Saturday I was playing around, and just out of curiosity I took out the JWT ecu and installed an unmodified 5 speed ecu I had recently bought to use as a spare. Actually, I wanted to see if the ecu threw any codes that would indicate it was for an automatic and not a 5 speed. Anyway, I didn't expect the car to run well at all with the 370 injectors and Z32 maf sensor.

To my surprise, not only did it run, but the combination of the Z32 injectors, Z32 maf sensor and A32 ecu worked great! It idled perfectly, with an egt of 700F (maybe 20F more than with the JWT ecu). Cruising I saw egt's maybe 50F more than with the JWT ecu. I did a WOT run up to redline in 3rd, and egt maxed out at 1400F. It did bog a little when I first went WOT at about 3000 rpm, indicating some richness (also indicated by the 1400F maximum egt). Not anything that couldn't be corrected with the SAFC, though.

This was all done without a fmu, just normal 43 psi fuel pressure, boosting up to about 10 psi.

Edit: I should have said this was done with normal 34 psi base fuel pressure, rising to a maximum 43 psi.

 

So you're the one who bought my ECU. Enjoy.

 

very interesting, nice discovery.... hmmmm

 

Thats good too know. For me to poop on. No j/k , good for some people who don't have the cash to throw out there.

 

Yes I am running my car like that but w/out the 300TT MAF. I am running it with a SFMU, but corrected low throttle to 26% @ 2500RPMs so the car drives good for now up until the ECU overrides the SAFC Low throttle settings. I may disconnect the battery to reset it or something. The car does bog from so much fuel and then boom it takes off and there goes the spikes since its cold outside.

 

I'm confused...

Are you saying that there is no need for a FMU with the stock ECU and 370cc injectors...or that having the Z32 MAF somehow tricks the stock ECU so you don't need the FMU.

I wouldn't want to test this theory without a FMU (or ECU), but its interesting.

 

The 370 cc/min injectors provide 54% more fuel than the stock 240 cc/min injectors.

The ratio of Z32 maf max airflow to A32 max airflow is about 1.49 (49% more).

I think what is happening is that the Z32 maf is giving a signal to the ecu that is 49% less than what the A32 maf would for a given flowrate. So the ecu tells the injectors to pulse at a certain duty cycle based on what it thinks is a flowrate 49% less than actual. But the 370 cc/min injectors flow 54% more fuel per pulse than the 240s would. The 49% less airflow signal is close enough to the 54% more fuel that they effectively cancel each other out in closed loop operation, and result in only minor afr lowering at WOT.

 

That could be very important information to someone who is trying to build a high HP NA car. (If that ever happens) It would effectivly increase the HP potential without running into fuel delivery issues since an FMU is not really an option.

 

That is interesting because that means you can run the z32 maf on the stock ecu! without blowing it!!!

 

Just make sure its on the non-charged side.

 

You have got to have the 370 cc/min injectors, too. Otherwise, you will be too lean.

Maybe you meant that and just didn't say it, but I don't want any readers to be confused.

 

I moved the maf back to the charged side because of driveability problems from having the maf too close to the blower inlet. I've had it there for about 3 weeks now without any maf problems. I'm going to leave it there until it blows (if ever). I'll post if it does. I carry a spare maf in my trunk, just in case.

 

Really? Interesting...

 

So, with the 370cc/min injectors and a 300zx MAF on the charge side, you do not have to run a FMU? Is this completely safe? This is VERY interesting as it would eliminate one more "factor" in fine tuning the car. Now the question is, with the S-AFC, what settings should one run in order to compensate for the leanness/richness at the given RPMs? You guys are awesome, sheesh......

 

What you're describing is like the Hacked MAF mod on the boosted 240sx...

Increase the inner diameter of the MAF tube by 50% and you can run 50% larger injectors

 

It is safe as long as you don't exceed the fuel delivery capability of the injectors. The 370 cc/min injectors can support around 350-420 bhp at 43 psi (depending on duty cycle and afr). Fine tuning the SAFC would have to be done with a wide band O2 sensor, e.g. on a dyno.

 

However, I still don't understand how the fuel is "built" as the RPMs increase. Meaning, as soon as WOT is established, the fuel pressure shoots to 43 psi and stays there to redline. However, the boost starts building at 2500RPMs and I reach full boost by 3700 RPMs at 10 psi. So I would be running WAY rich at the beginning of the pull. Now, can the S-AFC actually compensate for this and lower the duty cycle that much in the beginning to lean it out enough? This is quite interesting/weird......

 

this may be one of the best discoveries in a year.




And thanks for sharing.

 

any partial throttle problems with this method??

 

What he said. I have never seen a 300zx MAF sensor but can you port the sensor out like some people do to the maxima MAF for the Pathfinder throttle body upgrade? So could you have a ported out 300zx MAF and 555cc injectors? Or how about a Ported out and Maxima MAF and 370cc injectors?

 

EXACTLY what I was thinking.....

BTW how much HP can the 555cc injectors support? I suppose I should be able to figure this out.


edit: I figured it out. if 370cc injectors can support 420hp then 555cc injectors can support 630hp.

 

correct me if I'm wrong but, didn't hlh505 get 430hp from his stock injectors?

 

He has extra fuel coming from a nitrous wet kit.

 

yeah, but he has funny math.

anyway, how close was the maf to the blower inlet?

and would you run the na or the tt maf?

 

I didn't experience any in the short time I had the A32 ecu in. I'm going to reinstall it some time this week to do a more extensive test.

 

The fuel requirement is dictated by how much air is entering your engine, regardless of whether your car is NA or if the amount of air is augmented by being boosted. Of course, boosted people also have to worry about detonation, so we generally like the afr to be lower than NA folks. At any rate, as long as the maf sensor can measure the air flow (and the Z32 maf can measure up to 520 hp worth of air) and if the fuel injectors can supply sufficient fuel at an appropriate rate as determined by the ecu, then everything is fine. This is true whether at partial throttle or WOT, because both closed and open loop modes rely on air flow information from the maf.

So, in your example, your boost may reach maximum at 3700 rpm, but in an airflow referenced system (like what we're talking about) the maf is still measuring the amount of air regardless of how much boost you're making and the ecu is adjusting injector pulse width based on air flow. The ecu would not make you way rich just because your boost is high at low rpm. The only thing you have to worry about is whether you are rich enough at WOT to prevent detonation. The boosted run I did resulted in an egt of 1400F max, so I think the afr is sufficiently low.

 

The 555's are 50% larger than the 370's, so I guess if you could port the Z32 maf out to provide 50% more flow it would work. But 50% more air flow requires 22% larger diameter. The Z32 maf (like the A32 maf) has a 70mm diameter, 22% would make it 86mm. I don't think you can enlarge it that much.

 

At a much higher fuel pressure than 43 psi. And extra fuel from his wet kit, like spanishrice said.

 

now remember these hp figures are flywheel hp or BHP not WHP like what you get on a dyno. so assuming were all 5spds 15% drivline loss of 420 BHP = 355WHP which seems like alot of turbo guy will surpass above 10psi so alot of people wanting to do this but want more than 350whp need 550cc injectors which will support around 530WHP which not many maxs will ever see with out nitrous or 20psi

also im certain that you would need the ecu to be reprogramed for 550s and z32 maf unless you somhow increase the diameter like some people said

looks like were starting to become real backyard tunners like alot of honda guys figureing shortcuts to save money and i live for this type of thread unfortuanitly they only come every few months but you learn so much reading them

 

yup, now if one of yall would crack open the Maixma ECU and putz around and get into chipping/coding and reading Hex addresses, yall would be in business! no more cheap hacks or JWT/AFC dependence...straight OEM "standalone"

 

That would be the day.

 

Actually my comment refferred to the fact that 97- 99 cant get a jwt ecu. So the question has been asked many times whether or not you would be able to add a z32 maf with stock ecu without blowing the ecu. It looks like, by doing this, a 97 -99 supercharged vehicle would have no problems at all for a/f. The factory computer will do it all. It would be nice to take a car on the dyno that has done this just to check the a/f

 

I'm seriously thinking that the next time I dyno I'll have the stock ecu with me and do a run with the jwt ecu and then the stock for comparison. I've got it so that the ecu is easy to swap out.

 

The Z32 maf is the same physical size (and bolt hole locations) as the A32?

 

That is correct. Exactly the same externally. And an added bonus is that the sensor post is much smaller than the A32's, so less restriction to air flow:

 

Same wiring harness?

I really like the idea of no FMU...the simpler, the better.

 

Oh, you got me there. I forgot about the harness connector being different. The Z32 sensor has a 6 pin connector (vs 3 pins for the A32), so I had to splice in a Z32 harness connector. Two pins are unused, and there are two ground wires instead of the single A32 ground wire. Then there are the 5V signal and the 12V signal wires. The rumor is that if you screw up the connections you'll fry the ecu or the maf sensor.

 

You dont increase the diameter by 50%, you increase the area of the tube by 50%. Therefore increaseing the flow by 50%

 

Stephen Max: You are amazing. Can you get us the exact wiring code, (ie. which 300ZX wire goes to which on the stock harness, and which two are ground, etc). Thanks again. Awesome....

 

Also, anyone found a "hookup" on z32 MAF's? I've found them for $50 on car-parts.com.

Any z32 MAF? Does it have to be from a TT? Specific years?