[zoomie]

How come no one's talked about getting a performance high flow catalytic converter for the 4.2 rav4's? Something I should be concerned about? I figured for under $100 everyone would be jumping on it? Maybe i'm justs a wacko falling for the big hype. What's everyone's take on a high flow cat?

 

[jedimaster]

They make a big difference if they're made right. I'd go for it- but it's best used with other mods- as a standalone, I don't think it'd regsiter much if at all on the butt dyno.

 

[zoomie]

JEDIMASTER: what do you mean if they'r made right? Do you have experience with a particular brand you recommend? I plan to use it with a CAI, but no performance exhaust nor header. What performance gain if any can I expect from what you've seen?

 

[jedimaster]

Well, for the Subaru community, there are a lot of hfc options. Typically, we see 10-15 hp gains at the wheels. But that's in a turbo car and usually with additional engine management. I'd imagine that on an na car you'd see a difference, but maybe not as dramatic. Basically, as the engine is an air pump, you get more air in and out of the engine more efficiently, you get more power.

My vehicle is a 2005 Outback 2.5XT (sold a 2002 WRX wagon to get it, which was heavily modded). With a bigger downpipe (no cat in it) and the COBB AccessPort I am supposed to be at around 310 hp and 360 torque. The car is a beast. There's a company called Crucial Racing coming out with a high flow cat for the car very soon and it's supposed to get an additional 10-15 whp.

Sorry, long answer to a short question

BTW, nice thing about making it more efficient up to this point is that not only is it powerful, it gets much better gas mileage. When you have to put premium in, that's a definite bonus!

 

[Mohit]

a high flow cat on a car with stock exhaust is going to do crap all. on a rav you should get 10-15% more power with a cai, sports headers, high flow cat, bigger exhaust piping and sports muffler.

 

[jedimaster]

I have to disagree. ANY restriction you remove will net you something. HFC= high flow cat, which is less restrictive

But the setup you note with header and larger diameter piping sounds good- what about EM? Gotta take advantage of that with a good tune.

 

[Mohit]

You are forgetting about the stock exhaust piping. If you were to replace the original cat with a high flow one you still have the original (and restrictive) exhaust piping and drum muffler behind it!

 

[jedimaster]

Yes, I realize that, but you still remove a large restriction, piping diameter notwithstanding. At any rate, opinions are like...you know the rest

 

[zoomie]

Thanks all who have responded. But that's enough theory. There's plenty of info online about the technicalities of the modification. Let's hear something about actual experience. Stuff I can hear from you but no one else. Have you guys driven a friend's car that was stock with only a high flow cat installed?

I know all these crazy mods will mess up the low end torque, but i'm just trying to juice out all I can from the tiny little rav4.

 

[Jeff]

On the 2001-2003 Ravs the header and catalytic converters (there are two side by side) are integrated into one unit. So if you wanted to replace the cat you would also have to replace the header.

 

[Mohit]

That's the same setup as the 4.1 (header and cat are one piece). The reason no one has put a high flow cat on a RAV with a stock exhaust (apart from it being impossible without getting different headers) is that no one is dumb enough to do it. Instead put your money towards a custom made cat back...much better gains.

 

[RAV4Don]

From my experience the older design pelletized cats (mostly pre-90's) were fairly restrictive and their removal reduced backpressure considerably even without improving the rest of the exhasut system. Newer cats with the honey comb design have much less flow reduction if in good condition. Aftermarket cats alone only provide nomial gains from what I see on the chassis dynos. Of course any clogged cat will result in a significant flow impediment and hurt HP and mileage.

Increasing the cat's pipe diameter (and the remainder of the systems diameter) can improve flow to a point. A cat back sytem can be a benefit if it either increases the pipe diameter, has higher flow muffler, or has mandrel bent pipes (or all three).

IMHO, a well designed longer tube header provides the best bang for the buck.

 

[Jeff]

Rav4Don's right, cats have improved over the years in terms of flow and reduced restriction. The honeycomb cats (like the Rav has) do not create as much back pressure. However, modern engines require a certain amount of back pressure to work correctly, and if you reduce it too much (such as removing the cat) the engine will actually lose power and fuel economy will go down.

These days it's really not worth replacing the cat unless you can get one cheap and you are also replacing the rest of the exhaust.

 

[zoomie]

Jeff: got it, thanks. I had only recently learned that our cat is integrated into the header. No wonder i didn't see anything when it was crawling on the ground looking under the car.

MOHIT: The reason i'd like a high flow cat is b/c i'd like my car to continue to appear stock. I'd rather not have a big exhaust thing in the back. I don't think clients would be impressed. If you think this is a dumb idea, I'm definitely open to suggestions on anything you may think is NOT dumb. What advice do you have for improving performance without changing the look of the car too drastically?

 

[Mohit]

I would recommend you get a cat back exhaust. Go 2.25" exhaust piping from the cat into a resonator into a universal fit sports muffler into a 3" stainless steel exhaust tip. Check out some local exhaust shops to see what they offer in universal fit sports mufflers