RX7General

I have noticed on a thread asking for peoples first mod that they removed the cat.... Why? Doesn't that give you worse gas milage? Don't you lose acceleration? I understand if you are boosting, but my RX7 13b is N/A. My first accomplishment... not really a mod was to remove the manuel fan and install an elctric fan for the radiator. I also removed the A/C belt from the pulley's. Is it in my positive to remove the power steering belt as well? If so, how much of a gain is it?
I appreciate and help, thankyou.

FelixIsGod29X

iTrader: (50)

Put your A/C belt back on, you really dont gain ****. Dont take off your power steering belt unless you want a shitty ghetto manual rack. As for the CAT, if you have to pass emissions then dont remove it. You will gain power Like a few hp? but your car will be louder.

RX7General

So, the back pressure a cat gives will not be the same as a normal engine wich needs just the right amount to have the correct power available? Like my mustang 4.6 V8... I took the cats off and the mufflers and ran it straight piped and it was like a turtle slow untill I put either the cats or the right muffler on it for back pressure... The 13B engine will have more or less power with or without the back pressure? Pretty much I am looking for the best exhaust design the 13b can get for the maximum N/A power. I am all ears, or eyes online waiting for any more input.

cmanns

you need a silencer with a back pressure pipe

Your engine is 6port s4, so it opens the 5/6ports w/the exhaust pressure,

with out these opening and closing properly the engine will run alil poor'er but rarely people notice...

Read up and check if your 6ports are functioning fine and go to racing beat I think they sell a cat-delete pipe

btw your mustang ran like crap bcuz piston engines need back pressure, free flowing is great on a rotary but the piping shouldn't be too big in diameter for n/a

RX7General

^^ Thanks for the info ^^

RX7withNitrous

catless is the way to go.

RX7General

Will it make my gas milage worse or stay about the same? I average currently 18-22mpg. Going catless hurts torque and acceleration doesn't it?

GASnGO fd

when we took the cats off my fd the main cat was toast<fell to bits>i went to a hi flow cat for the main and dump pipe replaced the precat,made a good improvement,cant say i lost horsepower.

RX7General

It sucks getting a car from someone who got it from someone and they did not do any of the upgrades... I know already that mine has an after market full header exhaust installed, and I see 2 cats back to back after ther O2 sensor... I just don't know how to tell if they are high flows, stock, or gutted? I will probably cut through the exhaust pipe and look down the best I can to see whats what... This exhaust has no bolt onsections after the header flange on the block, so cutting and re welding is my only option. I'd like to think that since I got this ride I have found that alot of performance upgrades have been done... and whoever did it hopefully selected high flow cats as well.

RX7General

Update: I just read a thread about the cats having an air tube... I did notice my catylitic convertors say on there heat sheilds No Air Tube... So Anyone know does it mean I got some after market cats? I t looks like the entire exhaust is header, high flow cats, 2 1/2 inch pipe all the way and 2 mufflers...

trochoid

iTrader: (6)

Rotaries need to breathe, backpresure is a myth for them to run properly Since you have headers, there is a simple mod to tap one of the runners and run a 1/8" copper tube to the aux ports to keep them functioning, which keeps your low end torque. Replace the cat with a high flow presilencer or decent midmuffler such as a Borla.

RX7General

The prior owner emailed me some more details and he said the cats are high flow magna flow catylitic convertors... Do you still think for better performance I should remove them?

OneRotor

iTrader: (3)

Backpressure is also a myth when it comes to boingers running properly.

Any engine is just a glorified airpump. By putting a free-flowing intake and exhaust system on, you are just increasing the engine's pumping efficiency. Whoever tells you that you need backpressure is an idiot and does not need to be anywhere near a vehicle.

RX7General

Well, not sure about your piston engine knowledge but I've owned and worked on several... Including a 2002 Mustang that I learned don't fvck with the cats.. When I took them off and straight piped it, it was so bogged down and slow! I put the cats back on..... it was alive and accelerating normal again. I understand your theory, but back pressure has been proven to me first hand because I've tried so many rides and different setups. My question on back pressure only was related to the N/A rotary engines because I never did have a rotary untill recently... I know if mine was boosted, yeah take the cats and the mufflers off and go 3".

Chef-j

It's all depends on how engine design, some engine love air flow. Not all the piston engines need back pressure.

RX7General

I agree 100%. It can play a role in some though... These newer engines with emission controls are all calculated/designed to function with certain bends and diameter in the exhaust, and some requiring catylitic convertors to give final back pressure pulses.