4" exhaust gives less power?

[ditchmagnet]

I just put on a 4" exhaust. I drove it last night, but it was pouring rain, so I didn't get on it. My wife took it out today and came back asking if it should feel like it has less power now. I haven't gone out to test it yet, but some quick google results showed me a few threads of people seeing the same thing. I am wonder why this is though. It doesn't make sense to me. I saw something about increased turbo lag, but the speed of the turbo come from the incoming gas from the y-pipe, and I would think the easier the gasses could leave the turbo, the faster it should spool.

So can anyone give me an explanation?

EDIT:

I found some explanations that sound correct here:

New exhaust less power

The responses from High Binder are what I am talking about.

I am guessing that once I get a tune on the truck this "issue" wont matter anymore. Anyways, the truck still sounds amazing, and I am still happy I put on the 4".

[HankyD]

It's true, the power loss your experiencing is due to the the lower back pressure from the wider diameter exhaust system. Are you studded?

If you are studded and have an egr delete, you can get an SCT tuner which requires a larger exhaust set up which you have. It will more than replace the power loss which you are currently experiencing.

[ajfetterman]

Pretty certain diesels don't have back pressure issues which is the reason we can run big exhaust.

I have never heard of power loss after exhaust install.

[countryboyrob]

It's not due to the back pressure ...... Turbo creates that.

[ditchmagnet]

Vivian from Quick Tricks also says you will loose power.

Ford Powerstroke Diesel Forum - View Single Post - Well, I'm Looney now!

[ajfetterman]

I honestly know nothing of power loss with a bigger exhaust. Big air in and big air out.

If big exhaust causes a loss of power then using that logic we would all be running smaller pipes instead of larger ones.

And a 4" exhaust is about the most beneficial size you can use on these trucks. Only benefit of a 5" is a louder exhaust note and drone.

[Petro]

On my buddies 06 6.0L there was a noticeable loss of low end torque after installing his exhaust. Its a 6.0L thing. Tune it and move on.

[Johnny77Mutt]

I thought backpressure only mattered before the turbo, not after on these trucks. I could be wrong though.

[ajfetterman]

Originally Posted by Petro

On my buddies 06 6.0L there was a noticeable loss of low end torque after installing his exhaust. Its a 6.0L thing. Tune it and move on.

Perhaps this is why I dont know of this issue. Im over here with a 7.3 , but I honestly wouldnt think it would matter on diesels.

['94IDITurbo7.3]

i have read that there is a bit of low end lost when you go with a 4" down pipe rather than the 3.5" down pipe.