4" or 5" Exhaust

[SeEKandDESTROY2]

So a few weeks back I cut the exhaust on my truck before the cat and just just a straight pipe out the side. However it has been brought to my attention that the cold temps we get out here (Sometimes down to -20)could get to my turbo, after shutting down. I love the growl I get with the current setup but I need to do an exhaust so I don't run into issues.

Do you guys reccomend a 4" or 5" straight pipe kit with a down pipe? Where can I get the best deal? Thanks, Pete

[SpudZooka]

You only need 5" for sound, other than that there is no hp gain. And I dont think you have to worry much about the cold air getting to your turbo if you cat is still in tact, the cat should be hot enough to warm the air before reaching your turbo. Then again -20 is kinda cold....

[choupique108]

4inch is plenty for performance, 5" is just for asthetics and sound. I have a 5" and i love it. As far as your DP, i think the biggest you can go on a OBS is a 3.5 inch

[SeEKandDESTROY2]

I don't have a cat anymore, just down pipe to straight pipe. I was going to do the 3" down pipe, just wondering if i'd see any advantages between a 4" and 5"

[SpudZooka]

Originally Posted by SeEKandDESTROY2

I don't have a cat anymore, just down pipe to straight pipe. I was going to do the 3" down pipe, just wondering if i'd see any advantages between a 4" and 5"

In that case then yes, cold air would get to you turbo easy. You can get a 4" downpipe but those are *beep*beep*beep*ing hard to put on. Alot of beating and your passenger will most likely have a foot stool to rest his/her foot on while riding with you. 3" downpipe to 4" stright pipe is same performance as 5" stright. Unless you are cranking out extream HP 600+, 3" DP 4" SP will do fine. As said before, 5" is for sound.

[GM Duraturd]

What do you mean cold air getting to the turbo???? If its -20 out than cold air will get to everything no matter what exhaust is on the truck. Am I missing something?

3" downpipe, and 4" or 5" back. 4" is all thats needed and sounds great, 5" looks cool and sounds really deep.

[TANPOWERSMOKER]

Originally Posted by GM Duraturd

What do you mean cold air getting to the turbo???? If its -20 out than cold air will get to everything no matter what exhaust is on the truck. Am I missing something?.

Im missing somthing to ??? Any way, farmboy diesel has a budget 4'' exaust with or with out muffler. Dimond eye sells 4" 5" and 4" duel also stanless 4" for a little more.

[storkerlovr]

ok just get the 5in! it sounds a lot better. i love my 5in....but now i think thats even too small haha

[TurboTPI]

Originally Posted by GM Duraturd

What do you mean cold air getting to the turbo???? If its -20 out than cold air will get to everything no matter what exhaust is on the truck. Am I missing something?

Haha, thats what i was thinking. When the truck is off, the turbo will be ambient air temp no matter what. Cold air doesnt hurt turbos

[SpudZooka]

Originally Posted by TurboTPI

Haha, thats what i was thinking. When the truck is off, the turbo will be ambient air temp no matter what. Cold air doesnt hurt turbos

I think he is thinking in terms like how they say not to run open headers on an engine, cold air hits the exhaust valve and can warp/weakin them. If you exhaust is to short and cold air can rush up the exhaust I guess it could warp a hot side of a turbo like it could exhaust valves? Maybe not.

I dont think diesels exhaust get quite as hot as gas engines under normal conditions.