Is a PFC better for a stock application? If so, why?

I have a largely (other than a boost controller and a downpipe) stock 94 rx7. I don't plan on modding it further, as I put my money in to racing at the moment (rotax karts). It is my summer daily driver and I have been happy with it.

I bought a PFC recently because I was troubleshooting something with my stock ECU. I fixed the problem, but actually started using the stock ECU again because it idled better (I let the PFC learn three times but it still didn't like it) and my AC didn't work on settings #3 and 4. Are there any reliability reasons why I wouldn't keep the stock ECU?

Thanks,
David

 

the PFC requires 4 wires to be removed from the harness or the idle will fluctatue.

the PFC does have the benefit of adjusting boost on it's own without need for a boost controller, adjustable RPM and boost cut levels, OMP enrichment(2 stroke adapter?), adjustable fan turn on temps and last but not least - fuel enrichment to compensate for any weaknesses in the fuel system your car may have developed over the years.

you do need a datalogit to adjust the fan turn on temp, the OMP adjustments and it makes life a hell of alot easier for tuning fuel and timing.

unless you really want the money back from the unit i'd keep it and run it even on a relatively stock car.

 

karack you are my favorite member on this forum

 

My idle didn't oscillate, it just...died. It seemed like it wouldn't idle up when you added load to the engine. However, even with no load it would die at stop signs, though not as fast as with the AC. I checked to see if the pins were broken off of the PFC when I got it, and I believe they were. I thought that the idle was a misbehaving Idle Air Control Valve, but it worked great with the stock ECU.

I did a full reset several times and then let the PFC learn the idle. However, I always had to restart it a few times because it would never idle the full 30 minutes.

Any thoughts on this?

 

probably has a map loaded off it from a different vehicle since you mentioned broken pins(some shops have been known for yanking them out of the ECU versus removing the pins from the engine wiring harness).

if you have a PFC commander do the initialization procedure(loads default stock FD3S maps back into the ECU) and see if that cures the issue. remember that these units will not reset the maps simply by disconnecting the battery.

if you did initialize it properly then you could have a faulty PFC.

pretty soon i might have an ego complex.

 

On a stock car, it's worth it just for a real water temperature gauge and the ability to monitor air intake temperatures.

Jack

 

Do you need an pfc for a relatively stock car? nope not at all. In fact if I had to do it all over again id port the wastegate, get all the boltons, boost controller (set at 10psi), a miata thermoswitch, A.I. and call it a day. Thats it no other gauges, nor mods, just a simple reliable car that doesnt flood easily, over heat, over boost, nor run lean.

Sut since you have it just keep it and tune it(unless you really dont feel like figuring out your AC issue). As its really nice to use it for diagnostic and monitoring purposes.

When I first got my pfc I had an idling issue as well. My problem was it kept hunting between 800-1100 rpms and it drove me nuts. Mine was a simple fix: my O^2 sensor needed to be turned off.

 

Here is a thread discussing this same question from 2 weeks ago.....

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/tuning-daily-driver-974342/


John

 

gentlemen, what exactly is flooding easily?

sometimes when I drive my car with base map on pfc, the car will die at low revs or while driving in traffic. this will only happen when I push the clutch pedal in. is that flooding? if so, how do you prevent it? besides getting off my *** and paying for a tuner, that is.

all I did was go through the usual learning process and it runs perfectly other than that

 

sounds like the base idle settings for the throttle body are too low or you possibly could have a vacuum leak after the throttle body. could be the tune is severely rich as well but without a wideband and some minor fuelling adjustments it's hard to say.

 

Check your clutch switch. my car used to idle like crap and die when the clutch was pressed down. My clutch switch spring has rusted down and wouldnt pop up. I think the clutch switch tells the Ecu if the clutch is engaged. After i fixed it, it runs perfect now.

Read this thread.

https://www.rx7club.com/3rd-gen-archives-73/cheap-bastard-fix-clutch-switch-495391/

 

itll do this maybe once or twice a day of driving, and sometimes not at all. would letting the ecu re-learn the car as I initially installed it help?

 

Sorry for jacking the thread but my question is along a parallel line of thought . My car will have a straight through exhaust , and intake , I'm also planning on getting a power FC to help with all the extra boost the engine should be providing at this point . should I buy a manual boost controler to help regulate boost creep , or will the power FC's boost regulator be trust worthy enough to keep my boost from creeping into the danger zone ?


apart from boltons like a downpipe , and exhaust and intake the car will be stock .

 

Flooding is when gas soaks the sparks plugs to the point that you can't start the car. The more attempts to start the car the worse off you are. The fix is either to wait until they dry off(you'll be waiting a long time) or take them out and dry them.

 

You are confusing boost creep and boost spike. A good boost controller can control boost spike however even the best boost controllers can not control boost creep since the wastegate is wide open. A full exhaust like you mention can cause boost creep. Especially with a high flow cat or midpipe.

Properly setup the power FC boost control can be used. Search for a thread by arghx he explains the in's and out's of the PFC boost control logic.



John

 

As I indirectly said in my first post: you can run the stock ecu on a car with all the boltons (CAI, IC, DP, MP, EXHAUST) as long as you can maintain a rock solid stock boost level (10 psi). Now you maintain a rock solid level by getting a boost controller and porting the wastegate. The porting of the wastegate should be done on a case by case basis because not all cars experience boost creep.

 

I had planned to port my wastefgate is there any ill effects from porting it ? I mean the engine will be outside of the car already and it will be alot easier to do it now then put it in then realize oh my boost is dooing the creeP! then have it be alot more difficult , and I dont plan on running stock 10 psi . but what I'm getting at is what should be done in order to keep boost creep from making my engine go cablewie will the PFC and ported wastegate be enough/ or would I also need a manual boost controller ? not going electric since no extra cash atm.

 

No Ill effects from porting the wastegate other than over porting past the flap. But one would have to be asleep to do that. You can control the boost via the power fc (IIRC you have to purchase the option from apexi) so no need for a manual controller.

The golden rule is always to have enough fuel for whatever boost your engine sees (this statement includes creep). If you stay below 12 psi a TUNED power fc is adequate. For any higher levels you should start looking at upgrading injectors and the fuel pump.

 

I was planning on 12 psi , with the occasional 13psi .. when needed . IE auto-x weekend or .. the occasional snotty prelude owner that says its faster then an rx7 ..

 

The pfc has some good things it can add to even a stock car. Having said that if I bought another stock car and had no interest in modding it I would likely keep the stock ecu.

Since you have a pfc I'm not sure what I would do. Keep it, and get the car tuned so you can squeeze out a few HP and enable some of the functions the pfc has or just sell it??

 

I have a semi stock car and I'm installing my PFC tomorrow I'm so excited :-)

 

I had a PFC in a totally stock car. My only mods were downpipe and FC thermoswitch. I would never got back to stock ECU.

The car ran smoother, lost the 3k hesitation and got better gas mileage. Plus I had boost control and could monitor things with the Commander.

 

I had somewhat of a similiar problem with my 93 fd. Has upgraded ic, dp, exhaust and when I installed my pfc it was having a very bad idle issue where it was almost dying, and hunting badly. I reset it many times with no luck. Looked around on the forum and replaced the whole throttle body along with metal gasket and problem was somewhat fixed but still hunting. Then searched some more and found to adjust with the idle values a few hundred rpm in the pfc programmer. Also stock tb was pretty dirty so I cleaned the tb I picked up very good and now Im having no issues at all, idles perfect at 900. Hope this helps