Custom High flow cat to do or not to do?
 

Hey guys,

I recently bought power fc + commander, greddy profec spec B, megan downpipe midpipe, and blitz cat back . The other day getting my exhaust installed i notice the downpipe wouldn't fit cuz i have a jdm fd so i went and ordered a hks unit. Now i see under archives that midpipes would cause boost creep even though i got a power fc and greddy boost controller it wont stop it. So i'm left with no choice but to get a high flow cat! I was thinking of cutting my megan midpipe and welding the magnaflow cat i saw at canadian tire to make a custom high flow cat what do you guys think?

Cheers,

Charlie

Charlie you are going to want to properly mesure and by that I mean even if you have a straight section that is long enough you will want to make sure that it (the highflow) is not hitting the body as the Megan is V shaped and the tunnel is quite tight.

Some people experience boost creep with a midpipe some do not. Personally, boost was much more stable with my highflow.

The ebay mid pipes generally don't have the correct angles to weld in a standard sized cat. You could use a small metal core cat in one of those mid pipes. I did that some time ago. You are better off just getting rid of your mid pipe and getting a quality high flow cat that was designed to fit and engineered to work with the turbo rotary high exhaust heat.

Well as Adrian said the midpipe is v shaped and i'm sure that both sections of the pipe is long enough for the cat. my questions now is which side should i use? and if i successfully weld it and have it fit boost creep should be gone right? As for Gracer7-rx7 a high flow cat goes for around 325$ it is unlike me to do something custom but to me 325$ is alot compared to the cat that is only 80$ and i haven't seen any high flow cats available for sale on the forum.

So, stealing this thread a bit, has anyone run a high flow cat on a 3 rotor? I ask because I would like to get the gas smell out of the car. Would this possibly work and if so, what is the downside?

Here's some pictures to help you guys get an idea of what i'm dealing with it seems like a simple cutting and weld job just a matter of measurments.

i used to have a custom high-flow cat downpipe...can't remember if i sold it or if it's still in storage....

You could weld the cat into the MP. Honestly I would suggest going that route (as opposed to putting it on your DP).

Also, one thing I noticed when I installed my "Megan Racing" midpipe was that it is actually about an inch shorter than I'd prefer. This led to some pretty serious heat damage to my rear bumper. If you decide to cut and weld, I would install the whole thing, with your cat-back, before cutting and welding so you can get an idea for where your exhaust tip sits in relation to your bumper.

Flames are cool, burning through all the paint on your bumper is not...


Also, do you still have your stock airpump? If so be sure to get a cat with a plugin for that!! It helps a LOT when it comes to passing emissions.

Try getting that to work with the limited space in the tranny tunnel. Its not as easy as you think it is. Been there done that. Go ahead and try it if you like. don't forget to add in the cost of labor.

I have a friend that works at a body shop can weld it for me for free. And is the space really that tight with the space in the tranny tunnel? i saw the magnaflow cat at the store and didn't seem that big

Depends on the cat really. Do your research. It can get tricky depending on sizing.

I guess i'll buy the cat from canadian tire and if its too big i'll return it thanks alot for all of your help. By the way if you guys see a high flow cat for sale for cheap let me know.

Thanks ;)

If you have the time please post pics =) I was planning on doing the same...adding a 3" inlet outlet cat.

Dave, I thought someone bought one of the Knightsports Metallic Substrate cats to run on a 20B. I'm not sure if the project was ever completed.

Turns out the car is pig rich right now so my first order of business is to correct the AFR and then reassess if the car still smells like fuel. If so, I am going the cat route.

I made a custom cat-back some time ago and was going to take the stock cat and add 3" pipe to it. I never did the custom cat though.

Generally I say go for it because custom rocks!

here's one I had done a couple years ago, I still have it laying around somewhere since I replaced it with an SMB system. Anyone wants it?

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/another-custom-metal-substrate-cat-project-d-465198/

neit tyvm!!! I bought all the parts for it but wasnt sure what the outcome would be and its time to get the welds in this week!!!