Rev Limiters
10-04-2005, 05:54 PM
#1
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Rev Limiters
Inspired by the RPMs thread... When I first bought my 4Runner in July of 2002 I took it out on an isolated, flat mountain hwy here in my town. (I know we are all against it, but I haven't done it anymore since I've started wrenching on cars and see the damages) I hit over 100 mph. I am assuming the rev limiter kicked in and shut my engine off?! My wheels locked up and I pulled to the side of the road. No cars for my best guess 10 miles on the mountain hwy. I put it in park and had trouble cranking it, but if finally fired right up. I collected myself and turtled my way back to my 'wheeling spot on the hwy. My question is, is the engine supposed to shut off? I know normal operation is the limiter is supposed to shut the RPMs back down, but why did it shut off?
I know better now and it taught me to slow the heck down. So flame on, but answer the question too.
I know better now and it taught me to slow the heck down. So flame on, but answer the question too.
10-04-2005, 07:06 PM
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It's definately not supposed to shut your engine off, nor lock your wheels up. I don't know what you mean by the wheel lock-up, because at 100mph you would've crashed hard if your wheels locked up...
Either way, engine isn't supposed to shut off and all the rev limiter does it stop the RPMS from going higher (it's set at 6250-ish I think) but doesn't make them go lower, you can try that in neutral by stepping on the gas and seeing what happens...it's not bad if you do it just for a short time.
The thing you might've hit was the speed limiter (set @ 109mph) which basically "calms" the throttle until you reach 105mph and then it lets you do your thing until you reach 109mph again etc. etc. But even that shouldn't shut your engine down...
Either way, engine isn't supposed to shut off and all the rev limiter does it stop the RPMS from going higher (it's set at 6250-ish I think) but doesn't make them go lower, you can try that in neutral by stepping on the gas and seeing what happens...it's not bad if you do it just for a short time.
The thing you might've hit was the speed limiter (set @ 109mph) which basically "calms" the throttle until you reach 105mph and then it lets you do your thing until you reach 109mph again etc. etc. But even that shouldn't shut your engine down...
10-04-2005, 07:38 PM
#4
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I've hit the limiter in my wife's Miata a few times ( hope she doesn't see this) and it just feels like the engine is missing until it goes down a few hundred rpm. Doesn't shut off and definitely no wheel lock up.
10-04-2005, 07:47 PM
#6
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What I meant was the wheels locked up and sort of did the "towing" lock ups where they sort of go backwards and forwards. I know this because I looked at the skid marks. Skid mark, road, skid mark, and so on for a few yards. The engine definitely shut down since I remember looking at the RPMs and seeing it go completely down to the zero. I have not replicated the condition nor do I really have the desire to since it was pure stupidity on my part.
edit: I did lose some control but the vehicle slowed down very quickly, enough not to go careening off the hwy.
edit: I did lose some control but the vehicle slowed down very quickly, enough not to go careening off the hwy.
Last edited by Ironmike4x4; 10-04-2005 at 07:48 PM.
10-04-2005, 08:00 PM
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I highly doubt any engine is supposed to shut down when it exceeds a certain RPM. The wheels could lock up, there would be minimal braking assistance from no engine vacuum assist, and steering would become difficult. It would be a wreck waiting to happen, not a situation a manufacturer would knowingly put a driver into.
There can be any number of reasons RPMs would be high, such as climbing a steep hill or passing, etc. If there is a rev limiter, fuel would be cut until RPMs were lowered.
There can be any number of reasons RPMs would be high, such as climbing a steep hill or passing, etc. If there is a rev limiter, fuel would be cut until RPMs were lowered.
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10-04-2005, 08:05 PM
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The engines on my family's 97 5VZ 4Runner definately has a rev limiter, as does our CR-V (B20) which also has a speed limiter set at 105 mph....um or so I hear... The hot rodded 22R in my 84 definately does not have any sort of limiters on it whatsoever...it makes things more fun that way 
10-04-2005, 08:06 PM
#9
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I'm wondering if thats something I need to talk to a Toy Tech with? I know they legally cannot replicate the condition. Anything over 60 mph that comes into my dealership we wont even try to work on it since it's a liability.
10-04-2005, 10:57 PM
#10
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Originally Posted by Glenn
I highly doubt any engine is supposed to shut down when it exceeds a certain RPM. The wheels could lock up, there would be minimal braking assistance from no engine vacuum assist, and steering would become difficult. It would be a wreck waiting to happen, not a situation a manufacturer would knowingly put a driver into.
There can be any number of reasons RPMs would be high, such as climbing a steep hill or passing, etc. If there is a rev limiter, fuel would be cut until RPMs were lowered.
There can be any number of reasons RPMs would be high, such as climbing a steep hill or passing, etc. If there is a rev limiter, fuel would be cut until RPMs were lowered.
10-04-2005, 11:20 PM
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is that what the speedo limiter is at for 3rd gens? 105?
cause i know ive definitely buried the needle and kept going after that...not much, but slowly but surely. i know...flame at me all u want but im just wondering...
cause i know ive definitely buried the needle and kept going after that...not much, but slowly but surely. i know...flame at me all u want but im just wondering...
10-04-2005, 11:22 PM
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i have maxed out ons of cars and hit several speed limiters, none of them ever shut off the engine or locked any tires....
i had a similar situation once, but that was when i sent a piston through the side of the block doing 80 in an automatic...... i had no brakes at all, however....
i had a similar situation once, but that was when i sent a piston through the side of the block doing 80 in an automatic...... i had no brakes at all, however....
10-05-2005, 01:59 PM
#13
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I wonder if it might be a malfunction in my ECU? I'm not really worried about it, I haven't noticed any abnormal engine performance or transmission problems. I'm not going to try to find out again anytime soon.
10-05-2005, 04:27 PM
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Originally Posted by kyle_22r
nope, rev limiters cut spark to the cylinders. if it suddenly cut fuel, it could bring on a serious lean condition and destroy the engine.
On my 4runner I hit the speed limiter at 95mph. I think I had the power to go 100 or maybe 105, but its a big tall vehicle and shouldn't be going that fast.
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