Downsizing an exhaust system

Probably a stupid question: My SVT Focus has a 2.5" Borla exhaust that is droning a bit too much for me. I changed the resonator a few months ago, but it did not make enough difference. My exhaust guy is having trouble finding a muffler that will match my needs, mostly he is finding comparable performance mufflers. I am considering just having him make me a custom 2" exhaust with a regular turbo muffler, nothing fancy.

I don't care about the 5hp I will lose, and the resonator change actually gave me a teensy bit more torque, so I am hoping there could be an upside. My concern is that a few hundred Ford engineers came up with a OEM size of a little over 2.25", would smaller be detrimental in any way? I really don't think this would cause any issues (fuel mapping/backpressure?), but I am not a mechanical engineer.

I would think that just changing to a "regular" muffler would kill the drone.

Why would you have him make you a custom 2" when you could have him make you a custom 2.25"?

A 2.5" walker dynomax won't fit? They are pretty quiet IIRC?

probably not enough room.

Bung a restrictor of about 1.75-1.87" in diameter in the tail. This is a thing I've been doing on a long time to cut drone on straight-through exhaust systems. It nuked all drone on a 210hp RX-7 with a 2.5" straight-through system without affecting power to any measurable degree (A-B-A testing at the dragstrip). By the time the exhaust gets to the end of the system, it has lost a lot of temperature and therefore volume (size) compared to near the engine, so the large diameter is not required back there to keep peak exhaust gas speeds in check.

Most likely, SVT has the 2.25" system on there for NVH reasons in the "expected noise" vein. For a 170hp 2-liter, I'd just chuck a 2" exhaust on it and be done with it, assuming that the mufflers are perforated core straight-through systems.

Thanks for the feedback. I think I am going to look for just a new custom system, I will ask if any dynomaxes will work for my system.

The option I ended up going with on my cobalt ss was the stock muffler. I had a long tube header, 3" down pipe, & full 3" exhaust mated up to the stock muffler. Didn't start out that way, just got sick of the drone. Looked subtle, sounded amazing, and really didn't notice any seat of the pants loss in power. Just an idea

I also second going with the stock muffler. Most are designed to be quiet, so I'm not sure if you will be able to get quieter than that. It is also the cheapest and simplest solution to your problem. I would think that SVT went with a 2.25 inch exhaust instead of a 2 inch to get to 170hp easier than using a different tune or making the intake manifold/cylinder head flow more air.

Considering how overpriced Borla stuff is, couldnt you just straight up trade someone for a stock exhaust system?

Vigo wrote: Considering how overpriced Borla stuff is, couldnt you just straight up trade someone for a stock exhaust system?

Yeah I probably could get some money back on that system, I did not buy the exhaust, it came with the car. But I have space issues with storing an extra system and doing a swap.

Too much drone, what? My RX-7 TII has a 3" single pipe all the way back to a Borla XR-1 race muffler. Street driven. Nice and quiet. Well, okay, it can be a little noisy.

Turbos make great mufflers. Put a turbo on there.

In reply to 1988RedT2: I forgot about that option, but it's not cheap.