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05-02-2018, 05:26 PM | #45 | |
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Outlets, not always. If inlets are the last restriction in your intake air-flow, then they would provide faster spool-up; however, since they're on the uncompressed side of the turbo, they make absolutely no difference to the achievable pressure or peak power. From what I know about fluid dynamics - I tend to agree with you that inlets are nothing but marketing. This has been studied extensively in commercial air-conditioner design, and the tl;dr version it is a slightly smaller straight pipe presents only a tiny restriction in flow; but a poorly designed bend in a pipe makes a huge difference. The stock inlets are very squashed compared with aftermarket inlets, but the bends are similar - so it's very possible they provide little to no benefit. They especially provide no benefit if the restriction is elsewhere in the chain (eg. stock airbox or intercooler). ... All that said, it's a lot harder for a compressor to suck than it is to blow (which is why pressure pumps are always at the bottom of a hill, not at the top); and there's a noticeable increase in noise with aftermarket inlets, so you assume that means less restriction. But if it's just marketing or a real gain is entirely dependent on if the restriction in the inlets is the greatest restriction in the whole inlet system... And your experience pretty conclusively proves it's not. Outlets are a different story. Because your outlets connect the turbo to the intercooler - the air in them is the hottest and thus least dense of the entire compressed-side of the intake. (It's been heated by the turbo and is yet to be cooled by your intercooler). So, it makes sense to have the outlets larger in diameter than any of the plumbing on the cool side of the intercooler. All things being equal - the hotter, less dense air in the outlets means the pressure in the outlets (and thus on the compressor wheel of the turbos) is higher than the pressure in the chargepipe - where the boost sensor sits. So, when the wastegate is fully closed, increased flow in your outlets means less work for the turbo -- ie. higher peak performance and faster spool up. If you're limited by your boost limit - I though you're right. 17psi read at the boost sensor is 17psi going into the cylinders - so power won't change. But with a better intercooler and better outlets, 17psi at your boost gauge might mean 17psi at the turbo/outlets rather than (for example) 23psi in a more restricted system - meaning less work for the turbo. I did both inlets and outlets at the same time, and below is a picture of what the stock RHD outlets look like - so the gains I experienced may have been 100% caused by the outlets. Last edited by xQx; 02-13-2023 at 09:15 PM.. |
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05-03-2018, 08:32 AM | #46 | |
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Not on his 2012 with the N55
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2011 BMW 135i ///M-Sport, DCT
Bilstein B12 kit, Dinan camber plates, M3 front control arms, Whiteline poly RSFB, MHD Stage 1, cp-e Charge Pipe, H&R Front sway bar, BMW performance diffuser |
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05-03-2018, 08:57 AM | #47 | |
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On the other hand, lets assume you were previously limited to 17psi (32 psia) due to the turbo, and not fueling. Then you can increase your peak boost pressure while maintaining the same exhaust restriction. In this case, we use the same wastegate position as the stock case to get the 2.21 pressure ratio across the compressor. With the upgraded inlets, the peak boost pressure increases to 32.6 psia (17.6 psig). This allows you to inject slightly more fuel to get more power.
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2011 BMW 135i ///M-Sport, DCT
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05-03-2018, 12:10 PM | #48 |
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If I do nothing other than installing catless down pipes, will my car throw a CEL? And if so, what is the required step to rectify?
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05-03-2018, 01:56 PM | #49 | |
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2011 BMW 135i ///M-Sport, DCT
Bilstein B12 kit, Dinan camber plates, M3 front control arms, Whiteline poly RSFB, MHD Stage 1, cp-e Charge Pipe, H&R Front sway bar, BMW performance diffuser |
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05-03-2018, 04:15 PM | #50 | |
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05-04-2018, 12:06 AM | #51 | ||
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the DP fix isn't fantastic for your engine. |
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05-04-2018, 08:13 AM | #52 |
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Why is that? Doesn't it just plug into the downstream O2 sensor harness and simulate a working catalyst? Closed loop AFR control should be done using the upstream sensor so I wouldn't think that the DP fix would have any effect besides getting rid of the CEL...
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05-04-2018, 12:38 PM | #53 | |
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If I had an exhaust leak I didn't think it would show up as a DME code. No noticable leaking at the DP/Mid flanges so I'm kinda at a loss as to why it reeks so badly.....to the point where I considered putting my catted DP's back on. If it was a badly fitted VBand at the manifold it would be blatantly obvious, wouldn't it ?
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2008 E88 N54 135i / Cashmere Silver / Beige leather / VRSF catless DP's / BMW Performance Suspension / Whiteline inserts / Aluminum charge pipe and aftermarket BOV |
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05-04-2018, 01:51 PM | #54 | |
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TBH, any time you do DP's you should replace the fire rings. Also make sure you aren't melting the splash shield. |
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05-04-2018, 01:57 PM | #55 | |
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I took the splash shield off and haven't put it back on yet....
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05-04-2018, 03:51 PM | #56 |
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05-06-2018, 10:19 AM | #57 |
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Ah, I had to re-use the ones I had. Didn't know they were there before the install. My mazdaspeed didn't have one so I wasn't expecting it.
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05-06-2018, 03:19 PM | #58 | |
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I have 2 new ones sitting here for when I have to get in there to do some updating. |
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05-10-2018, 12:17 PM | #59 |
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Didn't see it mentioned, is just a chargepipe okay for MHD stage 2+ or should I be going to a BOV with the chargepipe? Starting to gather parts and wanted to know if the extra cost is needed or if the stock DV will be okay for that level. TIA
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05-11-2018, 05:07 AM | #60 | |
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You should be changing your charge pipe for a metal one anyway before tuning the car because the stock ones are prone to cracking under increased boost. When you order the new charge pipe is when you'll need to decide if you want a vent-to-atmosphere BOV or OEM style diverter valves. Using the OEM diverter valves will be absolutely fine for Stage 2+ but some people have reported that their OEM DVs leak a bit of boost. If you get a charge pipe with the fitting for DVs, the OEM units should be fine but if you have the money you may as well upgrade them to Forge diverter valves. The other option is obviously a BOV. Either will be fine for a Stage 2+ car. I personally run an Evolution Racewerks charge pipe with the factory diverter valves. I have disconnected the valves though so I still get the sound of a vent-to-atmosphere BOV but I still have the option to reconnect them if I ever get bored of the sound. You should put some small filters on the ends if you do this though because the OEM DVs are open at idle. |
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05-11-2018, 07:44 AM | #61 | ||
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05-11-2018, 09:09 AM | #63 |
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I considered this when I was making my charge pipe decision because I don't want the "pscchhh" every time my AT changes gear. Concerned about leaking boost using the stock DV's I ended up getting a Chinese tial knock-off for <$200 so I'll see how that goes with the sound. If I don't like it I'll dump it and get a charge pipe for DV's and use my stock ones. If they leak boost I guess I'll have to spring for the forge DV's.
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05-12-2018, 06:31 PM | #64 | |
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It won't make any BOV noise until you lift. Part of the auto advantage is the no loss of boost between shifts. Most have no idea I'm boosted until I lift at the end of the track, then heads get scratched ... that thing is turbo'd? Yeppers. |
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