# EEVblog Electronics Community Forum

## General => General Chat => Topic started by: firewalker on March 25, 2020, 11:02:57 am

Title: Turbocharger power input (consumption)
Post by: firewalker 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.
Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith 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.
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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.
Title: Re: Turbocharger power input (consumption)
Post by: firewalker 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.

Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith 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.
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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!!
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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.
Title: Re: Turbocharger power input (consumption)
Post by: firewalker 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.
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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!
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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.

Title: Re: Turbocharger power input (consumption)
Post by: langwadt 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

Title: Re: Turbocharger power input (consumption)
Post by: Mazo 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.
Title: Re: Turbocharger power input (consumption)
Post by: firewalker 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.
Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith 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.
Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith 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.  :-DD

I'm a member on this forum but not very active but it is a very good source of information.
Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith 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.

Title: Re: Turbocharger power input (consumption)
Post by: Mazo 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.
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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!!!
Title: Re: Turbocharger power input (consumption)
Post by: unknownparticle 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.
Title: Re: Turbocharger power input (consumption)
Post by: mzzj 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& (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)
Title: Re: Turbocharger power input (consumption)
Post by: Circlotron 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 (https://www.eevblog.com/forum/chat/turbocharger-power-input-(consumption)/msg2983598/#msg2983598)
Title: Re: Turbocharger power input (consumption)
Post by: Mazo 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 :)
Title: Re: Turbocharger power input (consumption)
Post by: Circlotron 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.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt 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
Title: Re: Turbocharger power input (consumption)
Post by: Circlotron 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.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 25, 2020, 10:58:12 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.

kinetic energy is velocity squared so I think it'll reduce power

Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith on March 25, 2020, 11:04:25 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.

I try to match this at 1:1.   So 30 PSI on the intake, 30 PSI in the exhaust.   To measure the exhaust pressure,  I use about a foot of stainless tubing to connect the sensor.

With higher pressures, I have had the valves want to open.   Of course there have been many other problems to solve along the way.
Title: Re: Turbocharger power input (consumption)
Post by: NiHaoMike on March 25, 2020, 11:11:54 pm
In the realm of racing, how does a turbocharged/supercharged engine compare to a jet engine?
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 25, 2020, 11:38:58 pm
In the realm of racing, how does a turbocharged/supercharged engine compare to a jet engine?

jet engines are  powerful for their size and weight, but thirsty and only really efficient at +90% power

Title: Re: Turbocharger power input (consumption)
Post by: joeqsmith on March 26, 2020, 12:04:38 am
In the realm of racing, how does a turbocharged/supercharged engine compare to a jet engine?

You saw a lot more innovation back then.
Title: Re: Turbocharger power input (consumption)
Post by: Someone on March 26, 2020, 12:18:01 am
In the realm of racing, how does a turbocharged/supercharged engine compare to a jet engine?
Mechanically they have a lot of similarities. Scrapheap challenge showed at least 2 DIY jet engines based around turbochargers:
https://youtu.be/z0iigOmActU
https://youtu.be/9GCBCdMOFpE
Rudimentary antilag systems basically use the turbo directly as a jet engine...

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!!
Antilag has many implementations:
https://en.wikipedia.org/wiki/Antilag_system
Title: Re: Turbocharger power input (consumption)
Post by: Circlotron on March 26, 2020, 01:09:20 am
I try to match this at 1:1.   So 30 PSI on the intake, 30 PSI in the exhaust.
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. A 1:1 pressure ratio wouldn't work very well for a turbo converted to a jet engine though! Inlet pressure would have to be higher than exhaust for the air + fuel to flow in the right direction. I've heard a single turbo with no air filter on an 855hp V8 on a dynamometer from a distance of about 20 metres. That convinced me that there was plenty of action going on! Living proof of advances in material science.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 26, 2020, 01:51:20 am
I try to match this at 1:1.   So 30 PSI on the intake, 30 PSI in the exhaust.
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. A 1:1 pressure ratio wouldn't work very well for a turbo converted to a jet engine though! Inlet pressure would have to be higher than exhaust for the air + fuel to flow in the right direction. I've heard a single turbo with no air filter on an 855hp V8 on a dynamometer from a distance of about 20 metres. That convinced me that there was plenty of action going on! Living proof of advances in material science.

modern efficient turbofans are more like 40-50:1, a 50 year old turbojet ~12:1
Title: Re: Turbocharger power input (consumption)
Post by: firewalker on March 26, 2020, 08:02:10 am
For an EE forum we are doing pretty well! I guess engineering is engineering! :D :D :D

Alexander.
Title: Re: Turbocharger power input (consumption)
Post by: mzzj on March 26, 2020, 08:19:45 am
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.
Bad business, you want to keep the exhaust gas as hot as possible and large plenum would be difficult to insulate. (hot gas is flowing faster and energy is lost when it cools down)
If you google "twin scroll turbocharger" it has almost opposite idea, maintain the kinetic energy and pressure spikes from each cylinder as well as possible.
Title: Re: Turbocharger power input (consumption)
Post by: firewalker on March 26, 2020, 12:34:31 pm
With many assumption made. A 2000 cm3 engine at 6000 RPM with a "pump" driving the intake at 0.5 bar (50000 Pa). Every revolution the engine needs 1000 cm3 of air. This means 50000 cm3 or 0.05 m3  every second. The power the fluid takes from the pump is P=0.05*50000 = 2500 Watt.

This is without taking in account the vacuum of the engine that the pump should overcome. This means that the pressure differential is in reality 1.5 bar or more for 0.5 pressure. And is just the power of the fluid.

Alexander.
Title: Re: Turbocharger power input (consumption)
Post by: SilverSolder on March 26, 2020, 01:11:04 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.

Batshit crazy.  Love it!  :D
Title: Re: Turbocharger power input (consumption)
Post by: Circlotron on March 26, 2020, 09:52:50 pm
Okay, back to the original topic.
Let’s try it again for a 3 litre engine at 6000rpm with 15 psig. Instead of a turbo, say our compressor is a very long cylinder and piston with a cross sectional area of 1/15 square inch. That means this piston needs 1 pound force against 15 psi. The engine will consume 9000 litres per minute of air, but at double normal density. 9,000,000,000 cubic mm. The piston in our long compressor cylinder has a surface area of 1/15 sq  inch or 43 sq mm so to displace 9G cubic mm per minute it would move at 9G/43 = 209,302,325 mm per minute or 686,687 feet per minute, against 1 pound force, so 686,687 foot pounds per minute. 686,687/33,000 = 20.8hp = 15.52kW. That’s pretty simplistic, but it’s a starting point.
Title: Re: Turbocharger power input (consumption)
Post by: james_s on March 26, 2020, 10:23:55 pm
The whole point of a turbocharger is that it recovers otherwise wasted energy from the exhaust and uses that to drive the compressor wheel that supercharges the engine. If you want to know how much energy that takes, you'd likely have more luck looking at engine driven superchargers as the parasitic load they draw is likely to be better documented.

I don't know how well it translates to car sized engines but I recall reading that the supercharger used on the RR Merlin aircraft engine draws about 500HP from the crankshaft so the ~1300HP engine was actually producing closer to 1800HP. A mechanically driven supercharger is simpler, easier to build and cheaper but the fact that a turbocharger uses mostly otherwise wasted energy makes it significantly more efficient.
Title: Re: Turbocharger power input (consumption)
Post by: james_s on March 26, 2020, 10:26:10 pm
https://en.wikipedia.org/wiki/Antilag_system

I actually kind of like the lag in my old Volvo, that kick in the pants when the turbo finally spools up is a lot of fun, it's like the whole car suddenly wakes up and leaps forward.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 26, 2020, 10:58:04 pm
Okay, back to the original topic.
Let’s try it again for a 3 litre engine at 6000rpm with 15 psig. Instead of a turbo, say our compressor is a very long cylinder and piston with a cross sectional area of 1/15 square inch. That means this piston needs 1 pound force against 15 psi. The engine will consume 9000 litres per minute of air, but at double normal density. 9,000,000,000 cubic mm. The piston in our long compressor cylinder has a surface area of 1/15 sq  inch or 43 sq mm so to displace 9G cubic mm per minute it would move at 9G/43 = 209,302,325 mm per minute or 686,687 feet per minute, against 1 pound force, so 686,687 foot pounds per minute. 686,687/33,000 = 20.8hp = 15.52kW. That’s pretty simplistic, but it’s a starting point.

it is a starting point, some of the pressure would come from the increase in temperature

https://checalc.com/calc/compress.html

Title: Re: Turbocharger power input (consumption)
Post by: JPortici on March 27, 2020, 07:26:22 am
Is the amount of power a turbocharger need the main reason for not having electrically driven turbines?

Alexander.
a conventional exhaust driven turbocharger in full power turns at 100k+ RPM and at the same time is way hotter than 150 °C :) that will add some complexity
Title: Re: Turbocharger power input (consumption)
Post by: tautech on March 27, 2020, 08:18:56 am
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

Some good general reading on turbochargers are books by Hugh MacInnes from way back in the 80's.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 27, 2020, 09:05:37 am
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
Title: Re: Turbocharger power input (consumption)
Post by: tautech on March 27, 2020, 09:14:39 am
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold.
It uses a separate piped connection and valving to accomplish it.

EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses.
Title: Re: Turbocharger power input (consumption)
Post by: langwadt on March 27, 2020, 09:37:52 am
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold.
It uses a separate piped connection and valving to accomplish it.

EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses.

yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand

Title: Re: Turbocharger power input (consumption)
Post by: tautech on March 27, 2020, 09:41:02 am
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold.
It uses a separate piped connection and valving to accomplish it.

EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses.

yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand
Some don't give a damn about emissions !  :-DD

(https://bloximages.chicago2.vip.townnews.com/newsbug.info/content/tncms/assets/v3/editorial/a/ee/aee85789-5d1d-5420-b013-64d6d1a6c751/5b5006eb2e372.image.jpg?resize=951%2C650)

Title: Re: Turbocharger power input (consumption)
Post by: SilverSolder on March 27, 2020, 04:27:00 pm
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold.
It uses a separate piped connection and valving to accomplish it.

EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses.

yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand

EGR can be disabled by the computer during peak demand input (mashing the pedal to the metal).  The rest of the time, during normal driving, the emissions are then safely lowered with EGR without impacting performance.
Title: Re: Turbocharger power input (consumption)
Post by: tautech on March 27, 2020, 06:02:27 pm
I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap.
Exactly this is the great advantage with turbo'ed diesels. The proper cylinder scavenging promotes cleaner and better burns.

if efficiency was the only object maybe

but exhaust gas recirculation to reduces the amount oxygen to reduce the amount of NOx. and since diesels
always run with excess oxygen in the exhaust a three-way catalyst won't work to reduce NOx so you need things like Adblue
EGR is something completely different where a portion of exhaust gasses are diverted into the intake manifold.
It uses a separate piped connection and valving to accomplish it.

EGR is quite different to engine valve overlap where boost pressure can momentarily pass from intake to exhaust when the valve timing overlaps and in doing so scavenges the combustion chamber of any remaining exhaust gasses.

yes EGR is the exact opposite. So why would it be and advantage to scavenge any remaining exhaust gasses only to add it back via the intake to meet emissions demand

EGR can be disabled by the computer during peak demand input (mashing the pedal to the metal).  The rest of the time, during normal driving, the emissions are then safely lowered with EGR without impacting performance.
Little do you know of the negative effects on an engine of EGR in its attempt to mitigate emissions.
Special oils had to be developed that better withstand the exhaust contaminants recycled through the engine that decimated ordinary diesel engine oil life and risked engine damage.

There are many tricks to disable EGR that monitoring systems do not see.  ;)
Title: Re: Turbocharger power input (consumption)
Post by: james_s on March 27, 2020, 06:43:20 pm
EGR has benefits but it is certainly not without problems. It tends to really gum up intake manifolds, and I've had the EGR valves themselves get gummed up and stick. The crankcase vapor recovery also makes a mess of intakes, covering everything with hard black crust.
Title: Re: Turbocharger power input (consumption)
Post by: tautech on March 27, 2020, 07:03:12 pm
EGR has benefits but it is certainly not without problems. It tends to really gum up intake manifolds, and I've had the EGR valves themselves get gummed up and stick. The crankcase vapor recovery also makes a mess of intakes, covering everything with hard black crust.
Another factor that further adds to intake gumming is the tiny oil leakage from turbo seals and when added to crankcase vapor and exhaust soot further exacerbates intake manifold deposits that in the longer term impact of motor performance by not letting it breathe properly.

Modern advancements in EFI and common rail injection systems have much reduced the need for EGR based emission control.