Decat option....worth it??

[ammo1981]

Any gains or improvement in dropping the cat and placing a straight thru pipe there?? (Standard spec 2000 volvo c70 T5) Any help appreciated

[blackbooty]

hi ammo, before i give my opinions, i must say its illegal to remove the cat from 93 onwards ( i think its 93 anyhow).
that aside i swear by it on all other turbos iv owned, extra horses and faster spool up reducing lag.
i hope lots of other people answer you , cos i also, would like to know how a t5 responds to a de-cat.
wayne.

[pikeajm]

if it is me7 engine it will throw up the lamda light and maybe ten engine managment light best go for a high flow/race cat

[shaun850]

no probs with mine, works well ( noise is superb also ) .

850 t5 saloon

[st1t5]

Im pretty sure in low revs the more freeflow you have you will get more turbo lag as you have reduced the back pressure to the turbo thus taking longer for the turbo to spool, however freeflow is better at higher revs ...

On my turbo'd car (not a Volvo, but im working on it) i fitted a freeflow and i noticed significant turbo lag in low revs, but mid range was slightly better, i ended up fitting the standard system back on and noticed an improvement in low range.

Iv heard of people removing the cat and getting positive gains and then somebody else doing the same thing to the same make and model and not noticing any difference .....

[TwistedSanity]

mines an 1996 850t5, sounds better with no cat, looses traction easier as well

[racer]

You sure about this st1t5? I'd have thought that reducing the back pressure would help the turbo spool up faster. Surely the pressure differential across the turbine bit of the turbo is where the energy comes from to drive the compressor bit? My thinking here is more pressure differential, more energy, turbo can accelerate faster.

Or am I massively over simplifying things by ignoring ECU / Lamda sensor effects?

To go back to the original question, I'd go down the race cat route. You'll probably need a re-map afterwards though.

[Wobbly Dave]

You cant do it with an ME7 engine. I could be wrong but I dont think so. You can do it on the 850s coz the management system is less sensative.
Best option is to buy a race cat e.g. Feritta. You will remain legal too - which in the event of an accident will be important.
What HP figure do you have in mind?

[blackbooty]

Im pretty sure in low revs the more freeflow you have you will get more turbo lag as you have reduced the back pressure to the turbo thus taking longer for the turbo to spool, however freeflow is better at higher revs ...

On my turbo'd car (not a Volvo, but im working on it) i fitted a freeflow and i noticed significant turbo lag in low revs, but mid range was slightly better, i ended up fitting the standard system back on and noticed an improvement in low range.

Iv heard of people removing the cat and getting positive gains and then somebody else doing the same thing to the same make and model and not noticing any difference .....

hi there st1t5, i cant speak with authority about de catting a t5 but i can about saab 9000's and a rover 620 ti that i de cat'd, they both responded with faster spool ups and took off at lower engine speeds.
putting the cats back on for the mot returned them to factory spec and they both seem sluggish by comparison.
my saab 9000 is at full boost by 2.5k.
all said and done, wobblys suggestion of a high flow cat is the best idea if you can afford it, increased flow with the bonus of being legal.
i have a cunning plan to de-cat my 854 , as i have a doner vehicle i will try and cut the top side of the cat off, strip its guts,and weld a same bore pipe inside the cat before welding the lid back on the cat, so it looks original.
dont know if its poss, but ive got a spare so why not.
wayne.

[Wobbly Dave]

Major worry for me is the sensitivity of the ME7 (T3) engine/sensors.

[After_Shock]

Dont de-cat an ME7, been there and tried it, car runs in limp home mode within minutes of re-setting the ecu after taking the cat out, ends up over fuelling terribly aswell so does no favours for mpg even though you are going at half the speed you were before.

A race cat as Dave says is the best option, if the ferrita is out of budget get a custom downpipe made with a universal 200cel race cat in will do the job nicely.

[Wobbly Dave]

"Sum of all the parts" is the thing to bear in mind. The map is key - dropping in race cat on its own will be expensive and I would not be hopeful of any gains?