High flow cat

RX7 FD EFINI

New member
Can someone recommend a good high flow cat and where I can buy in the UK to avoid import duties. I've done some searching but they seem hard to come by.

Thanks
 

terry06

Active member
I have an Apexi that came with the car when imported. Seems like a good bit of kit and the car made decent power with it. It doesn't do much in regards to emissions though so kind of defeats the point of having a cat...

Not sure if they're available off the shelf over here but they can be had from RHD
 

RX7 FD EFINI

New member
Only reason I want one is to create more restriction in the exhaust so I'm not over boosting on the stock ecu. Im currently building the car back up to stock, it's is straight piped currently by the previous owner probably why the engine went pop.
 

cib24

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Someone will be selling a used high flow cat if you look around. Ask @Jit since he usually has stock of a lot of things or knows who may have what.

I have been running a high flow cat for 4 years since my OEM cat honeycomb began crumbling. The high flow cat has been operationally perfect for me the entire time it's been on my car. I bought it used and have had it on my car for about 20,000 miles, 8 or 9 track days, etc. The metallic honeycomb is still perfect and it hasn't prevented me from making any power at all. I don't think they are as much of a restriction below about 450-500hp as everyone would want you to believe. The other benefit is the car doesn't smell like absolute shit, cause headaches and will hopefully keep lung cancer away from me some day.

Having said all of that, my high flow cat doesn't pass the MOT. It gets very close but I fail on CO2 just barely unless the map is leaned the hell out and the cat is very very hot. So, keep that in mind if you try to buy a JDM high flow cat. Another route would be to buy a universal high flow cat and have an exhaust shop make a mid-pipe to fit your car.
 

RX7 FD EFINI

New member
Not worried about mot that's fine. All im looking for is something to restrict flow and isn't the stock cat.
I'll be running it with an upgraded back box, not something massive though. Round about the racing beat size I would say.
 

cib24

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Are you using the stock downpipe?

RE-Amemiya high flow unit. It's like every other high flow one really. I would guess it's about 150-200 CPSI. I bought it used from another member 4 years ago so not sure how many miles in addition to my 20,000 are on it.
 

RX7 FD EFINI

New member
No, it's a custom one.
I see sard make one for a decent price. I'll probably go for that if i can't get hold of a good used one.
Also are you aware of anyone who makes a standard replacement cat, not the high flow one.
 

terry06

Active member
If on the stock ecu, even a high flow cat will likely cause you issues.
I'll have to keep and eye on this now I'm back running stock ECU as I have the Apexi cat and an AutoExe cat back. Still running the standard downpipe so hoping it will be ok.

Hard to keep an eye on boost with standard mm/hg gauge so I'm using the old boost controller as a boost gauge (boost control side not connected). Not sure how accurate that is though
 

terry06

Active member
As an update to my previous post on this topic I can confirm @Ceylon is correct as usual. I have noticed that my car appears to be over boosting now that I can push it after the run in period. Stock ECU/boost control, stock airbox with K&N filter, stock downpipe, Apexi cat, AutoExe catback.

I've seen ~93kPa a couple of times on the "boost gauge". It seems to read slightly higher than the standard gauge would suggest, although it is quite hard to accurately read that. I have had one occasion where I believe I hit boost cut (103kPa peak recorded) so I avoid pushing the car hard now as I don't want to ruin my new engine!

As a temporary work around I've been thinking of fitting a restrictor plate to the exhaust in an attempt to prevent the boost creep like the Supra guys do. At least until I can upgrade the fueling/ECU to deal with higher than standard boost pressures anyway.

Anyone else fitted a restrictor plate/is it worth it/what size orifice did you use?
 

GrantFD

Active member
As an update to my previous post on this topic I can confirm @Ceylon is correct as usual. I have noticed that my car appears to be over boosting now that I can push it after the run in period. Stock ECU/boost control, stock airbox with K&N filter, stock downpipe, Apexi cat, AutoExe catback.

I've seen ~93kPa a couple of times on the "boost gauge". It seems to read slightly higher than the standard gauge would suggest, although it is quite hard to accurately read that. I have had one occasion where I believe I hit boost cut (103kPa peak recorded) so I avoid pushing the car hard now as I don't want to ruin my new engine!

As a temporary work around I've been thinking of fitting a restrictor plate to the exhaust in an attempt to prevent the boost creep like the Supra guys do. At least until I can upgrade the fueling/ECU to deal with higher than standard boost pressures anyway.

Anyone else fitted a restrictor plate/is it worth it/what size orifice did you use?
I've still got my old CAT in the shed, you're welcome to put it on your car if you wanted to?

Although it sounds like the inside is starting to crumble.. but should still help šŸ‘šŸ½
 

jdmr_neil

Well-known member
Only reason I want one is to create more restriction in the exhaust so I'm not over boosting on the stock ecu. Im currently building the car back up to stock, it's is straight piped currently by the previous owner probably why the engine went pop.
Mate, gimme your address and ill send you a 3" restrictor plate which will do that for postage.

Iirc it reduces down to 2.5" so sorts any creep out, i used it years ago with a a full system on a oem ecu.
 
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terry06

Active member
If you want it gimme a shout and ill measure it exactly and send you a pic. Im not bothered about any money for it as it was gonna get binned anyway
If you wouldn't mind measuring it I'd be interested to know the size of the hole. I've cut out the outside shape using a gasket as a template but I'm not sure how small to make the central hole, don't want to restrict the flow too much.
 

cib24

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Roy
Thanks @jdmr_neil (y)
It's smaller than I was expecting but I will give it a go
It's what you need. You will still be making 10-15hp more than standard with this restrictor plate and your other mods. It will be beneficial for you and help your car stay in the safe zone.