Right after the headgasket swap the other week the engine is running as smooth as anything

But before it went I had a little niggle with it seemingly been down on power one minute and perfectly ok the next. Now I still have this and it is annoying the hell out of me.

I think it is one of two things either the wastegate is sticking open for some reason or the cat has collapsed

It really does feal as though someone has stuck a potato up the exhaust pipe when it happens and there is also tinkling from the exhaust when you rev the engine which makes me think it's the cat. The only thing stopping me from ripping it out is that it is a very expensive stainless sports cat and it is lucky if it has done 2K miles

Any thoughts before I spend the afternoon swearing swapping the decat back in?

Assuming you have some kind of data logging with boost levels & TPS

If it's the turbo/wastegate I'd expect to see an increase in spool-up duration (in car the turbo responds quickly & actual lag is low but the spool-up becomes a smoother less punchy surge). While if it's the cat you're more likely to see an increase in lag but little change in the spool-up characteristics & the turbo tending to stall a bit faster when feathering the throttle.

I'd think wastegate (or BOV, or hose, or wastegate control), if only 'cos it's intermittent -- can't see a collapsed CAT uncollapsing itself.

And the answer is.............................. Collapsed Cat





Basically the remains of the cat were in a ball the size of a cricket ball rolling up and down inside the cat can, so if you floored the throttle etc the remains were blocking the exhaust and depending which way the ball was facing you either got the open end of the honeycomb so had power, or it was side on so nothing.

Chuffing hell!

Hope it was guaranteed! If not, Aaron did mention that one off a V6 Rover was about the right size and should flow a lot better than the stock one.

It bloody well better be under guarentee, I shall be doing some moaning on Monday i can tell you,

I also wonder if this was one of the reason behind the HG failure the back pressure this was generating when blocked would have been incredible

Certainly possible. I think they'll replace -- wouldn't look good for a race cat safe up to 400 bhp to have gone on a Cinq producing less than 150............. :bang:

why bypass the cat then have a emission check. these engines seem to fall well within the margins even with it removed!

I like to be environmentally friendly



Actually it is there as a silencer as much as anything, the exhaust is too loud for me without it, (although it has the decat in now and it is not as bad as I rememberd) and as the car does tend to attract a bit of attention I like to make sure everthing is above board

if the car is runing real rich it can make your cat do that might wanna lookin to that

fasted said:

if the car is runing real rich it can make your cat do that might wanna lookin to that

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AFR's are spot on 11.6 to 12.3 on boost 14.5 off boost

allanhelen said:

I like to be environmentally friendly

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You'll be destroying another russian village for the mining of the metals though

Tis a bugger that though! How much was the cat itself?

You can run about with a decat for now can't you?

Krisitan

kritip said:

You'll be destroying another russian village for the mining of the metals though

Tis a bugger that though! How much was the cat itself?

You can run about with a decat for now can't you?

Krisitan

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I'm a NIMBY if i have to trash part of Russia to keep the roses blooming in my little part of gods own country then so be it

The cat must have been close to a couple of hundred pounds when i bought it and it wasn't fitted on to the car until October last year. Just checked and the car only did 1,700miles between May last year and May this year so the cat can only have done a few hundred miles at best

I'm running with the decat now and it is not as loud as I remember.

Well as I expected I'm in an argument over this

seems that 800 miles and 8 months usage is an acceptable failure point

forget them then, go to the small claims court. regardless of warranty etc, you'll be dealing with an impartial person who'll be looking at it objectively. If they think it is unreasonable for the cat to have fail in 800 miles / 8 months then they'll payout and recover the money from the garage.

Is it the garage/fab shop saying that or a certain manufacturer of race cats?

a car should live longer then that even running leaded fuel!

allanhelen said:

Well as I expected I'm in an argument over this

seems that 800 miles and 8 months usage is an acceptable failure point

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Sounds like bunch a cocks and hate it when this kind of **** happens! fight ur coner till the end

Ming