Gains from catback?

[Amputechture]

Hey guys,


I know this is a beaten subject but I haven't been able to find much in terms of hard data. Does anyone have any before and after dynos of just a catback on a turbo setup(butt dynos are welcomed too, fuck it)? I am running 10 PSI on a Precision 4854, 2.5 OP, 2.5 HFC with a stock catback on 93 octane. Long story short I am trying to squeeze a tad bit more out of my current setup without switching to flexfuel or methanol, and yes I am aware that the cost to gain ratio of flexfuel is much greater. I know CBEs do fuck-all in N/A fashion but in my case I stand to gain from one. Would it behoove me more to get the cat out of the front pipe or is there a noticeable gain to be made via a catback? Or at my power level would you just keep your cash and spend elsewhere?

[Toyarzee]

In general, any FI system will benefit from less back pressure; especially in comparison to OEM exhaust, considering in-line cats, small diameter and not always evenly flowing piping, and non-straight-through mufflers. As for this platform and the turbo setup you're running, end results may vary some, but I'd venture to guess you'll see some small but noticeable gains if the tune is adjusted accordingly

[guybo]

I can't find the article but an Australian tuning shop did a full turbo 86 build for professional rallying. It was a pretty extensive build blog and 86 breakdown, I wish I could find the article. They are using the stock catback and they did a big build. If you go bigger you will change how the power hits, but you won't gain anything.

The stock catback is more than enough for your build according to thier build. You can do it for looks or for sound but the stock catback is more than enough to make all the power you need.

[Toyarzee]

Not true at all with the no gains claim. Any chambered muffler reduces FI performance, regardless of what other successful builds utilize. Same goes for catalytic converters. "Good enough" and "noticeable gain" are highly subjective and vague references for any specific comparison... but I'm certain it's more than just how it hits and I'd be willing to wager on it.

[Amputechture]

Guybo- Did the powerband shift to the left and lose top-end or did it shift to the right and lose mid-range? I am always one that is inclined to take the side of empirical data over theories but theoretically any decrease in back pressure should mean less pressure opposing the turbine wheel and slowing it from spinning. The question is how much of that opposing pressure can be decreased by opening up the exhaust that far downstream? If I were to gain 5-7 lbs. of torque throughout a decent chunk of the RPM band(spanning across 3,000 RPMs) I would consider it a worthy investment (speaking for myself). Perhaps I'm pipe dreaming by thinking this...which is why I'm looking to those w/ experience.