exhaust cutout, is it a good idea?

[foxbrand]

from what I have heard, using an exhaust cutout (or dump) can decrease the power of a naturally asperated engine, what I'd like to know is it a good idea to install one of these before my converter? Would this increase the power more even if I also don't have a secondary pipe that runs off the cutout port? Is the assumsion that the a cutout can decrease the power of an N/A engine correct to begin with?

thanks

[duh2150]

not a good idea, whats the harshest cycle on the engine? you would think its the power stoke, but its the exhaust when the exhaust hits TDC it gets yanked back down by the cap on the rod and the only 2 bolts holding it on, a little bit of back pressure is good to "bounce back", sometimes its good to remove some pressure but not always all of it, too big of a pipe say 3" on a NA would lack engine exhaust pulse efficiency? and draw the pulses of the exhaust out the back kind of like a chimney when it warms up

[foxbrand]

I should have included this with my initial posting, I have a 6g72

what about if I make a straight pipe (say 2 feet long by 3 inches in diameter, or starts at 3 inches in diameter then is reduced to 2 1/2 inches) that I can bolt to the cut out port, would that be detrimental to performance?

[duh2150]

I know a guy has a 3" full exhaust on his stratus 6g72, sounds like crap, spend your money on a real exhaust, its your car you can do what you want that's all I can tell you

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[SPD_FRK]

On a daily driven, non-modified engine the exhaust dump is pointless and will yield no gains. Generally when you do an exhaust dump, it is because it is a turbo charged engine and the exhaust is dumping right off the turbine housing. In an naturally aspirated engine, the only purpose for an exhaust dump would be on a heavily modified race engine where your average RPM operation is no less than 3000RPMs...obviously as you would be racing. You would also be using aftermarket cams to accomodate the racing application, something with a high lift, duration, and very rough idle.

not a good idea, whats the harshest cycle on the engine? you would think its the power stoke, but its the exhaust when the exhaust hits TDC it gets yanked back down by the cap on the rod and the only 2 bolts holding it on, a little bit of back pressure is good to "bounce back", sometimes its good to remove some pressure but not always all of it, too big of a pipe say 3" on a NA would lack engine exhaust pulse efficiency? and draw the pulses of the exhaust out the back kind of like a chimney when it warms up

If you are remotely worried about the connecting rod bolts than you need to go back and re-build the engine, or use ARP rod bolts. Exhaust back pressure isn't something you should be mixing with simple internal engine components such as the rod bolts,

3" exhaust is typically used on the V6 turbo setups, though you can lose torque from using that large of a diameter even on a turbo setup. A 3" exhaust on an naturally aspirated V6 is going to drop torque, but it will aid in high RPM range power, minimal results on a stock engine, but noticeabe on a built engine (ie high compression, cams, etc...).


Depending on how the exhaust is setup, it will sound like crap, or it will sound excellent...you just have to know what you are doing, and matching the right exhaust components together.

There is truly no "real exhaust" out there, it's all metal tubing, stainless or not, "X" brand or "Y" brand, 2"-3", resonated or not, flow through muffler, and so on...if you don't know what you are doing, then buy an off the shelf kit.

[foxbrand]

my exhaust is pretty well made, I have gotten complements from police (long story) before, I needa post the video of me running straightpipe (pipe that is reasonator delete removed) the last time I went drag racing so you guys know what I'm talking about

so, what? too little backpressure will not be bad for the connecting rods/reduce backpressure? I figured that the reverse is true with really high reving engines used for racing as well as for motorcycles that scream into the stratosphere. I do know that some backpressure in an N/A is needed specifically in the head/header area for gas velocity, cyclinder scavangering, ect, but this has little else to do wih having a pipe that bypasses the cat a good bit downstream

I'm running stock y pipe and exhaust manifolds, the main reason for having the cutout before the cat (and after the first o2 sensor) to remove the largest source of backpressure in the exhaust system, nothing more, and exactly, I won't be using this outside of racing (and then have a short side exhaust that bolts to the cutout port, probably won't be bigger than 'stock'), which begs the question, would this sort of set up actually do anything besides sound really cool?

anyway, thanks for the info

[SPD_FRK]

You have a stock engine...why are you wasting money you could save for that "some day" engine swap you keep talking about?

You even stated you have the stock manifold still, as we know those are the most restrictive part of the exhaust system, not your cat.

This won't help your drag racing, in fact it will kill your low end where you need it most as the stock 3.0L is poor on the top end.

If you want to do this for that "look at me look at me" factor, then by all means go for it...just don't expect any pat on the back from doing so as it completely contradicts performance in every aspect being done to a stock naturally aspirated engine.

[foxbrand]

well, I just needed some help deciding on this, that would be it, actually running straight pipe might explain my lacking performance last time I went racing, in all honesty from the info you just gave, I won't be doing this, the new motor is taking priotity with my finances after books for school

thanks for the help

[duh2150]

If you are remotely worried about the connecting rod bolts than you need to go back and re-build the engine, or use ARP rod bolts. Exhaust back pressure isn't something you should be mixing with simple internal engine components such as the rod bolts,

I'm saying the exhaust pressure helps cushion the blow of the exhaust stroke, ive got eagle rods and arp bolts im not worried, but for a stock engine under high RPM's with low or no back pressure can effect how some of the engine works, even on some EGR systems that need back pressure for them to work