Downpipe taper performance?

I've searched around to see how much the 3" to 2.5" taper affects performance but I only found one case of performance loss. How much of a performance loss would this have around the 300-300awhp range?

 

While on the subject of downpipes, is there any manufacturer besides cobb that has the extra O2 bung for wideband? Also, curious about the general cost of getting an extra O2 bung welded on.

At 275-300AWHP, I can't imagine it would be much. I think it would be like using a stg2 reflash with a DP and a stock CBE then switching to an aftermarket CBE. Once decent size turbos are tossed in, then it becomes a bigger bottleneck. Hopefully someone will chime in with proof or better advice because I'm curious myself. And I think $50 plus the bung would be ballpark. Drill the hole, clean it up and TIG it in place and done.

I have used tapered shorty DP on both of my setup. I had Crucial dp on my stock turbo setup w/ FMIC. I hit 277whp and 18.5psi at 2800 rpms. Now I have a "Flow" shorty with my 20g w/ EWG and supporting mods. I hit 340whp and hit 20 psi @3400 rpms. It also hold 20 psi to 7000rpms on 91 octane Cali pump gas. Then on e85 I make over 370whp all with a tapered shorty DP. The Flow actually has a lip you can grind down. I tried it for about 5 mins then, said "F" it and put it on. I don't think that the tapper causes any power loss you will notice. I think people put too much on how bad back pressure is. I made those numbers also running a Hi flow catt and 3 mufflers(1 borla XR-1 and 2 magnaflows). My car is very quiet and my turbo spools louder the my exhaust.

 

A good tune will make more power then you would ever loss from a tapered pipe. Make sure you find a good tuner. Let me know if you have any questions.

good post itsme

It may help a couple of whp, but not really worth the headache IMO.

 

Don't forget, the farther from the turbo you are, the cooler the gases are, and the less space the take up.