[Shovelman]

A turbocharger or a supercharger is a compressor that is not able to deliver the right boost at all times. Sometimes too little but most of the time it is more parasitic drag than is needed. It spins too slowly with the throttle shut and takes too long to spool up.

Why not use an electric motor to spin the compressor? Motors have come a long way in the last few years, they are lighter and more powerful. Controls have reaches genius levels.

The motor would be sized to support full rpm so at lower rpm it would have plenty of torque to ramp up very quickly. Or it could be spinning fast all the time but with an intake valve so it would be spinning in modulated vacuum.

The alternator would need to be bigger to support the motor but it could charge only when the power is not demanded for hard acceleration.

1. Minimized parasitic drag so more net power

2. And more fuel efficiency

3. The perfect boost available all the time so more power and torque at all RPMs

[Cumberlandjames]

I find that my M235 does not have any noticeable lag. Power is delayed more from the 8 speed transmission shifting down to a power gear. Driving in manual mode results in instant response. If your 230 is experiencing lad I would suggest the following modification.
In my old A5, which was prone to lag and a loss of response, I installed an aftermarket diverter valve from Go Fast Bits. Typically the diverter (blow off ) valve dumps the pressure when you let off the throttle so you have to rebuild it every time. The GFB valve is different and maintains some of the pressure thus eliminating the lag. It uses the OEM valve body and replaces only the end mechanism. I was very satisfied with the improvement. Check out the DV+ at GoFastBits website.

[BEM-S4]

First of all a Turbo charger and super charger are two very different things. What you're suggesting makes no sense for a super charger.

Turbo perhaps but you lose some of the benefits of that approach by attaching a motor assist. Best to just learn how to massage your driving style to fully exploit the Turbo and its inherent benefits.

[aelarson]

Originally Posted by Cumberlandjames

I find that my M235 does not have any noticeable lag.

I am in the same boat. The only exception is when I really hammer down in 1st gear, I'll notice the boost kick in a second or two late. But other than that, I think its pretty linear as is!

[Shovelman]

Ok you're still in the box. I'm not thinking about your engine or mine. Those are what they are. I'm thinking about a next generation engine.

A compressor is a compressor, it uses power whether it is spun by a belt or by the pistons pushing exhaust gasses thru a turbine. That power reduces power in real time. A motor can suck from the battery for a few seconds while the pedal is on the floor.

Optimizing boost at all times is a very complex task. A turbocharger is a simple device. It is carefully sized and controlled to do a better job than a much simpler throttle valve but there is still a lot of room for improvement. A supercharger is even simpler and less efficient than a turbo and is less commonly applied due to inherent costs in power and efficiency.

A motor driven compressor can do much better.

[TajoMan]

I believe there are some application for Hybrid vehicles that uses electric assisted turbo.
It's just more expensive and difficult to guarantee the electric motor's life with heat from the exhaust.

[BEM-S4]

Originally Posted by TajoMan

I believe there are some application for Hybrid vehicles that uses electric assisted turbo.
It's just more expensive and difficult to guarantee the electric motor's life with heat from the exhaust.

That's more where things are headed, an ancillary electric motor to "fill in the gaps" so to speak. Turbos are also going to get drastically mor efficient with the increased deployment of speed sensors (physical for higher end cars, virtual for lower end).

[TajoMan]

Originally Posted by BEM-S4

That's more where things are headed, an ancillary electric motor to "fill in the gaps" so to speak. Turbos are also going to get drastically mor efficient with the increased deployment of speed sensors (physical for higher end cars, virtual for lower end).

yep. It's all about cost.
Technology is already there.

[crabu2]

It might make a small difference with a super charger since the motor's spinning it all the time, but since a turbo works off the exhaust, it's more efficient. The exhaust is going to push out any ways... so why not use it to ram air into the intake.. exhaust is just wasted energy.... where if you use an electric motor, you're robbing some power from the motor to keep the battery charged... Plus, I see a much larger battery being needed to drive an electric air compressor.

[BEM-S4]

Originally Posted by TajoMan

yep. It's all about cost.
Technology is already there.

Cost yes. And emissions regulations and a variety of other factors. Were kind of at a perfect storm moment for the next 5-10 years in terms of smaller engines, hybrids, autonomy, etc. etc. etc.

Think about it this way. M2 for example runs through 2020. 2021 car will arrive 4 years from now. That car may be the last great drivers 2 that resembles anything that we'd define as "a drivers car" for the last 50 years.

[Rayscott]

Originally Posted by BEM-S4

Cost yes. And emissions regulations and a variety of other factors. Were kind of at a perfect storm moment for the next 5-10 years in terms of smaller engines, hybrids, autonomy, etc. etc. etc.

Think about it this way. M2 for example runs through 2020. 2021 car will arrive 4 years from now. That car may be the last great drivers 2 that resembles anything that we'd define as "a drivers car" for the last 50 years.

Time for a new 2 series in 2021. Timing for me is perfect.

[BEM-S4]

Originally Posted by Rayscott

Time for a new 2 series in 2021. Timing for me is perfect.

That's why I've got a deposit down on an M2 or M240 GC

[Maynard]

Crabu2 is on to it - the turbo uses energy that is otherwise wasted, so it is the best option overall for efficiency or max power. An electric motor for a supercharger would be an option, but more complex and still some waste (you need to generate, then use the electric energy, rather than just driven direct).

I think you are underestimating the complexity and flexibility of modern systems, and the other options to reduce turbo lag (e.g. finding a way to increase initial exh. pressure, or retain high rpm in the turbo). These current systems have almost instant adjustability for pressure/volume, and can modify exh intake to maximize velocity at low engine speed. I think that the major changes will be detonation control and ignition, as well as longevity.

But for outside the box - how about bringing back steam engines. With modern tech and materials, they could be quite viable alternatives to the electric cars with on-board gas generators. Much better thermal efficiency, IIRC, and would be able to use any fuel. Or ways to use the exhaust/coolant thermal energy, rather than just blowing it out the tailpipe.

[3.0L]

We already have hybrid vehicles, so why not a hybrid turbo? An electric motor could keep the turbo spun up when the engine has low RPM's, then defer to the exhaust driven part of the turbo when RPM's are up. Today's brushless motors pack a huge amount of power into a very small package, so the weight penalty would be slight (ask me: my entire fleet of RC aircraft use brushless motors).

[XutvJet]

VW has a twin-charged motor on market that runs a roots supercharger for low end power and a turbo for mid and higher rpm power. The roots blower only works in the low rpms in an effort turbo lag and then disengages via a vacuum device once the turbo is at full boost.

There are a few companies out there currently experimenting with electric and electric assist turbos. The recently introduced "KERS" electric/heat assist turbo motors for F1 is the likely future though (https://www.formula1.com/en/champion...y_Systems.html).

For now though, most turbo applications will experience lag to an extent. Lag is getting reduced, little by little, but it still remains the inherent nature of a turbo motor. Turbos are load dependent (it's exhaust gas that spins them after all) so that means the harder you are on the throttle, the more boost that can be generated. Also, the larger the turbo, the more the initial lag. Golf Rs and AMG CLA45 have big turbos in relationship to their small 2.0L motors, thus they have pretty terrible initial lag. Lag also tends to be most prevalent in manually equipped cars. The reasons being:

1) Manuals typically don't produce as much initial load as an automatic on tip-in throttle to ramp up the turbo because there's no torque converter to slip (i.e., load) and multiply torque. Unless of course you leave the 6MT car in a high gear and mash the gas at a low rpm. Do that you'll create max boost very quickly; however, that creates a dangerous high load situation that can cause pre-detonation or what is commonly referred to in direct injection motors as low-speed pre ignition (LSPI) which has blown up many newer DI turbo motors. BMW's DME does a great job at managing LSPI though.

2) Boost is lost on the slower shifts.

Technology is there to reduce the boost loss on shifts in manual cars (the M235 and M240 do pretty well), but tip-in throttle does result in momentary lag. With that said, the lag I experience in my M235 6MT is NOTHING like I dealt with in my 2012 WRX which felt like an early 1990s turbo car in comparison.

Turbo cars have multiple personalities with respect to power delivery. If you're driving very sedately, you'll experience hardly any boost and it will drive like a naturally aspirated motor. Drive it somewhat aggressively and you'll get a bit more power and likely to feel some lag. In some cases, power delivery can feel somewhat wonky as the ECU and turbo management systems try and gauge your intentions for power. BMW has gone to great lengths to reduce odd power delivery in moderate throttle application. In my WRX, moderate throttle resulted in a bumpy powerband (best way I can describe it). In aggressive driving, you'll experience a wiff of lag and then a strong and a somewhat linear surge in power. If you're very quick on the shifts in a 6MT car, the power and acceleration on the gear change is shockingly seamless and smooth.

[TigerTrump]

The new 48volt car electrical systems enable an 'E-charger' to spool up a turbo or can be used to power 'electric superchargers'. Here's an article from Jalopnik..

http://jalopnik.com/everything-you-n...olt-1790364465

[delvec03]

I am confident that Mazda was looking into the electric turbo for the low tomorrow range of the next gen rotary engine (RIP). that would have allowed the poor bugger to generate torque at something less than 4k!

[delvec03]

I am confident that Mazda was looking into the electric turbo for the low tomorrow range of the next gen rotary engine (RIP). that would have allowed the poor bugger to generate torque at something less than 4k!

[Deutsche-Broke]

Boosting intake pressure is quite easy, but doing it RELIABLY, to a moving target EPA and MPG standard, WITH a bulletproof warranty is another quagmire.

I think for 2016/17, BMW has nailed it.

Those worried about lag are traditionally looking for hundredths off straight acceleration times and not much more. The greatest aspects of the 235 / 240 as a whole are traditionally overlooked on this part of the market..

The fact that they have included mandates for auto start / stop and "Eco Pro modes", provided the ability to get decent mileage on long, steady trips combined with the ability to go like hell and push an impressive turbocharged N55 through the entire RPM range is nothing short of incredible.. I can't really ask more out of 3 liters of displacement and throw a warranty on the whole package... While the B58 looks to be a tiny bit better, time will tell....

Of course there are Dinan adds, but I have always been a disciple of the, "Buy the car you want, not the one you want to build, club".. If it's a race car you want, go to town, but don't expect warranted reliability.. I've had a few and thrown a crap ton of money into them.

Also in fairness, I don't use eco-pro mode, auto start / stop or have a Dinan tune, but the well roundedness regarding power delivery, smoothness and predictability pre and post DSC are second to very few comparably in it's class.. And i'm not looking to impress anyone but myself.

[aerobod]

Assuming an electrically driven supercharger is used, at maximum boost of about 1 bar on a 300bhp engine, about 20% of engine power would be needed to compress the air to 1 bar, or 60bhp / 45kW. That means with a 48V electrical system just under 1000A would be needed at full boost for an electric motor to drive a compressor / supercharger, that would require a lithium ion battery weighing about 10kg with a 1kWh capacity to give 60 seconds of boost. The additional alternator weight (assuming an additional 100A of capacity) and supercharger electric motor will likely add another 20kg. This system would allow a maximum 10% duty cycle, i.e. full boost no more than 10% of the time.

Just using a mechanical supercharger with an electromagnetic clutch is a lot simpler and lighter and can give continuous full boost if properly designed, even if an electrically driven system could be a bit more flexible.

Another issue with using batteries to power an electric compressor is that you normally will only get hundreds of charge/discharge cycles before battery replacement, so an ultra capacitor at about 20kg for 1kWh capacity would be a better power source.

[Maynard]

And IIRC, that type of ultra-capacitor would probably have the lethality of an entire fleet of coffee'd up mustangs. It would put the one in the xenons to shame, wouldn't it? - the kind of zap that would leave a burn track right thru you. And glad to see somebody breaking out the slide rule to remind everyone about the law of conservation of energy.

[Shovelman]

Originally Posted by aerobod

Assuming an electrically driven supercharger is used, at maximum boost of about 1 bar on a 300bhp engine, about 20% of engine power would be needed to compress the air to 1 bar, or 60bhp. That means with a 48V electrical system just under 1000A would be needed at full boost for an electric motor to drive a compressor, that would require a lithium ion battery weighing about 10kg with a 1kWh capacity to give 60 seconds of boost. The additional alternator weight (assuming an additional 100A of capacity) and supercharger electric motor will likely add another 20kg. This system would allow a maximum 10% duty cycle, i.e. full boost no more than 10% of the time.

Just using a mechanical supercharger with an electromagnetic clutch is a lot simpler and lighter and can give continuous full boost if properly designed, even if an electrically driven system could be a bit more flexible.

Thanks aerobod, we needed some numbers. Still, compression is not free with a super or turbo charger. If it takes 60 hp to compress air at peak rpm and boost, that load is siphoned from the power at the wheels. (The pistons have to work harder to push air thru a turbo than to push it out an unstifled exhaust system)

A fully electric compressor provides 60 more horses from the battery to the wheels.

A 10% duty cycle is more than adequate for a D/D and the track rats will figure out what works there.

While we're transferring parasitic loads to more flexible and efficient motors, let's look at the oil and water pumps. Oil pressure prior to starting sounds like a good idea. And just the right flow of oil and water for the conditions rather than for the worst case all the time will have to be more efficient.

What we're looking at is a back door hybrid.