hi all
Does anyone have any knowladge of high flow cats? I was interested in putting an exhaust onto my rx-7 (when i find the right one)and ditching the cats but i didn\'t want a deafining noise from it. I was considering a high flo cat, what power differences are there between that and a straight pipe and does it cut out alot of noise? Is there anything else i missed?
Alternitivly i saw an apexi silencer although i dont know where it would go or how it would work. Anyone know?
heres the silencer.
http://www.rx7trix.com/store/customer/product.php?productid=71&cat=137&page=1
a cat is full of \'bricks\' so it probably doesnt give much silencing anyway (just generates back pressure)..
It will have some effect on noise, but not that much...
I have a cat-less exhaust on my Turbo II, and thats not deafening by any means (Its not a monster exhaust though, its about 2" after the split, and about 2-1/2" to 3" from the turbo to the Y-piece... ...its not that noisy, but sounds really nice and fruity with the window open!... ...inside the car is fine
One method of removing the cat (if you need it for MOT purposes) is to take the cat out, smash the bricks and cr@p out with a hammer and chisel, weld a straight tube through the centre of the cat box, and re-fit... ...looks like a cat, works like a cat replacement pipe!
b :)
Hi Rich,
I guess this is quite a topic when it comes to differing opinions.
You speak to some people they like a hiflow cat, you speak to others they don\'t like them and would advise on getting a midpipe. I think it does matter what hiflow cat you do install though as there are some that literally don\'t flow better than the stock one does. I have a friend in Denmark who just bought the knightsports metalit hiflow cat, I am waiting for him to install it so
he can advise on how good it is. I have spoken to a guy in Japan who races for re-amemiya, and he advises that the best hiflow cat in Japan for power is re-amemiya, well you say he would say that, but I have heard it on the grape vine from other sources as well. The problem with the re-amemiya one is that it\'s quite expensive. However he did advise me that panspeed make a hiflow cat and that the internals of it are actually re-amemiya though many people don\'t know this, so as far as flow is concerned it will flow exactly the same as re-amemiya one does, but this hiflow cat is cheaper to purchase. I personally want to keep my airpump, I don\'t want a lot of noise so I am getting the panspeed hiflow cat. If you get a midpipe you will get a lot of noise on a 3rd gen rx7 and you need a good boost controller as you will get loads of boost spikes too. The car will stink and will not pass an mot. Yes you get more power from a midpipe, but due to very little back pressure you lose a bit of bottom end grunt, but gain a lot more at top end.
It really is a personal thing a sto what you choose.
rgds
Brian Ellis
thanx guys
i think that there will be about a 10bhp difference with the high flo cat, cheers again guys.
You would get more than just 10bhp with a decent hiflow cat.
Also that apexi silencer is not what you think. It fits at the end of the apexi exhaust system because they are so loud, the make the exhaust noise a lot quieter, and you lose a fair amount of bhp putting one on.
rgds
Brian
ok, a catylitic converter is is a pollution control device. it is by no way a sound deadening device (muffler). basicaly it has porcelin internal core with fine holes running from the front of the cat to the back. the cat basicaly heats up from the exhaust and its job is to burn the unburnt fuel and some of the nasties that the motor produces (thats why there is an air blower that just pumps air into the exhaust, to help burn off the impurities. without air there is no fuel for the burning process).
i dont know the laws on cats in the uk. but to tamper with a cat ie punch out the porcelin and refit it to the car comes to a $10,000Aus fine. to not have it on a car that was originaly fitted with a cat is $2000Aus.
best to run a hi flo cat. and yes it is easy for the authorities to know if a cat is working on the car or not just by putting a "sniffer" up the exhaust (a sniffer is a gas sampling machine). environmental protection agencies use them here in australia. im guessing there would be an authority with the same cause over in the uk.
there not nearly as strict, not in scotland anyway. i dont even know if they carry the snifer devices with them. its ok to remove the cat on a pre 95 car as long as it passes the M.O.T without it(i think)
when i mentioned 10bhp i meant that you would have a 10 bhp loss over a straight through pipe when a high flo cat is fittted,so i\'d expect 25bhp gain with a high flo cat, down pipe and cat back.
(obviously ecu, fcd, ebc)
i was concerned about the noise levels as i would like to attract as little attention from the traffic police as possible, i think they\'re more concerned about noise than polloution .
:confused:
Brian, any idea when you are going to be getting your moggie? I\'m waiting to hear how you get on with yours before sorting out mine :)
Rich, I should be getting mine back with its rebuilt engine later in the month (I\'m hoping the cat didn\'t die when the engine did, but if so I may be going the hi-flo cat way sooner rather than later) so feel free to give me shout if you want to know how quiet/loud it is.
What you are best of doing (power wise) is scrap the Cat and get a Decat pipe with a Race Beat 3" exhaust, they are nice not to loud and still got a good hp gain with a distinctive sound.
Pip at WGT does a SS one.
Chris
Brian, ive got a metalit Hi flow cat on mine, so would be interested to know what sort of gains or differences your mate felt going from stock, to the metalit.
Be interesting to see if they make a big difference, having never driven an RX with a stock cat, ive no idea if they are good or not, althou Miguel does rate them very highly, so I would imagine they are a quality one.
Cheers
Hi Graham I\'ll let you know. He has not installed it yet. What power you get from them is dependant also on whether it\'s clogged or not. When new you\'ll see good power gains, but if in use for a few years with say a rich mixture setup, it may not flowing at it\'s optimum. Due to the fact a lot of high flow cats are smaller than the stock one they tend to not last as long.
rgds
Brian Ellis
Graham are you coming out to Dartford meet tonight should only be round the corner from you ??
rgds
Brian Ellis
Oh yeah, forgot about that, ill try get along, want to go bluewater anyway, so Id be right there.
Hopefully see you there later, you going Brian?
Yep I\'ll be there, it will be good to meet you for the first time.
rgds
Brian
Hi Brian
Didnt quite make it last night, did actually get to where the pub is, but really need someones mobile or something, as I did a flyby and saw it was quite busy, and didnt fancy approaching different groups asking them what they drive, lol.
Easy to get to thou, so ill know for next time, er, perhaps all members arriving at the pub should wear a certain colour flower, so we know, lol, except that would then be the "gays of FD meet", which I dont really want to go along to, so a phone number, or part of the pub to meet would be good.
If anyones meeting up round there apart from the 2nd Tuesday ones, let me know, be good to get a comparison of sounds and drives, as with most other cars, you kinda know if its going right, or sounds about spot on, but with fd\'s they are so thin on the ground you feel quite isolated when trying to determine what yours is like.
Take care
Graham
I have just gone from a high flow cat to a straight through midpipe. Noise is only very slightly louder. Problem with these high flow cats appears to be once you start tuning the car, this has an adverse effect on the cat and before you know it it gets clogged!
Once this happens you can forget about flow at the top end.
Regards
Max