[flash]

having tried a number of catalytic converters in search of the right one, i think i finally nailed it - i tried 100 cell, 200 cell, 300 cell, double bisquit, huge bisquit - you name it - NONE of them worked well - the smaller they were the more torque i lost - the bigger problem though was that NONE of them passed smog - i got by the last inspection by superheating the cat and barely passed - i mean i hit the maximum

however, i just had the factory cat welded back in - i left everything else alone - didn't remove any of the fun stuff - even ran it on 91 - it was so clean he had to run it a second time because he thought the sniffer had fallen out

at 15mph:
HC max is 85 - measured 2
CO max is .50 - measured .02
NO max is 695 - measured 1

at 25mph:
HC max is 50 - measured .02
CO max is .47 - measured .01
NO max is 717 - measured 1

on top of that, i now have more torque than before

WOOHOO!!!!!!!!!!!

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[rhudeboye]

<!--quoteo(post=70093:date=Apr 8 2009, 04:58 PM:name=flash)-->QUOTE (flash @ Apr 8 2009, 04:58 PM) <{POST_SNAPBACK}><!--quotec-->however, i just had the factory cat welded back in - i left everything else alone - didn't remove any of the fun stuff - even ran it on 91 - it was so clean he had to run it a second time because he thought the sniffer had fallen out<!--QuoteEnd--><!--QuoteEEnd-->

Remeber the Top Gear episode on our cars? He mentioned that Porsche claimed that the air coming out was cleaner then the air going in. Obvious hyperbole but the point seems to be true. These old cars have very low level emissions.

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[flash]

i have been truly amazed at the job they did on this - definitely done right

another added bonus was that it knocked down the sound a bit - it was just a touch louder than i wanted before, but i thought i was going to have to live with it, since anything more and i was losing power - now i think i have the best of both worlds

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[Johannvb]

Hey Flash,

Am I correct in assuming your exhaust setup is as follows?

• RS Barn Header
• Standard 968 Cat
• RS Barn Cat Back

I am asking, because I need to replace my exhaust (It's been patched too many times), but Shipping and Import costs are quite rough. So if I can save the weight and cost of the cat the RS Barn exhaust seems like a much more attractive option.

Thanks,
Johann

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[flash]

no - i do have the header and now the 968 OEM cat, however i have a prototype of a new cat-back system - it's not ready for production yet though, and won't be until at least late summer or fall

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[S_Cal968]

<i>***Bump...</i>
@Flash
So, has the header caused any issues during inspection or do you have rapport with the tester..? [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]
Does the RSB header bolt up to the OEM cat?
Do you have the RSB Stage II chip installed?

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[flash]

i have had no issues with the header - so far, they haven't cared at all at either of the places i went to - they have said it is because the O2 sensor has been in exactly the same location, and the tubing is essentially the same - it's not like going from a cast iron manifold to a header

it does not bolt up to the factory cat - i had to adapt it and weld it on

i have an RS Barn chip to match the things i have done - i'm a bit past stage 2 with some additional one-off mods

the results above were with that setup

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[wmuldowney]

<!--quoteo(post=74680:date=Jun 28 2009, 04:56 PM:name=flash)-->QUOTE (flash @ Jun 28 2009, 04:56 PM) <{POST_SNAPBACK}><!--quotec-->i have had no issues with the header - so far, they haven't cared at all at either of the places i went to - they have said it is because the O2 sensor has been in exactly the same location, and the tubing is essentially the same - it's not like going from a cast iron manifold to a header

it does not bolt up to the factory cat - i had to adapt it and weld it on

i have an RS Barn chip to match the things i have done - i'm a bit past stage 2 with some additional one-off mods

the results above were with that setup<!--QuoteEnd--><!--QuoteEEnd-->
Ok so whats the right answer?
I'm getting confused about the cat, I was considering the RSBARN hi flow cat but now thinking I should leave the factory unit in place. My car arrives Monday and I will be ordering the chip/header/hiflow/cat back. So should I just skip it now?

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[flash]

i'm in california where emissions standards are currently much more strict - the cat was a much bigger priority for me - i haven't had a chance to really run the car yet to see what other changes have occurred, or if i lost anything significant in horsepower up top - it doesn't feel like it, but i won't really know for a while

regardless though, this was not a direct fit by any stretch of the imagination - it took some doing to get it in there, and i'm not sure how easily the factory cat would fit with the rs barn cat-back

pete has done plenty of testing with the cat he uses - if emissions are not a concern where you are, i would run what he sends you

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[wmuldowney]

<!--quoteo(post=74686:date=Jun 29 2009, 05:53 AM:name=flash)-->QUOTE (flash @ Jun 29 2009, 05:53 AM) <{POST_SNAPBACK}><!--quotec-->i'm in california where emissions standards are currently much more strict - the cat was a much bigger priority for me - i haven't had a chance to really run the car yet to see what other changes have occurred, or if i lost anything significant in horsepower up top - it doesn't feel like it, but i won't really know for a while

regardless though, this was not a direct fit by any stretch of the imagination - it took some doing to get it in there, and i'm not sure how easily the factory cat would fit with the rs barn cat-back

pete has done plenty of testing with the cat he uses - if emissions are not a concern where you are, i would run what he sends you<!--QuoteEnd--><!--QuoteEEnd-->
Emissions are somewhat of an issue but not a deal-breaker. I can get anything to work and have the resources to get it done right. My concern is ultimately the loss/gains in power. If the RSBARN is not going to gain me anything, then I would rather spend the money on other items, for RSBARN of course [img]style_emoticons/<#EMO_DIR#>/rolleyes.gif[/img]

I sounds like both are good but it may depend on the modifications. I am not engineer but am I off base if I hypothesis the following:

With increased exhaust flow, more back-pressure needed, hence the stock cat works better

With stock exhaust flow, less back-pressure needed, hi-flow cat will gain more.

Just thinking out loud.

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[flash]

"back pressure" is a common misnomer - to be clear, back pressure is NEVER good - however, what is commonly mistaken for back pressure is gas velocity - slow it down too much and you lose power - this happens often with a system with too large of a pipe, or too little of an ability to properly scavenge the gasses - this happens often with a "free flow muffler" - larger passages result in slower flow - think of it like a straw - you get a stronger flow with a smaller one, though you get more volume with a large one - while often effective in increasing horsepower at the very top of the rpm range, volume is not the key to torque on a normally aspirated engine - velocity is

as to which cat to use, that depends on how strict the standards are - if you have a visual inspection that requires a number, then you should plan to install a cat accordingly - if all they do is look for a cat of any kind, then anything will work - if you have output testing, then you need to be concerned with that, and work on getting the factory cat installed

upon specific request, pete can ship the catback system with the flange loose, and the resonator as well - then you can have your muffler shop install the pieces where they fit - that is essentially what i did

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[gryphon]

<!--quoteo(post=70093:date=Apr 8 2009, 04:58 PM:name=flash)-->QUOTE (flash @ Apr 8 2009, 04:58 PM) <{POST_SNAPBACK}><!--quotec-->having tried a number of catalytic converters in search of the right one, i think i finally nailed it - i tried 100 cell, 200 cell, 300 cell, double bisquit, huge bisquit - you name it - NONE of them worked well - the smaller they were the more torque i lost - the bigger problem though was that NONE of them passed smog - i got by the last inspection by superheating the cat and barely passed - i mean i hit the maximum

however, i just had the factory cat welded back in - i left everything else alone - didn't remove any of the fun stuff - even ran it on 91 - it was so clean he had to run it a second time because he thought the sniffer had fallen out

at 15mph:
HC max is 85 - measured 2
CO max is .50 - measured .02
NO max is 695 - measured 1

at 25mph:
HC max is 50 - measured .02
CO max is .47 - measured .01
NO max is 717 - measured 1

on top of that, i now have more torque than before

WOOHOO!!!!!!!!!!!<!--QuoteEnd--><!--QuoteEEnd-->

All that work for nothing. You could have been watching football instead. LOL

Tom

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[flash]

lol - tell me about it - i've got well over $10k in exhaust systems - the good news is that i now have the best system there is for what my engine is doing - the bad news is that i didn't end up with a whole lot more juice than i started with, and a whole lot less cabbage

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[porsche]

Flash,

Did my super low mile Cat get "utilized?"

Porsche

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[flash]

yup - lol - it's on my car now

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[wmuldowney]

<!--quoteo(post=74717:date=Jun 29 2009, 04:03 PM:name=flash)-->QUOTE (flash @ Jun 29 2009, 04:03 PM) <{POST_SNAPBACK}><!--quotec-->yup - lol - it's on my car now<!--QuoteEnd--><!--QuoteEEnd-->

hey Flash, I got my car today!
I got to drive it almost a full mile before the first belt broke!
LOL

details to follow.

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[Kim]

Here in Canada we cannot buy an OEM cat or an aftermarket OEM lookalike from the US. They will not ship to here. An OEM cat from Germany costs almost $1300. That is why I went with an RS Barn header, cat and cat-back. Believe me, I really wanted to just buy a cat when mine cracked around the O2 sensor but is was near impossible without another job.

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