Dirtybill
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posted September 25, 2003 01:11 AM
A question regarding ram air
I've been hearing a lot talk on another forum that ram air on bikes does practically nothing until you reach some high speed like 120mph.
I think it works at lower speeds too.
Now who's correct?
  
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TurboBlew
Moderator
BUSY DOING THE SCHIAVO
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posted September 25, 2003 02:40 AM
I guess those defending that arguement must own Busas. 
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your car is slow
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Fuck Nitrous...Got Boost?
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posted September 25, 2003 04:59 AM
Im sure it works at all speeds...however probably not noticeable or measureable until higher speeds.
I know when testing with the wideband O2 setup on the bike...the a/f ratio at 150mph on the dyno...and 150mph on the street were easily a full point or more different (street being leaner).
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psycho1122
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posted September 25, 2003 06:10 AM
Read the "Hans Test" Thread............
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psycho1122
Pro
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posted September 25, 2003 06:11 AM
YCIS, Do you run the Hans Snorkel?
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your car is slow
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Fuck Nitrous...Got Boost?
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posted September 25, 2003 09:32 AM
no..stock one.
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dougmeyer
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posted September 25, 2003 09:39 AM
It depends on what you mean by "works". The pressure in the airbox doesn't crossover to positive until somewhere around 140-150 mph. So, if your definition of ram air is "power added" by forced induction, it is true that it doesn't work until you are going faster than most 1/4 mile runs with a stock bike. But, of course there is a progressive reduction of the vacuum in the airbox up to that speed where it goes positive. So, even at the lower speeds there is an effect, just not a boost in power.
Doug
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Dirtybill
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posted September 25, 2003 10:30 AM
Woooooooo...just got thru page 1 of the Hans test thread. I didn't do well in physics!!!
Remember the 86 1000 Ninja? Always wondered if those intake runners did anything for top speed or if it was mostly gearing?
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dougmeyer
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moderated
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posted September 25, 2003 10:54 AM
Neither the 86-87 100 Ninja nor the 88-90 ZX-10 had any ram air components. The "snorkles" were for intake noise reduction.
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frEEk
Administrator
ummm... yeah
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posted September 25, 2003 11:01 AM
doug, if i may pick ur expert brain again, i dont get why u wouldnt see an increase in power till u get to positive pressure. if u have 1 pound negative pressure instead of 2lb (say at 60mph vs 30, totally made up numbers of course), wouldnt that be equivalent to going from 0 to 1lb? i'm sure it woudlnt be an identical increase due to the function dictating power response to pressure increases, but i'd think both would provide a roughly similar power increase. so am i reading ur first post wrong or is there something else at work i dont get (liek a function that doesnt begin to climb until positive pressure has been realized, the reason for which i cannot possibly fathom)?
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Koz
Expert Class
Posts: 304
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posted September 25, 2003 11:16 AM
A few years back Sport Rider did some testing on ram air and, if I remember correctly, only the Kawasaki's actually produced a positive pressure below 100mph. I think the max. pressure was .7 of a pound. Also when the 12 was coming out in 2000, I thought I had seen something written about the ram air producing 12 or 14 HP at 100mph.
Koz
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Dirtybill
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posted September 25, 2003 11:24 AM
Thanks Doug.
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psycho1122
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posted September 26, 2003 05:56 AM
What am I?! Chopped Liver?
If you ram air systems are sealed from all leaks, close to a pound of pressure can be had at speeds above 160 mph!
I recorded getting the airbox close to ambient at speeds of 45 mph.
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Y2KZX12R
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posted September 26, 2003 01:50 PM
Psycho, I also found similar results. Another board member sent me a pair of map/baro sensors and I tested the ram air system at 3 locations 2 were with tubes.
The first location was about 6" into the front opening thru one of the removed screws below the ramair unit. I used a "mushroom" over the end to negate any venturi action by the movement of air past the end of the tube. (Just like using a compressed air blow gun to get a siphon going)
The second tube went into the frame thru the screw hole on the front of the tank cover.
The third location was reading the factory MAP sensor and correcting the voltage. All three sensors had to be corrected vor voltage differences but all three got thier voltages from the same source during testing, thus eliminating varriances in the input voltages to each sensor.
My bike went to barometric pressure in the air box around 55 mph at full throttle in 6th gear. As you droped gears you had to be going faster and faster to see barometric pressure in the airbox.
In 1st gear WOT it wouldnt reach the local barometric pressure at redline. Nor in 2nd.
The pressure at the first two locations was almost the same at all times. Althou the airbox (2nd location) pressure spiked low when forst wacking the throttle.
Picture this, your in 1st gear at 2000 rpms and you wack the throttle.
Initially the pressure spikes low for a brief second. Then the air box stablizes at a negative pressure relative to local barometric presure.
As the rpms climb the airbox pressure drops gradually more and more.
In 2nd gear its the same except that it drops slightly less initially and more slowly as the rpms increase. 3rd gear ditto, but the initial pressure drop is slightly less and the airbox recovers to barometric pressure just before redline. 4th gear the pattern was the same as the first 3 gears but barometric pressure was seen sooner and the airbox went positive before redline.
I didnt do a full 5th gear run or a sixth gear run on that test because it wasnt needed. The numbers in 1st thru 3rd charted in MS Excel and then using a formula for ram recovery I got from a friend to predict 4th gear based on the first 3, showed a predictability that matched what I found in testing in 4th gear.
So Doug is right about the bike not producing positive pressure in the airbox at full throttle untill well over 100 mph.
But it will produce positive pressure at a slower speeds when part throttle in upper gears.
I suppose a 1361cc zx12 or a bike with 1 tooth down in the front would show positive pressure later than a stocker. ???
I offered to test Hans's scoop for him when it first came out but he declined.
I also politely offered to design a new unit (with the assistance of a very qualified friend) that removed most of the design compromises that the factory incorperated for various reasons. He politely declined.
Some folks claimed power improvements on the dyno. This is totally possable and may be due to the less "lumpy bumpy" path for the air to flow. But it in no way can predict the effectiveness of the unit at speed.
Its two different situations.
I have some photos of the rig etc. if anyone would like to see it. I cant post photos anymore because i have no place to post them from.
Infact any pictures i have in other threads will disapear soon because charter dropped earthlink. They may be gone on the 1st. I dunno.
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necro
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posted September 26, 2003 04:40 PM
Search the internet for Bernoulli's Law. The velocity is inversely proportional to pressure (ignoring other variables). That means when the velocity of the air in the air box slows down, the pressure goes up.
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frEEk
Administrator
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posted September 27, 2003 01:18 AM
y2k, u can use blkrnbow's server or imagestation (or others) for ur pics. more info is in the FAQ. very much apretiate hearing actual scientific testing tho. can't argue with that kinda proof! thanks.
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psycho1122
Pro
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posted September 27, 2003 10:30 AM
THX Y2K!!
necro....EXACTLY!
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your car is slow
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Fuck Nitrous...Got Boost?
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posted September 27, 2003 11:15 AM
Wonder what effect on pressure nitrous has on the airbox when spraying.
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