"Warm Air Intake" Apparently increases fuel efficiency?

[Duk]

http://autospeed.com.au/cms/A_110577/article.html
http://autospeed.com.au/cms/A_110555/article.html
http://autospeed.com.au/cms/A_110581/article.html

the ideal intake temp increases as BMEP decreases.. say from 40C at full load to 100C at low load..

Was thinking about a set up that uses 2 flaps to direct the air into the air filter box. For cruising is could take air from directly behind the radiator and when required, opens the cold air flap and then closes the hot air flap.

[oldcorollas]

sorry, i meant scientific papers

that above correlation was for diesel.. not for spark ignition engines..

[AdrianS]

Was thinking about a set up that uses 2 flaps to direct the air into the air filter box. For cruising is could take air from directly behind the radiator and when required, opens the cold air flap and then closes the hot air flap.

My old '67 corolla had a similar (factory) system, with a flap that let air in from just above the exhaust manifold when cold, and closed it off when the engine warmed up. IIRC, it had a little weight so the warm-air closed at large throttle openings, even when cold.
You should be able to rig a vacuum-operated flap in the inlet, that allows warm air in at high manifold vacuum, with a spring to close the "warm-air inlet" as the manifold vacuum drops.
Dammit, now I have to re-design my planned inlet mods. I think I'll have to try this.

[Billzilla]

*sigh*
I'll post an image of the Adiabatic Engine. Hopefully it'll raise good questions about how all this works.



Not trying for a thread hijack, just for aome good info.

[oldcorollas]

some interesting comments on eng-tips..
as you know, in turbines they heat the air after compression, not before.

[Z2TT]

If EGR is recirculating exhaust gasses into the combustion chamber, how can it increase fuel economy as your just trying to use a gas that is non combustible? Only way I see is that the recirculated gas is being re-used just for environmental purposes, but how is re-introducing a non combustible gas from the exhaust increase fuel efficiency?

Thanks.

[oldcorollas]

EGR is very simple...
an engine works by expansion due to temperature.
with EGR, you have more gas to expand with the heat generated by the combustion process, so you get more power for a given amount of fuel, and thus, increased efficiency... as well as reduced pumping losses.

this is also the theory with "lean burn" cars

If EGR is recirculating exhaust gasses into the combustion chamber, how can it increase fuel economy as your just trying to use a gas that is non combustible? Only way I see is that the recirculated gas is being re-used just for environmental purposes, but how is re-introducing a non combustible gas from the exhaust increase fuel efficiency?

when you burn air with petrol (assuming th epterol is still liquid) you only get about 5% increase in volume at a constant temp.

the heat generated makes a much much larger expansion, but if you haev too much heat, bad things happen.. so you introduce a "non-combatant" gas to absorb some heat and change it into volume.. so you get higher cylinder pressure and a lower cylinder temperature...

simple eh?

[celicapain]

*sigh*
I'll post an image of the Adiabatic Engine. Hopefully it'll raise good questions about how all this works.

Blackmagic? sounds like a mechanical bumblebee!

[RyleyMA61]

Thanks for the input everyone

Woggin what do you mean all the most efficient cars use Warm Air Intake? I see that they all use cold air intake with a scoop going near the front of the bonnet or headlight.

So what i get it is that when the air is warmer, the throttle plate has to be open more to suck a given amount of air in, so this reduces pumping losses because the throttle is less of a restriction to the engines efforts to suck the air in because it is wider open, so the engine can suck that air in easier giving it better fuel economy? Yes.

Then shouldn't all the economy orientated cars be using warm air intake? Like Yaris, Echo, Getz?

And also, have you ever wondered why so many people have said that their fuel efficiency has gone real bad after putting a pod filter on... and people blame that because it's sucking hotter air in from being unshielded, isn't that argument null and void because hotter inlet temp = less throttle lossses = better efficiency. So I don't understand why pod filters decrease fuel economy that many people have reported.

i see where you're coming from mate, thing is people get too hung up on frictional and flow losses in throttles and piping, and when compared to the efficiency of the combustion process, particularly in this instance, is pretty insignificant.

this "warm air" idea is pretty much horseshit, as is most of the crap on that green driving website. fuel economy doesn't equal engine efficiency/combustion efficienct etc

the power the engine makes and uses comes only from the combustion of air and fuel. in order to maximise the combustion efficiency, you want to use as dense air as possible- similar in theory to forced induction. by increasing the combustion efficiency, you maximise the amount of heat energy that can be extracted from the fuel (42Mj/kg or something? I can't remember the units )

Obviously, if you can maximise the amount of work energy extracted per unit of fuel, you will maximise power. the amount of work energy required to accelerate the vehicle mass (no 1 consideration in fuel economy) can be considered constant, and aerodynamic forces are proportional to velocity squared, so aero really only becomes an issue if you drive a brick or at high speeds.

so, with the work required to move the mass constant, and considering the work energy produced by the engine as only variable on air denisty, in order to maximise power at X rpm, Y manifold pressure and Z throttle opening, you want the coldest possible air.

look at FI cars- cold nights, they go like a shower of shit -> better combustion efficiency therefore better power. (remember when you compress a gas it is also heated a shitload- hence FI loving wangers on warmer days)

it's like knobs who claim "more octane = more power, end of story"

more octane means you have more resistance to knock, and therefore run higher cylinder compression, more aggressive ignition timing and leaner mixtures = more efficienct combustion = more power for the same amount of fuel.

i may have let my brain die a bit since finishing my course, so if i make no sense read up on the carnot heat engine cycles, otto cycles, the isontropic and adiabatic processes.(like billzilla said) it's all basic thermodynamics.

kehendo really hit the nail on the head:

to be honest, i think that any gain or loss will be negligible you're better off leaving it the way the manufacturer intended. they spend millions in car design with a team of 20 or so people to design that intake, do you really think you can do better in your own shed armed with information that you got off a forum?

IMHO the best things for fuel economy are good intakes, good exhaust, good fuel and good tune -> all of which work ultimately to combine the efficiency of the combustion process and maximise the amount of work energy extracted by the fuel. (plus tyres, driving style, etc)

if the other engineers out there (billzill, oldrollas) reckon i've ballsed something up sing out. like i said my brain is on holidays

[RyleyMA61]

*sigh*
I'll post an image of the Adiabatic Engine. Hopefully it'll raise good questions about how all this works.



Not trying for a thread hijack, just for aome good info.

now that's a warm air intake interesting reading too!

[oldcorollas]

Ryley, thats all good and well, but....

most driving (in normal countries ) is not done at WOT, and is only done at very small throttle openings, making small amounts of power relative to the maximum the engine can make.
in that case, temperature differentials may actually become important, as do pumping losses (ie, hotter air = more volume for less mass = less pumping losses? nfi )

aero IS important.. for driving at say, 80 or 100km/hr, aero is a big part of fuel consumption.

FI is a whole different kettle of fish, when it comes to talking about efficiency, since you are never on boost when trying to drive efficiently.. so the turbo acts more as an exhaust restriction...

I really cbf doing any thermodynamic assessments of the process atm, suffice to say that any gains from warmer intake air may be incidental, as they affect other processes/losses.. ie right answer for wrong reasons.

i see where you're coming from mate, thing is people get too hung up on frictional and flow losses in throttles and piping, and when compared to the efficiency of the combustion process, particularly in this instance, is pretty insignificant.

ok, i'm gonna take exception to that OEM spend vast amounts of money and time reducing frictional losses in engines.. things like backcut cam lobes on the base circle, moving back to single chain drive for cams, roller finger followers on cams, lower tension piston rings, even titanium intake valves...
small gains everywhere add up.

[RyleyMA61]

Ryley, thats all good and well, but....

most driving (in normal countries ) is not done at WOT, and is only done at very small throttle openings, making small amounts of power relative to the maximum the engine can make.
in that case, temperature differentials may actually become important, as do pumping losses (ie, hotter air = more volume for less mass = less pumping losses? nfi )

aero IS important.. for driving at say, 80 or 100km/hr, aero is a big part of fuel consumption.

FI is a whole different kettle of fish, when it comes to talking about efficiency, since you are never on boost when trying to drive efficiently.. so the turbo acts more as an exhaust restriction...

I really cbf doing any thermodynamic assessments of the process atm, suffice to say that any gains from warmer intake air may be incidental, as they affect other processes/losses.. ie right answer for wrong reasons.

ok, i'm gonna take exception to that OEM spend vast amounts of money and time reducing frictional losses in engines.. things like backcut cam lobes on the base circle, moving back to single chain drive for cams, roller finger followers on cams, lower tension piston rings, even titanium intake valves...
small gains everywhere add up.

ahhhh you're right, i did make the assumption of WOT... and yeah by high speeds i meant 80kmh+ for aero forces. i better get back into my thermo + fluids books

interesting discussion however!

[oldcorollas]

nah, you're input is appreciated
feel like doing a thermodynamic appraisal of the effect of intake temp? ie during compression, pumping losses, temp loss thru cylinder/head etc?

I'm not sure warm air would be that effective for EFI cars, but i think that it can work for spit'n'dribble cars, preventing fuel pooling under the carby and wetting of runners (in my experience)

[Duk]

look at FI cars- cold nights, they go like a shower of shit -> better combustion efficiency therefore better power. (remember when you compress a gas it is also heated a shitload- hence FI loving wangers on warmer days)

Why are people using F1 cars as example of achieving improved fuel ecconomy?

How many times are people cruising down the road at full throttle?

The fact of the matter is that WHEN CRUISING at a legal speed the engine can only injest so much air past the partially open throttle. The driver will only be using enough throttle to maintain their chosen speed.

You can put a positive displacement supercharger before the throttle and the engine will still perform as required depending on the amount of air the throttle body allows into the engine. So any ram air feed that you could achieve at highway speeds is still worth zip when cruising. You may use a smigin less throttle but manifold vacuum would stay the exact same as pre ram air feed.

A high/full throttle acceleration is completely different.

When cruising, there is no chance that you have reached the flow limit of any pre (or post for that matter) TB component in the intake tract.
You can't put a bigger AFM, a bigger/better flowing air filter, or a higher flowing air intake on your car and gain better part throttle fuel ecconomy. The partly open TB is still the worst flowing item in the intake tract.

If your car needs 'x' kilograms of mass air flow per minute to do 100km/hr (obviously changes in wind direction and road incline will affect this) then it doesn't matter how much pressure you put infront of the TB, you will only let in 'x' kilograms of air every minute. If you let in more than you go faster, it's that simple.

[jimmmayyy]

it says FI not F1.