You got the duff one!!!!

It's difficult to see what 1st and 2nd go upto when rapidly accelerating - try holding the revs at 9000rpm and see what your speed is at.

 

I'm not sure I understand this thread, do you define over reving as

1) Trying to get into say 2nd at 70 mph and when you let out the clutch the car jerks as you bounce of the rev limiter.


or

2) Dropping into 2nd from 3rd at say 45 ish so your in the Vtec zone for the maxium speed(captain) when coming off a roundabout/overtaking/showing off.

because I do number 2 somtimes, is it a problem?

 

[QUOTE]Originally posted by Subaru2000
[B]I'm not sure I understand

 

[QUOTE]Originally posted by Amuse Boy
[B] You got the duff one!!!!

 

A guy i kart with who works for Honda on the technical side was telling me that a CTR owner took his car up the box, with max revs in each gear. Unfortunately when he went to change from 5th to 6th he missed 6th and went into 2nd. Apparently the engine revved to somewhere in the 20,000rpm region before it blew. Now that is what you call over revving!!!

 

ouch!

 

pretty sure it soes, will go and test in a bit

Hmmmm---surely 2 bog standard S's with similar mileage should hit the limiter at the same speed (assuming same weather conditions etc)-even accounting for differences in mileage etc there can't be more than a few mph in it can there? from standing starts of course

would be good to know what differences there are in peoples max speeds in each gear. (suppose 1st, 2nd is gonna be realistic cos none of us speed do we)

 

I can spot these a mile off when I look at a warranty claim engine.

Firstly the piston is approaching the closing exhaust valve (where as the intake valve is pushed towards the retreating piston and due to the valve train can never catch it)

As engine speed increases clearance between exhaust valve and piston reduces because the valves have more inertia and the springs can't pull them back fast enough. Normally fuel cut will be maybe 500-1000rpm prior to the critical speed when contact occurs.

As it's a performance car rather than attempting to be a fuel economical car it'll probably be closer to 1000rpm over (the stiffer springs increase friction in the valve train hence fuel economy suffers).

Fuel cut on the honda is 9500 so Zero's quote of 10,700 sounds about right

When the valves hit the piston I guarantee you the valves will bend. If you're lucky it won't do any immediate damage (although you'll probably cause excessive wear in the valve guide and could suffer oil consumption issues at higher mileage). If they're significantly bent you'll probably have power loss and misfire because the valves won't seal correctly to the cylinder head.

As in the 20,000rpm cases the exhaust valves will break away, probably pull the intakes out as they rattle around the terminally damaged bore, punch through the top of the piston which will break apart normally, conrod will flap about in the bore making a hell of a racket and shafting the block until it punches out the side

Scared yet

 

so what's the deal with the warranty in these cases?

 

I don't deal with that so much (it's a policy issue rather than working out what's failed on the engine)

Normally we take it on the chin as far as I know.
Two reasons, firstly dealer normally just see's a failed engine and replaces. By the time I get involved unit's already replaced (although I did a report on how to recognise them so maybe that'll change).

Secondly public relations, if you go and tell someone they've wasted their engine and they're gonna have to foot the bill on the repair they ain't gonna be impressed and all you need is someone to make a big deal and next thing you know Watchdogs involved

There's two ways to approach the problem. Increase exhaust valve clearance (cut outs in the piston or increased spring rate) although you'll still get the 20,000 rpm fails or design change to gearbox to lock out going in at high rpm (very difficult and expensive)

It really depends how big your claim level is I suppose

My personal opinion is we don't pay out on warranty if you drive your car into a tree and this is just as much driver error as that. Probably why I don't work in public relations