Rev limiter

[Ford Builder]

I have a question does our cars have rev limiter's ? if so can we change them!

[FoxBuddy]

The first week I had my SVO I was driving quick off a set of lights and when I shifted from second to third at WOT the floor mat got caught on the accelerator. Of course it red lined before I could get it un-stuck but it peaked at 6500. No higher. I figured the ECU limited it to that...

[Ford Builder]

Wow that must have been a wild ride, so what you're saying is, I don't need to change it. Thanks

[MikeFleming]

The PE is set to cut fuel (randomly) at 6500 RPM, and re-start fuel at 6350, iirc. So ti will "dither" between those two RPM levels if the throttle is held steady.

Note that hte EC is not very sophisticated in those older years and it is NOT a good thing to hold on the rev limited for long as the cylinder-to-cylinder and per-cylinder conditions (as fr as fuel flow) are very inconsistent, which can mean dangerously lean. It also seems like there is lots of knock detected because of the often violent movements of the engine, along with its built-in poor NVH issues, when the fuel cut is reached, and that will severely reduce ignition timing which leads to very high EGT values. Which is bad.

A few seconds at an auto-x is OK, but holding the throttle open for ten+ seconds on the limiter is very bad.

Newer engine mgmt controllers are capable of cutting individual cylinders completely of fuel (so it's 100% lean) while still supplying the proper fuel/air mix to the [other] active cylinders, if any, to reduce power as a rev limiter. So there is less danger of staying on the limiter.

Most of the other Ford Turbo EECS have a fuel cut in the 6250-6300 RPM. I have a list somewhere. This can be modified using a chip, EEC tuner, QH, etc. and the appropriate programming tools. I set the RPM cut in the Red Baron to 7500 for a spell but have since lowered it to 7100 for unrelated reasons.

Unrelated reason: I originally had ALL the front pulleys powder coated (gloss black) and have experienced much difficulties with the v-belt pair staying on above 7200. Probably something to do with the low friction level, who knows - it's definitely not an alignment issue. When they decide to n longer stay in the grooves, it makes a mess w3hihc usually destroys both belts and puts the car in Walk Mode unless I carry spare belts and associated tools. Fortunately they're really easy to change.

Someday I may find a way to remove the PC material from the pulley grooves where the belts ride (lathe work?) while keep it on the rest of the pulleys, or just blast it all off and spray something on, letting the v-belts wear the spray off the grooves.

Decisions, decisions. for now I just shift by 7100.

[Chuck]

What about the LA3 series of EECs? Does the RPM limiter affect the same RPM range?

[MikeFleming]

The LA2/3 is slightly lower than the PE, iirc 6300 max RPM.

[FoxBuddy]

Wow that must have been a wild ride, so what you're saying is, I don't need to change it. Thanks

Knew it was stuck, quickly thought it was the linkage stuck. First thought; push the clutch in as tapping the accelerator: red line. Second thought: kill the ignition and pull off to the side. Pull carpet out and yell at it.

[MikeFleming]

Second thought: kill the ignition and pull off to the side. Pull carpet out and yell at it. THIS is something we need to practice in EVERY car we ever drive. So we know the procedure and what actually happens. There are several cars now that have Start/Stop buttons and the "kill" process is slightly different between models and mfgrs. Be sure to test in/out of gear for automatics. Very important in rentals that you're not familiar with. Then teach your kids, and parents.

This knowledge may save your life someday.

[Ford Builder]

Thanks Mike, I will have to look at my tach when I reach my shift points more closely seams like its leaning out and bucking back if I mash the throttle to the floor, if I push the gas slowly to the floor it does not buck back or I think leaning out. any suggestions ??

[MikeFleming]

The only way to determine "lean" is with proper instrumentation. Find a local dyno with a wideband and get some real numbers.

Too rich often "feels" the same as lean, btw. The factory EEC is programmed to go to 10:1 at WOT (TPS >~80%, iirc) - provided the injectors can keep up.

[Ford Builder]

Well Mike, I have Mustang Dyno at work at my disposal we test our restored cars after they are completed, I have meaning to ask the boss to do a test run, just wanted to get all the bugs out , BUT this one, curios what HP its bringing to the table. I will keep you posted.