does taking cats off give you less power??
#1
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does taking cats off give you less power??
i have a 92 sc400.the previous owner has hollowed out the cats and almost straight piped it.only the 2 silencers remain.does this process affect the power of the car and my gas mileage?
any help will be appreciated
any help will be appreciated
#2
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Stock to stock, it won't be a huge difference, BUT you stand to lose some back pressure, which if you're really in tuned with your car will make it feel slightly sluggish from a dead stop. On the plus side, you MAY experience a tiny bit of top end improvement. Doubt it though. Lol.
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Back pressure is a myth when it comes to modern cars... What matters is pressure vs. flow of the exhaust stream. You want a system that gets the gas out of the system as soon as possible, without causing high pressure. For example, a 1" pipe will have a very high flow rate, but also a very high pressure, while a 4" pipe on a stock motor is too large, allowing the gas to cool and contract in the system which is no good for flow. You want to find the ideal balance of the two, which for a stock 1uz motor is dual 2.25-2.5" pipe from the headers, through an X all the way to the rear. Smaller and you will lose top end power due to pressure, larger and you will lose bottom end due to low flow in the system, making the engine work harder to push all the exhaust gasses out.
A hollowed out cat can reduce power, because the sudden increase in pipe diameter and then the sudden restriction back to the tubing causes turbulence. Instead, have a straight pipe welded in place of the cat. Alternatively, if you want the exhaust to pass a visual check for cats, remove the cat and weld in a pipe inside it, then put it back on the car. Looks stock, but you gain a *tiny* bit of power removing the cats.
A hollowed out cat can reduce power, because the sudden increase in pipe diameter and then the sudden restriction back to the tubing causes turbulence. Instead, have a straight pipe welded in place of the cat. Alternatively, if you want the exhaust to pass a visual check for cats, remove the cat and weld in a pipe inside it, then put it back on the car. Looks stock, but you gain a *tiny* bit of power removing the cats.
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#8
I dont car about the whole backpressure vs not debate,.
heres what i know, i have a 1995 sc400.
I removed the resonators and put in straight pipe = no power gain just louder
i removed the 2nd cats = still no real power gain but louder
installed IMF headers, 2 1/2" pipe with x and magnaflow mufflers, = SLOW CAR
sent the computer to jet chips, = car idles lower, car has no torque but all kinds of top end/ vs my buddys stock sc400 i gut him on the highway but not in the 1/8 mile he takes it
Took walker 2 1/2" x 11" cats and put them in after the headers. Its a car again! sooo moral of the story is. that particular engine/ecu, requires a certain amount of backpressure to operate with acceptable torque for what i feel is needed for everyday driving,
heres what i know, i have a 1995 sc400.
I removed the resonators and put in straight pipe = no power gain just louder
i removed the 2nd cats = still no real power gain but louder
installed IMF headers, 2 1/2" pipe with x and magnaflow mufflers, = SLOW CAR
sent the computer to jet chips, = car idles lower, car has no torque but all kinds of top end/ vs my buddys stock sc400 i gut him on the highway but not in the 1/8 mile he takes it
Took walker 2 1/2" x 11" cats and put them in after the headers. Its a car again! sooo moral of the story is. that particular engine/ecu, requires a certain amount of backpressure to operate with acceptable torque for what i feel is needed for everyday driving,
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plugs rotors and caps have been changed.is there a way to check if the o2 sensors are bad?i think the previous owner has taken off the check engine light coz he took off the cats.im thinking this is the case.
#12
Punched out cats won't reduce gas mileage. We did the same thing to my cousins SC300 and his gas mileage never changed. On the other hand, bad o2 sensors could. I've never seen this happen but considering that they take part in regulating the a/f mixture, its definitely a possibility. As for checking them, I would just go ahead and replace them anyways. They're bound to fail eventually anyways.
#14
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I have yet to see dyno proof of "backpressure" ever increasing power at any point of any motor's powerband.
Subjug4tor NAILED it. Velocity is the key word and cats kill velocity regardless how modern or high flowing they are. On older cars from the dawn of emissions era, cats are an absolute cockblock for making power.
Smaller diameter piping can shift powerbands but just adding cats has never been a solution to suddenly making power.