Catalytic Converter: Suggestions
 

Hey guys,
I've been driving around now for years with a full 3" downpipe, no cat, and Tanabe touring exhaust.
Obviously, the car overboosts if you let it. I don't drive the car very hard, as I just enjoy it as it is without romping on it.

However, I would like to protect the engine and be able to boost safely without going too much more overboard with modifications. (Injectors are stock, and I have a 255 lph walbro pump.)

Are there some suggestions for a 3" cat that people have had experience using that will limit the flow to prevent over boost?

Thanks,

Why not just upgrade the wastegate to stop the overboosting...

I have the Bonez hi flow cat from rx7.com. It is a high quality cat that should solve your over boost issues.

If you are only wanting to get the boost under control, you really should port the wastegate. Also, if you are using the factory boost control solenoids, they will run away with boost a lot of times, an aftermarket controller or a better valve with PowerFC control goes a long way.

You could also experiment with restrictor plates.

Most high-flow cats are designed to flow well, they shouldn't choke down the car that much if designed right. You should really look at one for passing emissions or reducing exhaust stink. Otherwise it's a lot of money for what you are looking to accomplish.

Dale

Thanks for the replies, friends.

I am aware of the possibilities of porting the WG, but I was trying to avoid removing the turbos to do that.

I think I'll look into the hi-flow cat option as well as the solenoid function.

Oh, I was going to give recommendations. The Bonez cat from Rotary Performance is really nice and does well, from what I understand it will pass emissions. If you want to go up a notch in quality, the SMB cat from Australia is exceptional. I have been running one for 10 years with no problems, it's super well built and hasn't been run with an air pump. It's pricey right now but is amazing. When I bought it the Australian dollar was weak and I got it for like $450 shipped or something.

Dale

Because removing the DP and turbos with the engine in the car...then doing the porting is a huge pita compared to adding a cat? Not to mention the risk of breaking studs or having to buy expensive gaskets? Running with a midpipe makes the car stink? And he might like the change in sound? :)

Another vote for BONEZ. I don't have anything to compare it too, but that's just it...it was in the car 15 years ago (~ 80k ago) when I bought it and it's STILL going strong. Most of that was without an AP. All stainless, good thick flanges and seems to flow well.

install high flow cat and see what happens, if it still over boosts then get a racing beat dual tip and try that..

Pettit 3" stainless high flow cat is hard to beat.


http://shop.pettitracing.com/ss-hi-f...-p-120068.html

I have a bonez cat on my car for about a little over a year now and for some reason the fumes still smell pretty bad especially when coming to a stop.
I want to go with a straight midpipe and would be up for trading if i didnt need this cat to pass inspection.

btw how does your car sound with a midpipe? I have the same exhaust set up.

Hmm, interesting.
I'll have to crawl under the car again and see how the Tanabe is again.
I wonder if this Pettit system can literally just bolt in, and I replace the mid-pipe area.

That would be super convenient.

Kinda like... BBRRRR BRRR BRRRRRRR BRRRRR.... :lol:

Nah, it's a very subdued tone/note which is a joy after years of riding around in open exhaust 2JZ supras. I love the Tanabe exhaust. In my opinion it's quiet, but has a good tone when you open it up a little with the throttle. Let me put it this way, it's quiet enough to still clearly hear the stock BOV even at around 1-2psi of boost. Doesn't drone... just all around perfect for me.

(Added some pics.)

Yes it’ll bolt right up between the midpipe and catback.

I ageee! Exact reason why I bought this exhaust. Glad to head it’s still relatively quiet with a midpipe

Thanks for the feedback.
I'll confirm everything under the car, then probably order that piece.
As with all my threads, I'll make sure to post my results later for anyone else looking/searching for similar issues.

On my FD I bought a used resonated mid pipe and it had boost creep even when bypassing the stock boost "control" with MBCs.

I put in a reducer plate between the midpipe and the catback that controlled the boost creep.

Then I bought a used 3" SMB catted and resonated mid pipe and I really enjoyed the lack of hydrocarbon stink/sting and the reduced noise with a nice deep sound and it also controlled boost creep to 10psi with stock intake no problems (No reducer plate required).

I don't understand the point of a restricter plate when you can just put a cat in there and lose the smell. It's probably not that big of a difference in restriction. I suppose you don't have to be concerned about burning up a cat if you don't have one but yeah having to deal with the smell gets old after a while.

Yes it does... Because most of the time I'm convincing myself "That's just the exhaust... you don't have a fuel leak... Nope.. No fuel leak at all..."

I have the Bonez cat with air pump and just passed Colorado emissions.

A restrictor plate and a catalytic converter are pretty far apart in terms of restriction IMO. I'm talking a 2.75 inch restrictor in a 3 inch pipe...... cats have their place be it OEM or Bonez but not when your power goals exceed 400 rwhp. Losing the smell is great and all but not if you lose 50 rwhp along with it :)

I do think when the issue is stock twins and the small WG, just run a high flow cat and be done with it at the power levels those little guys allow. Full open exhaust on stock twin turbos is about as silly as running a bridgeported engine with the Hitachis.

I'd never consider installing one on my BB 95 car as I can't see any kind of cat working well on a nice single setup at 20 psi. I'll check out the SMB given Dale's experience for future builds etc, I know those crazy Aussies love their rotaries and make some good stuff :D

Also, I think SMB has a "big" high flow cat, I seem to remember someone had that done. They can do some crazy custom stuff if you want.

The build quality and fit of my SMB cat is gorgeous.

Here's their page -
SMB Full Exhaust Systems-Mazda RX-7

Their website is garbage, though. Does have some pics of their products.

Dale

Anyone has any comment on
The vibrant cat?

http://www.vibrantperformance.com/ca...Path=1527_1326

I'd be interested in seeing your experience and data regarding why a high flow cat wouldn't work on a 400whp+ car. We have made 460 whp @ 20lbs (Mustang dyno numbers) through a Bonez high flow cat. The setup was limited by the s360 turbo as the motor and exhaust out flowed it. I've had multiple cars on twins boost creep with the high flow cat. Its not a significant restriction. Some people want to be environmentally responsible and emissions compliant. Nothing wrong with that.

Recently went with a Vibrant Ultra High output cat (p/n 7830 from the link above) on my FD in conjunction with an EFR 7670 turbo. Have mostly used a Bonez high flow cat the last 10 yrs or so with Efini twins, and wanted to give the Vibrant unit a test run. Interestingly enough, we weren't able to boost higher than 10-11 psi on the new turbo setup. Not sure if the Vibrant cat is the primary restriction or not (but obviously no boost creep with it, either).

Seems to knock down the odors well-enough. Not sure if it can pass a legitimate emissions test, though.

FWIW, you can make power with a metallic sub cat -

https://www.rx7club.com/single-turbo...2-psi-1055993/

454 whp with an RT cat (they aren't around anymore I think).

If power / smell is your main concern, go with smb. If emissions is your goal, go for bonez or pettit.

461 whp/372 tq with our ported and studded motor, S360 single turbo kit, Bonez high flow cat, and Racing Beat catback. These numbers would equate to about 530hp on a Dynojet factoring in the 15% difference commonly found. The cat is not the issue.