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Discussion Starter #1
Could an Exige motor possibly survive a 13k+ RPM rev? I had an ECU dump done on an S240 I am investigating. The highest rev of the top 5 listed is 13076, which occurred about 200 hours ago, so it's been driven quite a bit since the (possible) over rev. The other 4 are 8700 or below. I've read several threads that call the accuracy of ECU dumps into question. The car runs well and pulls hard but I'm still nervous. If it IS possible that the 13k+ reading is accurate, what would I check for damage. Thanks!
 
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The biggest problem with over revving, is valve float (the valve spring can't return the valve to the seated position fast enough to follow the cam profile). When valve float happens, the heads of the valves may tangle with the crown of the piston. Since the valves are at an angle (the axis of the valve is not coincident with the center line of the cylinder bore) to the piston, the valve will get bent or even break off. If the valve is bent enough to cause it to stick in the valve guide, you will see a loss of power. Since the engine is still running, none of the valves broke off. To get a warm, fuzzy feeling about that engine, you can run a bore scope down in through the spark plug hole and look for indentations in the piston crown. If none, no harm, to foul.

The over rev probably happened on a down shift...
 

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Do not trust ECU dumps. They were a good idea but the execution did not work out for Lotus. When you look at total time, time at speed, 0-60 times, you will almost always find a few errors. Things that don't compute.

If you are worried about a car you are looking at, get a leak down test and pull the valve cover to inspect the cams.
 

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2005 Elise LSS Saffron Yellow
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Everything MGK says is true. I'd add that the con rods and their bearings are under tremendous loads at such a high overrev (if it really happened - other people have noted bogus numbers in the ECU log--definitely take it with a grain of salt), so I'd look carefully at hot idle oil pressure as well. 'Hot' here is defined as 'oil above 180 deg F,' which might be a challenge in winter. That said, if it doesn't have hot idle rod knock, the bottom end is probably fine, so your primary concern is a close encounter between valves and pistons, as MGK says. Does anybody have any idea where valve float RPM is on a 2ZZ-GE anyway?
 

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It's unlikely the engine actually saw that RPM and lived. The ECU dumps seem to report errors with RPMs a lot. Besides the valve issues you would incur, the stock oil pump would also fail at that RPM too. If you're doing a PPI, have the cam's inspected too.
 

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It's possible to over-rev an engine where as the rev limiter in the ECU can't control.
How? An example would be, if you were in 2nd gear at peak RPM and meant to up-shift to 3rd but instead found 1st. Mechanical over-revs may not cause immediate engine failure but can fail sometime later. Mechanical over-revs can cause the valve to kiss the piston, (float as a poster already stated) and one day, the engine eats a valve. Although this is not the only thing that can happen, immediate failure provides real-time feedback but it's the ticking time bomb fear that causes one to feel anxious.

For whatever it's worth, you now have to come to grips with either one of two things. 1) error in the dump file or 2) it happened

Just my .02
 

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Had an ECU dump on my 06 Exige done and it showed 13K+ as top rev. I told the Lotus service manager that wasn't possible, as the only way to get that overrev was to miss a shift, and the math was easy enough, would've had to put it in 1st at about 90 miles an hour. Chaos would've ensued.

He said it didn't matter, the ECU couldn't be wrong, so engine warranty was void. Elevated to Lotus USA Service manager, who got in touch with Hethel, and the factory indeed said it was an ECU problem, and they sent an email communication verifying that at that point in time, there was no over rev. All documentation conveyed when I sold the car.

They attributed it to a hiccup in the first year moving to drive by wire. Your 08 S240 was 2 years after that. Have heard of 06's with this problem, not an 08.
 

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Discussion Starter #9
Thank you everyone for sharing your knowledge - much appreciated. SteelyPip do you know what the hot idle oil pressure should be on this motor? I'm in Southern CA so we should be able to reach hot idle temps.
 
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