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4" exhaust gives less power?

9K views 24 replies 16 participants last post by  lenzhotrod 
#1 ·
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".
 
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#2 ·
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.
 
#3 ·
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.
 
#6 ·
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.
 
#7 ·
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.
 
#9 ·
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 LOL, but I honestly wouldnt think it would matter on diesels.
 
#8 ·
I thought backpressure only mattered before the turbo, not after on these trucks. I could be wrong though.
 
#12 ·
I don't know what else it could be then other than back pressure. I did the egr delete, and could really notice the extra power at part throttle, then I put on the 4" exhaust and - I'm not saying it is a slug now, I just do notice some missing low-end torque. Maybe it is all in my head since it sounds so mean now and I expect more, but when hearing someone like Vivian saying you do loose power when you add the big exhaust, then I believe it. Obviously the stock exhaust does become restrictive if you put a tune on it, so like I said, I don't think this will be an issue when I get a tune, just a little puzzling.
 
#13 ·
egr delete isnt really a power adder either just keeps hot exhaust from entering the intake manifold. i mean maybe there is a slight increase but nothing major. its prob one of those things where you just imagine it. i use to do that alot after adding something on my truck. now since ive seen and build the big hp trucks its not that noticable to me anymore
 
#16 ·
I recall this being more an issue that the powerband is now higher in the RPMs. So the perceived loss of power is where it is most noticeable..low in the RPMs. Now add in and SCT this issue will go away.
 
#20 ·
Ok, we were just out and did so I had an opportunity to see what the power was like on the higher end. We did a pull from 60 and it felt like it did before I fixed the y pipe. I know there is nothing leaking now. So I am seeing a loss at every level. Maybe I have a different problem now, but it is strange that the power was lost right after I switched to the 4" exhaust.
 
#22 ·
i to didnt notice any difference with the exhuast, especially with a vgt turbo your backpressure is created pre turbo, i cant see exhaust losing power, maybe it just sounds like your getting on it more becuase its louder lol. its hard to feel seat of the pants dyno, i can feel more power after doing anything such as a oil change but i no its just in my head i dont actually believe my truck has more power lol.
 
#23 ·
i just put mine on a few days ago...sounds dope!
 
#24 ·
I put a 4" straight exhaust system in my 2007, no cat or muffler. I don't really know if I have more or less power on the wheels (I would have to check in a dyno), but driving in the city I improved the mileage up to 17 mpg, obviously driving like an "old lady" due to the traffic. I don't have tuner yet, I am saving for the BPD oil cooler and the tuner... are coming next year! But so far, no issues with the 4" straight pipe.
 
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