13B Etc

iTrader: (2)

I'll try to report everything I can, but will surely leave something out...

1988 RX-7 N/A. Car has emissions and other unnecessaries removed and blocked-off, is used for autocross and other track events, some street driving.

Lean diagnosis based on lack of power, dyno's sniffer, and reading plugs
No codes present, timing set, initial set not jumpered, no vacuum leaks.
AFM tests fine, aux ports open properly, fed from pipe from main cat (no precats)

Most every sensor checked as per FSM, all appear to check out fine, only concerns might be the AFM's AIT sensor (1.54V) or the AIT in the dynamic chamber (3.34V). Measuring the resistances of both sensors with the engine cold checked out fine, however. At 76 F, the AFM's AIT shows 1.96Kohms and the other AIT shows 29.3Kohms, just about dead-on as per the FSM.

TPS has no dead spots I can find, pins A-B set dead-on at 1Kohm with engine warm, unplugged from harness. A-B shows 4.5K at WOT. A-C shows 3.81K at idle position and 400 ohms at WOT.

Fuel pump has had new wiring run back to it, reporting battery/alt voltage when running now, instead of 11.X. Taped a gauge to the windshield and pressure is 40 PSI during WOT pulls, 35 at idle, and 43 when the FPR is vented to atmospheric pressure.

All injectors operating correctly, as best as I can determine. Listened for the solenoids via a long screwdriver placed on the body of each injector, secondaries kicking on ~3800. Pulled all four injectors and cleaned them by pushing pressurized brake cleaner through them, pulsing the injectors open. Spray patterns aren't a perfect cone, but they aren't just dribbling/pissing either.

The funny part is (and right now I'm thinking this is key to my problem) that when I pulled the primary injectors, they were low-impedence with yellowish tops. The car had a small fire under the previous owner, and I believe he replaced either the harness or parts of it, as the primary injector connectors were low-impedence, whereas this is an '88 with an N327 ECU, high-impedence secondaries/harness and no resistor pack. Unfortunately, I couldn't find any wired-in resistors to go with his low-impedence injector swap...

I put a cleaned pair of 195500-1350s into the primaries, no dice, still feels the same, only now adjusting the variable resistor actually has impact at setting idle, whereas before it did nothing, so I was able to get my idle fairly solid again. With the number 3 (smallest) connector unplugged from the ECU, measuring from 3A to 3C, 3E, 3F, or 3H shows 576 ohms. I probably went about measuring them the wrong way, but I was trying to see if there were resistors inline to the primaries (or anywhere, for that matter).

Reading where several others have stated that running low-impedence injectors without resistors will burn out the ECU, I pulled it to inspect. I found no signs of damage on the component side, but a bit of brownish discoloration underneath the area of two or so ICs on the under/solderside. Not black or obviously burnt, but definitely different than the entire rest of both boards, so worth noting.

That's all I can think of at the moment... like I said, I'm sure there'll be things left out, so a few engine bay pictures are included. Thanks to all for any assistance, I tried to do my best to search, etc.

Also, and unrelated... why is it that nobody can get the Falken RT-615Ks in 14" around here? I've been autocrossing for three years on tires that came from ratty warehouses and wherever I can find them for cheap, but am finally having/wanting to drop some change on a decent tire that will give some grip. Was going to pursue some cheap Nissan 240 wheels in order to fit a wider tire on 15" with more tire availability, but am unsure if it's safe to put them on lug-centric, or if hub rings are needed to keep the weight off the lug studs, etc, not my area of expertise. Advice?

AGreen

iTrader: (11)

A burned out ecu will not always show burn marks. Without a lot of electronic knowledge, you'll never know if it's bad until you throw in a known good ecu.

13B Etc

iTrader: (2)

That's my next step, just wanted to post everything up to see if anyone could find something I missed, or had different ideas, etc. Of course there's so much going on inside an IC that it could pop quite easily before it gets enough juice to actually "burn" anything, just wanted to point it out as part of being thorough. Thanks for the reply.

RotaryEvolution

iTrader: (30)

what kind of AFRs at what RPM range are you getting? i'd suggest swapping the ECU first.

although i'm not fond of the Rteks for any real modified applications the 2.1 is actually an OK engine management system for the S4/5 n/a vehicles to get a little more out of the lightly modified non turbo cars, it is good for diagnosing issues and i have squeezed out 190WHP out of an S5 n/a with just a moderate streetport on a customer's car(probably could have hit the 200 mark but it is a track car so i wasn't trying to break any records although it was probably already).

13B Etc

iTrader: (2)

My dyno sheets don't have the AFRs, funny enough, so I have no clue. I just remember them pointing out to me at the time that it was going quite lean through the pulls. The engine never pings or anything, so it's not -that- lean, but like I said, the plugs definitely indicate it. All I have on the car is a narrowband, although plans are to Megasquirt it and add a wideband over the winter/off-season.

I suppose one of my main questions is as to the resistance measured in the harness looking toward the injectors, as well as "Would/should my car even be running this well if it's been running low-impedence injectors for years with no resistors?"

bumpstart

WOT 40 psi,, but 43 psi static,, either your TB doesnt open and your losing 6 inches of Hg with the restriction at the top end
-- or this pump is not keeping up -- WOT should be 43 psi !!
3 psi = 7 % of the fuel !!!!

also,, check the in cabin atmo pressure signal, 3.5- 4.5 v for sea level


PS change out that filter first !!!

PSS-- this may also be related to where you have your vacuum source for the FPR signal
make sure you have a steady true manifold vacuum signal,, and not one from the purge signal port on the TB !

13B Etc

iTrader: (2)

Atmospheric pressure sensor reads 3.8V, I'm at ~1,100 feet.

Replaced the fuel filter less than 5,000 miles or so ago. Pulled it a week or two ago and it blew fine, both ways, even.

The FPR was attached to the middle nipple on the front of the TB, but not long ago I moved it to the front-most nipple near the blocked-off cold-start injection on the middle of the intake manifold, to be sure it was seeing proper vacuum.

I didn't even think about the pressure difference, that's a very good point. I'll have to hook up a vacuum gauge to determine what pressure the FPR is truly seeing, and see what happens during a pull with the FPR vented to atmospheric, in addition to the ECU swap. Thanks for pointing this out.

RotaryEvolution

iTrader: (30)

the best spot for a good vacuum signal is on the far side of the UIM where the top 2 intake halves meet, at least i think there was a port there, at least there is one on the S5 n/a.

13B Etc

iTrader: (2)

Now that I check my notes, the 40 PSI was actually while free-revving in neutral. It was pushing 42 PSI during actual WOT runs on the road.

RotaryEvolution

iTrader: (30)

well without AFR readings its difficult to know where the problem lies, if it is strictly in the upper RPM ranges or all over the RPM spectrum(which means fuel supply issues from your pump). the main inputs for fuel from the ECU is the airflow meter, coolant temp sensor and CAS signals. any issues with the fuel system won't be easily diagnosed, you can have pressure but low volume(plugged fuel filter or weak pump) or faulty injectors or injector drivers(ECU faulty).

used ECUs aren't that expensive and that it has been driven with the low impedence injectors for years means that the drivers have likely taken a bit of abuse.

lastly, be sure you have the correct air flow meter, if someone threw a turbo AFM on the car then it will run lean through all RPM ranges because the turbo AFM has a stiffer flapper spring. N318 is the turbo and N326 is the n/a version(if memory serves).