Decat.... Fuel consumption?

[Dan_1981]

Possibly a silly question... but does decatting have any effect on fuel consumption? Either positive or negative.

[MJK 24]

Smidge better on my Elise.

[StottyZr]

Depends on the car, without a remap usually negative I'd expect. I remember looking into it when I owned my Zr 160 and the general consensus was to get a sports cat, as the decat reportedly destroyed fuel consumption.

[Dan_1981]

its an Evo 8.

Remapped and ran without cat in the past.

Cat reinstalled afterwards and not been removed since.

[kambites]

StottyZr said:

Depends on the car, without a remap usually negative I'd expect. I remember looking into it when I owned my Zr 160 and the general consensus was to get a sports cat, as the decat reportedly destroyed fuel consumption.

The K-series VVC is rather unusual in that regard. The engine seems to need a certain amount of back-pressure to operation properly, I never understood why.

Generally speaking, removing the cat should improve consumption as you'll get less exhaust gas left in the cylinder for the next stroke so you'll get cleaner combustion; plus I suppose you waste less energy trying to shove gasses through the rather restrictive cat.

[StottyZr]

Dan_1981 said:

its an Evo 8.

Remapped and ran without cat in the past.

Cat reinstalled afterwards and not been removed since.

So its remapped for no cat?

Take the cat out then!

[GroundEffect]

If your car doesn't have any sensors post-cat then it might be marginally better due to lower pressure drop in the exhaust (higher volumetric efficiency of the engine).

[Dan_1981]

I can confirm *slightly* better.