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ram air geekery

No, not in the key of C. An H is likely involved though ...
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Post by mercutio » Tue Jul 23, 2013 9:48 am

that depends on what figures he has started with a ported and polished head will flow more air and therefore the figures will change if he is using cylinder volume as a measure then the figures will be pretty static over all engines @A1ex doesn't show his working out :lol:
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Post by NafemanNathan » Tue Jul 23, 2013 9:59 am

One would assume Alex calculated it using a standard H22a head (non-a7).

But yes, calcs would be nice :)

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Post by Mudgey » Tue Jul 23, 2013 10:22 am

I am sure the calculations were based on the swept volume and assuming a 100% volumetric efficiency.

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Post by A1ex » Tue Jul 23, 2013 12:38 pm

Mudgey wrote:I am sure the calculations were based on the swept volume and assuming a 100% volumetric efficiency.
this :lol:
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Post by A1ex » Tue Jul 23, 2013 12:58 pm

OK, so as stated at the start, I’ve assumed no losses in friction from the piping or from the resistance of the air filter.

I’ve also assumed that it’s a smooth linear flow. I've taken the internal flow characteristics of the head into consideration, think of it more up to the filter / throttle body.

The calculation was pretty basic. I’ve taken the displacement of the H22 as 2157cc’s, so for every 1000rpm the motor gets through 2.157 cubic meters of air.

I’ve then take the speed in each gear per 1000rpm, so in 4th at 5000 rpm with an M2B4 box it’s doing 77.7 mph. I’ve then converted the speed the car is doing into meters per minute and multiplied it by the surface area of the intake pipe based in the internal diameter.

That then gives the volume of air being forced into the air pipe at any given speed, which can then be matched against the engine rpm for the speed giving the flow of air which is being forced into the intake vs the air the engine needs.

So if the value is <100% the engine is sucking air in, if the value is greater than 100% air is being pushed in. The %age value shown is then the volume difference between what is trying to be pushed in and what the engine needs. There should be a way to use this airspeed to calculate its effect on the air pressure and density but I couldn’t be arsed to look it up :lol:
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Post by bb1boy » Tue Jul 23, 2013 3:52 pm

Is there an 'over my head' emoticon?? :?
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Post by mercutio » Tue Jul 23, 2013 4:04 pm

its only over your head if you let it be :lol:
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Post by NafemanNathan » Tue Jul 23, 2013 4:05 pm

bb1boy wrote:Is there an 'over my head' emoticon?? :?
:suicide:

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Post by bb1boy » Tue Jul 23, 2013 4:13 pm

hahaha I didn't say I was suicidal!
...Ok, so after reading it all again, twice, the conclusion I have come to (whether right or wrong) is that everything said so far is speculative mumbo jumbo that would only be true in an ideal world of no friction, no resistance and possibly no gravity, which we don't live in, soooooo (and with absolutely no offence intended @A1ex) is all this actually meaningless??
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Post by mercutio » Tue Jul 23, 2013 4:16 pm

pretty much :lol:
bristol_bb4 wrote:ahhh a 5th gen, i love 5th gens :D :lol:
Dino wrote:I loves the 5th gen really.... just dont quote me on it... ;)
4thgenphil wrote:Mines 4 1/4 unches mate, sorry

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