Hi Guys,

Any of you guys installed cat bypass pipes while keeping the stock muffler? Whats your thoughts?


Thanks

 

A cat delete requires a tune. Usually to get the most out of a tune, a better exhaust is required anyways.

I have a set of 200 cell Fabspeed cats that fit the stock system and *definitely* wake it up while still allowing the stock computer tune to function happily. I'm no longer using them if you are interested in 1/2 price new, whatever that is.

 

Genuine and valid question

If one off the tuners or someone with real world experience can give some input that'd be great

My question is:

By using a cat by pass on the stock muffler what difference is there in performance realistcally compared to using an aftermarket cat less exhaust system apart from maybe the obvious being tubing size, weight and noise?

Surely the stock muffler can't be that restricted once it's been de catted or be any worse or a lot worse off compared to a complete aftermarket catless system?

Please correct if am wrong

Thanks

 

Real world experience.

The stock muffler does have an element of drone in the 350-500hz zone. It's mostly acceptable because the cats are doing a very good job of muffling the system.

With cats changed out for 100 cell or 200 cell/in, ther eis significantly less cat muffling and the drone becomes significant.

Been there, done that.

 

We made some significant increases with the cat delete but I want another car for testing before I advertise them and start selling them. I made 20 sets of cat delete pipes that I have not even started to sell yet. If you want a set I can sell you them for $425.00 a set.

If someone is local and wants to do a set I will give you a free before and after dyno with them. We are located in SoCal.

 

Thanks for the reply guys! I was wondering if removing cats could damage the stock muffler. I'm looking for more noise!

 

No, it will not have any affect on the rear muffler, it will be slightly louder and deeper.

 

Hi Staff

Thanks for your input glad someone who's tried something different can give some input

So just to confirm on the 991 Turbo with the stock muffler you've taken out the O.E cat and installed a de-cat pipe and seen some good gains?

Take it that's after a tune and do you know if there's a lot of difference on these gains over one of the aftermarket exhaust systems?

Thanks

 

+ 1 on those questions

 

I wish I had the answer for you. We tested the gains before and after with the cat deletes and a stock tune to start from zero. The problem with the test is that the numbers were to good and I don't trust them. We tested them when our dyno was fairly new and we have learned a lot about how to make the dyno repeatable and how to use it as a tool for this type of stuff since then. I am waiting for a stock car to come in so I can run these tests again. We are getting our new turbo in a few weeks so I will be able to start with a base on that car and start testing again.

If anyone is in the SoCal area with a stock car and is ready to start modifying their car I can work out a deal for you on some parts and labor to get some extra testing in.

Hopefully I will have real hard data for you soon.

 

Staff thanks for the reply

Do let us know on your findings would be interested to know on the outcome

 

i'm surprised that adults owning expensive sports cars known for their style and elegance are discussing, at length, the volume and quality of their car's exhaust note. one might think it a discussion more suitable for children that put playing cards in the spokes of their bicycles.

 

We're all kids at heart

 

I'm surprised you pulled up a 4 year old thread to pass judgement on what people do to their cars.

 

it's a forum.. a public meeting place for open discussion.
so do you find the association unjust, unflattering or none of the above?