3rd muffler delete = power loss or throw code?

[Jeff szudy]

Just got catback magnaflow installed, moderate sound, with nice deep mellow tone and not broken in yet.
Any ideas of 3rd muffler delete will throw code or lose any performance gains?

 

[mmh64]

No codes. This cat is not monitored. Performance may actually be better.

 

[SHOdded]

Should not throw codes or lose perf gains. Might not be good though to increase catback pipes to more than 2.5 inch diameter all the way through, unless you go with single exhaust.

 

[18ADSHO]

I just put a corsa exhaust from the cat back and it didn't throw any codes on my 2015

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[SilverSH0]

Should not throw codes or lose perf gains. Might not be good though to increase catback pipes to more than 2.5 inch diameter all the way through, unless you go with single exhaust.

What's the reasoning behind this notion?

I've talked to several turbo buddies and they all tell me to go 3" or larger turbo back. Coming from various performance NA cars I was always under the impression that if your exhaust is too large or to small you lose performance. NA cars rely on exhaust velocity to produce scavenging in the collector (there's more to it in terms of primary lengths but we'll keep it high level). If you go with an exhaust that's to large then you lose velocity and the scavenging effect. If you go to small you get scavenging but the back pressure is so high it ends up being detrimental. So you search for the happy medium for what you're driving.

But what my buddies explained in turbos is that same thought process doesn't hold true. Turbos are essentially are compressors and work off a turbine pressure ratio. So if you can reduce the turbo outlet pressure by a certain amount, that will get multiplied by the pressure ratio and that ends up being the back pressure reduction seen by the engine. So if you can decrease the back pressure from 10 psi to 5 psi on a turbo with a pressure ratio of 1.5 you will reduce the back pressure on the engine by 7.5 psi (5 psi reduction multiplied by 1.5 pressure ratio). So the bigger you can go with turbo back exhaust the better. But there becomes a point where you will cease to see any gains because the car isn't making enough power.

That's how it was explained to me so I'm wondering what's different and why you would recommend single exhaust if going 3" turbo back. I'm not trying to say you're wrong, I'm just trying to understand the workings.

 

[SHOdded]

Mostly because the 2.5's already flow plenty for these cars even at 400+ AWHP. Not sure on bpd's SHO (custom exhaust), but I think that is still a 2.5 dual (at 600+ AWHP at that)? Also don't want to reduce backpressure too much as that has been theorized to blow out seals in stock turbos. Should be less of an issue with rebuilt units. Also not sure if there is room in the tunnel for pipes > 2.5" true duals. Somebody has to measure that.

EDIT: Livernois provides different exhausts for different levels of peformance IIRC. Maybe they can shed some light on their offerings.

 

[18ADSHO]

Mostly because the 2.5's already flow plenty for these cars even at 400+ AWHP. Not sure on bpd's SHO (custom exhaust), but I think that is still a 2.5 dual (at 600+ AWHP at that)? Also don't want to reduce backpressure too much as that has been theorized to blow out seals in stock turbos. Should be less of an issue with rebuilt units. Also not sure if there is room in the tunnel for pipes > 2.5" true duals. Somebody has to measure that.

EDIT: Livernois provides different exhausts for different levels of peformance IIRC. Maybe they can shed some light on their offerings.

I have a 15 and I have the tune, corsa exhaust and just bought the down pipes and I've exhausted all bolt on upgrades. Do I still have to worry and blowing the stock turbos? I have roughly 3500 miles.

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[SHOdded]

All Livernois intake/exhaust path? It's designed to work with the stock turbos, so I would think the worry is minimal.

 

[18ADSHO]

Awesome, it's all from livernios...tu

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[18ADSHO]

Awesome, it's all from livernios...ty

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I have a 15 and I have the tune, corsa exhaust and just bought the down pipes and I've exhausted all bolt on upgrades. Do I still have to worry and blowing the stock turbos? I have roughly 3500 miles.

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[2013blacksho]

But if your think about it the exhaust is 2.5" back on each side that would mean that installed single exhaust would be 5" in theory I eould think that anything bigger than 2.5 would be overkill. The performance f150 exhausts are single pipe 4"

 

[SilverSH0]

But if your think about it the exhaust is 2.5" back on each side that would mean that installed single exhaust would be 5" in theory I eould think that anything bigger than 2.5 would be overkill. The performance f150 exhausts are single pipe 4"

By that same mentality the 4" performance F150 exhaust would break down into 2" dual exhaust and that would make our stock 2.25" exhaust overkill.

There is a difference between back pressure on a turbo car and a NA car. Turbos can be thought of as back pressure multipliers. If you can reduce it by some on the exhaust output side of the turbo, you're reducing it by multiples as seen by the engine.

 

[onespdfrk]

But if your think about it the exhaust is 2.5" back on each side that would mean that installed single exhaust would be 5" in theory I eould think that anything bigger than 2.5 would be overkill. The performance f150 exhausts are single pipe 4"

It has to do with cross-sectional area. A single 3-1/2'' diameter pipe flows approximately the same amount as 2 X 2-1/2'' diameter pipes (9.82 square inches). A 5'' diameter exhaust has a cross sectional area of 19.63 square inches, equal to the flow rate of four 2-1/2'' diameter pipes.

 

[gimpy]

It has to do with cross-sectional area. A single 3-1/2'' diameter pipe flows approximately the same amount as 2 X 2-1/2'' diameter pipes (9.82 square inches). A 5'' diameter exhaust has a cross sectional area of 19.63 square inches, equal to the flow rate of four 2-1/2'' diameter pipes.

OMG...

Math!