4' turbo downpipe

Tdahl · 03-27-2008, 09:17 PM

I have a 05 LLY. I am looking fo a 4" downpipe to go from the turbo to my 4" exhaust. Does anyone know where to get one. I ordered a diamond eye turbo direct pipe but its only a dinky 3".

Maverick684 · 03-27-2008, 09:27 PM

I was going to tell you to try diamond eye, but I guess that won't work. You may want to PM bryan from ATS here on the forum. I think ATS uses 4in. downpipes on their aurora turbos, it's possible you could that piece individually and mount it up.

**05_LLY** · 03-27-2008, 11:21 PM

There is really no need for any more than the diamond eye pipe, performance gain with the bigger pipe is not a noticeable gain, with the diamond eye pipe ive noticed and AVG. 150deg egt drop though on a stock turbo truck. HP gain from the stock down pipe to the DE pipe is almost none, a bigger pipe would be the same.

Just for thought, the stock turbo outlet is barely 2.5 inches?

Patches4 · 03-28-2008, 11:07 AM

Quote:

Originally Posted by Tdahl

I have a 05 LLY. I am looking fo a 4" downpipe to go from the turbo to my 4" exhaust. Does anyone know where to get one. I ordered a diamond eye turbo direct pipe but its only a dinky 3".

Don't know about how much difference it makes, but going from 2.5 to 4" has to be better than 3". You can get the 4" down pipe from "Pinnacle Performance Exhaust", if you still want one. I bought the entire turbo back system from them and very pleased with it!

**samdweezel05** · 03-28-2008, 04:04 PM

If you are starting with a 2.5" hole it won't do any good to go bigger than 3". Remember, backpressure is your exhaust valves best friend. This is the same for the rest of your exhaust. If you arn't making big horsepower you will never need anything over a 4" exhaust. I noticed no performance gain with my 4" exhaust over the stock exhaust. It sounds better and looks cool. My EGT's droped about 150*.

Phil

muskrat · 03-28-2008, 04:14 PM

You need to go bigger than 3". Your EGT is going to be to high. Stock is 3 and a half inch. Put on 4" and also put on a air intake if you going to program it.

**samdweezel05** · 03-28-2008, 04:23 PM

With my factory exhaust and intake and my Edge on level 5 the highest EGT I ever saw was 1200 degrees. I had to melt the tires off the truck to get it there. The horsepower you would have to make to use a 4" pipe to it's fullest would push your factory turbo out the tail pipe. You may drop EGT's a little, but is it worth it?

Phil

Patches4 · 03-28-2008, 04:55 PM

Quote:

Originally Posted by samdweezel05

With my factory exhaust and intake and my Edge on level 5 the highest EGT I ever saw was 1200 degrees. I had to melt the tires off the truck to get it there. The horsepower you would have to make to use a 4" pipe to it's fullest would push your factory turbo out the tail pipe. You may drop EGT's a little, but is it worth it?

Phil

I agree that there may not be a big difference between exhaust sizes, but I have always gone by the addage that if you can't get air in, you can't get air out and if you can't get air out, you can't get air in.
I pull 10,000 lbs of boat and on a steep hill, you need large exhaust to kept the EGT's down, especially if you are running a programer like the Edge Juice. Even at that, I have seen some nasty EGT's. Nice thing is the Edge will defuel the engine if they get too high. Blows me away at how fast the EGT's go up just stepping on it alittle! I have heard the same thing that exhaust and intakes don't make that much difference over factory. Edge strongly recommends both if you are going past #3. I followed the recommendation and have never had a problem.

**samdweezel05** · 03-28-2008, 05:24 PM

And I agree with you. Adding a trailor will bring up the EGT's but I didn't hear any talk about a trailor. I also agree with your air in, air out. My issue would be with the factory turbo. It will only pass so much air before IT becomes the problem. EGT's are measured before the turbo so no matter how big the pipe is after the turbo, if the hole in the turbo is only 2.5", a 4" pipe won't do much as far as lowering EGT's or adding power. I am all for the "Go big or go home" but sometimes too much is just that, too much.

Phil

Patches4 · 03-28-2008, 05:38 PM

Your probably right - at least it seems to make sense. I just felt that if your going to the expense of an exhaust system, you might just as well go all the way, it only costs alittle more to go first class.

Anyway, I also believe that "if you can't run with the big dogs, stay home on the portch". I really didn't see much if any difference with the air intake either, but since they recommended it, it would be hard to complain if you didn't follow their recommendation. Let's face it, no matter what you do, if you do it right the first time, you won't have to do it again. It's only my 2 cents, but like you say, "Bigger is better".