So first of all does a decat do any significant damage to the turbo, loads of people have them but I have seen it makes the turbo over spool or something and therefore damaging.

Would I need to remap my car after a decat (already has a revo map @ 175bhp)

People drill then knock out the cat to have the decat with the cat still in place, can I do that whilst on the car?

I believe taking the cat out can cause overboosting which will damage the turbo, to check this you could do a group 11 log on WOT and if it is overboosting the map will need to be tweaked to suit

What ive done is buy a decat pipe someone made bu chopping the cat off and welding a pipe in its place. im then going to put a cat shell around the pipe so it looks as if its still there but the gases can go straight through

I believe taking the cat out can cause overboosting which will damage the turbo, to check this you could do a group 11 log on WOT and if it is overboosting the map will need to be tweaked to suit

What ive done is buy a decat pipe someone made bu chopping the cat off and welding a pipe in its place. im then going to put a cat shell around the pipe so it looks as if its still there but the gases can go straight through

Group 11 log WOT? Sorry don't know what you're on about can you elaborate haha!

If I drill and knock it out well, then it will be the same without chopping or welding the original down pipe?

He's saying you need to hook the laptop up and do some flat out runs to see how the turbos boosting on the diagnostics.

As for removing the cat, I'd like to know myself.

I wouldn't drill it personally, I'm tempted to stick a pry bar down and hammer it a few times in different places.

I'd definitely take it off the car though.

Yeah the original map on the car counts on there being a certain amount of back-pressure on the exhaust side. without that restriction in place the turbo spins more freely resulting in boost spikes until the map adjusts the turbo to reduce the boost. It can result in turbo damage so best to get it remapped straight after.

 

Your best options are as above. Either weld in a straight pipe and weld the casing round that to make it look like it's still there or remove the exhaust and bash it's innards out!

Yeah the original map on the car counts on there being a certain amount of back-pressure on the exhaust side. without that restriction in place the turbo spins more freely resulting in boost spikes until the map adjusts the turbo to reduce the boost. It can result in turbo damage so best to get it remapped straight after.

Your best options are as above. Either weld in a straight pipe and weld the casing round that to make it look like it's still there or remove the exhaust and bash it's innards out!

The exhaust comes apart right at the cat, could I not just have it on the car and get some long drill bits to weaken it all then bang down it, then Rev the car to blow **** out?

Try it and let us know.

I'm sure you can do that yeah but for the sake of 3 bolts you could have it on the floor or on a work bench etc.

The exhaust comes apart right at the cat, could I not just have it on the car and get some long drill bits to weaken it all then bang down it, then Rev the car to blow **** out?

Its only 3 bolts to undo thE downpipe from the turbo and then the whole pipe will drop down. Youll probably still be left with a load of crap that wont get blown out and it will rattle like a b*****d if you dont drop it out

Also wondering what the effect will be on flow having a large expansion area mid down pipe. A proper decat pipe will maintain diameter, a smashed out one will open up then bottle neck.

Also wondering what the effect will be on flow having a large expansion area mid down pipe. A proper decat pipe will maintain diameter, a smashed out one will open up then bottle neck.

Ah yes the guru speaks.

Guess it will have to come off, can you get a pipe that tightly fits inside 2.25?

I seem to recall hearing people say it increases exhaust noise slightly due to it being a hollow space.

Ah yes the guru speaks.

Guess it will have to come off, can you get a pipe that tightly fits inside 2.25?

 

2.24

I seem to recall hearing people say it increases exhaust noise slightly due to it being a hollow space.

 

Not true in my experience, instead of buying a cat back I chopped my exhaust up, took EVERYTHING out of the backbox and welded it back up.

It was just a silent as before, all it did was put a bit of black smoke in start-up and if you put your face at the exhaust a slight whilst and thast with 175bhp REVO map.

 

Since, I got annoyed I wasted my time and effort and chopped a hole in the bottom of it, needless to say it's mutilated but throaty.

 

Asking around now for prices on a custom cat-back to be professionally done.

Then I might end up sleeving a pipe in place of cat for the sake of a £10 decent sleeve, so I can sleeve cat back on for MOT.

Not true in my experience, instead of buying a cat back I chopped my exhaust up, took EVERYTHING out of the backbox and welded it back up.

It was just a silent as before, all it did was put a bit of black smoke in start-up and if you put your face at the exhaust a slight whilst and thast with 175bhp REVO map.

 

Since, I got annoyed I wasted my time and effort and chopped a hole in the bottom of it, needless to say it's mutilated but throaty.

 

Asking around now for prices on a custom cat-back to be professionally done.

Then I might end up sleeving a pipe in place of cat for the sake of a £10 decent sleeve, so I can sleeve cat back on for MOT.

 

I was lucky and found a pipe on ebay that someone had already chopped and welded up so all I need to do is add a shell. means I can keep my proper cat in the shed just incase.

I was lucky and found a pipe on ebay that someone had already chopped and welded up so all I need to do is add a shell. means I can keep my proper cat in the shed just incase.

 

How much is a second hand downpipe? 

 

I've posted on here for one, if I can get one I can chop and weld it myself and switch the whole downpipe over like you.

Mine cost £50 which is £100 cheaper than a proper miltek. but no idea on the average going price tbh

I have a standard downpipe for sale for £30 if anyone wants it

^^^ Problem sorted

So first of all does a decat do any significant damage to the turbo, loads of people have them but I have seen it makes the turbo over spool or something and therefore damaging.

Would I need to remap my car after a decat (already has a revo map @ 175bhp)

People drill then knock out the cat to have the decat with the cat still in place, can I do that whilst on the car?

I got my map tweaked after fitting decat.

Just for extra peace of mind. They explained that it did need to be adjusted.

Didnt cost much as got original remap from shark anyway so they gave me a good deal.

Try going to the revo dealer you got your map from they should give you a good deal. Returning customer and all.

Me and mate got our cars mapped together but he says mine seems faster,

Probably the slightly quicker spool with decat & map adjustment.

But who knows??thats where the fun is. Lol