exhaust, ecu change??

[Simaroon]

my fd is totally standard at the moment, however i have a 4 inch jap can thing fd exhaust from the cat back in the shed which im tempted to put on it, just because it looks cleaner than the standard rusty box really.
 
would i need to change the ecu even if im not replacing the cat, just from the cat back. or could i get away with putting the exhaust on,
 ive read a few horror stories of running lean and ruinin air flow etc while searching any airflow mods.
 
thanks

[AtomicRex]

Always best to be safer than sorry! Are you running a PFC?  Just realised You arent...should read posts!  I have a piggy back ECU if you are looking for something cheap?
 
Sorry about the lights....slipped my mind as Ive been flat out! Do you still need them?

[Simaroon]

not running a pfc or anything, no extra gauges, just totaly stock fd type r. so you would advise against fitting the back box.
 
i would still like a pic of the lights if you didnt mind, still interested in buying them yes.

[trotter]

the problem with fitting new exhausts / intercoolers / decat, etc is that they help breathing of the engine both in and out. IIRC the stock ECU can\'t compensate and you will get boost creep / spike and a good chance of running lean = BANG!

graeme

[Simaroon]

yes, thats what ive read into and it has worried me alittle, on the hand ive seen people say they run air filters and exhaust without a problem, just dont replace the cat.
this is what i wanted to clear up.

[Speedline Imports]

If your car is completely standard and you just want to put a cat back exhaust on, the standard ECU is fine.  Putting on a piggy back ECU wouldnt be a great idea as it will be from a different car with different modifications.  If your modifying the car further look into an Apexi PFC, HKS Fcon "Gold version", Motec etc.

[Simaroon]

thanks for the reply. yes powerfc is on the list and dont want to bother with piggy backs etc. its just as i had the exhaust alreay lying around its been frustrating me not putting it on.
so aslong as i keep the cat on, and only replace from there back, with no additional filters etc it should be fine,
sorry for the repetitive questioning, its just this rotarty engine makes me paranoid, and ive only owned it a fortnight.

[trotter]

thanks for the reply. yes powerfc is on the list and dont want to bother with piggy backs etc. its just as i had the exhaust alreay lying around its been frustrating me not putting it on.
so aslong as i keep the cat on, and only replace from there back, with no additional filters etc it should be fine, sorry for the repetitive questioning, its just this rotarty engine makes me paranoid, and ive only owned it a fortnight.

seems logical to me.

If you are interested in the reasoning why de-catting on a stock ECU is \'a bad thing\'....

Basically, turbo(s) work by increasing the mass flow of air through the engine. More air = more fuel = more power. Now, the exhaust flowing through the hot-side of the turbo (i.e. from the engine) has a certain pressure on both sides of the turbo. It\'s this ratio of pressures that determines how much work is transferred to the cold-side (incoming air) via the compressor turbine. The exhaust pressure leaving the turbo is not (counter-intuitively) a result of anything the turbo is doing, rather it is a result of restrictions to flow in the exhaust system (pipe bends, cat, silencers, etc). Think of it this way: with more backpressure to overcome and get the exhaust gases out the back of the car, there is less work \'energy\' available to transfer.

So, if you remove the cat, you remove up a rather large restriction from the exhaust, thus the pressure differential over the turbo is much greater, and thus more work can be transferred to the cold-side. This consequently leads to more air getting in to the engine. However, the stock ECU can\'t compensate outwith a certain range and thus you will have more air going in, but not the corresponding amount of fuel to keep things good = lean = BANG!!

hope that makes sense and helps a bit!

graeme

[m1tch]

I would definatly buy a mechanical boost guage to check there isn\'t any boost creep.