I have been measuring all the pipes on my exhaust.

The front side on the catalysators are 3" and the rear side it is 2.5".

After the flange it goes down to 2" and end up in a y pipe that goes into the middle resonator. I can see that i forgot to measure right after the y pipe before the resonator. But i think it might be 2.5".

The back side of the resonator is 2.5 and the pipe goes to a Y pipe and then the two pipes are 2" and goes into the side of the two resonators.

After the two resonators the pipes are about 45mm thick. Thats about 1.8" almost 2".

So my question is like this.. Alot of people says that i should go 2.25 all the way, and PD you says that i should not go with different sizes. But why do Toyota do it then? I know you like it to be almost original?

3UZFTE, thank you for your reply. I sure think after your post and after my measuring that 2.5" will be too big all the way.

I am thinking og buying all my resonators and catalysators from Magnaflow and also buy the nescesary size pipes for the best result. I live in Denmark so the weight of the resonators of course cost some to get shipped but i think this will be the best thing to do.

So can anyone help me choose the right sizes and resonators. I will make a DIY when i get all the stuff together and weld the exhaust. Make some videos and take some pictures for other members to see.

 

Do you have emissions/smog in Denmark? If not, I would say that you can possibly just remove them altogether. You have 2 cats, a resonator, and 2 mufflers, and you really don't need any of them if your not worried about pollution or sound. Not having a cats might set a CEL/MIL code, but it might not, I don't know for sure. Being that it's a 91' OBD1, I doubt it would cause any issues, but it could effect your fuel trim/efficiency. If your going to go the cat route, you should buck up and buy some nice ones, or run your OE cats. One thing you will find is that the flanges that meet up with the exhaust manifolds are a unique style. You can easily fab your own, or pick some up from some online distributors, but don't expect to go down to NAPA and for them to have the flange in stock, your better off trying to re-use your factory flanges.

General rule of thumb. Cats work buy platinum and other precious metals that basically get super hot, and vaporize any unburnt/leftover fuel, to reduce pollution. Platinum goes for over $1000 a troy OZ., which is why OE and good cats are so expensive. How much platinum do you think your getting when you pay $99 for a cat, probably next to none. It's a matter of time until your either replacing it, or just living with that that it can't keep up. Either run a GOOD replacement cat, or run the OE cats, or don't run a cat at all.

 

OK, just now saw this.

Dual 2.00" from the catalysts into a single 2.5" center split back into dual 2.00" is the BEST size for your car. This is slightly larger than the stock pipes. Actually if possible locate another STOCK Y pipe as the merge collector is very good at making torque which is what a heavy car with a small 4 liter needs.

Remember that even though these engines were rated 250hp they were overrated and make around 230hp. The have the SAME exhaust size (dual 50mm into single 60mm) that the acurately rated 300hp GS400 and GS430s. Trust me... you do not want bigger pipes and you want that stock merge collector. Go with the 2" into a single 2.5"

 

Hi guys.

At first i would like to say that the sound means alot for me. Read my first posts. I dont want a ricer rattling v8 can sound. i'm more into deep AMG sounds. I know i cant get that exact sound but something simillar. I have heard when people remove everything and use a straight pipe and that sounds bad if you ask me.

In Denmark we have pollution test, smog test, so i have to use cats. At the last inspection i had to weld some small holes IN my cat. so you can imagine how rusty this exhaust is. The main problem i guess is that they put salt on the road during the wintertime. it really sucks.

Well, then what cats should i use? I was thinking of using the original flange and weld it to a new stainless steel cat. and use stainless steel flanges the other places. Actually i was thinking of reusing the old rear mufflers because they arent worn out at all. also the rear piping from y pipe and back are in good shape, so i might just reuse this. but i will install a new middle resonator and all the pipes up to the manifold. so it sounds like i'm going oem size. and maybe use a more free flow resonator to maybe get a little more sound without having drone sound in the cabin?

But what cats should i use then? Sounds expensive. The $99 magnaflow cats on ebay isnt anything worth really?

There is really not alot of space for cats so i think its hard to get something that fits.

Maybe i should look after some 93-93 cats. I know the exhaust is stainless steel right? maybe the cats are also? well if its possible to get some in good shape with low mileage one them. sounds like a tough job.

I already ordered magnaflow 3" rounded tips with 15 degree rolled edge. oem look just a tan bigger ;-)

 

Just found out that the direct fit cat from magnaflow is available on ebay for $129.

So that would say i dont have to reuse the old flange. Would be nice with the stainless steel flange on the magnaflow for easy fit. Just noticed on the picture it says 2.65" at the front flange. I measured it as 3" hmmm.. Maybe the US exhaust are not the same as europe?

http://www.magnaflow.com/02catalytic...irectfit=93162

Well, my old cats are defintitive done, so i'm thinking that i might as well get these direct fit magnas and make new piping and middle resonator down to the rear y pipe.

 

b b b b bump...