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Doug Thorley/aftermarket exhaust issues

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Old 11-05-2012, 03:14 PM   #1
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Doug Thorley/aftermarket exhaust issues

Serious headache with my 2000 2.7L reg cab...I replaced my entire exhaust a few months ago with a Dynomax 'super turbo' system. Eliminated the front cat. Finished it in a day in my driveway. Initially the smaller muffler sounded much louder than I'd expected, but I quickly grew to enjoy the sound. Everything sounded tight, even though the hangers weren't lined up and the whole system was wired up.

The problems started roughly two weeks later when I took it into a shop to have the hangers welded into the right spots and to have my Doug Thorley 'headers' installed. I also had them weld shut the weep hole on the muffler.

Immediately after leaving the shop I noticed what sounds like a leak from somewhere near the 'headers', either at the engine or the front pipe. It becomes noticeable at 2000rpm and gets worse from there. Of course I took it back in and they assured me there is no leak. The sound is like a "whispering", maybe even a gasket leak. I had three gaskets on the manifold/front pipe connection initially, one flat gasket that fit around both the pipes and two individual crush gaskets. The shop did away with the first.

The noise did not exist before the 'headers' were installed, and my shop is pretty adamant that there are no leaks. I'm wondering if anyone has had a similiar problem. Maybe the heat shield missing from the new 'headers' allows the noise from the fan/belts escape and be heard? EGR problems?

Any help or advice would be greatly appreciated, I've put a bit of money into this exhaust and I feel like a moron, thanks
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Old 11-06-2012, 07:52 AM   #2
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Do you see any black residue around any of the mating surfaces where gaskets go?

Also, you can always let the truck idle, and carefully move your hand around areas of suspected leaking. If you feel the hot exhaust gases pulsing against your hand, then voila.

Another thought is that the Doug Thorley headers just make the noise by the nature of what they are, and you are just not used to them.
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Old 11-07-2012, 02:27 PM   #3
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Thanks for the reply. I've thoroughly checked the entire system and all connections are tight and leak-free. Haven't pulled the header itself but that might be happening soon. Am I wrong in thinking that a performance header should alter your exhaust tone at the tailpipe, and not make noise of its own? I'm not new to building/fixing exhaust but have never messed w/ headers. I'd really like to hear from someone who has installed a DT 511Y-1-C header on a 2.7L, because this just isn't right. No one in their right mind would want their truck to sound like mine. To boot, I've not noticed any gains in performance in any RPM range. Possibly even a bit slower, worse mpg. Whatever.

Thanks again for the response though. I checked out your build, thats pretty amazing. Maybe I'll just paint mine black and call it done.
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Old 11-12-2012, 03:23 PM   #5
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No, headers will make their own sound.... in fact they are one of the most significant changes you can do. Also remember you eliminated the front cat... so that will also change the resonance frequency.

My DTLT headers on my v6 do make a bit of that "whistle" type sound... it's just a bit diffrent.

Also in theory, you should get better gas millage and more HP (lower torque).
- This only applies if you drive exactly the same as before (lets face it, new noise = more skinny pedal = less mpg)
- Lower back pressure will cause your torque to go down, but HP to go up
- The ECU probably isn't going to be able to auto-tune itself very well to the new setup on it's own. I know on the V6 URD makes a MAF tune calibrator that would actually allow you to maximize your gains (and you can lean toward performance or fuel saving depending on the map). So, if you are seeing worse power and millage... tune is most likely the issue.
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Old 11-13-2012, 07:04 AM   #6
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Thanks for the replies. I ended up taking them off, found a slight gasket leak on 4th cylinder, and re-installed with permatex. Thought that might have been the issue but the noise persisted. I put the factory manifold back on the other day and everything sounds great on the Tacoma again. I'll try to sell the DT header on here seeing as its only been used for a month. Thanks again
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