Cats or no Cats?

93Range302 · Mar 31, 2008

My buddie keeps trying to get me to take the cats off my truck... he swears it will get a better flow and give me more horse....i've posted a thread a while back and a couple people told me to just leave the cats, but i want to know why or why not to touch my cats (lol) !

also , flowmaster 40 series or something different?

Ranger44 · Mar 31, 2008

Leave the cats. You won't gain anything removing them. Yeah, flowmaster 40's are good.

mjonesjr · Mar 31, 2008

removing the cats off a 4.0 Ranger will only hurt the engine performance.....the engine needs a certain amout of back pressure to produce the proper amount of power/torque....

that is why they are still on the Ranger you bought....

93Range302 · Mar 31, 2008

gotcha thanks alot

Wicked_Sludge · Apr 1, 2008

im sorry, but you will not LOOSE power by removing the cats. backpressure on a 4-stroke motor is a BAD thing and you want as little of it as possible.

that said, the stock cat converters are not in the least bit constrictive and you wont gain anything (horsepower or mileage) by removing them.

the reason to leave the cats on is the $10,000 fine the feds can issue you if they find out you've removed them.

mjonesjr · Apr 1, 2008

Wicked_Sludge said:
im sorry, but you will not LOOSE power by removing the cats. backpressure on a 4-stroke motor is a BAD thing and you want as little of it as possible.

that said, the stock cat converters are not in the least bit constrictive and you wont gain anything (horsepower or mileage) by removing them.

the reason to leave the cats on is the $10,000 fine the feds can issue you if they find out you've removed them.

actualy you will lose power.....that is why engine builders put them on their vehicles.....there are plenty of 4.0 builders who have them on their trucks...

and the government can only give the fine to a shop, not an individual...

85_Ranger4x4 · Apr 1, 2008

mjones said:
actualy you will lose power.....that is why engine builders put them on their vehicles.....there are plenty of 4.0 builders who have them on their trucks...

and the government can only give the fine to a shop, not an individual...

Losing the proper velocity is what kills power, if backpressure was a good thing the restrictive stock system would be the best thing to run. There is probably something to the stock cats helping with the velocity, but the whole backpressure thing is a strangely common myth.

The dealership my brother works at gets inspected to make sure they have paperwork to back up any used cats sitting around. $25k fine for the shop and $5k for the tech that does it if someone there takes them off without replacing them.

shadetree · Apr 1, 2008

mjones said:
actualy you will lose power.....that is why engine builders put them on their vehicles.....there are plenty of 4.0 builders who have them on their trucks...

and the government can only give the fine to a shop, not an individual...

Please explain your theory of how backpressure adds power to a system. I need to learn something today. shady

mhughes165 · Apr 1, 2008

there is no gain, and there is no loss fro removing the cats from the performance aspect, well not noteable enough to be felt.

the only ticket that you can be issued is midifiying emissions equipment, in which case they remove your inspection sticker and its a 300 fine in NJ,

mjonesjr · Apr 1, 2008

there is no inspection in Indiana......

not to mention you will get a Check Engine light because the last O2 sensor will be reading improperly....

85_Ranger4x4 · Apr 1, 2008

mjones said:
not to mention you will get a Check Engine light because the last O2 sensor will be reading improperly....

You can get dummy sensors that just tell the computer what it wants to hear so it doesn't throw any codes.

I don't recomend removing them though, as others have said they don't do much to hurt performance anyway.

shadetree · Apr 1, 2008

mjones said:
there is no inspection in Indiana......

not to mention you will get a Check Engine light because the last O2 sensor will be reading improperly....

Uhh, you must have missed my question, so I'll repeat. How does backpressure add power to an engine??????? shady

mjonesjr · Apr 1, 2008

all engines require some backpressure.....

shadetree · Apr 1, 2008

mjones said:
all engines require some backpressure.....

Please give me an explanation why. Just saying it doesn't mean anything. Maybe you don't really know. shady

mhughes165 · Apr 1, 2008

mjones said:
all engines require some backpressure.....

all engines require exhaust escape velocity, 4 stroke engines perform at the optimum with no restrictions and no "back pressure"

however u may think what im sayin means just run shorty and thats the best performance.....its not, becuase it wont have the velocity it needs and u will overhead the header and start burn up valves

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