School me on ram air induction?

[Big R]

Let me start out by saying: I have been reading into this a lot lately from various sources online. And I am NOT expecting some kind of neck snapping top end power boost.

So what do the great minds of DTT think? I'll be running a larger-than-stock air box, full or half fairing with appropriate duct work, into mechanical carbs (VM34's to be precise). I know that the float bowl vents need to be tied into the air box to equal out the pressure. But what about the air box drain? I'm curious as how any moisture will escape the box since it would need to be pressurized ..... And what happens if I hook up the crankcase breather vent? Obviously I don't want to pressurize the crank case. Either hook up an inline PCV valve or just drain it onto the ground?

Like I said, not looking for an extra 20 horses or anything like that. Just like the idea of "readily available, cooler air" flowing into the box.

 

[hillsy]

If you look at ram air'd bikes you'll see the openings / ram ports are quite small in comparison to the size of the airbox. The idea is more to assist induction at speed rather than supercharge the engine.

This way they can have the crankcase breathers going into the airbox without issue, although they are usually close to the intakes of the carbs, as opposed to being near the ram openings (so the vaccuum effect is higher).

 

[hillsy]

Also, about the air box drain - most set-ups have a low point in the intake tubes and there is a hole there to drain any intake water. This is before the air filter - after the air filter the unit is sealed.

 

[mydlyfkryzis]

Going Fast? Ram Air, like spoilers, are not really effective at under 80MPH speeds. The ram air on newer bikes is up front, at the fron of the fairing. In addition, fuel injection can accommodate the variance in ram air effect at different speeds. Tuning the carbs for the ram effect may make them less than ideal at slower speeds and vice a versa. In addtion, finding the real high pressure area to get the best effect requires a wind tunnel....Unless you are just adding a cosmetic, looks like ram air effect.

Cool air is good. Directing cool air to the inlets is good, so you are not using the air already heated by the cylinders.

I would think a "cold air inlet" is doable and tunable. The ram air concept, while enticing, is probably not really effective on a smaller bike. Now at 140 MPH, the effect is something else....I don't usually ride that fast since none of my vehicles can even go that fast.

 

[Big R]

Thanks gents. Keep the ideas coming though. They are all appreciated.

Hillsy, I am actually looking at dual intakes as a possibility - but with a hose diameter of 1.75". And I'll keep the rest of your posts in mind as well.

Midlife, I've read a lot about the high speed affect of ram air induction. So I understand what you're saying about it not being 100% effective on a street bike. While I'm never going to reach 140mph either, I would like to at least reap some of the positive gains of a "cold air induction".

 

[teazer]

Even at 140, the effect is fairly small.

 

[ronnie]

Midlife,

I just realized his name was Midlife crisis... I always thought he just pressed a bunch of keys on the keyboard for a random username..

 

[Big R]

Ha! We still love ya Ronnie.

 

[kopcicle]

...but worth it or you wouldn't see it on a factory race bike .

That said just one practical tuning aid to keep things all on the same page . The float bowl vents need to be plumbed to the air box when using any kind of significant ram air . It just makes life easier , trust me .

~teaz , agreed , but since one did it everyone had to . I've seen detectable increases due to cold air intake on several street bikes but little if any attributable to "ram air" . I know , I had a digital manometer plumbed into a zx9 . Pressure increase over ambient was minimal and fluctuated wildly even at steady speed and load so go figure .

~kop

 

[Big R]

Kop, thank you. I sincerely appreciate everybody's input on this.

Same for you Teazer - thanks. Glad to have you guys around.

 

[sprocket2cog]

it can add alot to a bikes top end, i added a ram system made from pool cleaner hose and plastic sauces bottles once on an SRX 250 single and at 100 kph you could let the throttle off a bit and the bike wouldnt slow down, then crack it open again and it would pull out to 180 or so. i regeared the back sprocket as well as making a smaller then stock air box from a old ram air car filter. but that bike was running a twin carb primary and secondary into twin inlet ports, tt 250 motor from memory. have fun at higher speeds it can make for some extra ponies.

 

[lingo]

Would any of these bikes see any noticeable improvement from pulling it's intake charge from a high pressure area of the bike like a cowl induction system on a car? The original idea behind cowl induction hoods was the high pressure area formed at the base of the wind screen and trailing edge of the hood. It would still be a cooler air charge than pulling it off the back side of the head and it may be a little more consistent than the ram air effect.

 

[mydlyfkryzis]

Aerodynamically, the ram air effect is minimal at the speed a small twin can travel. the benefit would mostly be from cool air intake.

Even the Ram Air on the Pontiac Firebird, Camaro, et al, really had a small effect.... It was mostly marketing. #/4 of the cars on the road with a hood scoop don't even have an opening.

Funny thing is, most cars draw cold air from behind the headlight are nowadays. Those Cold Air Intake kits often draw warmer air then the OEM ducting.

There are other issues that cold air intake on a bike can have. The expansion of air through the venturi of the carburetor has a cooling effect. Carburetors can ice up, causing poor performance. Slightly warmer air prevents this....

If Ram Air offered serious performance increases, every hooligan bike would have it. they do have front ducts for cool air, but the ram effect is only helpful well above the ton.

Real Ram air is putting a supercharger or turbocharger on the bike. Then you get PSI instead of inches of water pressure increase.