2003 Toyota Highlander 3.0 V6

toyota
exhaustsystems
highlander

#1

Okay, I’ve thought long and hard about this and I think I’m prepared to ask my first stupid question. I’ve only worked with older and mostly American makes, so I’m clueless about this kinda stuff. This car has THREE catalytic converters and two mufflers (California emissions compliant). My question is about the removal of at least two cats and one muffler. I don’t give a care about the sound but the fuel mileage of this vehicle is horrendous, especially considering that it’s newer and has such a tiny engine. Do all those oxygen sensors associated with the cats tell the ECM of anything else how to behave? Would I be doing something rather stupid by removing any of this hardware? The state where the car is now located requires only that each vehicle have a cat so I want to know if I can remove this crap to eliminate all that back-pressure in the exhaust?


#2

What kind of fuel mileage are you getting and how is it being determined?

How have you determined that the converters are causing too much back pressure?

Without a ton of details provided about the vehicle the only suggestion I can make at this point is that you not gut the exhaust system.


#3
The state where the car is now located requires only that each vehicle have a cat so I want to know if I can remove this crap to eliminate all that back-pressure in the exhaust? -

Your state has some laws…but the Feds trump states laws.

Federal law states you are NOT allowed to remove any manufacturer installed emissions. Now in reality no will may ever know it was actually done.

No to your original problem. Removing the cats may NOT necessarily mean you’ll get better gas mileage. And if you remove the cats you’ll have to fake out the O2 sensors.

And as OK asked…what kind of gas mileage are you getting. This is an SUV. It’s NOT a small commuter vehicle. If you get over 22mpg I’d be very very surprised. The new Highlander- Hybrid gets 28mpg. So expect a lot less then that vehicle.


#4

According to the EPA, a 2WD Highlander should get 17 city, 21 highway (18 avg). 4WD is about the same with 16/21/18. How does hour mileage compare, and what type of driving do you do?


#5

You thought long and hard? Why do u think removing cats/muffs will improve your mileage?


#6

Bad idea. Fix the problems, don’t butcher it. It’s not 1980 anymore.


#7

If I were to free up the exhaust flow, I would delete the common catalytic converter and run dual exhaust pipes back to turbo mufflers with exit pipes just before the wheels. As a result I would keep the bank 1 and 2 catalytic converters pre and post O2 sensors as well as the integrity of the OBDII system. A good exhaust shop should be able to build you up a satisfactory system. You might talk to them about headers and freer flowing catalytic converters.

Be aware that most power inhancers come with an MPG penalty. The MPG liabilities come with the frontal area of the vehicle, vehicle weight, the agressiveness of the tire tread pattern, and the agressiveness of the driver(s).

Hope this helps.


#8

I’m with those that say if it ain’t broke, don’t fix it. If it’s operating properly an providing the advertised mileage, you’re more likely to cause operating problems than to improve your mileage. Any serious and properly done changes, such as Researcher suggests, would be much more likely to provide a bit more power at the expense of a bit less mileage.

There are no free rides left anymore. For the record, I modified my induction system to provide a bit more power on the highway. I was surprised at how well the modifications worked…but I accepted that when I drove aggressively I’d get reduced mileage. Real world, when I drive aggressively I get about 2mpg less mileage. It’s worth it to me, but I knew going in that this was likely to happen.

If you want better mileage, I’m afraid your best bet is to look to other models.