My main cat has started to stink and I am thinking of replacing it with a Hi Flow cat. I am leaning towards the Random Tech unit, since it has an air tube (I am still running the Air Pump). First of all, is this a worthwhile purchase? I have a 3" downpipe, a 3" straight pipe exhaust, I/C, Intake, and PFC. Should I really expect any significant performance gains from adding a high flow cat? Anybody have any experience with Hi Flow Cats (bad or good)? Also - any problems with boost spike (as with a midpipe)?

Thanks,

Jim

 

Honestly, with a PFC, you're only likely to get a test or two out of a high-flow before it's burned up. You're better off just going with a resonated midpipe, and picking up a good factory cat to swap in at test time.

You will get a little more power with a hiFlow though if you do get it... and no spiking problems.

 

I have had a N-tech HF Cat and recently swtiched to a with a Resonated Mid-Pipe(RMP). The HF cat is a noticable improvement over the Stock cat. Better power and responsiveneess. The RMP is then again a noticable improvement over the HF cat.

Get the HF cat if you're worried about emissions. If being smog legal isn't an issue, i'd go with the RMP.

If you are worried about noise, don't be the Rx7store's RMP is quiet. It's the exhaust fumes that are a bit hard to take. I now a have daily driver now and when I take FD out, the fumes are pretty strong and very noticable, especially at stop lights and around town.

my .02

 

I've never had a midpipe but I just installed a HF cat...I can't tell you how much improvement over a stock cat cause mine was very clogged, but at the drag strip the other night I was shooting flames. My other exhaust mods are DP and Apexi single.

 

Thanks...I need it to be emissions legal, otherwise I'd go for the RMP.

Anyone have any before/after figures? Any direct experience with the Random Tech Cat?

- J

 

Tri-Points high flow cat is money, I passed CA emissions with it when I lived there and it flows pretty damn good. If you buy a good HF cat it isn't gonna burn up, I've had mine on for a year with similar mods as you and its still fine.

 

Now a HFcat you can get away with on a piggyback(M2/petitt) right? I know anything beyhond that, RMP or strait MP are too high-flow for the computer.

~Kris

 

Right now I can postulate that although you have freed up your exhaust you have also created some backpressure too, with the stock pipe and cat. I can't back that up with proof, but it seems logical. Because your basically going from 3" to 2 1/2" back to 3" and not keeping a consistent flow path. If your worried about a ticket than yeah go for a highflow cat. If your worried about emmissions w/ a midpipe you could always swap back your stock cat, specifically for that purpose. The highflow cat is going to be most beneficial with a good exhaust, as you mentioned you have a 3"dp and cat back, how bout the muffler aftermarket too?

I haven't done any testing myself but from what I am told highflow cat is a gain of about 4-5 hp over stock, and it allows you to run more boost over stock. But since you have the other mods I would say considerably more than that.

I can agree with everyone here your better of getting a midpipe, your mods will support one, mind you don't max out your injectors.

 

I'm a cheap bastard. I just piped the stock cat and put it back on, I don't have to smog my vehicles but if anyone ever checks, I have a cat.

 

You can get away with a HF on stock ecu just as long as you control the boost. MP your pushing it, but I've heard of people who have amazingly had no problems, so it's kind of a contradictory issue.

 

Generally, Hi-Flo cats are fine with piggy-back or rechipped ECUs (Pettit/M2/etc).

Some companies have recommended against using midpipes with their ECU's, like M2. Pettit has no restriction. However people have run midpipes using the M2 ECU without problems as long as they were able to control boost.

 

I've used HF cats on all my cars for years because a midpipe is too loud for daily driving and never had an issue with them clogging. You should see about 1/2 to 1 pound boost increase which of course will improve your hp and you'll save a few pounds as well

 

I have before after dyno runs on my site. They are good for 10hp. As for burning up, the PFC does use the air pump differently, which lowers the life of any cat. And naturally if you have tuning issues you can destroy the HF cat in just a few pulls as Pete suggested above. The combination of a HF cat and a PFC alone will not destroy a cat in a few pulls though. If that were true everybody would know about it.

 

Please tell me how a HF cat can get destroyed in just a few pulls on a dyno because of fuel issues I'm just curious.
Thanks,
Fritz

 

Go with the newer technology, better emmissions control and less back pressure than ceramic cats:

http://www.rpmoutlet.com/powercat.htm

With two of these on Corvettes making about 500 hp (Random Tech's version), they are only loosing about 10 HP with them. That is from a company here in Houston who are one of the top American GM products mod shop.

Ceramic cats are obsolete except for the poor!

 

I have the Random Tech hi-flow. Very happy with it. No noise issue. With race gas I run 17--18 lbs of boost, some backpressure but desireable to prevent overboosting and I pass emissions.

 

Nice find, man! I was talking to Carsound/Magnaflow a few months ago about a an aftermarket cat that would be appropriate for the rotary. Their advice was to use one with a metal core due to the high EGT's. However, they don't have a metal core offering.

I think a custom hi-flow might be in my future. I'm just curious how long it will survice with no air pump?

Sonny

 

Chuck,

Do you know anyone using that powercat on an FD? Sounds like a GREAT option, if it gets rid of the smell like a normal cat will. That plus a $50 ebay midpipe and some muffler shop to weld it, could be a cheap, great cat. I am just curious if it will last on an FD without airpump, and if it is as effective as a normal cat at getting rid of the smell, as that is my biggest concern.

 

FWIW, I don't remember having heard anyone say that their exhaust stank after they removed their cat. I've only heard that from people whose air pumps died or were removed. Are you sure your air pump is working properly? What kind of smell are we talking about? The "rotten egg" or sulphur smell comes from a dead or missing air pump with the cat still in place. If it's a fuel smell, that's just normal.

I had the random technology high flow cat, and I hated it. I used it for probably 40 miles, then took it off and sold it. Part of that may have been that I was non-sequential and bought it only to try to help control boost creep (even with a ported wastegate) and do "my thing for the environment" while I was at it. I eventually ended up with a Tri-Point stainless midpipe with a Borla XR-1 in it which solved my noise problem. The boost creep was eventually solved with a bleed valve, after I ditched my HKS EVC III.

 

I don't think the metallic substrate cats need air injection to help with the catalyzing process. More and more motorcycles are coming equipped with these types of cats, and there is no air pump/injection for them.

However, the temperature a cat (even one of new metallic cats) sees during operation is critical to its performance and longevity, so I'm not sure just slapping one on in the stock cat's location will work properly or last due to the FD's high exhaust temps. It may have to be moved a little further down the exhaust tract, but it's worth a look.

 

Jim, my cat got clogged, due to apex seal frags. So I puched it out, and basically had a straight though midpipe now 2.5" of course, and it stunk so bad, I hated it. I smelld when I went to work, and couldn't stand it anymore. So I bought a Bonez hiflow, and there is ZERO stink now, and yes, my airpump works just fine. It's the hydrocarbons thatn don't get burned off, due to there being no cat, that stink so bad. I'll take the HP loss and run a cat, if that is the only option, but this litte metal cat sounds like a great option, if it will work with an FD.

 

It's been a LONG time since you've been around a rotary without a cat then. The exhaust will make your eyes water and it sticks to your clothes like cigarette smoke.

I'm not talking about a *little* smell I'm talking about a LOT of smell.

 

yup, i run a midpipe and when the engine is running and you are near the back of the car good luck. it stinks and burns your eyes.

 

By the way Jeff, I couldn't wait for another GB so I bought a used Battery tray from a forum member. I have to say, that is one of the nicest mods I have done to my car. The tray is a very nice piece, and I fell like it open a ton of room for the Rad to vent. may just be my imagination, but I love it.

 

A few months.

Maybe you're just more sensitive than I am.