in antisipation of the catless 3.0 results what are the 4.2 results

B6/7 S4/RS4
#1

I can see how bad the catless dp’s are on the 3.0 but I don’t know performance wise other then they look like there killing the car. on the 4.2 I know its a n/a motor and Im thinking that there is some decent performance gain from going catless Vs. just precat.

The 3.0 reallty dosn’t have room to gut the pre and leave the main cat so basically were jumping from full cat to cattless how big of a difference is this in the 4.2 world.

Also were going from 2.0" or just under to 2.5

so were going from 2.0 fullcats in the precat location to 2.5 catless any idea on if this bigger pipe will go well and if there is really a gain to be had just ditching the cats

Thanks to all of our bigger brothers in the S4 for there input hey even the RS4 guys can chime in

#2

From what I know the v8 s4 cars have made power without touching the exhaust and made more with piggies, then more on top of that with a tune. The 3.0l wouldn’t budge an ounce of power due to the pre-cat and main cat ( total of almost 11" of cat right after the headers) being super packed tight and more restrictive then the v8 cars, Ive seen both and its obvious that these were meant to really keep emmisions down.

The b6 a4’s 3.0l were made to not be a performance car where as the s4’s were. Different design for different purposes.

the stock piping is about 2’’ on the b6 a4 3.0 DP.

As far as gains when you ditch the cat. Oh yes! very much so.

#3

The 3.0 cat really is killing the 3.0 just as much as the 4.2 precat does. Rod said it all for me. thanks rod glad to have ya

#4

Yup, anytime. Glad to be on board.

#5

I spoke about this on the other thread. I feel that there is going to be a tremendous amount of power to be had by removing both the cats on the 3.0. The 4.2 is a much bigger motor so its going to see a nice size gain with the pre cats removed. The 3.0 is a smaller motor but with two cats stacked one on top of the other I don’t see how removing them wouldn’t bring great results

#6

Torque, plain and simple. I came from piggie pipes and I was STUNNED how much torque I picked up going from piggie pipes to true 2.5" catless dp’s. The torque and completely different sound were the two most noticeable factors. The sound is significantly different from piggies, and piggies give a nice bump in growl over stock, but the catless just sound mean.

I really think 2.5" catless + magna flow 2.5" catback and the JHM ECU & TCU tune is going to shock all of you all. I’ve got no dog in this race, and I’d love to see a nice JHM 3.0 go up against a stock S4 just for comparison. The S4 should still beat it, but even being in that race is pretty notable considering where the 3.0 was starting from.

#7

Good to hear. Based on that, IMHO I’m probably going to save my nickels and dimes to do proper downpipes (when they are released) and have a custom exhaust built locally to get the most out of the exhaust. And I know a couple stock b6s4’s that would love to try that matchup ;D

#8

I need to go full 2.5"" exhaust, mine is still super quiet and its driving me nuts haha!