Decat with a standard back-box

[calaerial]

Once again i'm having to change my center section due to a leak from the flexi pipes, and this time ive decided to take it up to Powerflow to have a custom piece fitted.

They're going to fit a piece thats a touch higher so that it doesnt hit the deck as often, and since it was almost the same price i decided to take them up on their offer to make an entirely new middle section with a straight through (decat) pipe.

He said that he wasnt certain about MR2s specifically but that sometimes running a decat with a standard back-box can make the exhaust sound a little tinny. Has anyone got any experience of running this setup?

[deadmau5]

Probably not a good idea as you'll fail your MOT on emissions, and 'blow a hole in your torque curve'.

[manchestermatt1986]

Iv also heard that putting decat pipe without a new ecu makes you loose torque and bhp. Someone please correct me if I'm wrong because iv wondered about decatting myself

[calaerial]

I would imagine that resetting the ECU would cause a retrim of airflow and fuel conditions. And it would adapt to the increased airflow. But thats more of a guess than anything else

[FGrob]

I would imagine that resetting the ECU would cause a retrim of airflow and fuel conditions. And it would adapt to the increased airflow. But thats more of a guess than anything else

You will also keep getting a EML as you have no cat (unless you have a MRS as no third O2 sensor is fitted), you will need either a anti fouler to move the O2 sensor or one of the electric gadgets which does the same thing. Your torques curve will be crap, it will be loud and you will fail your MOT. You will need some kind of piggy back or replacment ECU to gain the benefit, which means a re-map so you are looking at £350 - £450 for the mapping session plus the cost of the ECU mod.

Rob

[markiii]

I would imagine that resetting the ECU would cause a retrim of airflow and fuel conditions. And it would adapt to the increased airflow. But thats more of a guess than anything else

nope you will bugger your torque curve, fail an mot and have a permanent check engine light

[calaerial]

Yeah looking like i'm going to be better off getting them to adapt the existing cat, he seemed to indicate he could perform a similar modification to the elbow/flexi piece of the pipe while retaining the cat, and that it would actually be marginally cheaper (about £150, from £185)

I'll give them a ring tomorrow and confirm this is the case and do that. Dont want to create another massive workload for myself, the car has already had £700 out of me this month. Just figured if it was easy enough done it was worth getting it done all at once. Thanks for saving me from a fairly substantial  scock cock scock -up.

[dan_daran]

hi having recently just decatted , (i also have a che manifold and tte backbox) i do prefer the way the engine "feels" like its outputting its max more of the time not esp after removing the airbox piipe, now maybe it does loose a bit of torque but its just more fun to drive like youre connecting with the engine better

[Anonymous]

I would imagine that resetting the ECU would cause a retrim of airflow and fuel conditions. And it would adapt to the increased airflow. But thats more of a guess than anything else

You will also keep getting a EML as you have no cat (unless you have a MRS as no third O2 sensor is fitted), you will need either a anti fouler to move the O2 sensor or one of the electric gadgets which does the same thing. Your torques curve will be crap, it will be loud and you will fail your MOT. You will need some kind of piggy back or replacment ECU to gain the benefit, which means a re-map so you are looking at £350 - £450 for the mapping session plus the cost of the ECU mod.

Rob

im fully decatted with an ecu and ok bigger engine but i still say my idel  is because it hates the fact there is no cat and trying to compensate. also looking at an old dyno for my engine to my current one i got a hole in the max torque by 20 - 30. now that is alot.

[calaerial]

Just got it back from PowerFlow, kept the cat in the end.

The new piece makes a hell of a difference to the sound of the engine, i think the old one had been blown for a lot longer than i realised, possibly the whole time its been on because the engine has never sounded this healthy before. It might be my imagination but it also seems to have changed the character of the engine somewhat, perhaps its the slightly different configuration, perhaps its just restored it to what it should have been before it blew but the car feels much more eager. Torquier somehow.

Either way, £160 well spent.

[Maz_craft]

Hi bud, just wondering what did you get done in the end? Just a backbox or downpipe and backbox

[shnazzle]

Just so you know... This post was from 2011  s:) s:)  A response is unlikely. But from the looks of it the replacement was for the cat. So the part between manifold and back box.