[KyleL]

So a little while ago I tried to downshift to 4th and grabbed 2nd by mistake and saw the revs peg out the tach (7500+ rpm) for a split second. The car is bone stock so if I have to take it in it's no big deal. No cel's at the moment. I know at 6600 it cuts fuel so what damage is caused by over revving a completely stock motor? What safeguards are in place to help protect an m6 from a mishap at the track like I had?

[Inspector 17]

Hitting the Rev limiter or high revs for a short time isn't going to do any significant damage. However, I would certainly avoid prolonged high RPMs to avoid unnecessary wear or damage. The rev limiter is there to protect the engine and keep from damaging it as best as possible. Downshifting into too low of a gear is obviously another story. I don't know that there is much that can be done to prevent damage in this scenario except cutting or limiting the fuel to prevent the RPMs from going any higher.

[KyleL]

This was for less than a second, it just surprised me that the revs shot to over 7500 when there's supposed to be safeguards in the Ecu to save the engine. I mean, I can't leave a light without it falling down to protect the engine/drivetrain, surely it shouldn't have hurt the car?

[unavailablezl1]

Originally Posted by KyleL

This was for less than a second, it just surprised me that the revs shot to over 7500 when there's supposed to be safeguards in the Ecu to save the engine. I mean, I can't leave a light without it falling down to protect the engine/drivetrain, surely it shouldn't have hurt the car?

I would assume it should have cut power at 100 rpm above redline, which seems to be a fair observation. My M3 and Mustang GT both cut power and the entire dash light up in red on the Mustang. Quite alarming.

[ChevyRules]

The ECU won't protect you from the money shift. Nothing the ECU can do when the engine is mechanically spun up to 7500 RPM due to the vehicle speed+too low of a gear selected.

[KenB925]

not much the computers can do to protect the car from a money shift, totally mechanical. The rear wheels are turning the engine, cutting fuel or spark does nothing.

That said, if the car is acting fine, it's probably fine

[utsteve98]

Nothing can protect from this scenario. Sure it can cut fuel but can't make an engine not over rev if too low a gear is selected. If you're doing 100 and you downshift to 2nd then the gear ratio may be shooting your engine speed up to 8k or more. However if your engine didn't blow at that moment and it runs smooth still then I imagine nothing is wrong.

[KenB925]

Originally Posted by ChevyRules

The ECU won't protect you from the money shift. Nothing the ECU can do when the engine is mechanically spun up to 7500 RPM due to the vehicle speed+too low of a gear selected.

looks like you were posting while i was typing

[nicktechla]

Originally Posted by ChevyRules

The ECU won't protect you from the money shift. Nothing the ECU can do when the engine is mechanically spun up to 7500 RPM due to the vehicle speed+too low of a gear selected.

ahh never heard money shift. i just heard Mechanical Over-Rev before.

[KyleL]

Yeah it was definitely a money shift. I can honestly say it hasn't happened in the last 20yrs but i made it home just fine and didn't throw any codes so I guess it'll be fine. I guess it hasn't happened to anyone else yet lol

[ChevyRules]

Oh and to answer the question of what damage can be done to the engine when you end up money shifting it.... When the engine is over rev'd, it can cause valve float and can result in the valves and pistons coming into contact with each other causing major damage to the components.

The rev limiter is not the engines true absolute limit before valve float can occur. There is some buffer room built in obviously for further protection. But if the car is still operating normally, think you lucked out and shouldn't be any damage to the engine.

[PinHead]

CONGRADULATIONS

You passed the Gen6 Valve Train Over Rev Beta Test(without breakage ver1).

Engines have a safety margin built into them just for situation like these.


Sounds like the worst that probably happened is that he stressed a valve spring by the mechanical over Rev.

You can take in to a private shop have them check the ECM for Max RPMs Data and Duration.

If you have some Extra $$$, They can also pull a pair of valve strings off and test them, (if it would make you feel better).

(Btw the Money Shift only occurs when you're seated in the front row directly in front of the Brass Pole with a fist full of $$$)

If it was for a short duration you should be Ok

Here's a more in-depth explanation
http://performancedevelopments.com/w...rev-really-is/

[Evolvedx27]

Originally Posted by unavailablezl1

I would assume it should have cut power at 100 rpm above redline, which seems to be a fair observation. My M3 and Mustang GT both cut power and the entire dash light up in red on the Mustang. Quite alarming.

Pretty sure that red light is a shift light...

[KyleL]

Drove it back home a few minutes ago and it ran just fine, just have a rattle now coming from behind the gauge cluster. So it looks like I'll take it in to the dealer my friend works at so I can have him take a look at it. I'm guessing the excess vibration from the motor over revving caused something to become a-loose under the hood or behind the cluster