Volume Of Air Used By 2.0L Engine @ 5,000Rpm

[Bananaman]

Can anybody tell me what volume of air a 2.0L Zetec engine uses @ 5,000RPM..... (per Min)

[stephenh]

Well, for every revolution, of a 4 cylinder engine, 2 cylinders will fire. so the sum is actually quite easy I think. (I may be wrong of course!)

2 litres x 5000/2 = 5000 litres.

This is a simplistic approximation, for 2 reasons; first it ignores the volume of petrol vapour, and secondly it ignores the compressing effect on the gases at tdc of a modern engine. To some extent, those 2 points are self-cancelling.

[ianstewartshouse]

As the engine is a 4 stroke it will fill all cylinders once every 4 strokes so approx 2 litres of air used every 4 strokes ( doesn't take account of vacuum or pressure in inlet system) so if you say 5000 rpm and you want to know roughly how much air is req per min that's 1250 (5000 \ 4) x 2L = 2500L / min

I think but I'm happy to be corrected!!

Ian

[peterg]

Interesting article regarding volumetric efficiency here

http://www.epi-eng.c..._efficiency.htm

based on that a 2litre engine (122cu in) will get through 4983 litres/minute (176 cu ft for the septics) - this assumes 100% volumetric efficiency which won't be right but for airbox calcs etc a good max to aim for

so Stephen's 5000 is about right

[Bananaman]

OK so we can assume that the engine will be using 5000L/min @ 5000rpm.

If i were to fit an air-box with a 140mm dia (70mm rad) opening facing the direction of travel this would have just over (0.07 x 0.07 x 3.142)= 0.0154m2 so assuming we travel at 100mph (160kph) @ 5000rpm that would be(160/60) 2.6kpm or 2600m/min?

So 2600m X 0.0154m2 = 40m3/min or 40,000L/min?

That's one hell of a ram-air effect??

Assuming i have my figures correct?

[AdamR]

Assuming the above maths is correct (which I am sure it is) - yes, I guess you are forcing a lot more air into the system.

BUT (my theory) - if the engine can't use that extra air (which it can't unless you start doing 40k rpm?), then you are just effectively adding a parachute to the car?

[Bananaman]

Assuming the above maths is correct (which I am sure it is) - yes, I guess you are forcing a lot more air into the system.

BUT (my theory) - if the engine can't use that extra air (which it can't unless you start doing 40k rpm?), then you are just adding a parachute to the car?

Kinda my thoughts that Adam + the additional air pressure could/would upset the mapping???

[AdamR]

Phew - I'm not completely bonkers then

[stephenh]

As the engine is a 4 stroke it will fill all cylinders once every 4 strokes so approx 2 litres of air used every 4 strokes ( doesn't take account of vacuum or pressure in inlet system) so if you say 5000 rpm and you want to know roughly how much air is req per min that's 1250 (5000 \ 4) x 2L = 2500L / min

I think but I'm happy to be corrected!!

Ian

Ian, you're right about it being a 4 stroke, but you overlook the fact that for every revolution, each piston goes through 2 strokes, not one. Putting it another way, one stroke = half a revolution!!

(No rude comments please!)

[ianstewartshouse]

Doh, hehe I did say I was happy to be corrected, I was talking about an 8 stroke engine.........

;-)

[stephenh]

Doh, hehe I did say I was happy to be corrected, I was talking about an 8 stroke engine.........

;-)

:laugh: :laugh: :laugh:

[Mat Jackson]

You've made some big assumptions about all the air going into the engine at 100mph, there would be some very significant losses which would see the is drmatically reduce.

What you would need to do is calc the air pressure it creates in the air box, and translate that into the extra airflow into the engine.

Not an expert, but the engineer in me thinks this!!

[Bananaman]

You've made some big assumptions about all the air going into the engine at 100mph, there would be some very significant losses which would see the is drmatically reduce.

What you would need to do is calc the air pressure it creates in the air box, and translate that into the extra airflow into the engine.

Not an expert, but the engineer in me thinks this!!

Mat,

I'm no expert (doh!) but would love to hear more about your theories?

Andy

[Nick Algar - Competition Secretary]

Nana's, when you look at it as you have it seems like a great idea to add ram air to apparently get some turno like boost. Unfortunately and I can;t remember why it doesn;t work like that. From well worn out memory the superbikes are getting about 3% extra at 170mph, which makes it worthwile for them, but at our lower speed's it's pretty insignificant. I think it's actually more important to get cold air in than any ram effect.

Sorry to p*** on your chips, at least it wasn't in the shower :laugh:

[BLiNK Motorsport]

In simple terms:

If your bathroom sink can drain water at 1ltr/min when the plug is out and you can fill it at 5ltrs/min - what happens to the excess water?

That is your answer as to what happens with the excess air from the airbox.