ronarndt

Has anyone found a *permanent* fix for the wot cutout. I have read posts from others who power down and reset the computer, and have found this to work for a while, but the recurring problem is annoying, especially since it is unpredictable. If it happens when you are counting on having full power to make a short-sight-vision pass on a two lane road, you can be sol and have to make a full braking, embarrasing bailout back to the right lane. Any suggestions- other than ditching the piggyback setup?

silver93

i've got a pmc as well, but i'm not sure what you are referring to -
what exactly is happening?
btw, where is veil, nc?

Sidestick

iTrader: (1)

Guess you're one of the lucky ones On SOME FDs the fuel cut activates unexpectedly in the higher rpm range, around 5-6k rpm. The fault can be cleared by switching the ignition off then back on.

ronarndt

I've found this to work when the fuel cut happens, but what I would like to do is find some way that prevents the fuel cut from happening in the first place. There seems to be no pattern to when it will happen next, although it usually is in third gear, where the max boost lasts long enough to activate the cut off. Much of my driving is on rural two lane road with a relatively short distance to pass slower drivers. Losing half of your expected power as you are passing a car under these conditions is a royal PIA.
Silver93- Vale is about 15 miles sout of Hickory. Out in the middle of nowhere, but really awesome roads for a good handling FD.

silver93

oh cool - yeah, i'm not to far from hickory here in w-s.
been up around there before, and yeah, great roads!
good luck with the problem -

finky

iTrader: (2)

I put up a thread probably a month ago I thought my second turbo was not coming on line (newbie w/ tt) What you are saying sounds exactly like my problem. If you look back at the thread (I think it was "installed pfs computer and now 2nd turbo only comes online some of the time") Wade responded and he seemed to know his stuff. Since it is snowy here I am not driving the car much, but my problem still exists. Hopefully we can find a resolution.

It rarely happens from a stand still when accelerating fast. It mostly happens like when you said in third gear trying to pass someone

ronarndt

Finky- I will probably spring for the PFS software package for the PMC to see what is going on. I'm making the assumption that the max boost cutout is causing the problem, but have not done any datalogging to monitor boost, fuel injector cyle, timing, etc. If I find out anything which might help, I'll let you know.
Ron A.

the_saint

Reviving this thread

Any other suggestions? Is this a grounding problem? software problem?

I had this happen twice yesterday in third gear, WOT, and then it went away, but both times it felt like running into a wall. The boost gauge didn't show any creep, and I didn't think it was overboost cutoff.

What is the danger of having this happen (other than being unable to finish/complete a pass). Is there risk of detonation with this?

thesaint

WhiteRXseven

Low and behold..

I am not the only one with this problem..

Last year I bought 2 purple boxes from PF.
I bought one used and New from Peter Farrell.
and BOTH at WOT would hit fuel cut.
At WOT it would build build going going and then bog,
then build back up then bog, build back up and bog..
until you let off the gas...

Needless to say I returned both Piggy back PMS's.
Peter Farrell try to say it was a bad map sensor..
So he changed it and IT still did the same thing.
Other than that. PETER FARRELL basically said " some
work and some dont" he didn't even know.

For some odd reason SOME RX7's won't work with the EFI(PF PMS) system, IT won't disable fuel cut off.
If anyone know why ? or how to remedy it LET ME KNOW.

Currently I am still on STOCK ECU..
and planning to go ith reprogrammed ECU like M2 or Pettite and RE Amemiya or P F C...

There is one bright side.. about it .. :
IT prevents you from blowing your car up...

silver93

You know, I used to have the same problem you are talking about. at WOT, go, go, go then BAM! big cut, then build a bit more and BAM! cut!

anyway, this was happening when i first installed the unit. I have a 93 model, and was using an old gold computer (still am, actually).

anyway, i was pretty unsure about what i was doing to start with. So, i installed the unit, with base maps set in from the previous owner with a similar setup. Anyway, the car ran like **** for the first day. LOTS of backfiring, just drove like ****. after about a day of driving in the parking lot it got a bit better. then i started screwing with it, until it ran pretty good, except for the cut. several people told me i was running lean, etc...

long story short. i am now at the point with the unit where the car runs great and has no problems. I am running 14psi, with cold air, IC, DP, CB and low to mid 11s on the wideband. no fuel cut, no hesitation anywhere.

My personal thoughts:
1. do not make adjustments with the car running. even though they say you can, i personally think it screws things up.
2. if the PMC is in the car and its running like ****, unplug the pms, set your boost to 10psi, reset the ECU, and run the car for a day with the stock ECU only. Then, plug the PMC back in, set all the PT settings to zero, and make your adjustments to the max boost table.
USE A WIDEBAND! You do not need a lot of fuel added in, and will probably take fuel out at idle and low PT settings. Check wade's site out for TONS of good info on this unit, as he is a PMC master.
3. When i was hitting that "fuel cut" i was running SO damn rich , its not funny. I think back then i had added like 32% fuel! ha! you should have seen how black my exhaust was! after wideband, i'm down to like +8% (i think, can;t recall, maybe +10).

anyway, try all that, check out wade's site, send him an email - PM me if you want, but it is a good unit, especially for the price.

Wade

iTrader: (1)

To those of you who have consistent fuel cut problems... since it appears the PMS isn't removing the stock fuel cut properly, I wonder if using a FCD before the PMS would fix the problem? It should, I would think. I have a FCD (not installed) and a PMS but I never get this fuel cut problem. I wish someone nearby me had this problem so we could try to find a fix.

Wade

bbeavers

I have this problem intermittently with my purple unit. It is frustrating to say thhe least. Does EFI have an opinion as to what causes this.

Wade

iTrader: (1)

EFI says the problem is caused by temps getting too hot and/or the stock ECU detecting knock. Doug says they have demonstrated on a dyno that this is the case. The stock ECU is lowering the fuel cut below that of the PMS MAP clamp. The result is the PMS fuel cut is no longer effective. Resetting the ECU fixes the problem because the stock ECU fuel cut is returned to the normal level. Also, running race gas tends to help the problem, perhaps because the stock ECU is not detecting knock.

I can't personally verify this is true but this is what EFI thinks.

So, theoretically, if EFI would lower the PMS MAP clamp even further, it should fix the problem. Though you might need to reprogram your maps after the change. If experienced this problem I'd be twisting Doug's arm to provide a fix, assuming his conslusions are correct.

Wade

bbeavers

Thanks Wade this seems to make sense, but to your point there has to be a fix.l

finky

iTrader: (2)

Hey Wade thanks for your imput. If I wasn't in MI I would let you use my car for a guine pig. It hasn't been doing it as much since it has warmed up. In my first two auto-xs this season the problem never happened luckily. I never got into third gear though and I was also using octane booster to be safe. Hope this info helps.

Wade

iTrader: (1)

Yes Rikki using a reprogrammed ECU with the stock fuel cut and knock control removed should fix the problem. Those of you with this problem might want to experiment and borrow a friends reprogrammed to test this.

This is why I suggested someone who has the problem trying a FCD in combination with the PMS. Lower the FCD to about 7psi and then use the PMS to tune fuel above that point. You'd want to wire the FCD in the PMS harness though so the PMS sees the real MAP signal and the stock ECU only sees 7psi.

Or, after the EFI Xtreme has been out for awhile, we could probably get Doug to lower the PMS MAP clamp futher. This would be tough though since they are working overtime trying to get the Xtreme released (and probably will be very busy on it even after it is released).

I agree that the fuel cut shouldn't be terribly harmful (yes, all it is doing is cutting fuel to one rotor, I don't think it actually causes knock like some people think), however I don't think it is generally a good idea to hit it either or keep your foot in it if you feel it - I'd try my best to avoid it.

To anyone having a problem at an Autocross or on the track - be absolutely sure you aren't experiencing fuel slosh, as this is another very common problem.

Hope this helps,
Wade

CrispyRX7

iTrader: (139)

Wade,
I concur. In numerous discussions with Peter this is the conclusion we were both drawing. I had a PFS purple box with the old purple software and the car ran fine. I then upgraded to the "pink" hardware/software and started to have this exact problem. I track my car and the problem would be much more pronounced on the track than on the street so I believe in only the worst cases will it occur on the street or at the strip. On the track it was consistent fuel cut about 3-4 laps into a 20 minute session. I datalogged and it *IS* coolant/engine temperature dependent. The warmer my car got the worse it would be. If I ran 104 race gas no problem. If I ran 93/94 street gas, bingo, fuel cut every time. Very annoying. This was only using the low 10psi setting also. Put all this together and the only attributable cause is a knock sensor initiated fuel cut (not fuel slosh). According to Peter the PFS "pink" hardware has problem dealing with the stock knock signal and initiates a fuel cut when under heavy consistent load under boost. Typically 6k rpm but as mine got worse it would creep lower and lower into the rpm range. There is no real solution but as Peter mentioned some cars see it some cars don't. BTW my problem was repeated on the dyno at KD's once or twice, no datalogging unfortunately. Reset ECU and the car would do a nice clean "good HP" pull...then the next pull we would get a fuel cut. Dave said they had tried numerous things like shielding all the wires to stop spurious electrical signals etc and nothing they tried worked for those cars that saw the problem. This is all I know. Hope this info can be helpful to some of you
Good luck,
Crispy
FWIW I am now using a PFC

Wade

iTrader: (1)

Chris,

Thanks for the information. Glad to hear your experiences are consistent with EFI's explanation of the cause of the problem.

BTW, wonder if anyone has tried unbolting the knock sensor from the engine or padding the mount (so the stock ECU doesn't see the knock)?

Wade

CrispyRX7

iTrader: (139)

Not my words but here's an update from Peter through a second hand source. I'm not convinced this isn't a band aid solution for a deeper rooted ECU problem but if it works for some then happy trails. IMO one data point should not be interpreted as a solution for all.
Regards,
Crispy

"He finally got hold of a car that did it consistently and was able to reproduce the problem even after removing the purple computer. Apparently, at a steady 10 pounds of boost, the stock knock sensor would start acting up. They moved the knock sensor to another location and the
problem went away."

Wade

iTrader: (1)

Thanks Chris.

"He"... meaning Peter or Doug? Doug told me months ago (maybe a year ago) that he had reproduced this problem on a dyno and proven that it was heat/knock caused. His explanation made sense to me but I didn't have the problem so I couldn't argue with him. He seemed to think that no one would listen to his explanation.

If Peter finally duplicated the problem as well and found a solution, this would back up Doug's claims.

Not sure what you mean about a band aid solution for a deeper ECU problem... [what we believe is the cause] is a function of the stock ECU that is doing exactly what it is supposed to do... encourage you to stop driving so hard when the car is being overworked (overheated, knocking).

Yes, it is a band-aid, as just about anything that allows us to modify our cars beyond stock performance. Is using a Power FC or reprogrammed ECU with no knock function at all not a band aid solution?

I suppose keeping the fuel cut feature of the stock ECU and using better gas/reducing temps so the fuel cut doesn't happen is the only "proper" solution.

Regardless, I'm glad to hear some progress is being made and Doug's explanations are being supported. I would greatly encourage anyone with this problem to try some of the "fixes" (use a reprogrammed ECU under the PMS instead of the stock ECU, try better gas, try muffling the stock knock sensor... etc.)

Wade

CrispyRX7

iTrader: (139)

Wade,
He being Peter. Well "band aid" in a sense that
what Peter was suggesting was to just move the stock knock sensor to a location where it wouldn't detect as much knock or be less sensative. Like you said if the car be a knockin' then moving the sensor to avoid the fuel cut doesn't sound like such a smart move to me. My basis for the assumption regarding a deeper rooted problem is on my car I was unable to create this problem on the stock ECU running back to back track sessions, one with the PFS "pink" installed one with just the stock ECU all other things being equal. FWIW I never had the problem with the older 1st generation "purple" box. I upgraded to the "pink" hardware/software and immediately had this issue.
And I guess is part of the reason I beleive it is more than just a problem with the stock knock sensor

No argument that the other ECU's that ignore the stock knock signal are no better a solution that Peter's. It doesn't make this a right solution though. Maybe if a J&S was hooked up to "replace" the stock safety device then perhaps but yeah you're right.

And yes (I agree with you I think) that using the proper gas and fuel maps, reducing engine temps to be the optimal solution as one should never get to a point where detonation is imminent.

In short yup "they" found a fix I just hope it doesn't come around and bite back. I for one would be leary if I was told to just move my knock sensor and the fuel cut would go away. It still begs the question why was I getting the knock signal in the first place?

Just a thought.
Regards
Crispy

Wade

iTrader: (1)

Chris,

Thanks for the contributions.

Were all your fuel maps in the PMS set to +0%? If not, the extra fuel could have been the difference between your two back to back track sessions. We know that extra fuel doesn't cause knock, but it can cause extra noise or misfire that the stock ECU might not be "interpreting" correctly.

Some supporting of this would be what Silver93 said above:

"When i was hitting that "fuel cut" i was running SO damn rich , its not funny. I think back then i had added like 32% fuel! ha! you should have seen how black my exhaust was! after wideband, i'm down to like +8% (i think, can;t recall, maybe +10)." [it's actually +8% and still richer than necessary for 14psi -Wade]

I'm not suggesting that this was necessarily your problem but it might be a possible explanation. At this point we will never know exactly why you couldn't reproduce it with no PMS since you are no longer using it, unfortunately. At least we now think there are some solutions, people have several options to try before giving up on the PMS.

Wade

CrispyRX7

iTrader: (139)

Well I don't really think I've been of any help expect to poopoo Peter's solution. I kinda wish I DID have something constructive to contribute

No. But they were Peter's *factory* settings. However see below. Besides I was under the impression that 0% did not necessarily indicate the PMS was NOT adjusting fuel addition (or subtraction) in some shape or form.

This is definitely a possibility. However I can say that shortly there after I had the car on the dyno and lamba's were in the very high 10's to low to mid 11's so I was not running rich enough IMO to cause any kind of problem. If anything with the stock ECU alone I would suspect the leaner mixture to be more likely to cause onset of detonation. Still the issue seems to be more with spurious noncredible knock signals than anything else or at least misinterpretation of the existing signal. FWIW when we (*ALL* of my track friends running PMS ECU's have had the same issue in differing degrees of severity)first started having the problem we both increased and decreased fuel with no effect. On the 10Psi setting I was IIRC in the +8% to +10% range at 6k rpm using the stock injectors and original OE fuel pump. Safely rich IMO but not the black smoke belching kinda rich.

It seems most definitely plausible but I don't know how this can account for my own data.

Amen. I sorta wish I'd known about this earlier too. But after 2 years of "suffering" with this problem and with no real help from Peter I had no choice but to move on to system that worked - for me. I have no regrets.

Regards
Crispy

Wade