loud knocking constant with engine speed
 

ok, so 1st post, hit 9k on accident on the intestate. Now the engine has lost power, engine is knocking loudly, and I think I can here a flapping noise too. Its the day b4 thanksgiving so im pretty sure I wont hear from the dealership until next week. No mods. So any thoughts?. Plz im upset and a little panicy. Do not want to drive my wifes veloster for the next however many weeks.

As much as I would like to reassure you it looks like you better resign yourself to driving the Veloster for a while.
There are a number of things you could have broke and none of them good.
Have to ask (and I don't somebody else will) how did you manage to hit 9K?

Did you downshift to a gear you were going to fast for?

Its the only way I can think our car could hit 9k unmodified.

If so, uh oh, you may be screwed.

Mechanical over rev aka "the money shift". You probably bent some exhaust valves. At that rpm it's possible the valves can float and the piston can give them a good ol smack. I would start thinking about the best way to approach the situation. You don't wanna be a jerk to the service department because they don't have to cover that kind of damage under warranty.

Floated valves and bent at least one. At best valve job on one head.

edit: civdaddy beat me to it.

What did you tell the service department so far about what happened?

In the event you did bend a valve or 16 you can bet the piston(s) have at least nicks at worst cracks. I know they get tossed out where I work if there is the slightest damage to the piston. Future failure point.

Oh yeah, duh. I'm just going to take a seat over there and shut up now.:bonk:

How did you hit 9K. That is a major Over-Rev. Miss a shift did we....

I've seen this. I know a guy who did the same thing. Bent 4 valves, cracked a piston and bent a rod. Goodbye engine. At least short blocks are less then 3k from subaru. Labors is going to be much more than that though.

bite the bullet and buy Anthony's used engine off here and throw it in yourself :lol: .. http://www.ft86club.com/forums/showthread.php?t=77957

.. sorry, these guys covered everything. condolences op, hope you get it sorted

Yeah, it was cold. I had the heat on in traffic. My hands were sweating and slipped off the shifter in the middle of a 4th to 5th. So it went into 3rd instead.

Im guessing warranty is non existant after they see data that says it hit 9k. But, my saving grace might be the fact that the warning light never came on. As a matter of fact the noise didnt start until like 10 minutes later. Then I got a low oil pressure light.

I mis shifted a 2011 Scion tC that I once had. Took it to the dealership, and told them it was making weird noises. They took the top of the engine apart and knew exactly what I did to it. Cost me a little over 7k to have the dealership repair it. Needed a new short block. Floated the valves also. Had to go through the whole break-in process after the repairs.

However, I have heard of dealerships covering over revved engines. Obviously the customer had to lie about what he knew. But most of the time the dealership isn't stupid.

For future reference... Palm the left side of the shifter knob when up shifting, Palm the right side of the shifter knob when down shifting. Less likely to hit the wrong gear.

Best case scenario, you need new exhaust valves. $1,800 to $3,500 repair out the door.

Worst case scenario, you bent/stretched some rods in the bottom end... ~$7,500 repair out the door.

You may be required to have the dealership make the repairs to retain the powertrain warranty. Also, they're most likely to do the repairs right as their top mechanics will be handling this.

Keep us updated on this whole process!

Eh, best case its covered. Ill eat it if I have too. Didnt buy an frs to drive miss daisy. I absolutely drive spiritedly. Just got lazy I guess. Like I said, it was slow traffic and when it finally spead up I got a little over zealous. But im definitely going to pay more attention now. Good advise though. I just want to know what I broke.

On a good note. My wife is not tripping at all. Whats up with that?

Let's say your bill is "X" amount. The service advisor wants to make money off of your repair. The mechanic wants to make money off your repair. Your bill is somebwhat negotiable.

When they first give you the amount, tell them that is more than you were expecting and you will have to sleep on it and give it some thought. The next day they will call you back want to know your decision. I'd bet worse case scenario you will get 10% off if you express that you can only get the work completed for "Y" amount. Don't be afraid to ask to the service writer to ask his manger for a lower bill. And also don't be afraid to ask to talk to the manager. They want your business.

Isn't the rev limiter suppose to prevent events like this?

Nope. The rev limiter won't peotect you from a mechanical over rev like this, at all.

Ok, but in fairness that's a good question. Did civdaddy's answer click? If not, it's worth discussing. Otherwise I don't want to sound all condescending, you know, like I'm talking down to you.

More info would be great. I was always under the impression that with todays manual if you down shifted when you shouldn't the ECU would shut the car down to prevent damage

So the other day I was doing about 85 in 4th, went to upshift to 5th and went into 3rd, and released the clutch but before my revs could go past about 6500 I put the clutch in so the tach didn't overrev. Is this still considered an overrev and can it do damage even though the tach never went above 6500? Car seems to be running fine but my stomach just about fell out my a$$.

The rev limiter is there to prevent the engine from blowing itself up under its own power. "I'm going too fast! Cut the fuel/ignition now!"

In OPs unfortunate case, there isn't a mechanism to prevent an engine from being externally driven (overrevved) to the point of failure. Consider downshifting to engine brake down a slope. It's a very real danger to downshift too many gears and force the engine to rev too fast.

In the case of the valves, they are pushed open by a lever but a spring pulls them shut. If the engine is rotating faster than designed, the piston gets to the top of its stroke before the valve has time to shut on its own. This is called "valve float"

The piston smacks into the floating valve and - poof - catastrophic failure.

There are other reciprocating parts that will fail because of the extremely high forces generated from accelerating them. Valve float is just the first thing that comes to mind for most people

edit: technically, any time the camshaft turns fast enough to accelerate the valve/rocker arm assembly fast enough for it to lose contact with the camshaft (bounce) it's called valve float.

That's also why pushrod engines can't rev as fast as overhead cam engines. There's more mass to push back and forth.

Nope. You saved it. Good reflexes!

Should be fine, but it's still a strain on the engine/transmission if the RPMs fell to say 2k as you were shifting, and then force the engine RPMs up to 6.5k via the flywheel too fast.

Yeah luckily I didn't let the clutch out super fast so it wasn't TOO harsh but it definitely made me cringe. Thanks for the responses guys.

OP hope you get taken care of, best of luck. Bring your service guy some Krispy Kreme donuts and coffee lol.

A mechanical overrev situation is when the vehicle speed mechanically forces the engine to rev beyond redline in a certain gear. It usually happens with a misshift.

Put it this way: If you had your engine off, you rolled the car down a hill to 80MPH, and put it into second, the same thing will happen. No electronics needed to spin an engine.

-alex

I see..thanks!

I think the shifter in these cars is prone to letting this happen, especially from 5-6. I have missed that shift a couple times (at low revs) and now make a conscious effort to hold the stick to the right when pulling it down. It's almost like it needs a little more slop. :)

Ok, sry for not posting/ updating. #2 rod bearing spun. Toyota warranteed the short block. With a little push of course. Thanks for the support. Honestly feels better than before the spun bearing.

Thanks for the update. Glad it worked out for you. Very interesting!

loud knocking constant with engine speed
 

@whatsmynameagain

Not trying to thread jacks but since you've had this experience I thought I would ask you.

I've been having this knocking sound that is consistent with engine speed but I have never over revved. I'm curious if this sound sounds familiar to your experience. It's been happening for about 5 months. Engine still feels strong however. I can't figure out what it is

I'm stock btw

[ame]http://youtu.be/nvHnLm-EtkA[/ame]


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How the hell did you manage that? Care to share?

He didn't tell them he hit 9k is my bet.

It would have been in the log dump.