I was just woundering becuase I'm considering of purchasing the Power FC. I would like to know what problems arise from installing the unit. Im plaining on using my car daily, through trafic and so on. Will the unit interfer with any of the stock accessory. Also do i need the Commander to install, meaning, can I get the unit and just plug it in without programing it. Thanks.

 

It's best to have the commander.

There are no downsides to running the PFC compared to the stock ECU - only upsides.

 

The only problem is sometimes your AC will not work and also the idle hunting issue.

But there are fixes...and there are more benefits than downsides

 

The A/C may or may not be flaky. As far as the idle hunting issue goes, it's not an inherent problem with the PFC, just something that occurs on some cars.

Get the Commander.

 

I had the idle hunt, but fixed it. My a/c blows cold as ever. No downsides that I can think of.

 

The A/C intermittant issue is caused because of incompatibility with the PFC and early 93 engine wiring harnesses. The new engine wiring harness eliminates the intermittant issue.

Idle hunting is more of an issue of adjusting your idle on the TB correctly, and having the proper settings in the pfc for injectors.

For hard core tuning, there is no substitute for adding the datalogit software and wide band. Progamming by mail will only get you so far. Most pre-delivered maps are very rich and very conservative with timing - they're safe, but there is usually considerable power that can be gained with proper tuning. DO NOT DO IT YOURSELF until you have educated yourself on proper tuning, and use a dyno. If you don't have the time, inclination, or access to the proper equipment, pay someone to do it right. The cost of tuning (~$400) is well worth it if you don't have the ability to do it yourself. Reputable tuners are Jason (rx7stroe) and Steve Kan (Gotham) for the PFC, KD Rotary and RP.

Beast

 

No it's not. I know many people with 94s that have A/C problems and my 95 does. Meanwhile my mechanic's 93 car works perfectly.

The problem is that the voltage tolerances for the PFC are stricter than the stock ecu for some reason. It's completely random whether the A/C will be flaky or not, it has nothing to do with year.

 

Hmmm. Maybe I should clarify. The reports I've seen, and my own experience, showed that the newer (as in currently being manufactured) engine harness fixes the problem. I have a 93, and the intermittant problem was resolved when I replaced my engine harness with the most current harness. I participated in a thread on this forum and on the big list where others experienced the same thing (it was about a year ago). I think the issue affects cars with original harnesses. Are you running your original harness? Can you find out if your mechanic replaced his?

The part number on the harness has gone through several alphabetical number increases (from a to b to c and so forth). I think during the production run of 96-99's in Japan they upgraded that harness and it's backwards compatible.....

Of course, I have nothing from Mazda stating this - only my own experience. I know you've been around a long time, Ryan, and I'm fine with you debunking this theory.

Beast

EDIT - it could also relate to the fact that old harnesses get pretty heat baked, and I believe that baking of the metal wiring slowing decreases it's ability to conduct (increases resistance). It may have nothing to do with any upgrades to the harness per se - it's just that the new harness wiring hasn't gone through that heat cycling that the old harness has gone through, and after several years of use, the intermittant problem could return. The challenge is I won't know for another 10 years....

 

Well, actually your theory regarding a newer harness (instead of a "newer" harness) may certainly have merit. I believe my mechanic still has his original harness but that doesn't necessarily debunk the theory.

I am still using my original 77k mile harness. As far as my A/C, it still works on all four settings, but it cycles. It will work for a couple of minutes or so and then cut out for a minute and then come back on, and so forth. Odd.

 

Just to let you know, that 'cycling' is exactly what I experienced, and upon getting a new harness - voila, it disappeared.

If you are a factory sponsored Mazdacomp racer the harness costs are dramatically reduced, btw. Unfortunately I learned that the hard way - I bought my second rebuild components right before my sponsorship came through.

 

Yeah, I'm a member, but I have too many other things to spend money on right now to get the car more reliable/fun for the track -- dual oil cooler setup, race seat + harness, larger wheels + brakes.

Also, to be honest, I don't know how much longer my motor is going to last. It's running ok but with 77k miles on it, who knows. It would certainly be much easier to install a new harness at that time.

 

AT 77K you should be able to hear the clock ticking....that would be the right time to do the harness. I guess you just live with it. Fortunately the weather in San Lorenzo is pretty temperate. Good luck.

Beast

 

Anyone else have exhaust popping during decelleration?

 

I get some light popping under certain throttle openings during deceleration.

 

Tyler is correct, you are sort of correct too. I have a 94, tyler has a 95, both our cars have AC issues with the PFC but work fine with the stock unit.

On my car it worked on 1,2,4 and failed on 3. After about 1 year, it stopped working on 2,3,4.

My mechanic (Rick at rx7fashion) took my car in for several hours trying to determine why the PFC failed with the AC. He grounded the AC relay and found it worked perfect on all positions when he did that.
He found the voltage was fine in the harness and fine until he got to the switch. I wish I could remember everything he said, so I'll do my best to say this right. The PFC and the stock unit have different tolerances for the voltage to run the A/C. The tolerance in the pfc is very, very precise. Meaning if you have anything worn even slightly your ac is going to stop working. The stock units tolerances are much higher so you can have some wear.


At the time he could not check the voltage in the switch as I did not want my dash taken apart. So I ordered a new AC Switch which just arrived yesterday. I will install on my car and see what happens.

My prediction is that the new switch will make it work on 1, 2, and 4. I believe 3 still will not work, but its just a guess. According to rick, if my switch does not fix it, then its a resistor or the ground somewhere behind the glove box.

I get the feeling the problem is caused by many things. For some of us it could be a switch, others it could be a bad ground or it could even be the harness.

Oh yea, I tried the ECU by-pass and it made no difference in my case. But when I plug the stock ECU in it blows cold air.


later.

 

I had that problem and it went away after I installed the water injection. It turned out in my case that it NEVER happen when my intake temps were low, only when the intake temps were heatsoaked.

 

What are your fuel cut recovery settings? If they're too high you'll be dumping a bit of fuel under decel, but they'd have to be fairly high.

I have no popping, but I used to. I've done quite a bit of tuning on my n/a areas, especially in the high rpm ranges. That made it go away.

Zero - let us know how it goes with the new switch. I hate trying to chase electrical issues. It can drive you nuts.

 

BTW,

Kinda funny story. I called MazdaRippoff, I mean mazda recycling they wanted $100 + 15.00 shipping for a used switch and hung up on me when I asked how many miles were on it.

I called Mazdaformance and got a new one for $62.00 shipped. Thanks Mazdaformance!!!

BTW, there is only 1 switch left in the country, it may have been discontinued or be very hard to get, if anyone needs one I'd consider buying it ASAP.

 

Ah, Zero, you triggered a thought - there is a setting to in the PFC via the datalogit that dumps timing when your intake temps and/or water temps get up past a certain point. Retarding timing = anti-lag (very limited) = decel popping. However, the default settings are pretty high. You'd need intake temps of 70 C in order to hit the first setting (retard one degree) and 80 C (retard 3 degrees). That's not much, but maybe roadsterdoc has different settings?

 

my intake temps in stop and go traffic on a very hot day have reached as high as 189F.

 

On my lunch break I decided to hook up the new AC Switch. It was easy since I only use one of my DIN spaces. I unplugged the current ac switch and plugged the new one in the harness. Same problem.

I'm taking my car back to Rick on saturday he is going to finish his electrical trouble shooting.

Its appearing now that the switch is out of the way, the harness where it connects to the switch is dropping the voltage, but thats just a guess.

 

From what I've read and researched, the A/C problem is caused by the thermoswitch behind the glove box. Sometimes you can fix it by just wiggling the harness that connects to it. Sometimes you have to clean the switch. You can check the switch with an ohmmeter. It should read 0. If not, try flexing the connectors a bit, tapping it, etc. The PFC is just more sensitive to the small voltages generated by dirty switch contacts (senses 2.5 volts rather than the stock 3.5 as I recall).

Get the PFC. It will make your vehicle a different car - the way it should have been at the start! Proper idle, smooth power transition vs throttle position. Easy to adjust re mods. The Commander can read out many parameters, so you may not need to add extra gauges.

It's the best money I spent on mine!!

 

ok, here is the deal. when my mechanic plugged my new switch in, the AC worked on all 4 positions. I guess when I tried it on friday I did not have it connected all the way.

when I plug the stock ecu with the original switch it works fine, but only the new switch will work with the power FC. It appears that the switch was worn enough to cause a voltage drop that was too severe for the power FC but still within spec of the stock ECU.

If I have any more problems or if the ac quits working again I will post, but I am pretty sure its fixed now, yea!!!