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07-10-2013, 04:34 AM | #222 | |
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And, a turbo is designed to be propelled by exhaust. But what the exhaust does is "only" to spin the turbine shaft, in effect changing the rpm of the turbine shaft and thereby the compressor part of the turbo can do it's job. Whether the turbine shaft is driven by exhaust or the electrical motor doesn't make any difference, does it? |
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07-10-2013, 05:34 AM | #223 | |
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07-10-2013, 05:37 AM | #224 |
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it's probably been posted in this thread already but BMW filed a patent in Germany for an electric (multiclutch) turbo offering less turbo lag. I'm not sure if this post was around the same time as the actual patent filing but the post is way back from October 2011:
http://f80.bimmerpost.com/forums/sho...d.php?t=597327
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07-10-2013, 05:51 AM | #225 | |
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In a high voltage circuit of, say 250V (as a KERS type circuit is) that is around 4amps... 5000W at 250V is 20amps. A EV/Hybrid vehicle generally has 100-300V and the Prius has a voltage converter that can "boost" the voltage going to the electrical motors to 600V... The electrical generator/motor on the F1 turbos are fairly big: But the cabling isn't THAT big diameter, due to the high voltage they operate under. If it can be made to work on a F1 engine, why not on a production engine? You would obviously need a energy storage unit for the high voltage units. And it won't be able to spool the turbo for prolonged periods of time without also being in a regeneration mode from time to time. Last edited by Boss330; 07-10-2013 at 06:15 AM.. |
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07-10-2013, 06:08 AM | #226 | |
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In a racing car, easy, as the power demand can be mapped for an individual circuit. On a road going car, how do you predict a WOT event with enough time to drive an anti lag system that will be driven with much less energy than the normal energy fed into the system in the first place? It just makes no sense whatsoever. |
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07-10-2013, 07:10 AM | #227 | |||
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And a hybrid/electric turbo can accelerate from 40,000 to 120,000 rpm in less than 450 ms. This rate of acceleration eliminates the turbo lag which is a major limiting factor on the performance of standard turbocharged engines. http://en.wikipedia.org/wiki/Hybrid_turbocharger The electric motor (MGU) reacts so much faster than the turbine would from exhaust gases, this is where you can loose most of the turbo lag. And as I mentioned earlier you could even have a "M-mode" where the MGU actually keeps the turbo spinning at a rpm where boost constantly is made during deceleration, part throttle and where the turbo would "be boosting" even before WOT. And while at WOT the MGU acts as a generator/boost controller, recuperating energy and controlling boost levels at the same time From an article on BMW's electric turbo patents: Quote:
Borg Warners eBooster: Quote:
Bowman electric turbos for trucks: http://www.bowmanpower.com/technolog...turbochargers/ Turbos with a electric generator/motor unit makes a lot of sense to me Last edited by Boss330; 07-10-2013 at 07:17 AM.. |
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07-10-2013, 07:29 AM | #228 | |
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The other thing that makes me chuckle in your wiki link, is the whole reason for using turbo chargers in the first place is to use the efficiency of the low or unboosted state where the engine uses significantly less fuel. To add a device that artificially maintains boost, is surely defeating the object? May as well stay with a larger NA. The biggest factor in Turbo lag is the inertia of the entire turbine unit. Hence the reason for using smaller turbo's to overcome the inertia issue. Also why some manufacturers use ceramic turbine blades instead of metallic ones, again to reduce weight of rotating mass and lower inertia.... ....so someone thinks it is a good idea to add clutches and gearboxes to turbines significantly increasing inertia all to reduce lag? Doesn't take a rocket scientist to how anti productive that thinking is. My guess is all this is more focussed on harvesting the 'wasted' energy than reducing lag. |
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07-10-2013, 07:57 AM | #229 | ||
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http://www.acarplace. com/ cars/ turbochargers.html Quote:
http://www.osti.gov/bridge/servlets/...ive/841240.pdf This report provides very interesting reading! http://www.bmwblog.com/2011/07/09/ed...trical-assist/ You oversimplify when you state the reason to go turbo is "to use the efficiency of the low or unboosted state where the engine uses significantly less fuel. To add a device that artificially maintains boost, is surely defeating the object? May as well stay with a larger NA." What you are saying is that modern turbo engines don't boost before medium revs??? The fuel economy benefit of a smaller turbo engine vs a larger NA engine is more complicated than boost/no-boost: Less cylinders means less frictional losses (significantly less). Fewer combustion cycles per rpm etc. A modern turbo engine is on boost from very low revs anyway. In a "M-mode" I wouldn't think fuel consumption was the main priority either... It's not only inertia that is the reason for going to a smaller turbo. A large turbo will need larger amounts of exhaust gas to spool up but will be able to handle higher rpms and the resulting larger volumes of exhaust gases. A small turbo spools quicker as it's a smaller amount of exhaust gas needed to rotatet the turbine, but restricts exhaust gas flow at higher rpm's. This is also one area where the MGU would come into play. You can have a larger turbo, that can handle high rpm's, but with reduced lag from the assist of the MGU. Last edited by Boss330; 07-10-2013 at 09:04 AM.. |
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07-10-2013, 09:49 AM | #230 | ||
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Agreed on the smaller engine having lower frictional losses. I'll point out a little scenario that helps understand why turbo engines are so fuel efficient. Take a 335i cruising on the highway at 70. In this steady state it only needs about 50hp to maintain the speed. 50hp of airflow is not much at all, so the throttle valves will only just be cracked open. In this state, regardless of engine revs, very little energy is flowing through the turbo, therefore it runs slowly, and produces little to no boost. Here we have a turbo charged engine running in almost NA engine conditions. Good fuel economy. Flipside time.... ........we all know that a turbo engine on full booost runs stoichiometric-ally richer than an equivalent NA engine. Therefore on boost a turbo is LESS fuel efficient, power for power. Proof if needed that it is only at low-No boost conditions where a turbo engine is actually able to run more efficiently than a similarly powered NA. Frictional losses/weight of powertrain aside. Quote:
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07-10-2013, 09:54 AM | #231 |
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One of the links above agrees with me
"What the electrical assist does is spin the turbine up to speed in very light to no load conditions. And the term ‘light to no load’ is the critical piece. Under load, you have to supply massive quantities of amps to the electric motor to generate the boost levels needed. But if all that is required is for the turbine to be spun up then an existing automotive electrical system will work just fine" Suggests that automotive electrical systems are not powerful enough to produce positive boost pressure.....and yes you can fit a prius motor and 3 phase electrical system to drive a compressor, but really? an extra 100kg's to reduce lag by a few tenths? |
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07-10-2013, 10:19 AM | #232 | |
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To me it makes sense to have a MGU on a turbo, to you it don't. No problem We'll just have to wait and see what the future brings |
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07-10-2013, 10:21 AM | #233 | |||
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The electric motor can also prevent the turbo from spooling down. Even if the electrical system adds inertia to the system, if the electrical motor is able to maintain some speed in the turbo, intertia is less of an issue. At partial loads, the turbine is still contributing work to keep the rotor spinning, albeit not enough to maintain full boost. An electric motor would simply assist the turbine to maintain the speed of the rotor. The electric motor would just supply the delta work required to maintain boost, not the entire work. Quote:
I see the biggest challenge in all of this mostly with the control systems. Maybe 10 years ago, the control technologies were not there to support the concepts. Great strides have been made in electronics and computer control technology since. Last edited by CanAutM3; 07-10-2013 at 10:56 AM.. |
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07-10-2013, 10:32 AM | #234 | |
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07-10-2013, 10:47 AM | #235 | |
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Those electric turbos on e-bay do not have an exhaust driven turbine to spin the compressor and maintain the boost once the mass flow demand increases. |
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07-10-2013, 11:12 AM | #236 |
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Personally I hope they just find a simple mechanical solution to reduce lag to industry leading level. I prefer that to a more complex electrical solution. F1 engines are reliable today but the number of times the KERS failed in it's early days were not few. I prefer the simplicity of NA engines and a change to FI is already enough added potential point of failures at one time. Not all FI engines are unreliable but BMW's TTs have their share of fuel delivery issues wether it's the N54 or N63.
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07-10-2013, 11:14 AM | #237 |
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So you think they work at partial throttle like you said?
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07-10-2013, 11:16 AM | #238 | |
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Even with all the information from turbo manufacturers and Renault F1 about how the MGU can be used to spool up the turbo to avoid lag, NISFAN isn't convinced that this actually has any real world effect... |
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07-10-2013, 11:20 AM | #239 | |
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The e-bay stuff is not what we are talking about here...
In next years F1 technical regulations, the MGU unit is not allowed to operate at a higher rpm than 125.000. That would be sufficient for part throttle, right? Quote:
Last edited by Boss330; 07-10-2013 at 11:27 AM.. |
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07-10-2013, 11:54 AM | #240 | |
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The Turbo generator is to enable an F1 car to HARVEST energy to recharge the battery to give the 161 crank hp. It can't harvest that on brakes alone like they do in 2013. Adding additional weight to something you are trying to keep low due to inertia, is counter productive. Simple science. The simple fact is, if they didn't use ERS-K they would NOT have this device sitting on the Turbo. No other form of racing uses this, of which there are many turbo charged classes....why? because there is no need for it. |
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07-10-2013, 12:15 PM | #241 | ||||
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You have been privy to the process of F1 tech regulations and development since you can claim the following as a fact? Quote:
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Of course, one of the main objects of the MGU-H is to regenerate energy from the turbo. And it's not me who claims that it is also used to reduce lag, match the air flow of the engine and act as a wastegate. That's RENAULT F1's statement. If you disagree with them on that, please, be my guest And the MGU-H is clutched to the turbine shaft, reducing the increase in inertia: Quote:
Last edited by Boss330; 07-10-2013 at 12:31 PM.. |
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