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Discussion Starter #1
how much does it benifit to get an aftermarket down pipe? is it worth it, or is the stock one big enough? just wanting to get the egts down as much as possiable without having to go to some sort of injetion-i.e. water
 

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If you have an Allison, there currently isn't any aftermarket downpipes available.
 

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If there isnt a downpipe available then why is there one on my truck? Dynomax offers a full turbo back system.
 

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He said 'aftermarket' downpipes available.



Pretty much all aftermarket exhaust manufacturers advertise turbo back even though they are only downpipe back. We've seen it many times. Sorry.
 

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All I know is I def. changed my downpipe to 4 inch on my truck.
 

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Lets see a pic of the Dynomax downpipe, and your old stock downpipe.
 

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There is NO replacement down pipe available unless someone fabricated their own.

What is a downpipe?

It's the pipe that you can't even get to where it's bolted to the back of the turbo. When they designed it they had tight contraints to work with and ended up with a flattened out cobobulation that no one makes a replacement for.

Make a BS'r out of me


Here is a real downpipe.... the one in front. It clamps directly to the back of the turbo and can be done in 30 minutes or less.

Edited by: hoot
 

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MBRP said:
Rest assured.................... its coming!!





MB

If you wanted a non biased trucks opinion, let me know. It would probably work real well with your "cool duals"
 

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Discussion Starter #12
when i said down pipe i meant anything other than stock. thats what i thought the definition was?? i already have a 4" exhaust from summit that was advertised as being downpipe back, but its after the downpipe. is there a "pipe" from the turbo to the first clamp-right before it bends to go to the back of the truck- for the d-max. if so how will it lower egts??
 

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Moss, you are correct in your description, there is none available yet, but MBRP just said they are working on it. I know of a guy that built one for his 6 speed.
 

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White Duramax said:
I know of a guy that built one for his 6 speed.

That why I made sure to say "If you have an Allison".
 

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Discussion Starter #15
i of course have the ally--nearly smoked!!
 

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What about this? Is it not "turbo back" as the advert says?


http://www.ttspowersystems.com/exhaust_gmdiesel.htm


I even talked to them about the "turbo back" vs "cat back" (which for my truck apparently means from back of down pipe back) and my understanding was that it *is* a new down pipe and he knew I had an Allison...
 

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It is still not the actual down pipe, it is the pipe that is connected to the downpipe. The downpipe bolts directly to the turbo housing and runs down at an angle to the bottom of the engine and stops where the passenger exhaust manifold is. What everyone else calls the downpipe, which it is acutally just the first piece of the regular exhaust, hooks up to here and goes reward. I hope I didnt confuse anyone.
 

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The downpipe bolts to the rear of the turbo and snakes down behind the engine and stops at a v-clamp flange.


All of the exhaust systems currently for sale, including the one above (which is actually labeled as "turbo down pipe back") start at the v-clamp flange and go from there. This replaces the "cat", or if you buy "cat back" then they leave that piece out of the kit. In either case, the restrictive, flattened factory downpipe is still attached to the turbo.


I spoke to Steve Cole (TTS) at the LA dyno day, and he has an interesting downpipe in development, hopefully it'll be out soon.


I'm also anxious to see what MBRP comes out with, their fully polished stainless systems are a bit pricey, but look like a million bucks. If you're building a super clean street truck or a show truck, it's a must have!


I replaced a CT Sonic pipe on my Yamaha Raptor with an MBRP polished stainless pipe, it turned a nice gold color, I never polish it. I purchased it from Craycraft Racing, in Aledo, TX and they happened to be in Glamis, CA for 4 Stroke Wars II. They showed off their engines and the full line of MBRP exhaust systems.
 

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socaldmax said:
All of the exhaust systems currently for sale, including the one above (which is actually labeled as "turbo down pipe back") start at the v-clamp flange and go from there.

Actually, if you read the description above the pricing categories, it says "Turbo Back". It goes on to say specifically "replacing the stock 3" down pipe". But thanks for the info.


I guess when I asked him specifically if the down pipe would make any real difference, he was just talking about that front pipe. I know he did talk about the various joints where things tied in and such (which I was not in a position to look at while talking to him) so I'm sure the misunderstanding was mine and not intentional on his part. I was very impressed with his help and customer service. Still, seems the description should/could be a little more clear...


Now I wonder if I should delay my order (which I planned to place next week) till this new "interesting" down pipe option comes available. He previously indicated that the more expensive "down pipe back" system made little to no difference in most situations. I wonder if the down pipe will be worth extra money for those not looking for every last bit of performance and degree of EGT reduction...Edited by: BadDog
 

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Bad Dog, you're right, I agree, it is a bit misleading. Honestly, most ads are even more confusing. Kennedy's exhaust description is clear "from downpipe back" but all of the rest I've seen were borderline deceptive.


As for the original question - would a new downpipe help. Yes, on a high hp truck it would probably help quite a bit with EGTs at the upper end. Even with trucks making 125hp extra or more, I'd *guess* that it would make a worthwhile difference.


Everyone who has looked at the factory downpipe says it's all smashed and restrictive.
 
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