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

[Zed Head]

But your 625-000 AFM number is designated for NA. The 624-600 number is for turbo.

Motorsport! Air Flow Meter, 75-83 Z/ZX Non Turbo - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

Motorsport! Air Flow Meter, 81-83 280ZX Turbo - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

So what would the difference be then between the turbo/ECCS and NA AFM's? Maybe it's the ECCS system versus the NA's EFI ECU. Different computers, different voltages, different internal resistances? I don't know, but Nissan had two different AFM's used for the ECCS and NA EFI systems. The AFM is on the low pressure side of the intake tract so it shouldn't be a pressure issue.

Just saying, Nissan used different AFM's for the same model year. The reason is unclear. Maybe superlen will figure something out.

Edited March 15, 2014 by Zed Head

[Unfairlady]

Yeah I checked the engine block and it is a F54. I took a light and tried to look but from what I could tell it was a flat top piston but Idk I coulda just not had a good enough view. And I set everything up so that it was using that AFM like a NA engine and just left the turbo in the exhaust. But the car still wont rev above 2500k. I was looking and I thought that the AFM from a turbo car wouldnt work with a NA ECU. And it still makes no since though why itll idle fine but when I get to 2500 rpm it acts like its hit a rev limiter almost. Its very odd.

I believe the distributor set up is straight from the 83 turbo car just like the block and the heads. So idk if thats my problem or what.

[Unfairlady]

You know what. I am going to pull the gas tank tomorrow and check that just to see if maybe there is crud in the tank and I'll change the fuel filter to. maybe thats got something to do with it. IDK but I have no other plans tomorrow anyways so might as well clean and check the tank.

[Zed Head]

Download the 1976 FSM, open the Engine Fuel chapter and make sure that your TPS is adjusted correctly. The TPS is famous for acting like a rev limiter when it gets wet. Out of adjustment may have the same effect.

Datsun Service Manuals - NICOclub

Take your resistance measurements from the connector at the ECU. Download the EFI Handbook to get the pin numbers. www.xenons30.com/reference

And it would be much, much easier to take a fuel pressure measurement than to drop the tank.

Post a picture of the distributor. The 1983 turbo distributor only works with the 1983 ECCS, I believe. It's optical, not VR. Are you sure that the ECU you took a picture of is the one that the engine is actually using? It's possible that the PO wired in the 83 ECCS but mounted it somewhere else. Follow some wires to be sure.

Edited March 16, 2014 by Zed Head

[superlen]

Unfair

+1 on what the others have said. It looks like the PO grafted a NA setup onto your turbo motor, except for the AFM.

I have several NA AFMS. I would love to swap one out with your turbo AFM. I am in the last stages of releasing a digital LJET ECU replacement & I'm currently testing as many AFMs as I can to make sure I have a good stock calibration curve on them. I have been looking for a turbo AFM to compare against & your posts' timing is very good.

Here is a build thread on the HellFire (http://www.classiczcars.com/forums/fuel-injection-s30/49964-zfuel.html), which incidentally would solve your AFM problem as well. It's no problem to run a NA motor with a turbo AFM if you have the right calibration curve. The stock ECU of course is completely non changeable for anything. Of course we don't have that cure yet, I still need a turbo AFM hint hint.

PM me if you are interested in swapping out. Later if you go full turbo we can swap back no problem. I don't need to keep the AFM forever.

Lenny

Edited March 16, 2014 by superlen

[superlen]

Zed,

I haven't looked at the ZX turbo wiring or AFM so I'm just speculating here, but I think its possible that those L-JETs fed the Turbo AFM with a regulated voltage, not VBAT hence the need for only three wires VREG, GND, & wiper. That would eliminate the need for the reference resistor. Once I get a turbo AFM and take a quick look at the schematics I can confirm.

I do this with HellFire, btw. I feed the AFM potentiometer with it's own cleanly regulated 5V and read the signal back on the wiper. I also read the reference resistor but do nothing with the reading. The extra wire going to the AFM that was used for the ref can now be used as an analog input for ANY other sensor such as a wideband oxygen sensor without hacking up the harness too badly.

Len

[superlen]

Ok,

I got excited when I saw the potential for swapping out AFMs and glossed over a lot of later thread. Now I'm catching up, and have more to say.

The wrong AFM could easily explain the wall you're hitting. The AFM votage out vs airflow going into the engine is modeled in the stock ECU. It expects it to be dead nuts on. The ECU will only dump the correct amount of fuel to match how much air it THINKS is going in the engine.

This curve doesn't have to be wrong at every RPM and most likely at idle it isn't!! Both a NA and Turbo are going to have a good chance at being close enough in airflow that the slight curve difference won't matter. However, at higher RPMS the curves start to diverge.

With a mismatched AFM in there the NA ECU around 2500 rpm begins getting something different that it wants and starts metering the wrong amount of fuel (I'm guessing lean) and you hit the wall.

This EXACT same thing happened to me two weeks ago testing the HellFire. Remember I can change my curve easily through the laptop. I didn't have any baseline curve at all so I just typed in a set of numbers that I thought might be close. My engine idled (rich at first, but I adjusted and got it right)...then I started revving it up. It would fall flat around 2000rpm & I even heard a backfire. Aha! I bumped the numbers up to meter more fuel and voila I could rev to 4-5k no problem. You ECU/AFM mismatch could easily be doing the same thing.

The TPS also warrants a look AZS (As Zed Said - I have to type that a lot so I need some shorthand) and several other things could be the issue as well. Just don't assume the AFM isn't the problem because it idles nicely.

Len

[Unfairlady]

Alright so here we go. I went to check the Distributor and took a couple pictures then I found another distributor in the box of goodies that came with the car:

and the distributors are clearly different? the distributor from my box of goodies looks to be older then the one on the car.

I also took a picture of where the rubber lines go into the fuel rail just for a reference. I will open up the AFM tonight sometime. and I did check the wiring harness and it is going back to that ECM (a11-600 000) And I was reading up elsewhere and I thought they said the turbo 81-83 AFM were wired up differently then the 75-78 NA AFM. I have came to the conclusion of switching this to a simple NA. and I've already built a custom harness for one of my other projects cars and I would rather not even touch the wiring but I think I may have to either way. The harness in some spots looks like it's already been hacked and chopped.

Also with my car I can rev it as high as it needs to be but when I am actually trying to pull the car down the road it will kill itself off at about 1500 rpms now. So I am beginning to think that it is the fuel filter or something because it's the only thing that would explain the going lean becoming more and more of a issue. So as the sediment in the tank gets into the fuel filter it starts starving itself more and more. That's logical right? because the AFM would just stay at about the same RPM not get worse and worse? And the car supposedly had been sitting for over 2 years when I picked it up, So that makes logical sense.

I also figured I'd throw in some pictures of the car just to show you guys what your helping me with:

Another thing on that AFM thing, IDK about switching just yet. I've been hearing alot of mixed answers on the AFM being able to work and not being able to work. Which in my other automotive experience I would say that it'd be the most likely thing to be the issue but I don't know these. the oldest car I've ever messed with that still had electronics was a 95 chevy it was running off a manifold pressure. everything else was either Carb'd or was too new to even worry about stuff like this.

[Zed Head]

That looks like a 280ZX distributor on the engine now, with an E12-XX module (XX = 80 or 92). Pretty common self-contained module and distributor swap. The old one in your hand might be a 240Z points (I haven't seen one up close myself), or 280Z electronic distributor. Take the cap off and look. Maybe it's the one the car came with.

On the leaning - it could be the fuel pump, the filter, the pickup tube in the tank... With a gauge you could check pressure before the filter and after and test the pump off of the car. Without a gauge it's hit or miss.

There's not much to see inside the AFM. Most say it's best not to mess with it.

[Unfairlady]

I looked up the numbers on this extra distributor and people are referring to it as a Turbo Dizzy distributor people apparently use it with the MS, otherwise it wont work. or at least that's what I am getting outta these.

And I just won't open the AFM then.. Ill throw a gauge in the fuel system and see what I get here in a bit. The garage is full at the moment and its dropped almost 30 degrees since yesterday, don't think I can stand being out there much longer.

Hopefully have the fuel pressure checked by tomorrow evening and then I ca go from there with the AFM if nothing checks out.

Again thanks for your guys input.

[superlen]

Good looking car. It's hard not to love a red Z.

As for the AFM, I don't know if the turbo *can* work with the NA ECU or not, but I KNOW the NA AFM will work with it. My instinct is that by tweaking the wheel in the Turbo AFM one can get a Turbo AFM to act close enough to a NA AFM that the car might run, but it won't be perfect. I'm guessing that's whats been done by the PO in this case.

If you think it's fuel related get a gauge. Fuel pressure is a critical number to know when diagnosing EFI and without that number, you're hindered.

Len

[Unfairlady]

Yeah I am going to go get one tomorrow and put it in line. and the car looks really good in that picture. much better then what it actually looks. the cars got the clear coat coming off of it now. I was planning on repainting it here in a few months but I want to get it running flawlessly first.