Anyone tried de-cating?

[Cerano]

As above?

 

I know its a very controversial issue but does anyone have any dyno charts? It appears to be very popular on the MBworld forum but many other people say

 

reduced backpressure = less low end tq

[Cerano]

Catalytic converters, which are responsible for igniting and burning unburned engine exhaust gases, became standard automotive equipment on all cars beginning with model year 1975. Although catalytic converters help to make engine exhaust gases cleaner, they are not without their minuses. What follows is a brief list of the potential benefits of removing automotive catalytic converters.

.Increased Horsepower

Cars that have their catalytic converters removed experience an increase in engine horsepower. Catalytic converters create a significant source of engine back-pressure due to the constrictive effects they have on exiting engine exhaust gases. Removal of catalytic converters from cars allows exhaust gases to exit their engines much faster and at higher levels.

Better Gas Mileage

Since catalytic converter removal allows for exhaust gases to exit a car's engine at increased speeds, engine back-pressure is reduced, which lessens engine strain. This reduction in engine back-pressure and engine strain enables an engine to work more easily, and thus reduces fuel consumption and increases gas mileage.

Lower Engine Operating Temperature

Since removing a catalytic converter lessens the burden on a car's engine by enabling engine exhaust to vacate the engine more easily, a net effect is a reduction in engine operating temperature. The more easily an engine functions and the less work it has to do results in less friction, less load and, ultimately, a lower operating temperature.

More Fuel Options

Cars equipped with catalytic converters run only on unleaded gasoline. Lead-based gasoline, which produces more power and better engine combustion, quickly destroys the inner catalyst materials of catalytic converters. A car with no catalytic converter will be able to run on a variety of lead-based and/or high-performance fuels that would not be possible with a catalytic converter.

Healthier Exhaust Sound

Catalytic converters operate like car mufflers, whose sole purpose is to muffle the sound of exiting engine exhaust gases. Although catalytic converters burn unburned exhaust gases exiting an engine, thus making tail pipe emissions cleaner, they also further muffle a car's exhaust sound and bestow a somewhat timid, tempered exhaust sound. Without a catalytic converter, a car's exhaust sound becomes a little louder, a little deeper and more distinctive.

 

http://www.ehow.com/facts_4899387_benefits...rters-cars.html

[Mini-itx]

I don't know if back pressure is beneficial or not but its definitely a restriction for Turbo engines. Hence no cat = best.

 

Btw, talking about car.... Its rather questionable on how useful it is...

 

Cause some cars oversea are still able to pass emission tests even w/o a cat.

[Sp33dst3r]

its illegal in Singapore. U hv been warned!

[Cerano]

I don't know if back pressure is beneficial or not but its definitely a restriction for Turbo engines. Hence no cat = best.

 

Btw, talking about car.... Its rather questionable on how useful it is...

 

Cause some cars oversea are still able to pass emission tests even w/o a cat.

 

all FI cars or just turbo?

[Mini-itx]

all FI cars or just turbo?

 

It has a larger effect on Turbo cars compared to supercharged ones. This is because Turbo relies on exhaust to spin the turbine, the faster the exhaust moves thru the turbine the better it is for power and efficiency. Thus you want as little restriction as possible for turbo. If no exhaust even better... But the noise....lol......

 

 

[Mini-itx]

I did some research on internet + add my own logic...

 

I would say back pressure is something that is not wanted (regardless of what people said) if you are after power.

 

extractor designs like 4-2-1 or 4-1 is meant to enhance exhaust scavenging and hence improve power. Back pressure will reduce this effect and hence reduce the amt of air/fuel going into your combustion chamber. This is particularly important for high performance NA vehicles because of valve overlapping at high RPM.

 

Lack of back pressure may cause certain vehicles to run lean and hence possibly damaged to valves, detonation etc........ But this happens only for very old cars. In new cars, A/F ratio is carefully monitored (some KS veh even have 2 O2 sensors!). Hence its quite impossible to run lean.

[Cerano]

I did some research on internet + add my own logic...

 

I would say back pressure is something that is not wanted (regardless of what people said) if you are after power.

 

extractor designs like 4-2-1 or 4-1 is meant to enhance exhaust scavenging and hence improve power. Back pressure will reduce this effect and hence reduce the amt of air/fuel going into your combustion chamber. This is particularly important for high performance NA vehicles because of valve overlapping at high RPM.

 

Lack of back pressure may cause certain vehicles to run lean and hence possibly damaged to valves, detonation etc........ But this happens only for very old cars. In new cars, A/F ratio is carefully monitored (some KS veh even have 2 O2 sensors!). Hence its quite impossible to run lean.

 

interesting. So conclusion is that decating works

 

and without cats you can run leaded aviation fuels on an rx8 rotary engine

[Mini-itx]

interesting. So conclusion is that decating works

 

and without cats you can run leaded aviation fuels on an rx8 rotary engine

 

Actually you can still run leaded petrol even with a cat. Its just that the lead will coat the cat and render it useless. It won't coke your engine or blow anything.

[Dscheng]

Anyone decat and pass annual inspection??

[Kiadaw]

its illegal in Singapore. U hv been warned!

 

Its illegal in almost all decent 1st world countries.

[Cerano]

Actually you can still run leaded petrol even with a cat. Its just that the lead will coat the cat and render it useless. It won't coke your engine or blow anything.

 

it will clog up your cat wad.

 

so you'll still fail inspection even with your cat so might as well not put

[Zangetsu77]

It has a larger effect on Turbo cars compared to supercharged ones. This is because Turbo relies on exhaust to spin the turbine, the faster the exhaust moves thru the turbine the better it is for power and efficiency. Thus you want as little restriction as possible for turbo. If no exhaust even better... But the noise....lol......

 

Yes agreed. Irrespective of engine/turbo/engine management/fuel management, a decat will allow the turbo to spool faster. Hence the low end response for a turbocharged car on decat has got to be better too.

[Ken4555]

As above?

 

I know its a very controversial issue but does anyone have any dyno charts? It appears to be very popular on the MBworld forum but many other people say

 

reduced backpressure = less low end tq

 

i have never driven with a cat before in any of my present and previous cars...

 

mods or no mods... having a cat is like choking your engine... high flow cat? bs... its still restrictive compared to no cat... modded cars power will go up and then level off as the exhaust cannot pass throught the cat fast enuf...

 

funny thing is that many mech especially old birds will tell you that 'some' back pressure is good for NA cars... but the dyno will tell this is not so... and the whole idea is still to get a good header, and also a good muffler so you wont go deaf....

 

 

[Ken4555]

Catalytic converters, which are responsible for igniting and burning unburned engine exhaust gases, became standard automotive equipment on all cars beginning with model year 1975. Although catalytic converters help to make engine exhaust gases cleaner, they are not without their minuses. What follows is a brief list of the potential benefits of removing automotive catalytic converters.

.Increased Horsepower

Cars that have their catalytic converters removed experience an increase in engine horsepower. Catalytic converters create a significant source of engine back-pressure due to the constrictive effects they have on exiting engine exhaust gases. Removal of catalytic converters from cars allows exhaust gases to exit their engines much faster and at higher levels.

Better Gas Mileage

Since catalytic converter removal allows for exhaust gases to exit a car's engine at increased speeds, engine back-pressure is reduced, which lessens engine strain. This reduction in engine back-pressure and engine strain enables an engine to work more easily, and thus reduces fuel consumption and increases gas mileage.

Lower Engine Operating Temperature

Since removing a catalytic converter lessens the burden on a car's engine by enabling engine exhaust to vacate the engine more easily, a net effect is a reduction in engine operating temperature. The more easily an engine functions and the less work it has to do results in less friction, less load and, ultimately, a lower operating temperature.

More Fuel Options

Cars equipped with catalytic converters run only on unleaded gasoline. Lead-based gasoline, which produces more power and better engine combustion, quickly destroys the inner catalyst materials of catalytic converters. A car with no catalytic converter will be able to run on a variety of lead-based and/or high-performance fuels that would not be possible with a catalytic converter.

Healthier Exhaust Sound

Catalytic converters operate like car mufflers, whose sole purpose is to muffle the sound of exiting engine exhaust gases. Although catalytic converters burn unburned exhaust gases exiting an engine, thus making tail pipe emissions cleaner, they also further muffle a car's exhaust sound and bestow a somewhat timid, tempered exhaust sound. Without a catalytic converter, a car's exhaust sound becomes a little louder, a little deeper and more distinctive.

 

http://www.ehow.com/facts_4899387_benefits...rters-cars.html

 

burning of unburn fuel in the cat is not intended... when this happens the honeycomb melts causing further restrictions...

 

the correct way for the cat to work is to use its special metals to cause a chemical reaction which purifies the gasses that pass through it...

 

i think for your Merc if you remove your cat, your engine check light will come on...

[Cerano]

burning of unburn fuel in the cat is not intended... when this happens the honeycomb melts causing further restrictions...

 

the correct way for the cat to work is to use its special metals to cause a chemical reaction which purifies the gasses that pass through it...

 

i think for your Merc if you remove your cat, your engine check light will come on...

 

kekeke.

 

ECL come on will go into limp home mode and no power.

 

do you think the piggyback ECU can compensate and trick the sensors?

[Yeobh]

Try running a engine without manifold and min exhaust pipe, you may not be able to idle and accelerate to you satisfaction. Once you place the manifold and min exhaust pipe , the restriction will develop back pressure. This pressure ( how much depends on each make and model of engines) is very necessary resistance to prevent engine over run ( resulting in crankshaft hitting the crankcase and piston slapping the cylinder walls at great forces.)

When dyn engines it's best to have a back pressure gauge install after the exhaust manifold

[Kwchan]

Hence no cat = best.

 

A CAT can cause few K and it is on every car for a reason - to reduce the green house gas emission

 

human are already guilty of creating green house gases, so STOP being irresponsible by increasing the emission just to gain some house power :angry: