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electric supercharger 7
- Thread starter ed911
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We tried a powerful short-burst electric "turbo-charger" of sorts, on buses in Los Angeles. The intented purpose was to eliminate the puff associated with older Diesel engines. It worked, but for stop and go driving it ended up requiring more electrical power than even a modified charging system could provide.
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GregLocock
Automotive
We measured the power consumption of a supercharger on a 4 litre V6. It was around 40 hp.
Have you seen a 40 hp electric motor? Can you imagine running one on 12 V?
Even if we assme that the blower was only half as efficient as a modern design, and you only needed half the airflow, that is still 10 hp, or several hundred amps.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
Have you seen a 40 hp electric motor? Can you imagine running one on 12 V?
Even if we assme that the blower was only half as efficient as a modern design, and you only needed half the airflow, that is still 10 hp, or several hundred amps.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
The use of electric superchargers has only started to become interesting and viable with the advent of the 42v electrical system - I doubt there is anything particularly useful running on 12v, especially some of these things you see on e-bay!
The use of an electrical supercharger is attractive in a number of ways, not least the fact that boost ceases to be a function of engine speed. Without the need to worry about wasted energy through the compression of air that is simply going to be sent through a bypass valve.
MS
The use of an electrical supercharger is attractive in a number of ways, not least the fact that boost ceases to be a function of engine speed. Without the need to worry about wasted energy through the compression of air that is simply going to be sent through a bypass valve.
MS
SomptingGuy
Automotive
Electrically assisted turbochargers are starting to break ground as engine downsizing catches on. But I've yet to hear of a car in production with one. A google search on "electrically assisted turbocharger" score many good hits.
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patprimmer
New member
How is boost not a function of engine speed.
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eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Pat ?!?
Surely the whole point of the 'electric' part of the supercharger is that an electric motor drives a compressor which then produces boost pressure. Making boost a function of electrical supply to the motor.
A 'normal' supercharger however is a compressor driven by a pulley that is in turn driven by the crankshaft of the engine, with boost a function of the cranksspeed (engine speed?!?)
In the electrical system there is no compressor/crank coupling - so boost is not a functino of crank speed. You could, in therory provide full boost pressure with the engine not running.
Perhaps you are talking about massflow, which IS a function of engine speed, boost and also VE...In which case we are talking at cross purposes.
MS
Surely the whole point of the 'electric' part of the supercharger is that an electric motor drives a compressor which then produces boost pressure. Making boost a function of electrical supply to the motor.
A 'normal' supercharger however is a compressor driven by a pulley that is in turn driven by the crankshaft of the engine, with boost a function of the cranksspeed (engine speed?!?)
In the electrical system there is no compressor/crank coupling - so boost is not a functino of crank speed. You could, in therory provide full boost pressure with the engine not running.
Perhaps you are talking about massflow, which IS a function of engine speed, boost and also VE...In which case we are talking at cross purposes.
MS
"OUR NEW 2007 ESC ELECTRIC LINE OF SUPERCHARGERS HAS THREE MODELS. RATED AT 250, 500, AND 750 CFM, THE ESC-250CM, 500CM, AND 750CM WILL FIT ENGINES FROM 1000CC UP TO 500 CID BIG BLOCKS. OUR ELECTRIC MOTORS ARE NOW 80-90% EFFICIENT AND SPIN THE SUPERCHARGERS WITH SHAFT RATINGS OF 6HP @ 24 VOLTS UP TO 26HP @ 72 VOLTS. EACH 1000CC REQUIRES 3.5HP, SO WE COVER EVERY CONCEIVABLE ENGINE SIZE WITH OUR NEW LINEUP. STARTING AT ONLY $1695, THESE ARE THE LATEST TECHNOLOGY IN THE AREA OF ELECTRIC SUPERCHARGING. IDEAL FOR HYBRID VEHICLES AS WELL."
Even though the electric "turbo" we used was probably a different design, it was incredibly powerful. The REP fired it up in the main office. Though aimed at an open door 10 feet away, it still cleared all the papers off several desks. The thing I would question most is electrical reserves vs desired duty cycle.
BTW, the one we tried worked in parallel with the OEM turbo. It used a simple flapper valve on the output side of the OEM turbo. The electric unit came on as soon at the throttle was pushed, moved the flapper, and simply out blew the OEM turbo until OEM boost came up. When this happened the flapper would move back and the electric unit would shut off till next time. Worked great, but even with an automatic transmission it used too much electricity for commercial city driving.
MacGyverS2000
Electrical
250cfm... but at what pressure? They will do zip for you if they can't create a pressure differential beyond 0 psi...
Dan - Owner
Dan - Owner
The last I understood these units to do is apply boost in the lower RPM torque curve area of a gas engine then taper off as engine HP/rpm builds up (using a controller).
Using this type application, the blower becomes a helper and does not run all the time but makes the overall torque curve quite high and flat where it is most needed.
I feel the smaller displcment engines benifit more for having the additional low end torque than trying to use this on large displacments that should already have enough reasonable torque.
I run a Kenne Bell positive displacment 1500 cc blower on a 5L v8. It 'do make' the motor feel like a big displacment for throttle response from about 1800 rpm upward and is even better off idle before boost actually begins.
Using this type application, the blower becomes a helper and does not run all the time but makes the overall torque curve quite high and flat where it is most needed.
I feel the smaller displcment engines benifit more for having the additional low end torque than trying to use this on large displacments that should already have enough reasonable torque.
I run a Kenne Bell positive displacment 1500 cc blower on a 5L v8. It 'do make' the motor feel like a big displacment for throttle response from about 1800 rpm upward and is even better off idle before boost actually begins.
patprimmer
New member
Boost is a function of airflow supplied over airflow used.
Airflow used is fairly well directly related to engine speed. A crank driven positive displacement supercharger also supplies air fairly well relative to engine speed. An engine with a crank driven properly sized roots blower will have an almost flat boost curve relative to engine speed over the normal operating speed.
I would expect an electric driven supercharger will only give constant boost if it is well regulated with pressure switches and controllers to control the electric motor well enough to overcome reaction times, relative friction and inertia and if the electric motor can provide enough power to keep up with engine requirements.
As mentioned earlier by Greg, this can be a very large electric motor, needing a very powerful electrical system to support it.
Crank driven simply requires a belt and two pulleys.
I guess, the question, or the quest will be, is the total package for the smaller engine and electric supercharger, smaller or larger than the larger engine with NA, turbo or belt driven or compounded belt driven positive displacement and turbo.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
Airflow used is fairly well directly related to engine speed. A crank driven positive displacement supercharger also supplies air fairly well relative to engine speed. An engine with a crank driven properly sized roots blower will have an almost flat boost curve relative to engine speed over the normal operating speed.
I would expect an electric driven supercharger will only give constant boost if it is well regulated with pressure switches and controllers to control the electric motor well enough to overcome reaction times, relative friction and inertia and if the electric motor can provide enough power to keep up with engine requirements.
As mentioned earlier by Greg, this can be a very large electric motor, needing a very powerful electrical system to support it.
Crank driven simply requires a belt and two pulleys.
I guess, the question, or the quest will be, is the total package for the smaller engine and electric supercharger, smaller or larger than the larger engine with NA, turbo or belt driven or compounded belt driven positive displacement and turbo.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
crysta1c1ear
Automotive
patprimmer
New member
I just followed the link.
So what is it supposed to tell me that explains away with any supporting data, any of the objections above.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
So what is it supposed to tell me that explains away with any supporting data, any of the objections above.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
GregLocock
Automotive
Just to add to the confusion, that is an electrically controlled mechanical CV transmission for a fairly conventional compressor. Not a bad way of doing it, but not really what this thread is talking about.
I like the idea of the all electric system. It would only activate at full throttle and it would run out of puff gracefully. But, on a 12V car I really don't see how to power it. Maybe an additional pair of deep discharge batteries in series, then switch them back to parallel for charging.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
I like the idea of the all electric system. It would only activate at full throttle and it would run out of puff gracefully. But, on a 12V car I really don't see how to power it. Maybe an additional pair of deep discharge batteries in series, then switch them back to parallel for charging.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
crysta1c1ear
Automotive
pat
The link was for general interest rather being a direct response to the posting that came before it (yours). Some of the criticism of electrically driven supercharging was the electric power needed to drive the compressor.
If you drive the compressor electrically then its speed is not directly linked to engine speeds and you have a CVT of sorts. The problem raised by the criticism of the electric power required for electric supercharging can then be rephrased: how can you electrically control the continuously varying ratio between engine speed and supercharger speed, without all the supercharger power being electrically sourced?
Powersplitting the engine power to the supercharger and just using an electric motor/generator for controlling the ratio is one way to drop the electric power figures, and that is what the nexxtdrive supercharger does. It seems to have two motors, so that one can generate and one consume power, in a way similar to the Prius CVT.
So - without any supporting data, sorry - I think it explains away the need for large external electric power. I think electrical power would be reduced due to a power split mechanism, and that electrical power would be circulting internally between a generator and a motor.
The link was for general interest rather being a direct response to the posting that came before it (yours). Some of the criticism of electrically driven supercharging was the electric power needed to drive the compressor.
If you drive the compressor electrically then its speed is not directly linked to engine speeds and you have a CVT of sorts. The problem raised by the criticism of the electric power required for electric supercharging can then be rephrased: how can you electrically control the continuously varying ratio between engine speed and supercharger speed, without all the supercharger power being electrically sourced?
Powersplitting the engine power to the supercharger and just using an electric motor/generator for controlling the ratio is one way to drop the electric power figures, and that is what the nexxtdrive supercharger does. It seems to have two motors, so that one can generate and one consume power, in a way similar to the Prius CVT.
So - without any supporting data, sorry - I think it explains away the need for large external electric power. I think electrical power would be reduced due to a power split mechanism, and that electrical power would be circulting internally between a generator and a motor.
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This may be a miles off topic, but the best solution to all these turbo problems with todays technology, seems to be to combine a turbo with a positive displacement supercharger, (with the compressors simply run in series). This has now been succesfully done on three mass produced production engines.
Nissan did it with the March, a small hatchback not sold outside Japan, it combined a Garret turbo with a roots blower.
Lancia did it with the Delta S4, again a KKK turbo with a roots blower, and two intercoolers.
VW are doing it right now with the Golf GTI hatchback just released in Europe this year.
I built an experimental system like this myself over fifteen years ago, the results were exceptionally good in all respects. The corporate bean counters are probably the only real obstacle to overcome, otherwise I am sure many more forced induction production engines would now be using this system.
It combines lag free low end torque, with high top end airflow. The advantages of being able to keep boost pressure just above exaust back pressure should not be overlooked. The torque curve can be made any shape you wish to make it, and it is relatively simple. Initial cost is the only real disadvantage.
I very much doubt if an electric supercharger could beat it, if you also take into account the extra charging and battery capacity that would be required. If used constantly, the extra alternator load must rival the power requited to drive a supercharger. And a small supercharger would probably have less weight and volume than an extra lead acid battery or three.
Nissan did it with the March, a small hatchback not sold outside Japan, it combined a Garret turbo with a roots blower.
Lancia did it with the Delta S4, again a KKK turbo with a roots blower, and two intercoolers.
VW are doing it right now with the Golf GTI hatchback just released in Europe this year.
I built an experimental system like this myself over fifteen years ago, the results were exceptionally good in all respects. The corporate bean counters are probably the only real obstacle to overcome, otherwise I am sure many more forced induction production engines would now be using this system.
It combines lag free low end torque, with high top end airflow. The advantages of being able to keep boost pressure just above exaust back pressure should not be overlooked. The torque curve can be made any shape you wish to make it, and it is relatively simple. Initial cost is the only real disadvantage.
I very much doubt if an electric supercharger could beat it, if you also take into account the extra charging and battery capacity that would be required. If used constantly, the extra alternator load must rival the power requited to drive a supercharger. And a small supercharger would probably have less weight and volume than an extra lead acid battery or three.
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