Welloilbeefhooked

iTrader: (3)

I'm thinking about cutting out the cat in my Zerosports 3" open neck downpipe to increase flow. Although the actual work is a piece of cake, how much of a restriction does this type of catted downpipe cause?

Its listed as a super metal catalyst sports downpipe on their site.

Cheers,

Wayne.

Mike P

From what I understand they get more of a problem the greater total power output you're after.

I have a GGR 100 Cell Sportscat DP, resonated catless centre and H&S Backbox. I recently has a remap at Power Engineering and the peak power and torque are very similar to fully decatted cars that otherwise have the same mods.

Variablity from day-to-day on the rollers due to air temp was probably more of a factor than the cat, TBH.

Mike

DaveW

Would you not be better getting a decat DP and selling the catted one?

Consdiering the price some companies are charging for DP's with sports cats you should make a bob or two.

Welloilbeefhooked

iTrader: (3)

Thought about selling it but decided most people would want a decat anyway.

Its interesting that the power figures are similar to the decats. What power level are we talking about though? I'm looking at 350-380 bhp.

Cheers,

Wayne.

911

All:

Very interested in this thread.
I have an Sti v3 with tons of mods and it recently gave 407 bhp peak at Well Lane.

That was with a decat 3'' semi open neck Magnex.

A week before that the car was mapped by AndyF after all the mods had been done with a 3'' Jap unknown sports cat d/p secondhand from API Engines. Walked the MoT easy, and drove really well. The engine would not hold 1.4 bar (TD 05 20g turbo) over 5500 rpm, and tailed-off to 1.2 at 6800rpm.
Andy and I thought this was the cat restricting flow, but after the '407 run' and fitting the decat, the car seems to drive as if the cat was on.

I think when the car is actually on the road the engine does not run at peak power much of the time, but more 3500 to 5000 so the cat 'restriction' (if there is any) is un-noticed?

I hill climb in competition the car, and it goes well so reluctant to change back to the cat, BUT, it is good to be legal; the cops are after us!

Graham.

Mike P

Hi Wayne

You're looking for a lot more power than I've had my car tuned to (mine's under 300), but Graham's experience would indicate you can get a lot out of a catted engine.

Mike

Welloilbeefhooked

iTrader: (3)

From what you have just posted Graham I am inclined to believe that I may not notice much difference if I do remove the cat.

Does your's now hold 1.4 all the way? I think 1.4 is all I would ask for anyway.

My setup is very similar to yours, but on a WRX engine, not STI.

911

No!

The engine with or without the cat still peaks at 1.4 and tails off. This is why i think the cat makes little difference.

So tempted to put the cat back on and be green and not worry about some do goodder booking me for emissions!

Graham.

Welloilbeefhooked

iTrader: (3)

Do you know what I'm going to do now you have said that?..................

....Wrap the existing catted downpipe and have done!! LOL!

Seems like I am striving for too small a gain with a possibility of failing emmision checks should plod stop me.

Thanks for the advice everyone.

Welloilbeefhooked

iTrader: (3)

Ok, found out that the cat that Zerosports use is a 100 Cell. As far as I know this is the best flowing type of cat to have so its staying in place.

Also, just for Graham, I now have a problem with my boost creeping to 1.3 bar!!

This is all down to a nifty IC duct for the STI8 cooler!!