overrev - LotusTalk

slipstream · 11-07-2007, 01:43 PM

What type of damage would realistically be caused if a downshift caused a mechanical overrev to 13,000 rpm?

Could the car survive and be driveable...with no apparent damage? Or would some apparent, and likely catastrophic damage in the drivetrain be inevitable?

mcoupe · 11-07-2007, 01:44 PM

13K RPM??? What car is that? Hope not the Elise!!

slipstream · 11-07-2007, 01:45 PM

Quote:

Originally Posted by mcoupe

13K RPM??? What is that? Hope not the Elise!!

Yeah, in an Elise.

Looking for considered answers. Is it feasible the car would survive and virtually no damage apparent, or would serious damage be inevitable?

Randy Chase · 11-07-2007, 01:46 PM

Probably kill the engine. It could depend on how long it happened.

exarkun1178 · 11-07-2007, 01:53 PM

9880is the rpm that the stuff inside on the bottom starts hitting the stuff inside on top.

so 13000 umm your going to have problems!

Nathan · 11-07-2007, 01:57 PM

I'm no mechanic... but Id assume no instant catastrophic damage, however I would have the engine "freshened up" and checked out by a mechanic. I'm guessing valves would be the thing to check? Overtime severe damage would occur

slipstream · 11-07-2007, 02:00 PM

I'd imagine that instantly going to 13K through downshift would also put the transmission at risk as well?

RegGuy · 11-07-2007, 02:08 PM

Clearly that's a calculated overrev since the tach doesn't go that high. That's about 100mph in second gear. If you slipped it into gear and let out the clutch and realized you missed the shift, it is likely that it never hit 13K rpm as you probably jammed the clutch right back in. That's my sense of what might have happened.

So tell us, what happened?

codymac · 11-07-2007, 02:13 PM

13k? Oil pump would likely break up.

TimMullen · 11-07-2007, 02:20 PM

What others are alluding to is that at that high of a RPM, the valves are likely to "float" - that means that the valve is opened so rapidly by the cam that when the cam has continued to rotate (and is no longer pushing the valve open) the momentum of the valve has continued to cause it to open. The springs do not exert enough force to close the valve rapidly enough. A litle bit of "float" is bad because the valve "slams" shut under spring pressure and can damage the valve seats.

Higher amounts of valve "float" causes more problems by keeping the valve in the area swept by the piston's movement for too long - the valves often open into the area of the cylinder where the piston will occupy when the piston is "up", but the with careful timing the valves will open when the piston is "down" and close when the piston is "up". Servere valve float can cause the pistons to hit the valves. Light "hits" can cause the valve(s) to be slightly bent, keeping them from sealing tightly. Heavy "hits" can cause the valves to bend enough that they can't close (get jammed in place).
At this point, the valves will break or you will get holes in the pistons.

"Light" hits will make the engine run a little rougher. Heavy hits. will make the engine stop completely.

If you are lucky, you didn't get any hits...

choi0706 · 11-07-2007, 02:21 PM

Quote:

Originally Posted by codymac

13k? Oil pump would be likely break up.

+1

2zzge has a very weak oil pump.. if you rebuild you're engine get the circuitworx pump..

slipstream · 01-08-2008, 07:30 PM

Ok, not that anyone is still interested, but here's the story.

ECU dump at last service said 13027 RPM as highest RPM. All others embarassingly low.

Looked at highest speed on the ECU dump, did some calculations, and the only way the 13027 rpm could've happened was a mechanical overrev caused by a downshift into first gear at about 68 mph.

That never happened while I drove/owned the car.

So I told my dealer something was wrong with the ECU dump. Dealer contacted Lotus Cars USA, who got the regional Lotus engineer involved. He investigated, contacted the engineers at Hethel, and they acknowledged that in the 06 cars the specific rev of 13027 was an anomoly that showed up in ECU from time to time, and in no way reflected an actual over rev.

Lotus stepped up, and Lotus USA and Lotus Hethel provided written documentation indicating this was not an actual over rev, and that power train warranty is fully intact.

This could've easily gone the other way. They could've written my car off as one they need not support under warranty. Great follow up, fair, good documentation.

Thanks to Lotus USA and Lotus Hethel, and my dealer for the investigation, follow through, and resulting documentation.

charliex · 01-08-2008, 07:49 PM

yeah i have a bench ecu i run at 13,000 RPM+ i notice the ecu will reset at around 13K so any reading like that must be invalid.

Boosted2.0 · 01-09-2008, 06:57 AM

at 13K you will bend at least all the exhaust valves (probably the intakes too). You will also shatter the oil pump gear. You MIGHT also do any or all of the following:

Introduce a connecting rod or two to daylight
explode the clutch disc
Snap off valve heads
break valve guides
Put peices of valves through pistons
Put peices of valve and piston back into the intake manifold or exhaust

This is not conjecture. This is based on observation of a LOT of over-revved 2ZZs back before the shift pattern was updated on the Celica.

xtn · 01-09-2008, 08:41 AM

My 2006 ECM also had the 13027 rpm logged. Was assured by LCU that this is an anomaly.

The oil pump will definitely grenade itself with one quick excursion over 10K rpm. The crank pulley / balancer is known to crack shortly thereafter, and valve train damage can't be far away. By the time you got to 13K rpm I'm quite certain conrods would break too. The whole engine would be completely FUBARed.

xtn

insane · 01-09-2008, 08:57 AM

Quote:

Originally Posted by Boosted2.0

at 13K you will bend at least all the exhaust valves (probably the intakes too). You will also shatter the oil pump gear. You MIGHT also do any or all of the following:

Introduce a connecting rod or two to daylight
explode the clutch disc
Snap off valve heads
break valve guides
Put peices of valves through pistons
Put peices of valve and piston back into the intake manifold or exhaust

This is not conjecture. This is based on observation of a LOT of over-revved 2ZZs back before the shift pattern was updated on the Celica.

Don't forget the electrical problem....

you know, the one whrere the piston rod coming throught the side of the engine knocks the alternator clean off its bracket.

dbisbee · 01-09-2008, 10:18 AM

Quote:

Originally Posted by insane

Don't forget the electrical problem....

you know, the one whrere the piston rod coming throught the side of the engine knocks the alternator clean off its bracket.

Thanks!

Boosted2.0 · 01-09-2008, 12:31 PM

Quote:

Originally Posted by insane

Don't forget the electrical problem....

you know, the one whrere the piston rod coming throught the side of the engine knocks the alternator clean off its bracket.

All depends on which rod and which side it comes out

xtn · 01-09-2008, 12:51 PM

At 13K rpm they will ALL come out. Well, except for the one that comes out first will presumably stop the engine's rotation in a turn or two, possibly saving the rest?

Hello Kitty · 01-09-2008, 02:36 PM

There is another thread here at elisetalk where someone had catastrophic engine damage from a downshift that took him to 10,000

11-07-2007, 01:43 PM	#1 (permalink)
slipstream Registered User Join Date: Sep 2007 Location: Lincoln Posts: 85	overrev What type of damage would realistically be caused if a downshift caused a mechanical overrev to 13,000 rpm? Could the car survive and be driveable...with no apparent damage? Or would some apparent, and likely catastrophic damage in the drivetrain be inevitable?

11-07-2007, 01:46 PM	#4 (permalink)
Randy Chase El Jefe - Agent 111 Join Date: Apr 2002 Location: San Diego and where ever the roads lead Posts: 23,947 Images: 761	Probably kill the engine. It could depend on how long it happened. __________________ *** V E R I T A S * A E Q U I T A S *** We have been feeling the buzz since 2002 2006 Noble M400. Getrag tranny, Quaiffe LSD, Hinged clams. Duratec dual turbo V6. Hoosier 315-18 tires. 2350 pounds. 0-60mph in 2.9 seconds. ..is a stranger in an open car. Tempt you in and drive you far away

11-07-2007, 02:13 PM	#9 (permalink)
codymac short angry bloke Join Date: Nov 2005 Location: where the east tapers out and the west begins Posts: 8,580 Images: 19	13k? Oil pump would likely break up. __________________ torque (tôrk) n. - an excuse for the lack of momentum. - let's bring back CanAm & Group B! - have you hugged your Exige today? I'm currently working on my performance driving merit badge. There's always somebody faster, sometimes it's me. Last edited by codymac : 11-07-2007 at 02:21 PM.

11-07-2007, 02:20 PM	#10 (permalink)
TimMullen Moderator Join Date: Jun 2003 Location: Chantilly, VA Posts: 10,698 Images: 19	What others are alluding to is that at that high of a RPM, the valves are likely to "float" - that means that the valve is opened so rapidly by the cam that when the cam has continued to rotate (and is no longer pushing the valve open) the momentum of the valve has continued to cause it to open. The springs do not exert enough force to close the valve rapidly enough. A litle bit of "float" is bad because the valve "slams" shut under spring pressure and can damage the valve seats. Higher amounts of valve "float" causes more problems by keeping the valve in the area swept by the piston's movement for too long - the valves often open into the area of the cylinder where the piston will occupy when the piston is "up", but the with careful timing the valves will open when the piston is "down" and close when the piston is "up". Servere valve float can cause the pistons to hit the valves. Light "hits" can cause the valve(s) to be slightly bent, keeping them from sealing tightly. Heavy "hits" can cause the valves to bend enough that they can't close (get jammed in place). At this point, the valves will break or you will get holes in the pistons. "Light" hits will make the engine run a little rougher. Heavy hits. will make the engine stop completely. If you are lucky, you didn't get any hits... __________________ Tim Mullen --- There is no such thing as Touring suspension or Touring wheels. I love being married. It's so great to find that one person that you want to annoy for the rest of your life. - Rita Rudner Chantilly, VA http://members.cox.net/elans4/ 05 Lotus Elise - Chrome Orange - No Touring - No LSS - No Hardtop - Lotus Driving Lights - Lotus "Chin Guards" - plain and simple. 94 Miata R Package - Black 72 Lotus Elan Sprint - Colorado Orange/Cirrus White

01-08-2008, 07:30 PM	#12 (permalink)
slipstream Registered User Join Date: Sep 2007 Location: Lincoln Posts: 85	update Ok, not that anyone is still interested, but here's the story. ECU dump at last service said 13027 RPM as highest RPM. All others embarassingly low. Looked at highest speed on the ECU dump, did some calculations, and the only way the 13027 rpm could've happened was a mechanical overrev caused by a downshift into first gear at about 68 mph. That never happened while I drove/owned the car. So I told my dealer something was wrong with the ECU dump. Dealer contacted Lotus Cars USA, who got the regional Lotus engineer involved. He investigated, contacted the engineers at Hethel, and they acknowledged that in the 06 cars the specific rev of 13027 was an anomoly that showed up in ECU from time to time, and in no way reflected an actual over rev. Lotus stepped up, and Lotus USA and Lotus Hethel provided written documentation indicating this was not an actual over rev, and that power train warranty is fully intact. This could've easily gone the other way. They could've written my car off as one they need not support under warranty. Great follow up, fair, good documentation. Thanks to Lotus USA and Lotus Hethel, and my dealer for the investigation, follow through, and resulting documentation.

11-07-2007, 01:44 PM	#2 (permalink)
mcoupe Registered User Join Date: Nov 2006 Posts: 328	13K RPM??? What car is that? Hope not the Elise!!

11-07-2007, 01:53 PM	#5 (permalink)
exarkun1178 Registered User Join Date: Feb 2007 Location: Point Pleasant Beach, NJ Posts: 3,630	9880is the rpm that the stuff inside on the bottom starts hitting the stuff inside on top. so 13000 umm your going to have problems!

11-07-2007, 01:57 PM	#6 (permalink)
Nathan Registered User Join Date: Aug 2007 Location: Dallas, TX Posts: 151	I'm no mechanic... but Id assume no instant catastrophic damage, however I would have the engine "freshened up" and checked out by a mechanic. I'm guessing valves would be the thing to check? Overtime severe damage would occur

11-07-2007, 02:00 PM	#7 (permalink)
slipstream Registered User Join Date: Sep 2007 Location: Lincoln Posts: 85	I'd imagine that instantly going to 13K through downshift would also put the transmission at risk as well?

11-07-2007, 02:08 PM	#8 (permalink)
RegGuy Registered User Join Date: Mar 2006 Posts: 2,935	Clearly that's a calculated overrev since the tach doesn't go that high. That's about 100mph in second gear. If you slipped it into gear and let out the clutch and realized you missed the shift, it is likely that it never hit 13K rpm as you probably jammed the clutch right back in. That's my sense of what might have happened. So tell us, what happened?

01-08-2008, 07:49 PM	#13 (permalink)
charliex disproving HD MTBF daily Join Date: Feb 2005 Location: Las Vegas , NV Posts: 8,290	yeah i have a bench ecu i run at 13,000 RPM+ i notice the ecu will reset at around 13K so any reading like that must be invalid. __________________ Black Exige S - http://goth.am 265 Mule / Elan M100 ECU Tuning, http://www.elisetalk.com/forums/showthread.php?t=39660 Arguing with an engineer is like wrestling with a pig in mud. After a while, you realise the pig is enjoying it.

01-09-2008, 06:57 AM	#14 (permalink)
Boosted2.0 Registered User Join Date: May 2006 Posts: 718	at 13K you will bend at least all the exhaust valves (probably the intakes too). You will also shatter the oil pump gear. You MIGHT also do any or all of the following: Introduce a connecting rod or two to daylight explode the clutch disc Snap off valve heads break valve guides Put peices of valves through pistons Put peices of valve and piston back into the intake manifold or exhaust This is not conjecture. This is based on observation of a LOT of over-revved 2ZZs back before the shift pattern was updated on the Celica.

01-09-2008, 08:41 AM	#15 (permalink)
xtn McLareghini Bugatterrari Join Date: May 2006 Location: Texas Posts: 5,858	My 2006 ECM also had the 13027 rpm logged. Was assured by LCU that this is an anomaly. The oil pump will definitely grenade itself with one quick excursion over 10K rpm. The crank pulley / balancer is known to crack shortly thereafter, and valve train damage can't be far away. By the time you got to 13K rpm I'm quite certain conrods would break too. The whole engine would be completely FUBARed. xtn __________________ 2006 McLareghini Bugatterrari, Storm Titanium... <mods> installed: air horn, Scroth 4-point ASM harnesses, Sector111 halon extinguisher and mounting bracket, Von Hep exhaust and rear panel delete, Pagid brake pads, red Volks CE28n wheels, Toyo RA-1 tires, Nitron SA coilovers, Sector111 (WorksBell) quick-disconnect steering wheel kit. awaiting installation: Scroth "pull-up" lap belts, Sector111 RTD Brace, Tony's heater bypass mod, and dropped steering rack mounting plates. </mods>

01-09-2008, 12:51 PM	#19 (permalink)
xtn McLareghini Bugatterrari Join Date: May 2006 Location: Texas Posts: 5,858	At 13K rpm they will ALL come out. Well, except for the one that comes out first will presumably stop the engine's rotation in a turn or two, possibly saving the rest? __________________ 2006 McLareghini Bugatterrari, Storm Titanium... <mods> installed: air horn, Scroth 4-point ASM harnesses, Sector111 halon extinguisher and mounting bracket, Von Hep exhaust and rear panel delete, Pagid brake pads, red Volks CE28n wheels, Toyo RA-1 tires, Nitron SA coilovers, Sector111 (WorksBell) quick-disconnect steering wheel kit. awaiting installation: Scroth "pull-up" lap belts, Sector111 RTD Brace, Tony's heater bypass mod, and dropped steering rack mounting plates. </mods>

01-09-2008, 02:36 PM	#20 (permalink)
Hello Kitty Registered User Join Date: Nov 2007 Posts: 335	There is another thread here at elisetalk where someone had catastrophic engine damage from a downshift that took him to 10,000

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