how much power does a turbo make
 

So I have been throwing out some thoughts with friends of mine and have been encouraged with the efficiency of my last turbo charged small car. (1992 plymouth laser) It made me wonder how much power is in that turbo when it spools up.

I am not talking about using it to make a super eco mod, I am thinking of using a turbo for a different purpose.

Can anyone tell me basics on how to figure out how much power a turbo is actually producing so I can apply it to something more fun :)

When my smaller turbo was all buy its self my smaller it ran at a peak of about 40hp.
I only ran it at 1/3 of its rated capacity.

There is nothing better a turbo can do than force air into a diesel engine.

It's not the turbo that gives extra power. It's the air forced to the combustion chamber. So it's very simple more air + more fuel (to have decent air to fuel mixture) equals to more power. Actually connecting turbo to the exhaust decrease power of the engine, by restricting exhaust flow. Forced induction gives you more power that turbo is consuming so the overall power is higher than without turbo. Of course when turbo is spinning with the right speed. If not you have turbo lag when engine is weaker than similar naturally aspirated engine.
That's why you can't get straight answer to your question. There's too many variables in the equation. Turbo can easily double the engine's power or triple it, if the engine will handle such power. Most of the engines will handle 20-30% of power increase without other mods. If you plan more power you may need to rebuild your engine with new pistons, connecting rods, maybe even crankshaft. It's cheaper to swap more powerful engine than rebuild old one for more power. But it's a great fun to build one though :)

I would be curious to know how much horsepower a turbo generates at the turbine shaft.

For the OP. A very cool on line tool to use running different turbo scenarios is Matchbot by Borg Warner.
Performance Turbos | TurboDriven.com - BorgWarner Turbo Systems

It has lots of info and gives turbo shaft power also.

Check out the online tutorial or if you have any questions feel free to let me know.

Interesting question... :)

This is not true with diesels. I have not touched the fuel injection rate or amount on my mechanical injected diesel. But after I installed the turbo on my non-turbodiesel I had much more power and +2mpg with the same fuel.

One of the very cool things F1 is doing next year is there new turbo DI V6 engines. The new 2014 F1 engines will have a MGHU (Motor Generator Heat Unit) that will produce electricity for storage and on demand power through a MGU-K unit (120kW max) added to the ICE power unit with the engine at a fuel limited max of 100kg/hr.

These new engines will be more of a N/A DI version with state of art fuel
"spray guided direct injection". So they will have the efficiency of today's N/A engines with the power of a turbo charger. The turbo will not just add power but also will help with engine delta p. I think we will see some of the most advance BSFC to date.

This could be a game changer as far as what it will bring to the OEM level. Just last week Honda said they are going to get involved.

Visit the MatchBot link I provided for the answer.

Yeah, it is true. There is power required to spin the turbo charger, that has to come from the engine. People always think it's just "Waste Gas", but it isn't. There is a load placed on the engine to make the turbo charger spin, if you just let the air blow into the open by not hooking it up to your engines air induction, it would really slow you down. But since it is packing in a lot of air into your engine, the net gain is that it does help, you're MPG increase is due to the turbo allowing you to operate in a better region of the BSFC chart for your engine. This is basic turbo charger stuff.

You don't get something for nothing, but the benefits outweigh the losses in this case. It is understandable for you to think as you do, but it is not accurate.

This is a tricky question. The turbo is generating shaft hp, but, it is using that hp to stuff more air into the intake. If something else is done with that power, the engine will have a substantially reduced power output, which means that turbo won't spin as hard.

The bottom line here is that spinning a turbo to do anything other than stuff air into the intake is kind of dumb. Perhaps taking a small amount of the power off and further reducing the exhaust restriction to compensate may make some sense, but, I kind of doubt it.

At very light loads maybe. Current turbochargers use a waste gate to dump excess exhaust gas around the turbocharger once the desired boost (compressor work) is achieved. There's still plenty of energy available in the exhaust that is being routed around the turbine.

Since about 1/3 of the energy in the fuel goes out the exhaust and ~1/3 ends up available for useful work, in theory there's as much power in the exhaust energy as the engine achieves at the flywheel. At least some of that energy could be used to drive an electrical generator connected to an exhaust gas driven turbine.

If you replaced the engine with a combustion chamber that generated exhaust gas with the same temperature and pressure as that past the engine's exhaust valve, the gas would still drive the turbine. The engine isn't driving the turbine by acting solely as a compressor on the exhaust gas.

There is also that the exhaust valve(s) are operating in choked flow at least part of the time. When that is occurring you can do whatever you like downstream of the exhaust valve, even pull it down to a perfect vacuum, and not increase the mass flow rate of the air past the exhaust valve(s).

That means it is possible to increase the exhaust gas pressure between the exhaust valve and turbine, via the restriction caused by the turbine, and not necessarily reduce the flow past the exhaust valve(s).

What size turbo what psi are you running? A stock mode 90s Volvo was like 110 hp the same motor with a Garret t3-4 well close to it running 7.5 psi boost stock form was like 150 hp. Honda guys turbo the 1.5 1.6 liter motors 110-125 stock and push 400+ hp. So way to many variables. You can tweak the psi to make more power but then there is also spool time little turbo quick spool overall lower psi capability. Big turbo long spool up time but high psi 20+. So run two a little and a big no lag and big top end. Volvo s80 turbos use that set up. So you need to clue us in what the goal is you could also build a jet engine out of a turbo.

I don't have any actual stats, but, I believe that statement is backwards. I believe that a properly sized turbo uses its waste gate only at high loads.

There is one other problem here. How do you harness power from a device that is spinning at crazy rpms and is very hot? You do it with a rather complicated transmission that will cause turbo lag like you've never seen.

The bottom line is that yes, there is some wasted energy here, but harnessing it is gonna be awfully tricky if possible at all.

Sorry Pete he is right. A properly size turbo will run a smaller size turbine then needed to keep turbo lag at a minimum. So the waste-gate will open at lower loads to keep from over boost. If you turn the boost up there will be less waste-gate flow. Check out the MatchBot link and notice the waste-gate flow at 17psi @ 7000rpm then turn it up to 22psi and adjust the turbine expansion ratio to the original turbine phi curve. You will see that a higher boost will have less % waste-gate flow.

As far as the turbine not being able to do anything useful then spin a compressor wheel and add flow. Check out what F1 is doing for the 2014 season.
Renault takes lid off of 2014 F1 turbo engine - F1technical.net

They are using the turbo to make power and taking some of the turbine flow that would normally be dumped out the waste-gate and harness it through a generator unit. The electricity can be used on demand or sent into a battery/capacitor system for later use or to be used to spin the turbo if needed for no-lag.

It is waste gas.
Before the turbo went on I was blowing 1,100'F exhaust out the engine, just to maintain speed.
Now that burned fuel that was getting blown out the exhaust is being put to work. When installing a turbocharger on a diesel you are doing no less than adding a second engine under the hood.
That added power and fuel economy isn't what anyone would call "getting something for nothing". You have to buy and install the turbocharger, its expensive, a great deal of work and you are cramming 40 to 80 pounds of extra equipment under the hood.
I rewrote the BSFC chart. Still putting the same load at the same speed on the engine.

Yes this is correct.
I don't not use a waste gate. I limit boost by over sizing the turbo a bit and by fueling then making sure the engine can take the amount of boost it gets fed.
On a gas engine this isn't really an opption.

Compound turbos have been used a lot. They use the turbine shaft to mechanically drive the load, parallel with the flywheel. Lots of WWII airplane engines used them.
Until recently, Detroit Diesel 15L engines had a compound turbo that drove the gear train, but it seems they have ditched it now. There's probably a good reason for it.

EDIT: The DD16 (600 HP) still uses turbo compounding.
http://www.demanddetroit.com/engines/dd16/default.aspx

How do airplanes harness power from turbojet engines? Which are, after all, basically scaled-up turbochargers pushing bypass air out the back end instead of stuffing it in the cylinders of an IC engine.

Simplest answer is that you don't do it mechanically at all. Turbine shaft is mated to the rotor of an alternator, which generates electricity. By switching the alternator so it only generates at higher exhaust flow, you pretty much eliminate any excess turbo lag. If you happen to have a hybrid, you can store the electricity for later use...

Can an alternator handle the kind of revs it would see bolted directly to a turbo? Perhaps it can, but, I suspect it would be a damn expensive alternator.

Compound turbos do it mechanically through a gear set. The DD16 in my link above does, as did all the WWII airplane engines.

Isn't that what I said? Reread my post in the context of the post I was replying to.

It's really interesting to play around with the variables in the MatchBot page pgfpro provided the link to.

In addition to the turbo compounding (geared to the crankshaft) and turboprop aircraft, that problem has been solved in every gas or steam turbine power station.

If lag is an issue, there's no reason, other than conversion efficiencies, why electrical energy can't go both ways, whichever is appropriate at the time.

It will cost money to do it but it has been tried:

AutoSpeed - HyBoost

Sure, it CAN be done that way, at the cost of adding weight, complexity, and wear/failure points. That might not matter much for combat aircraft - after all, the average service life of a B-17 in combat was something like 4 months.

The amusing part is the research done after the war to discover the most efficient size of turbocharger for a given piston engine. Turned out the optimum was to reduce the size of the engine to zero.

No its not true. If you pack more air into the cylinder it and supply the same amount of fuel the resultant combustion gases are cooler because of the excess air. The end result is less heat energy lost to the cooling system and more energy in the combustion gases that can be extracted by the piston. Also a turbo that is properly matched at a load point and rpm will generate more pressure in the intake manifold than in the exhaust manifold.

Here is what you said.

The way I read that, you are saying that anything above "very light loads" results in waste gate bypass.

This very well might be the case, but, I kind of doubt it. My thought was that the waste gate only came into use at high loads.

Perhaps you are right, as I make no claims to being anything remotely close to a turbo expert.

As for aircraft applications, lag is not an issue as engines are run at relatively stable rpms. Also, these engines spend a lot of time near max power. An aircraft engine really is an entirely different animal.

C'mon people, listen to yourselves, you sound like a bunch of HHO proponents with "Cooler Gases" with "More Energy" WTH??

Bottom line, think about this, The discussion was started based on the question "How much horsepower a turbo generates at the turbine shaft?"

Who here said None? No horsepower? I'm guessing nobody. So if there is horsepower being generated by the turbine, it has to come from somewhere, and I don't think anybody is going to say it isn't coming from the engine.

Now I completely understand that if the turbocharger is using say 5HP, the net effect of it packing in more air is going to be an additional 10-20HP or something, resulting in a net gain in HP. Great. Works as advertised.

How it improves fuel efficiency? I'm not real clear on these nuances, but I don't dispute they do.

What I do dispute, is the notion that the turbocharger is running on magic fairy dust to make it propel the compressor which requires a fairly substantial amount of energy in order to raise the pressure of a large volume of air.

The energy comes from somewhere, and it is the engine. Net Gain, Yes, all day. But the turbocharger is using power to make power, and the power used is not "free".

It's only free in the sense that it's power that isn't being used for anything.

It's likely you would only have excess boost pressure to bleed off to produce electricity at very high engine speeds. If you're getting excess at moderate or low speeds, then you have a poorly sized turbo and you're throwing a lot of energy away, in the first place. Hybrid-electric turbochargers that generate electricity only make power at high engine speeds, and use it at low engine speeds. As a means to increase efficiency, it doesn't seem very efficient for ecomodders who tend not to drive flat out.

Also, looking at the diagrams and what goes into making power-generating turbos, seems like a lot of work for recovering what is potentially a few measly horsepower from the tiny turbine you would attach to a car engine. And that's before you go through the losses in converting it back to electricity. Would make more sense to simply have the turbine properly sized, in the first place, or to use a variable-geometry unit, instead.

This kind of thing makes sense on the industrial level or with ships, which have huge turbochargers, but on cars... I don't see the benefit.

That's an interesting Autospeed article.

Here's what BMW patented

They use three turbos; the electric turbo is to control lag. Most of the time it's feeding the battery/ultracapacitor.

You think wrong. It is not coming from the engine, in the sense that it is robbing power that would otherwise go to the wheels. It is using the energy in the hot exhaust gas, which otherwise would just go right out the tailpipe.

I'll say power is not coming from the engine.

The energy comes from the fuel, not the engine. The engine and the turbo convert this energy to usable work. There is no rule in thermodynamics forbidding use of a turbo to improve the efficiency of an engine.

I love this thread. :)

Could you explain how this works please, or point me to a website that says this and explains it.

If you read what I wrote, I said the turbocharger improves the efficiency of the engine several times. So why do you write this?

For a simple thought experiment, consider eliminating the engine, and spinning the turbocharger with a stream of hot gas generated by burning some sort of fuel. That's fairly easily done. There are lots of examples on the web, starting with this: The Junkyard Turbojet Engine - A Real Working Jet Engine Built From Junkyard Parts (The first hit of 2.4 million.)

So this can hardly be robbing power from the engine, since there is no engine.

Well James. It looks like to me you just said you need energy to run the turbocharger in the form of burning fuel. So, the turbine side of the turbocharger you admit needs power. I understand we burn fuel in our engines, pretty basic stuff. But when it leaves the engine on a normally aspirated engine, it just goes out the exhaust pipe fairly freely. Lets for grins say that it is at 1psi at the exhaust manifold. If there is a restriction in the exhaust system like say...A Turbocharger....then the pressure is going to rise in the exhaust manifold to say 3psi. This pressure and restriction WILL place a load on the engine, requiring more power from the engine in order to operate. That is where the power is coming from, our engines are big air pumps, and if you restrict the flow on the outlet, it needs more energy to overcome that.

Something you have not thought to mention, is that the air being compressed raises the intake and cylinder pressure about as much as there is a restriction on the exhaust, therefore, it is kind of close to a zero net sum situation, so it really doesn't take much extra energy to run.

I will say this again.....Pay Attention. The Turbocharger makes the overall engine more efficient. It does not rob power and slow it down, it's benefits far outweigh its gains. If it didn't than nobody would ever put them on an engine.

My only point is, it does take some power from the engine in order to run. It is doing so by requiring more force on the piston during its exhaust stroke than it would require if there were no turbocharger in the line.

You do a thought experiment and tell me what the engine would run like if the compressor side of the turbocharger just dumped the air into free space instead of the intake manifold. The engine would deliver less power than if it were not installed due to the exhaust restriction.

This really is just a nuance I wanted to point out, it is a misconception that turbochargers run for free, as if they don't require energy to operate. They do, you admitted yourself that you need to use "a stream of hot gas generated by burning some sort of fuel" which makes my point exactly, turbochargers need energy to run.

I always wanted to see a turbocompound setup on a car. I know it's impractical because turbine speed and crankshaft speed have very different requirements (not just in magnitude but also in dynamics) but I believe an exhaust turbine produces more shaft horsepower than it takes in restriction. Additional energy can be had from the exhaust stream by enlarging the turbine outlet relative to the inlet, increasing pressure differential across the turbine. That's why a catback is so much more effective on turbocharged cars than on N/A cars. Mechanical constraints make a true turbocompound setup unlikely in a passenger car, but I think it would do good things if rigged to charge an IMA battery.

I don't deal with these things much—if the turbo muffles the exhaust, would it do it with more or less restriction than a passive muffler with equivalent effect? Could you 'tune' the turbo for maximum acoustical results?

There is some truth to the turbine increasing the exhaust pumping pressure but it's not true to say that the turbine wholly presents a restriction that would not otherwise be there.

It depends on the engine load and exhaust valve area but the exhaust gas in the cylinder is still at fairly high pressure relative to that in the exhaust manifold, particularly in the early part of the exhaust stroke, even absent forced induction. That means flow past the exhaust valve will be, at least for part of the exhaust stroke, in choked flow.

When that is the case, the pressure downstream of the exhaust valve can be a lot lower than that which will produce the maximum mass flow rate past the exhaust valve. There is some head room within which the exhaust manifold pressure can be increased and have no effect on the mass flow rate of the exhaust gas, and consequently the pressure in the cylinder, at least for part the exhaust stroke.

There can also be some pressure benefit, as freebeard is alluding to ^, in substituting the sound reduction of the turbo for a muffler i.e. you end up with a similar restriction whether with the turbine or muffler in place.

If you think the exhaust pumping work is substantially contributing to the turbine work, try another thought experiment. Run the engine as an air pump i.e. don't add the fuel or spark with a turbine in the exhaust. How much turbine work will be available then vs what is actually available when it is producing the hot, high pressure exhaust gas?

F1 engines next year are apparently going to use turbo shaft energy to make electricity. In addition to the current KERS (Kinetic Energy Recovery System - AKA hybrid), they are talking about TERS (Thermal Energy Recovery System).

From this article: Honda confirms F1 return in 2015 as McLaren engine supplier - The Globe and Mail
And check out this thread in the F1 technical forum:
http://www.f1technical.net/forum/vie...134193b4bebc3b
An old thread, but still pretty cool stuff.

Very cool thread guys :thumbup:

I run a straight pipe on my turbos.
If you use a Holset, they are very quiet. When I was only running the Holset with the straight pipe it was quieter than when the engine was N/A with factory mufflers and full exhaust.
The Garretts are a little noisy.

From back pressure tests others have done with Holset HE351VE and HX40 turbos with a straight pipe during normal driving the back pressures are about the same as the back pressure I got when I had the factory mufflers on there.