Surely sport cats gonna be a lot better than two std cats ??
And to get good std cats probs cost just as much??
My original plan was to just fit 3.0 downpipes and move lambda but i thought for a decent price i can have atainless downpipes mandrel bend with two magnaflow 200cell sports cats in them.. why would this not be better??
I'm not really an expert in the dynamics of these engines but my opinions are those of a bloke who has owned both the 3lt and the 3.2
Tuning wise, without forced induction (turbo or supercharging) there is not a lot more power to be gained but you can make them a little more driveable .
I personally prefer the feel of the 3ltr engine but if it did have a problem, it was with the downpipes which was cast not tubular and definitely was a choke point with the exhaust gasses.
The DBW engines cured this with tubular manifolds which are iirc good for much more then the 210 bhp ish that the 3.2 will kick out even on a good day so imho, i'd leave the standard 3.2 manifolds alone
If you look at the physical difference between the 3ltr and 3.2 cats, you will see that the 3lt one is quite a bit larger then 3.2 one and is constructed must better so not only do they breath better but also last much longer too hence some lads on here (including myself) have modified the old cats to take both lambda sensors once the DBW pre cats start to fail and fitted them to our DBW engines
I can confirm that it does make it a little more driveable
Right, the DBW engines bad bits ...........
To get the DBW engine threw the yanks market emission tests, they have to choke it up with the precat and also reduce the compression
If you remove the 3.2 heads and fit a pair of heads off a 2.6 c/w the 3.2 valves and do a little porting in the inlet manifold area, not only will you raise the compression back upto around the 3ltr but you will also have more torque due to the extra capacity and greater drivability of the larger and more solid cats
I understand what you mean about the aftermarket sports cats but with the 3ltr cats been so durable, it isn't really a problem to use a pair off a scrapper and with the sensor bosses fitted, I would think it would be better in the long run
Exhausts .........
I would say that the standard size one would be more then good enough for the amount of gas that the 3.2 will kick out.
Fitting a nice clean new cat back system will cost you about 100 quid so unless you really want to spend money on a stainless or to change the tone then i'd go down that route
Also bare in mine that these engines do need a little back pressure to give maximum output and tinkering too far from the original setup will probably loose you some lower end torque which is the last thing you want on a 2 ton car