6637 question
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Senior User
Joined: Apr 2010
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From: Walla Walla, Wa
6637 question
I ordered my 6637 kit yesterday night from clay and just wanted to know if there'll be a noticeable difference as far as performance, MPGs or both once installed?
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
I did notice a 1MPG increase in city driving, but as I said that was with an exhaust also.
The one thing you will notice is it will be louder.
Congrats!
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Senior User
Joined: Apr 2010
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From: Walla Walla, Wa
When I installed mine I also did a 4" exhaust back from the turbo. Most people would recommended getting some sort of exhaust upgrade because when you upgrade the input you should upgrade the output, too.
I did notice a 1MPG increase in city driving, but as I said that was with an exhaust also.
The one thing you will notice is it will be louder.
Congrats!
I did notice a 1MPG increase in city driving, but as I said that was with an exhaust also.
The one thing you will notice is it will be louder.
Congrats!
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
No worries, I'm in the same boat. Doing one before the other wont hurt ya, but you wont get the full benefit of either with out the other.
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Senior User
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From: Walla Walla, Wa
I do have a question though about doing my exhaust, I've got an appox. 8 ft section of 409 stainless pipe from exhaust on my boat that I never got around to doing, would it be a straight enough shot from the down pipe to an aftermarket 4" tail pipe to use that pipe or would i have to use a kit to have the proper bends in it??
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
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From: Missouri
Once you get past the down pipe its a straight shot to the rear axle. You would either need to go up and over the axle or just cut the exhaust before the axle and have it end at the front of the bed area. But I believe you would need a 4" down pipe too, unless you adapted it to the factory down pipe, but then youre really not getting any benefit.
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Senior User
Joined: Apr 2010
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From: Walla Walla, Wa
Once you get past the down pipe its a straight shot to the rear axle. You would either need to go up and over the axle or just cut the exhaust before the axle and have it end at the front of the bed area. But I believe you would need a 4" down pipe too, unless you adapted it to the factory down pipe, but then youre really not getting any benefit.
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9 ECHO 1
Joined: Aug 2009
Posts: 12,467
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From: Missouri
I'm not sure. Ive never seen a stock muffler, mine had a round aftermarket one when I did my system. I would recommend getting an aftermarket system. Check my sig for the one I got. Its only about $300. If you just replace the down pipe and intermediate pipe you still how a 3" muffler and tail pipe, not to mention the stock muffler is pretty restrictive.
I would just save up and get a full kit. It will be better in the long run IMO.
I would just save up and get a full kit. It will be better in the long run IMO.
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Beer Fridge Finder
Joined: Apr 2003
Posts: 14,988
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From: Savannah, GA
I did 6637 only and went from (truck by itself, cruise set, 73mph, 90 miles) 17.1 to 19.0. I installed it last Friday before I went to my camp site. Same stretch of road, cruise set same. It was as even of a test as I could do.
And driving it to work and back I have noticed a slight increase as well. I used to get 15.9-16.3 ish in combo country and city driving. Now I seem to be hanging closer to 17.
Oh and for the record it's a 2000 crew cab long box 4x4 3:73 gears, no mods other than the air filter. Well and some guages, and the previous owner put a thumpity thump stereo in it, but that doesn't effect mileage much.
And driving it to work and back I have noticed a slight increase as well. I used to get 15.9-16.3 ish in combo country and city driving. Now I seem to be hanging closer to 17.
Oh and for the record it's a 2000 crew cab long box 4x4 3:73 gears, no mods other than the air filter. Well and some guages, and the previous owner put a thumpity thump stereo in it, but that doesn't effect mileage much.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
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From: Rio Rico, AZ.
You'll notice that it's noisier, but with the turbo quieting things down it will be like putting a set of glass packs on a gas engine.
Nice mellow rumble.
Fleet Mechanic
Joined: Jul 2005
Posts: 1,800
Likes: 52
From: Southern Colorado
I just did a 6637 - nice MPG gain. Along with a lighter foot on the freeway and fixed boost leaks, I went from high 13s to high 16s, for MPG. I have a stock exhaust system and no other significant mods other than the Hutch mod.
You will hear turbo farts (I believe that's that term) on up shifts and if you quickly lift off the throttle under boost. I'm ok with that. I feel a stronger off-the-line and mid-range pull.
Protect the 6637 or sleeve on the filter by covering any rough spots under the hood where the filter sits. What I'm trying to say is that after you remove the factory air box be aware of the sharp plastic bits that remain, as they will wear through your cloth cover, if you have one.
You will hear turbo farts (I believe that's that term) on up shifts and if you quickly lift off the throttle under boost. I'm ok with that. I feel a stronger off-the-line and mid-range pull.
Protect the 6637 or sleeve on the filter by covering any rough spots under the hood where the filter sits. What I'm trying to say is that after you remove the factory air box be aware of the sharp plastic bits that remain, as they will wear through your cloth cover, if you have one.
Senior User
Joined: Jun 2010
Posts: 362
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From: middlesex county, nj
I have a home made 6637 with donaldson filter, and just cut the muffler off my 99,5 350 dually, its loud, but I like the noise, don't know about mpg, but its crisp when I jump on the go pedal, so opening up the intake and exhaust gives a nice seat of the pants boost, and she sings like a bird at all speeds
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Senior User
Joined: Apr 2010
Posts: 268
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From: Walla Walla, Wa
I have a home made 6637 with donaldson filter, and just cut the muffler off my 99,5 350 dually, its loud, but I like the noise, don't know about mpg, but its crisp when I jump on the go pedal, so opening up the intake and exhaust gives a nice seat of the pants boost, and she sings like a bird at all speeds