[Dr. G]

So I want to add my Downpipes back on, but I chose to run with one set of cat's at all times. I took my car into the shop to get a set of high flow cats welded into my Vanguard Catback setup, but they said there was nowhere to put it unless I remove the Resonators and put the cats into the place of the resonators.

Now my concern with this is how much raspier would the exhaust setup get? I know removing the resonators will definitely induce some rasp, but will a set of high flow cats be able to keep the rasp under control?

If anyone has done something similar their input would be greatly appreciated.


ORRR.... would just going with a set of catted downpipes be a better idea? The goal of this setup is for Pure sound enhancement and not performance.... I have the catless AR's for my performance needs

[Transport3r]

Do you have vanguard midpipes?
If not, since you have an E92 there is no resonator on the stock midpipes.
Those are the secondary cats. Replacing them with high flow ones will change your sound a bit, but not much from what i've seen. most people do it for performance.

[Dr. G]

Originally Posted by joshuo

Since you have an E92 there is no resonator.
Those are the secondary cats. Replacing them with high flow ones will change your sound a bit, but not much from what i've seen. most people do it for performance.

I have a Vanguard catback not OEM.

[Transport3r]

yea saw that, lol. it's late, reading comprehension fail.

[tibra1]

Catted DPs are not worth it IMO..ur always better off removing the restriction in the downpipes..rasp, drone etc are a function of the mufflers more than anything..w that said rule of thumb is:

HFCs help drone
Resonators help rasp

You should prolly run both if your set on keeping the Vanguard

You might also wanna look into Vibrant resonantors they make some application that are slim enuff and work w the tight space u have

[Dr. G]

Yeah, I just don't see the benefit in the catted DP's since the restriction right after the turbos is still there... so I never really considered them much.

I don't really notice any annoying drone I'm just adding the HFC's for emissions reduction... but I am worried about the Rasp that deleting the resonators might cause.

If I were to run both I would have to do a MAJOR hack job on the exhaust... first I'd have to cut the resonators out and weld in HFC's... and then I'd have to cut another area of the exhaust and weld in some vibrant resonators (which I know work magic for rasp) so that start's to become a bit too expensive with the labour involved.

Getting the exhaust system perfect on this car is proving to be quite a pain in the ass.

Originally Posted by tibra1

Catted DPs are not worth it IMO..ur always better off removing the restriction in the downpipes..rasp, drone etc are a function of the mufflers more than anything..w that said rule of thumb is:

HFCs help drone
Resonators help rasp

You should prolly run both if your set on keeping the Vanguard

You might also wanna look into Vibrant resonantors they make some application that are slim enuff and work w the tight space u have

[tibra1]

Originally Posted by Dr. G

Yeah, I just don't see the benefit in the catted DP's since the restriction right after the turbos is still there... so I never really considered them much.

I don't really notice any annoying drone I'm just adding the HFC's for emissions reduction... but I am worried about the Rasp that deleting the resonators might cause.

If I were to run both I would have to do a MAJOR hack job on the exhaust... first I'd have to cut the resonators out and weld in HFC's... and then I'd have to cut another area of the exhaust and weld in some vibrant resonators (which I know work magic for rasp) so that start's to become a bit too expensive with the labour involved.

Getting the exhaust system perfect on this car is proving to be quite a pain in the ass.

I feel ur pain and really this was the main reason I went w the AE..its not the loudest exhaust out there but I am fully catless-no resonators.. w/o a hint of rasp or drone...their mufflers are really kick ass..

[Brey335i]

I looked again today. There's definitely room for the D shaped HFC's in the midpipe section. I might go this route

[Dr. G]

Originally Posted by Brey335i

I looked again today. There's definitely room for the D shaped HFC's in the midpipe section. I might go this route

Wouldn't you run into some ground clearance issues with this setup? Let me know if you do go this route since I'd rather keep those resonators in there.

[Dr. G]

Originally Posted by tibra1

I feel ur pain and really this was the main reason I went w the AE..its not the loudest exhaust out there but I am fully catless-no resonators.. w/o a hint of rasp or drone...their mufflers are really kick ass..

The Problem is I don't want to be fully catless... otherwise I have two possible setups I'd be running.

Catless Vanguard
Catless BMW PE with Vibrant Resonators

These two systems sound absolutely AMAZING.... but the problem is finding room for those HFC's.

[Brey335i]

Originally Posted by Dr. G

Wouldn't you run into some ground clearance issues with this setup? Let me know if you do go this route since I'd rather keep those resonators in there.

There's extra space on the sides and it wouldn't hang down any lower than the stock cats.

[Dr. G]

Originally Posted by Brey335i

There's extra space on the sides and it wouldn't hang down any lower than the stock cats.

Damn, doooo it then take pics and show me where you put them haha, I need to settle this exhaust dilemna and move on haha.

[Bullet]

def post pics.. I'm thinking about doing the same

[Dr. G]

Originally Posted by Bullet

def post pics.. I'm thinking about doing the same

I don't wanna be the first to cutout the resonators haha, might end up being stupidly raspy and then I'd be spending more money buying resonators and somehow welding them in.

[nailer335]

To revamp an older topic here...

I already have CL DPs and will be keeping the OEM catback exhaust, but I want it to be the least restrictive it can be and was considering throwing in some high flow secondary cats in place of the stock secondary cats on the stock midpipes. Is anyone doing this? If so, how are the results, if any?

[bigdnno98]

I may do the same thing. Ill post a vid if I do.

[bigdnno98]

Ok I think I've decide to pull the trigger on some high flow cats. Any recommendations? Does anyone know the dimensions of the stock cats?

[nailer335]

(clearly) interested in doing this as well. There are probably minimal gains to be had in replacing the stock secondaries with higher flowing cats.

Who has done this people? What did you put on your car? How does it compare? Cost, source, anything else relevant?

Bueller...

[nailer335]

Really? No one?

[marcvtec]

Originally Posted by nailer335

To revamp an older topic here...

I already have CL DPs and will be keeping the OEM catback exhaust, but I want it to be the least restrictive it can be and was considering throwing in some high flow secondary cats in place of the stock secondary cats on the stock midpipes. Is anyone doing this? If so, how are the results, if any?

This is the route I am going to take as well

[Dr. G]

Originally Posted by nailer335

To revamp an older topic here...

I already have CL DPs and will be keeping the OEM catback exhaust, but I want it to be the least restrictive it can be and was considering throwing in some high flow secondary cats in place of the stock secondary cats on the stock midpipes. Is anyone doing this? If so, how are the results, if any?

It's really not worth the money to do this. Either remove the secondaries all together or just leave them as is.

They aren't very restrictive so you'll only be picking up a couple hp and by replacing them with another set of cats it makes your hp gains even smaller and basically negligible.

[marcvtec]

Originally Posted by Dr. G

It's really not worth the money to do this. Either remove the secondaries all together or just leave them as is.

They aren't very restrictive so you'll only be picking up a couple hp and by replacing them with another set of cats it makes your hp gains even smaller and basically negligible.

After driving 100,000 km I can bet they are fairly dirty/clogged.
So changing them to highflow will give good gains