Not sure yet. Motor is still in the car. I'm trying a good MMO soak first to see if I can correct a stuck seal. It's idles fairly well and runs fine but starts hard and you can hear a miss at idle. I don't drive it very often so I'm crossing my fingers for a stuck seal or carbon crud somewhere. Compression test after the de-cruding. I'll have to have it taken apart if this doesn't cure the issue.

Or without going deaf...

Abbreviated version of my post (I'm an idiot and clicked the wrong button and deleted my previous long form reply....).

I have a single turbo, aftermarket ecu car w/ OMP and premix .5oz/gallon. I live in west LA (green juice capital) so I have to run a cat or else risk getting harasses by swarms of priuses, plus I hate smelling like a gas station after driving the car.

I've blown out both magnaflow and Bonez cats. I think mostly due to crap tuning on the car, but still question whether they'd last very long on a high hp single turbo car. They're ceramic cats so a couple solid back fires and they'll start to crack apart.
Currently have a Vibrant GESI metallic cat and so far it's been great. Newly installed single turbo setup and much better turn on the car to help it along. Very little smell at idle at 13 AFR. Although hard to eliminate back firing completely. ie i run ign cut at rev limit as it's safer for the engine. I also run a quick fuel cut on decel to preserve the cat. If you want to shoot fire like youtubers/instagrammer, forget running a cat, you're wasting money.

From my research german cat brand HJS makes the highest end cats. They're used by german OEMs and in some supercar after market parts. They make a motorsports 100 cell line which is prob perfect for rx7s. Down side is they're 2x the cost of the GESI cat. Fabspeed sells them in the US. $900 (just the cat) for the ideal one for the rx7.

High end cats have much higher content of catalytic previous metals than cheap ones. This makes them more effective at reducing emissions. Hard to know the previous metal content of each aftermarket cat but I'd guess that a OEM level cat like the HJS would be much better than the magnaflow which costs <$200 for just the cat.

Would be great if someone could work up an aftermarket airpump setup for single turbo cars. Some OEM cars have electric air pumps which might be easier to integrate vs the stock mechanical setup.

HJS Catalyst Summary

^quick & informative writeup of HJS catalyst technology

Has anyone noticed any difference with power and turbo response after installing the Vibrant GESI catalytic converter?

I currently have the Vibrant SHO version with the 4 1/2" canister rated for 550 hp. I used to have the SMB 100 cell metal cat before and the spool was better than the Bonez brick-type cat I had before that. Power was likely better too since it was more free flowing with less backpressure. I have changed so many things, including different turbos, since installing the Vibrant I can't directly compare. One thing to know, my old SMB cat partially melted and Vibrant has a much higher melting point. Also, NO SMELL at idle with my idle AFR of low 13's with the Vibrant which leads to a happy spouse. LOL
Mike

Yeah, smelling like fumes and having to vent the garage for a while is getting old. Does it quiet down the car as well as a resonator?

Right now I'm running an EFR 9174 with a 3.5" DP, which goes to a 3.5" mid-pipe (straight through), to a 3" HKS Hi-power. It's deafening driving on the freeway. I was planning in swapping in the Racing beat 3" cat-back dual tip. The question is if it's worth trying to keep the mid-pipe 3.5" and add the Vibrant cat or to just go 3"? Also, considering if a resonator is also needed, not knowing how loud it will be.

I may be the only 3 rotor guy to run a cat on his/her car. Wanted to get rid of the stink so tried a few units. Settled on the MBS 100 cell unit and have had it installed for around 3 years:

High Flow Catalytic Converters - Mandrel Bending Solutions

Holds up to the heat of the rotary and eliminates a good bit of the stink. The 200 cell would eliminate more of the smell but I was worried about the restriction. And yes, you can make good power using a high-flow cat. Here is my dyno at 20 PSI:

https://www.rx7club.com/attachments/...71004_0002.jpg

I have a smaller SMB oval absorptive muffler right behind the cat in the mid pipe area. It does quite the car down some and the cat itself does too. I have an old RSR cat back. It is a little loud overall but not bad at all. I can still hear my stereo well and I can carry on a normal conversation with a passenger without raising my voice. Overall, good combination of less restrictive flow and good drivability I think.
Mike

The Vibrant is the SHO which comes in 3",3.5", and 4" inflow and outflow and is rated for racing and 500-850 hp. Melting temp is 1600. It is a 300 cell and is OBDII rated for emissions. I believe it would fine for a 3 rotor depending on your HP. May be a little more restrictive than your 100 cell, but the smell of the exhaust should be much better. This trade off I would accept and you might too. I will again say that at idle in order to have no appreciable smell the AFR needs to be around 13 if idle is possible on your 3 rotor this lean. If not, I found around 12.5 the smell is noticeable but still ok and below 12, it is more bothersome.
Mike

Nice!

Must have been tough fitting that cat with a 4" inlet and 5" outlet. For sure too much for my application.

Would you say it would make much of a performance difference if I used the 3" Vibrant cat instead of the 3.5"? My current down-pipe is 3.5" and the straight mid-pipe is also 3.5", but the cat-back tapers to 3", which I read is ok since the exhaust has cooled some and is more dense. Seems like the local muffler shops aren't as comfortable making 3.5" piping since they can't bend it in-house and would have to weld together bent pieces. Running an EFR 9174 on a ported engine, making 500rwhp.

A 300 cell would most definitely improve the "stink" even better than my 100 cell unit, but I wanted max air flow with an improvement in the smell. MBS sells (or alt least used to) 200 cell units and I thought about one day giving that a try. A 300 cell unit? Maybe, but that is a lot of restriction. Would be interesting to try them all and document the differences in WHP.

The 3 rotor idles at a little above 13 AFR.

I didn't. When I bought the MBS cat, they sold it in a 3.5" inlet/outlet configuration, so that is what is on my car. I see they don't have many cats currently listed, but I'd give them a call as they used to offer many different configurations.

@netseven
Order the Vibrant 7835 UHO catalytic converter (3.5"), and have your local shop weld it in place via your existing midpipe. The custom shop that installed my single turbo kit had it done with no issues at all, and cost was fairly minimal if I recall.

In my case, the shop simply removed the middle section catalytic converter of the Bonez midpipe, and welded in the Vibrant unit. I plan to swap in a new cat in similar fashion every few years or so as needed to keep odors in check. I'm also considering a resonated midpipe/Vibrant cat combo for that same section of piping.

Note: JEGS is showing the 3" & 3.5" UHO (ultra high output) converters at $450 currently.

+1
IMO, I would definitely stay 3.5" as Topolino said. At 500rwhp, the 3" piping would be to restrictive. The cat will add to that. I would also consider upgrading your catback since is it is only 3".
Mike

How many cells on the Vibrant 7830 UHO unit? I don't see it listed.My tuner recommended a 200 cell.

The HJS units certainly look nice, and I love all the info available, but fabwork will be more expensive as its just the cat itself and doesn't come with the reducers needed.

Net Seven, how do you like your setup? im 8374 now and am curious how it compares to the 9174?

^ The 7830 is a 300 cell unit:

https://vibrantperformance.com/catal...84d9d0c238ae2b

I believe all of the GESi OBD2 High Performance Catalytic Converters are 300 cell units. Vibrant does make a 200 cell unit, in another product line:

https://vibrantperformance.com/catal...107a8a836cadc7

Not sure of the heat rating on the 200 cell unit, nor it's "cleaning" capabilities. You could contact Vibrant for more info.

The page says "2. This converter is NOT to be used in a turbo or supercharged application. Warranty will not apply in this instance." so I'm sure it wont work on a rotary.

I just bought the car with the 9174 installed and it made awesome power during the test drives. Then I found out there are some issues with the car, so it's getting fixed now. I just hope there isn't any permanent engine damage from a few hard runs before I discovered the issues.. log showed 13.1AFR at 15PSI, 7,500rpm.

Honestly though, the 8374 is supposed to be a tiny bit more responsive, but makes a little less top end. I'm not looking to make crazy power, so I would have went with the 8374 for better response if I was buying a new EFR.

In the last week I've read and heard a million different opinions about exhaust sizes. I've heard it's only really important to have the bigger piping for the down-pipe, because that's when the exhaust is the hottest and as it goes down the pipe it cools and becomes more dense, so you could taper down the piping and maintain the same flow. A lot of tuners and rotary shops told me 3" is plenty big enough. Howard Coleman is making something like 580rwhp on 3" piping he said and doesn't see it as an issue. Personally, I think keeping the mid-pipe at 3.5" will help because I'm adding a cat that's more restrictive than a resonator. Not sure if going 3.5" on the cat-back is going to change much since it's so far back. Feel free to change my mind as I'm just going off all the different opinions I've heard recently.

I agree that further back the exhaust is much cooler and denser and many air flow systems such as HVAC ductwork tapers for increasing velocity distally. Therefore, the ability of overall volume/time exiting the tailpipe would be very similar in a straight pipe system. IMO, however, in our typical catback systems the catback is where the piping is most tortuous i.e. the junction just beyond the midpipe and the proximal catback in the Racing Beat and some similar other systems. It has to bend here and the flow dynamics here suffers. If you then decrease the diameter of the piping, you add yet another negative to the flow dynamics of the bend. The degree in which it adversely affects it is not great (particulary at low flow rates), but at higher flow rates it is more important and everything helps. You may have seen on the forum many people talking about the newer Racing Beat catbacks being restrictive and costing them RWHP, that is why, it's that first tight bend. True, a well designed 3" system could be better than a fair or poorly designed 3.5" system. It all depends on the flow dynamics of the piping, velocity of the exhaust, volume of the exhaust, and most importantly the number and degree of bends and mandrel vs. non-mandrel bends.
Mike

Fair points. I didn't know that Racing Beat changed their exhaust system, but the dual tip on my other FD does seem to have a much more drastic bend than other cat-back systems.

I was actually considering this:
"3.5" stainless steel mandrel bent exhaust system designed to work with our Y-pipe and headers."
https://www.hinsonsupercars.com/p-74...ust-35-ss.aspx

It's supposed to go from the y-pipe all the way through and out the back. I called and spoke to someone at Hinson and he said basically, it's setup to be a straight pipe that goes all the way out the back and you have the option to weld in a muffler if you would like. They were supposed to send me pics of it mounted up so I can see if the V-8 y-pipe location would be pretty close to where the 13BREW downpipe is. If that's the case, pretty easy to weld in a cat and a muffler and have a nice flowing exhaust system. No guess work on the exhaust shop's part.

Looks well made. If you use it make sure you carefully map out where the cat is. On my previous SMB cat and small additional oval absorptive-type straight-through midpipe muffler(I still use it with the Vibrant cat), made off the car and shipped from Australian, the cat hit against my Banzai trans support bracket because it was further forward than typical and since SMB had no idea I had the modified bracket. I had to take my previous downpipe off(a pain in the butt) on a twin with heat shields and take it to a exhaust shop to bend the downpipe a little to make it fit.
Mike

I just ordered all the parts for a full 3.5" exhaust system and will probably have the exhaust shop install it next week. I already have a 3.5" downpipe that will remain, but the rest will be completely replaced. From downpipe back, I'm installing the Vibrant GESi UHO 3.5" in/out cat, followed by a small magnaflow 5x8 (6" long) racing muffler and finishing off at the back with the Racing Beat 3.5" muffler. I'll let you guys know how it sounds.

Net Seven, did you get that exhaust system installed? I'm curious to hear your results. Thanks bud

I bought this one
https://vibrantperformance.com/catal...2b072944a19cf5

plan to get it installed here hopefully in a week or two

I have the 7670 EFR,3" downpipe rx7 store resonated midpipe, and RB dual tip exhaust. the ehxuast is just a tad too loud after going single, and am hoping to eliminate most of the smell as well. this should check both boxes off.

its rated to 1500 deg .... exhaust temps get alot higher than that

That is sustained 1500F and the cat is 3-4 feet from the exhaust ports. A typical twin cools the exhaust 150-200F just going through the turbos and then you still have 3 feet of pipe to radiate the heat off. I have an EGT sensor right after my turbos(I know not ideal for an EGT) and my top is 1550-1600F at WOT with extensive ceramic barrier coating of all my manifolds, turbos, and exhaust pipes. Add in the next 3 feet and it will definitely cool down below 1500F. I have had this cat now for a while and it is still intact as I checked it last week to change my exhaust gasket.
Mike