installation of the high flow cat = re map?

[michaelb]

Hi

I am thinking of changing my cat to a high quality high flow cat.  I was worried that if I de cat the mid pipe I will not be able to pass the MOT since I have a 96 RB Bathurst.

I have a HKS back box and recently I had an Apexi PFC installed with a basic map for my fd.  However, the boost on both turbos was lifted a bit.  The car now boosts to 0.92 with injectors duty reaching 88% on stock injectors.  Stock ic.

My questions are:

1) After installation of the high flow cat will I have to re map my car or will the base map be OK ?

2) Is there a missive difference in power loss if using high flow cat as oppose to de cat mid pipe. (My car being an import does not have a pre cat) ?

Regards,
Michaelb

[chrisBoid]

1) Personally I wouldn\'t risk it, but I am uber-catious.  I replaced my standard down-pipe and silenced mid-pipe babck-box combination with a dual flow downpipe, high flow cat and smaller diameter exhaust all in one go, so I got it remapped.

2) I lost a total of 15bhp at the wheels - not something I am going to notice (see here for details: - http://www.mazdarotaryclub.com/forums/showthread.php?t=10324).

[michaelb]

Hi Chris

Thanks for the substantial amount of info.  Car look great.  I am also not in favour in “over doing” the exterior although I am looking for a Knight Sport Spoiler now.

I also was thinking of getting Knight Sports Metalit High flow catalyst like yours.
I do have already big bore 3” HkS back box.  I guess my power loss maybe a touch less then yours due to the bigger back box, right?

What is a dual flow down pipe?  Is that much better then stock one, is it less restrictive?  I thought that jap cars had no pre cat in the down pipe?
All we had to do is change the mid pipe and back box to improve the flow?

Regards,
Michaelb

[chrisBoid]

Yes, the dual flow down pipe is basically less restrictive than the stock one.  I replaced it as I was doing most of the rest of the exhaust system anyway.  Plus trying to future proof if I make more changes.

I dropped from a 4" exit back box to a 3" Racing Beat back box at the same time.

[probedb]

There\'s also metallic substrate cats to think about which flow better than high flow cats as well. I have one of these tho not yet fitted.

[michaelb]

Hi Probedb

At the moment I am seriously undecided.  Either I get a de cat mid pipe and hope for the best when time arrives for MOT or get a high flow metalit cat

I simply can not decide, I sent an e-mail to Dragon some days ago to ask advice but have not heard since…probably too busy to reply to e-mails..

Regards,
Michaelb

[rx7veilside]

get a metallic substrate cat and weld it into a midpipe u wont notice any great power loss and shd be ok at mot time..the states is the place to get the met substrate cats

[probedb]

Michaelb, I was in the SMB Exhausts bulk buy on fd:uk a while back which is where i got mine from, andysmee (I think) also got the same and said his boost pattern went straight back to normal. They\'re more expensive I think?

[michaelb]

Michaelb, I was in the SMB Exhausts bulk buy on fd:uk a while back which is where i got mine from, andysmee (I think) also got the same and said his boost pattern went straight back to normal. They\'re more expensive I think?

Do you mean there was no bhp loss?

Regards,
Michaelb

[michaelb]

get a metallic substrate cat and weld it into a midpipe u wont notice any great power loss and shd be ok at mot time..the states is the place to get the met substrate cats

...there are very expensive here, I am sure states is cheaper...the welding would cost as well, looks like de cat is a cheaper option..

Regards,
Michaelb

[rx7veilside]

weld in wldnt be expensive