phase 1 decat

[chopchop]

hi first thread so i hope this makes sense lol!!

i got a 172 mark 2 phase 1 what is the difference in lengths on the cats! and can you just get a 172 decat and fit it to the exhaust?

from what i have read on here the single cat is slightly shorter than the other so if i get hold of a longer decat can i just re-mount the whole exhaust system closer to the rear bumper thus the longer decat would fit or does it not work this way? so confused by all this just wanna buy one lol

 

[davebem]

If your 172mk1 has the twin barrelled cat it has the shorter cat. You will need a shorter decat designed for the 172mk1, also to confuse things more the later ones made in 2001 have 2 lambda sensors so you will need a cat with 1 or 2 holes for the sensor depending on your car. If yours is a very late 172mk1 with the same cat as the ph2 then I think its the same length and you can use a ph2 designed decat. You cannot mount the system further up as none of the mounts will reach and it will bang on the rear axle, the difference is about a inch and a half.

 

[chopchop]

ok well after reading that mines an early one twin barrelled but it only has one sensor before the cat coming down the pipe nothing after it! do you no the rough size differnce in lengths of the 2 cats?

 

[davebem]

About a inch and a half!! Youll need a cat designed for the ph1. To fit a normal 172 cat youd need the shorter centre section and a bung for the 2nd lambda sensor hole.

 

[chopchop]

i had already sorted something to bung the hole up with while ago as i had got the decat weeks ago and its just sat in my garage! sorry to be an idiot but are the mounts all the same because if its only and inch and half then surely pipes could get cut and re-wielded? or am i being a r****d on this matter lol

 

[davebem]

You could move the mounts but where the exhaust bends over the rear axle it would foul it moving either way. Have a look behind the backbox and youll see what I mean. The reason why I know so much is because I had the same problem ages ago when i was given a ph2 decat.

 

[pug_92]

if you've got a twin barrel cat and go for a yozza exhaust you need to change to a longer ph2 length cat/decat.

 

[AlexG]

All 172 Manifolds end in the same place though right? The only difference is after the manifold.

 

[Fred@BTM]

yup all 172 manifolds are the same

the twin barrel/twin sensor cat is the same length as the ph2 "box" cat

the twin barrel single sensor cat is shorter in overall length than both of the above