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Old 19th August 2009, 18:27   #1
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Default Debate: WAI and fuel efficiency

I've been searching around for info on CAIs the last few days and came upon the popularity of WAIs on hypermilers. Principle is that the oxygen deficient warm/hot air causes the engine to run lean as well as providing for better atomization of fuel molecules. Pretty much the opposite of CAIs, other than the atomization part.
Result: better fuel efficiency albeit at lower performance.
Performance losses seem to increase at high rpm(red lining would be sore). This is because of higher rpms producing more heat, which heats up the intake air more, causing more lean injection which further heats up the engine, thus forming a vicious circle.
Efficiency increases are notable. Infact on one particular forum they've seen steady gains of almost 15% mpg in freeway runs using DIY piping using heat of the headers.
Since the monsoons aren't gonna leave us for another month maybe i should give it a try - the roads are too full of holes and slippery for any high spirited driving anyway.
What are your views on this ?

P.S: And I'd be happy if any one would like to give me any advice or warnings before i actually get down on the job.

Last edited by di1in : 19th August 2009 at 18:35.
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Old 20th August 2009, 02:28   #2
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IMO, if you want to increase milage at the cost of power, why don't you go in for a good LPG kit?

That way,
1> I'm sure you'll get better economy from it over a WAI.
2> You still have the power of a petrol engine on tap. [if you decide to rip past some punk ]

Though the investment will be much higher for a good LPG kit.

Also running a lean mix means running your engine hotter than usual, which could lead to increased engine wear.

Maybe you could have a solenoid of sorts so you can switch between a CAI & a WAI. This way also you can have a simple way of switching between economy & power [That's iff a WAI actually increases mileage]

Sorry about that...can't help my self sometimes

Last edited by Sprucegoose : 20th August 2009 at 02:29. Reason: correcting a dumb *** mistake
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Old 20th August 2009, 02:36   #3
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Quote:
Originally Posted by Sprucegoose View Post
IMO, if you want to increase milage at the cost of power, why don't you go in for a good LPG kit?

That way,
1> I'm sure you'll get better economy from it over a WAI.
2> You still have the power of a petrol engine on tap. [if you decide to rip past some punk ]

Though the investment will be much higher for a good LPG kit.

Also running a lean mix means running your engine hotter than usual, which could lead to increased engine wear.

Maybe you could have a solenoid of sorts so you can switch between a CAI & a WAI. This way also you can have a simple way of switching between economy & power [That's iff a WAI actually increases mileage]

Sorry about that...can't help my self sometimes
OR you could invest in a standalone ECU and map it for mileage and then drive it with a light foot. Either way your warranty is void but as well take the vfm option.

Though EGR is already doing what WAI does. as Mcstumpy1885 says

Last edited by binz : 20th August 2009 at 02:47.
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Old 20th August 2009, 02:38   #4
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WAI for people who drive in extremely cold weather ie sub zero temps.
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Old 20th August 2009, 02:46   #5
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Isn't EGR already doing this in most cars? Running them leaner than their non-EGR predecessors?
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Old 20th August 2009, 10:38   #6
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Hi di1in, pre-BS-II cars, like my 2000 Alto have a coolant circuit in the throttle body, i.e. coolant is used to heat the throttle body. This helps with atomization of fuel I guess, from BS-II onwards this heating of the throttle body was removed in the Alto. Check if your car already has a heated throttle body - I've measured mine at 70 degrees C on hot days !

Also, air entering the engine spends very little time in the intake runner & the manifold, so I'm not sure if you'll be able to heat it up much - can I ask what kind of intake air temperature increase you're shooting for ?

P.S. - You could also look at fooling around with your IAT sensor & make it "see" higher temperatures (this sensor is relatively expensive - ~1.8K for my car)...

Last edited by im_srini : 20th August 2009 at 10:39.
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Old 20th August 2009, 10:56   #7
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You are doing all this, for what? About 2 kmpl max? 15% of 45mpg translates to 1.8kmpl from 12kmpl. Running your engine very lean is dangerous, and why do you want to make your engine hotter anyways? A well taken-care-of car will serve you longer.

Last edited by pranavt : 20th August 2009 at 10:58.
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Old 20th August 2009, 14:30   #8
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As long as you dont rip the car, it should be ok.

Moreover, the engine wont be running a lean mixture, when the sensors detect a lack of oxygen in the air, the ECU will automatically reduce fuel supply to maintain ideal AFR.

The only issue could be with temp. If you notice any increase in engine temp, avoid using it.

Shan2nu
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Old 20th August 2009, 14:51   #9
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Quote:
Originally Posted by binz View Post
OR you could invest in a standalone ECU and map it for mileage and then drive it with a light foot.
Quote:
Originally Posted by Sprucegoose View Post
IMO, if you want to increase milage at the cost of power, why don't you go in for a good LPG kit?
Both those options are expensive. Changing the piping to take in hot air is easier and way cheaper.
Thanks for the input though.
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Old 20th August 2009, 15:06   #10
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Quote:
Originally Posted by im_srini View Post
Also, air entering the engine spends very little time in the intake runner & the manifold, so I'm not sure if you'll be able to heat it up much - can I ask what kind of intake air temperature increase you're shooting for ?
The guys who've already done it have vouched for the header heating up the air. The intake is set between the headers and the motor beneath the shield - the have major heating power. They've recorded temp increase at around 30 K. Infact it's because of this that we have a CAI in the first place.

Quote:
Originally Posted by pranavt View Post
You are doing all this, for what? About 2 kmpl max? 15% of 45mpg translates to 1.8kmpl from 12kmpl. Running your engine very lean is dangerous, and why do you want to make your engine hotter anyways? A well taken-care-of car will serve you longer.
2kpl increase for a couple hundred rupees worth of piping is pretty good by my calculations. An increase from 10 to 12 kpl would save you 2 liters every 100kms. That's pretty nice isn't it ? And the lean drive doesn't last long - the ecu would set things right soon. (Thanks for reminding me shan2nu)

Last edited by di1in : 20th August 2009 at 15:09.
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Old 20th August 2009, 16:42   #11
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Quote:
Originally Posted by Shan2nu View Post
As long as you dont rip the car, it should be ok.

Moreover, the engine wont be running a lean mixture, when the sensors detect a lack of oxygen in the air, the ECU will automatically reduce fuel supply to maintain ideal AFR.

The only issue could be with temp. If you notice any increase in engine temp, avoid using it.

Shan2nu
Shan2nu I have a doubt. Since the ECU controls fuel injection rates depending on the amount of o2 in the air what happens when we ride a CAI equipped vehicle in monsoon situations where there is high humidity and a lot of water spray at the wheel arches wherein the CAI intake is placed?

Also Wouldn't the filter get soggy, or if it manages to pass through the filter then wouldn't it have an adverse effect on the motor and sensor?

Thanks in advance!
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Old 20th August 2009, 20:03   #12
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Quote:
Originally Posted by di1in View Post
Shan2nu I have a doubt. Since the ECU controls fuel injection rates depending on the amount of o2 in the air what happens when we ride a CAI equipped vehicle in monsoon situations where there is high humidity and a lot of water spray at the wheel arches wherein the CAI intake is placed?

Also Wouldn't the filter get soggy, or if it manages to pass through the filter then wouldn't it have an adverse effect on the motor and sensor?

Thanks in advance!
The ECU controls the fuel injection based on the amount of AIR entering the cylinders. Generally, the only sensor at the intake is the MAP sensor which reports the negative pressure (in case of naturally aspirated engines) at the intake manifold. If water enters the cylinders, you are looking at big problems and an expensive overhaul.
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