So I hate loud exhausts, period. But I have a built motor and good size turbo running pretty high power/boost. I can tolerate having a 2.5" downpipe into a 60mm exhaust for everyday driving.

If I have a 2.5" cut-out on the downpipe (right after the oil pan), will I make as much, or more, power than if I had a full 3" exhaust?

 

maybe not as good as 3" exhaust but a lot better than a 2.5" exhaust

 

Depends on how much power your making. I think after 300whp 3" is optimal.

 

Yeah but I'm talking a 2.5" open cut-out about 12-18" downstream from the turbine outlet. Is that going to limit my power producing capability more than a full 3" exhaust?

 

i don't think so but i'm not an expert, maybe someone with more knowledge in this question may answer.

 

putting that cut out that close to the turbine will affect your power and could actually run worse because you would be losing alot of back pressure but if you moved it back a lil yes it would help your power than having to do a 3" full exhaust

 

Hum, less to no pressure is a good thing for a turbo. So therefore yes, you will gain more from an e-cutout then putting a whole catback on.

 

to the OP.... ill be running a 3 inch downpipe with a 2.5 inch catback, but ill have a 3 inch cut out coming out right before where a stock catback would bolt onto...

id suggest running something similar.

 

^^^^ That's exactly how I plan to do mine as well. You want the e-cutout after the o2 sensor so your motor runs fine and before a cat (if you put one on) to further divert gases out before a restriction.

 

Corkey Bell "The best exhaust for a turbo is no exhaust"

 

Make sure it at least passes the oil pan, you don't want hot exhaust gases recirculating back into the turbo...

As far as gaining power, you'll gain some spool and power. The problem is 3" is overkill for most Hondas, so the 2.5" isn't restricting too much. If you had a stock axle-back you'd want a cutout - mine will hit 18psi faster with it open than it hits 10psi with it closed.

When you consider that one of the first upgrades factory turbo guys do to their cars is exhaust work, it makes you wonder...

 

exactly.

all the backpressure is between the motor and the turbine.

just get a 3" downpipe and 3" cutout. i used to run that with a stock exhaust. it was entirely night and day with the cutout open, also got me some more rpms in spool time

 

I ran a very free flowing 3" on my dsm, Noticed some spool time increase with dropping the exhaust, so I decided to install a cutout, I noticed less of a spool increase then with no exhaust, but more than with the exhaust connected.

I did have to adjust my boost controller accordingly.

It reduces backpressure, which is what you want (no backpressure). It will work very well for what you wish to do.

However, my QTP cutout was crap and the plate bent, it leaked etc.. but my friend has the same one and had no issues with his, needless to say the car now has a 4" exhaust with no cutout.