Engine/Transmission (1998.5 - 2002) When is 5-inch necessary?

[WadePatton]

At what general power level does a 5-incher really become beneficial?



I don't think I'm going that far, but would like to be prepared. I ask because many vendors carry 5 inch for the PSD, but it's not as common for the CTD.



I'm going to do it anyway--because I can.



And how loud is it compared to a 3-inch res. only system?



TIA

 

[BRI7070]

Its 5 " time when...

You are boared lookin at sone 5" line and elbows thinkin that that would be cool. . then you look at the 4" exhaust on the race car and start thinking... if i split the 4" in the right way I could adapt them to the 5" giving me 2 4" lines slip on 2 two chamber flowmasters (race car needed new exhaust anyway)modify a 3"-4" reducer and a 4"-5" reducer. tap that into the turbo and off you go. I am currently about to fit up the 5" to turbo. Have made the 5" in to 2 4" split with the flowmasters and 14" long dumps. BTW my truck is all stock. thats when you need 5"

 

[Mactruck]

I just put a Bully Dog 5" on my truck and I needed it! I was running the stock system straightpiped, and was having a lag problem with my new PDR HX35.

I put that new system on and WOW. Spools up very fast and it has great reduction in EGT's. I cannot compare it to a 4" though. Although the 4" would have done the job just as well maybe.

However, I believe most of these 5" systems (like mine) aren't a true 5" turbo to tail. There is no room for installation for a 5" where the downpipe goes and next to the transmission. Mine goes from a 3" collector at the turbo to 4". Then comes down next to the transmission. After the transmission bracket it enlarges into the 5" for a few feet, then feeds into a 5" inlet of the muffler. the rest is a true 5".

I like mine

 

[WadePatton]

let me re-phrase that

When does 4" exhaust become a (always more than one) limiting factor in developing HP with acceptable EGT's?



If 3" chokes at a little over 300 then 4" has to have a limit too.

 

[Blkdawdg]

This subject has been brought up before and I believe that the conclusion was that you won't gain anything from going to a 4" to a 5" (other that you'll have more of a "WOW" factor with the 5"). It probably has something to do with the maximum size turbo that we can use.

 

[Idaho CTD]

Wade,

If you figure the area of a 3" pipe vs. a 4" it is nearly 2x the area. So in theory if 3" is only good for 300hp, 4" is good for almost 600hp. So 5" wouldn't be NEEDED until you've reached at least 550-600hp.



Nathan

 

[WadePatton]

Dam Idaho, that's what Joe D said! (in PM) That a 5" becomes necessary just under 600HP. I 'spect I'll be over-PIPED! Maybe I'll wait a bit.



Well heck, I needed injector money anyway.

 

[nickleinonen]

5" is needed for the ultimate factor!

 

[Vaughn MacKenzie]

Even as mildly BOMBed as my ETH is (DD2s only) it is amazing how much exhaust velocity comes out of the tailpipe of my 5" system at idle. I do believe at some point gains can be realized by going from 4" to 5" although like Idaho CTD says, probably not until you are past 500hp.



Then there are people like Dave Mitchell that seem to have plenty of exhaust volume (and smoke) to fill TWO 5" (or is it 6"?) stacks!!!!

(of course we know he's in a league of his own)



Vaughn