3" exhaust on a non forced induction truck?

[reffug]

is anybody here w/o forced induction running a 3" exhaust?

if so why and what has been your experience with it?

[jamisobe]

With headers and a custom mandrel Y-collector.

Gas mileage ranges from 15 to 17 mpg with good pick up. It sounds neat though I initially had to deal with drone at highway speeds.


This is what I used for the drone:



These photos are in order from the
Downey headers to the Flowmaster 70 series muffler:



















At normal throttle it sounds stock, but at WOT it sounds racey.

[Riad]

I have been thinking of doing the same thing. Are those headers custom made or some kind of universal fit? I am hoping to be able to reuse the OEM header with 3" down pipes and cats. Do you get any extra heat for not having the shields on?

[Riad]

Never mind, I found the headers. I am still interested know about the heat question.

[jamisobe]

Originally Posted by Riad

I have been thinking of doing the same thing. Are those headers custom made or some kind of universal fit? I am hoping to be able to reuse the OEM header with 3" down pipes and cats. Do you get any extra heat for not having the shields on?

The headers are discontinued Downey headers (edit: were discontinued). The problem with headers is that the few attempts made used the inefficient OEM style collector which limits power regardless of the rest of your exhaust. Exhaust flow is only as good as its most restrictive point.

My collector is custom made from a Y-pipe and welded into place. If needed, it would be difficult to remove the header/collector without cutting.

What you are proposing is to use the existing manifolds, which are good, and fabbing new down pipes. Makes sense, but you won't need 3" before the Y since you will only have 3 cylinder banks off of each manifold. The key is using a Y (Flowmaster Y) instead of the OEM arrangement which favors one manifold evacuating easier over the other. That causes unwanted turbulence.

My installation required some mild cutting/widening of the fender (you can see this in one of the pics) and the bending of a body mount washer (you can see this in another pic). It's tight but it can work by cutting mandrel tube into shape, tack welding, and then final welding.

I think 2" off of the manifolds routed to outside the frame with a Y into 2.5 or 3 would work very good.

The heat is a minor issue (no issue actually) for me. I haven't noticed any difference, especially from where I sit. If heat were an issue there is wrap around heat insulation available. The wife mentioned a warm foot on a long trip once, but her mention wasn't a complaint and it didn't even register on the Richter. I haven't heard anything since.

The 3" over the frame was completed about a month ago. It's tight, but it works. Same thing for heat there. No problem for me or my wife and since I rarely have 2nd row passengers I am not too concerned, but there is heat wrap if I ever get the itch.

[jamisobe]

Originally Posted by Riad

Never mind, I found the headers. I am still interested know about the heat question.

Interesting. The last time I checked with Downey for somebody else they had stopped producing. When I bought the headers 6 years ago they came with a lousy OE style collector to cat connection. That link says they no longer supply a collector arrangement.

It can be done, but it takes some skill. When I first explored this 6 years ago the first couple of shops I went to were not on board with what I wanted. They either didn't have the skill or didn't have the time.

[Riad]

Originally Posted by jamisobe

It can be done, but it takes some skill. When I first explored this 6 years ago the first couple of shops I went to were not on board with what I wanted. They either didn't have the skill or didn't have the time.

Thanks a lot for the insight . Agree. Shops around where I live most likely are the same way. I am going to do this on my own and take as long as possible before I put it on. I am going to follow the cut and tac weld process you mentioned. Hopefully my OEM pipes hang in there long enough otherwise I'd have to park it in the garage and force myself to speed up the build, which I hate doing. I like your setup BTW. Very nice and clean build. I am planning on using flanges as many as possible. That way if I have to replace any pieces (i.e cats, mufler, down pipe, etc), I should be able to just unbolt, weld in new flanges and then bolt it back in there. Hopefully my plans work out OK.

[jamisobe]

Originally Posted by Riad

Thanks a lot for the insight . Agree. Shops around where I live most likely are the same way. I am going to do this on my own and take as long as possible before I put it on. I am going to follow the cut and tac weld process you mentioned. Hopefully my OEM pipes hang in there long enough otherwise I'd have to park it in the garage and force myself to speed up the build, which I hate doing. I like your setup BTW. Very nice and clean build. I am planning on using flanges as many as possible. That way if I have to replace any pieces (i.e cats, mufler, down pipe, etc), I should be able to just unbolt, weld in new flanges and then bolt it back in there. Hopefully my plans work out OK.

Thanks.
FYI, the stainless steel band clamps helped me immensely and they do not leak.

Since you are doing your own collector try to tuck the exhaust up in the side gunnel as much as you can. You can see from one of my pics that less than half my cat is visible. If the side heat shield was still there you would not see the cat or the exhaust at all.

Good luck and God's speed.

[landtank]

My truck is in the shop as I write this and I went with a 2.5" exhaust. I talked with a local guy who put his on and he thought that 3" over the frame was too tight. From the look of things it seems it can be done.

I went with a flow master muffler and a second resonator as I want this thing quiet. I should have it back Friday and am interested in seeing how it does,

Jamisobe, I'd like to see my MAF on your truck. The stock units are so restrictive and with your exhaust it would be interesting to see how much more you can get out of a stock engine.

[jamisobe]

Originally Posted by landtank

My truck is in the shop as I write this and I went with a 2.5" exhaust. I talked with a local guy who put his on and he thought that 3" over the frame was too tight. From the look of things it seems it can be done.

I went with a flow master muffler and a second resonator as I want this thing quiet. I should have it back Friday and am interested in seeing how it does,

Jamisobe, I'd like to see my MAF on your truck. The stock units are so restrictive and with your exhaust it would be interesting to see how much more you can get out of a stock engine.

It's tight but it worked. I originally considered using an oval section over the frame, but when I measured it appeared to be doable without that piece. The small heat shield occupying that space above the frame had to be removed.

What size Flowmaster did you go with? I was able to fit the 70 series muffler in the stock location tighter than the larger, stock muffler. When I first ran the 3" exhaust 6 years ago there was a drone, but I installed the silencer pictured above from Jegs. It's sounds stock unless I really get on it.

I too think your MAF may contribute favorably to my performance. I am sure that item belongs on my short list of items to be purchased "for the cruiser". Any reports on change in MPG?

[landtank]

Originally Posted by jamisobe

It's tight but it worked. I originally considered using an oval section over the frame, but when I measured it appeared to be doable without that piece. The small heat shield occupying that space above the frame had to be removed.

What size Flowmaster did you go with? I was able to fit the 70 series muffler in the stock location tighter than the larger, stock muffler. When I first ran the 3" exhaust 6 years ago there was a drone, but I installed the silencer pictured above from Jegs. It's sounds stock unless I really get on it.

I too think your MAF may contribute favorably to my performance. I am sure that item belongs on my short list of items to be purchased "for the cruiser". Any reports on change in MPG?

I don't know which muffler is being used as I went with their recommendation. No concrete MPG numbers that I know of, but some have reported and increase.

[Nay]

I want to see clearance pics with the 2.5". I am killing my stock muffler and the bend in the tube that comes out near the slider (it is a slider ). I'm probably down to 1.5" , although with the MAF mod it was still killer in the high country @ up to 12K feet this last weekend and delivered 14 mpg in a mix of 1/3 city / 2/3 highway driving.

I really need to redo the exhaust behind the cats and am looking for ideas.

[landtank]

I'll post some pics of my system when I get it back.

[jamisobe]

I really liked this shot. It gives a good idea of the ground clearance gained for the exhaust. The side heat shield that hangs down beyond the body pinch joint has been removed.


Here is a shot of the tight clearance between the frame and the exhaust. There are rubber insulators on the exhaust hangers, but there is less flex than needed for the exhaust to touch the frame here. There is enough room to gain a little more clearance than what I achieved. I could go back in the future, if needed, and redo the small section from the cat to the band clamp in this pic. I don't think it will be an issue.

[hill]

Landtank..... id be very curious to hear about your set up with new muffler... did you go with headers?

[landtank]

Originally Posted by hill

Landtank..... id be very curious to hear about your set up with new muffler... did you go with headers?

No, I have a Turbo in the works and had them install a 3" hi flow Cat in prep for that. I realize that I'm giving up some performance withthe back end being 2.5" but it's all about compromise and I think it will be good enough for me.

[jamisobe]

Originally Posted by landtank

No, I have a Turbo in the works and had them install a 3" hi flow Cat in prep for that. I realize that I'm giving up some performance withthe back end being 2.5" but it's all about compromise and I think it will be good enough for me.

You might try to have a listen to your turbo without a muffler especially with it necking down from 3 to 2.5. I have a friend back in Ohio with a Lingenflelter/Callaway twin turbo Vett that puts out 900-1000hp to the rear wheels on the dyno(depending on which fuel/fuel program he was running). He ran no cats and no mufflers. Just custom dual pipe all the way to the back. It sounded bone stock, until he stomped on it (it looked bone stock too ). He said that doing tricks are what make exhausts quiet and turbos are very tricky for exhausts. I know its true because I saw it (and road in it ).

[landtank]

Picked up the truck a few minutes ago and it's louder than I had hoped for but not by much. It's actually not as loud as the Borla that was on there. They did a great job and everything is way up under the truck between the frame rails. I also did a side exist incase I go with a 4x4 labs rear bumper.

[concretejungle]

went out and snapped some pics of jfz80's 3 inch exhaust. His is over the frame rail. The guy said that was the last time he will do it since it was such a b!tch to do His gas tank is out that is why i got that one side shot.

His is kind of loud and needs to add a resonator.

[concretejungle]

couple more pics of his 3" exhaust.

[concretejungle]

last one.

[Tapage]

Does anyone here do something like this ?

[jamisobe]

Originally Posted by Tapage

Does anyone here do something like this ?

What? Can you say that again ...I can't hear you over the exhaust.

[Riad]

[jamisobe]

Originally Posted by landtank

Picked up the truck a few minutes ago and it's louder than I had hoped for but not by much. It's actually not as loud as the Borla that was on there. They did a great job and everything is way up under the truck between the frame rails. I also did a side exist incase I go with a 4x4 labs rear bumper.

How long till you expect to have your turbo ready?