Ignition is cut off, not the fuel.

1st, if fuel was cut, you would think you just hit a wall with the car. That's not the case. The rev limiter is a soft limit in which the igntion is cut.

Second, go to an autocross and watch one of the cars when it hits the rev limiter. Notice the black stuff coming out of the exhaust, it's unburnt fuel.... I know this argument has come up before, but I can tell you from experience that I've seen the black cloud of fuel myself when the rev limiter was hit in a protege. If the fuel was cut, then that cloud wouldn't exist.

 

my max out was in a speed trap at night with no radar detector
it was at 115mph in a p5 with alot of my bands equipment in the back

does anyone else notice a sulfuric smell when they go around 80-90 for a while??

 

The FS motor and I suspect just about any OBDII compliant motor uses a fuel cut-off. The reason is emmissions related. Unburnt gas cause dramendous emmission voilations. . . and is a no no.

I would be very surprised is the Protege uses a ignition cut.

I am not sure how you would have a "soft igntion limit" anyway. . . you either have ignition or you don't. . . If you don't then that would be a pretty "hard limit". . . . fuel cuts can be made to reduce the effects of "hitting an rpm wall".

 

Reducing fuel would cause a lean condition, and resulting with no black smoke. Manufacturers wouldn't do this for warranty reasons.

Cutting fuel completely, makes the car feel like you hit a brick wall. It doesn't do that.

Ignition cut results in a "soft cut" where it doesn't feel like you hit a blunt object.

Do you have documentation or evidence that the fuel is cut?

I have no documentation of ignition cut, but I have personally seen the evidence of it, on the Protege and MANY other OBDII cars.

 

I like bouncing off the rev limiter myself. Where do you think my screen name came from?

 

What on earth is a noid light?

 

I have no fvcking idea

 

Excellent info BryanPendleton! This is the kind of post that makes coming to this forum worthwhile.

You mentioned skipping 4th gear when running 1/4mile. Did I read that correctly? So shift from 3rd to 5th?

 

He means that stay in 3rd gear, do not go to 4th or 5th. Obviously 3rd gear has a top end speed and a top power, but the time lost from shifting into 4th gear to go faster wouldn't be worth it.

 

Thanks for clarifying that up gcs118. I was confused for a moment also in part due to the fact that he missed the optimum shift RPM value from 3rd to 4th, so I assumed incorrectly that there might be typos.

 

My 1996 Ford Technical Service Manual states that fuel cut exist as "some" rpm. . . I forgot the exact rpm though. . .

A lean condition is harmful when there is enough fuel to generate significant combustion chamber pressures and temps, you can SIGNICANTLY reduce fuel injection, and simply burn a small "charge" of fuel, which will be burning lean, but there is not enough to cause significant combustion chamber pressure and temps to risk pinging, knocking or detonation.

When you start modifiying the car with aftermarket turbos, electroics, etc. then a fuel cut becomes a potential threat. One reason tuners and builders switch to a new ignition such as MSD, to install a ignition cut limits as opposed to the fuel cut limits on most production cars. Neons have fuel cuts, but I would be will to place money that most OBDII cars, if not all, are fuel cut.

 

Timing light perhaps?

 

Anyone with an EGT sensor and gauge, willing to hold the rev limiter and see what happens to the exhaust temps?

I'm going to try to borrow a friends, OBDII Logger and see what happens to timing at the rev limiter.

As for OBDII cars, with fuel cut.

ALL 2G turbo Eclipses have ignition cut as a rev limiter. Fuel cut is used if you overflow the MAS. 2G Eclipses ARE OBDII cars. For whatever reason, the government doesn't care about WOT conditions. At least they didn't when OBDII was developed.

What's your theory for the source of black smoke coming from the protege when I reach the rev limiter? Lean mixtures don't create black smoke, and there "should" not be enough carbon build up in the engine (~13K miles) to have excess carbon burning off from increase temps caused by a lean condition.

 

I don't claim to have the answer on this, just speculating. My FS is (actually was, now using E6K) controlled using Ford's ECC V engine managment system. The Pro5's probably are using Mazda's engine managment system. Two different animals. Perhaps its Ford or domestic labels tend to use fuel cut over ignition cut. *shrug*

Black smoke would lend itself toward a rich condition caused by an igniton cut. There could be other things going on too. . .*shrug*

 

I'm blabbering off, but my speculation is based on the experience with the protege5 that I've had.

The only way to really get the answer, is to monitor the engine and see what is going on, or from reading about it in a tech manual. I don't know of one that is available for the protege's?