Greetings from Greece.
Hey guys i need your advice or opinion...
My mechanic at the repair shop told me that i should remove the pre-cat of my TurboII (it has no mods,except a blitz bov).If i do that the car will gain at least 10hp and it will run better.
Is that true???
Should i remove the pre-cat?
Is it safe to do it??
Is there any chance to harm my engine?
Will this affect my mileage?

I thank you in advance.

 

Anyone???

 

It'll help by removing restriction from your exhaust, but you'll still have another cat right after it, so it won't help that much. It'll also have a negative impact on your emissions. It won't hurt the car in any way.

 

I recommend. I took out all of the cats on my FC, and I have been soaking up the benefits. My gas mileage must have increased at least 20-25%. I get well over 200 miles per tank, and I redline it daily. It's great. The only drawback I have experienced, is that SOMETIMES I can smell the exhaust, but it's not that big of a deal. I say take them all out if you don't have emissions. And the HP gains are nice too.

 

yes get rid of the cats but you will need to buy a fuel cut defenser because you will have a less restrictive exhaust you will boost more. Later on you might have to port your wastegate out if boost rises to much

 

Not really. Except for the first few minutes of running after a cold start, the only thing the precats are good for is to clog your main cat. Stupid treehuggers can't even deal with 5 minutes of slightly more polluted running

 

Haha, they make great presilencers, as that's all i've got mine doing at the moment. I knew they don't do much, but not quite exactly how much as I'm emissions free here. Thanks for the info.

 

just got to a shop and pay them like 50 60 bucks to have the fab you a 2 1/5 strait pipe with a couple of flanges. then just take off the muffler with the cats and just bolt on the one with out.

 

Luna is correct. When evaluating the exhaust, a less restrictive one will flow much better which benifits you in the way of increased performance, better gas milage, and an all around better hummmmmming engine. Just make sure you remember how to reinstall the old exhaust system when emission test date rolls around! That reminds me, make sure you have new seals too.....don't want those gases leaking out during test day.

 

I know if you have a FD, it's the first thing you should do. Don't the precats on 'em clog up pretty easy and end up frying the engine?

Would pulling the cats off benefit a NA FC as well?

 

Of course, less restriction = more efficient engine (just don't completely kill all back pressure, as it helps torque) Also, on an N/A the s4's used back pressure to open the aux ports, so be sure to do something about those.

 

Hmmm... it's no good if my ports remain closed. What would you suggest doing aside from having the engine pulled and a nice port job done?

 

Search for the beefy N/A thread (or beefiest N/A) that should give you more than enough pointers. Basically the VDI upgrade on s4 intakes, ported intakes, TB mod, intake/exhaust, advanced timing, ignition boxex, and an s-afc are about all that can be done to a stock engine to get more out of it.

 

if you just have a little air pipe welded to the side of the straight pipe, will that open the 6pi?

 

Thanks guys.

 

I use the bonez 2.5 race pipe, with stock mufflers, and my ports open up just fine. I guess that would be my fear. Just try to find out what mufflers will work, and what won't.