Decat pipe options
- Thread starter Pooltee
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engine killer
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i did a simple research last year on the decat for my 35i. the cheapest option probably from ebay but not easy to find the comment so i mainly looked at branded. from the most expensive Supersprint to probably one of the cheapest - VRSF. KWE looks very much like the original downpipe with the flexi section but cost much more than VRSF. didn't want to lost an arm or two so i went with VRSF as it has quite a good reputation. my mechanic told me it wasn't an easy install though.
noise-wise, i noticed they are a bit louder but not very significant. fuel consumption-wise, since my mechanic re-installed the lambda sensors to the secondary cats so it is about the same consumption as before if you keep you right foot feather-light.
noise-wise, i noticed they are a bit louder but not very significant. fuel consumption-wise, since my mechanic re-installed the lambda sensors to the secondary cats so it is about the same consumption as before if you keep you right foot feather-light.
A
Anonymous
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MACK said:
Don't you get a check engine error with these babies?
Pbondar said:
You will get a cat efficiency warning on the dash. It monitors the change in exhaust gasses over the primary cats so you need a tune to turn that warning off. You do need to keep the sensors in place though, removing or playing with them will screw the closed loop fuelling up.
Pbondar said:
I was hoping the remap would take care of that to be honest. I thought it was normal practice to delete this on a stage 2/3 tune but I'll clarify that before going ahead.
I've contacted a few remappers I'm considering for this, to see what mods are needed to remap to a certain stage of tune. This is where it got a bit confusing. I'm used to a scenario that goes something like this;
Stage 1 - Stock car hardware
Stage 2 - Induction kit, possibly a de-cat pipe or 100/200 CEL cats, sometimes even a full exhaust.
Stage 3 - Intercoolers and the like
Celtic offer three stages of tune for 20i but only one for the 28i. Which unsurprising, as the car's are for all intents and purposes identical, both ultimately end up in the same place at circa 280bhp and 290 lbft. But this is listed as a Stage 3 on the 20i and a Stage 1 on a 28i. I couldn't (still can't) get my head around was why are they also offering on the 20i a Stage 1 214bhp and a Stage 2 240bhp tune? Doesn't make any sense to me, surely if your going to remap a car you want the most bang for you buck. So I asked the question to Celtic "Do you recommend any hardware changes to go to Stage 3 on a 20i?" Just in case they considered you did, even though that wouldn't make any actual sense as they state you don't need them for the 28i. They responded with "All stages of tune are software based, your engine is massively de-tuned from the factory and this allows us to get huge power gains on standard components. The cost would be £325 all inclusive for one of our mobile team to come out to you when fully operational in the next few weeks hopefully." For me what they're actually saying here is they have three levels of Stage 1 tune for some reason, but I can't for the life of me see why you'd go with anything less than stage 3. I have to admit the idea of someone just turning up and remapping on the drive is sorely tempting, especially in the current climate, although of course it means I'll loose the before and after rolling road sessions.
For the last decade or so I've usually used Performance Torque in Wolverhampton for remapping. They list two stages of tune 260/280 bhp with the latter requiring an exhaust. They don't specify what bit of the exhaust on their website so I've asked them to clarify if they're talking full/cat back exhausts or just downpipes etc.
The whole thing does seem somewhat dis-jointed, with different tuners mapping to the same level but some requiring hardware changes and other not.
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Anonymous
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I covered the N20 in this post... https://z4-forum.com/forum/viewtopic.php?f=23&t=121232&p=1734136&hilit=pbondar#p1734136
Celtic are trying to create a value / performance proposition hence there logic of paying more for incremental greater power..despite the fact that most of the gains are easily achieved by a re-map only..
In my research things like de-cat / intercooler mods add about 10-15 bhp per mod on the N20..
The N20 is not intake restricted so new inlets do nothing bar increase noise..
Since in most people’s view for a car destined for long periods of trouble free operation the upper limit in most people’s minds rests around the 280bhp / 290 bhp area..
In reality no road going car owner is going to be able to discern say 280 bhp s/w only remap vs 295 s/w plus decat..
It doesn’t seem to be readily available but an auto box change to shift parameters would score more advantage..
IMHO it’s the end of the 80/20 design road..you;ve got mot of the gains for little effort / change...
You need to go to a 35i if you want a more elastic performance envelope...
There are lots of goodies for those unlike N20 especially in the Z4 engine bay format..
Many people have stretched the 35i performance without much ill effect..there isn’t a body of evidence to suggest you can go much beyond 300bhp on a N20 without tears..
Celtic are trying to create a value / performance proposition hence there logic of paying more for incremental greater power..despite the fact that most of the gains are easily achieved by a re-map only..
In my research things like de-cat / intercooler mods add about 10-15 bhp per mod on the N20..
The N20 is not intake restricted so new inlets do nothing bar increase noise..
Since in most people’s view for a car destined for long periods of trouble free operation the upper limit in most people’s minds rests around the 280bhp / 290 bhp area..
In reality no road going car owner is going to be able to discern say 280 bhp s/w only remap vs 295 s/w plus decat..
It doesn’t seem to be readily available but an auto box change to shift parameters would score more advantage..
IMHO it’s the end of the 80/20 design road..you;ve got mot of the gains for little effort / change...
You need to go to a 35i if you want a more elastic performance envelope...
There are lots of goodies for those unlike N20 especially in the Z4 engine bay format..
Many people have stretched the 35i performance without much ill effect..there isn’t a body of evidence to suggest you can go much beyond 300bhp on a N20 without tears..
Pbondar said:
For me the real benefit of the decat pipe is solely the throttle response, rather than noise or any gains in bhp/lbft, although obviously gains in bhp/torque are always nice.
Personally I would take 260bhp and better throttle response over 280bhp and a more sluggish one for example. I've had quite a few cars over the years with de-cats or sports cats and they really do make a huge difference to the throttle response. The only drawbacks are the noise, they can sound a bit too max power for my liking. Having had a look at the shape of the standard cat and comparing with the de-cat pipes out there like the one linked at the start of this thread. The de-cat pipes don't have any 90 degree angles like the standard cat, so I'd be expecting a bit of a smoother flow for the exhaust gases over a hollowed out standard cat. Hopefully this would equate to it being a little quieter as I can't say I'm too keen on it sounding like a scooby on start up as Twin Turbo reported with his. That said he did report it wasn't really any noisier than standard on the move.
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Anonymous
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MACK said:
Well on this one, I'll let you be the pioneer!
I will be of course very interested in the results
Pbondar said:MACK said:
Well on this one, I'll let you be the pioneer!
I will be of course very interested in the results
Well Ive took the plunge and ordered the UltimateBhp ebay jobbie linked at the start of this thread. I let you know how it goes. I have to admit I do have my doubts as to whether it will actually fit or not, but I've rolled the dice now.
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Anonymous
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MACK said:Pbondar said:MACK said:
Well on this one, I'll let you be the pioneer!
I will be of course very interested in the results
Well Ive took the plunge and ordered the UltimateBhp ebay jobbie linked at the start of this thread. I let you know how it goes. I have to admit I do have my doubts as to whether it will actually fit or not, but I've rolled the dice now.
Great stuff...love pioneers and respect your observations / judgements do await with interest your findings..
MACK said:Pooltee said:
Ill report back when I've got it fitted........ If it actually fits!
Ok,
Time to report back, its fitted, but it didn't exactly fit!
But I'll come back to that.In terms of the difference its made, well its noticeable.
1) Noise - there's a subtle growl from the front that's most noticeable from a cold start, it diminishes as the engine warms up a bit but is still there. It's not particularly intrusive though, it won't have you turning up the stereo at all to drowned it out. It's certainly nothing along the lines of sounding like a Subaru Impreza that Twin Turbo reported with his gutted OEM cat pipe. I put this down to its smooth flowing pipe design, rather than effectively something akin to a giant baked bean can welded into the exhaust as you get with a gutted OEM cat. On the move there's a subtle growl with a bit more pronounced turbo spooling, but nothing I would describe as being too Max Power. I'm generally not the sort to like noise for the sake of it. Yes I do have a modified backbox on my E85, which after some fettling I've got the sound to be a nice note/level. But that said I'm also someone who put the foam back in the sound generator because it was not a nice sound at all.
2) Performance - My car's still a standard 20i, with this pipe being fitted a head of remap. The reason I mention it is I expect the pipe to really come into its own once that remap has been installed. However that said its already made a noticeable difference, the throttle is much more responsive and the car feels like it picks up and goes a fair bit more. I don't want to over play this because this isn't a night and day difference, but I think a good way to describe it is it's similar to the difference in throttle response between comfort and sport. But then imagine there are two further incremental steps of throttle response beyond that, a kind of Sport ++ mode. I know the car's already have a Sport + mode but that does nothing to the throttle response over Sport. This really is like Comfort to Sport +2 more.
Ok, now the bad news, The Ultimate BHP downpipe bought off ebay (as linked at the start of this thread) wasn't a straight forward fit. I read that folks including Twin Turbo on here had had issues with decat pipes not fitting. So I deliberately targeted one that was specifically listed for the E89, avoiding the ones listed for F series this that and the other, as well as the E89. In its defence it looks well made and is the right shape and size for the E89.
The welding does seem to be well done and the downpipe mates up to the manifold well. It's just that one of the mounting brackets is welded in the wrong place and the rear of the pipe doesn't slip inside the existing exhaust centre pipe as it should because it's a few mm's to big.
Fortunately my mate's place took care of both these issues for me but I know a lot of garages would have just said "sorry mate it doesn't fit!" The biggest issue, the slightly oversized rear section of the pipe was remedied by leaving the downpipe alone and cutting a few inches off the centre pipe, then mating the two sections together with a exhaust sleeve/clamp.
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Anonymous
Guest
Great write up..pisser that when you're paying good money for the 'correct fitment' you're having to do a cut n shut to make it fit..
Given my lack of metal working skills and tools probably sends this to the bin unless we can find someone willing to do a batch?
Smartbear hello?
Given my lack of metal working skills and tools probably sends this to the bin unless we can find someone willing to do a batch?
Smartbear hello?