TRNorBRN6001
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posted March 10, 2006 01:08 PM
Ram Air Affect
Ram Air Affect, Topic for them crazy Data Loggers.
Just curious if you have noticed a significant differance in A/F ratio at speeds
around 200mph. Has anyone Dynoed there bikes and had a good A/F then
ran it up to 200mph and had the Ram Air lean there bike out significantly. I would
think .75 - 1.5 psi of ram air at that speed would be reasonable estimate for a ZX-12,
but would like to here a little on this topic as I am a novice.
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zx23rr
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posted March 10, 2006 02:00 PM
back in the zx-11 world of carbs, the ramair on the c model would restrict the air flow and cause a rich condition on the dyno compared to going 180+. A/F would be 12.7-13.2 while under way, and full rich on the dyno.
For the 12, I would think the computer sensors would compensate as again I saw the same kind of conditions as the 11. My airboxes were/are both sealed tighter than a drum.
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TRNorBRN6001
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posted March 10, 2006 04:01 PM
Yeah that ZX-11 did breath through a straw, but it was much better than than
the original old crew of midm to late 80's and some early 90's heavy hitters.
I remember reading a few articles on ram air, but not anything of late. I think the
last one I have seen was on an old ZX-9.
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jimzx9r
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posted March 10, 2006 04:14 PM
The ram air effect is not that great as to screw up the A/F at 200mph, unless your A/F and tune are really, really aggressive to begin with...and on the edge of being lean. Honestly, I don't believe the benefit is from "ramming air" but from scooping cold outside air, as opposed to hot air around the engine.
I read an article recently about truth in ram air...it stated that ram air was just a myth and the product of clever marketing...and insignificant under some ridiculously high mph that couldn't even be achieved by todays cars or motorcycles. The "ramming effect" wasn't even possible, it was all scientific and backed up by studies and engineers. I'll have to see if I can find it and post it.
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claude
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posted March 10, 2006 05:17 PM
Here are a few readings:
http://sportrider.com/tech/146_9508_ram/
http://sportrider.com/tech/146_9910_ram/
http://sportrider.com/tech/146_9912_ram/
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12r1
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posted March 10, 2006 05:30 PM
jim, I'd like to see those also...
jeff
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jimzx9r
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posted March 10, 2006 06:01 PM
 Edited By: jimzx9r on 10 Mar 2006 18:08
Found parts of it...but it's not really worth anything until I can find the real article with all the citations and qualifications of the guy that wrote it.
"Marketers just can't resist it. Ram air! The words themselves summon up images of rushing wild beasts, or of secret military aircraft operating on futuristic principles.
Unfortunately, on most performance cars, ram-air is as functional as tail fins were on cars of the '60s.
What is it? Ram air just means using a forward-facing air intake to gain some extra intake pressure. We have all, as children, felt the pressure of moving air on our hands when we held them out the window of the family car. When moving air is brought smoothly to rest, the energy of its motion is converted into pressure. Motorcycles went through a "ram-air" period in the early 1990s, during which street bikes were equipped with the forward-facing "rocket-launcher" engine air intakes seen on many road-racing machines.
While it's appealing to imagine the forward velocity of a car being converted into free supercharge, the actual air pressure gain is extremely small at normal speeds. For example, at 150 mph, the pressure gain when air is efficiently brought to rest is 2.75 percent. Because this is a dynamic effect, it is proportional to the square of the air velocity. At a more realizable automobile speed of 75 mph, the effect (again with 100 percent efficient conversion of velocity into pressure) will be only one-quarter as great that is, just under seven-tenths of one percent.
In fact, velocity energy is not converted into pressure at 100 percent efficiency. A figure of 75 percent efficiency is usual, which reduces our notional ram-air gain at 75 mph to one-half of one percent.
Therefore, at normal speeds, ram air is a myth. However, something much more interesting lies behind it, ignored by the advertiser's busy pen. That something is airbox resonance.
In order to implement ram air, the carburetors or throttle-bodies of our engine must seal to an airbox whose volume is large enough that the intake cycle of one cylinder cannot pull its internal pressure down significantly. Box volume is typically 10-20 times the engine's displacement. Then the forward-facing air intake is connected to the box. When this assembly is tested on the dyno even without an external fan to simulate the high-speed rush of air past the intake it is discovered that the engine's torque curve is greatly altered, with new peaks and hollows.
Why? The answer is airbox resonance. If you hold the mouth of an empty bottle near your open mouth as you loudly hum scales, you find that at certain "hum frequencies" the bottle reinforces your humming, which becomes louder. What is happening is that the springy compressibility of the air in the bottle is bouncing the slug of air in the bottle's neck back and forth at a particular frequency higher if the bottle is small, lower if it is larger. Your humming is driving a rapid plus-and-minus variation of the air pressure inside the bottle.
The same thing happens inside a resonant airbox. The volume of air in the box is the "spring" in this kind of oscillator. The mass of air in the box's intake pipe is what oscillates. The "humming" that drives the oscillation is the rapid succession of suction pulses at the carb or throttle-body intakes. If the volume of the airbox and the dimensions of the intake pipe(s) are correctly chosen, the airbox can be made to resonate very strongly, in step with the engine's suction pulses. The result, when this is done correctly, is that the engine takes air from the box only during the high-pressure part of its cycle, while the box refills from atmosphere through its intake between engine suction pulses. This produces a useful gain in torque.
Using this idea, motorcycle engines have been able to realize torque increases, in particular speed ranges, of 10-15 percent. In race engines, it is usual to tune the airbox to resonate at peak-power rpm to increase top speed. For production engines, it is often more useful to tune the box resonance to fill in what would otherwise be a flat-spot in the torque curve, resulting in smoother power and improved acceleration.
Early resonant airbox systems used long intake pipes that terminated in forward-facing intakes. More recent designs do not connect the ram-air pipe to the box at all, but terminate it near the airbox entry. The actual entry pipe is a short piece of tubing with bellmouths on both ends. This is done because (a) the potential gain from actual ram air is too small to worry about, and (b) it's easier to tune the airbox with a short tube.
Where vehicle speeds are very high, gains from ram air are significant. This was discovered by Rolls-Royce in the late 1920s as the company developed its R Schneider Trophy air racing engine. At speeds above 300 mph, it was noticed that the R's fuel mixture leaned out enough to cause backfiring. When the mixture was corrected for ram-air pressure gain, the engineers realized they had a "free" source of power. At 350 mph the gain from ram air is almost 15 percent. Similar mixture correction is necessary when ram air is used on drag-race and Bonneville cars and bikes.
Intuition suggests that a forward-facing intake made in the form of a funnel, large end foremost, should somehow multiply the pressure of the air, resulting in a much larger pressure gain at the small end. Sadly, intuition is wrong. In order to convert velocity energy into pressure, the air has to be slowed down, and this requires a duct that widens rather than narrows. Next time you fly on a commercial airliner, note that its engine intakes widen as the airflow approaches the compressor face. Such widening passages are called diffusers, and they are universally used in the conversion of velocity into pressure.
Language often plays tricks on us especially when language is used by product advertisers. "Ram air" sounds much more appealing than "resonant airbox." Nevertheless, it is airbox resonance that actually generates a significant power gain.
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Cliffnotes:
-Ram Air a myth? = NO
-Does it work on a road car = NO
-At 150mph there is next to no gain.
-Significant gains aren't seen until 300mph+
-The air box is the key, not the ducting.
-When buying a CAI/induction kit look for the one that uses air box resonance
Additional Reading
Intake temperature is a whole different ball game.
The simple rule is:
'Cool for power (maximum charge density), hot for economy (minimum charge density to reduce losses due to throttling).'
Although in many cars the under bonnent temperatures are no where near as bad as many people beleive. This refers to a 5.3 liter Jguar XJS V12. So a big engine in a small engine bay.
The under-bonnet air temperature at idle can easily get up around 70 C but the faster the car goes the lower the air temperature falls - simply because the radiator is passing its heat to a much larger quantity of air per second - so at 80 mph. the engine is breathing air at around 45 C. That's still a bit higher than the ideal but not nearly so bad as many people think. Obviously the standard arrangement helps to maximise economy in moderate speed urban cruise without compromising top end power too much.
In setups that duct cool air from outside. The power gains from such a system are almost certainly attributed to the filter, and less restritive intake (meaning quite simply a bigger opening), and a form of air box resonance coupled with a 'cool air intake' from outside the engine bay. Sadly even at very high speeds (well over 100mph) I doubt that it has any form of 'Ram Air' effect. If you reconfigured the system to take air from the inside of a wheel arch it would produce the same results as having the intake ducts at the front of the car. The source of the air, not the location of the ducts is the important factor.
Remember the only way to get a greater volume of air into the engine is to compress it. This is what turbo and superchargers do. An air intake scoop either on the front of a car or on the bonnet will not compress the air at any speed most people are likely to travel at.
Taking the airbox resonance theory futher with the intake manifold itself by optimising the length and entry profile into each of the tracts to better exploit induced harmonic resonances in the air as it flows towards the cylinder. Any tube containing air can be made to resonate at certain critical frequencies in the manner of an organ pipe. Such is the case with the inlet tracts of an engine and if the natural resonance frequencies can be matched to the engine speed then a mild supercharging effect can be induced. Get it wrong and the reverse will apply, resulting in a loss of performance."
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entropy
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posted March 11, 2006 03:21 AM
Edited By: entropy on 11 Mar 2006 03:41
almost like those guys a hundred years ago who proved a bumblebee was aerodynamically incapable of flight...
some empirical results from a 1427 ZX12 running 1/4mi at sealevel (Houston):
cliffs notes
Yes, the airbox resonance is critical:
Example: taking off the rubber connectors between the airbox and the RAM air intake dropped my hp by 5-8 hp on the dyno. Bottom line; DON'T FUK WITH THE BASIC AIRBOX / INTAKE CONFIGURATION.
yes, RAM air system adds pressure to the motor at 150 mph:
I log manifold air pressure and last night (and every time at the track), the MAP gains about .8"Hg at 150mph compared with 30-60MPH.
This may not sound significant, but its equivalent to going to the track when a shitty lo pressure air weather system is present vs a nice hi pressure day, e.g. 29.95 vs good air 30.7+"Hg
High barometric pressure adds about 5% hp, my guess is that RAM air adds about the same.
significant??
Yes, RAM air adds hp, about 5% = 10 hp at 150MPH; 10 hp means 2.5MPH in 1/4 mi.
adding 2.5MPH via RAM air is a whole lot easier than staying on Atkins for 6 mo and losing 30#
no, the RAM air effect doesn't lean out the mixture
the MAP sensor gives intake pressure and the ECU compares intake pressure with ambient (sensor is in the tail) and the ECU adjusts A/F accordingly. My A/F logged 12.7 - 12.9 at lo MPH and the same at 150MPH.
My question (and psycho's) is NOT whether RAM air makes hp (it does), we wanna definitively know whether the Hans RAM air intake makes more/less/same than OEM. That's a test I will do soon 
(psycho has done this test, but i'm from Arkansas  , show me )
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Y2KZX12R
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posted March 12, 2006 04:32 AM
Edited By: Y2KZX12R on 12 Mar 2006 05:04
Sport rider mag. did a pressure test in 99 before the 12r came out. The pressures generated by varrious bikes varried as did when they started to generate pressure.
This sheet will give you a summary from the data they collected.
Notice that the busa doesnt make any ram pressure untill after 140mph. And it can only generate 14mb max.
The countershaft HP of a factory stock as delivered zx12r (according to the service manual) is 178 hp. So thats 12.10 hp per psi of atmosphere. So if you add 14.7psi (one additional atmosphere with a turbo) to a zx12r it would make about 356 hp. Or if you added 1 psi with ramair it would be about 12.1 hp. Thats very close to what the silver book claims the ramair system adds to the 2000 zx12r. So i'd guess that the ramair system on the 12r generates slightly less than 1 psi or about 65mb of pressure at top speed.
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Y2KZX12R
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posted March 12, 2006 05:03 AM
Notice the r6 ramair system. Its excelent. The engine just runs out of hp to push the bike faster. But if that bike kept accelerating it would keep making more pressure. It only needs 140 mph to generate 15mb of pressure, the lowest speed for any bike to make 15mb.
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psycho1122
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posted March 12, 2006 07:22 AM
Y2K: The R6 has significantly smaller displacement (along with an efficient ram air assist), thus having smaller intake pulses drawing from the airbox. Less Vaccume for the system to overcome.
entropy: One of the interesting things I noticed in my testing was how soon the 12's (00') Ram Air system allowed the airbox to recover from a "Vaccume Environment" at W.O.T.
I saw voltage readings on my road tests that revealed achieving AMBIENT by 40 m.p.h.!! AT W.O.T.! When you compare this to a STATIC reading from a Dyno environment, you are already gaining almost .5 lb over Static (Vaccume). From 40 m.p.h. to well over speeds of 180 mph in my tests, my 12 (with a well sealed airbox and snorkels) gained an additional .4 lbs. Now that's worth something!
TRNorBRN6001: Find the "Hans Test / Doesn't Work" Thread. It's long and you have to sort through the B.S. However, it is enlightening and informative!
P.S. entropy: I am still looking forward to your findings! Update the thread mentioned above when you finsh.THANKS!
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supra5677
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posted March 12, 2006 07:35 PM
To Y2K on part 1 or 2 of the same article sportrider was projecting 44mb of pressure way over 27....
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supra5677
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posted March 12, 2006 07:39 PM
Confirmed I just checked it.. Part 1 of Sportrider Magazines Ram Air Whats it worth.. They projected 44mb or more at 180mph.. Iv'e been trying to tell the board this but no one paid any attention to it..The liquid bubbled over at only 30mb at 150 mph...check the article
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trnorbrn6001
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posted March 12, 2006 09:16 PM
Entropy if you are planning on testing the different ram air systems (Hans vs. Stock) at the Texas Mile I am game to help ya out. I am willing to turn a couple wrenches. 200+mph
should give nice results for the snorkel test and real world ram air psi at that speed. Even though that Giant Monster of a motor likes to gulp them PSI's down faster through them oversized TB's and wicked cams.
I do also here that the ZX-12 air box is not very tight and does have leaks as the turbo guys tend to have to do a bit of weld up on the frame to seal things up.
As far as the Busa is conserned the air system is not sealed and a bit of engine and radiator heat tends to get driven in. They do however sell seals to close off the area between the airbox and fame where the ducts come in.
Some may feel like 2-5% is not a lot of gain, but when we spend $1200+ on an aftermarket exhaust to pick up 10%, that small percentage realy starts to look nice to me.
I will have to search for the original hans snorkel vs. stock, should be interesting at the least.
I still have a hard time understanding that preasure would not be greater from a large funnel through a straw size hole compared to just going through a straw. As was stated above, but I tend to be slightly mentally challenged.
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psycho1122
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posted March 13, 2006 06:47 AM
trnorbrn6001: You have to grab the incomming air and "Slow It Down" to get the Pressure to rise. The Hans Grabs too much and the air has to speed up to funnel through the same ducks in the airbox.
entropy! Looks as if you are running quite the large "Air Pump" 
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TRNorBRN6001
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posted March 14, 2006 06:35 AM
I would guess it would get slown down in the airbox and then build the pressure there.
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psycho1122
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posted March 14, 2006 06:45 AM
It will slow down in the snorkel tubes. The inlets to the airbox are larger in total area than the intake mouth.
This is also where the Hans is opposite. It has a larger mouth than the airbox inlets.
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