Full decat / or 2nd decat ?

I was planning to fully decat my TT but then considered the pain in the a*se issue of putting it all back for MOT purposes, If i fully decat I know will need a restrictor ring in place, what about if I only remove the second Cat ? Will I need one then ?

Iwhat about if I only remove the second Cat ? Will I need one then ?

No. But if you're only taking one cat out, remove the first one as it's more restrictive. You still won't need a restrictor ring.

Cheers mate !Thats a bugger though as the 2nd one is easier to get too !

No. But if you're only taking one cat out, remove the first one as it's more restrictive. You still won't need a restrictor ring.

If its anything like mine he will

I was hitting 1.3-1.4 bar with the first cat out and the 2nd cat still in without a RR

If its anything like mine he will

 

I was hitting 1.3-1.4 bar with the first cat out and the 2nd cat still in without a RR

Thats more than the 1.2 bar recommended, if thats the case with one cat out whats the point in removing both ?????????????

less restriction = lower EGT's and quicker spooling

I prefere with 1st cat in. Nicer sound and better drive.

If its anything like mine he will

 

I was hitting 1.3-1.4 bar with the first cat out and the 2nd cat still in without a RR

I had to mess about with rr sizes for days and Iv got mine to a steady 1.1-1.2 bar now. The second cat isnt that resrictive so like us you will probably need a rr aswell if you remove the first cat (which is the one you want to remove for more performance)

A mixed view then !

If I do a full decat then what size RR would you recomend ? at least I can get an idea of where to start with it.... everything else on the engine is standard at the moment, although I will be looking at a basic BPU very soon.

I prefere with 1st cat in. Nicer sound and better drive.

What? Thats the complete opposite of what should be done.

The first cat is the most restrictive and the one that should be removed BEFORE raising boost pressure. The last thing you want with raised boost is a bloody great restriction a few inches away from the manifold.

To anyone thinking about removing a cat, replace the first one first. Do not leave it in place with raised boost.

oh and Lucifer, if you continue to post this sort of crap in tech, take a walk. Almost everything you've posted in tech in the last week or two has been wrong or misinformed.

I have a comparison graph I plotted from the dyno.

Both runs at 1.1bar, one with the first cat still in place and one with a full decat with a restrictor ring to get me down to 1.1bar.

The results speak for themselves. I'm not at work so do not have a scanner but will see what I can do with the digi cam.

I like the double decat approach but I do find the boost curve and power delivery is a little less savage with the Nur Sec baffle in place as well. This drops the boost a fraction but makes things a little smoother, less savage and more predictable on the road.

Go full decat mate with a 1bar restrictor ring (if you're planning on getting a boost controller to raise the boost to 1.2 when needed for the more spirited drives), or save the hassle and pop in a 1.2 CW RR instead.

Find a friendly MOT tester, there's plenty around

Find a friendly MOT tester, there's plenty around

could do with finding one near Stoke

If its anything like mine he will

 

I was hitting 1.3-1.4 bar with the first cat out and the 2nd cat still in without a RR

There seems to be a big difference between cars as I had the opposite. With double decat and a 1.25bar RR I only got 0.7bar!

Attached is the comparison I mentioned.

1.1bar with the 1st cat still in place.

1.1bar with no cats but with a suitable size restrictor ring.

Clear performance benefits are there to be had!!

Things should run a little cooler and the car will be a little louder.

Thats quite a difference in power for the same boost without the cat compared to with the cat in. I wonder how that compares to leaving the second cat in as its less restrictive. Good post

So what were saying is that you can put the second decat in leaving the first cat in place and you will not do any damage or melt anything?

Decat it fully or take a Sports cat if you want to have a cat. The stock cats are both very restrictive and things will get hot.

Canislupis, what things will get hot if you only take the second cat out and what damage could be caused?

Trying to get a definitive answer to this thread......

I've been told by lee p that it's ok and am inclined to respect his opinion on this

Canislupis, what things will get hot if you only take the second cat out and what damage could be caused?

 

Trying to get a definitive answer to this thread......

 

I've been told by lee p that it's ok and am inclined to respect his opinion on this

How can it make it hotter if you are removing the restriction i.e. the cat. If anything it will make things run cooler as there is less restriction in the exhaust, remember if you remove the first decat you will need a restrictor ring to prevent your turbos overboosting. They can be had from most of the traders on here. I think canislupis is misinformed.

How can it make it hotter if you are removing the restriction i.e. the cat. If anything it will make things run cooler as there is less restriction in the exhaust, remember if you remove the first decat you will need a restrictor ring to prevent your turbos overboosting. They can be had from most of the traders on here. I think canislupis is misinformed.

He seems right to me. If you leave both cats in and up the boost, there will be a lot of heat produced.

How can it make it hotter if you are removing the restriction i.e. the cat. If anything it will make things run cooler as there is less restriction in the exhaust, remember if you remove the first decat you will need a restrictor ring to prevent your turbos overboosting. They can be had from most of the traders on here. I think canislupis is misinformed.

I've never said to remove the decat oO

If you read my post carefully i said to decat fully or IF NEEDED replace stock Cat(s) with a Sports Cat(100cpsi or so). I've got the first cat still fitted and Blitz second decat EGTs rise up quite fast @1bar and stay around 950-980°C on top speed runs and hard pulls. Didn't try 1.2 and i won't until i've removed 1st cat and an 100cpsi in place. I personally wouldn't run it above 1 bar with either Stock cat fitted but maybe wrong with that as i can't try running just second.

He seems right to me. If you leave both cats in and up the boost, there will be a lot of heat produced.

I've never said to remove the decat oO

If you read my post carefully i said to decat fully or IF NEEDED replace stock Cat(s) with a Sports Cat(100cpsi or so). I've got the first cat still fitted and Blitz second decat EGTs rise up quite fast @1bar and stay around 950-980°C on top speed runs and hard pulls. Didn't try 1.2 and i won't until i've removed 1st cat and an 100cpsi in place. I personally wouldn't run it above 1 bar with either Stock cat fitted but maybe wrong with that as i can't try running just second.

Who mentioned upping the boost he only talked about the removing the second decat

I don't think he has helped by reviving a thread over 4 years old !!!

Create a new thread like you should have in the first place and state exactly what you want to know .....