Red Flash

Hi All

So, I am in the middle of my "backend refresh." In the process of doing so, I found out that I certainly have an X-pipe from Lomas with high flow cats that had been installed by the previous owner. I would never have installed anything like this myself, but when I bought the car 4 years ago, it came with it. And after a short time, I realized I actually like it.

But there is a problem, I found that the RMB needs to be replaced (rusting out) and worse, the cats are actually too big to be mounted right after the X-pipe. They don't fit becuase the cats' diameters are too big. But the PO did manage to shoe-horn the whole thing together somehow. So, I would need eccentric cats, and unfortunately, I have found out that these are not available for our cars any more.

So, assuming that I like the sound of my X-pipe and RMB set-up and am not necessarily looking to shark-tune or something, what options are available?

1.) There's a complete set-up from Automobiltechnik Liphardt & Lomnitz GbR which is well-nown in Germany. But at this link, only the cats are mentioned, the system does have TÜV certificate: http://www.automobiltechnik-gbr.de/3.html
2.) And I "heard" that Greg Brown also has a nice exhaust system, but I know nothing about it. The disadvantage with this is that you need to install new exhaust headers as well though, and that's more than I am up for right now.
3.) Anything else?

Thanks for any advice or thoughts... !

John

bureau13

Since the PO already made them fit, is there a reason you can't just leave them as-is, and replace the RMB? Why do you have to replace the cats?

danglerb

More info, smog rules in your area, your own rules on smog, and why can't you find reasonable to use cats? and/or why replace the ones you have?

Maybe a picture of what you have might help?

Red Flash

The point is this: the high flow cats have a diameter that is too large to both fit side by side at the exit of the X-pipe. So, the mounting requires stress on the cats and the X-pipe, and is therefore also difficult to seal. (I found evidence of leaking as well.) If I had eccentric cats, then this would not be a problem.

You are right, I could theoretically just delete the cats, but then I would need something to lower the sound level. An RMB with no cats and no muffler would be wayyy loud I'm thinking.

But are there any other solutions that would have a similar sound as a RMB and high flow cats and actually "fit" without beding and residual stress? Having first hand knowledge of Greg Browns products, I am 100% sure things he sell would fit, for instance.

James Bailey

put on a new stainless RMB and be done with it !! If and when you learn that your hi flow cats no longer are functioning THEN revisit your options.
tuning the exhaust note is often a cut and try type of thing and hard to get it just right It is also so very subjective as to what sounds GOOD ! One man's awesome is another man's rusted out old Chevy truck exhaust sound.....

FredR

I am surprised to hear the cats have a silencing effect but will take your word for that. I understand the Lomas x-pipe has been further optimised recently and if you cannot fit your cats ffind some that do fit.

The 90 GT has the same stock set up as the S4 and if you remove the main silencer to fit the x-pipe then you will need a silencer somewhere else and for this I would try the stock resonator and the stock rear muffler first. If you want to use a RMB then you need to remove the mid resonator and do as I did- make a custom pipe using a Bullet muffler and a top quality good stainless fabricator and welder.

I would also give you a warning- when the exhaust is well sealed I find the exhaust note drones around 4k rpm [presumably the point where the flappy transitions] and I find this somewhat uncomfortable in the cabin.

Fred

James Bailey

Fred he is in the U S .....hard to spend much time at 4,000 RM given the speed limits That is well OVER 100 MPH !!

FredR

James,

I used to have a similar problem - I found it hard to spend time under 4k rpm but then they imported speed cameras and mobile radars. After losing my 90 S4 after some tw*t on a mobile phone clipped me and I hit a parapet at about 70+ mph close to head on I kind of took stock of the situation and nowadays limit my escapades to about the point where it drones [in top gear].

Regards

Fred

Ketchmi

I can easily supply a pair of cats that fit perfectly, all it takes is possibly a little heat and a hammer. The offset cats do not fit anyway, they hit the body on both sides or hang to low depending on how they are installed.

Depending on when I supplied your system depends on which cats you got. Some were worse than others, cat suppliers are a flash in the pan type business. Just as soon as I was comfortable with one's products they would eliminate or change them. Also the new clamps we supply eliminate most if not all leaks. The clamps are only reuseable for a limited time, usually two installations and they require replacement.

There is also the possibility that someone else supplied the cats, the ones I currently supply are custom manufactured for this application. I will not use off the shelf Magnaflow or equivalent as they do not last and break loose internally causing all kinds of fun.

There is no flex in the crossover system so if the cats are touching there is no problem in fact many of my customers have welded them together. The stresses you are concerned about do not in fact cause any problems or I am sure with the hundreds of crossovers I have out there I would have experienced something by now.

Feel free to contact me and we'll see if we can get you taken care of.

Oh, and Fred, the cats certainly do change the sound significantly. Even though the ones I use are 100cpi and about the most free flowing on the planet they do dampen the sound a considerable amount. The 200cpi/400cpi do also to a greater degree but with more restriction to flow.

Jetdriver69

I cut the rotten cat out of my 82. Welded in a straight pipe with O2 bung and installed a stainless Borla cat back exhaust. It sounds much better than stock IMHO.

Nice and throaty and I think I get a bit better throttle response.

No smog for 25 year old cars in Texas.

Crumpler

Did the PO leave the intermediates on?
I have been running on a x-pipe, no cats, stock intermediates, and RMB -- for several years.
While the sound is notable, I don't think it is over the top.
It will bark at times when you get on it-- or throttle down, but mostly you will get that deep throaty, distinctive V8, purr.
Give it a shot and see what you think, IMO.

MjRocket

This is the setup I run as well, Sounds good to me. +1 on giving it a try.

worf928

For reference:
S4 with no cats, stock large resonators and an RMB is loud.
GT with no cats, stock small resonators and a RMB is much, much louder. It is Wiston Cup car loud. The cams make a big difference in what exits the exhaust.

SMTCapeCod

Hey Dave- there's a tidy but costly stainless exhaust on Ebay for some time now, is that your offering?

http://www.ebay.com/itm/PORSCHE-928-...70caac&vxp=mtr

Also,- is the statement above regarding design changes correct, or is it just the cat (converter) rodeo?

And, there's always the Supersprint system...

ROG100

Exhaust note is about as contentious as "what oil do I use".

What is loud to one person is "music to my ears" to another.

My 87 with X pipe, small resonators and an RMB is awesome and not loud at all.
My GTS with X pipe, cats and Dave Lomas full cat back exhaust is bad *** - loud to some maybe but then again I am getting old and deaf - just turn up the radio will ya!!!!

Back to the original topic - did we define what cats are on the car at present? Big difference in size with the original Lomas cats with "pressed" flanges and the later smooth cats. The later cats fit side by side perfectly - I have fitted plenty of them. A picture of the original setup would help.