Author Topic: Turbocharger power input (consumption)  (Read 1389 times)

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firewalker

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Turbocharger power input (consumption)
« on: March 25, 2020, 11:02:57 am »
Does anyone know what amount of power a car turbocharger need in order to spool and produce the needed pressure? Is there any first-hand rule to calculate it? E.g. a T25 turbocharger needs X amount of power input etc.

I was looking at an electrically driven turbocharger and motor was about 7 kWatt at 48 volts. The equivalent motor driver was also at that range.

Alexander.
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joeqsmith

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Re: Turbocharger power input (consumption)
« Reply #1 on: March 25, 2020, 12:39:01 pm »
Does anyone know what amount of power a car turbocharger need in order to spool and produce the needed pressure? Is there any first-hand rule to calculate it? E.g. a T25 turbocharger needs X amount of power input etc.

I was looking at an electrically driven turbocharger and motor was about 7 kWatt at 48 volts. The equivalent motor driver was also at that range.

Alexander.

There are a few turbocharger forums that would be more appropriate than one for electronics.

I've seen some stupid videos on electric turbochargers based on leaf blowers and such.  Some of these, they had their cars on some sort of roller dyno to attempt to measure the gains.   It seems there was one using gas powered leaf blowers that made some small amount of boost.

A general rule would be 1/3 goes into friction losses, 1/3 is available for work and 1/3 exits the exhaust in heat.

For an engine, the amount of charge you want to pack in there will vary.  Pump gasoline maybe they run 7PSI vs a methanol engine running at 60PSI.   The volume of air required will be dependent on the engine as well.  You can imagine if you were to pump up tires of a road bicycle to 120PSI, vs an off road at 30, which one will be more difficult to fill.  But again, I did say that a 1/3 is available at the exhaust.

If you know the flow and pressure, you could calculate the power ballpark the efficiency from the curves for your particular compressor.

In your case, 7KW / 745 is roughly 10HP.   I use small turbos like your T25 on my bike engines.  Even if these were stock, they can output more than 100HP.   That's a lot more than 7KW available to the turbocharger.

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unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #2 on: March 25, 2020, 02:30:00 pm »
Think that an ICE is typically between 30-40% efficient. So for a given power rating there is upto 70% of the actual available power of combustion going out to cooling system, friction and exhaust. I think the typical rule of thumb is that as much power as the engine produces goes out of the exhaust. So that is alot of available power for a turbo to convert, more that 7KW in almost any automotive engine and then some!  Electric turbos are just a joke, especially the early versions that used a PC fan!!!!  The electrically assisted turbos that are now being developed, actually, they might even be in use now, are a different matter.  Here, an electric motor is used to spool the turbo to minimise or even eliminate turbo lag, but the motor is not used to develop actual boost pressure.
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firewalker

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Re: Turbocharger power input (consumption)
« Reply #3 on: March 25, 2020, 02:57:51 pm »
If I understand correctly Audy uses two turbochargers. One electric and one on the exhaust manifold.  Both produce boist. The electrical one in low rpm ti fux the lag issue.

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joeqsmith

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Re: Turbocharger power input (consumption)
« Reply #4 on: March 25, 2020, 04:29:50 pm »
Garrett is apparently planning to release one next year as well.  The goal is not only to improve matching the turbo to the engine and reduce lag but to use the motor as a generator to help in recovery.    That's a big difference from having a 7KW motor trying to create boost.

Another thing we have tried was VGTs.   Around this same time, I want to say New Departure Hyatt was working on a sealed turbo that required no external oil system.   I've moved onto ceramic bearings but not to reduce the lag but rather hoping it is more forgiving with the oil system.   I saw a more recent system that did not use oil as well.  They still require water cooling but that was it.

In my particular application, lag isn't an issue.  The motor sits on a stutter box (rev limiter, low speed governor, 2-step...) with the throttle held full open.  The turbo spools up under this condition and will create 7+ PSI of manifold pressure (boost).   Once the clutch is released and the engine is no longer limited, you have all the boost you want.   I want to say it's up at full pressures in well under a half second.     If you like, I can show you plots of boost vs time from my own setup.

unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #5 on: March 25, 2020, 04:47:06 pm »
Guy in the UK, can't recall the name just now, used an interesting method of eliminating turbo lag on his Ford BDT (If I recall correctly) powered hill climb special.  He used a jet turbine APU to assist driving the turbo, so the turbo had a constant feed of exhaust gas, therefore boost was constant!!  The thing is crazy fast off the line, as it is also AWD, and everywhere else!!  Not exactly practical or fuel efficient for road use, but for it's intended use, amazing.
I've watched it run a few times and it's quite an experience, with the sound of a jet engine and a 4 cylinder turbo motor. Oh yeah, he built it all himself!!
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unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #6 on: March 25, 2020, 04:57:14 pm »
Had to find that guys name!!  Nick Mann, heres his website with full details :-

https://raceenginedesign.co.uk/the-manic-beattie/

Really interesting if you're a petrol head.
DC coupling is the devils work!!

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firewalker

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Re: Turbocharger power input (consumption)
« Reply #7 on: March 25, 2020, 05:02:47 pm »
Is the amount of power a turbocharger need the main reason for not having electrically driven turbines?

Alexander.
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unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #8 on: March 25, 2020, 05:05:15 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the sake of discussion a 2Ltr 4 cylinder unit, and you want 300 BHP using a turbo. So, ignoring all the other stuff needed to accomplish this, and all the relevant  efficiencies, losses etc etc.  In simple terms, power in = power out, so to produce that additional 100 BHP the turbo needs at least 100 BHP from the exhaust gas off the engine to do that. In practice, due to losses, efficiency, etc, etc, it needs more than that. So, more than 75 KW of energy, regardless of the turbo used.  Unless I'm getting something very wrong!
DC coupling is the devils work!!

unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #9 on: March 25, 2020, 05:06:08 pm »
Is the amount of power a turbocharger need the main reason for not having electrically driven turbines?

Alexander.

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Re: Turbocharger power input (consumption)
« Reply #10 on: March 25, 2020, 05:21:59 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the sake of discussion a 2Ltr 4 cylinder unit, and you want 300 BHP using a turbo. So, ignoring all the other stuff needed to accomplish this, and all the relevant  efficiencies, losses etc etc.  In simple terms, power in = power out, so to produce that additional 100 BHP the turbo needs at least 100 BHP from the exhaust gas off the engine to do that. In practice, due to losses, efficiency, etc, etc, it needs more than that. So, more than 75 KW of energy, regardless of the turbo used.  Unless I'm getting something very wrong!

yes you got it wrong, the turbo doesn't need 100hp to add 100hp, it needs the power required to add enough air to burn ~300hp more worth of fuel

Mazo

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Re: Turbocharger power input (consumption)
« Reply #11 on: March 25, 2020, 05:22:39 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the sake of discussion a 2Ltr 4 cylinder unit, and you want 300 BHP using a turbo. So, ignoring all the other stuff needed to accomplish this, and all the relevant  efficiencies, losses etc etc.  In simple terms, power in = power out, so to produce that additional 100 BHP the turbo needs at least 100 BHP from the exhaust gas off the engine to do that. In practice, due to losses, efficiency, etc, etc, it needs more than that. So, more than 75 KW of energy, regardless of the turbo used.  Unless I'm getting something very wrong!
To get more power you need more air/fuel mixture to burn.The turbo gets you more air than possible with NA and the FUEL gets you the energy input.Following your line of reasoning a supercharger(driven by the engine by a belt in most cases) is a completely useless device as it will take 100hp to "give"100hp,and yet superchargers exist and are useful.As langwadt says it seems you are getting it wrong.

By the way I once made a rough calculation on the power needed for a pretty small boost of 0.3bar on a 1.6L engine and the number I got was around the 5kW mark of electrical power needed.Very difficult to supply on 12V and by a standard alternator.

firewalker

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Re: Turbocharger power input (consumption)
« Reply #12 on: March 25, 2020, 06:00:16 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the
By the way I once made a rough calculation on the power needed for a pretty small boost of 0.3bar on a 1.6L engine and the number I got was around the 5kW mark of electrical power needed.Very difficult to supply on 12V and by a standard alternator.

Did you just calculated the mass and the speed of air per second? I did that and my result same as yours.

Alexander.
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joeqsmith

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Re: Turbocharger power input (consumption)
« Reply #13 on: March 25, 2020, 06:10:40 pm »
Because it was brought up:

https://itstillruns.com/honda-gx140-specifications-7661089.html

About 1000HP to turn the blower (supercharger) on a T/F car.   One sport you need to be there, in person to appreciate what a 10KHP car does.

Had to find that guys name!!  Nick Mann, heres his website with full details :-

https://raceenginedesign.co.uk/the-manic-beattie/

Really interesting if you're a petrol head.

Thanks for the link.   I've never seen or heard of this.    A good read and a couple of nice videos on YT.

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joeqsmith

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Re: Turbocharger power input (consumption)
« Reply #14 on: March 25, 2020, 07:24:33 pm »
First Google hit, finds your question and even mentions the T25.   Gotta love these modern search engines.

I'm a member on this forum but not very active but it is a very good source of information.

joeqsmith

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Re: Turbocharger power input (consumption)
« Reply #15 on: March 25, 2020, 07:41:15 pm »
Scan down a couple of posts and you can see some data I posted from one of my bikes showing the lag.

Mazo

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Re: Turbocharger power input (consumption)
« Reply #16 on: March 25, 2020, 07:45:40 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the
By the way I once made a rough calculation on the power needed for a pretty small boost of 0.3bar on a 1.6L engine and the number I got was around the 5kW mark of electrical power needed.Very difficult to supply on 12V and by a standard alternator.

Did you just calculated the mass and the speed of air per second? I did that and my result same as yours.

Alexander.
Yes but I also took compressor efficiency(increase in power needed) and volumetric efficiency(decrease in power needed) of the engine into account(you can say they cancel out if you got an efficient compressor).
Thought about modding a car with such a supercharger(I call it a supercharger as  the plan was to supply it with electricity using a belt driven alternator),while thinking that a boost available from ~idle will make for a really flat torque curve.TL;DR it isn't as useful as one might think,and it still comes worse power and money-wise than driving a normal supercharger by mechanical means.
I was considering the idea from performance standpoint and it seems it is a no go.
AFAIK the electric compressors are made so one can pass the emissions regulations of the future.
Ofcourse impemented the way garett will do it,enables them to function as normal turbochargers at higher RPM and even regenerate the energy of the exhaust gases to charge batteries,at the same time eliminating turbo lag from big turbos bolted on cars with the displacement of a soda bottle .
All in all if you don't use the exhaust gas at all the idea is terrible.(can't say I wasn't excited doing all the math to prove my gutsense is right)
P.S If someone has an example that proves otherwise,I would be very interested so PM me.
« Last Edit: March 25, 2020, 07:48:11 pm by Mazo »

unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #17 on: March 25, 2020, 07:49:46 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the sake of discussion a 2Ltr 4 cylinder unit, and you want 300 BHP using a turbo. So, ignoring all the other stuff needed to accomplish this, and all the relevant  efficiencies, losses etc etc.  In simple terms, power in = power out, so to produce that additional 100 BHP the turbo needs at least 100 BHP from the exhaust gas off the engine to do that. In practice, due to losses, efficiency, etc, etc, it needs more than that. So, more than 75 KW of energy, regardless of the turbo used.  Unless I'm getting something very wrong!
To get more power you need more air/fuel mixture to burn.The turbo gets you more air than possible with NA and the FUEL gets you the energy input.Following your line of reasoning a supercharger(driven by the engine by a belt in most cases) is a completely useless device as it will take 100hp to "give"100hp,and yet superchargers exist and are useful.As langwadt says it seems you are getting it wrong.

By the way I once made a rough calculation on the power needed for a pretty small boost of 0.3bar on a 1.6L engine and the number I got was around the 5kW mark of electrical power needed.Very difficult to supply on 12V and by a standard alternator.

Superchargers do work but are inefficient as they are parasitic devices, so they require mechanical power from the engine to drive them.  For that reason they never even get near the capability of turbos.  They are typically used for low boost applications.  Top fuel drag racing doesnt count!!!
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unknownparticle

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Re: Turbocharger power input (consumption)
« Reply #18 on: March 25, 2020, 07:54:26 pm »
Just another thought on the power required by a turbo to provide useful boost pressure.  Say you have a NA engine producing 200 BHP, for the sake of discussion a 2Ltr 4 cylinder unit, and you want 300 BHP using a turbo. So, ignoring all the other stuff needed to accomplish this, and all the relevant  efficiencies, losses etc etc.  In simple terms, power in = power out, so to produce that additional 100 BHP the turbo needs at least 100 BHP from the exhaust gas off the engine to do that. In practice, due to losses, efficiency, etc, etc, it needs more than that. So, more than 75 KW of energy, regardless of the turbo used.  Unless I'm getting something very wrong!

yes you got it wrong, the turbo doesn't need 100hp to add 100hp, it needs the power required to add enough air to burn ~300hp more worth of fuel

Well, yes, but the fuel requires the correct amount of air for it to burn at the correct AFR. To provide that air the turbo has to compress the atmospheric air to the necessary pressure to provide the CFM flow to burn the fuel. So, power in = power out, to compress the air AND at the necessary CFM, the turbo has to be powered from the exhaust gas flow of the engine.
DC coupling is the devils work!!

mzzj

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Re: Turbocharger power input (consumption)
« Reply #19 on: March 25, 2020, 08:15:37 pm »
Is the amount of power a turbocharger need the main reason for not having electrically driven turbines?

Alexander.
Yes, that is THE reason.
Heavily boosted 2.3L turbo engine with ~450 hp output needs 70hp power on compressor shaft.
Borgwarner matchbot shows "turbo shaft power" , this is a 2.3L ethanol(E85) fueled example:

http://www.turbos.bwauto.com/aftermarket/matchbot/index.html#version=1.4&displacement=2.3&CID=140.346&altitude=500&baro=14.502&aat=75&fueltype=3&turboconfig=1&compressor=67x80&pt1_rpm=2500&pt1_ve=88&pt1_boost=13&pt1_ie=99&pt1_filres=0.08&pt1_ipd=0.2&pt1_mbp=0.5&pt1_ce=66&pt1_te=85&pt1_egt=1450&pt1_ter=1.48&pt1_pw=16.27&pt1_bsfc=0.62&pt1_afr=9&pt1_wts=300&pt1_wd=83&pt1_wd2=74&pt1_wrsin=69033&pt2_rpm=3000&pt2_ve=95&pt2_boost=22&pt2_ie=95&pt2_filres=0.1&pt2_ipd=0.2&pt2_mbp=1&pt2_ce=70&pt2_te=83&pt2_egt=1550&pt2_ter=1.87&pt2_pw=25.72&pt2_bsfc=0.68&pt2_afr=8&pt2_wts=320&pt2_wd=83&pt2_wd2=74&pt2_wrsin=73635&pt3_rpm=4000&pt3_ve=100&pt3_boost=21&pt3_ie=95&pt3_filres=0.12&pt3_ipd=0.3&pt3_mbp=1.3&pt3_ce=74&pt3_te=72&pt3_egt=1650&pt3_ter=2.11&pt3_pw=36.22&pt3_bsfc=0.68&pt3_afr=8&pt3_wts=340&pt3_wd=83&pt3_wd2=74&pt3_wrsin=78238&pt4_rpm=5000&pt4_ve=95&pt4_boost=23&pt4_ie=92&pt4_filres=0.15&pt4_ipd=0.4&pt4_mbp=1.5&pt4_ce=76&pt4_te=71&pt4_egt=1650&pt4_ter=2.37&pt4_pw=40.62&pt4_bsfc=0.68&pt4_afr=8&pt4_wts=368&pt4_wd=83&pt4_wd2=74&pt4_wrsin=84681&pt5_rpm=6000&pt5_ve=90&pt5_boost=27&pt5_ie=90&pt5_filres=0.18&pt5_ipd=0.5&pt5_mbp=1.8&pt5_ce=72&pt5_te=70&pt5_egt=1650&pt5_ter=2.88&pt5_pw=40.24&pt5_bsfc=0.7&pt5_afr=8&pt5_wts=400&pt5_wd=83&pt5_wd2=74&pt5_wrsin=92044&pt6_rpm=7000&pt6_ve=80&pt6_boost=27&pt6_ie=90&pt6_filres=0.2&pt6_ipd=0.6&pt6_mbp=2&pt6_ce=70&pt6_te=70&pt6_egt=1650&pt6_ter=2.96&pt6_pw=39.64&pt6_bsfc=0.72&pt6_afr=8&pt6_wts=400&pt6_wd=83&pt6_wd2=74&pt6_wrsin=92044&

We considered adding 48v system and electric charger to that motor but 7kW electric turbo was marginal even to cover the low end before the larger turbo wakes up. For smaller engine or milder tune the electric turbo would cover the low rpm boost just fine. (Like in some Audi models)

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Circlotron

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Re: Turbocharger power input (consumption)
« Reply #20 on: March 25, 2020, 08:31:48 pm »
Ages ago I did a rough calc for a 3 litre engine at 6000rpm with 1 bar boost and I got about 30kW needed to drive the turbo’s compressor. Many of the tricky words used in thermodynamics make my head spin, but I reckon the figure is within +/- 20% of correct.

Edit -> maybe half that figure. See my later post.

https://www.eevblog.com/forum/chat/turbocharger-power-input-(consumption)/msg2983598/#msg2983598
« Last Edit: March 26, 2020, 09:59:20 pm by Circlotron »

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Mazo

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Re: Turbocharger power input (consumption)
« Reply #21 on: March 25, 2020, 08:43:39 pm »
Ages ago I did a rough calc for a 3 litre engine at 6000rpm with 1 bar boost and I got about 30kW needed to drive the turbo’s compressor. Many of the tricky words used in thermodynamics make my head spin, but I reckon the figure is within +/- 20% of correct.
1bar of boost on a pretty normal 3L petrol not really fancy engine gets you in the 350-420hp range easily,while the same not really fancy 3L engine has about 200-250HP that is say a 200hp gain for a say 60hp loss(for a supercharger and some driving loss added that's it).
Real life example->M112 the 3.2L NA vs the supercharged version(the engine from the W203 C32AMG).
NA-220hp vs 1bar boost coming from a supercharger for 354hp
So yes power in=power out only if you apply it correctly
« Last Edit: March 25, 2020, 08:48:51 pm by Mazo »

Circlotron

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Re: Turbocharger power input (consumption)
« Reply #22 on: March 25, 2020, 08:47:57 pm »
Also, I wouldn’t say the power to drive a turbo is free. If you have pressure at the compressor outlet then you are also going to have pressure at the exhaust turbine inlet. This exhaust back pressure is something the rising piston has to push against on the exhaust stroke, therefore stealing crankshaft power. Of course, this might be partially countered by the inlet boost pressure helping to force the piston down on the inlet stroke. To get it right is engineer’s stuff, not a shade tree mechanic.

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Re: Turbocharger power input (consumption)
« Reply #23 on: March 25, 2020, 09:38:41 pm »
Also, I wouldn’t say the power to drive a turbo is free. If you have pressure at the compressor outlet then you are also going to have pressure at the exhaust turbine inlet. This exhaust back pressure is something the rising piston has to push against on the exhaust stroke, therefore stealing crankshaft power. Of course, this might be partially countered by the inlet boost pressure helping to force the piston down on the inlet stroke. To get it right is engineer’s stuff, not a shade tree mechanic.

it is not quite so simple, the turbine is driven by the kinetic energy of the exhaust stream not just pressure

Circlotron

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Re: Turbocharger power input (consumption)
« Reply #24 on: March 25, 2020, 10:32:41 pm »
it is not quite so simple, the turbine is driven by the kinetic energy of the exhaust stream not just pressure
It sure isn't simple! I've often wondered about the effect of having a large plenum right at the inlet to the turbine similar to one commonly used at the compressor outlet where the inlet pipes branch from. That would spread and reduce the amplitude of the kinetic energy of the pulsating waves to more of a smooth flow, similar to the effect of a series choke with rectified DC current flow. The turbo might have to be resized to suit the new circumstances, but I wonder if there would be any benefit. Somewhat similar to a transformer not having to handle the peak currents of a capacitor input filter? Far fetched maybe, but sometimes physics has some interesting parallels.

Smf