Need advice for 540 quad exhaust!

[Armando540i]

The tips are vibrant 3.5", measuring the cut out on the m-tech diffuser it seems as though i'm going to need to trim half an inch to get them to fit. Also, does anyone have any experience or a guide on how you did the cut out on the passenger side? Tools/measurements etc? This will be the 3rd time messing with my exhaust.. From changing the muffler... To taking out the y-res.. Now putting it back in to run quad exhaust straight pipe from the res (or muffler delete lol). I will keep this thread updated on the route I take in dealing with the spare tire well and how the whole thing goes.

[Only1Balto]

I'd take some cardboard or paper and trace the current cut out, take a few measurements of the exact location on where it is relative to the bumper, then just flip the paper over and place it on the other side exactly, trace and cut. After the line has been drawn, cut out the bulk of it any way you can- then slowly dremel up to the line for clean looking cut. That's just what I would do if I had to cut, however there are diffusers out there already with the supplied two holes. But as you've mentioned, you're going to need to cut the original side anyways.

[auaq]

I'm not sure if this is possible as I think you will have to reposition/relocate the battery to a different place and cut and remove the spare wheel area. On the M5 the battery is located where the spare tire would be and they don't have a spare wheel. I think that's how BMW managed to have the dual exhausts. Unless if you're going like straight pipes or something different where you can circumvent around the battery and the wheel location then it's possible I guess.

- - - Updated - - -

I know that's how Brandon managed to have or install dual exhausts on his touring.

[Only1Balto]

I'm not sure if this is possible as I think you will have to reposition/relocate the battery to a different place and cut and remove the spare wheel area. On the M5 the battery is located where the spare tire would be and they don't have a spare wheel. I think that's how BMW managed to have the dual exhausts. Unless if you're going like straight pipes or something different where you can circumvent around the battery and the wheel location then it's possible I guess.

- - - Updated - - -

I know that's how Brandon managed to have or install dual exhausts on his touring.

He'll definitely have to do that. He mentioned he'd keep us updated on which direction he plans on taking when it comes to the spare wheel well. I'm curious as well, seeing as how this is something I too would like to get done in the future.

[dannyzabolotny]

I've seen some people route the second exhaust pipe while keeping the spare tire well, by only cutting into the spare tire well slightly. I could never give up having a spare tire just for quad pipes.

[mcgnms]

I have a full dual exhaust system. I have mufflers in the back as normal. The battery is in the same position. The spare tire well had to be cut into and the spare tire just sits in the trunk now.

[Only1Balto]

The E39's have a big boot. A tire fits in there nicely with room to spare. I see a lot of M5 guys doing this, strapping the tire down with the net. I wouldn't hesitate to do it either. Where did you get your tire well cut MCGNMS? I'm curious where people go and who they ask. I guess I'm lucky, here in SD there are a ton of custom shops that do their own fab work.

[mcgnms]

I did all the cutting myself and use small spot welds before sealing everything up properly. Here are a few photos:

[Armando540i]

I'd take some cardboard or paper and trace the current cut out, take a few measurements of the exact location on where it is relative to the bumper, then just flip the paper over and place it on the other side exactly, trace and cut. After the line has been drawn, cut out the bulk of it any way you can- then slowly dremel up to the line for clean looking cut. That's just what I would do if I had to cut, however there are diffusers out there already with the supplied two holes. But as you've mentioned, you're going to need to cut the original side anyways.

appreciate the advice! And yea if I wasn't cutting the original side more I would go for an m5 diffuser with the dual outlets. Going to be doing the outlining for the cut tomorrow.

[Armando540i]

I'm not sure if this is possible as I think you will have to reposition/relocate the battery to a different place and cut and remove the spare wheel area. On the M5 the battery is located where the spare tire would be and they don't have a spare wheel. I think that's how BMW managed to have the dual exhausts. Unless if you're going like straight pipes or something different where you can circumvent around the battery and the wheel location then it's possible I guess. - - - Updated - - - I know that's how Brandon managed to have or install dual exhausts on his touring.

I am going to be going with straight pipes cat back. Whichever route I take the spare wheel has to stay. My body shop/mechanic said he will be able to make a small cut for a channel near the diffuser to make room and have to seal and weld it all shut from inside the trunk. Wanted to bash in the area but I don't want to stress the frame as I would need it up at least 4inches so the pipe sits right.

[Armando540i]

I've seen some people route the second exhaust pipe while keeping the spare tire well, by only cutting into the spare tire well slightly. I could never give up having a spare tire just for quad pipes.

Yes going to go a similar route, me neither I wouldn't be able to give it up lol. Because i'm just going to run a straight pipe to tips I won't be needing to cut much to fit it under there.

[Armando540i]

I did all the cutting myself and use small spot welds before sealing everything up properly. Here are a few photos:

nice job and set up! Will keep this updated with the progress, looking into a supersprint x pipe to replace section 2 of the exhaust.

[AK_5eries]

mcgmns, you used magnaflow round mufflers as resonators in place of the y res? What are the dimensions on those? Any drone?

[mcgnms]

I actually used a complete system called a 16858. It comes with a X-Pipe that has built in resonators. There is no drone, but it does have a very deep/bassy sound to it from outside. It sounds very different from other exhausts I have heard. It is also fairly quiet compared to other exhausts.

Here is a link to it with specs.

[Charlie207]

Legitimate question here.... What is the benefit of a dual-exhaust setup after an X-pipe? Wouldn't a larger, single-pipe exhaust be more efficient, with much less weight? Same volume of exhaust gas, but lest surface area of pipe?

I'm used to turbo cars, where you just need to dump all the gas after the turbo, so dual exhaust was never practical.

Either way, the DIY work looks pretty great. Good on you for taking up that project. I bet it sounds great.