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05-10-2013, 03:27 PM | #67 |
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Ok, to settle this, we need an 18 wheeler flat bed that can accelerate at the same rate as a Z4M with a dyno on the back. Let make it happen zpost!
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05-10-2013, 04:11 PM | #68 | |
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Alternatively, why doesn't O-cha put his Z4M on a static dyno using his Autoenginuity software to datlog the ECU at the same time as the dyno runs to prove me wrong and show us all what really happens? |
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05-10-2013, 09:51 PM | #71 | |
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05-10-2013, 11:56 PM | #72 |
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The video was exactly what I was thinking when reading Exdos's posts. Because it seems to me that his general explanation of how he's getting such crazy power figures is due to the fact that a lot of air is being fed into the intake manifold...
And I've already noted in another thread that unless the air is pressurized, there's only so much air that an otherwise stock engine can make use of |
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05-11-2013, 05:02 AM | #73 | |
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To increase Torque you need to increase engine Volumetric Efficiency. Since the engine capacity is a fixed volume, the only way to increase the VE (i.e. the mass of the air/fuel charge in the cylinder) is to increase the pressure of air entering the cylinders and/or have the temperature of the charge as low as possible. Horsepower is calculated from Torque x RPM/ 5252. Because in that calculation the RPM is divided by the constant 5252, the point in the engine rev range at which Peak Torque occurs has a very significant effect on the HP figure which is calculated. I didn't make up that formula, so don't shoot the messenger! Try a few different calculations yourself to see how this works. At 8000rpm the S54 engine consumes (3.246litres x 4000 =12,984 litres) = 12.984 cubic metres of air/fuel mix. Air at 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m3, therefore, if the S54 engine at 8000rpm can be filled with air at this density, then it will consume (12.984 x 1.2041 =) 15.6340344kg/min of air (34.47lbs/min). If the air density is different, then the mass of A/F mix will be different, but the volume of 12.984 cubic metres of air will always be the same. A vehicle travelling through air will experience an equal and opposite force from the air related to the speed at which the vehicle and the air are travelling relative to each other which will create ""ram pressure". As such, an air intake designed to capture and retain air at ram pressure can supply an engine with air at a pressure greater than ambient pressure, therefore, it is possible to achieve a greater VE than would otherwise occur if the source of air is at ambient pressure, only. The Z4M's OEM air intake is such a design. I've previously stated that the OEM Z4M will record around 31lbs/min as Airflow through the MAF at 8000rpm in 3rd gear and since the charge at WOT is an A/F mix at around 13:1 AFR, then the actual charge is 31lbs of Air + 2.38lbs of Fuel = 33.38 lbs of A/F mix. Therefore the OEM S54 engine is operating at a VE of 96.85% at peak revs. Since the engine is an air pump, the exhaust system must also be made more free-flowing so that exhaust gases can escape to allow the greatest cylinder filling (i.e. highest VE/torque). The Z4M's OEM ram air-intake is very good, but it can be improved by using the same scientific principles long used in other totally unrelated applications. The objective is to provide the engine with a constant supply of air at ram pressure and the graph below shows how ram pressure increases in relation to speed. Therefore, the faster the car travels the greater the pressure difference above ambient pressure is the charge, thus increasing VE/torque and shifting the peak torque to higher rpms, thus considerably increasing the HP. Last edited by exdos; 05-11-2013 at 06:05 AM.. |
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05-11-2013, 06:37 AM | #74 |
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05-11-2013, 07:52 AM | #75 | ||
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If the S54 produces at 180 ft*lbs torque at the rear wheels at 8000 rpm (274.2 whp), even at 100% VE you would only produce 8.6 more hp (282.8 hp). To produce 370 whp, you will need to run the engine at 131% VE, or increase cylinder pressure by about 4.5 psi on a standard day. 4.5 psi is the same pressure increase that a Vortech blower gets by spinning at tens of thousands of rpm. That's a whole lot of air. http://en.wikipedia.org/wiki/Ram-air_intake Quote:
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05-11-2013, 10:32 AM | #77 | |
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The Volumetric Efficiency of an engine is constantly varying and is not a fixed percentage. The published VE of the OEM S54 engine is 106% and this will occur at, or close to, peak torque, which is normally at 4,900rpm and therefore peak torque is the place to best look rather than max revs. Normally, the lowest Intake Air temperature recorded by the OEM air-intake is 7degrees C above ambient temperature, but I've now I've got mine working at ambient temperature without relocating the MAF/IAT sensor. Obviously, this increases the density of the charge. Likewise, in OEM format at 4900rpm at WOT in 3rd gear acceleration, the MAF of my Z4MC shows an air-flow rate of around 21.38lbs/min but now, after gutting the silencers and doing a few mods to the air intake system, the airflow rate is now in the order of 23.07lbs/min, in similar ambient conditions. That's an increase of 7.49% in the mass of air ingested so the VE has increased to 113.93% at 4900rpm. Because I've made the air intake more able to harness the ram effect at all speeds, the increase in ram pressure with the increase in speed means that there is less pressure drop within the air-intake system as engine rpms increase, and consequently, the plot of torque now shows less of a peak and more of a plateau across the upper range of rpms, where my MAF now records an airflow of over 34lbs/min in comparison with the OEM figure of 31lbs/min, an increase of 10.3%. When I use a Magnehelic Differential Pressure gauge to monitor the pressure within the air-intake system, in 3rd gear acceleration at WOT, now, the pressure never dips below ambient pressure. I have produced the acceleration figures for all to see, elsewhere. Nobody seems to bother much about the gains in torque, and all the critical focus seems to be on HP. The formula to calculate HP shows quite clearly why the shift in peak torque as far up the rev scale as possible gives such huge increases in HP. I don't make up the figures I record and I didn't make up any of the formulae to work any of this stuff out. Anyway, here's a graph showing the torque/hp of my car in OEM format, with gutted silencers and modified intake. It seems that the spike at the end of the torque curve in the yellow plot that is causing all the trouble. |
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05-11-2013, 10:58 AM | #79 |
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Certainly. The dip seen in the OP's dyno plots at around 7300rpm is also markedly shown in one of my plots from "real world" driving as above. So I guess this is normal for the Z4M.
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05-11-2013, 01:56 PM | #80 | |
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Just ignore Exdos. Anyone that's silly enough to believe a figure of 370rwhp with intake modifications on an otherwise stock car clearly has zero common sense. Again, as others have stated in other threads: not to take away from the work that he's put into logging data, but come on....enough is enough If it were THAT easy to produce power, why don't you copyright or trademark your amazing intake invention and make thousands off of Z4 owners the world over? I double dog dare you Oh, and I'd like to ask for a measly 1% of the share of the profits, since I just provided you this wonderful monetizing idea. Heck, I even have a patent lawyer that I can hook you up with |
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05-11-2013, 05:42 PM | #81 |
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That's precisely what I've been researching. If I ever attempt to market the invention it will be independently tested by a recognised engineering faculty rather than some bloke at a dyno shop with an inadequate fan.
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05-12-2013, 02:40 AM | #82 | |
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There's no forum-member cure here. |
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05-12-2013, 08:50 AM | #83 |
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Has anyone dyno tested the tune from ESS?
Looking at stock AFR which are rich in upper RPM it would seem power could be gained from correcting them. My car broke 300WHP on a stock tune, I am going to need some SOLID proof something actually works to warrant the cost.
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05-15-2013, 07:42 PM | #84 | |
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Any ideas anyone? |
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