo. all numbers match a 83 turbo on the engine and has the Air Research turbo. It goes lean at about 2500 like I said, So like you said I was thinking the ECU must be a NA, I don't really care if its a fast car. I just wanted a low rust 240z.

So next question if the AFM checks out as a NA because from what I am deducting the wiring harness is for a NA as well. I grab a header for a p90a which is a square port head and move the MAF to to the correct position on the NA engine and hope he hasn't modified the harness at all. which from what I can tell he hasn't, and technically it should run.

Next question is the 70-76 square port E31 head the same size ports and location as the P90a head because its also a square port.? or Do I have to specifically buy a header built for the 81-83 turbo P90 head.

[Zed Head]

The ECU has already determined your wiring harness. You'll want the up-to 1976 square port headers, the engine bolt patterns and spacings are all the same, it's the body style that was different with the ZX's P90 head.

Might be cheaper, easier and quieter to get a square port 280Z exhaust manifold. With your low compression ratio engine, in stock form, the header won't really add any performance. Apparently the stock manifolds flow pretty well. And where is the AFM now? There aren't many non-stock places for it to be.

One problem you might find is that the PO left the turbo injectors in the engine. They will cause it to run rich, with the 280Z ECU, becuase they flow much more fuel thanthe NA injectors. They're a dark purple-brown color, whereas the NA injectors are a light-green or tan color.

Somebody out there would probably trade a complete 240Z or 280Z engine, or two, for that turbo engine. Maybe even for just the turbo and turbo exhaust manifold. They're popular items.

[Unfairlady]

Hmmmmmm, well the injectors are green. well how about after I make it home from work I'm going to take some picture and post them up here. and the AFM is right in front of the turbo apposed to right in front of the throttle body. where it comes stock on the l28et is where it is now.

So i think I have NA injectors. On a turbo engine.. How hard is it to find a 81-83 turbo ECU and Harness? because I can't seem to find one that's not been molested

I am just going to take alot of pictures of cast numbers and stuff tonight and post them up. See if we can't figure out what I have.. Because I am pretty sure I know but I was never a Datsun/Nissan guy up until this point so I may be way wrong.

[Unfairlady]

Here are some picture I have taken. I decided to bypass the turbo and run it as if it was a NA. It will rev above 3k but when the car is pulling itself down the road and you actually put the engine under torque it kills itself off at about 2500-3000 rpm. I'm wondering if my fuel pump is not sufficient enough for the injectors above that.

I'm going to try to attach those pictures:

[Zed Head]

That's a turbo AFM. Here's a link showing the part number - Motorsport! Air Flow Meter, 81-83 280ZX Turbo - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

I don't know that it will work right with the NA ECU. Nissan changed the way the AFM's are wired with the ZX's. Look in the Engine Fuel chapters of a 280Z FSM vs. a 280ZX FSM and you'll see (1976 versus 1982 for example). The NA AFM uses 4 wires for the potentiometer, the ZX only has 3. But the 4th wire might just be the altitude switch circuit in the NA system (discussed in other threads). Anyway, it's unclear that the turbo AFM will work right for you. You might want to get an NA AFM.

Those injectors look like aftermarket. They have numbers on them that will tell you what they are. Probably NA since I don't think the turbo injectors are available aftermarket.

[EuroDat]

IMHO Since your setup is a mixed up combination of turbo and non turbo equipment, I would go back to NA. Its the most logical IMO.

The steps you could take to to it are not that hard and you might come out in front pocket wise

Find a N42 head. It has the recesses for the injectors, but you will need to get the valve seats done. That head will get your compession back up to standard 280Z CR 8.3:1. The NA engine in the 280Z had the N42 block with the same dished pistons (10.9cc).

I wouldn't go looking for an E31 head. They will bolt on, but they are getting hard to find which means $$$$ and you will need to do the work with replacing valves, and valve seats. It wont get the high 240Z CR with the dished pistons. You will actually get a CR around 8.6:1. Still good, but there are alternatives.

The N47 on the Maxima (Not the 280Z) would be much better and will increase your CR to just under 9.1:1 which is where the E31 was on the L24. Don't compare it to the N47 on the 280Z. It has "closed" quench chambers and doesn't have the exhaust port emmision liners.

You will need another exhaust manifold which is stamped N43 for the N42 head or N36 for the 260Z will also fit. It should have square ports.

Fit your injectors (Green are JECS N76, I believe. They NA injectors) and inlet manifold to the new head. The AFM you have is for a NA engine

Finally: Sell the turbo and P90a head to recoupe your costs on the other head.

Its the route I would take and I think it would make a nice stock engine and a lot less hassle than what you would go through trying to find all the parts you need to get your current setup running right. This is considering the bottom end it still in good servicable condition. A compression test will tell you more on that.

Chas

Edited March 15, 2014 by EuroDat

[Unfairlady]

Yeah I am starting to think I will just go back to a NA set up. If I ordered the correct AFM would the engine run correctly even though the compression ratio is so low at the moment? Until I decide to switch the heads out.

and I thought that my block was flat top pistons.? so wouldn't with any other head I would be running like over 10:1 compression ratio?

I thought it was already 8.8 CR.

[Unfairlady]

So now I am trying to find the correct AFM for my ECU and I think its the A31-060 001 that goes with my ECU which is A11-600 000. Am I correct to believe this? and where would be a good place to come across a re-manufactured one without sending in the core because obviously I don't have one.

Thanks guys you've been alot of help

[Zed Head]

That AFM and ECU is a matched set, they're designed to work together.

Since you've discovered all of this strangeness though, you might take some time and put a full plan of action together. Obviously you know how to get around the interweb and are finding lots of information, and know what to do with it. But you have a collection of odd parts and could take many different paths from here. You could get the wiring harness, distributor and ECU from a turbocharged engine and have a very powerful turbo L28 240Z. Get the NA head for your dished piston short-block, and an NA AFM (if needed, still unknown), and NA exhaust and have a standard L28 NA EFI engine. Get the NA AFM and headers and have a low compression ratio L28 (which might sill be as powerful as the original L24). Put carbs on it. Or tweak and tune what you have to make it work.

But there are still questions. It's been assumed that you have a dished piston turbo motor, but maybe the PO just put the P90A turbo head on an NA L28 block. Look down below the motor mount on the driver's side and make sure it says F54. Then pull a spark plug or two and locate a piston that's at the top of its stroke. With a good light you may be able to see if it's flat or dished.

Did you get any extra parts with it? The turbo engines use a special distributor so the ECU (also special) can control timing. Could help determine your path or make sourcing parts cheaper. Barter for parts.

[EuroDat]

and I thought that my block was flat top pistons.? so wouldn't with any other head I would be running like over 10:1 compression ratio?

I thought it was already 8.8 CR.

If its still running original pistons, it will have 7.4:1 CR. The P90, P90a and P79 (P79 is NA head in the 280ZX) all have the same chamber capacity 53.6cc. The turbo engines used dished pistons like the 280Z to reduce the CR. Thats why going for the N42 is a good bolt in option (Except for the Silicon/Bronze valve seats need to be replaced with steel).

Im using a A31-626-000 on a NA unit. The AFM you have should work alright.

There are lots of different part numbers for the ECU. They did small changes to them quiet a lot over the years. The 280Z started with A11-600-000 I think and they ended somewhere around A11-639-800 in the NA 280ZX.

Chas