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  1. #1
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    Downpipes- Catted vs. Catless

    So I thought I had done a good bit of research on the topic of catted vs. catless downpipes for the N54. In terms of power the various manufactures and tuners I talked to said that there would be a negligible (to me) difference in power. At higher boost levels than I plan to run they were talking about a 4-8whp difference. As a daily driver I was/am concerned about the smell of a fully catless exhaust. I assume it wouldn't bother me but the woman in my life and other passengers could be another story. I have no experience with a catless system so again going off of word of mouth it seems that the smell is very subjective. On the noise front I really enjoy my AMS system so I doubt that change would bother me. I thought I had boiled the difference down to primarily a price difference and to me it seemed that it would be worth hedging my bets by spending the extra money and going high flow catted.
    My problem is that recently I've been doubting my decision as it seems to me that I see more threads about people changing their hfc dp's out for fully catless. I think a couple people are just trying to pick up those last few hp, but more than a few seem to have some kind of tuning problem. Basically I am looking for everyone's thoughts on the issue from a tune perspective. It seems that all the common tunes have a quality catless downpipe fix of some sort and there are a lot of people that have problems getting their CEL to go away but that seems to usually be user error imho. In summary- which would be more conducive to a tuned vehicle?
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    Honestly,
    There is about a 1-5 hp difference. That's minimal. If you want to be responsible to other drivers and your passengers then cats are the way to go. If you are trying to squeeze as much hp as you possibly can, then go catless.
    Now, the throttle response does to improve with a catless. Slightly. But this is completely subjective really.
    Don't worry about what others are doing, just do your own thing.

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    i think it depends on your post DP exhaust. I hda catless and stock exhaust and noticed considerable hp/thottle response gain, and with no smell. it did add a slight rumble to the sound though, but nothing anyone besides me would notice. Now when i went full catless, my experience is different since i went with a brand that is VERY quiet, just barely more audible over stock, which is why i got it, sounds like a very tuned stock car, but the smell has come up on me a few times. it is noticable with the windows down when you do get a wif, but not like im anywhere near choking. as for drivers behind me, well, i don't know. I personally dont believe in global warming, so thats not a area for me to comment on. Of course, with other exhausts, their wxperience may differ considerably, but i hope this helped some.

    as for the DP fix, the add-on DP V3 from BMS works great, it did take a few days to get it dialed in, but once there your golden. I actually prefer it that was as opposed to just clearing the codes every so often.

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    I've been running catless DP's with stock exhaust. haven't noticed a smell sound is little more prominent but nothing major. BMS dp fix works great. Like LM said it takes a bit to dial but nothing to worry about.

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    Depending on where you live, the law and legal issues might be a concern. E.g. if they have visual checks each year, installing DPs twice a year, first stock DPs and then aftermarket DPs, might not be worth it for a couple of whp.

    The risk of getting fines for it should be small everywhere, I guess.

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    Thanks for the input guys. On the inspection side of things I'm good to go. My car is registered in North Dakota which has no type of inspection and I live in Maryland so I don't get messed with at all. Thanks for your experience on the smell LM. I'm going to have to poke around the local BMW CCA and see if I can take it in in person. I was really hoping I could get Terry or Shiv to chime in on which setup plays more nicely with tunes.
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    Click here to enlarge Originally Posted by SSDD Click here to enlarge
    Thanks for the input guys. On the inspection side of things I'm good to go. My car is registered in North Dakota which has no type of inspection and I live in Maryland so I don't get messed with at all. Thanks for your experience on the smell LM. I'm going to have to poke around the local BMW CCA and see if I can take it in in person. I was really hoping I could get Terry or Shiv to chime in on which setup plays more nicely with tunes.
    No reason you can't have one of them chime in, just yell. HEY TERRY!!

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    Click here to enlarge Originally Posted by SSDD Click here to enlarge
    Thanks for the input guys. On the inspection side of things I'm good to go. My car is registered in North Dakota which has no type of inspection and I live in Maryland so I don't get messed with at all. Thanks for your experience on the smell LM. I'm going to have to poke around the local BMW CCA and see if I can take it in in person. I was really hoping I could get Terry or Shiv to chime in on which setup plays more nicely with tunes.
    not sure we understand your question of plays nicely with tunes? bms fix keeps the light off permanently, and the other, correct me if im wrong, just clears the code as it comes back, *or* it just never lets the car finish its testing cycle. I cant remember which or if its the same since i was reading info on both.

    i do know that some states, do snif tests and some dont (NJ does not) , but most do the obdII test (NJ does), and if its not finished the cycle it wont pass anyway, but since thats a fine line anyway, it depends more on your states inspection.

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    Click here to enlarge Originally Posted by SSDD Click here to enlarge
    Thanks for the input guys. On the inspection side of things I'm good to go. My car is registered in North Dakota which has no type of inspection and I live in Maryland so I don't get messed with at all. Thanks for your experience on the smell LM. I'm going to have to poke around the local BMW CCA and see if I can take it in in person. I was really hoping I could get Terry or Shiv to chime in on which setup plays more nicely with tunes.
    Terry is losing his touch Click here to enlarge

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    1 out of 1 members liked this post. Yes Reputation No
    First off let me say thank you again for your input LM. This is my first go at really modifying a vehicle and the vast majority of my information comes from reading about your (and people like you) experiences. I appreciate every bit of the trail blazing information.
    Of course I can't find it now but throughout my reading I believe I have come a accross a few people that knew what they were doing that were changing out their HFC dp's due to hiccup's with their preferred tune. Again I only know what I can research but I thought there was more to the O2 sensors than just a CEL. I thought the DME and/or tune made adjustments based on the info the O2 sensors picked up and the various fix methods can/do actually affect the info that those adjustments are made off of.
    Click here to enlarge

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    yea, your looking for a more technical explanation then i can offer. the only parts im sure about are what I already mentioned. If you need more info, im sure these questions have been asked before Click here to enlarge

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    Alright so apparently my concerns were totally unbiased. After emailing Vishnu and Terry the consensus is that catted or catless has no effect on your tune. Apparently the only difference from their side of things are the issues we already discussed. I still haven't come across the threads I had seen with people going from HFC to catless that led me to my false conclusions. I did see that Mr. 5 had made the change years ago but I think he was just looking for the couple more hp.
    In my case I think I'm going to try going catless first. I figure I'll see what the downsides are like (smell, noise, etc) and see how I like it. Worst case scenario I should be able to sell the catless pipes for almost no loss other than my install labor and at least I won't have to wonder anymore.
    On that note I'm looking for opinions on going with thermal or ceramic coatings. The idea makes sense to me but I haven't seen any data to back it up so it could just be something to add to the price for people like me.
    Last edited by SSDD; 07-16-2010 at 02:54 AM.
    Click here to enlarge

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    Click here to enlarge Originally Posted by SSDD Click here to enlarge
    Alright so apparently my concerns were totally unbiased. After emailing Vishnu and Terry the consensus is that catted or catless has no effect on your tune. Apparently the only difference from their side of things are the issues we already discussed. I still haven't come across the threads I had seen with people going from HFC to catless that led me to my false conclusions. I did see that Mr. 5 had made the change years ago but I think he was just looking for the couple more hp.
    In my case I think I'm going to try going catless first. I figure I'll see what the downsides are like (smell, noise, etc) and see how I like it. Worse case scenario I should be able to sell the catless pipes for almost no loss other than my install labor and at least I won't have to wonder anymore.
    On that note I'm looking for opinions on going with thermal or ceramic coatings. The idea makes sense to me but I haven't seen any data to back it up so it could just be something to add to the price for people like me.
    Great post, thanks.

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    get the coating, not only for any possible "performance" gain, but the longevity of the material itself

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    I thought it was just the $200 dp's that had the issues? Also, anyone have any comments on Macht Schnell vs AR (performance, fitment, etc)?

    On the coating front I know I've read about people saying there were downsides but I can't find any links at the moment other than people just saying it's a waste of money. If anyone finds anything please throw it up here.

    http://www.automobilesreview.com/aut...impreza/11194/
    Click here to enlarge

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    Click here to enlarge Originally Posted by SSDD Click here to enlarge
    I thought it was just the $200 dp's that had the issues? Also, anyone have any comments on Macht Schnell vs AR (performance, fitment, etc)?

    On the coating front I know I've read about people saying there were downsides but I can't find any links at the moment other than people just saying it's a waste of money. If anyone finds anything please throw it up here.

    http://www.automobilesreview.com/aut...impreza/11194/
    I would take Macht Schnell over AR just because the guys at EAS aren't douchebags.

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    I heard coating the down-pipes is bad because the additional retained heat in the downpipe will cause less energy drive across the turbine from the manifold. Basically you want the manifold/turbo - downpipe temperature split to be higher so that exhaust gases want to travel through faster. Energy is always trying to equalize and this is all that is happening.

    The benefit of the coated downpipe however is the increased longevity and resistance to corrosion.

    I think it would be better to have a turbo blanket and coated/heat-shielded manifold and leave the downpipes alone.

    I'm no expert though, I would contact Garrett or Borg Warner or some high-class turbo shop and get their opinion.
    Last edited by fundahl; 07-16-2010 at 03:14 PM.

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    valid points as well gents.. OP, might wanna do some more research then or wait for someone a bit more knowledgable to chime in

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    After doing a bunch more reading there are a Ton of opinions, professional and otherwise, as well as some 'data' on both sides. Again I think I've arrived at a compromise- heat wrap. Apparently there are large variations in the thermal insulation properties of the different coatings. It seems that most are aimed at just protecting the metal from the elements. I haven't seen anyone with a problem with the CPE/Macht Schnell/AR pipes so I'm not really at it for that purpose. Also, it sounded like although most coatings talked about or let people just assume that they were inside and out they were actually applied with an airbrush and thus only slightly inside of curvy and somewhat lengthy pipes like ours.
    The heat wraps seem very reasonably priced and I can easily apply and remove it. I should be able to try with and without, and some data logging, temp gun measurements, etc to come to a conclusion.
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    Never dealt with Macht Schnell. They are probably great. I can say that AR has gone out of their way to help me with several issues that AE was having (making sure that I get the HFC exhaust that I ordered -Before- AE decided to do away with offereing it). Andrew has always been busy when I've contacted him, but, he does get back to me and has never had the "tough $#@!" attitude towards me. At any rate, felt I should chime in because I've had an experience with him as a consumer. BTW, his CL downpipes fit awesome, per the guy on this forum that helped me install them. Everyone can cop an attitude and maybe he hasn't acted well on this forum. He has been stand up with making sure I get what I need with AE though.

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