Shop Life 2.0

[Jdesign]

I wish it was as easy as scrolling through the pictures and seeing the flare form itself into the body. Thats looking great man, keep going!

[HipMF]

Hmm, almost 4 months with no progress? Time to get back to work on this thing now that I'm done fooling around with the compact.

Did a couple piddly things last weekend. Got started on building a new exhaust this weekend.

Since the subframe has moved up 2", there's no need to do the old over-the-subframe, under-the-half-shaft trick anymore. The exhaust that was on the car was put together at the 11th hour, and I never really liked it much anyway. It was fine for the grandpa-stanced, 13" wheeled version of the car, but it's time for something new...

Maybe my google-fu is weak, but I haven't been able to find a video of a 4-cylinder car that has a "true dual" exhaust (ie the exhaust from half the engine's cylinders travels to the rear of the car in one pipe, while the other half travels in another pipe). Both V8s and inline-6s both seem to sound better with this type of setup, but I don't seem to recall ever seeing it applied to an inline 4.

So, in the interests of science, I've decided to try it for myself. Obviously, 4-cylinders tend to sound like crap in general, so I'm not expecting miracles here, but here's what I'm thinking: 4-bangers tend to have a fairly mellow tone in general, but when they do get raspy it tends to be extreme, and in a narrow rpm range (unless, of course, they're forced through some terrible fart-can exhaust which just sounds raspy and terrible all the time...). By splitting the exhaust in two, I'm hoping that each half will hit it's raspyness at a different rpm, thereby cutting the intensity in half, but prolonging it over a larger part of the rpm range. I'm also assuming that lengths of straight-pipe tend to resonate at a particular RPM, contributing to raspyness, so I'm trying to make sure every straight section of pipe is a unique length. The idea here isn't to get rid of the raspyness, but to spread it evenly across as wide an RPM range as possible.

So, here's what I have so far:

The M42 is a good candidate for this experiment, because the stock exhaust is a 4-into-2-into-1 system. The stock header already has each pair of cylinders each exiting through 2 separate pipes, so that's where my work starts.

Even "true dual" systems seem to sound better with an "H" or "X" pipe, so I've included one at the location where the stock exhaust would merge from two into one. This will also be a handy spot to put the O2 sensor so that it gets an average reading from all 4 cylinders and doesn't obstruct flow through the pipe. I'm using 2x1.875" pipe, which is way too large for a stock M42, but gives me some future proofing for when I finally put a turbo on this thing, or rip it out and do something completely different...

The glasspacks that I'm using are super cheap and don't seem like they'll be very effective, so if it does end up sounding like crap, I'll replace those with something that has a greater muffling potential. I've also got a couple stainless MagnaFlow mufflers for the rear of the car that should help quiet things down and look cool to boot.

[YoungCR]

In for the exhaust video! Looks great so far

[Jdesign]

That's looking nice! I am interested to hear what it sounds like. I have a good history with working on Honda 4 cylinders and always thought cheap exhaust made them sound horrific. Because there is such a huge aftermarket for them, everyone buys these cheap exhausts, and now the whole world associates the terrible 4 cylinder sounds with Hondas.

 A nice muffler and correct resonator and piping makes a world of a difference. You look to be on the right track to making something that sounds good. Im all ears

[B C]

I like it when people disregard common solutions and dive into the deep dark world of trying new things. So long as you dont end up with a manifold that looks like a dang house.

[GunMetalGrey]

Your fabrication skills never cease to impress! 
I like your thought process behind the exhaust, and I'm excited to hear it!

[m42b32]

I've always wanted to try this, looks awesome so far! I saw someone post about doing something similar on an e36 318is on BF.c a while back using a stock 328i exhaust and a Y-pipe after the o2 sensor. I managed to dig up the link, but unfortunately the video isn't available anymore. It sounded way better than stock with minimal rasp. Here's the thread, not much info now that the video is gone:

https://www.bimmerforums.com/forum/showthread.php?1872648-328i-Exhaust-on-a-318is-(-video-with-sound)&highlight=318is+dual+exhaust

[HipMF]

Made some more progress. Not as confident about the rear section from a sound perspective. I think the long-ish straight sections aren't a good thing, but i chose the most direct route, rather than adding unnecessary bends.

Still have some tweaking, then hangers and weld the mufflers on. Fits nice and tight to the car, so I'll have to put some thought into the hangers to keep it from rattling. I think it will be fine though.

[Jdesign]

Doesn't it normally exit out the left side of the car?

[B C]

looks real good! which muffler are you using?

[m42b32]

I'm excited to hear how it sounds!

[Bassboy3313]

Jdesign said:

Doesn't it normally exit out the left side of the car?

It does since the fuel pump, filter, etc. are on the right side normally. Since he is running a fuel cell, it opens that area up for interpretation. 

[HipMF]

Jdesign said:

Doesn't it normally exit out the left side of the car?

I do what I want!

But yes, I moved the fuel pump to the drivers side since the fuel lines run down that side of the car. So I moved the exhaust to the other side.

The eE21s that I've seen corner-weighed are also a tad light on the rear right corner.

[Jdesign]

HipMF said:

I do what I want!

But yes, I moved the fuel pump to the drivers side since the fuel lines run down that side of the car. So I moved the exhaust to the other side.

The eE21s that I've seen corner-weighed are also a tad light on the rear right corner.

There is a meaning to your madness. I like it!

[straight6pwr]

cheap glasspacks do indeed work well. they definitely helped with the rasp on my car.

.

[Jdesign]

Im always hesitant with cheap glass-packs because they can fail. If they are welded in that means redoing exhaust, and Im not a fan of working on exhaust..

[GunMetalGrey]

Just wanted to drop by and say hello.

[HipMF]

#ShopLife

I guess I'm finally old enough to have some proper dad shades. I think I've had those since maybe 2003...?

[jc43089]

I bought some glass packs from http://www.heartthrobexhaust.com/glasspacksandflowpacks.htm The shell is much thicker than el cheapo ones, but they were very resonably priced, just call to order.  I think I paid under 60$ shipped for a pair of small ones.  I would never buy Cherry bomb or Thrush after using these.  Made in  Litchfield Minnesota too.

[HipMF]

Got the car back together enough (barely) to take a couple beat-runs down the road in front of the shop. Can confirm that the exhaust is not just loud, but also obnoxious. Still no floor in the trunk, and no back seat, so the exhaust might as well be plumbed right into the cabin. It's the kind of loud that you can feel, as opposed to just hearing it. Also still missing one of the side windows. That combined with the not-car-culture-friendly temperatures this weekend, stiffer suspension, manual steering and general fear of things falling apart or exploding made for quiet a visceral first-drive experience. I survived, nothing broke, but there are more things left to do than I have fingers to count them.

I thought I did a pretty good job bleeding the brakes, but they didn't work worth crap (try rev-matching your downshifts when the brake pedal goes straight to the floor. It doesn't work well, but it's worth a laugh...). Bled the front, which made little, if any, difference. Will have to try re-bleeding the rears next weekend. May have a leak somewhere? Who knows...

Body roll is still substantial, even though my spring rates are 2-3 times stiffer than stock.

Also can confirm that Hankook RS-4s are no match for the mighty torque of a tired M42 when the temps outside are near freezing...

All-in-all it was a good time. Much work left to do, but definitely excited to get this thing out to an autocross or ten this summer.