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02-09-2009, 11:23 AM | #45 |
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yeah, usually for the N54, people stay around 14-15 psi (5-6psi over stock) if they're not going for crazy horsepower records.
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02-09-2009, 05:06 PM | #47 |
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02-09-2009, 05:10 PM | #48 |
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Terry had the boost at 18lbs to set a new record on the dyno and see if the turbos could hold that much boost... regular people will almost never see that type of boost...
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02-09-2009, 05:20 PM | #49 | |
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(his wouldn't be a good example to use for longterm reliability as he regularly uses a non public turbo melter map at the drag strip that is tuned at 16.5psi) |
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02-09-2009, 05:40 PM | #50 | |
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02-09-2009, 07:14 PM | #51 | |
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Last edited by Nixon; 08-10-2009 at 03:08 PM.. |
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02-09-2009, 10:58 PM | #52 | |
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Here is something to consider from BMW's own technical papers on the stock N54 engine: "At full load the engine operates at an overload of 0.8 bar" 0.8 bar is equivalent to 11.6 psi of boost. I know the current stock boost peak is 9 psi, but the point is that it would appear that the N54 was designed to handle 11.6. So one can reasonable conclude that companies like Dinan, Vishnu or BMS are not really pushing things too far with boost levels of 13-15 psi on their regular customer maps. The experimental race maps are a different story....but those are not intended for public use. |
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02-10-2009, 09:28 AM | #54 | |
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This is one of my favorites.
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Mods list got too long, lets just say more than enough.
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02-10-2009, 10:09 AM | #55 |
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the turbos will last longer if the psi is lower. plus, if it made 3 more psi stock, the M3 would look WAY overpriced...
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02-10-2009, 10:29 AM | #56 | |
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Am I reading this differently or are you numbers off? If it says it operates at up to .8bar over boost, and factory boost is 7-8 psi, .8 is equal to 11.6 psi, so wouldnt that mean at times it is running at 18.6-19.6psi? |
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02-10-2009, 10:33 AM | #57 | |
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They're talking about boost above normal atmospheric pressure. It's a translation issue with the terminology I think. |
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02-10-2009, 10:36 AM | #58 |
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I doesn't matter as what was posted is fairly irrelevant. We're talking about turbo failure, not pressure in the intake manifold.
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02-10-2009, 12:09 PM | #59 |
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This is very relevant. When BMW states that the turbos are allowed to boost up to 11.6 lbs. stock, It makes us realize that 13-14 lbs. of boost is not that far off from what BMW had them manufactured to handle.
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02-12-2009, 08:04 PM | #60 | |
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I don't think it's a stretch to think that the turbo lag issues which surfaced after the launch of the N54 have a lot to do with BMW de-tuning the engine from it's original specifications. Keeping the wastegates open at idle resulted in a less responsive engine off the line and is well documented in these forums. So it does not surprise me that they keep peak boost a little lower as well. Maybe as others have speculated this was in part not to piss off the M3 market. But at some point before all this took effect, someone at BMW designed the engine for 0.8 bars of ATMOSPHERIC overpressure (not over stock boost) and they published this statistic in their technical papers. Sorry but I didn't publish this....BMW did. I do have to agree though that at some point you are starting to introduce the potential for serious problems if turbos are extended way beyond their efficiency range, but it's going to be compressor rpm that does them in. As some have pointed out already, in the VW/Audi and Subby world, boost pressures north of 20 psi are the norm. That's NOT a lot of air pressure! The standard household water pressure in your faucets is around 30 to 40 psi. Do you lose sleep over your toilets blowing up? I think the two main enemies of running a tune are execessive compressor rpm and engine detonation/pre-ignition due to too much timing for the boost levels. It's probably more accurate to debate those parameters than to blindly say that 16 psi of boost is unsafe because it's double that of stock. The peak boost chosen by BMW is undoubtedly a compromise between creating a smooth power curve and achieving fleet fuel efficiency and emissions compliance targets. Tuners don't have to worry about these factors and can exploit the headroom available within design specifications to maximize power delivery for more performance. Last edited by dcafs; 02-12-2009 at 08:27 PM.. |
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02-12-2009, 09:27 PM | #61 |
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seriously folks...I am not stopping until you can hear that kind of turbo spool coming from under my hood.
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02-13-2009, 12:04 AM | #62 |
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you are understanding it wrong. it is saying that the turbos can run .8bar (11.6psi) at full load so people that are running that psi or 1-2 more think they feel safe. you don't add the factory boost plus what its running under full load.
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04-16-2018, 01:44 AM | #63 |
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