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05-23-2013, 11:50 PM | #133 | |
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As many of us have discussed prior, the numbers of 395 ft lb, approximately 415 hp and anywhere from a 7500-8000 rpm redline just are not consistent and possible together. Also BMW seems to have a decent track record (335i, 1M, F10 M5, etc.) of underrating. This M4 will be one and the same in that regard. I think they may rate the car around 425 hp but the likely actual crank hp will be in the range of 440-460. If these rumors on redline are true, and they do sound reasonable (and I always have a pretty high degree of trust in claims backed by southlight), I would guess a 7700-7800 rpm redline. It surely will not be ≥8000 rpm. No doubt about it, the car will feel a bit flat above 6000 rpm compared to the current engine. However, flat with 10% more hp is not so terrible. Sure I'd prefer to not have this engine characteristic given such a choice. Lastly I am 100% confident that this car despite the shape of its torque and power curves when above about 6000 rpm the former is falling fast and latter table top flat, will still only achieve maximum acceleration when shifted precisely at redline. Generally speaking, as long as the power curve does not actually fall and as long as the gear choices are reasonable, shifting at redline is required for maximum acceleration. If anyone want to continue to doubt this I would be willing to prove it either with a detailed Excel chart showing wheel force vs. speed in all gears or with a physics based acceleration simulation. Both require a resonable assumption on the torque or power curve vs. rpm and I would use something right along the lines of the one from HMR.
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05-24-2013, 03:56 AM | #134 | |
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It may be true that if you or I started with an off-the-shelf N55 and began swapping turbos and playing with the ECU, we are unable get max power at ~7900 RPM. But then that isn't what BMW is going to do. None of us know just what is in store for the S55 yet. All we know is there will be multiple turbochargers. |
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05-24-2013, 07:53 AM | #135 | |
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Of course engine which have nice almost flat top end power curve is more easily to drive than engine which redline is 6000rpm and power rises very fast---> hard to find balance whit grip. Last edited by Tåst; 05-24-2013 at 08:01 AM.. |
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05-24-2013, 07:55 AM | #136 | |
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What will be interresting is that, with such a flat power band, there should not be any drop in acceleration when shifting from one gear to another. Essentially having "450hp" available at any road speed. Further enhanced by the seamless shifts of DCT, the acceleration curve should be very smooth, progressively decreasing with road speed. As a comparison, with the peakier power curve of the S65, the wheel torque significantly drops with each gear change, yielding a "staircase" acceleration curve. Last edited by CanAutM3; 05-24-2013 at 08:48 AM.. |
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05-24-2013, 09:18 AM | #137 | |
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Numbers are just numbers without the context of the whole picture. FI engines can be sized to run to high RPM, just depends on the configuration of the turbos, etc. The S55 will have at least two turbos, and who knows what kind of technology behind them. Since BMW is moving hard toward single twin scroll turbos on their I6's, this is a significant departure and can't be overlooked in light of the "close to 8,000 RPM redline" claim. Most turbo engines on the road are low redline simply because they can be, and because it's cheaper to do so. Resources are not blown simply to make a number in Top Trumps. If a car meets targets for performance and economy, then a redline point is pretty pointless. Let's face it. 99% of drivers out there don't rev their car hard on purpose. |
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05-24-2013, 10:01 AM | #138 | |
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With BMW going to single turbos on most of their I6 engines, I can't imagine a tri-turbo engine with electric motor. I would more envision this motor with one conventional twin scroll turbo, and one with this electric assist. It would make sense for a small twin scroll to be paired with a larger electric assist turbo, as that would minimize lag all the way around. The tri-turbo setup as shown in the monster diesel is to get around issues that would be solved by having the electric motor. Here's hoping...although warranty might be nightmarish! |
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05-24-2013, 10:10 AM | #139 | |
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The M3 has been a 4, 6, 6, 8 and now back to a 6. So 6 is certainly the norm for the M3, but not the rule. And if you want to stay "pure" you should be saying it should be a 4. The M5 has been a 6, 8, 10 and now back to 8. Don't forget, BMW also said "no turbo M cars, no AWD M Cars, no M SUV's and no automatic transmission M Cars" as well. Times change, technology changes and so does philosophy, etc. I am no luddite, but the S65 is an amazing engine with a lot of soul, and while I understand why BMW is making the move they are, it doesn't mean that I don't bemoan the loss of one of the greatest V8's ever. |
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05-24-2013, 10:13 AM | #140 | |
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05-24-2013, 10:25 AM | #141 | |
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05-24-2013, 11:25 AM | #142 | |
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So BMW isn't really a renowned maker of V8's. They have made two greats, one good, the rest are meh. Where as they have a much more consistent record with their inline 6's. I would have to agree with the statement that BMW has never really been about V8's. |
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05-24-2013, 12:40 PM | #143 | |
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Agreed, like I said before. I think we are going to see something new. Possibly something along the lines of an electric assist to defeat lag in conjunction with a turbo sized for top end breathing.... |
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05-24-2013, 12:54 PM | #144 |
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I dunno, I've owned a handful of turbo cars and driven many more over the last 25 years and none have built linear power as rpms raises towards the redline. Is it possible? Probably but can anyone here say that they have driven such a car and point us to one?
Also, keep in mind why BMW is going FI and the thirst of an engine running peak boost at 8k rpm... Last edited by solstice; 05-24-2013 at 01:11 PM.. |
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05-24-2013, 01:14 PM | #145 | |
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05-24-2013, 04:09 PM | #147 | ||
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05-24-2013, 04:12 PM | #148 | |
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05-24-2013, 04:46 PM | #149 | |
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SMG SMG 2 DCT Special Diffs Double Vanos ...... etc. |
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05-24-2013, 04:48 PM | #150 | |
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"We will surprise you with this car." - BMW M (forgot the specific person's name) Based on how much skepticism and doubt exists even as more and more information comes forth, I fully expect that it will indeed surprise a lot of us. Heck, I will admit to being caught off guard if the weight truly ends up 3300 lbs or less. |
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05-24-2013, 04:53 PM | #151 | |
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http://www.ebay.com/itm/HorsepowerFr...-/140090291662 And try it out yourself. Maybe that would help explain? I kid. But only sort of. |
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05-24-2013, 05:08 PM | #152 | |
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I think the 'problem' with US-spec STIs is they come with a 2.5 liter motor that redlines around 7,000 while the JDM STI has a 2.0 liter that revs out to 8,000. I think they may be using the same gearing on both cars, that would explain why the US cars feel like they're constantly running into their rev limiter. Last edited by Remonster; 05-24-2013 at 05:13 PM.. |
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05-24-2013, 05:21 PM | #153 | ||
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05-24-2013, 05:27 PM | #154 | |
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How about a friendly wager then? Shall we say the winner donates an agreed upon sum to a worth charity in the forum's name?
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