I have a 420sel, 1987.

If I remove the O2 sensor, cats and modify the exhaust, will I gain some Hp #'s? This is with NO engine mods at all.

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2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6

Of course, an easy 500hp just by removing the parts that keep your car from being a gross polluter. If only all hot rodders were this responsible.

i dont know. but in removing the o2 sensor and cat you have changed all the parameters that the engine was designed for and unless you know what you are actually doing you may well lose power.

removing the muffler or mufflers would prob give a little more power. and making the exhause bigger too might help a little.

personally i wouldnt take the sensor and cat off.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Oh yeah sort of like Professor Chaos trying to destroy the world with aerosol cans.

I would just experiment. Get a G-Tech Pro or something or if you can afford it go to a dyno. You can disconnect the O2 sensors in 30 seconds there is no need to take them out. You could start by just taking the exhaust off right before the cats. The only reason to disconnect the O2 sensors is if you are getting more fuel. The standard operating ratio is 14.7 air to fuel the optimal is somewhere near 12.5. You could see what the ratio is under full throttle with a wideband A/F meter at a dyno and may need an aftermarket chip to get it lower with the O2 sensor(s) disconnected. To improve performance you need at least these three: increased timing, slightly higher octane fuel, A/F ratio around 12.5 and possibly a less restrictive exhaust. Good luck and have fun.