4" Down Pipe Worth It?
 

I got some stacks a little while back and just now got the piping ordered. Would it be beneficial to replace the OEM down with a 4"? I have it straight piped now and plan to leave it straight piped unless the stacks are too ungodly loud. Would I see a noticeable drop in EGT's? Thanks for the input...

Brian

You probably won't see much of a drop in EGTs. I only saw a 50* reduction going to a 5" system, before the stacks. No power mods at the time. The 5" had a 4" DP, but the inlet was still 3 or so, off the turbo. Not sure what it would be on your truck.

My EGTs dropped about 100 degrees when I put the Banks downpipe on. The drawback is that now, if I'm towing and I push the truck real hard, I get a terrible drone until I let up on the throttle.

Engines that are 305/555 (4inch turbine out necks down to 3.5" downpipe inlet)will see a benefit only if you replace the cast iron turbo elbow with one from a 325/610 enigne (4 inch both sides). Then get a 4 inch downpipe.

So the cast elbow off the 610's will mate up to the 555's with no mods? Other than a new DP that is...

That's correct, a good update for a 305 engine.

Especially if you've paid to update your exhaust to a 4+ inch system and are still running a 3.5 inch outlet on the turbo.

turbo elbow
 

If I was to change that elbow would I need to order an exhaust for an 04.5 or newer for my 04?

Kris

I thought they cam with a 4" DP on the new trucks?:confused:

"new trucks" being the 610's, yes, they have a complete 4 inch system (to try and make up for the increased system backpressure caused by the cat).

555's, have no cat, but the turbo elbow necks down to 3.5".

You would need the downpipe from a 2004.5 and later exhaust system (pipe that goes between the cat and turbo elbow) and the corresponding turbo elbow (4 inch outlet).

So the 600's and the 610's have 4"

Re: turbo elbow
 

Yes, you can order the factory downpipe for an 05 - And as for cast elbow off an 05... You have to grind off the little locator pins, But it is still a perfect fit...

One things for sure... It can't HURT your egt!

PS - don't forget to get the bigger clamp for the 05... The old one is too small to reuse

So Am I reading this right? All I have to do is buy a downpipe from an 05, the elbow AND the clamp and I'm set to run full 4" ??
Anybody know the cost of doing this ?

Or here is my other option. (email I recieved earlier today. I asked about 4" piping for stacks)

"I CAN GET YOU A DOWNPIPE FOR $205 AND IT WILL ELIMINATE THE 3.5" CAST-IRON ELBOW SO IT WILL FLOW A TRUE 4" BUT THAT IS ALL I CAN GET I DONT HAVE ANYTHING ELSE "


So which would be better ? Or is it just a price decision ?
Also, where CAN I find 4" elbows and such to run stacks ? Thanks, Dan

Just in case some fellow 03's want to know....
I did some research today and I'm going to the dealer in the morning to order some parts.

4" elbow part #5161570AA
4" Downpipe part #52121285AA
Clamp part #52121600AA

Judging from the list pricing I am assuming these parts should be around $150.
I'll find out for sure tomorrow.

Checkmate,
I am very interested in how this works out - plz keep us updated. How much is the Banks downpipe?

The Banks downpipe costs around $180-$200 and replaces all those parts and you can reuse your stock clamp. I got mine from DPP which is Carnut57 here..