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01-22-2013, 08:29 PM | #67 | |
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Look at the first graph in this post for an easier comparison.
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01-22-2013, 08:52 PM | #68 | |
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Anyway, thanks again, bookmarked.
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01-22-2013, 10:05 PM | #69 | |
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01-23-2013, 12:25 AM | #70 | |||
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Bruce PS - What in God's name is linear power delivery, and how does it help with traction. |
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01-23-2013, 04:41 PM | #71 |
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Congrats! Enjoy it...it is a keeper!
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01-23-2013, 07:38 PM | #72 | |
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Power to the wheels is horse power * mechanical advantage. To get how much power the car is putting down, you need torque and gearing. That is science. Seriously?
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Last edited by MKE_M3; 01-23-2013 at 07:48 PM.. |
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01-24-2013, 12:19 AM | #73 | |
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Next, let me give you three examples of power and torque: 1. Stock M3 at around 100 MPH in third gear, 414 HP at 8300 rpm 2. Modified M3, 414 HP at 4150 RPM, at the same speed 3. Modified M3, 414 HP at 2075 RPM, same speed Obviously car two will need to be in a different gear so as to be at 4150 rpm, or for this example, the final drive will have to be half the stock final drive ratio, numerically speaking. Car three needs a quarter (numerically speaking) final drive. OK, so these three cars are cruising side-by-side at around 100 MPH. The stocker is capable of about 262 pound feet of torque at that point (per the formula), car two has to be making double that, and car three needs 1048 pound feet, again per the formula. Other than engines and gearing, the cars are identical, weigh the same, have similar rotational inertia at that point, blah blah blah. So everybody floors it, and what happens at that instant? The cars stay dead even is what happens. Granted, the stocker has to shift a split second later, but that's not important here. What IS important is that, with wildly different gearing, wildly different engine speeds, and wildly different torque production, the cars accelerate identically at that point. They do this because thay are making the same horsepower, and horsepower is the great shorthand in this context. As I've mentioned, you can mess about with torque at the drive wheels (and I did for years), but there's no need. Horsepower is the great simplifier. Yes. Let me ask again: What in God's name is linear power delivery, and how does it help with traction. Bruce |
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01-24-2013, 12:42 AM | #74 | |
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You are right in that horsepower IS the shorthand that generally summs up an engine's performance, but you can't just throw out gearing like it doesn't matter. The truth is, if the analogy is understood, we would also have to concede that in order for those engines to produce that torque at those rpm's and have that HP rating, they would all have to essentially shift very very soon. Why does gearing still matter? Gearing still matters because given the same exact car (6MT M3 vs DCT M3), you can have one car consistently win. Let's take for a moment that the 6MT was being driven by a machine that could reproduce accurate shifts every single time, with zero time between shifts. It would still lose to the DCT car due to the gearing and how the torque curve is then translated to the road. Any advantage in to the wheel torque of the shorter 6MT first gear is negated by the available traction, and then it's all on the DCT's favor.
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01-24-2013, 05:20 AM | #75 |
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There is no way in hell an S62 is nearly 100 lbs lighter than an s65. They are both aluminum V8s with roughly the same size block. Just throwing that out there.
One could build a bored/stroked 7000 RPM S65 with 400 hp, but that would be seen as a big waste of money and a step backward by most. Similarly one could build a destroked 8400 RPM S62 with 414 hp but that would be seen as a waste of resources as well. For racing applications, either engine is capable of 600hp+ once you equalize displacement and RPM. The S62 may have a higher deck (not sure) which would mean more displacement potential in theory. Both have an 98mm bore center like all BMW V8s. For a race series that does not allow altering the short block from stock, the S62 obviously has the advantage. |
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01-24-2013, 05:20 AM | #76 |
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There is no way in hell an S62 is nearly 100 lbs lighter than an s65. They are both aluminum V8s with roughly the same size block. Just putting that out there.
One could build a bored/stroked 7000 RPM S65 with 400 hp, but that would be seen as a big waste of money and a step backward by most. Similarly one could build a destroked 8400 RPM S62 with 414 hp but that would be seen as a waste of resources as well. For racing applications, either engine is capable of 600hp+ once you equalize displacement and RPM. The S62 may have a higher deck (not sure) which would mean more displacement potential in theory. Both have an 98mm bore center like all BMW V8s. For a race series that does not allow altering the short block from stock, the S62 obviously has the advantage. |
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01-24-2013, 05:33 AM | #77 | |
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S54 : 326lbs S62 : 348lbs S65 : 293lbs |
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01-24-2013, 05:47 AM | #78 | |
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That too seems suspect. Does the S62 use iron sleeves? I think it uses a spray on bore liner just like the S65. And the deck heights should be within 10mm. Aside from that difference, every other part in the engines should be within a couple percent weight-wise one way or the other. And both engine will have almost the same parts since they are both DOHC V8s with chain drive valvetrain and dual VANOS.
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01-24-2013, 08:24 AM | #79 |
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I have a turbo E36M3. In 4th gear on a Dynojet in SAE, it makes 170 lbs rwtq and 80 rwhp at 2500 rpm, 517 lbs and 400 rwhp at 4000 rpm, 440 lbs and 500 rwhp at 6000 rpm, and 360 lbs and 480 rwhp at the 7200 rpm redline. The tires are 255/40/17. I find that in 2nd and 3rd gears, where the torque multiplication is higher, the torque comes in so hard and fast that I often lose traction and that once I lose traction, I do not regain it (maybe because the car is going sideways and I back off. From 3300 to 4000, it gains about 225 lbs rwtq, and this is usually the window in which the traction disappears. I have often wondered whether a more gradual power torque delivery would help with traction, and have considered the idea of running a bigger turbo to shift power higher while also increasing top end power and torque. I view more "linear" as more "gradual."
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01-24-2013, 10:31 AM | #80 | |||
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And while we're at it, I wasn't talking about how peak power more or less sums up an engine's performance. I was specifically pointing out that, at any given speed, horsepower and weight dictates how a car will accelerate at that instant, and torque, gearing and rpm are completely immaterial. Those three examples demonstrate the point vey adequately. Quote:
In your example of auto vs stick M3s in a drag race, let me suggest that both cars are at a sprayed drag strip, with track temps at, say, 90 degrees or so. I'm suggesting that to get away from what I consider is beside the point in this general discussion, and stick to the main points, which are gearing and shift speeds - not traction. In that context, I'm thinking the stick car will have a minor advantage over a quarter mile (assumimg optimum launches for each vehicle), because it will launch harder, and will spend more time under power during the run because of the zero-length shifts. No biggie. Just an observation. Bruce PS - In general, gearing tends to be a little less important than folks think in terms of acceleration. If you change the M3's final drive from a 3.85 ratio to, say, a 4.11, the car will clearly be able to put more torque to the drive wheels at any given engine speed, but that torque will be delivered at a lower vehicle speed. The net effect is that the geared car will have the early advantage off the line, but when it shifts to second gear, the stocker will now have an advantage because it's still in first, and is now making more power (and of course more torque to the drive wheels) than the geared car. Then it has to shift and the geared car now has the edge...and so on. Because the geared car has the early advantage in each gear, there are ET implications, given perfect traction, but trap speeds won't change much, because average power over the quarter mile won't change much, and it's power and weight that tend to govern trap speeds. Last edited by bruce.augenstein@comcast.; 01-24-2013 at 10:40 AM.. |
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01-24-2013, 11:19 AM | #81 | |
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In my opinion, the tires are screaming (literally) for mercy because they are getting a stupendous amount of torque thrown at them, and the fact that the torque curve ramps up so quickly is not an issue. As an aside, street tires (even sticky ones) tend to "go away" pretty rapidly once they pass around a 10% slip rate - which is the point where they show best traction, by the way. At a thirty or forty percent slip rate, it's starting to feel as if you're driving on ice. Slicks don't peak, traction-wise, until they're slipping in the thirty to forty percent slip range, and fall off the traction curve way less rapidly. Bruce Edit: PS - Still waiting for MKE_M3's explanation. Last edited by bruce.augenstein@comcast.; 01-24-2013 at 11:28 AM.. |
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01-24-2013, 12:48 PM | #82 | |
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Now please tell us the proper way to express it rather than baiting someone into making you do the same. I suspect we need to be talking about linear throttle response and a lack of an aggressive tip-in, but I'm no expert.
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01-24-2013, 01:22 PM | #83 | |
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However, I genuinely want to know what MKE_M3 meant, and since's he's been present in the string, he can answer with more than single-word sarcasm. Assuming he meant "flat torque curve", then I particularly want to know how that improves traction. Buehler? Buehler? |
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01-24-2013, 02:11 PM | #84 | ||
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"The S62 uses weight-saving silicon-impregnated cylinder walls and has a specific casting with 94.0-mm cylinders. The stroke is mm to 89.0 mm. This results in a displacement of 4941 cc, or approximately 5 liters. "Above all, we wanted to create an abundant torque curve," says BMW M engineer Wolfgang Kreinhfner modestly - and if that is the goal, to paraphrase what the hot-rodders used to say, "there's no substitute for liters." The cylinder centers are 98.0 mm apart, leaving only 4 mm of block surface between cylinders. For effective sealing with this tight cylinder spacing, BMW M engineers developed new 3-layer steel head gaskets."
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01-24-2013, 02:16 PM | #85 |
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Why S85 (E60 M5 engine) is not discussed here? Yes it is a V10 but the same displacement as the E39 M5 engine (5L). It does fit into the e92 M3 engine as well. the S65 is very similar to S85 with 2 missing cylinders. I would prefer S85 over S65 in my M3 any day. ~25% higher hp and torque.
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01-24-2013, 02:31 PM | #86 | |
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I'll play. Everyone (sans yourself) talks about the "linear power delivery" of the M3. This exact phrase used by BMW themselves in their press release for the M3 CRT: "the high-revving unit provides the linear power delivery you expect from an M car." It is easy to control the amount of power to the wheels because the engine responds linearly to throttle response. A little bit of throttle, a little bit of power. A lot of throttle, a lot of power. Yet seemingly the ratio is constant; there seems to be a 1:1 ratio between your foot and how fast the car accelerates. This is different to a car with a large peak throughout its rev range. No power, no power, no power, POWER!!! The sudden inconsistency of power application to the wheels from one moment to the other overloads available traction and the car becomes difficult to control. The E9X is extremely easy to drive around town and in inclement weather due to this behavior. In fact to some it feels deceptively underpowered and underwhelming during test drives for this reason. Or another way: If you smoothly and linearly accelerate, you don't spin the tires. If you smoothly accelerate and then stomp the accelerator (non-linear), you spin the tires. Isn't this obvious? I enjoy reading your posts and find them educational. I hope you're not insulted that I think you're being purposely disingenuous -- I find it hard to believe you're not. I am hoping you will now translate my attempt into whatever the proper technical explanation may be.
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01-24-2013, 04:37 PM | #87 | |
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I assume you were bolding the part about the gaskets in an effort to suggest it can help account for the alleged weight difference? I am skeptical of that to say the least. I would need to see the shipping weight on those vs. the M3 head gaskets to be convinced. I highly doubt there is more than a pound or so difference between the two. What are M3 gaskets made of, I wonder? There's only 6mm between cylinders in the S65. I suppose that is 50% more than an S62, but then we are also talking about a significantly higher compression ratio too. |
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01-24-2013, 04:59 PM | #88 | |
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S54: 478 lbs, 217 kg S65: 445 lbs, 202 kg S62: 527 lbs, 239 kg S85: 529 lbs, 240 kg Good Read! http://www.europeancarweb.com/featur...e60_m5_engine/
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