straight6

Anyone have experience bypassing both the cat and the muffler? I was wondering just how loud it would be? Loud is ok, just do not want that terrible highway low mind bending harmonic... I was originally thinking of just doing the cat...
Also, what about correct back pressure? Don't want to sacrifice HP for a little extra growl...

Thanks

69COU

Do the Cat only if possible, Doing both will for most people be too loud

Vince5

I called RUF when I was doing some enquiries before starting to mod the car. They told me they had dynoed the same car with and without the original muffler. Without the muffler the car had lost 15 hp.

Go for the cat bypass or like I did, if you have to pass emission test or if the car has to be equiped with a cat, buy a race cat (it does work but the car is more quiet).

straight6

Thanks guys

ian

I would really like to see dyno proof of this, something else must have been going on in the exhaust system, unlike a NA car where some restiction in the system helps you make more torque, and must be used to make ideal hp depending the cam profile, with turbo charged cars the easier it is to get the air out from behind the turbo the more quickly it should spool and in most every application I have seen the cars normally make a little more hp as well..... Or a lot more depending on other factors.

Vince5

It does sound strange but the salesman I had on the phone was positive about it. Of course he is a sales guy, being one myself I know sales people always tell you the truth .

My car didn't have the muffler on last year and I found I did not have the power advantage I should have had against athmo cars. Of course it may be because of 100 other reasons !
Last week the car with muffler (put it on because the car was to noisy for DEs) 0,85 in boost and race cat was as fast as an M3 CSL on the straight . It doesn't mean anything regarding with or without muffler perf but I was so proud of her I had to write that down somewhere

cobalt

Go to the Fabspeed site they have a great little video of what they feel works best. One option is the G pipe which replaces the factory muffler. I have this done to my car. It sounds better and feels like a little less back pressure. I doubt there is any HP gains.

The other is the cat bypass using the factory muffler. They claim the factory muffler is better than the aftermarkets and all it does is tone down the sound. Not very restrictive and works well without the cat adding about 22 hp. I have also heard from people that the car can pass the sniff test without the cat. I don't know if that is true but it may be worth a look.

When I spoke to RUF they claimed they had a pipe to eliminate the muffler on the 3.3 L engines that increased HP by 15. They said they had nothing for the 3.6 as it does not make any HP changes.

Curious.

straight6

Everyone should just dyno their cars!! I have a feeling that the horsepower gains
from all these mods are not so significant. (less than everyone thinks) Horsepower is not the most important piece of the puzzle anyway. It's really more about torque and turbo lag with these cars. Right?

Vince5

Yes it's all very confusing and you are right about the turbo lag. The best mods are cat bypass, and quality CBV I think.

cobalt

I agree that when I installed the New CBV the car appeared much faster. The HF turbo and headers reduces lag which gives you hp earlier and maintains it longer and that is most important. It would be nice to increase torque, however you will have a hard time increasing torque with the factory cams.

The cat bypass is the way to go, however they check for cats in Jersey. I think the 100 cell cat may be the best compromise.

Vince5

I have the CarGraphics race cat. Tested it this week-end on the track it works great to reduce lag. I can recommand it to whoever wants to upgrade and is required to have a cat on his car.

cobalt

Vince,

How much of improvement does the new cat make? Do you feel the improvement warrants the expense? Is it a direct bolt on installation?

Vince5

I think it makes a huge improvement (off course I did other things at the same time so it's hard to isolate the effect of the cat alone).
Now the turbo starts to load even before 3000 rpms, it was more like 3700/3800 before, and off boost throttle response is greatly improved. It makes life much easier on the track.

I think it's a bolt on but since I didn't do anything myself I am not sure. I haven't received the full bill yet for all the mods but this one cost roughly 1200 USD. In my mind it's all worth it even if it's cheaper to buy a simple bypass or to open your cat and remove everything inside.

On the other hand if you like you cars brutal you may want to stay stock with the OEM CBV

emilios

Vince5,

how does the Cargraphic sports Cat affect sound?

Also, I'm quite surprised that your turbo used to start boosting at 3700/3800 - I think that was quite high.

Mine (which is factory standard - apart from an adjustable Hyperboost CBV and a sports secondary muffler) starts to boost at approx. 2700-2800, and I think I have full boost (0.7) by 3400-3600rpms.

Best regards

Emilios

Vince5

I always drive the car myself so I don't know how it sounds I used to get a lot of comments about how loud it was with standard cat and no muffler last year but so far this year with race cat and standard muffler back on I have only 1 comment saying the car had a nice loud sound. So nothing to impressive I think.

I kid you not, before the race cat and Forge CBV the car went from 0 boost to full boost between 3500 and 4000 rpm approx and off boost perf was poor. I changed both at the same time.