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Exhaust cut-outs

97Sierra4x4

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97Sierra4x4 Enthusiast

97Sierra4x4

Posted
Posted

I'd like to run a straight thru exhaust on my 5.7L 97 GMC. I already have a dual-cat back flowmaster exhaust on. I wanna cut my pipes after my cat's and put exhuast cut outs in before my mufflers. Then i would continue on into the flowmasters.

 

When I run with the cut-outs open will the decreased back pressure negatively affect my engine?

 

Thanks,

Jim

97Sierra4x4 Enthusiast

97Sierra4x4

Posted
  • Author
Posted

okay yeah thanks for the reply, but im not worried about decreasing a lil torque and dont really care about my MPG. I more wondering about if the decreased backpressure will have any long-term negative affects on my engine?

  • 2 weeks later...
95Sierra2500 Senior Enthusiast

95Sierra2500

Posted
Posted

It will NOT hurt your engine, it's a very common mod for street-driven drag cars. Just remember that, as stated above, they're really only useful for WOT runs and drag racing. The loss in torque isn't that big. If you run with them open in city driving then it'll hurt your fuel economy, not to mention probably rack you up quite a few tickets for noise violations. If you run with them open on the expressway it will actually HELP your mpg a bit (I've removed the cat and resonator on my car and gained almost 4 mpg just from the reduced restriction in the exhaust...it's not a cutout but it's the same principle), but again you may have issues with noise violations.

TheClassic Enthusiast

TheClassic

Posted
Posted
It will NOT hurt your engine, it's a very common mod for street-driven drag cars. Just remember that, as stated above, they're really only useful for WOT runs and drag racing. The loss in torque isn't that big. If you run with them open in city driving then it'll hurt your fuel economy, not to mention probably rack you up quite a few tickets for noise violations. If you run with them open on the expressway it will actually HELP your mpg a bit (I've removed the cat and resonator on my car and gained almost 4 mpg just from the reduced restriction in the exhaust...it's not a cutout but it's the same principle), but again you may have issues with noise violations.

 

Just get electric cutouts. That way you can just close them with the flip of a switch if any cops come sniffing around.

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