Well today I was cruising along at about 70 mph on the highway when I decided to switch gears to pass someone who had just cut infront of me. I forgot however that the cruise control was on and when I pushed in the clutch the motor shot up quickly to about 9k before I was able to cut it off. My question is, what are some potential problems to check for? I didnt have any problems the rest of the drive all gauges red normally. I didnt experience any power loss or feel anything odd. Thanks. BTW, it's an S4 motor with an S5 intake manifold.

 

I would say not to worry about it bro... I've missed a shift before and the s-afc read well over the tach shot some flames, and that was about it... If the car runs normally after this occurance i wouldn't worry about it.

evan

 

um...i thought the rev limiter on a s4 didnt let you go past 8250-ish? cause once i was holding the throttle down completely in N and it basically hit a wall at about 8250-ish? so thats really weird...but i have been driving for months now, without a single problem..

try not to think about it...it should be ok

Jahan

 

I was thinking the same thing. The motor should have stopped short, but for some reason the engine went much higher than expected.

 

what rev limiter? there is no limiter.

 

^LOL, ok that explains it then.

 

imma go outside and see how high i can overrev my motor! ... jk. but seriously, i didn't know that there is no rev limiter...

 

S4's don't have a limiter, just the S5 and up, i think there's a fuel cut thing though.

 

he mean that clunk sound when the motor stares vibrating and lossing power. something to do with an apex seal or something. thats the rev limiter he means =P

 

It doesn't matter if it has one or not; if you miss a shift the tranny will puch it past redline whether there is fuel going to the motor or otherwise.


--Alex

 

Oops double post - see below

 

It says in his first post that it went up that high because the cruise control stuck, not from a missed shift.
I've had mine do this too, if the switch on the clutch is sticky the cruise won't shut off when you press the pedal.

 

That only happens if you throw it in too low of a gear. The engine has to have fuel to gain speed.
Also, I'm pretty sure the s4's have some sort of rev limiter. Mine hit a wall at about 7800.

 

mine had an annoying beep when i hit past 7 grand but never cut me off...

 

I missshifted in my s5 and was >9000 rpm (off the dial) while spinning around 4 times from rear end braking. My engine still seems relatively as strong as when that happened 2 years ago.

It will do less damage since it was unloaded too.
You should fix that clutch switch.

Stephen

 

Most tach's read incorrectly and optimistically as rpm climbs.
There is a rev limiter if running a stock ECU. Not sure if it is timing or fuel related but its there.

Also, depressing clutch should kill the cruise control. You should look into why that didn't happen.

 

if you want to get down to it, the rev limiter is the person behind the wheel with their foot on the gas pedal.

 

Crusing at 70mph with cruise on….. push in clutch and it rev’s to 9000.
So what rpm’s is 70 mph (3800?) and it took you that long to let the clutch back out?

 

i hate to be a source of misinformation....but from personal experience i know for a fact the engine hits a wall (fuel or timing..as stated above). I was having some problems with the car...and my rotary mechanic basically held the throttle cable down from under the hood, and it wouldn't rev past 8200-ish (maybe slightly lower?) on my S4.

Of course it's a different story and you mis-shift and the engine matches the revs to that of the wheels in the selected gear...that could be catastrophic (flywheel shattering?) if you select a very low gear at a very high speed.

BUT the original poster said the throttle cable was held down by cruise control due to the sticky clutch switch which didn't deactivate the cruise.

So, why didn't his car ever hit fuel (or) timing cut? maybe because he has a S5 ecu with a S4 block??

Either way...i doubt you caused too much damage. Don't stress it.

 

It was a pretty steep incline and it was only at about 2800 rpm, so i'm sure the engine was pushing the engine due to the lack of power at that rpm.

 

You'd be surprised how fast an unloaded (clutch in) rotary will climb til it stops. I've done it before too. Besides that, if it won't disengage the cruise with the clutch in, it takes a second to figure out what happened, because the cruise pushes it up with your foot off the gas so to stop it you have to figure out that the cruise control did it, and turn off the cruise control, or get it in some gear at 7500 rpm +.

Oh, and your flywheel wouldn't shatter, because it's surface friction based, it doesn't lock in or anything, and it doesn't really care what gear you're in. Who hasn't, at one point or another dumped the clutch with the engine at 5 or 6 grand and left a nice long burnout? It'd actually be easier on the drivetrain at highway speed because the tires are already rolling.

 

Well... on the terms of 9k...

http://www.rerev.com/temp3/9kish.avi

Oh.... and a little straight downhill speed:

 

Damn! Couldnt get the video to work.

 

I dust.

 

I do believe I hit a rev limit the other day. 1st gear, power loss around 8300