De cat or not de cat that's the question

[Lee987lee]

I've just about sorted the brakes on my civic type R.

I'm now looking at the airflow system and thinking about putting on a manifold decat and full s steel exhaust. I've been told a decat will loose power as they need the back pressure
does anyone know if this is correct or what's the best to do?

Thanks Lee

 

[taylor]

Hi their its a fact you need back pressure, but most good makes of decat manifolds are designed to flow more gasses, but still allow for these pulses to continue, to gain real response from it, a remap is the best route to take.

Its worth taking this into account.

Taylor

 

[Shoonk]

It should give more power but you'll need to swap it for the MOT plus I think you'll need a different o2 sensor so your management light won't come on. For optimum gains you should remap as well.

 

[Hazz]

If it's for road use, do not decat. It is illegal. In order to pass an MOT you need a cat. A VOSA check on a decat car could result in hefty fines and even impounding or crushing your car.

If it's for track use, then sure, decat it. As said, you will need a remap to see any real gains.

Also, just for completeness.... What that guy said about back pressure isn't true, it's a commonly held myth that all engines need back pressure when the fact is they just flat out don't. It's something lots of people like to talk about when exhausts and manifolds are mentioned, because it sounds clever. You cant deny the correlation between increasing bore sizes of mainfolds and exhausts can (when taken to extremes) reduce power and back pressure, but it is wrong to assume it is the back pressure reduction that is causing the engine to lose performance. The idea, to create the best performing pipes is to create the most efficient laminar air flow with the lowest friction so that the engine can expell gasses at its optimum rate, now increasing a bore size dramatically will both reduce back pressure (irrellevent) and create a turbulant airflow (relevent) because insufficient pressure & volume is created by the engine to push the air at the required velocity to acheive a laminar flow. The counter argument is that the back pressure helps to seal the valve, but if your valvetrain is sprung propperly this should never happen (as proven by David Visards tests). Backpressure is actually counterproductive, a perfect engine would have zero back pressure but this is not feasably possible as it is a byproduct of creating a pressured laminar flow.

Engine physics lesson over.

 

[Lottie]

Also im pretty sure in the EP3 (not sure on FN2) its pretty much pointless unless you get a K100/KPRO.

 

[Ed]

Also im pretty sure in the EP3 (not sure on FN2) its pretty much pointless unless you get a K100/KPRO.

Flashpro for the FN2

 

[taylor]

What the other guy said....over bore is proven to lose power.

This is not an issue in regards to a turbo set up. A good two and a half inch system will keep you right.

If you want to take a chance with the law its up to you.....



Taylor