mr2 catalytic coverter

[jus7o]

hello

i wanted to know if there is a bolt on catalytic converter for my 86 mr2 with an input size of 2 1/4 1inch and an output size of 2"?

thanks

[Mista 2]

Your best bet it to have a look at your local parts shop. I can get them but i am in australia and I dont think Walker ship exhaust parts to America.

[jus7o]

thanks Mista 2

the trd header outlet is 2 1/4" and while the Hks muffler inlet is 2"
can i just use a cat with either a 2" or 2 1/4 " flange on both inlet and outlet? any problems with this set up?

[Mista 2]

Well im not too sure about that one. I would not go for the 2 inch cat as the that would make the exhaust gasses terbulant just before the cat.

[jus7o]

then how about 2 1/4 cat but how long does it have to be all the stock replacement cats are 2" outlet only so how long is a stock aw11 cat?

thanks

[Mista 2]

That one i dont know, sorry. It has been a long time since my car had the standard cat and my info at work doesnt have the AW11 MR2's.

sorry again

Jordan

[jus7o]

Am i right on that? is the TRD header outlet flange to the cat 2.25"? and is the HKS muffler input 2"? can anyone confirm?

thanks

[te51levin]

Let's start at the beginning. Do you currently have the TRD header and the HKS muffler? If not, TRD headers have been discontinued for some time, so you may not find one easily, and HKS makes the muffler in supercharged configuration, so you might get that instead.

If you already have the parts, I can make you a cat that will fit your header and muffler perfectly. If I get all the info I need, it will be a direct bolt in. If I use a standard Magnaflow blank it will cost you about $125 for the whole thing (figure $135 shipped to a US address). I will want to see the flanges on the parts you have to make sure I have all the information I need. Can you post clear, sharp pics of the flanges, and measure the inside diameter of both the header outlet and the muffler inlet pipes?

Ideally, you'd want to carry the larger tubing diameter all the way to (and through) the muffler. You can do that by selling the NA muffler and buying an SC version. If that is not practical or economical, you can have your local exhaust shop cut off the muffler inlet flange and expand the pipe to 2.25" so that you have a smooth transition to the smaller tubing. I can also include an extra flange that you can have a local shop weld on if you go that route. They are $4-8 each depending on which style you need.

Here's a cat and downpipe I made up for another AW11 owner



There are more pics of the downpipes I've made here if you want to take a look:
20v exhaust

[jus7o]

Levin: Ok but first let me start by saying youre _F_ucking awesome ive read some of your helpful threads and posts - ur the man!

yes i have a TRD header and N/A HKS muffler. I've mesured the outlet flange of the TRD header and I read 2.25" and the HKS muffler has a inlet of 2". I didnt know the supercharged version had 2.25" piping if i did then this the would have been ALOT easier.

so if i decide to have you make me the custom cat what size cat would you use? and how will you do it? Would you use a 2.25" cat and neck down the outlet to 2"??

would there be any difference in overall transition/flow from 2.25" to 2" between chosing the cat option or muffler option?

ill get some pics up for you tomorrow.

thanks for your help.

[te51levin]

Thanks for the kind words

The best way to do it, if we absolutely had to use your NA muffler, would be a gradual reduction in diameter. That's going to be very difficult to accomplish within the catalytic converter without a pretty spendy stainless reducer. You'd want to use stainless rather than the super-soft low-grade mild steel reducers most parts stores carry. The better option would be to reduce the diameter at the cat outlet rather than the inlet; the exhaust gases have to flare out from the inlet pipe to the catalytic element, whereas at the outlet, they are converging toward the outlet spout anyway. The outlet is thus the more logical place to reduce pipe diameter.

If I were in your shoes, I would use a 2.25" cat and just live with the mismatch where the cat meets the muffler. It is not ideal, but it does allow you to upgrade to a better muffler down the road (HKS SC, or Toyota SC, or one of my own design if that ship ever sails). If we build the cat 2.25" all the way through now, it'll be a better match for the bigger muffler when you get to that point.

[jus7o]

If I were in your shoes, I would use a 2.25" cat and just live with the mismatch where the cat meets the muffler. It is not ideal, but it does allow you to upgrade to a better muffler down the road (HKS SC, or Toyota SC, or one of my own design if that ship ever sails). If we build the cat 2.25" all the way through now, it'll be a better match for the bigger muffler when you get to that point.

i dont plan on it the HKS muffler i have cost 300 bucks so i wanna work with it.

The better option would be to reduce the diameter at the cat outlet rather than the inlet; the exhaust gases have to flare out from the inlet pipe to the catalytic element, whereas at the outlet, they are converging toward the outlet spout anyway. The outlet is thus the more logical place to reduce pipe diameter.

thats exactly what i was i thinking!

lets do it!

thanks

[jus7o]

is that .25" really a big difference??????????????///////////////////////

[te51levin]

Probably not, unless you are chasing every last horsepower. I would still like to see some good pics of the header outlet and muffler inlet, center-to-center measurements of bolt holes on both parts, and pipe inside diameter, at the flange, measured with a caliper. I like to make things as accurate as I can.

[jus7o]

sent you email.

[Teado]

Originally Posted by jus7o

is that .25" really a big difference??????????????///////////////////////

According to Ron Jeremy... yes





I'd like to see pics of what comes out of this!

[te51levin]

jus7o - I can't find the mail you sent me. I'm up and running again, trying to sort out who wants what, but I can't find your info. Do you still want me to make you a cat?

[jus7o]

no i dont need a custom cat im going to have the shop where my car is at make me a test pipe but maybe later ill shoot you a email and let you know

thanks again for you help

[te51levin]

Oh, OK. I can do test pipes too if you need - $35 and up depending on paint, gaskets, etc:
20v exhaust