daniel mason
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| posted on 11/5/09 at 09:44 PM |
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ram air induction?
is it possible to get the ram air effect with an airbox ducted from nose cone. have seen a nice one on the bay and was wondering if it would work on
the mnr.his ebay name is qbert_10
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BenB
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| posted on 11/5/09 at 09:46 PM |
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Ram air works well above about 150mph. Unfortunately most sevens reach their terminal velocity well before then!!! LOL...
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daniel mason
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| posted on 11/5/09 at 09:50 PM |
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was meaning more like an extra bit of forced induction from ducted nose cone.
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balidey
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| posted on 11/5/09 at 10:01 PM |
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I read somewhere (can't remember where or when) that an engine can easily 'suck in' more air than you can force in just by driving
into the air. Unless you are going at 'silly' speeds, ie over what the car can drive at. So the ram effect doesn't actually exist in
normal conditions. What you can do though, is channel as much cold air to the inlet as possible, therefore giving the engine the air feed that it can
suck in.
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clairetoo
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| posted on 11/5/09 at 10:15 PM |
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With a good airbox/intake arrangement you will get an improvement - but the most pressure you can get will be between a quarter and a half a PSI .
The biggest gain will be from giving the engine cold , dense air - rather than the loss from feeding it hot or low pressure air .
Its cuz I is blond , innit
Claire xx
Will weld for food......
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daniel mason
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| posted on 11/5/09 at 10:20 PM |
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thanks claire. the one i have seen looks nice and is small and light(c/f) he is also selling some nice carbs which may be an option.
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clairetoo
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| posted on 11/5/09 at 10:34 PM |
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Small isnt allways best - but light is good 
I do a carbon airbox - check this thread
Its cuz I is blond , innit
Claire xx
Will weld for food......
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Mr Whippy
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| posted on 12/5/09 at 07:45 AM |
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Ram air does work quite well, used it on the old cortina. If you use a carb it must have a float chamber that is pressure balanced from the Ventura
and not the external atmosphere, otherwise the petrol will be blown out. Don't underestimate the pressure, hold your hand out the window at
70mph, it’s quite a force, especially at the front of the car
Fame is when your old car is plastered all over the internet
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balidey
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| posted on 12/5/09 at 07:54 AM |
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quote:
Originally posted by Mr Whippy
Don't underestimate the pressure, hold your hand out the window at 70mph, it’s quite a force, especially at the front of the car
But which would you rather do, stick your hand out the window at 70mph, or stick you hand over the inlet of an engine running at 5,000 rpm? 
I think where I read it as being uneffective could have been in one of A G Bell's books, will try and have a look tonight.
And I'm not disputing the fact that there is some additional pressure to be had there, but by adding a 'ram' ducting, you
aren't actually adding the ram effect, you are just removing the convoluted path the engine currently uses to suck air from the engine bay.
Which I agree does make an improvement, but is it actually ram? IMHO, its not, its just helping the engine breath better.
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Breaker
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| posted on 12/5/09 at 08:20 AM |
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quote:
Originally posted by daniel mason
is it possible to get the ram air effect with an airbox ducted from nose cone. have seen a nice one on the bay and was wondering if it would work on
the mnr.his ebay name is qbert_10
I think this is possible if you try to make a F1-like air intake. If you look at the air intake of a F1-car (above the head of the driver) you see
that the opening is quite small. Inside the diameter gradually increases. This makes the air to slow down and by this increasing the air pressure.
This is the reverse effect of the venturi of a carburettor. In the venturi you make the air passage smaller; this increases the air speed but lowers
the air pressure.
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sucksqueezebangblow
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| posted on 12/5/09 at 10:25 AM |
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What about these electric "superchargers" advertised on fleabay and t'interweb. I know they cant actually supercharge but perhaps
they might give a similar effect to ram-air. Anyone tried one?
Tech info link here
[Edited on 12/5/09 by sucksqueezebangblow]
Better to Burnout than to Fade Away JET METAL ~ AndySparrow © 
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sickbag
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| posted on 12/5/09 at 11:12 AM |
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Ram air can work, and does, very effectively on bikes. Might be an idea to search on the systems employed there rather than on cars.
Basically you need a large reservoir (air-box) fed through a narrow tube which is fed from a scoop. The carbs/throttle-bodies, all their breather
pipes, etc need to be contained within the pressurised chamber or they won't work.
The scoop doesn't need to be that big (look at ones on bikes) and neither does the feed pipe.
I believe airbox on the CBR is 18 litres so is quite a lot bigger than the engine capacity (600ml) - but at 9000RPM the engine is trying to consume 45
litres of air per second.
Finally back on the job!
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TimC
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| posted on 12/5/09 at 11:13 AM |
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I spole to Andy Bates abput airboxes yesterday. He said you need at least 8 litres of volume ona BEC.
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Rob Palin
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| posted on 12/5/09 at 12:22 PM |
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The ram effect isn't really worth bothering about unless you're at very high speed for any sustained period.
Intake air temperature is vastly more important though, and some 'ram' intakes may often get most of their apparent benefit not from air
pressure but simply from sourcing 'fresher' air from colder locations.
To compare, the ram effect at 150mph is loosely equivalent to an 8 degree difference in intake air temperature.
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deezee
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| posted on 12/5/09 at 03:25 PM |
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Have a read of the Kawasaki Ram Air box. I've talked about this before on other car forums. Simply channelling air towards your filter, does
not increase air pressure in the manifold.
So summarise the link, they got a 20 millibar (0.28 PSI) increase at 150mph through the ram air box. This 20 millibar increase came out to 4% engine
power increase.
I think 150mph in a kit car is unlikely, and frankly the extra 4% HP isn't going to help much against the enormous drag.
Kawasaki Ram Air trials
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