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Cold air intake / ram air?

  • Thread starter Thread starter 80GS1000
  • Start date Start date
txironhead said:
Here's a thought: would the increased drag nullify the benefits of the cold air?
Click to expand...

Given that bikes (especially unfaired bikes) are such aerodynamically dirty machines I can't imagine you could even measure an increase in drag. You can easily gain 5% or more in HP just with cooler air. It will have almost no effect on top speed (power required for any speed is proportional to speed cubed, so 5% amounts to almost no change), but you would feel a noticeable difference around town in acceleration. And that's where all the fun is, isn't it?:-D

Mark
 
You know, you'd think that motorcycles would benefit greatly by reversing the head, allowing the carbs access to the cool air from the front of the engine and allowing the exhaust to be closer to it's exit point. However, from what I've learned, it has been attempted many times by different manufacturers and met with dismal failure. The "why" has never been convincingly answered, just that they tried and failed.

I understand that having the carb inlets at the front exposes them to rain and debris, but look at the "ram air" intakes many Harleys and V-Twins are running now, basically just a snorkel facing the front of the bike. They meet with the same problems.
 
I was wondering the same thing about the whole flipping the head thing also but figured if it worked the manufactures would already be doing it. Maybe they don't do it because of turbulence? I know that on high speed cars you can't just have an open scoop because at top end the air is too turbulent and would screw up the whole induction thing. I dunno I'm just thinking outloud. As for the whole ram air thing, it has to work. Kawasaki has it on their bikes and people claim that they can actually feel the ram air effect
 
Ironriot said:
I was wondering the same thing about the whole flipping the head thing also but figured if it worked the manufactures would already be doing it. Maybe they don't do it because of turbulence? I know that on high speed cars you can't just have an open scoop because at top end the air is too turbulent and would screw up the whole induction thing. I dunno I'm just thinking outloud. As for the whole ram air thing, it has to work. Kawasaki has it on their bikes and people claim that they can actually feel the ram air effect
Click to expand...

Don't think that everything is on our bikes because it works better. There is a strong conservative, traditional esthetic involved in a lot of the design elements. The "reversed" head makes a lot of sense on a liquid cooled engine and has been tried a number of times. I think a lot of the failures have nothing to do with the configuration, but with other design/manufacturing/quality issues with those bikes. It certainly seems to make a lot of sense from a packaging standpoint, but none of the big 4 Jap makers have bit on producing a mass market version. Our loss, I think.

No one says that ram air doesn't work (or they shouldn't), just that the effects are very small and you need very high speeds to realize even those small gains. The gains made from a properly tuned airbox system and the cold air intake setup used on current sport bikes are much higher than ram air pressure gains, even at stupid high speeds.

Mark
 
I rememberd I read an article online in the past that tested a few different modern sport bikes and how much Hp was actually attributed to Ram Air. The Busa was one of the bikes...it didnt do the best in the test; however I was surprized how little Hp difference it made...were talking under 5Hp at significant speed. Bike manufatures ads really hype up the ram air thing. Futhermore the stock busa air box sat right on top of the throttle bodies and obvioulsy it would heat up from rising engine heat inside the fairing at legal speeds. So Im thinking that performance gains would be minimal and possibly imagined just like high octane fuel in an 87 octane machine. I will try and find the article to post...Its really interesting.
 
Just another idea...years ago, racers would take a plain piece of aluminum and mount it to the frame right behind the carbs(like on the cross braces in above picture). Idea was that it stopped the air from swirling right behind the carbs and basically create a dead(or calm) air area that the carbs could use. Supposely worked to some degree as the pro-stockers used it before they went to pressurized air boxes. Use some heat barrier of some type between head/block and carbs along with the shield and that should help.
 
IIRC, the Honda racing guys experimented with this idea, before the Kawasaki 'ram-air' trend....some might recall a pic of simple ducts running from the airbox to the front of Freddie Spencer's superbike. I think at high speeds they found it created a very lean condition, and somehow solved it by venting the carbs via tubes to the same intake duct to equalize pressure ....no, dont argue or ask for details....this I recall from an issue of 'Cycle' in my schoolboy days, so may or may not be entirely accurate. ;)

Tony.
 
Tony you are absolutely right, if you manage to get anysort of pressurised feed to the airbox, you will also need to run your bowl vent pipes to the airbox to pressurise the floatbowls or you will run lean.

Dink
 
The air close to a bike is extremely turbulent. In order to get a consistent even cool charge of air one would have to place the intake well away from the bike. The phenomenon of laminar air flow coupled with extremely odd surfaces on the bike makes it tough to get "clean" air close to the bike.
 
Dink said:
Tony you are absolutely right, if you manage to get anysort of pressurised feed to the airbox, you will also need to run your bowl vent pipes to the airbox to pressurise the floatbowls or you will run lean.

Dink
Click to expand...

Thanks for confirming, Dink....it's weird how some info gets retained eh......other times, I can't seem to locate my car, in the Walmart parking lot.:)

Tony.
 
airboxidea.jpg


This is my idea for an airbox. The blue would be the metal. The red would be the airfilters and the green are the carbs. I was thinking of building the two side tubes from pipe about twice the size as the carb openings.

I wanting to build it more for looks then anything. What do you guys think of a setup like this.
 
If it's just a box, would that make for efficient airflow? I'd think it'd be more effective to have like a 1 into 2 tube or pipe for each side, so that the pushed air is going directly to the carbs, instead of into a box and get confused.

I'm also curious about the pod filters. They all have a metal cap on them...wouldn't pointing them into the wind deflect a lot of air as well. If you were to do a set up like this, it would be cool to find some pointed air filters. and if you're making your own setup, you can use what ever size you want.

or do away with the air filters and just make scoops, like mentioned above and figure out some sort of internal filter element.


All just thoughts....good luck with your project.

peace
 
Sacrifice space in the gas tank or enlarge it to have internally sealed snorkels run through and exit out each side of the tank next to the steering stem. Disturbed air would need to dealt with around the headlight fork area, I imagine.

Plumbing out the rear of the tank could maybe achieved from underneath the tank above the rear portion of the carbs intakes.

A guy who raced at Seattle and Portland had a air/oil GSXR 750 where he lopped off the outer 2 cylinders, plated it and had two flexible black shop vac hoses running from the fairing to an airbox. I think a later version of the bike was featured in Sportbike awhile back.

It's entertaining to read all the "gearhead" brainstorms.
 
The "simple":shock: solution is to relocate the ignition coils and run pipes through the "gap" created. Now of cause you are still somewhat space limited, but it would be a cooler air supply at least, add some sort of scoop at the front say under the headlight you may be headed in the right direction. Remeber also that "vacuum cleaner" pipe is corrugated which would upset the airflow by creating a "boundary layer" smooth walls would be what you are looking for, possibly heated and sculted PVC pipe, leading to the stock aircleaner housing.

Dink
 
Dink said:
The "simple":shock: solution is to relocate the ignition coils and run pipes through the "gap" created. Now of cause you are still somewhat space limited, but it would be a cooler air supply at least, add some sort of scoop at the front say under the headlight you may be headed in the right direction. Remeber also that "vacuum cleaner" pipe is corrugated which would upset the airflow by creating a "boundary layer" smooth walls would be what you are looking for, possibly heated and sculted PVC pipe, leading to the stock aircleaner housing.

Dink
Click to expand...

I've already replaced and relocated the coils. So I might be able to do something like that.
 
THIS IS THE INTAKE IM CURRENTLY BUILDING FOR MY 1982 GS1100GL BOBBER
moz-screenshot-2.jpg
INTAKE.jpg
 
The typical ram air set up , ala srad or zx-11 , mainly pressuizes the float bowls. The routing of the vent hoses from the carbs is very important. We have tried to "blow thru" CV carbs with turbos, and have had some luck, but not much. The air correction jet in the inlet horn of the carb must be modified. I would think smooth bore carbs would be the best for the potential mod. My Hayabusa has it and the airbox looks ike something from star wars.
 
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