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08-14-2014, 01:50 AM | #23 | |
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08-14-2014, 02:18 AM | #24 |
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The champ has arrived with opening statements! I'm not sure they'll broadcast this trial on cnn, but I'm anxious to follow the action. I'm not sure swamp is on the right side of this argument, but he's the best litigator on this forum and my money is on him to pull out a stunning comeback victory of attrition nonetheless. 12 round split decision for swamp.
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08-14-2014, 04:08 AM | #26 | |
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For trap speed it's seem more logical that errors are in the lower trap speed recordings due to the driver being part of the formula. Here you have two out of four "professional" runs, two I assume independent runs at different facilities by different sources recording 119 mph trap speed. I would think this is closer to where the cars power capability lies than the 114 runs and that we will see well executed trap speeds gathering more round 120 mph than 114 mph. |
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08-14-2014, 05:09 AM | #27 | |
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My questions/comments are:
Last edited by Boss330; 08-14-2014 at 05:59 AM.. |
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08-14-2014, 05:39 AM | #28 | |
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On a 1/4mile run in the F8x, every time you shift gear the revs drop to around 5500rpm, but you still have 425hp on tap from the engine. In a NA engine like the S65 (or any engine with a traditional "non plateau" power curve) you have max power at your shiftpoint/redline, but when you change gear and drop down in the rev range you don't start with max power. You might be 50hp down from what you had at redline in the previous gear... What matters here is the average hp in each gear. In the S55 that is 425hp (because we are always at max power under acceleration), but in the S65 it might be as "low" as 380-390hp (because, in each gear, we start off at a low hp level and end up at max hp only at redline). In effect this means that the S55 performs like a 420whp engine (with a traditional power curve) since it probably has the same average HP in each gear as a more powerful engine with a "normal" hp curve has. For instance if we just use as an example a engine that in each gear starts with 380hp @ 6000rpm and ends up at 480hp @ 7800rpm. Let's also assume, for ease of calculation, that the power delivery is perfectly linear between 6000rpm to 7800rpm. With this engine we would start at 380hp in each gear under acceleration (apart from in 1st at launch) and the engine would gradually build power towards the shiftpoint at 7800rpm where we have max power of 480hp. The interesting thing here would of course be what average power this engine develops in each gear (because that would tell us about the total acceleration. Peak power means little since the engine only sits there for a very brief moment). Average power, in gear from 6000-7800rpm, for this hypothetical engine would be: 480+380/2 = 430hp Here we have a 480hp engine that makes an average power, in gear, of 430hp. Not that far off the average power of the S55, which only is a 425hp engine... I believe my example shows how the S55 can perform like a much larger "traditional" engine under acceleration. Because it's max power is also it's average power, in each gear, under acceleration. Hope this makes sense |
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08-14-2014, 05:42 AM | #29 |
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If the car for all practical purposes acts, performances, dynos and feel closer to 500 hp than 425 who really care about the academic question if a lab mounted engine is within specs in a scenario it will never be used in? It seems like a question only interesting to officials and not car buyers. It's not even interesting for simulation if the resulting academic crank hp is no longer reflective of real life performance. I still suspect the engine is underrated vs. actual power delivered when the S55 is working in a production car even if I don't for a minute think it's a conspiracy. Some tuning of parameters or ( legal ) lack of or normalization of some DME inputs maybe but not a conspiracy involving officials as in lying of measured results.
Last edited by solstice; 08-14-2014 at 06:01 AM.. |
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08-14-2014, 06:12 AM | #30 | |
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There is a reason race engine builders use engine dynos to test and develop their engines. And they also want to make sure that the engine performs the same way when it's in the race car... My point is that the "academic" crank hp actually represents very well how the S55 performs in the car and why it performs like a much more powerful engine, due to it's high average hp. I believe, both because of the trap speeds and high average hp of the S55 AND the rigid and thourough EU-type approval framework (both legal and technically) that there is a VERY small possibility that the S55 is under rated by anything more than 5% (which is the allowed EU tolerance). BTW, any "tuning" of parametres or "normalization" of DME parametres would all imply misleading and misrepresenting the engine when tested for type approval authorities. The dyno room conditions are set up according to strict parametres and any "special software calibrations" for the dyno run would certainly have to involve a lot of people that knowingly program those parametres to achieve a lower hp result... |
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08-14-2014, 07:17 AM | #31 |
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OT but, how do you measure whp on the vBox??
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08-14-2014, 08:04 AM | #32 |
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I'm still confused
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08-14-2014, 08:27 AM | #33 |
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The power plateau is nothing really unusual. Look at the N63TU for example. It is quite interesting since it has similar power levels and power delivery. It is rated 20 hp above the S55 but seem to dyno about 20 hp below the S55. Furthermore when looking at the shape of the power curves it should average similar power from 4500 rpm to 6500 rpm as the S55 between 5500 and 7500. I.e it should get higher to match it's 445 hp rating to make up for it's drop off towards the redline. I.e it's power plateau and area under the graph should provide similar effect in power between shift points.
Unfortunately there is no car of the M3s' weight with an N63TU, however I'm not sure how much the weight difference really impact trap speed in cars of this size and engine type. The track day I spent with all the N63TU cars I managed the highest trap speed of the day at 109.5 mph in the 750 Li... I ran the others as well as the 650 coupe but it was not faster... Looking at other trap speeds for these cars it seems like the N63TU cars trap at about 10 mph down on the S55 cars. That seems a lot, more than the lower weight and stated less hp should allow. It just seems that whatever reasonable theory is raised for no under rating as double correction and power plateau they just don't hold to explain real life data, relative or absolute. |
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08-14-2014, 09:13 AM | #34 | ||||
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I can't comment on the EU regulations. We don't know anything about them. But you certainly make a good point. Quote:
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08-14-2014, 09:28 AM | #35 | |
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Thanks for your response, appreciate it.
Yes, I would be curious to see your opinion of DashDyno, its strengths/deficiencies, etc. Also, as far as the actual moment from the ECU not being accurate, none of my own logging corroborates this. If anything, it tends to run higher than I would think (not lower and then I do the dash dyno run and apply the 13%-15% drivetrain losses and seems about right). However, if that dyno was from a tuned M3, that could account for the difference/inaccuracies. I own two tunes, one of the tuners changes the minimum torque tables (which result in extremely high TQ numbers), one of them does not (results in in line TQ/hp numbers for a tune), and I have logged the stock ECU, and again seems to produce around 410-420 bhp. I believe that others who have done this in the past also have corroborated that on an untuned engine, the actual moment from the ECU is fairly accurate..this is actually what got me started looking at logging this parameter. Since support is not there for the F80, maybe doing a stock actual moment logging and vbox (or dash dyno) logging would be great to establish a baseline and then use the same procedure for an untuned F80 once the support is there. Thank you in advance. Quote:
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08-14-2014, 09:37 AM | #36 |
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I have a simple / unscientific test that could be telling.
Why not dyno a stock M4 on this dyno and get a result of 425 whp or whatever the number everyone has been claiming is. Then throw an FBO and e85 N54 that almost always dyno's around that power on Dynojets. If the power results on the dyno are similar, then race the two cars or take them to the track and compare trap speeds. Wouldn't this immediately resolve any inaccuracies in adjustements for ambient conditions if the cars are far off from each other in terms of real world performance?
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08-14-2014, 09:51 AM | #37 | |
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I think its also appropriate to consider the fact that this is not the only engine that seems to be underrated the new 5.5L turbo from merc, the 3.0SC from audi, the 4.0TT from audi to name a few have all been dyno'd at significantly higher values than the manufacturers claimed values they also perform in line with those numbers. |
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08-14-2014, 10:06 AM | #38 | |
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And, yes that's how I understand the DME operates. As you say (and has we have discussed at length in the other thread), the understanding is that the DME regulates for ambient/altitude (probably also including limiting/lowering boost in cold weather at low altitude). |
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08-14-2014, 05:48 PM | #42 | |||
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BTW, I’ll look at the Dash Dyno a little later. I’m really curious where they’re getting velocity. But we’ll look into it and post an update. We might even buy it and try it on our own F80. It would be a really good comparison to the vBox and vBox Dyno. |
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08-14-2014, 07:13 PM | #43 | |
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My point is that it appears that some sort of minimum torque setting that can be overridden with certain tunes and influence the actual moment, otherwise it is a strict calculation. But on a stock car and with certain tunes the calculations appear to be directly affected by various parameters, unless something is overridden (based on my discussions with tuners and my own logging of dozens of parameters, where it can be clearly seen). It is my understanding the ECU looks for a minimum torque value that is calculated (or set so low in the table that it won't matter unless things are going wrong..I'll have to look back at my logs but I believe I get different miminum torque ratings based on environmental factors, showing that untuned, it is a calculated value from various parameters) or alternatively with different tunes, this calculation be overridden. I just know what I've gotten with stock tune, and two different tunes using actual moment with dozens of logs. The person who maintained the dyno DB also did some actual moment logging and seemed to work fine with stock cars, but not with all tuned cars. You can talk to the various tuners as to what they modify/don't modify. Also, when I put in better fuel, the timing targets are hit (vs timing pulled on 91) and there is a direct change in power as calculated by actual moment, even at equivalent temperature/ pressure. Also, I have observed that changes in mass airflow, altitude, atmospheric pressure, IATs vs ambients all influence power/actual moment produced. I have the benefit of road logging on flat roads at sea level, where it is very easy to control for environmental factors and established enough baselines to see how changes in various parameters influences power. So to me is shows that various inputs change the calculation, unless things in certain tables get overridden.
For example, I just logged an E85 mixture, and I got the highest Actual Moment value I have ever logged, under any temperature or pressure conditions. Since we're talking stock, from all my logging, there does not appear to be evidence I can see from my dozens of logs that actual moment isn't accurate on a stock car, as it matches the factory stated bhp (with 93 octane) and my dash dyno logging. Also, one of the points I was trying to make earlier, but noticed I was missing a few words that made it really unclear is that would be curious to try Vbox/Dash Dyno and compare to BT actual moment on an E90 M3, on the open road. This would establish a baseline for the accuracy of open road logging per wheel hp calculations and what the ECU says the engine is producing (per BT actual moment) for the S65, then test it with the S55 once BT offers support for the S55. Thx for looking into the dash dyno.. I'm curious about your thoughts. Quote:
Last edited by FogCityM3; 08-14-2014 at 07:37 PM.. |
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