Heat Pump on Exhaust
 

For those of us on the EcoRenovator site, we often see that a heat pump is a very popular mod to a house (it's like the grill block of house modding!). I was wondering if one attempted to use the heat of the exhaust for a heat pump if the heat pump could be used for anything useful. Some ideas:

• Cabin heat; don't know what good this would do, since we use the coolant, but maybe it will save electricity off of the alternator to pump the coolant to the heater core?
• Electricity generation; don't know how it could be done, but maybe the heat could be used to make electricity and then delete the alt.
• A/C; a heat pump is often used to cool a house during the summer. Maybe this could be adapted to eliminate the A/C off of the engine's drive belt.
• Powered by a turbo; a heat pump uses a compressor, which could be powered by a turbo (turbine and compressor) so it doesn't take electricity from the alternator (and power from the engine)

Maybe this is another one of those give power back here, but take power from there and thus it's a net unchange or worse net loss. These are just a few ideas, I haven't completely refined my thoughts, but I'm willing to bet there is a diamond in the rough here.

I had another idea:

What if during warm-up time, the heat pump transfered heat into the engine coolant to help warm up the engine faster? After that period, then it could run other activities like the ones listed above? I think that may actually help efficiency and certainly emissions during the warm-up period.

Thoughts?

The A/C in a car is a heat pump.

The car heater is using otherwise wasted heat so there's nothing to gain by doing it in any other way. You can either pump the coolant through the radiator or through the heater core. It's pretty much the same pump effort required either way.

Exhaust (and coolant) heat might be used to evaporate a low boiling point fluid and useful work extracted from that in a turbine. (Exactly as occurs in a steam turbine, just lower pressure and temperature.) BMW were prototyping that using ethanol as the working fluid a few years ago.

Yes, a gas turbine in the exhaust can be use to extract work. If not connected to an electric generator it can geared to the crankshaft. See turbocompounding.

Exhaust gas from an ICE is at fairly low temperature and pressure so the efficiency is pretty low. That wouldn't matter where the gas is free and otherwise wasted but cost kills it in practice.

In a spark ignited engine, where the gas flow is throttled for much of the engine operating range, there is a lot of variation in gas flow rate so it's not going to be possible to optimise a turbine in terms of efficiency.

Faster warm would be possible with a heat pump but you have to put energy in to get the heat back. Even allowing for the multiplication effect of a heat pump, it's going to cost much more than you can save. Again, engine coolant heat is otherwise wasted anyway.

I know the A/C is a heat pump, but it runs off of the drive belt. I was thinking about having it run off of the exhaust instead. Conversly, it can also provide heat to the cabin, which means you eliminate the A/C and heater core to have just the exhaust heat pump (eliminate 2 items and add 1 item means a net reduction in car systems = less complex and cheaper... hopefully).

If this is the turbine that you're talking about, I've heard of it and it sounds promising, but like you said, with a throttled engine how useful/efficient would it be?

I'm not sure what you mean by this. The energy in would be from the exhaust which would power the heat pump. A turbo would spin a compressor, but instead of compressing air for the engine, it compresses the warm air from the exhaust (post turbo exhaust is still going to be hundreds of degrees, more than enough for cabin heat). Then run it through a heat exchanger (unless you want to breathe super delicious exhaust fumes in your cabin) to heat the cabin and engine (during warm-up). Where else would I need to put energy in? Maybe a small blower to push the air into the cabin at a desired pace (based on user selection).

I think this might be more efficient, because any pumping can be powered by the heat pump/exhaust. Of course, if one had a TIGERS exhaust generator, then one could just make everything electric and be done with it, but this is another option.

Using a turbine in the exhaust to run the A/C (& heater?) compressor directly? That might work, subject to the limitations of the highly variable gas flow on a throttled engine.

The same pump that is required anyway, to circulate coolant through the engine, is used to pump coolant through the heater core. It doesn't cost anything to use that heat other than having to carry around an extra heat exchanger (the heater core).

Yeah, that's it.

What you are describing is a variation on perpetual motion; expand and cool the exhaust gas in a turbine then re-compress it back to the initial state in a compressor.

Heat from the exhaust has been used to heat the cabin (air cooled VW's) via a heat exchanger.

You were discussing using a heat pump to encourage faster engine warm up. A heat pump uses a compressor, condenser and changes of state (condensation and evaporation) in the working fluid to extract low grade heat from an external source.

Driving that compressor takes energy, even if you can get more heat energy out (taken from the surroundings - air usually, or earth for a building) than you put in to drive the compressor.

I guess it's possible to use a turbine in the exhaust to drive the compressor for the heat pump but that'd be a lot of hardware just to save a tiny bit of fuel.

If you wanted to use the energy in the exhaust gas to aid engine warm up, it would be much easier to do it directly with a heat exchanger between exhaust gas and engine coolant.

Even better is to store some of the otherwise wasted energy from the cooling system (as latent heat) and feed that back into the cooling system in a cold start situation, as is done in Prius.

The big problem with using exhaust heat to power anything is not so much in aquiring the heat - it is right there - but shedding it on the other side of whatever device you'd use.
As you cannot power anything with just heat. You need a temperature differential.

Take the simplest form: Electric energy directly from your exhaust. Attach a Seebeck effect element between the exhaust pipe and a big metal plate. That will easily produce several Watt of electricity that you can feed back into the 12V system. Great!

Except that the plate needs to be quite big to shed enough heat to make it work effectively. And you cannot just attach it to the car body; you do not want to heat that up. The exhaust pipe trajectory is not isolated for nothing.
All in all you'd add quite some weight to the car, just to get a few Watts, less than 0.1% of whay you'd use on the highway. ROI? Not in a lifetime.

The same applies for other approaches; the Stirling generators, the steam turbines; they all need cooling, and that's where it stops being practical for cars.

There are stationary applications that produce heat 24/7. Weight is not an issue there. Size is generally not an issue. They work all the time. They could use waste heat for power generation so much better than any car ever could.

But they don't generally. There are exceptions, but they seldom get a follow-up.
There must be a reason for that.
The reason is that even in ideal circumstances the power generated hardly makes up for the initial cost and maintenance, if at all.
If it does not work there, it has no place on a car. Sadly.

There's no free ride on turbo's, the added restriction in the exhaust puts a higher load on the engine, the question is can you extract more energy from it than the amount that is added back by the additional load.

Extracting waste heat is difficult in the sense of getting to a point of usable heat differential, outside of making hot water or heating the cabin which only requires a differential in the order of 50-100°C, to produce mechanical motion you generally require a differential of 300°C +. There have been some attempts to use lower temps with specially designed stirling engines, but they require highly volatile working fluids and are generally operated at a partial vacuum, so not really something an ecomodder is going to do with an old twostroke and some PVC pipe.

As for the heat pump, again it's efficiency is governed by a heat differential, it can effectively move heat from one place to another, but to use it to increase heat potential it's efficiency begins to fall rapidly, it is nothing more than a compressor and is governed by the same laws.

I applaud you for putting ideas out there, but I have yet to see any workable proposal for utilizing waste heat from the ICE.

Turbocompounding is barely worth the cost, complexity, and reduced reliability in an airplane engine that runs 100% power for 5 minutes, then 75% until almost there.

In a road vehicle that sees 100% power for 5 or 10 seconds, then 10% power, it's useless. In a vehicle driven for gas mileage, the average power is even lower, and it's even more useless.

Turbocompounding only works at relatively high power settings.

There's no heat transfer required with the turbine in the ICE exhaust. It's a bottoming process, solely based on the reduction in pressure across the turbine. The work out through the turbine shaft is equal to the loss of internal energy in the gas as its pressure drops. It cools adiabatically (ideally).

An alternative would be to extend the expansion stroke relative to the compression stroke in the engine and extract the energy from the gas in that way, through the crankshaft i.e. use Atkinson or Miller cycles. Same thing done in a different way.

That´s exhaust pressure you´re talking about. I was reffering to the heat part.

Even so, most of the time you do not want exhaust pressure. Performance goes up when exhaust pressure gets down. At WOT there is some residual pressure at the bottom of the power stroke that could be of use, but not at light load.

That´s why (exhaust) turbo´s (compressing intake air) work so well: they do a lot at WOT and nothing much at light load, just what you need.

At light load running the A/C on exhaust pressure means the pressure differential needs to be high enough to spin the turbo as the volume is low. Then it will work against the engine, requiring much more load.
At WOT the pressure differential can be lower, and tapping that would not matter much as there is an overage. Even so, you are not at WOT for nothing; you would not like to do anything that reduces power then.
A turbo that uses a high pressure difference at low speed and can still function efficiently (having relatively low drag) at high speed would be a golden nugget.

Heat pump systems are complex too.

I kinda like VW's approach:
Run coolant through the exhaust manifold to quickly heat up the coolant and get the engine up to temp.


I've never had a car that warms up this quickly.
I'll have to check in winter, but it certainly looks promising !
Coolant is now up to normal temp in about 1 km.
When hypermiling Hägar the diesel, it wouldn't get up to normal temp before hitting the motorway, after 9 km.
Being a CNG engine, the coolant is also used to heat the gas evaporator.

Then again, a CNG evaporator could be the cold side of a heat pump ;)

I actually like the idea of running coolant around the exhaust to heat up the engine. I'll have to look into this, I might try it one day, once all my other plans actually come to fruition. Is there a thermostat so that it doesn't continue to heat the engine after it gets to operating temperature?

You're engine uses the heat of the exhaust to some benefit. That is what I was theoretically trying to do with the heat pump idea, albeit in a different form. I was really hoping to just put a turbo on it and instead of compressing air for combustion, it compressed it for heating & cooling. Some of that is done via the heater core, but certainly not the a/c.

VW does some of what I was thinking, but in a much simpler form. Thanks for the input and yet another idea to add to the list! :thumbup:

gas vapor cycle turbo-generator
 

In Israel,they have used solar ponds to super-heat a low boiling point refrigerant to power a gas turbo-generator to produce electricity.
The exhaust heat might provide for such a process.Coolant too.

Nail on the head.
possible , but No Free Lunch.

A Turbo in the Exhaust creates back pressure which reduces the efficiency of the ICE... normally a Turbo gets some of this back by also compressing the intact air ... but if you only take away then the ICE sees a reduction in efficiency... and that air pressure in the exhaust is also 'thrust' slowing it down also is a net negative.

Of the energy you take away you won't have 100% conversion to something else... be it Heat Pump or Peltier style... always losses... which means you have to take more than you get.

I think the only way for such a exhaust system to be a net benefit ... is if what it is taking is already waste , with virtually no negative impact for taking it.

The coolant to heat up the ICE faster I think would fall into that category.

Just a few other ideas along this line I've run into in the past.
----
Tigers pdf ... use switched on and off ~80% efficient generator from exhaust instead of traditional alternator... gives less parasitic loss than a traditional alternator... but it isn't a net benefit by itself ... it is just less parasitic losses than a traditional alternator.
----
Link ... NREL researched the potential for a Peltier style device to improve net vehicle efficiency ... after the + and - all balance out... they were left with seeing a potential for only ~1.5% increase in net vehicle efficiency with current devices ... and only up to ~2.5% with future devices ( that they hoped would exist soon ) ... given the cost of such a system ... ~1.5% improvement is rather tiny.
-----
Link ... these People built one to test out of off the shelf Peltier modules ... Their Best case was about ~1kw of harvested electricity when the Engine was under about ~225 HP load. ... ie about ~0.6% of the Engine's load ... a lot of money and several additional pounds ... just for 0.6%... if you were able to get the same results ... maybe ~500Watts when the ICE was under a ~112HP load ... or ~225W @ ~56HP Load ... etc.

Running AC off the exhaust is not a good idea, you'd be subject to variable amounts of heat available and variable temperatures, aka your AC isn't really going to work most of the time. Belt driven wastes power by overrunning the compressor but at least the compressor has adequate power all the time and functions.

Exhaust driven turbines I think are a good idea if the idea is to act like a muffler that returns some energy back to the system, but they also don't generate much power and cost too much money for what they accomplish. Better to just save the energy upstream at the engine using Atkinson cycle. At maximum power like F1 most of the time, it's useful because then the turbine produces a significant amount of power and raises the efficiency of the engine appreciably.

I think exhaust heat regeneration devices that actually come on cars in the near future will be Seebeck effect (thermoelectric) devices, once they figure out some efficiency improvements, or similar very high power to weight ratio heat engines that don't rely on a gas turbine. To condense a low boiling point fluid and drive a turbine would require a low temperature condenser which is going to be difficult. If they figure out some nice 800C working temperature thermoelectric devices that are cheap (not even more efficient), you can run 80C engine coolant through the cold side and end up with enough power for the car's basic electrical demands under cruising conditions, with pretty little effort.

Later model Prius also use the exhaust heat directly.

It's not as bad as it's made out to be. If the flow across an exhaust valve is supersonic, the flow is choked. If that is so, there is scope to increase the pressure in the exhaust manifold without having any effect on the mass flow rate across the exhaust valve at all, at least for (the early) part of the exhaust stroke.

That would be OK though if you could store the energy in a cold sink. i.e. run the A/C compressor hard when the exhaust gas is available and use latent heat storage around the evaporator to cover the intermittency.

The latent heat storage may already be used in some cars (BMW again?) with engine stop-start.

The A/C system would have to be larger though, because the peak refrigeration work would be higher.

SuperSonic Air Flow seems like a mighty big IF to me ... especially in the exhaust of ground vehicles.

It always is (supersonic) in the initial part of the exhaust stroke/end of power stroke.

The pressure in the exhaust manifold/runner isn't constant either. It pulses high around the exhaust valve opening event and is lower through the remainder of the exhaust stroke.

Do you have a reference?

Maybe start with this one:

Internal Combustion Engines - Google Books

It's this book, from page 169:

Internal Combustion Engines (Combustion Treatise Series): Constantine Arcoumanis: 9780120597901: Amazon.com: Books

You can search for more. There's no magic in it.

Thinking some more:

Maybe intercooling the compressed air first and then allowing it to expand for the cooling? Might work. This is done in passenger aircraft where there is a convenient source of high pressure air available in the form of bleeding some air from the jet engine compressors.

I think you're exactly describing what I was thinking. The only difference in this system is that the compression of the coolant comes from the turbo, rather than a belt driven compressor. You would still need an intercooler (or condenser) and an evaporator inside the cabin.

(I think I originally described it as compressing the air for cooling, when I should have said the compression of coolant)

Thanks for the reference.

I didn't think there was "Magic".

But ... I am still of two minds about this.

- - - - - -

#1> It does not change the results of my original claim you posted this in line of reasoning in response to.

That increase in pressure you write about is the same back pressure I wrote about ... and on its own ... just taking that away ... still results in a decrease in ICE efficiency.

- - - - -

#2> I think your reference is not actually claiming this ( supersonic flow ) you described , is actually happening in real engines.

I think the passage from your links you are referring to is:

They claim "Sonic" not Supersonic ... they aren't the same thing.

Bold Added

The author claims this is only "likely" to happen ... and even that 'likely' is only in the theoretical case described.

But we know in the real world ... some of the conditions of that theoretical case don't follow.

For example the low pressure at that point is NOT atmospheric pressure ... as he assumed in his theoretical case ... there is back pressure in the exhaust system ... with a lower pressure difference there will be a slower speed... the gasses also have momentum , etc ... the real world is not that theoretical case.

If you only compress air you don't need an evaporator, just an orifice through which the air can expand. That's a bit different to a conventional car (or building) A/C system which uses the change of state in a refrigerant to absorb and reject heat energy, and is a closed system.

A refrigerant based system can produce a cooling work (energy flow) that is a multiple (maybe 3-4x) of the compressor work. The air based system is only at 1:1 (ideally) but would be simpler to implement.

You do need the intercooler to bring the compressed air back to (near) ambient temperature and so to allow cooling below ambient when the air is expanded. If you search for "air standard refrigeration" you should find some more info.

I've mentioned it in another thread but if you've ever watched an F1 qualifying session you will have seen the drivers being cooled in their cars with air ejectors. The compressed air is released through a nozzle in a duct, which both allows the expansion cooling and entrains (extra) ambient air to provide the air flow.

To play around with the idea, a portable tank for holding compressed air is pretty inexpensive, as is a very basic 12V air pump (not wasted if it doesn't work as you can still use it to maintain tire pressures).

It does cover it. There is reference to more equal pressures across the exhaust valve reducing the time spent in, and the effect of, the choked flow on turbine and ICE efficiency.

Where back pressure (or the lack of it) is important is in the part on the exhaust stroke during which choked flow is not occurring.

It is. It is a theoretical discussion that is non-specific because whether or not there is choked flow, and for how much of the engine cycle, depends on the particular engine and on the load it is under i.e. the actual mass flow which is occurring, the gas conditions, and the size of the hole(s) the gas is flowing through.

Yeah, same thing. If you want to be pedantic, sonic is where the flow velocity exactly matches the local speed of sound, supersonic is where the flow velocity exceeds that speed of sound.

Whether it matches or exceeds the speed of sound doesn't alter the mass flow through the valve (at a particular cross sectional area). That is fixed for any given upstream pressure while sonic/supersonic flow is occurring.

I think your making it harder/more complicated than it needs to be.

The Back Pressure caused by a turbine in the exhaust WILL itself reduce the ICE efficiency ... which is the point I made.

The Turbine and back pressure it produces , does not magically come and go from the exhaust millisecond by millisecond ... looking at tiny fractions of a second events during the whole process is not going to change the overall negative effect on ICE efficiency that back pressure causes... the ICE efficiency is still reduced by the inclusion of the Turbine in the Exhaust.

Bold Added.

Thanks for agreeing with the point I made.

Like having a theoretical discussion about FTL or warp drives... or other fictional devices and or situations that are not the real world.

And the reference did not claim supersonic ... so it is not making that claim.

I'm glad you seem to now agree ... that it is NOT supersonic.

Can we also agree that the conditions of that theoretical case of 'sonic' flow are very unlikely to ever actually happen in a real world vehicle ?

Meaning for one , that immediately after the combustion chamber it will NOT be atmospheric pressure ... as the theoretical assumes ... that a real world exhaust system during operation will have pressure in it higher than atmospheric pressure.

And even if some experimental , non-road going , ICE did see this instant drop to atmospheric pressure through the entire exhaust system ... by itself is also still not be enough to = sonic flow.

Supersonic won't happen... no references to-date showing supersonic.

The conditions listed for the theoretical sonic flow ... are conditions that won't happen ... for real world operating vehicle engines... it is only theoretical ... like talking about FTL or warp drive.

Actually if it exceeds it ... ie goes supersonic ... it will GREATLY effect the pressure ... you will have caused a sonic boom ... and a very different kind of non-uniform pressure front ... which will itself effect the mass flow rate ... even if the upstream pressure is the same for a non-supersonic event ... it will not behave the same.

Although this aspect still seems to me to be making it overly complicated than it needs to be ... whatever the mass flow rate ... when you add a turbine to the exhaust it will reduce the efficiency of that ICE ... no mass flow rate changes that.

If it is simpler, with less items to make it work, then I would imagine it *could* be cheaper for the auto companies to use an air-to-air system.

It makes sense to keep the intercooler/radiator as the heat picked up would still need to be released (or radiated) somewhere else, but with less obstacles within the system (e.g. evaporator).

So the big question then is if somebody was to get into otherwise identical cars, save for the a/c system, would they notice a difference? In other words, can an occupant be comfortable in an air-to-air system without noticing any negative effects as compared to a refrigerant system?

Also important is the efficiency of the system. Assuming we use a turbo to compress the air, would it be any more efficient than a standard refrigerant style a/c? That may be a hypothesis that needs to be determined through trial and error experimentation. If it doesn't improve engine efficiency (in any aspect: FE, power, etc.), then what would be the point?

I wonder if there is something other than air that the system could use that would be more efficient/have better cooling capacity. What about CO2? Or to expand (no pun intended) on that thought, what about exhaust gases (CO2, NOx, etc.)? What about pure oxygen?

I have not heard of the F1 style coolers, very interesting concept though. I would imagine it is similar to the compressed air in electronics dust cleaners, except the cold is transmitted out rather than at the nozzle/can itself. The idea does remind me of the water spray bottles with a fan attached that you see at amusement parks. I wonder if the concept can be used effectively in a duct and vent system that a car utilizes?

The experiment concept is pretty interesting and I already have a 12V tire air compressor for another project that didn't pan out, but as you know this experiment is going to go way down on the totem pole! :p

To what degree i.e. does it matter if the loss is small?

The pressure in the manifold does vary throughout the exhaust stroke. Later in that reference is a discussion of how the turbine efficiency varies with the exhaust pressure pulse(s).

"...the exhaust valve flow passage at that instant of low valve lift is very restrictive and it is likely to be choked (sonic flow at the valve throat)."

"Later in the exhaust process the valve area is larger and the pressure ratio is lower, hence flow becomes subsonic..."

That's pretty clear.

As described in that reference, the exhaust manifold pressure will vary throughout the exhaust process. When there is high pressure in the exhaust manifold there is also high pressure within the cylinder. Flow can still be choked with (relatively) high exhaust manifold pressure.

The fundamental principle is that under conditions of compressible flow/sonic (or supersonic) flow the downstream pressure has no affect on the mass flow through an orifice.

That they don't is probably a clue. If it's cheap to play though, why not?

You can size the A/C system how you want. Is there enough average power available from a turbine to make it workable? Possibly. The peak power from a turbine is plenty, maybe 10's of kW even from a 1.5-2.0l engine. A refrigerant based A/C compressor might take 1-2kW to drive it.

Because there are unrecoverable losses across an exhaust valve it would be better to use the Atkinson expansion to extract some of the energy left in the exhaust gas and take the compressor work off the crankshaft, if you can accept the effective loss of engine size (power) or increased weight for a nominally larger engine. Or only implement Atkinson with low power demand.

CO2 is already being used as a low GHG potential replacement for R134a where a price is being placed on GHG's. It was also used as a refrigerant prior to the development of the CFC and HCFC refrigerants.

It isn't perfect because it has a critical temperature of ~31C which means it can be difficult (or impossible) to get it cold enough to condense.

O2 has some safety issues which would preclude it's use. I am pretty sure that it has to be under quite high pressure to condense when around ambient temp. too. N2 is similar.

With a supply of compressed air I can't see any reason why not. I gather there is a bit of an art to designing an air ejector though.

Actually, back in the days of steam trains, air ejectors using steam to provide the entrainment were used to provide air conditioning for the cars.

At it's most basic, maybe some PVC tube, shaped to form a venturi, and a ball valve to control the flow of compressed air into a small diameter tube within it?

If the goal is to have the same or better net efficiency ... then yes ... any loss is still a loss.

If the goal doesn't care about the loss of efficiency ... then no ... it doesn't matter how much of a loss to efficiency the exhaust turbine causes.

If the goal is in the middle between the two ... then it depends ... how much does one care about the amount of loss , you got compared to what you gained for having that loss in efficiency.

I'm not claiming the manifold pressure doesn't vary through the exhaust stroke ... I'm claiming it doesn't matter ... because once you put the exhaust turbine in place ... it is there for all of it ... you don't get to have it there for millisecond 1 and have it not there millisecond 2... it's there for all parts of the exhaust stroke.

I would expect the efficiency of the exhaust turbine itself to vary as the conditions vary ... but a variation in turbine efficiency just means that less % of the loss the turbine creates gets converted into mechanical power ... ie a 10% efficient turbine wastes 90% of the energy it consumes ... a 99% efficient turbine wastes 1% of the energy it consumes... and the turbine will NEVER reach 100% ... it always consumes more energy input than it converts to the output... and none of that changes that the exhaust turbine is still there for the entire net operation... it does not come and go millisecond by millisecond.

Yes it is ... the reference is not claiming supersonic ... that is pretty clear... just as I posted it is not.

Can be choked is a much better claim on its own ... by itself ... if given up the additional claims of sonic and/or supersonic flow rates.

And the point I was making in that comment your responding to ... is that the theoretical case this reference describes requires completely non-realistic conditions ... conditions that will NOT happen in a real world operating engine... the varying manifold pressure in a real operating ICE does not change the gap between the real and this unrealistic theoretical case's base assumptions.

I still stand by my post above you made this response to ... if it actually did go supersonic ... which the reference is not claiming ... it WOULD very much effect the mass flow through the orifice ... due to the non-uniform effects of the created sonic boom... the nonuniform effects of a sonic boom would propagate both upstream and down stream ... just by going supersonic it would get different results than a non-supersonic.

Claiming supersonic would have no affect compared to sonic or subsonic ... is incorrect.

The old turbo's back pressure debate. lol

IMHO I think its a matter of what out ways what and by how much?

In John B. Heywood's book "Internal Combustion Engine Fundamentals"
on page 870.

Heywood's next paragraph describes how air temperature, fuel octane etc. needs to be optimized for a turbocharger engine.

After reading this around eights years ago I decided to do my own test with real data. I took my son's 1992 Honda Civic and put a cheap ebay turbocharger kit on it.
Start:
http://i147.photobucket.com/albums/r...o/DSC01839.jpg
http://i147.photobucket.com/albums/r...o/DSC01840.jpg

After kit:
http://i147.photobucket.com/albums/r...o/DSC01860.jpg
http://i147.photobucket.com/albums/r...o/DSC01846.jpg
After installing the turbocharger kit the Civic had a increase of 10% in fuel mileage running the stock ecu with the stock injectors.
IMO I based this increase off what this forum has come to the conclusion that "Pulse and Glide" helps with FE. The Civic made more torque at lower rpm and increased the mechanical efficiency that out weight the back pressure increase from the turbocharger's turbine.

Now when DI is added to a turbocharge engine you will even see more better results ecoboost etc.
http://i147.photobucket.com/albums/r...stbaseline.jpg
http://i147.photobucket.com/albums/r...oboost1of3.jpg
http://i147.photobucket.com/albums/r...oboost2of3.jpg
http://i147.photobucket.com/albums/r...oboost3of3.jpg

So you put a turbo on the Civic, but didn't downsize the engine and still got ~10% FE improvement? The exerpt mentions a turbo'd smaller engine vs. a stock size engine (i.e. Ford's EcoBoost), I wonder what FE benefit you would have seen if you had swapped a smaller engine in. Of course, maybe with a smaller engine, you would lose the low-end torque of the turbo and FE would have no net change? (Maybe that is why the EcoBoost engines aren't living up to their expections - that and people can't keep their foot out of it. :)) I also wonder what your results might have looked like if you had put a 'good' turbo in. I'll admit I know nothing about turbos, but maybe if you had a less restrictive/better compressing turbo (T3/T4 hybrids seem to be popular) what sort of FE changes you would have seen. Did the octane requirement change after adding in the turbo?

(Can you post the link to those EcoBoost graphs, I'm having a tough time reading them off the pic?)

But I'm not looking to turbo the car in the conventional sense. A turbo (either the turbine or both turbine and compressor, depending on application) would just be a simple, but effective way to apply what I want. For a quick a dirty example, a turbine spins a shaft connected to an alternator, which creates electricity (e.g. TIGERS).

Another option, if one wanted to have a little more fun would be to over-pressurize the charge air and let it power a device (losing some pressure) before it enters the intake at which point it will be at the appropriate pressure for what demand is (maybe with a pressure regulator to ensure the right PSI). That sounds like way more work (and materials) then necessary and a lot of energy changes, meaning higher inefficiencies. It would be interesting though.

Instead, could one extend the shaft of the turbine to accomadate both a compressor and a secondary device (heat pump, alternator, etc.)? This way, you still have the extra power and the back pressure (if more than negligble) is compensated for by having the charged air, while still using some of the exhaust energy for a secondary device. I know this would create a higher back pressure, but I think the charged air can make up for that.

In terms of mass flow rate: choked flow = sonic flow = supersonic flow = compressible flow.

There's never a pressure difference across the exhaust valve of ~1.9:1 or greater?

I encourage you to read up on what choked flow means and why a pressure wave cannot propagate upstream when the flow velocity reaches the speed of sound.

Yes we just added the turbo kit to the all stock engine. The increase comes from a higher amount of torque at lower rpm with less engine pumping losses at light load. I'm sure that if we ran even a smaller engine the FE would have improved even more, but that's just a guess. The turbo that we ran was a ebay T3/T4 57 trim compressor with a .63 A/R hot side.

At freeway speed the FE was the same with the extra back pressure of the turbine not changing the performance. The extra fuel mileage came from accelerating the car. We eventually started running Crome Pro engine software and I kept the fuel and ignition tables stock at that point in testing.

We did start running premium pump fuel after the turbo install.

The Ford Ecoboost question of not meeting up to their standards is a major debate. A lot of it has to do with the nut behind the wheel as you said. Ford has started something though. Seems like all the major car manufacturers are starting to build DI turbo cars with the same thought process.:thumbup:

With what your wanting to do I think it comes down to how much load will be put on the turbine and what amount of back pressure will be produced?
Some back pressure will help with exhaust blow-down especially higher compression engines. How much it can increase the BTE to offset the pumping loss of the exhaust stroke is the key question.

Ecoboost Link:
http://www1.eere.energy.gov/vehicles...ich_2011_o.pdf

NO.

This comment of mine you refer to here ... I was writing about ... an obvious error in your theoretical reference's claims ... It claims Atmospheric pressure ... in a location ... where in the real world it will not have atmospheric pressure during ICE operation.

- - - - - - - - -

Variations in Manifold Pressure ... do not change this assumption error in your theoretical reference.

I don't know how you think this 1.9:1 ratio you now reference ... has anything at all to do with the assumption error of the theoretical case refereed to in this quote of mine you reference here??

I encourage you to drop any references to sonic and supersonic flow rates ... talk about choked flow if you like ... but drop the sonic and supersonic claims ... especially supersonic.

The engine material will resonate the sound wave up stream ... sound waves are not required to stay in the gas itself ... it will propagate upstream ... and events like a sonic boom from supersonic flow , will cause different effects than a subsonic flow without a sonic boom.

I am wondering what comparison could be made of the Civic's part-throttle intake manifold vacuum, before and after installing that eBay turbocharger. A lower intake manifold vacuum, resulting from higher backpressure due to the turbocharger, could also account for the increase in fuel economy.

OK, in terms of mass flow rate, how do they differ?

1.9 (the reciprocal of 0.528, which is low pressure/high) is the ~pressure ratio above which the flow will be choked (it varies with the gas and its temp.).

Choked flow - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/De_Laval_nozzle

You could be right?

We ran the stock ecu, map, and injectors for a couple weeks before we installed Crome. So I didn't have any data logs of running it N/A.

ok ... which means this 1.9:1 ... has absolutely nothing at all to do with the assumption error being pointed out from the quote of mine you referenced when making the post.

#1> Sonic not = Supersonic.

#2> Chocked subsonic is not necessarily = to chocked sonic is not necessarily = to chocked supersonic ... the way you wrote it by just putting an = sign ... assumes all three are = ... that is not necessarily the case... there can be chocked flow in each of the 3 cases ... but that does not mean all three are =... or that they all have the same choked flow.

#3> your own wiki link bellow to choked flow points out a few issues / errors with putting those 4 things = to each other as you did.

And what?
:confused:

I do not follow why you are referencing a nozzle that is not used in the application being discussed ( Automotive Exhaust ) ?
:confused: