Elite gearbox

[oioi]

with that sort of failure it looks very lucky the engine did not go bang.  are you going to take the head off and inspect to see if mr piston has been talking to mr valve?

[Westfieldman]

are you going to take the head off and inspect to see if mr piston has been talking to mr valve?

Done a leak down test and looked in the ECU logs and it should be OK

I am changing the big end bearings

[Bananaman]

doesnt look over hardened to me, look soft centered ie only surface hardened. Keep us updated with how you get on, as I was considering one of these, but might go with my tried and tested albeit heavy alternative.

Looks like it might be worth waiting untill a full product test has been carried out (good man Paul!!!! ......................

I think I'll stick with my Tractor gearbox for a while yet.    

[Westfieldman]

I think I'll stick with my Tractor gearbox for a while yet

That will be best with your tractor engine they go together so well            

[Matt Seabrook]

That will be best with your tractor engine they go together so well            

So what does that say about your engine then Paul if your broken gearbox matches you engine    

Just to add sorry to hear of your gear box  

[stu999]

Why did it spin up to 10,000rpm?

[YouMustBeJoking]

Doesn't the ecu have programmable rev limiting    

[S8ight]

Doesn't the ecu have programmable rev limiting    

wouldnt of reved from ignition, would of been when the shaft let go

[YouMustBeJoking]

wouldnt of reved from ignition, would of been when the shaft let go

How does that work then  

[Nick M]

An ECU rev-limiter can't cope with mechanically induced over-revs - an an input shaft snapping would have caused a sudden loss of load in the engine so it would have just spun up very quickly.

I imagine the ECU complained loudly with lots of popping and banging, but there's not much it can do to slow down the inertia of the crank, pistons, flywheel, etc.....

It's like changing down into first gear at 90mph - no rev-limiter is going to prevent the engine from over-revving in those circumstances.

[YouMustBeJoking]

But this isn't mechanically induced over revving in the way that a change from a high to low gear would be.  The sudden loss of load will allow the engine to accelerate rapidly, but cutting the spark will stop that instantly.  No matter what load the engine is seeing, if the engine is disconnected from the wheels with no spark it cannot possibly accelerate.  This is exactly the circumstance that a rev limiter is intended to protect against.

[stu999]

An ECU rev-limiter can't cope with mechanically induced over-revs - an an input shaft snapping would have caused a sudden loss of load in the engine so it would have just spun up very quickly.

I imagine the ECU complained loudly with lots of popping and banging, but there's not much it can do to slow down the inertia of the crank, pistons, flywheel, etc.....

It's like changing down into first gear at 90mph - no rev-limiter is going to prevent the engine from over-revving in those circumstances.

Mmm. I must admit, I'm having truoble picturing this scenario in my minds eye. As I see it, a sudden loss of load will merely be like revving the engine with no load - and the rev limiter should stop it going any higher. I cannot see how the engine would rev any quicker/higher just because it was under load one second, and free revving the next...

Changing into first from 90mph is not to be recommended however

[steve_m]

But this isn't mechanically induced over revving in the way that a change from a high to low gear would be.  The sudden loss of load will allow the engine to accelerate rapidly, but cutting the spark will stop that instantly.  No matter what load the engine is seeing, if the engine is disconnected from the wheels with no spark it cannot possibly accelerate.  This is exactly the circumstance that a rev limiter is intended to protect against.

I would have thought that too but there was some debate (argument ) earlier this year regarding the Hayabusa engine.  Apparantly with the clutch pulled in (you have to do this to start the engine) the rev limiter is lowered by 400 rpm, Suzuki claim this is to stop the engine over revving with no load as the ECU can't cut the spark fast/early enough.  Maybe not having a flywheel helps this but in any case, I've tested it and it does limit a good 300-400 rpm lower.

[Westfieldman]

MBE logs show that the engine speed over the rev limiter was for a few hundred rpm over the limit and for only a second or so as you need to add up the readings

I saw 8,500/9,000rpm on the Stack and the Ecu shows less

Suden loss of load will let the engine spin faster for a second or so this was limited my the ECU cutting the spark and me liffting off

[Nick M]

But this isn't mechanically induced over revving in the way that a change from a high to low gear would be.  The sudden loss of load will allow the engine to accelerate rapidly, but cutting the spark will stop that instantly.  No matter what load the engine is seeing, if the engine is disconnected from the wheels with no spark it cannot possibly accelerate.  This is exactly the circumstance that a rev limiter is intended to protect against.

It rather depends how quickly the sudden loss of load happens and how much inertia the rev-limiter is trying to limit.

Note that I didn't say how long the situation would exist, just that since the limiter is electronic rather than mechanical it can't slow down the crank other than by influencing things which make the crank spin in the first place, i.e. fuel and spark.