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

[superlen]

I just saw you posted on the guage. cool.

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?

Poor fuel delivery could explain it and the fact it's been sitting supports that. However, it's not the only thing.The AFM responds to load not rpm. Of course they are closely related, but when you're loading up the engine the AFM flap is near full swing (even at a lowly 1500rpms). This full swing position is where I think the two AFMs curve will depart from each other. Racing the engine in neutral will of course move the flap, but 4k rpm in neutral might not have the same fuel requirement as trying to accelerate on the road at 1500rpms.

Think about this:

1. The AFM for a NA only has to respond to X amount of airflow. say 180cfm max.

2. The Turbo AFM has to respond to all that extra air, maybe 250cfm. X+70.

3. If volts out/cfm between the two AFMS are the same, then the ECU won't care & life is good.

4. However, I'm 99% certain that Bosch had to change the full scale volts out on the Turbo AFM, or the extra airflow would bottom out the NA AFM. On my NA under full load, there is hardly ANY flap movement left on the AFM. If I added 50% more air flowing through the engine, the flap would stop at full scale before the engine reached it's peak and it would for sure lean out at the top end. That's what leads me to believe that changed the scale on the TAFM.

5. Assuming that to be true, then the spring force on your TAFM is stiffer, which gives you a lower volts/cfm reading than the NAFM at any given cfm. It's even worse at higher flows because they designed it to be logarithmic. The NA ECU you have is metering LESS fuel at every point along the load curve. It's worse at the higher loads (usually associated with higher RPMS) & has probably been accounted for near idle by adjusting the idle air bypass screw so it doesn't show up at light loads.

Anyhow, that's what I think, but I'm not real swift on these Z ecus and such.

Len

[superlen]

BTW,

I was in Fort Wayne a few weeks back it was -12 when I was there. Your weather sucks. I'm fighting weather here in Arkansas too. I'm trying to get a flow bench finished up to do some testing and it's another blizzard going on. It was 66 yesterday, 34 now with ice/sleet/snow. Like you said, it makes it hard to stay out in it. My shop is heated, but I still would rather have a nice spring day to work in.

Len

[Unfairlady]

Yeah that makes sense with the AFM, but I am wondering if that would make it get worse and worse.? and I feel like with the turbo AFM wouldn't it want to over fuel. not lean out? I don't understand any of this datsun stuff so I am just going to roll with what you said ha your definitely more on it then me. I'll just tell the fuel pressure and then I'll go from there. shouldn't take too long to do that anyways.

(And yeah haha, it was 68 here yesterday (I even road the motorcycle) and it hasnt broken 36 degrees today and it was supposed to snow sometime today. And I was trying to fix the starter on my brothers mustang in my nice warm garage and of course when you go to fix something for someone they immediately ask you to "fix this and fix that" next thing I know I am putting a windage tray in and figuring out a mounting solution for his catch can.. now my garage has been taken over by a mustang...)

[Zed Head]

superlens logic looks right on the need to rescale the vane movement for a wider range of air flow. It may be that instead of, or in addition to, a stiffer spring, they also went to a bigger bore. Less vane movement for more CFM. On people using turbo AFM's in NA cars, I think that what they're doing is using the turbo AFM body and swapping in the NA AFM "guts" or circuit board. On the theory that the AFM is an air flow restriction. There are few threads out there on swapping AFM internals. The end result is probably a mixed up AFM, with different vane action on NA ECU electronics.

One more wrinkle - the turbo system, ECU and AFM, is designed for 265 cc injectors, the NA for 188 cc. Three variables; ECU, AFM and injectors. Just looks messy to deal with and the odds of success are low.

[Unfairlady]

Okay but with the NA injectors and the NA harness and ECM if I just got a AFM from a NA car (a31-060 001). then I wouldn't have to even open up a AFM or anything just slap it on and it'd work (lazy mans way out). correct? then I won't need to even do some fancy calibrating or anything. That's if the fuel system is fine.

[superlen]

Unfair,

on the Mustang. It's the same way here, you work on everyone else's first then yours....at midnight...with the windows blacked out so they don't know you're in there.

YES on the stock NA ECU, stock NA injectors, & stock NA AFM. If all three of those match & nothing else is wrong of course, it should run your L28 engine.

Zed,

I had forgot that the turbo AFM might be a bigger bore. (I don't know what they are, but the NA AFM bore where it connects to the throttle body boot is definitely 2.75" - I just turned an adapter on the lathe yesterday). I understand why people try to swap them around, but I'm not a believer of needing a bigger TB or AFM unless you have done some serious head work on our Z's. The main limitation is the head, not the intake system.... I think.

This was the adapter I was making yesterday to mount this AFM on a flowbench to pull some numbers.

BTW, I am going tomorrow or Tuesday to work a deal on maybe 12-15 AFMs. Hopefully some will be turbo. If they are, I can do a good apples to oranges comparison for us.

Len

Edited March 16, 2014 by superlen

[Unfairlady]

Sounds good to me! keep us posted on that. Oh and I went ahead and just grabbed a ruler (crude way to measure it I know). But here you go. its bigger then 2.75" at least but not by much.

[superlen]

It's definitely bigger. Hopefully tomorrow there will be a turbo AFM in that pile & I can give you some feedback between the two.

Len

[EuroDat]

On people using turbo AFM's in NA cars, I think that what they're doing is using the turbo AFM body and swapping in the NA AFM "guts" or circuit board. On the theory that the AFM is an air flow restriction. There are few threads out there on swapping AFM internals. The end result is probably a mixed up AFM, with different vane action on NA ECU electronics.

I didn't realise nissan made the turbo AFM with a A31-624 part nr. I thought they started at A31-630. Nice of them to throw one somewhere in between all the NA units.

Some people go with a Toyota Cresseda AFM and transplant the 280Z NA electronics onto it to get the bigger AFM. I don't know your AFM cna be calibrated for the NA.

Interesting subject...

Chas

[Unfairlady]

Can't find my fuel pressure regulator with a gauge, which is what I was going to use last night to see if I had adequate pressure. Got so frustrated I just went an ordered a cheap one. Not sure when it will be in but when it is I'll get back to this thread.

Also if you know anyone that would like to trade my turbo AFM (a31-625 000) for a NA (a11-600 000 specifically) get ahold of me.

[EuroDat]

Can't find my fuel pressure regulator with a gauge, which is what I was going to use last night to see if I had adequate pressure. Got so frustrated I just went an ordered a cheap one. Not sure when it will be in but when it is I'll get back to this thread.

Im not sure what you mean here, but you only need a pressure gauge that can go upto 60psi and a T-barb to tie in between the fuel filter and fuel rail.

The FPR you have is the later version which has one inlet and one return to tank. The early version has two inlets and one return to tank. None came with a gauge to measure pressure.

Motorsport! Fuel Pressure Regulator, 78-83 Z/ZX - The Z Store! Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

Chas

[superlen]

Chas is right. Your FPR is off the ZX but it will work fine as it regulates to the same 36PSI the Z does. One thing to watch for is that the fuel rail under pressure can blow the hose off the FPR barb if not tight & the FPR is mounted soild. The early Z had opposing barbs so this was less likely with all the short hoses connecting it. I've never seen this happen & I would think that if it was so loose that it could occur you would notice the massive fuel leak before hand, but nevertheless I've seen it mentioned before when people are running a ZX FPR in place of the Z.

Also if you know anyone that would like to trade my turbo AFM (a31-625 000) for a NA (a11-600 000 specifically) get ahold of me.

????? I offered to do that earlier in this thread with my first post. I have some Turbo AFMs already coming to me now, but I still have several NA afms and if it helps you out I'll swap one with you. Just PM me.

Len