Rattling at Redline

[Quadracycle4000]

Sooooo the other day I got curious and tested how much more power I could squeeeze out of my 99.9% stock engine by taping over the rev limiter

I'm using the E5 fuel due to new UK regs, which has the by-product of being higher octane, so to make use of that, I've tuned the ignition timing. It's been running fine for months. The day after I the dizzy taped up, I showed off to some mates about how high it could go, and stepped on it. There was much clattering, and everyone cringed. That evening I untaped the dizzy.

Now, whenever I'm taking it up to the high rpms, it clatters I don't think it's knock/ping, I think I've ****ed the valvetrain but I need more insight. Is this something that I could've done?

It could be knock cos it only does it under load, at high rpms, when it's warm. I've heard that oil can get into the cylinder and lower the octane rating but then I don't know why what I did would rupture anything to let oil in. Also being summer the weather is much hotter than back when I tuned it.

 

[Quadracycle4000]

Oh and the answer was less. Less power after the rev limiter would have cut in...

 

[vexorg]

The cams are the key to more power at higher revs, different cams give different power bands, hence the term "tuned". You may gain top end power but will lose out at the bottom end.

You dont say how much above the limiter you went, there are mechanical limitaion for the valves and how fast they can close.
Or the distributer in terms of how fast it can pulse the coil (assuming it has one).
Either of those could cause a misfire type sound

 

[Quadracycle4000]

I see what you're saying. I got the feeling though when you mod the engine, you increase fuel consumption, and that it's not worth spending money on it unless you've got the 1.3L or 1.4L

I know that I've lost bottom end power from advancing it

I couldn't tell you how far above. I'm inclined to say up to about 7500? There was some mad valve float noisiness. I wonder if this has caused permanent damage. It was sat in a hangar in neutral, so no-load too. The rev limiter caps it at 6500. I've got the 1999 CG10DE, so definitely got a single coil. It doesn't misfire while driving. It'll bubble at idle if I tap the accelerator.

Actually, come to mention it, I recently dropped the idle to 650 by adjusting the butterfly and the iacv, and closing the idle screw. Still doesn't explain why it clatters at the top end though ?

Edit: I was also wondering if it could be a rattling chain. The car's only done 60k, so I don't imagine I've got issues there.

 

[vexorg]

It's not a good idea to do it on no load either

 

[Quadracycle4000]

Might be a lesson learned too late sadly.