Exhaust fitting?

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socal1200r
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Exhaust fitting?

Post by socal1200r » Tue Sep 17, 2013 7:35 pm

So I got the new stainless header yesterday, along with the downpipe. Took the downpipe to a muffler shop, said it'll be tight, but it should fit, their estimate for labor was $100. Had a chance to look at the underneath of the car, and wow, what a maze of exhaust tubing, far from being a straight shot to the back. I think it would be a very good candidate for a new universal cat (2.5"), new welded muffler (2.5"), and dual outlets (2.5"), pretty much straight back from the downpipe (with a slight bend to get it down the middle), more on that later.

I'm looking at the stock exhaust manifold, and notice this fitting on the rear of the manifold:
Image

I look at the new header, and there's no fitting on it for anything, just tubes:
Image

So what does this fitting do on the rear of the stock exhaust manifold? Is it something I need to find a way to hook up with the new exhaust, or do I just trace where it goes and block it off, find another source, or?
Robert Brooks
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merk23literturbo
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Re: Exhaust fitting?

Post by merk23literturbo » Tue Sep 17, 2013 7:55 pm

I would do 3 inch all the way back down the right side under the car, extremely easy and not too expensive. All you need is a 6 ft straight piece and two long 45 degree bends with 3 inch cat and muffler. I did mine with good quality stainless 5-6 years ago and it looks like the day I put it on. Well worth the money.
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Re: Exhaust fitting?

Post by John Brennan » Tue Sep 17, 2013 8:50 pm

That's the Exhaust Gas Recirculation, or EGR, fitting/pipe. It runs to a solenoid-controlled valve affixed to the upper intake near the throttle body. Under certain conditions, the ECU opens the valve, allowing exhaust air to be recirculated back into the intake, where "witchcraft happens" and emissions are reduced, or so it is claimed.

A great many, if not most, folks here will eliminate this apparatus if/when given the chance (such as buying a header with no EGR fitting, and, looking at their engines, going "hmmm..."). Headers, rotated intakes, or sometimes, no specific reason at all ("What are 'ya rebelling against, Johnny?" "Waddaya' got?" "EGR valves." "Sounds good-- I'm in.") will suffice. In truth, they don't do a whole lot, and are typically never missed, unless, as I do, you happen to live in a fiefdom where rigorous smog-testing is de rigeur, and not only does the clunking thing have to be there, but it actually has to be proven to work.

In which case, you might want to reconsider, as, unlike putting other smog stuff back on for testing, replacing exhaust equipment isn't exactly a lap dance.
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socal1200r
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Re: Exhaust fitting?

Post by socal1200r » Tue Sep 17, 2013 8:57 pm

John

Ah, the infamous EGR plumbing. Thankfully, I live in the Commonwealth of Virginia, and they don't do emissions testing like they do in AZ and CA. They do annual safety inspections, but they don't check for things like that, just more obvious things like leaky exhausts, missing cats, etc.

So if I'm following your logic, I can just follow this piping and see where it leads, remove it, then cap it off or seal it up? Should be easy enough to do...famous last words, lol...
Robert Brooks
1987 XR4Ti, white, AT
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Re: Exhaust fitting?

Post by John Brennan » Tue Sep 17, 2013 9:20 pm

Yeah, you can remove the pipe along with the manifold (soak the Bejesus out of it with a good penetrant the night before), remove the valve, plug the vacuum line, pound a nickel into the hole in the upper intake manifold (it fits perfectly!), then fab a piece of sheet metal to cover it all up, using the original bolts (or newer, shinier ones, if you like). I think some have welded in the nickel, or an appropriately-sized slug, or just welded up the hole.
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Re: Exhaust fitting?

Post by MarkM » Tue Sep 17, 2013 9:47 pm

To repeat merk23literturbo's suggestion- go with a 3-inch exhaust, especially since you're planning on completely redoing it. If nothing else, get a good 3-inch downpipe and cat.
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Re: Exhaust fitting?

Post by merk23literturbo » Tue Sep 17, 2013 10:13 pm

Image
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Re: Exhaust fitting?

Post by socal1200r » Tue Sep 17, 2013 10:58 pm

MarkM wrote:To repeat merk23literturbo's suggestion- go with a 3-inch exhaust, especially since you're planning on completely redoing it. If nothing else, get a good 3-inch downpipe and cat.
I'm hesitant to go with 3" past the downpipe because of some "advice" I was given when I had my '91 Saab 900 turbo. They said for most street applications, 3" was too big, and I'd lose backpressure, which would make the car run worse and actually lose some hp. So I ended up going with a new cat, muffler, and piping all in 2.5", and the car ran great. When I was holding the 3" downpipe today, I didn't realize how large 3" tubing was, lol!
Robert Brooks
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Re: Exhaust fitting?

Post by socal1200r » Tue Sep 17, 2013 11:02 pm

Is that pic a 3" system? Hmmm...I might have to go with something like 3" downpipe, 3" cat, and a 3" inlet muffler with dual 2.5" outlets, so I can get my dual tips. At least that way, I'd have 3" pipe all the way to the muffler, then dual 2.5" pipes from there with 3" tips. I just think 3" pipe all the way to the back is going to be too much?
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Re: Exhaust fitting?

Post by xrattiracer » Wed Sep 18, 2013 12:53 am

that "advice" about exhaust that is too large is perpetuated by rednecks with small minds mostly. basically those that cant understand that a tuned exhaust system can scavenge better than a completely open one in most applications (typically not turbo) so they think it has something to do with flow rather than resonance. thus actually creating *less* backpressure at the valve than an open exhaust would. hows that for reverse logic? :)
as for the old egr stuff, dont even bother trying to loosen that fitting up. just cut it off. the other end is on the back of the upper intake, big ugly looking valve. remove it and make up a plate to go in its place.
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Re: Exhaust fitting?

Post by Jeff_C » Wed Sep 18, 2013 12:59 am

xrattiracer wrote:that "advice" about exhaust that is too large is perpetuated by rednecks with small minds mostly. basically those that cant understand that a tuned exhaust system can scavenge better than a completely open one in most applications (typically not turbo) so they think it has something to do with flow rather than resonance. thus actually creating *less* backpressure at the valve than an open exhaust would. hows that for reverse logic? :)
as for the old egr stuff, dont even bother trying to loosen that fitting up. just cut it off. the other end is on the back of the upper intake, big ugly looking valve. remove it and make up a plate to go in its place.

+1

To expand a bit on this post, turbochargers operate on the premise that, all other things equal, a higher delta-p across the turbine will decrease the boost threshold (read: it will spool faster). The best exhaust you could have would be none at all ;).

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Re: Exhaust fitting?

Post by merk23literturbo » Wed Sep 18, 2013 2:11 am

Use complete 3 inch system, no 2.5 in the system. The pipe is only going to flow as much as the smallest point, so a 900 inch wide pipe with a 2.5 tip will only flow what a 2.5 inch pipe will flow.
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Re: Exhaust fitting?

Post by In XS 7 » Wed Sep 18, 2013 2:52 am

Yep, I vote for 3" all the way back, I have it like that and 3" in and out muffler,no cat and my car actually runs and sounds a lot better then with the small pipe. :cheers
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Re: Exhaust fitting?

Post by socal1200r » Wed Sep 18, 2013 6:56 am

If this is a repeat, my apologies. Had a reply all typed out, hit "submit", and off it went into the ether...

Anyway, I'm leaning now towards the 3" system, but might go with a muffler that has 3" inlet and dual 2.5" outlets, so I can run dual tail pipes. What has been posted makes sense, at least from a turbo'd car perspective, regarding bigger is better. I'm guessing on a non-turbo'd car, backpressure is more important, but on a turbo'd car, increasing the flow so the turbo can spool up faster and keep spinning is better.

'Course one has to include in this equation that what happens AFTER the turbo is spinning can handle the bigger exhaust, otherwise that could be another chokepoint? But with the 2" elbow off the turbo going into the Saab IC, then 2.5" tubing up to the TB, I think this can handle the 3" downpipe and exhaust, yes? I think I'm going to run with a muffler that has a 3" inlet and dual 2.5" outlets, so I can run dual tailpipes with 3" tips. I can get a 3" universal cat, Thrush all-welded muffler with single 3" inlet/dual 2.5" outlets, and chrome 3" tips with rolled lips for $150 from Summit Racing. I've used them before for cats and mufflers on other cars I've had, all with good results, and prices for these exhaust components are hard to beat. The muffler shop I use will charge me labor to install these pieces, and to fab up the connecting pipes, and they do good work at reasonable prices.

Think I just might get this 3" exhaust done before installing that header...
Robert Brooks
1987 XR4Ti, white, AT
Norfolk, VA

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Re: Exhaust fitting?

Post by RichBaker » Wed Sep 18, 2013 8:04 pm

I live in AZ, does anyone make a header that has a bung for the EGR pipe? I would not pass the emissions check without it.... :?
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