[repalmer]

Hello all. What's the pros and cons of going with a 4in downpipe? I have a 5in system I'm going to install and I can either use the stock downpipe or buy a 4incher.

I guess mainly what I want to know is, how much low end will I loose? That's about the only con I can think of

 

[HeavyAssault]

You may need to port the firewall to prevent rubbing due to the size. 3.5" MBRP worked great for me. Fits with no issues, needed to be aligned a few times to prevent vibrations.

 

[SOOTIE]

Loose low end????? This is a turbo diesel, not a naturally aspirated gasser. A larger downpipe will gain you nothing in performance. Stick with what fits well. The tiny drop in post turbo egts would hardly be noticible either. Now if you were over 800hp, the egt drop might be worth it...

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[kcoyner]

I just mashed the pipe a tiny bit to go by the firewall. You loose no volume that way.

k

 

[repalmer]

I'm not to worried about fitting it. I can take care of that. Just didn't know if the gains and losses were worth the money. I think I'll use what's there for now and see how I like the 5in. I did pick up a muffler for it if it's too loud.

I know, I know, if it's too loud, you're too old. But I like to be able to have a conversation. Although the 37 Toyos are loud already.

The only reason I have the 5in is I picked it up several years ago from a guy stationed in San Diego that some how ordered 2 sets and couldn't return the extra. Got a sweet deal on it that I couldn't pass up. I was going to put it on my 7.3 but never got around to it, then sold it

 

[Heavy_GD]

none, the more flow the faster the egts drop.

 

[junior125]

pretty sure most kits these days come with a 4in downpipe

 

[voodooridr]

Remember too, we had a 6.0 fail the visual for smog because of an aftermarket down pipe.
Stoopid commiefornia

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[repalmer]

pretty sure most kits these days come with a 4in downpipe

Mine didn't come with a downpipe, I think it was supposed to be a cat back setup.

Remember too, we had a 6.0 fail the visual for smog because of an aftermarket down pipe.
Stoopid commiefornia

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My permanent address is in north central Washington so I'm ok with that

 

[Jason Thomas Cook]

i think you do want you want, buy what you can. The install is a little tight.

 

[jmeaby]

https://youtu.be/HYyNbz9zNdw
This was my brother and I installing his Exhaust. 4 inch down pipe is nice. We even compare the factory down pipe to the 4 inch. I must say the factory down pipe is very restrictive. It is smaller in diameter than the rest of the exhaust. I was shocked to see it. It is a little bit of a pain getting the down pipe in but not bad. I would get the 4 inch down pipe.

 

[Boudah]

I have a stock Downpipe and cat to a 5” straight pipe out. It’s “ quiet “ u til I’m towing.

I’m about to get rid of the cat too so post up a sound clip , thanks


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[SOOTIE]

Just remember..... perceived restriction based on an uneducated naked eye, with no data to back it up, is no justification for change.

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[kcoyner]

Just remember..... perceived restriction based on an uneducated naked eye, with no data to back it up, is no justification for change.

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I will concede that point. Is there an educated eye or any data pro or con that you could share?

Thanks!

k

 

[mhatlen]

I have a 4” Diamond Eye SS D/P and I wrapped at least 1/4”-3/8” of DEI Titanium wrap on mine and it’s not touching the firewall. Temps are better then stock D/P for sure and extremely quiet in cab after the wrap.
I think it spools better with 3” OEM but that’s about it from my experience. I like mine and don’t buy the it won’t fit business. Both my trucks had 4” D/P