There's always a lot of confusion over rev limits. In a case like this especially so. Why? Because the likely cause of the failure is a previous overrev on a downshift. It doesn't take much to weaken the retainers leading them to fail at a later date. Nothing to do with cooling mods at all.

Most people don't realise when they've overrevved. If the engine doesnt lunch itself there and then they think they're fine. When doing a valvespring change on a UK members car recently I'd insisted that new retainers were fitted as part of the process. In the end the owner didn't go for uprated ones, but did get the later spec Honda ones. Lucky they were replaced too - too of the retainers were stretched...

Kobe, I'd be very surprised if your Mugen ECU did rev to that. The others I've checked don't. More likely the method of measuring the rpm on the dyno wasn't accurate which would also explain why your peak power figure was so much higher without engine changes that could affect it so much.

As to the rev limit itself. The Mugen ECU is fine with the stock valvetrain. Mugen didn't just raise the limit, they also changed the nature of the limiter itself somewhat. Mugen's ECU runs a very different codebase to the standard ECU - unlike a lot of the others which are just remapped tables on a standard Honda codebase.

-Brian.

 

Hi lads...

We must convince Amuse_Boy not to drive his S anymore...

Anyway... it is not an overheating case, but most probably the valves didnt went back on time into the seats due to the high rpms... It was a bad moment..

 

Thanks for you rinput Brian

Marios - don't worry mate - if my engine lets go - we could do a GB on new engines together

 

[QUOTE]Do we know of any cars that have *not* let go with the Spoon mods

 

I doubt that very much. Even with the stock valvetrain the valve float rpm is higher than the J's ECU can hit under power.

It's most likely that you'd a previous overrev on a downshift which weakened the retainer, leading to the failure later on.

You do get a lower valve float rpm if you've a stretched retainer giving a higher installed spring height. But for that to lead to valve/valve contact would be unusual as you'd need some stretch on both intake and exhaust retainers at those rpms. Which would be unusual again - the intake valve is a lot heavier, tending to give problems on the intake side first.

It's more likely that the intake valve dropped first then the exhaust valve dropped after being damaged by the intake valve. Always an inexact science diagnosing from pics, but that's by far the most likely cause.

-Brian.

 

I am feeling a little uneasy, I confess I have downshift overreved the car twice. Not impressed with the fact, just down to not thinking straight and trying to keep it in the band. It is sounding as though it might be time to do some mods to the engine including replacing the retainers to take advangtage of the Mugen ECU. Now where do I go from here before it ends up looking like above?

 

Although am against putting "fingers" into the engine the best thing to do is to get some reinforced retainers and spring. Especially if you are have mods on the S...

 

Actually the damage inside the pot is surprisingly small, considering some idiot left a valve in there.

Even the other pots survived quite well, considering some of the valves were jammed open once the camshafts got buggered.

I understand that the engine has a bigger margin of error than 9,200, so I doubt that that would do it alone.

There's no obvious frying of the valve heads, etc so leaning out looks unlikely to have been a factor, so the mods may not be culpable.

Which all supports Brian's opinion.

 

So next question - how easy is it to change retainers?

 

Group Buy anyone?