EXHAUST QUESTIONS???

NAVYBO · 29th February 2004, 18:24

For everyone that's taken off their stock exhaust, I have a few questions.

First, the stock system appears to have an H-pipe connection where the brackets are right after the cats. Is this a true H-pipe, or is this just a bracket welded in for support? If someone still has their stock system laying around, can you check that out via the hanger method.

Second, do the resonators have baffles all through them and is there a crossover effect? Since both pipes feed into the resonators, it would appear that they are a giant X-pipe. However, if there are baffles in there, then I would think this would be negated. I'm just curious. Once again, for those with the system removed, if you could take a look, I'd appreciate it.

Since reviewing most posts on exhaust, there is no major HP gains with the SS X-pipe, and if the stock system has a functional H-pipe in there, which I believe it does, then simply cutting out the resonators and replacing them with stainless pipe would give the desired effect of improved sound and flow with the weight savings.

Thanks for the helps.

Brett

2003 Titanium Silver M5
Custom CAI
UUC EVO 3 SSK and trans mounts enroute

NAVYBO · 29th February 2004, 18:32

Here's a picture of what I'm talking about with the stock looking H-pipe. You can see it by the two hangers there on the left.

Brett

Need4Spd · 29th February 2004, 20:14

I don't quite understand but let's see if I do. What you propose is simply taking out the resonators and replacing with straight (well, curved to fit) pipe so as to eliminate the baffling in the resonators but achieve no other connection between the two pipes, right? I assume the reason to do this is cost, so you don't have to buy an X pipe, or is there another reason? It's interesting that you mentioned the H pipe. On V8 cars and the M5 is no exception, you get better torque and a smoother exhaust note if you connect the twin pipes somewhere between the exhaust manifolds and the mufflers. Connecting the two smooths out the pulses and lets each side "see" more area effectively making each side seem "larger" to each particular pulse, giving better breathing. I've often myself wondered whether the stock system has an H connection and whether that's also there when converting to an aftermarket exhaust or SS X pipe.

The Tubi seems to have the H connection.

TCM · 29th February 2004, 20:23

The stock H pipe connection is not very good. The SuperSprint X pipe or similiar offerings from other brands greatly improve the flow of the exhaust IMHO. Definately provides crisper throttle repsonse and more power gains than an exhaust does. For $400, I would not hesitate just to get an X pipe.

M5 Fever · 29th February 2004, 20:46

Navybo

The H -pipe is truly an H -pipe, but I cannot speak to its functionality of exhaust flow. It is at 90 degrees compared to an x -pipe which must be freer flowing. I verified by sliding a wire thru from one side to the other.

The stock resonators do not appear to have baffles. I dropped a plumb bob from the top and it slid thru down to the mufflers w/o any interference.

Aside from the 90 degree h-pipe design, I have taken some pics pointing out where exhaust flow may be compromised. The key word here is may.

At the brackets, the pipes are flattened out.

Below the brackets, the pipes are flattened out again

Where the exhaust splits to go into the stock cans, the larger pipe is split into two smaller ones.

hope this helps

btw, where in MD are u. when I cruise to baltimore, annapolis or st michaels this summer, maybe we can crack some crabs if you're nearby.

al

NAVYBO · 29th February 2004, 23:03

Need: Yes, you are correct in what I was looking for. It is most definitely a good thing to have an H or X-pipe connection in our exhaust system. Since Al has verified that our stock system does in fact have an H-pipe connection, it is no wonder that no one has been able to get any measurable performance gains with their exhaust systems. To me, I would say that the TUBI has an X-pipe, however its design seems much different than the Supersprint.

TCM: I hear what you are saying, and I probably will just go with the Supersprint since it is a proven commodity.

Al: My thinking on this subject was that if the stock system has a functional H-pipe connection and the resonators aren't baffled, than its going to be extremely hard to gain any performance. Looking at your pictures, there are definitely some kinks in the stock piping, but nothing too major.

I've been looking at two things. First, Magnaflow has a stainless X-pipe, however it is not a complete system like the Supersprint. I can definitely make it work in the system for less $$$$ than the Supersprint. It helps when your brother can weld stainless. The second option would be to just simply enlarge the stock H-pipe connection and cut out the resonators. This larger connection should definitely improve flow and sound and is probably the cheapest option.

From doing searches, it looked as though only one person has done the straight pipes back from the cats to the mufflers, however I am wondering if they did it after the stock H-pipe or not. I know they said no performance loss. I'm also wondering if anyone else has done some creative exhaust system modifications.

Any insight would be appreciated.

Brett

NAVYBO · 29th February 2004, 23:05

Al,

I live in Annapolis, but am going to Newport, RI for a Navy school in May. From there, its up to the Navy. Who knows where I'll end up.

Brett

M5 Fever · 1st March 2004, 02:18

I spent this past xmas in annapolis. My next door neighbor (USNA-71) goes there often and we seem to always tag along. May will probably be too early for crabs

Good luck with your exhaust system whatever you decide on. I installed mine for sound over performance. If I gained a few hp, I consider it a bonus. At least now, it sounds like I'm going faster, hehehe

And good luck in Newport. I was there last summer for the first time, such a cool place.

al

Need4Spd · 1st March 2004, 08:05

Quote:

The H -pipe is truly an H -pipe, but I cannot speak to its functionality of exhaust flow. It is at 90 degrees compared to an x -pipe which must be freer flowing.

Oddly enough, from what I recall reading, the benefit of the H pipe is simply the connection to the other pipe. It doesn't have to be all that large and 90 degrees is fine. As someone else mentioned, that's likely the reason no one can find much additional HP or torque from going to an X pipe.

NAVYBO · 1st March 2004, 13:58

I think at the higher RPM's, the X-pipe is probably more effecient and gets better flow than an H-pipe due to the fact the H-pipe is a 90 degree angle. However, this effect is probably very minimal on our cars and why no one gets much out of the X-pipe. If I was a racer, the couple of HP that might be had would be worth it I guess. I'm not a racer, I just want the car to sound like a real V8. So after some serious thought, I will be going with cutting out the resonators and replacing them with 2.5" stainless piping unless I can convince my brother to create a giant crossover where the stock exhaust is crimped up right after the stock H-pipe. That would take some serious fabrication though, and I don't know if there is any performance to gain by doing that. Any body have any thoughts on that one?

The beauty of doing all of this is that it is pretty cheap to mess. Only $50 for stainless tubing. This time I'll remember my camera and take some pics. Install is scheduled for Sunday along with my UUC SSK and tranny mounts.

Brett