Well my winter project for the truck is new exhaust. I have already tweaked the pump and added a 16cm housing and K&N filter. I pull a 3500lbs Jeep with a 9ft camper in the box. So say 6500lbs total. With the above combination I can't use full throttle on extended hills as my pyro gets too high, 1100* post turbo. So I want to try opening up the exhaust to 4".

I'm pretty cheap and have a fully equipped garage with mig. I want to build my own but am not sure about the downpipe from the turbo. Can a 4" down pipe be used or does everyone use a 3" and then open up. Can I find a 4"(or 3") fairly easily at a truck shop? How much will opening up the exhaust decrease my EGTs?


Also I live in Alberta and heard there was a place in BC doing 4" exhaust. Anyone have a contact for them?

Thanx.

 

You can use a 4" downpipe on your 1st gen truck. You'll need an adaptor to take you from the 3" outlet of the stock turbo to the 4" inlet to the downpipe. We also need to "tune" the downpipe for each truck as no two are the exact same. It may also require an adjustment to the dipstick on auto trucks.
We also do custom installs on 4" systems for our trucks.
They take time and literally custom cutting/welding/hangers to make it work and the 4X4's are the worst....but it can be done.
Give the shop a call if you're interested at the toll free line:
866-888-9396... as for pastor bob or harry.


Pastor Bob.

 

I use the factory downpipe and open up to 5 inches after the transfercase because of the tight fit between the frame and TC.
Just my 2 cents

 

Not to steal some contacts from Bushy, but there is a 4" bending shop in Red Deer by the name Flo-Pro that makes 4" kits, not sure if they do the 1st gen stuff, but the tail end off of the newer trucks will work.. I have it.

Also check out Unlimited Performance in Cowtown and talk to Andy. They have 4" stick there.

J-eh

 

Hmm that's weird I could have sworn I posted a reply yesterday. Oh well.

Anyway thanks for the tips guys! I'm pretty comfortable fabbing my own exhaust I'm just not sure what to do about the down pipe. If I understand correctly the outlet on the turbo is 3" and I need to get it to 4". What size is the stock exhaust? Is there an off the shelf part to go from the 3" outlet up to 4"?

Also how much will this reduce my EGTs? Noticable or hardly at all? Really need to get them down so I can keep that pedal to the floor!

 

Stock setup is 3". Any heavy truck parts store will have the exhaust adapters and tubing you need, or you can get them online from Airflow Systems. If you're going from stock with a muffler to 4" straight or bullet muffler I'd predict a drop of 200 degrees under heavy throttle.

 

I realize there would be lower operating temps but has anyone done a real check to see what kind of added fuel savings can be seen on the chang over? I too would like to do the same trick and also have my own shop with everything necessary in the way of tools. I have not found anyone near here that has the bending ability for anything over the standard automotive sizes.
Have fun
Allen

 

We were talking about flow and efficiency on another thread here, and there was some discussion on the 2nd gen forum too.

After reading here and other places, I have a plan, as yet untried, that I think will yield the best results . . .

When you have a sudden change in the diameter of a pipe, it cause turbulence in the flow. This turbulence effectively increases the back pressure in the pipe. The amount of turbulence seems to be proportional to the the flow rate.

The Exhaust gasses are hotter up next to the turbo, so the flow rate is higher there (in terms of cfm -- obviously in terms of moles, the flow rate has to be basically the same from one end of the exhaust pipe to the other), and it seems as though the restrictive effects of sudden transitions in pipe diameter are more noticible when the transition is made up near the turbo.

Based on that logic, I plan to make a down-pipe that has a "stock" 3" bend at the turbo and then uses the entire straight section between the first and second bend to taper up to 4 inches, then run everything 4" from there back.

I also think a little header wrap around that first bend and down the straight section might help things.

If anyone has more time than I do, and the inclination, I would love for them to try it out and let me know how it works .

My $.02

 

I built my own 4" system from the turbo back. I went to the local IHC dealer where they deal with lots of mid size trucks.
I bought a 10 foot piece of 4" pipe for about $40.
I bought a dynomax muffler out of Jegs for about $70. It is a full 4"in and out and is straight through.
I had about 4-4" mandrel bent elbows left over from installing Exhaust brakes on mid size trucks. I believe you can buy elbows at a good truck shop.
I Made my own adapter going from the turbo flange to the 4" elbow. It is not real pretty but works. I cut the stock flange about 1 inch from the clamp. Then I took a mandrel bent elbow. to change a diameter 1 inch, you will have to take about 3 inches out of the circumference. So I took 3-1 inch pieces and cut them pie shaped and reduced the size of the 4" pipe to 3" and then welded the elbow to the stock flange.
If I had photos I would show you.
There is enough room to run 4" betweeen the frame and the trans on manual transmissions.
I built the whole system in 1 afternoon. It has been on the truck for more than a year. I dont know how much EGT or fuel milage change there was if any.
Good luck You can PM me if you want.

 

I'd be kind of surprised if you saw 200*F... I think that is a bit optimistic.

Going from a stock system to a full 4" from the turbo back will likely result in about 100*F plus or minus a few. It gets better if you do the intake air (air filter/airbox), and also turbo upgrade. These are the primary "air in/air out" components.
1100*F post turbo is WAY too hot.... do not go there for any length of time, for any reason.
This well known and fairly accurate rule of thumb applies here....
for every one pound of boost you can add roughly ten degree's "F" to your pyro reading. This formula works fairly well up to about 24 pounds boost. It goes a bit goofy after that.
Yes, I have "tested" this on my own truck and it's pretty close.
So, if your pyro says 1150*F post turbo and you are at 24 psi boost you are now running approx. 1390*F at the turbo inlet... way too hot.
1200*F pre turbo near continuous duty cycle (watch water temps if you are pushing it at this level for very long)
1350*F >>> ONE minute out of 5, with good cool down afterwards
1500*F>>> Stand by for Chernyobl at any time depending on your luck quotient...unless you know all the words to La Bomba...
Pastor Bob...

 

Has anyone received any better fuel mileage on the exhaust changover? I am getting just a bit over 22 mpg empty running at no more then 65 mph with an automatic. I am interested in the economy plus temp. If I cant get both then it may not be worth the $$ and time. Im not interested in raising the noise levels.
Have Fun
buckshot

 

I used a 5" pipe right after my 3" down pipe then to a 4" over the axel. the only reason 5" was used was because they did't have any 4" pipe left. Sure works good.. I was getting 11.8 MPG pulling my 30' 5er going to Pensacola Fl from Okla. City Ok.