Pardon me while I go back to revisit a few things I didn't write down at the time. Still, when you get a car running it's such an awesome feeling that you kinda want to skip to the end and let folks know it happened...
That said, half of the reason I wrote / am writing this thread is to document things for myself so I can remember the lessons learned for the next job. This one's fairly straight forward, just an
exhaust build... but it took forever to get it done how I wanted.
So I'd built a bitching set of headers a while back right? I’m picking up where that left off.
Ran stainless screws on the merges per Jack Burn’s suggestion:
Left myself just enough space for the 02 bungs. (No pic of the bung but exhaust bungs aren’t that exciting anyways).
Here’s one key lesson learned: The type of V-bands I was using (Deed’s Engineering) have keys to maintain precise alignment. I think the OBX bands and a few others do this too. Cool right?
Turns out welding will deform keyed v-bands just enough that they won’t key together anymore… Note to self, if there’s any way to do so, ALWAYS weld up the V-bands with a mating part clamped to it to help keep it from moving on ya. I have probably 2-3 hours with a dremel grinding and fitting and grinding and fitting to get these to key back together like they’re supposed to.
So header’s were finally done done done and installed. Now I’m building the rest. I’m a big fan of 1:1 printed paper doll studies to work out geometry. Here’s my x-pipe study.
I debated a little bit over how much overlap to run on the crossover. Ended up calling Jeff Jordan and rapping theory with him for while. Good stuff... At the end of the day, I decided to aim each upstream pipe almost at the from the fork downstream so 2/3 of the flow would continue down the pipe it came from and 1/3 could cross over. It seems like companies making good power (American Racing, LG, Kooks, etc) tend to not do a full cross and I could see why I might not want to have a significant reduction in area.
So now to make it a reality. Started by coming off the headers at angles kinda where it wanted to be to split the difference between trans tunnel and transmission.
I’m still quite stoked on the Ronin trans mount. This is a dual 3” exhaust and it packages nicer than my old Grannies setup did with 2.5 duals.
Key thing I did for getting the alignment right for the X-pipe was setting up a guide string. No idea if this is common in industry but it made sense to me as a reference of where I wanted to land and what was going to be required to take two random angles off the headers (at unequal distances from my x-pipe) and get them to land straight and true.
I built passenger first but you can see how I need two angles on the driver’s side to keep everything tangent.
X-pipe was 15” downstream of the collectors. I’m a big fan of David Vizard’s book “How to Build Horsepower” and recommends 10-20” as a ballpark collector length, albeit he typically does the whole pressure wave termination box thing, which I decided not to.
Jack Burns (of Burns Stainless) just says to run them as close to the merges as you can get. This seemed to land pretty well regardless of whose advice I was following.
Before I fully committed and welded the X-pipe I started the muffler end to have a better idea what I was aiming for. I only own 8 jack stands and the car was on 4 of them so I had to get a little creative to get everything shimmed in place. No, I didn’t tell my wife I borrowed the camera tri pod.
Mufflers are Vibrant TPV 1090’s.
http://vibrantperformance.com/catalog/product_info.php?cPath=1022_1031_1052&products_id=1165 One of the key lessons I picked up from the Vizard book I mentioned was in regards to sizing exhaust via flow rather than pipe size. Key rules of thumb:
1) You need 2.2 cfm of flow per engine horsepower if you want to be near “loss less”.
2) A straight pipe flows 115 cfm (at exhaust pressures) per inch of cross sectional area.
3) A straight through perf core muffler flows about 55-60% of a smooth straight pipe at equivalent pressure.
Note that last rule isn’t Vizard’s but that what I found in studying and crunching numbers on what muffler flow data I was able to find online. He does discuss running bigger muffler cores than the rest of the piping which is really the key point.
Brass tacks. These are 4” core mufflers. You can reach your whole arm in the tip, which isn’t really a tip since there’s no change in diameter to the inside. These sound ---ummmm--- healthy?
By the way, if you have the means… Backpurge all your stuff! I don’t have said means, but I’m a still a dork, so I went back in and ground off all the “sugaring” on the inside wherever I could.
Here’s the mid section, starting to look like something. That last weld (see sharpie mark on the right) was hard because you can’t get a torch all the way in there. About 1" of tungsten stickout later and you can officially color me impressed at what a gas lens can do to help a torch.
These are the weld that matter, when you tie the front to the back you’ve committed to where the muffler’s land so this was one I spend a great deal of time on and was somewhat challenging to get right. FWIW I wouldn’t even attempt to do this job without a big disc sander. You’ll be using that a lot to trim angles a 1/32" here and there.
And here we are back under the car. Ronin 8.8 peeking out, makes me happy.
Mid section is nice and straight and centered.
Left about 1/4" clearance to the subframe since my car is relatively low. Nice shot of the Ronin 8.8’s front mount as well.
Smooth tapers for the upsized mufflers. Wanted to keep flow as smooth as I could.
Last but not least I thought I show of some comparison of my slowly improving TIG skills. I still suck at feeding so I start and stop more than I should but at I’m learning to compensate. Here’s a couple welds at the beginning of the project.
Compared to that about halfway through the job.
Did just about everything on the bench with a small vice as a support V to keep things from rolling.
All hangers were built after the fact using 3/8” pencil rod. If you heat up the rod (propane torch, map gas if you have it) you can bend it reasonably nicely with a hammer and vise. I used a hodge podge of worm screw hose clamps to hold them to the body of the muffler to tack them in place under the car. All welds critical to fit were tacked like that, less critical ones I just marked orientation and tacked on the bench prior to fit check.
Not doing this with a lift I think had me climbing back and forth under my car ~200 times, by the time it was all done. Still, it lands perfect and I learned a ton. Feels good to do things yourself.
