[afo818]

If you have a full exhaust with catless downpipes I’m sure you’re also suffering from chronic respiratory illness lol

Anyone running catless primary with stock secondary’s? Or something similar to the photo attached? Interested in hearing some feedback!

[Stlthnmrdrd]

Pretty sure that will help a lot with smell, rasp maybe slightly. I believe the secondaries are 200 cell cats.

.

This is a f90 with 200cell hjs with akra full exhaust stand still revs

same car, but in motion @14:25

[afo818]

Originally Posted by Stlthnmrdrd

Pretty sure that will help a lot with smell, rasp maybe slightly. I believe the secondaries are 200 cell cats.

https://www.youtube.com/watch?v=nhpF...BCsseldorfe.K.

This is a f90 with 200cell hjs with akra full exhaust stand still revs

https://youtu.be/OVPFXv8MOnI?si=7dy5JTrcTvLkhcTI&t=867

same car, but in motion @14:25

This is the car that started my journey
The downpipes on this car is basically catless primary and catted secondary, not sure if that makes a difference vs the other way around

[AustinM4AlpineM5]

Originally Posted by afo818

If you have a full exhaust with catless downpipes I’m sure you’re also suffering from chronic respiratory illness lol

Anyone running catless primary with stock secondary’s? Or something similar to the photo attached? Interested in hearing some feedback!

I have the Stone exhaust downpipes with the secondary cats on my car currently. They are insanely high quality and sound better than full catless in my opinion.

Previously I’ve had secondary deletes, and then fullcatless(Evolution Racewerkz) and just didn’t like the exhaust sound.

When I have sometime I’ll start a thread with some pics and quality videos of these downpipes paired with the Dinan x-pipes. This setup sounds really good to me and other M5 owners locally agree. It has turbo spool sounds, louder pops and bangs, but has a better V8 sound signature.

I’ll add some pics shortly.

[afo818]

Originally Posted by AustinM4AlpineM5

I have the Stone exhaust downpipes with the secondary cats on my car currently. They are insanely high quality and sound better than full catless in my opinion.

Previously I’ve had secondary deletes, and then fullcatless(Evolution Racewerkz) and just didn’t like the exhaust sound.

When I have sometime I’ll start a thread with some pics and quality videos of these downpipes paired with the Dinan x-pipes. This setup sounds really good to me and other M5 owners locally agree. It has turbo spool sounds, louder pops and bangs, but has a better V8 sound signature.

I’ll add some pics shortly.

I think that’s the remedy right there. Better flowing turbos and the rasp restriction in the secondary downpipes.
Please post whenever you get a chance thank you!

[AustinM4AlpineM5]

[pbonsalb]

So high flow cat secondaries with catless primaries give less rasp than high flow cat primaries with catless secondaries? Interesting. Until yesterday, I had not seen the high flow cat secondary option. One post above said the Stone high flow cats are very high quality. Are they expensive HJS or Gesi? If not, they are probably the same quality as the CTS or MAD or other inexpensive high flow cats.

[afo818]

Originally Posted by pbonsalb

So high flow cat secondaries with catless primaries give less rasp than high flow cat primaries with catless secondaries? Interesting. Until yesterday, I had not seen the high flow cat secondary option. One post above said the Stone high flow cats are very high quality. Are they expensive HJS or Gesi? If not, they are probably the same quality as the CTS or MAD or other inexpensive high flow cats.

Either way you go you won’t have rasp but it seems like the best sound and turbo spool is with secondary catted catless primary
However it may be the same as leaving the stock secondary’s on in my opinion instead of spending 5k on that option

[AustinM4AlpineM5]

Originally Posted by pbonsalb

So high flow cat secondaries with catless primaries give less rasp than high flow cat primaries with catless secondaries? Interesting. Until yesterday, I had not seen the high flow cat secondary option. One post above said the Stone high flow cats are very high quality. Are they expensive HJS or Gesi? If not, they are probably the same quality as the CTS or MAD or other inexpensive high flow cats.

I’ll do my best to get accurate sound in a video while moving and parked. Also, when possible I’ll try to get a few other F90s together and compare them.

That’s really the only reason I went with these, I had never come across a catless primary with secondary high flow cats. I would really like to have someone flow test these to see what the flow rate is, but not sure who could do it. The low end back pressure is great and hi RPM flow seems good, but maybe not catless good..

Pretty sure Stone manufacture the cats in-house for the eddy design. Based on the materials and build quality my guess is they’re better quality cats, but I honestly don’t know. I have a direct line at Stone so I’ll ask.

[afo818]

Originally Posted by AustinM4AlpineM5

I’ll do my best to get accurate sound in a video while moving and parked. Also, when possible I’ll try to get a few other F90s together and compare them.

That’s really the only reason I went with these, I had never come across a catless primary with secondary high flow cats. I would really like to have someone flow test these to see what the flow rate is, but not sure who could do it. The low end back pressure is great and hi RPM flow seems good, but maybe not catless good..

Pretty sure Stone manufacture the cats in-house for the eddy design. Based on the materials and build quality my guess is they’re better quality cats, but I honestly don’t know. I have a direct line at Stone so I’ll ask.

Any idea how to upload videos on here? I have a recording with a professional mic
Catless Dinan X pipe Akra muffler

[Stlthnmrdrd]

Originally Posted by afo818

This is the car that started my journey
The downpipes on this car is basically catless primary and catted secondary, not sure if that makes a difference vs the other way around

On the car in the video, the primary cat location is moved down to where the secondary downpipe is the o2 bungs are relocated as well. It is done to bring the exhaust heat as far back as possible.

[Stlthnmrdrd]

Originally Posted by pbonsalb

So high flow cat secondaries with catless primaries give less rasp than high flow cat primaries with catless secondaries? Interesting. Until yesterday, I had not seen the high flow cat secondary option. One post above said the Stone high flow cats are very high quality. Are they expensive HJS or Gesi? If not, they are probably the same quality as the CTS or MAD or other inexpensive high flow cats.

They are hjs

[pbonsalb]

HJS id the best. So not cheap. $4k?

[916_M5]

Originally Posted by AustinM4AlpineM5

I have the Stone exhaust downpipes with the secondary cats on my car currently. They are insanely high quality and sound better than full catless in my opinion.

Previously I’ve had secondary deletes, and then fullcatless(Evolution Racewerkz) and just didn’t like the exhaust sound.

When I have sometime I’ll start a thread with some pics and quality videos of these downpipes paired with the Dinan x-pipes. This setup sounds really good to me and other M5 owners locally agree. It has turbo spool sounds, louder pops and bangs, but has a better V8 sound signature.

I’ll add some pics shortly.

Please share!!! Subbed!

[Stlthnmrdrd]

Originally Posted by pbonsalb

HJS id the best. So not cheap. $4k?

My mistake guys, problem with stone exhaust version is they dont mention its hjs + the O2 bungs arent even relocated to the lower downpipe section. Reason people do hjs not just for quality but also for street emission regulations. Since they dont mention anything like hjs or gesi, its most likely similar cats found in ER, mad, and cts.

For 4k imo its not even worth it. Either slap the oem secondaries or just buy catted primary 200cell hjs cats from Keller performance for half the price + the benefit of passing emissions without swapping out to oem primaries.

If the o2 bungs were relocated to the lower downpipe and if the cats were actual hjs, I would say go for it. If I was paying 4K for a downpipe set up, I wouldnt want to deal with swapping out to oem primaries just to pass emissions.

Reselling to used market is gonna be a headache bc no one is gonna pay 3k-4k for downpipes when there so many cheaper options brand new.

[pbonsalb]

I don’t know the price— hence the question mark. For me, extending O2 wiring and welding in bungs is no big deal but I would instead just deal with the emissions issue with a tune.

[afo818]

Originally Posted by Stlthnmrdrd

My mistake guys, problem with stone exhaust version is they dont mention its hjs + the O2 bungs arent even relocated to the lower downpipe section. Reason people do hjs not just for quality but also for street emission regulations. Since they dont mention anything like hjs or gesi, its most likely similar cats found in ER, mad, and cts.

For 4k imo its not even worth it. Either slap the oem secondaries or just buy catted primary 200cell hjs cats from Keller performance for half the price + the benefit of passing emissions without swapping out to oem primaries.

If the o2 bungs were relocated to the lower downpipe and if the cats were actual hjs, I would say go for it. If I was paying 4K for a downpipe set up, I wouldnt want to deal with swapping out to oem primaries just to pass emissions.

Reselling to used market is gonna be a headache bc no one is gonna pay 3k-4k for downpipes when there so many cheaper options brand new.

Very well said

[Stlthnmrdrd]

Originally Posted by pbonsalb

I don’t know the price— hence the question mark. For me, extending O2 wiring and welding in bungs is no big deal but I would instead just deal with the emissions issue with a tune.

If u can get a hold of a hjs 100/200 cell unit u could technically make the secondary section similar to the one in the video.

OR

Maybe email Keller performance maybe they can make a custom pair of high flow catted secondary hjs section with the bungs.

Keller performance might take on the project if you guys setup a group buy of high flow secondaries.
This could perform better than their catted primary 200 cell, bc the cats are far from the turbos, which will keep the turbo temps lower compared to the cats being close to the turbos and trapping the heat. Plus it will mask the fumes

Rally inspired setup, also similar to m235ir

[pbonsalb]

I don’t need to do this on this car, but I can and have extended O2 wiring and welded in O2 bungs.

[AustinM4AlpineM5]

Originally Posted by Stlthnmrdrd

My mistake guys, problem with stone exhaust version is they dont mention its hjs + the O2 bungs arent even relocated to the lower downpipe section. Reason people do hjs not just for quality but also for street emission regulations. Since they dont mention anything like hjs or gesi, its most likely similar cats found in ER, mad, and cts.

For 4k imo its not even worth it. Either slap the oem secondaries or just buy catted primary 200cell hjs cats from Keller performance for half the price + the benefit of passing emissions without swapping out to oem primaries.

If the o2 bungs were relocated to the lower downpipe and if the cats were actual hjs, I would say go for it. If I was paying 4K for a downpipe set up, I wouldnt want to deal with swapping out to oem primaries just to pass emissions.

Reselling to used market is gonna be a headache bc no one is gonna pay 3k-4k for downpipes when there so many cheaper options brand new.

100% agree and well put.

My main goal is to get a better exhaust note out of the F90. Emissions are not an issue for me, but I would absolutely be pissed off if I paid $4k and they didn’t pass inspection.

The best setup from my experience so far would probably be something like this:

A 3.5” catless primary with a smooth transition to a 3” high flow catted secondary and o2 bungs both pre and post cat.

Or alternatively:

A Keller catless primary and use the factory secondary *if they fit together*

I have talked to Stone about the custom setup described above, but don’t think they’re interested. If Keller would do it that would be awesome and I’d be game.

Not advocating that anyone spend $4k on this setup at all. My take away is that it sounds different and in a good way to me and some local M5 and M8 owners.

My next step is buying the Valvetronic full Ti cat back. I’m hoping that has the sound that I’m going for. My 0.02 and let me know what you guys think.

[afo818]

Originally Posted by AustinM4AlpineM5

100% agree and well put.

My main goal is to get a better exhaust note out of the F90. Emissions are not an issue for me, but I would absolutely be pissed off if I paid $4k and they didn’t pass inspection.

The best setup from my experience so far would probably be something like this:

A 3.5” catless primary with a smooth transition to a 3” high flow catted secondary and o2 bungs both pre and post cat.

Or alternatively:

A Keller catless primary and use the factory secondary *if they fit together*

I have talked to Stone about the custom setup described above, but don’t think they’re interested. If Keller would do it that would be awesome and I’d be game.

Not advocating that anyone spend $4k on this setup at all. My take away is that it sounds different and in a good way to me and some local M5 and M8 owners.

My next step is buying the Valvetronic full Ti cat back. I’m hoping that has the sound that I’m going for. My 0.02 and let me know what you guys think.

That’s a great way to put it. I emailed Keller to see if they can make a 200 cell hjs secondary set of downpipes. If not I may try stock secondary w my ER catless primaries and see what kind of sauce we get

[TacoJova]

As someone who is about to go catless cause of built motor with turbos does anyone make a resonated set of downpipes? On my f80 with turbos I had Resonated AR Designs with resonators in the midpipe with a Remus rear to eliminate the rasp that catless gives. Add to the fact that on that particular car turbos made it soo much louder. I wonder if adding resonators to the primaries would be effective for rasp