why Warm intake?

[ConnClark]

Originally Posted by tasdrouille

Do you have anything to back this statement? How much do you think 100 F higher IAT raises the combustion temperature? Were you talking about just the warm up phase?

100 degree higher intake temps will raise combustion temps quite a bit. For the same amount of power out your cylinders have less air and egr to heat. It therefore heats it even more. Your putting the same energy into less mass that has already been heated 100 degrees. You'll probably end up with combustion temps 250 to 350 higher than normal when all is said and done.

[naturalextraction]

I've been studying this issue and other related to fuel and air induction systems, design and efficiencies for three years now. Here is a link to the above related to the production of Nox and other emission gasses very simplified:
Emissions
It is related to the high combustion temperatures of the fuel in the combustion chamber. There is a fine line to gains in efficiency in what is considered an "ultra lean burn spark ignition engine". High output of NOX is the concern all though, CO's COV's and the such are lower. The following is an extensive yet simplified information from Cummins that also talks about Selective Catalytic Reduction systems designed to break down NOX and with Ammonia to produce a water vapor out the exhaust. http://www.cumminsfiltration.com/files/def_training.pdf Google "NOX heat related" or any variation there of as there is lots of info to verify.
We've been able to manipulate a phase change in the fuel through the control of temperatures of fuel and air mixtures along with a configuration of a particular design to optimize performance gains and utilize more of the internal energy of today's available fuels. In general, yes, we have found raising the inlet air temperatures controlled throughout the system will provide a gain in economy, as stated from others above, at lower load demands particularly. This related to your means of warm air delivery particularly. There are problems with how today's vehicles cpu's adjust the fuel delivery in order to compensate for warmer air through the intake. It can also be detrimental to an engine through detonation if the fuel system is not operating correctly to adjust. Especially in naturally aspirated "Carb" engines as you are increasing cylinder combustion temperatures. As cfg83 mentioned, some system operating control designs will work better than others in terms of mileage gains related to warm air intake designation.

[blueflame]

Do timing changes occur too via ecu? I'm not familiar with them.

My naturally aspirated carb Citroen Ax has no ecu or even a temp gauge, and I have had to advance the timing slightly as the vacuum advance is kaput and all the other vacuum units at the wreckers were kaput and my other 2 AX have kaput vacuum advance units too...so rather than replace the Bosch distributor with other brand/type and and .... I live with it and have advanced the ignition timing slightly.

I have a manual air intake flap that is lever operated under the hood. This can have either cool or hot air, or a combination of both - 50/50.

Going up mountains in warm weather I often kill the stereo and listen to the engine for detonation by depressing the throttle quickly thereby increasing load... then listening for any detonation which will occur if I ascend too quickly and/or in too high a gear.

Dropping speed and selecting a lower gear will cease detonation.

Yesterday I traveled with surfboards on the roof and 4 people in my 954cc 45hp Citroen, and after 10 minutes pulled over and went to 100% cold air (was a hot day anyway so not that cold!), as performance was crap and detonation was occuring on the flat at 90km/hr. Detonation then ceased. Returning back home in the evening with the cooler night air I went back to 100% warm air and experienced no detonation even ascending mountains at speed. FE was at least 60mpgUS for this mostly highway journey @ 90-100km/hr.

In my case I have had to determine the amount of WAI my vehicle will tolerate by trial and error, even without a temperature gauge. No music and a feel for engine power output is important during this appraisal time. And calculating in various loading considerations of speed, weight of cargo, outside temperatures and incline. Instrumentation would be handy to say the least, but this way kinda brings you in rhythm with the engine and its 'sweet spot'.

I have found WAI to add around 10% to my FE in the Citroen compared to CAI, during this summer, so I use it as often as I can.

[metalshark]

very interesting bits of information but you are missing the fact that a CAI dosnt mean cold air is lead all the way to the combustion chamber.
most newer vehicles (95 +) come with throttle warming features to it.
if I was thinking full cold air I would run a coolant bypass there.

but the fact is shown in many dyno tests that combustion is most efficient at 60-75 degrees Fahrenheit.

by the way O2 sensors are made to see if the combustion of air/fuel is at peak efficiency, but single band sensors aren't 100% right they only read if its too lean or too rich.

wideband O2 sensors on the other hand read how rich or lean the mixture is and CAI dont make Huge Air improvements compared to a stock intake.
made to improve performance with equivalence to stock intake system.

if the CAI ever did make the huge air density improvements you guys speak of the car would need to be retuned.

BUT

in actuality the WAI does the oposite of what extrems you think a CAI does. WAI limits the amount of air going though the intake system, and in that case is limiting the amount of air in the chamber and in turn the O2 sensors are reading the car is running rich so it turns down the amount of fuel needed, and sacrificing power to make a complete combustion.

what ever els happens with the air after the combustion dosnt matter to me.

now remember Im thinking relative to stock, and efficiency is known for effectiveness in both power and MPG.

so if you think im wrong
I urge you to dyno your car on an inertia dyno.

like i said tho its different to different vehicles

[cfg83]

metalshark -

Originally Posted by metalshark

...
BUT

in actuality the WAI does the oposite of what extrems you think a CAI does. WAI limits the amount of air going though the intake system, and in that case is limiting the amount of air in the chamber and in turn the O2 sensors are reading the car is running rich so it turns down the amount of fuel needed, and sacrificing power to make a complete combustion.

...

Thanks for pointing this out. It was one of the points I had read in other threads. When it works, a WAI is an easy way to "lower" your HP.

Specifically for my S-Series Saturn, I have read the "hottest" my IAT temp can get is about 180 degrees F (as read by the ScanGauge). Over that, and the car will become undrivable.

On the WAI on my car, I usually see a range between 120 and 140 degrees F while driving in my "ideal conditions". When I am stuck in traffic, I can get over 160 degrees F. I should insulate my WAI (it's just a clothes-drier duct) for better performance, but I am happy with the setup as-is for now.

CarloSW2

[blueflame]

Dont forget WAI changes the combustion temperature as well as molecular air mass.

What about timing changes in ecu engines?

To prevent detonation retarding occurs?

This is counterproductive to economy?

[metalshark]

well generally my view of efficiency you will get better MPG and power, but if you are loosing one side of the scale you just tipped it you didn't make it more efficient.

lets remember our car were created and tuned in a controlled, possibly indoor, and air condition environment.

ok comparing timing and compression and temperature.
the engine cant make any big differences when it comes to compression vs timing, but when thermal temp is a lot higher there by reducing the amount of air into the combustion chamber suddenly changing the temp to a temperature that isn't too far from itself wont have a bigger impact possibly retarding the timing or making the gas ignite before required to.

if i go on about the CAI I will go off on a calculating tangent

but here I calculated WAI for you
stock intake is about 2 and a half inches wide
air pressure at 70 degrees 100 ft above see level is 0.0742

stock manifold get to about 500 degrees Fahrenheit but lets say light driving you get to 300 and the intake sucks in at 250 (as the temp cools before it hits the IAT sensor {assumeing the IAT is right})

air pressure at 250 degrees 100 ft above see level is 0.0554
(thats what your 2 and a half inch intake opening is getting)
and since pressure cant change in a low volume vacuum the lower 170 degree temperature drop wont make a difference.
except for sparing electronics a bit longer.

but if it sucked air at 170
air pressure at 170 degrees 100 ft above see level is 0.0624
even if you were at see level it will only be 0.0627

all this is still not calculating the humidity in the air as well as the volume.
but if it was added it would look worse due to the quantity of air molecules being less.


but the car wasn't made to have over 150+ degree temp air in the intake.
Im pretty sure sensors go out at extremely hot temps.
and most IAT sensors weren't made for extremely hot air so they might be getting incorrect readings.
which reminds me of if you put a transistor in the IAT plug it will think the air is cold and you will get better mpg a power until the engine blows.

By the way if you want to put hot air into the intake just take the heat shield off the stock manifold it gets everything toasty in the engine bay for you.

[tasdrouille]

If you increase the IAT, but the EGT does not change, where does the heat go?

[metalshark]

it is almost impossible to fully insulate the engine bay so heat will ussualy escape through plastic, or if you haven't sealed the top of your hood, or if you have an outside air flow (generaly produced by a fan if not moving) . if your Intake manifold or engine is aluminum, aluminum is also know for heat dispersal.

[cfg83]

metalshark -

Originally Posted by metalshark

...

but the car wasn't made to have over 150+ degree temp air in the intake.
Im pretty sure sensors go out at extremely hot temps.
and most IAT sensors weren't made for extremely hot air so they might be getting incorrect readings.
which reminds me of if you put a transistor in the IAT plug it will think the air is cold and you will get better mpg a power until the engine blows.

By the way if you want to put hot air into the intake just take the heat shield off the stock manifold it gets everything toasty in the engine bay for you.

In my Saturn they use the same brass covered temp sensor for IAT that is used for the CWT coolant sensor, so I am not worried about failure (knock on virtual wood).

No heat shield, huh? Hrmmmmm, een-tay-rest-ink.

CarloSW2