You contributed greatly by adding Peter's solution and also that your own experience suggests knock induced fuel cut is to blame (better gas fixed your problem). Both of these give credibility to Doug's explanation. Not that Doug is not credible, but people tend to dismiss his explanations as "just defending his product, placing the blame elsewhere" And I don't blame them. Since I have never experienced the problem I can only pass on what Doug says, I can't personally verify it. Though Doug has always seemed to be honest and supportive even when competition is involved.

Not to get off topic... Doug assures me there is virtually no change in fuel delivery if all settings are at 0% when within the factory fuel cut zone (approximately 10psi at sea level, but it varies by RPM). I could measure no difference in a:f between 10psi w/PMS and 10psi stock ECU only with my wideband. If there are differences, they are small enough that they don't result in a noticable change in a:f.

I agree it is hard to explain why you didn't have the problem without the PMS. Who knows, there may be some way the PMS is making the situation worse.

I can't imagine how your a:f would be in the high 10/low 11 range with 10% fuel added at 10psi. IMO it should have been practically maxxing out the meter at 10:1, your mods are not that significant and the stock ECU will max out the meter on many cars. Was the wideband post-cat, that would explain it.

(I feel like we should start a new thread or let someone else post, or something)

Wade

 

Ryan,

If you were hitting MAX duty at 5850 RPMS then you had WAY to much fuel added!

Wade

 

Wade,
When I was discussing the problem with Peter we both agreed it was knock related issue (i had previously almost completely replaced my ignitions system and prolly unnecessarily removed a Crane HI-6 So I have no doubt that Doug was/is on the right track. Although I must admit my two calls to Doug were VERY dissappointing. Specifically (if I may digress for a minute) had the PMS throw a wacked error code followed by a totally dead car while driving in prep for a track weekend. No explanation. I reset the ECU and all was fine for a quick 15 minute drive before departure but I called Doug to get a read on the code. He said he didn't know the code and that I "just have pre-race jitters." So I trailer the car to the track and start the car and the keypad goes nuts. Cursor jumping all over the place with no indications or anything. Car is dead. Reset the ECU again and it comes back. Start car and unload it off the trailer. Saturday morning try to start the car for the first session and nothing. The PMS is totally dead. The computer is dead. So much for my pre-race jitters. it was at that point that I decided I'd had enough of the 6k fuel cut and the computer as a whole. A shame really as I liked the principle and loved the datalogging and was soemwaht familiar with it's use so was not looking forward to relearning a whole new system. Oh well such is life.

What I figured too but was never able to confirm.
Peter would never give me/us a straight answer. All very secretive.

This is what I think is exactly the case. Peter was just able to drive the car hard enough on a dyno to geta the stock ECU to see the same thing but under conditions that perhaps a car would never see either on the street or on the track

It's been a long time so perhaps my memory is off a bit. But the settings were no where near the +35% range. The car was dynoed at KD witha wideband in the O2 bung. I videotaped the Wideband readout and the entire session. I dare say if it wasn't +8% to +10% range it was no less that +6% but the +8/+10 sounds much more like were I was.

Really?
I wonder if we are the only two reading the thread?

Ryan,
It is quite possible the knock signal could be originating somewhere in the exhaust manifold or turbo's even, however, and I'm not knocking your suggestion but until you've driven the car HARD on the track for 30 minutes (lats time we talked I don't recall if you said you'd been to the track or not - and yes we have met!) it's tough to say if this fix - to non-sequential - will work. FWIW my car never experienced the fuel cut either on the street or at the dragstrip (the couple of times I've been) However on the track when ambient temps were anything above 80degF, guaranteed by the 4th lap into a session I'd start having a problem


Anyways...the more datapoints on the broad the better IMO
Crispy

 

Rikki <G>
see your PM
Crispy

 

Damn, why won't the entire post show up when I try to quote you Chris? Anyway...

That's too bad about your experience with Doug. Might have lost some future customers among you and your buddies.

When it comes to some tuners being secretive, I often interpret it as they don't really know the answer. But I'm also a very doubtful person in general, too much "wisdom" has been wrong in the past.

You may be right that the PMS itself somehow makes the problem worse (even excluding possible tuning problems, knock from higher boost, etc.) I'm no electrical whiz so I won't even make a guess on how this might happen.

About your dyno, all I can say is wow, I'm surprised!

We aren't the only two reading... at least Ryan is getting some entertainment out of it too.

I don't think the principle of the PMS is good nowadays since plug and play standalones are available, with even better ones on the horizon. The PMS has been around for 15 yrs so it's no surprise that what once might have been the very coolest thing available (back in the "chip" days) is now viewed by many as nothing more than a kludge. I'd rather use a standalone but I've spend a lot of money on the PMS and I don't want to replace it more than once. I'm anxiously waiting for the Xtreme. I've used the Power FC and it is very nice and trivial to learn and use, I'd like more support and a company supported PC interface, but I also really like the convenience of the keypad (which the Xtreme will not have). I can totally understand why you switched. I often think about buying a PFC instead of waiting for the Xtreme.

In the meantime, bargain shoppers and people like me who are holding on until the bitter end will just have to make due.

Wade

 

You have another person listening intently. I am trying to learn as much as fast as possible. By all means continue the discussion on this thread. Thanks for the input. As far as temps go my car hasn't been cutting out as much now that atmosphere temps are going up.
-says this with a shrug-

Jeff

 

Wade, Ryan

I don't think his comments were deliberate. He was very nice to me on the phone and seemed honest enough so I'm not going to pass judgement given this single interface. Who knows maybe he had a paying customer at his desk and couldn't spare the time at that moment. I have no ill will towards him.

The secretive inference was mainly as a result of my dealings with Peter - don't come into my shop I don't want you seeing my techs work on your car and when he did the chip swap when I upgraded to the pink hardware he shut the door! That cinched it for me..what's he hiding...I dunno?

This is exactly what I think it is. A "problem" that is exacerbated by the PMS. Time lag due to the extra circuitry? Time lag due to an additional processor in the loop? Who knows but I do serisously think having the PMS in the system is doing something....be it intentional or not.

Really? *sniff* he said my mods aren't that significant. *sniff* Catback, DP, hiflow main cat, IC intake, and pulley with the piddly stock injectors. I don't think +8% to +10% extra fuel to be extreme? Maybe if I had bigger injectros and a RRFPR then maybe the necessary ECU fuel addition required might not be so significant but still....

In it's heyday the PMS was state of the art although even back in the days of the Big RX-7 list the dabate raged over piggyback vs chip/standalone. Remember? In today's times the piggyback is dead IMO. It just can't do with the same degree of precision what a modern standalone can do. This is not to say it cannot generate some healthy performance numbers and be quite user firendly and understandable but that *if* a user wants comprehensive control then a standalone is really the only way to go. I did afterall buy a PMS whe they were avialable but like Ryan said it's just getting old. We have faster and "better" options available now. I look to the case of Rick Potter's One Lap car. Had all the PFS goodies but when the single turbo went in the PMS was yanked and a TECII was installed

Nothing wrong with that at all. Hell half my car is assembled with used and second hand cast offs from people who have upgraded. I think my roll bar and PFC are the only two new parts I bought at full retail price for my car. I am a tightwad too

Crispy

 

Chris,

Not to disagree with your fundamental idea that the PMS makes the problem worse, since it certainly appears to be true for whatever reason... but I'm 90% sure the knock sensor doesn't actually run "through" the PMS. I think whatever is causing it to be more "active" is likely a side effect of fuel or timing changes. There could be some kind of noise introduced in the PMS pass thru harness though, as I said before I'm no electrical whiz so anyone's guess is as good as mine. It may be that Doug made some change to the fuel cut defense and it ended up being less effective than in the older models.

No offense meant about the significance of your mods. It's just that I've tested a few cars with your mods or more (such as midpipe) and the a:f has been from 11.5-10 (depending on mods) with 10psi and the stock ECU. You've probably seen the stuff on my webpage. Take my car for instance, all the bolt on mods, no cats, and 14-15psi of boost and I only add 4%.

At 10psi I don't add anything, and 10% fuel is a lot more than you'd think, consider you are adding twice the extra fuel that I am, my car has more mods and runs 5 psi more boost. That's a lot of fuel!

Anyway, I'm just surprised, that's all, I'm not suggesting your information is wrong, after all there are slight variations among like cars. It might even make more sense to me if I saw the graph of a:f by RPM, after all the a:f is VERY lean at lower RPMs, maybe that's where you saw mid 11's... and high 10's in higher RPMs.

About the PMS, yeah you are pretty much echoing my comments.

It really boils down to the fact that you just cant change some things about the stock ECU. The stock ECU has a fuel cut that is apparently also triggered by knock that creates a problem for a FCD... the stock ECU is built around the 550:850 injector ratio, so upgrading injectors is difficult... the stock ECU expects air from the ACV/airpump for closed loop to work properly and if that air is gone the PMS can't correct it... etc. This is why a standalone can work better. I certainly would never go with a TECII though, well, unless it was given to me and installed for me, that is.

I played with standalone mode with the PMS for awhile, and I had very positive thoughts at first. But then it came down to the fact that it needed a few more maps (water and air temp comps) and staging to really be effective. Those probably would have been added if someone had played with standalone a year earlier, but once I was playing with it, EFI was deep into development of newer projects and couldn't dedicate the time/money to it. Particularly when only one person that I know of had shown any interest in this functionality.

I like the PFC but I worry about being stuck out in the cold if it would ever go bad. The likelihood for updates, enhancements, and fixes seems remote, too. (praying for the Xtreme to be finished...)

Wade

 

Wade:

Spent some time on your website. Thank you. Could I derive from your argument that from the feedback your are getting from the added amount of fuel that one could do with the stock ecu if say the boost was well controlled to not exceed 10psi?

You claim to add only 4% fuel at 15psi boost so can I deduce that installing a midpipe or hi-flo will improve hp without necessarily having to buy an ecu and also inherit these wot cuouts?

will all these folks with pfc and other types of ecu, it should be well extablished with the standard bolt on mods what the injector duties and fuel supplement are need if stock injectors, pump and boost is normal.

right now i have intake, downpipe and hks super drager (yeah the brand new one) but have heard the testimonies of new mid-pipe owners on the immediate effect on performance. yet, constantly i hear about blowing seals...if i can validate that injectors are clean and boost is rigidly controlled to <= 12 psi, will an supplemental or standalone ecu be neccessary?

thanks

 

Guys,

I just though I would put my 2 cents in. I have had my PMS for about 3 years and never had a problem with it. The fuel cut off is at about 8.5k to 9K. I think I have hit it once. I do have a J&S and it never shows knock. Good luck.

Chris

 

Sorry guys, been away from a computer for the past week!

Ryan:

My unit controls boost pretty well but it isn't perfect. I usually do some adjustments with the PMS and valves and can get the boost control as good as possible for my setup. I had a lot of creep before working the wg but that is not computer dependent.

You will need to use a wideband to be sure about your tuning. I don't use standalone anymore and I add 4% fuel at 15psi, subtract about 5 degrees of timing.

cover8:

Yes, normally the stock ECU would be okay with a lot of mods. Every car is different but I haven't found one yet that doesn't run overly rich at 10psi even with mods, mine has lots of mods and runs sufficiently rich at 10psi. If you keep boost at or below 10psi you shouldn't really have fuel issues, however there may be a point where you want to reduce timing a bit or raise the boost level, either of which would really require some sort of aftermarket computer.

I think that less exhaust restriction results in extra power from a somewhat leaner mixture with no other tuning changes as well as the reduced exhaust restrictions. Adding an ECU and adding fuel back to the factory 10:1 a:f ratio would actually reduce power compared to using the stock ECU.

You are right, with all the people with programmables it should be well known what millisecond values are needed for different levels of modifications. This information is already known and available for people who want to do a little digging on the internet or run a few relatively simple tests with their cars.

For example it should be easy to prove that the stock ECU and Power FC have very similar fuel maps at around 10psi of boost and both run reasonable a:f ratios for many cars (I think the Power FC map is actually leaner than stock). However most people aren't interested in this info, millisecond comparing, wideband testing, etc. I can provide all this info if enough people want it and are willing to wait a little while for me to measure and compare the data.

If you can stay below the fuel cut level with the stock ECU then no, I don't think you will need any type of fuel supplement. However it is best to spend a small amount of money for a wideband test as cheap insurance.

Wade

 

so this is common with the PFS purple unit? I am looknig into a car w/ that unit and i would liek to know abotu any other problems with it.

 

Hmmm. since I started this thread and asked the question, seems like there is no real definite answer, other than going with another type of EMS.
Ron A.

 

It seems to me there is a definite answer. Get the car tuned properly. If the problem still exists, doing somethign to reduce the sensitivity of the knock sensor seems to be working as a fix for the fuel cut.

Wade

 

Bring back a dead thread. Any update on this problem from two years ago? I'm about to get a pmc for my Auto and would like to Know. I believe it has the pink update. People in the past have said the the pink update is the one that gives the least problems, what you guys said seem to say other wise.

 

The solution for me was to sell the PMC and use a Power FC ;-)
FWIW PFS's "solution" was to remount the knock sensor to a less sensitive location like up on the alternator bracket. Well Duh! If knock is causing the apparent problem well then lets just make the sensor less sensitive. From an engineering perspective this is total crap but apparently it works... so they say.
I don't know, nor do I care...the switch from the PMC to the PFC was one to the best decisions I've ever made.
Regards,
Crispy

 

The answer is to relocate the knock sensor.

It works. Peter Farrell moved mine two years ago and the problem was solved.

No fuel cut problems of any sort since and the car runs like a bandit & I have been drag racing it for those two years too.

The PMS is a damn good unit so long as you are staying with twins. Really cost effective with current low prices for the unit too. It's all you need.

 

Hello to all... first time in forum and wondering if someone could help...

I'm having the same problem, but it begins after the single turbo conversion....I did'nt have any problems when twin (rather than the primary turbo shaft been damage 4 times...that's why I changed to single)

About the topic... I was suspecting about the PFS retainin the stock ECU error codes, but now that I read all this, I'm not sure. My fuel cut begins at 3000 rpm. The engine diagnostic is indicating metering pump, fuel thermosensor, fuel pressure regulator SV and relief SV error codes. However, when I phisically test them, they are ok (except the metering pump...have not chk it but I don't think it has something to do w/it).

I restart the ECU (ground/brake) and it runs fine until some minutes later depending of the TPS position during the ride (if the ride is mostly WOT, the fuel cut nevers come back, but if I let it idle 2 or 3 mins, the **** is back. My car is an RX7 R2 1994 US spec...someone told me about my car beign a CA spec is causing the problem but don't know excactly why...

could my problem be the same as yours? or is the error codes the problem...

does anyone know why the diagnostig is triggering the selenoid codes if they seem to be ok?

BTW ... where is the knock sensor located?

ANy help.... WELCOME!!!

Jose

thx!