NO rev limiter??

[acidbug]

I am running a WBO2. I tune so I'm in the mid 11's A:F ratio wise.

My additional injectors comes on when I hit boost.

The problem where I go stupid rich is ONLY off of boost, and I can't figure out why. Part of the problem in figuring it out is that I can't reproduce it. It's totally random. It happened yesterday for a minute in stop and go traffic. Today I drove for 2.5 hours, mostly highway, and didn't have an issue. Saturday morning I drove highway for 1.5 hours and it happened once, and was horrible. I almost stopped moving on the highway.

It's not due to a bad O2 sensor, as I replaced it to try to diagnose.

But regardless, I'm still overrevving. Does anyone know HOW to set a rev limiter in the MPI tuner software?? Nick told me awhile ago that it would not interfere with my stock rev limiter while it obviously is...

Dude..i am tryin to tell you that it sounds like an injector is stuck open...One of them must be failing.

I suggest taking some time..and cleaning them out! When was the last time you ran some fuel injection cleaner?

Also there is no way to set the rev limiter..b/c that option isn't available in the software version we have.

Chas

 

[Kooldino]

Dude..i am tryin to tell you that it sounds like an injector is stuck open...One of them must be failing.

But why would it fail intermittently at random?

I suggest taking some time..and cleaning them out! When was the last time you ran some fuel injection cleaner?

Never. You mean just the $3 bottle of stuff from Pep Boys that you put in your gas tank?

Also there is no way to set the rev limiter..b/c that option isn't available in the software version we have.

That's beat. Because now I lack a rev limiter. lame.

 

[MPNick]

But regardless, I'm still overrevving. Does anyone know HOW to set a rev limiter in the MPI tuner software?? Nick told me awhile ago that it would not interfere with my stock rev limiter while it obviously is...

You are not over riding the OEM PCM rev limiter. The problem may be you are having your extra injectors adding fuel at higher then the stock rev limit. You need to set the the extra injectors to not add fuel above the stock redline.

Chas is right as far as the injector being stuck or sticking every now and then. This can also cause an over rev at lighter throttle.

 

[BradC]

Which is exactly what he is saying..the car is idling bad..and falling on its face until he get's his rmps up & above 4k..

Chas

Ok, so I can't read. I thought his motor was revving on its own.

 

[Kooldino]

You are not over riding the OEM PCM rev limiter. The problem may be you are having your extra injectors adding fuel at higher then the stock rev limit. You need to set the the extra injectors to not add fuel above the stock redline.

But what about spark?

 

[LinuxRacr]

Interesting thread. Subscribing. My injectors are different. I am using the RX-7 S5 injectors.

 

[MPNick]

But what about spark?

What about spark? On the Ford's the PCM cuts the fuel not the spark at redline, in fact most PCMs work this way. Not 100% sure but why would they change it on the Mazda?

 

[Installshield 2]

you probably know more about than I do Nick, but I have never heard of it that way...that is a very dangerous way to limit an engine, and will always result in at least one or two extremely lean cycles...I know porsche PCMs, as well as VW's and a lot of newer honda PCMs cut spark at a given rpm, and ms's after cut the injectors...that way if any residual undburned gasoline is left in the chamber it won't ignite it (just compress it and then throw the crap out of the exhaust)...its much safer...

I will try to find the link on this...there is a article somewhere online that goes into detail about this, and claims that most japanese OBD-II stock ECU's do the same...

I am not saying you are wrong...I am only saying there is no advantage for ford to do it that way, its just a better way to grenade an engine at high rpm...

 

[Little Beavis]

I'm curious too, but I wouldn't be that surprise to just do a fuel cut (while more "dangerous") it would be better "environmentally", since you wouldn't risk sending more gas to atmosphere. . .just a thought, but I'm just talking out of my butt right now. . .so I guess just consider this a bump.

 

[MPNick]

I'm curious too, but I wouldn't be that surprise to just do a fuel cut (while more "dangerous") it would be better "environmentally", since you wouldn't risk sending more gas to atmosphere. . .just a thought, but I'm just talking out of my butt right now. . .so I guess just consider this a bump.

Think about this. How about running full throttle full boost at 6,000rpms. Then shut off the ignition. What would happen with all of the fuel that the injectors are still pumping into the engine. Then let if get filled with raw fuel and turn the spark back on.

 

[LinuxRacr]

Kabloowie! (eek2)

 

[Bigg Tim]

AHHH, makes sense!!!

 

[Installshield 2]

Think about this. How about running full throttle full boost at 6,000rpms. Then shut off the ignition. What would happen with all of the fuel that the injectors are still pumping into the engine. Then let if get filled with raw fuel and turn the spark back on.

ok relate this to a pcm that cuts both...not sure if that is ours or not...but the ones the do cut ignition, also cut fuel...I am not talking about an ECU that pulls ignition completely off, and leaves the injectors operating...

pulling both will NOT ignite a lean mixture, and will NOT allow fuel puddling and flooding...

we are getting confused I think though...I can't think of an instance in which what you just described could happen...if you spray fuel in, and not ignite it, then nothing happens on the power stroke...and all that unused s*** is pushed out on the next exhaust stroke...it would be grosse and give you hellish back fires once the engine returns to normal operation...but thats it...you make it sound like there will be more than one intake stroke worth of air and fuel in there, which there won't be...forgive me if I am missing what you are saying...

So anyway...not cutting the fuel will not make your engine explode...you can turn the ignition off and keep dumping fuel all you want...9 times out of 10 you will simply stall and sputter the enigne when you turn the ignition back on (think about what flooding an engine in reality is...too much fuel)...if anything is going to pop it will be the exhaust manifold once things get going again...

Now the other end is where you can pop an engine....If you are screaming at full boost, and cut the injectors...but not the ignition...you are setting yourself up for one serious show...at high rpm, the piston speeds are so fast that it is very common for residual fuel to not be completely burned, as well not completely pushed out of the chamber...Not only that but you are still feeding fresh air, regardless of injector operation...So lots more good air, and no more good fuel will sometimes make whats known as a "flash expansion"...and very few engines can withstand a few strokes of that...this is exponentially more common on cars running richer A/F's for safety...So you can potentially end up igniting a mixture with north of 20:1 at extremely high speed...

there probably won't be enough fuel for it to ignite everything in most cases though...at least on a small displacement engine such as this...

Beavis I agree...the only argument for the environmental thing is what area the engine operates at during this limit...the stock ecu is programmed for efficient and enviromentally friendly low rpm/load driving...in which it is in closed loop...when it kicks into open, everyone knows how it gets dog rich and makes the engine suck...and the rev limit is always during open loop as far as I can tell...an area where mazda tried to keep the engine safe as possible...and being that the engine can't breathe for s*** at high rpm, and is being fed tons of fuel...leaves a lot of room for the problems I mentioned earlier in this post...

But I have no idea...all I know is that most new ECU's do both as far as I can tell...whether ours does or not is beyond me...

 

[MPNick]

ok relate this to a pcm that cuts both...not sure if that is ours or not...but the ones the do cut ignition, also cut fuel...I am not talking about an ECU that pulls ignition completely off, and leaves the injectors operating...

..

I only know of the fuel being cut to limit the rpm. Things like the MSD unit and other like it do a "soft Touch" rev control. They drop one cylinder at a time. I do not know of any OEM PCM that cuts spark out to limit rpms.

If our cars cut the spark and your thing is right then we would get the backfire you are talking about when the spark come back on.

 

[acidbug]

But why would it fail intermittently at random?


Never. You mean just the $3 bottle of stuff from Pep Boys that you put in your gas tank?

About it failin intermittently..why not..it's possible..it's on the edge of ******* up..and about to give on you.

about the $3 bottle..hello no..i mean the real s***..like run rite..and such.

Chas

 

[Aricjm15]

Think about this. How about running full throttle full boost at 6,000rpms. Then shut off the ignition. What would happen with all of the fuel that the injectors are still pumping into the engine. Then let if get filled with raw fuel and turn the spark back on.

it wouldnt fill with fuel, its a vapor when its injected in, it would go right out the exhaust manifold. if the manifold were hot enough it would ignite the mix and you would be shooting flames out your tail pipe

I know a few people that have lost a turbo motor to the revlimiter being to harsh (not on proteges) the ECU would cut the fuel and all of a sudden the engine is super lean, dentonaion galore engine ******

if you could cut timing then cut fuel it would be alot smoother and safer

 

[Installshield 2]

exactly...Nick, it appears you are not catching what I am saying...You won't get a backfire if you pull both...if you pull ignition only, then you will have an exhaust full of fuel that will most likely ignite when you turn the ignition back on...and you can get detonation if you pull only fuel...I am saying if both are pulled, its the best of both worlds...

its irrelevant though...if you say ours only pulls fuel, then I guess thats what it does...Any other ideas on what is causing Kooldino's problem?

 

[MPNick]

exactly...Nick, it appears you are not catching what I am saying...You won't get a backfire if you pull both...if you pull ignition only, then you will have an exhaust full of fuel that will most likely ignite when you turn the ignition back on...and you can get detonation if you pull only fuel...I am saying if both are pulled, its the best of both worlds...

its irrelevant though...if you say ours only pulls fuel, then I guess thats what it does...Any other ideas on what is causing Kooldino's problem?

I understand what you are posting. The question was on the Mazda and then it moved to OEM PCMs. They cut fuel only and I not sure if any do both. So I am not saying you are wrong only it is not any factor in Danas problems.

I do not see how you get detonation if you shut the fuel off. The engine is shut down and not running for that point in time. Maybe if you keep it floored and have the fuel cut come on and off for a amount of time. But at that point you should just remove the oil and blow the engine because that is what you are tring to do anyway.

Other then having the extra injectors add fuel above the stock redline I see no MPI tuner factors.

 

[Kooldino]

What about spark? On the Ford's the PCM cuts the fuel not the spark at redline, in fact most PCMs work this way. Not 100% sure but why would they change it on the Mazda?

Well, if i really want to test it, I can pull the MPI out and rev it in neutral to see what happens...

 

[Kooldino]

you probably know more about than I do Nick, but I have never heard of it that way...that is a very dangerous way to limit an engine, and will always result in at least one or two extremely lean cycles...I know porsche PCMs, as well as VW's and a lot of newer honda PCMs cut spark at a given rpm, and ms's after cut the injectors...that way if any residual undburned gasoline is left in the chamber it won't ignite it (just compress it and then throw the crap out of the exhaust)...its much safer...

I will try to find the link on this...there is a article somewhere online that goes into detail about this, and claims that most japanese OBD-II stock ECU's do the same...

I am not saying you are wrong...I am only saying there is no advantage for ford to do it that way, its just a better way to grenade an engine at high rpm...

Agreed.