what's the highest you guys have your knock sensor hit? Mine went to 48, engine durty 94.1%.... I'm scared that my engine is dying, and it's about to detonate

 

i would do a search in the Pfc section.

https://www.rx7club.com/forumdisplay.php?f=47


This subject has been debated for years.
Bottom line? 48 is no big deal.

 

mine even goes up to 80 and no worries here...but then again that is only when I shift....

 

huhh. 40. i can sometimes get that at idle. nothin to worry about, if its below 100 its nothing to worry about(or am i wrong)
ive seen 120 on shifts with big backfires(midpipe rules)

 

270 i think was my highest. i believe it was loose however and since messing w/it i havent seen anything above 120 or so. i still think its broken though.
from what ive read and heard many dont pay much attention to it. just make sure your properly tuned or not running lean.

 

Waste of time to pay attention to those knock readings. If you have the supporting mods and know you're tuned well, don't worry about it.

 

If it's always making 40, then don't worry about it. If all of a sudden, it shoots up to 140, then worry. 60 or below, according to the manual is engine noise and normal. But some cars will average 60 to 70 so those are normal for THAT car, but again, just be on the look out for numbers over 100 since apparently 40 is your norm. What is your normal number anyway?

Tim

 

you posted engine durty 94.1%.

Did you mean injector duty cycle 94.1%? If so then you have a problem. if this was not the case before. then check your fuel pump and your fuel filter. You should never be running injectors at 94%.

 

duty is high, but that knock reading is nothing.

 

Hogwash. Tuning is the point of failure about 100x more often than a bad injector. If your fuel pump is up to it youre fine.

 

read it again homie. I said if he didn't have this problem before to check his FUEL PUMP and FUEL FILTER. I never said he had a bad injector.


I'll say it again you should never run your injectors at 90%. Or are you suggesting otherwise? If you are then what margin of safety are you saving when the fuel filter gets dirty or the fuel pump starts failing? They are already at 90% so that leaves 10% extra to compensate for the lack of fuel that is being delivered.

 

Isn't anything above 85% kinda dangerous because injectors can stick open?

 

I do suggest otherwise. If youre tuned for an 11.0afr and youre at 99% cuty cycle and your pump, injector, or fuel filter gives out youre gonna run lean and pop it

If you were at a 50% duty cycle and tuned at an 11.0afr and something in the fuel system hiccuped youre in the same boat.

Our ecu isnt self tuning on the wideband. Its just doing what we tell it to. If something we didnt account for or couldnt account for in tuning happens then the motor is screwed regardless of what your duty cycle is.

 

well then I am glad that I don't prescribe to what you are saying.

When I had my PFC tuned: AFR's in the 11's and 75% duty cycle MAX , and I have a walboro fuel pump. About a 2 weeks ago I boosted and happened to see my injector duty cycle at 92%. WTF? After looking at a few suspects it turned out that my fuel pump was giving out me and my injectors were compensating for the lack of fuel being pumped through. huh...

tell me what would had happened if my PFC was tuned with injector duty cycle at 99% as per what you say?

I'll tell you what POP! that's what...

No wonder people here are blowing their motors left and right. For me I get my car tuned for reliability first then power.

 

"huh..." is right I gotta post the BS flag on this one.

Your fuel pump was "going out" & your injectors compensated? RIGHT

Want to tell me how the PFC "reads" fuel pressure?

Fuel temp, air temp & air pressure.

Try again Skippy.......................

 

yes let me try this again:

When did I state that I read fuel pressure of the PFC? learn to read. I said that: after looking at a few suspects it turned out to be the fuel pump. Did you miss that? or just didn't understand what that meant? "hu..." is right obviously.


You can argue all you want but the fact remains that changing the fuel pump fixed my problem. Unless you want to call BS on that too lol.

 

This is just what I have seen when my walbro failed. I don't know who is right nor do I care.

When my pump started going out it made excessive noise (which was a good indication). But every time you tipped into the throttle more the just slightly it would fall on its face. I was warming up the car and could not even drive it out of the drive way with out it stalling. I watched my fuel ratios and as soon as you gave it gas it would go lean. I picked up my commander and watched all the parameters (8 on the screen and injector duty cycle was one that I watch) and nothing there was out of the ordinary from what I could tell. I then jumped out and took a look at my fuel pressure and it was down a touch at idle. When I tried to turn up the fuel pressure through the regulator it would not. I then grabbed a buddy/room mate and had him give it gas while I watched the regulator and I could see it decrease as rpms increased.

I then took off to work in my other car and ordered another walbro fuel pump.

When I came home I was going to try and diagnose it further to make sure that it was the pump. When I turned the key to the on position I did not hear the pump and I had no fuel pressure. The was conclusive to me that it was the pump.

But what I'm trying to say is I did not see my injector duty cycle increase to compensate for the failing pump or lower fuel pressure.

Just my .02

Joe

 

This is what you wrote....................




So you think your PFC has the ability to monitor fuel pressure & compensate for it.
Your words, not mine.

Under boost the PFC is in closed loop & directly reading your fuel map.

There's no "compensating" to it.



So you might want to rethink WHY you recorded a 92% duty cycle.
The only explanation is you boosted higher than you normally see.

 

dude? you seriously need to stop assuming things. When did I actually state the that the PFC was the one compensating? I didn't. You know what they say when you assume.

well thank you captain obvious on that great deduction that I would never think about... on no wait that's the first thing that I checked. SEVERAL TIMES. I have a boost gauge and greedy spec 2 boost controller which monitors boost in real time and up to 1/10 of a psi besides it has an alarm to let you know when you over boost to past a preset limit. So it's pretty idiot proof.

Actually I dind't come that conclusion myself. After it began happening I called my rotary mechanic and he told me what it could be. But then again WTF does he know, he only fixes FD's for a living. and for the record we measured the fuel pump flow manually and after replacing it, the problem was gone. Hence the "huh..." in my original post which really means (in case you missed that too) "wow, i had no idea that would be the cause but the proof speaks for itself."

Just for the record I find internet know-it-alls interesting. They weren't there don't know the facts but somehow believe that they are right lol.

 

Let's try to be civil guys we are in this together.

Chuck Westbrook has a thread on rewiring the pump so the main current doesn't go through the ignition switch! (this slide contactor with grease on it can be a variable resistor). I dropped my duty cycles from the 90's to high 70's with his well thought modification.
Barry

 

Injectors hitting >80% duty can electrically fibrillate and are at risk of being unable to meter the fuel the P-FC is programmed to expect; worse, the P-FC has no way of knowing the injectors aren't delivering - except for the "injector warning" via the check engine light.