i hear they robb performance
i hear they give performance

anyone wanna give me the straight and narrow on this?
and specifically for my size of engine

1.6L

They improve performance. But, I suggest you get headers and hi-flow cats for better flow.

proven?
not to hate on your intelligence
but iv heard so many strong opinions one way and the other

so i was wondering if anyone has it first hand

glock says it does squat... cept for make your car loud
but i was reading a golf improves the quarter mile time by 3 lengths

i will be deffinately be doing a write up on this

I have heard this done before, but havent done it myself since I don't have jack stands. once you get your foreward exhaust how you want it... like headers / cats / etc. put your car up on stands and start the engine. draw a line of chalk down your exhaust from front to rear. Now, supposedly, it will burn off up to a point where obviously the gasses are beginning to cool off substancially. It is at this point where you would want to do a cut out.

Now, I don't know that this will work. Honestly cutouts just seem like something else to interrupt the flow of the exhaust when closed off. If you are wanting street / strip options I would recomend good hangars and a flange that you can just unbolt and un-hang the whole rear section and then transport your car to the track then re-attach the exhaust once its back home. Sure its not as simple but theres no random Y turbulence generator hanging out in your system.

FURTHERMORE, by doing this you can just take your now modular exhaust with you and to a pass without your rear exhaust, and a pass with to determine any REAL gains.

i like being able to do it automatically

and i dont really care cause hte exhaust will be stock so the performance will only come when the cutouts open
why do you wanna do the cutouts when the exhaust cools?

I will be perfectly honest, I have no idea. Something about thermodynamics and the density of the air in reference to the temperature of the air and the vaccum generated by pressure variance. I basically threw it out there in the hopes someone with more technical experience would jump on it and either validate it or provide a better solution. Again, its just something I have heard of and have not experimented with myself. In all honesty it may be a trick that only works on higher output engines.

This post has been edited by KoreanDeathMachine: May 1 2009, 08:16 PM

tr00f

thanks for letting me know
ill look into it

Cutouts should definitely help. Every bend, curve and obstacle(i.e. catalytic converters and mufflers) in your exhaust system causes backpressure which requires energy to push out of the tailpipe. This energy comes directly from your engine and instead of being applied to your wheels its used to push out exhaust gas.

Where are you going to place these cutouts? Placing cutouts before the catalytic converter is quite illegal from an environmental standpoint, but then again placing them after the catalytic converter removes the mufflers which is illegal from a noise standpoint, so we'll assume legality is not an issue here. Placing cutouts before the catalytic converter will also cause computer fault codes. However certain companies do sell circuits to fool your car's computer. One such example is o2simulator.com, I have never used anything from this company so I in can in no way vouch for them. Will this cause your air/fuel ratio to be off? I honestly don't know as I've never done this on a computer controlled vehicle.

The gains you will see from cutouts will depend on how restrictive your exhaust is currently. Obviously a high flowing exhaust will see much less improvements than a choked off maze leading to an economy muffler. I'd think you'd see better gains from a good set of headers but I'm just guessing on that one.

My only experience with cutouts comes from my personal experience with them on my 67 Nova. I race it every weekend and with the cutouts open it will run 7.40's in the 1/8th mile. Through the muffles it runs 7.70's. Three tenths may not seem like much but believe me, its a huge difference.

I'd like to qualify my statements by stating the above numbers are for a 350 (5.7 liter) engine. For a 1.6 liter engine, the gains may very well go unnoticed.
Here is an interesting article on catalytic converters. http://www.importtuner.com/features/0610im...oval/index.html Assuming their tests are accurate, it looks like a no brainer on where to place your cutouts in relationship to the catalytic converter.

This post has been edited by ShofRacing: May 25 2009, 11:46 PM

I had cutouts on my srt-4 and it gave me 14 hp at the wheels. But turbo cars are different because they don't need backpressure from the exhaust. I also had a friend with an 07 civic si and his cutout gave him 9 hp over stock but i'm not sure what the difference in torque was.

Yes. A cutout will improve performance. Proven over and over again, just make sure you put it in a place that's not noticable so the cops don't mess with you.

Actually turbo cars do need backpressure to operate efficiently, but they don't need near as much as the stock exhaust gives them. I'm a V8 guy and a turbo car guy so I've a little experience in both worlds. Suffice it to say that all gain power from a cutout.