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View Full Version : Cat bypass - running lean?



CJay
08-03-2008, 01:20 PM
Is there any issue installing a cat bypass in the VR-4 on the stock ECU? Is there the potential of running lean? I'm keen to get a bypass pipe in place on the basis that it won't impact on running conditions etc.

CJ

Wodjno
08-03-2008, 03:15 PM
Is there any issue installing a cat bypass in the VR-4 on the stock ECU? Is there the potential of running lean? I'm keen to get a bypass pipe in place on the basis that it won't impact on running conditions etc.

CJ

I take it you mean a Decat Pipe ?

A Decat pipe won't make you run lean ! It won't alter the fuelling at all. And it won't affect the ECU..
What it will do is allow the exhaust gases to escape faster as theres less back pressure and will give a small increase on Mid range Torque on a standard car..There is a benefit on leaning out your fuel mixture though.. It will give you increased power thoughout the rev range.. But you will need some sort of fuel controller to do this, like an S-AFC or an Aftermarket ECU, like a Map ECU or E-manage.

CJay
13-03-2008, 10:24 PM
I take it you mean a Decat Pipe ?

Yup, exactly!

Is it safe to install a decat on a standard Ralliart exhaust? Assuming the baffles in the backbox are mild steel, whats the possibility of blowing them with the increased flow?

CJ

Nick Mann
13-03-2008, 10:29 PM
It's fine. I've done it. Unfortunately, the back box is still a bit restrictive, so you won't see the real benefits until you change that too. Is the exhaust stamped with Ralliart? If so, you may get better gains than I did with just the de-cat......

CJay
13-03-2008, 10:36 PM
Is the exhaust stamped with Ralliart? If so, you may get better gains than I did with just the de-cat......

Yes, stamped with Ralliart but its definetely not SS. 65mm is the standard bore, right?

CJ

jayjay99
09-04-2008, 08:35 PM
Yes, stamped with Ralliart but its definetely not SS. 65mm is the standard bore, right?

CJ


Yes, for the standard 2.5" exhausts and 76mm for the 3" exhausts.