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Search for "aluflex pipe" numbers.
smooth walls are good until a certain point where the laminal flow would fade.
At a certain flow rate, the rough surface is better, like golf dimples and dimple porting.
RB products are fancy plug and play hence they have to scarify on some corners and push their marketing as much as they can.
Some report issues with RB revi over the speed of 200km/h.
Well, that’s pretty interesting. I do wonder what is RX8 intake air speed I’m talking through the filter box/MAF at say 9000 RPM?
Obviously air speed through the ram scoop/hose is going to be pretty close to vehicle speed that at least initially and then it would significantly slow down in the airbox building up pressure?
Well, that’s pretty interesting. I do wonder what is RX8 intake air speed I’m talking through the filter box/MAF at say 9000 RPM?
Obviously air speed through the ram scoop/hose is going to be pretty close to vehicle speed that at least initially and then it would significantly slow down in the airbox building up pressure?
It is more complicated than you think, Mass Air Flow measures in weight(e.g. gram) in time(e.g. second)
Weight of air depends on many things like altitude, ambient temperature, humidity, and so on.
The aforementioned 270g/s could be equal to something around 0.27 liter per second which is well below 1 liter per second.
Last edited by motodenta; 03-04-2021 at 12:43 PM.
Reason: correct my mistake
Well, that’s pretty interesting. I do wonder what is RX8 intake air speed I’m talking through the filter box/MAF at say 9000 RPM?
Obviously air speed through the ram scoop/hose is going to be pretty close to vehicle speed that at least initially and then it would significantly slow down in the airbox building up pressure?
It should actually speed up since your scoop funnels air into a smaller cross-section. How it compresses as a result of its own momentum after that is hard to guess, but the MAF gives you g/sec.
I'd focus on air mass more than air volume, since volume is a function of pressure, temperature, etc. Whatever mass is going through your MAF is the mass going through the rest of the intake, before and after.
If you look at the white rectangular scoop a few posts up, its functionally the bottom part of the Racing Beat intake. The top half is the same shape again but flowing in the other direction.
It is more complicated than you think, Mass Air Flow measures in weight(e.g. gram) in time(e.g. second)
Weight of air depends on many things like altitude, ambient temperature, humidity, and so on.
The aforementioned 270g/s could be equal to something around 0.27 liter per second which is well below 1 liter per second.
1L of air at STP is 1.2grams. So 200g/sec = ~160L/sec
I think you were counting water at 1kg=1L, not air?
1L of air at STP is 1.2grams. So 200g/sec = ~160L/sec
I think you were counting water at 1kg=1L, not air?
na dadash,
I made a mistake.
we have to measure molar volume of the gas, which by Ideal Gas Law is 22.414 L
molar mass of dry air is 28.9647 g/mol
So22.414 L is 28.9647 g
28.9 / 22.4 = 1.2
So, at normal( sea level, regardless of temp... ) one liter of air is equal to 1.2 grams
1l/s = 1.2 g/s
270g/s = 225 l/s
~ 470cfm
270g/s air is a V8 4.5L @ 9000rpm
For water:
"1 Liter per second to grams (water mass) per second = 1,000.00 g/sec" 1 l/s H2O = 10000 g/s
Water has very strange behaviors at different temperatures, which is another story to catch.
It should actually speed up since your scoop funnels air into a smaller cross-section.
How it compresses as a result of its own momentum after that is hard to guess, but the MAF gives you g/sec.
I'd focus on air mass more than air volume, since volume is a function of pressure, temperature, etc. Whatever mass is going through your MAF is the mass going through the rest of the intake, before and after.
If it speeds up it would cause a pressure drop. (Mr.Bernoulli law for horizontal pipe)
Don't want to nick-picking but there are lots of mistakes, air pressure is like a layer on the layer, a wave...
PCM/ECU uses barometric and temperature sensors to correct MAF reading.
What happening in the rest of the intake is the other, others story especially in rotaries.
The only confirmation we can get is via a pressure gauge on the actual car.
If it speeds up it would cause a pressure drop. (Mr.Bernoulli law for horizontal pipe)
Don't want to nick-picking but there are lots of mistakes, air pressure is like a layer on the layer, a wave...
PCM/ECU uses barometric and temperature sensors to correct MAF reading.
What happening in the rest of the intake is the other, others story especially in rotaries.
The only confirmation we can get is via a pressure gauge on the actual car.
It may well cause a pressure drop. Said another way, static pressure at the intake mouth will be higher than through the constriction, which is part of the reason ram air intakes are tricky. Sure, you can ram air at the mouth, but if not done right, you lose all of that benefit by the time you get to the throttle plate. And, high pressure at the mouth also acts on the air before and around the mouth, reduces flow through the mouth and negates the point of putting the mouth in the air stream in the first place.
Mass measurement: sure but there is no new air mass being introduced past the entrance of the scoop (hopefully), so even if the MAF mass measurement is not 100% accurate, its the only stable measurement of intake performance and will show relative improvement between intakes (all else held equal). Looking at flow volume is going to be subject to all kinds of variables that arent helpful in measuring the intake performance.
I point something and apparently, no one noticed.
In order to make a ram air works, we should relocate the barometric air pressure sensor to the entrance of ram air, Or plug a hose from there to the sensor.
Of course, if can observe any pressure increase in the ram air. For this reason, I said it should be measured with -/+ gauge to see how much positive or negative pressure we can observe.
For mass yes hopefully all that comes in goes out If there is no blowby or one rotor failing on compress... all ECU does is half the total mass assuming both rotors are receiving an equal amount of air.
( In some cars the barometric sensor used only on start-up of the car and/or they are backup for guesstimate correction)
Two major issues with ram design are 1-flow separation 2- momentum loss
everything needs to be just the right size not big, not small.
so to get the accurate MAF readings I would need to move barometric pressure sensor in the airbox before filter to account for increased pressure from ram effect?
otherwise ecu will think it is getting less air then what is actually getting into engine, which would lean things out in the open loop operation mode right?
Last edited by Nadrealista; 03-05-2021 at 08:26 AM.
so to get the accurate MAF readings I would need to move barometric pressure sensor in the airbox before filter to account for increased pressure from ram effect?
otherwise ecu will think it is getting less air then what is actually getting into engine, which would lean things out in the open loop operation mode right?
Fuel trims will adapt either way. It will learn to compensate for the few % of difference it makes.
The opposite is also true: if you put the the baro sensor in a high pressure zone, but the intake isn't actually propagating that pressure to the engine, the airflow calculation will still be a little inaccurate, but the car will still compensate.
The baro sensor is there to adapt to weather & altitude changes, not to tune the car.
According to my Ford EEC5 training book, BP is used in the different strategy modules for :
- crank fuel
- desired mass air flow through the idle air by-pass valve
- switching to altitude tables for EGR and spark advance
- torque converter lock-up
- shift chedules
- calculation of theoretical air charge at WOT
- self test
and I believe it also affect electronic throttle body progression.
so to get the accurate MAF readings I would need to move barometric pressure sensor in the airbox before filter to account for increased pressure from ram effect?
otherwise ecu will think it is getting less air then what is actually getting into engine, which would lean things out in the open loop operation mode right?
Well, the thread is about Cold Air Intake suggestions as so your build is CAI.
Do not hope to have a ram air charge effect unless moving the ram in front of the bumper/car.
Any ram in the back of the grill or bumper is CAI. It should stick out!!
Yes/No even if it creates a higher pressure, it would confuse ECU as it sees its MAF deviation aka fault. As rx8 dost does not have an EGT sensor it would solely look to
wideband O2 and check backup it with secondary O2 and.....
It is complicated and just bla bla booo without proper data logging.
Textbook examples of MAF false reading, If we have a sudden increase of air mass somewhere ( presuming ram effect discharge! on high speed) it would be interpreted as a fault because ECU does not see any change in gauge pressure reading the barometric sensor unless it remapped. It is complex as far I can understand.
These graphs are so cheeky!
Firstly, the units are chosen in a way to exaggerate the results, 0.1 m3/sec is equal to 0.0001 cfm ( 0.000057 g/s) which is nothing to cause any gain.
Secondly, the power band must be measured on wheels as the 125kw is 167hp, and based on other dyno graphs by shortening the part intake would cause
a power drop in low rpm, also it is noticeable that there was a huge gain on the top end which cannot be justified by 0,000057 g/s increase.
Lastly, the temperature dropped could happen if they run it with the bonnet open I guess.
1 cfm = 0.00047 m3/s
The first google search result for "m3/s to cfm" is wrong
[edit] looks like its just the label in the graphic, I agree with the rest.
The R/S fully open and R/S Box 1 don't make a lick of sense, those are hot air intakes.
1 cfm = 0.00047 m3/s
The first google search result for "m3/s to cfm" is wrong
[edit] looks like its just the label in the graphic, I agree with the rest.
There’s no way that either of these contraptions are creating pressure in the intake system. The best you can hope for is to offset the restrictions downstream some. Which is going to directly be reflected in the MAF readings. That’s not likely to happen with a long 4” tube snaking around into a 4” x 6” oval opening. So in addition to that, the baro sensor relocation is pointless.
The max MAF values mentioned earlier were only with a custom box/filter/maf tube ported into the oval opening at the front. The class I was competing in doesn’t allow removing the plastic shield on top of the crash bar. So it’s not possible to fit a ram air duct; it didn’t have one. That’s how ridiculous this discussion is.
IMO, RB design is a failure on bends also as it tries to fit OEM factors like openings and...
Metal 90-degree pipes are a failure too in the term of flow and heatsink.
There some good here: Updated Miata air intake design now available | Wrench Game
Many production motorcycles have used ram air systems effectively for over 30 years. Starting with the 1990 Kawasaki ZX-11.
They have had measurable improvements in top speed with these systems.
Money quote: "Just riding from the dyno facility to the strip was illuminating. We'd reckoned on needing 90 mph before boost would register, but at an indicated 70 mph the manometer already showed 8mb of boost.The results were even better than we'd hoped for. At lower speeds (under 120 mph) the gauge was easy to read and the result quite consistent: at 70 mph pressure was 8mb; at 80 mph, 10mb; at 100 mph, 12mb; at 110 mph, 14mb. From this point things really took off. At 120 mph (indicated) the airbox pressure was approximately 19mb, 130 mph about 23mb, at 140 mph, 26mb and at an indicated 150 mph, the gauge was beginning to pump out green liquid as it bubbled over the 30mb limit."
__________________________________________________ __________________________________________________ _____________________
RAM AIR
What's it worth?
Source: Sport Rider, August 1995
Why are Kawasaki's so damn fast? Anyone who's experienced the giggling hard-core buzz of a ZX's awesome acceleration from the pilot's seat comes away shaking his head in disbelief.
Time after time the big K's machines run faster at the strip than rivals which put out notionally identical horsepower. So where do the extra horses come from?
This is an account of the first attempt to scientifically measure the real effect of ram air.
The results may surprise you.
Who has it?
The ZX-11, ZX-9R, later versions of the ZX-6 and ZX-7 and the new ZX-6R Ninja all utilize the ram air system, and now Honda's latest CBR600F3 has followed along the same path - a sure sign that it works.
The difficulty is in measuring the effect, simulating the results of a 150-mph airflow, while the motorcycle is harnessed to a static dyno. But that is exactly what we set out to do with the help of Steve Burns, noted builder of very special turbocharged trick-framed motorcycles, sometime dragracer, endurance-racing-team boss and the owner of a Dynojet Model 100 dyno. As an innocent patient we had one meticulously prepared Kawasaki ZX-9R Ninja.
The theory
In essence, the theory behind forced-induction systems like Kawasaki's is quite simple and not that far removed from turbocharging, just at a less extreme level. A motorcycle traveling at high speed is pushing a slug of pressurized air ahead of it. If the air-inlet is placed in the correct position then air entering the airbox will be greater than atmospheric pressure. The resulting intake charge will be denser and cooler and contain more oxygen and fuel, thus causing a bigger bang and hence -Hallelujah!- more power.
There are limitations. The amount of mixture you can force through a motor is finite. Imagine strapping a ZX-9R on top of a jet aircraft and starting the motor; the plane will rapidly reach a velocity where the motor would be incapable of utilizing the volume of mixture being forced into it.
Next, at very high speeds -over say 150 mph, where theory says that ram air should be working most effectively- the nature of air drag means that large increases in horsepower are needed to produce relatively small increases in speed. Finally, compared to turbocharging systems, the increase in pressure are quite low. How low? Before we began testing, Burns predicted, "I don't think we can get more than one psi in there."
The ZX-9R system
Kawasaki's ZX-9R uses a relatively straightforward system compared to the 1995 Honda CBR600F3. Twin vents mounted beneath the headlight channel air via ducts running over the frame beams and int a sealed airbox. Look closely, and you can see two smaller nozzles behind the grilles which connect to the carburetor float bowls. Their function is to equalize the pressure between float bowls and airbox; without them the higher pressure of the incoming charge would upset the carburetion, potentially blowing fuel out of the bowls and tending to push fuel back down the jets, causing mixture leanness. Kawasaki uses much the same system in all its ram-air machines, though the ZX-7 and earlier ZX-11s have a single inlet only.
Measuring
To reproduce the effects of high-speed running on a static dyno, Burns' intention was to use a fan capable of producing relatively small volumes of air, but at high pressure. The fan was connected via custom-made tubing and coupling to the intake vents of the big Kawasaki. The joint was carefully sealed with high-density foam.
So we could measure the pressure generated in the airbox as we pumped air up the ZX-9R's nostrils, a manometer, or pressure gauge, was plumbed into it. With the manometer we would be able to measure pressure up to 30 millibars above atmospheric pressure. A bar is roughly equivalent to atmosperic pressure; one millibar (mb) is just one thousandth -0.001- of a bar. Not a lot compared to tire pressures, but Steve's experience with varying boost levels on his 250-bhp turbo -which churns out approximately an extra five horsepower for every 70-millibar (one psi) increase in boost ore intake pressure- suggested that if it were possible to create one psi of pressure in the airbox, we could be looking at an increase of 5 to 6 bhp. Note that pressure in the context of this article is pressure above atmospheric pressure.
Testing theory
Burns' first thought was to set the air pressure at a certain level, say 15mb, and then measure the power at a steady throttle at 1000-rpm intervals. This was abandoned when we realized the results would be meaningless using CV carbs, which wouldn't necessarily be at full lift.
The second problem was that as the slides lift and the motor drags in air, the pressure in the box drops off. Observation suggested that if the airbox pressure was set to 10mb at idle, then at the redline, the manometer would show just 4mb. Obviously this bears little realation to real life, as the only way the airbox would be pressurized at idle would be if the bike were freewheeling down the highway.
Most importantly, the level of intake pressure on the road would be realative to the velocity of the motorcycle. If the airbox were pressurized to 20mb at 150 mph, it would be correspondingly less pressurized at 120 mph and still less at 70 mph. We had no way of reporducing this effect on the dyno, but if we could show that an air pressure of, say, 20mb gave a boost of 3 bhp at a certain point in the rev range and could then relate that to real road conditions, we'd have a fair idea of what the actual power output on the road would be.
In the longer term, Burns hopes to be able to use an interface between fan and dyno to take account of increasing air speed and thus simulate the effect of road speed on a static dyno.
First test
The initial step was to run the Kawasaki at atmosperic pressure -no boost- to get a baseline figure. The ZX-9R, like others tested on the same facility, gave 123 bhp at its power peak. The induction fan was then connected, and the bike was run with the intake pressure set to 10mb at idle. The process was then repeated with 20 and 30mb of pressure. In each case the intake pressure fell by approximately 6mb at peak revs when the slides were fully up and the engine was gulping down great gobs of mixture.
The results were gratifyingly clear. At peak power the ZX-9R was producing an extra 2.6 bhp for every extra 10mb of pressure fed into it by the fan. Peak power was up from 123 bhp to 131 bhp, an extra 8 bhp over atmosperic pressure. A secondary bonus was that the bike also hung on to its peak better, which would translate into a more forgiving motor on the road, which would be less sensitive to gearing and thus more likely to be able to take advantage of following winds or favorable gradients to give a higher maximum speed. Because of the testing procedure we'd been forced to use, the graphs also showed similar increase right through the rev range, but this was obviously deceptive. There was no way that the levels of boost measured at low speed on the dyno could be reproduced on the road. At this point we suspected that boost would be insignificant at speeds below 100 mph.
Interim conclusions
So far so good. The first part of the experiment was a success. We'd shown that pressurizing the ZX-9R's airbox definitely produced power increases. We'd established that the system has the potential to work, but what we didn't yet know was how the pressure we'd managed to generate on the dyno -a maximum of 30mb at idle, or 24mb at peak revs- related to real road conditions.
Phase two was to attempt to establish what sort of pressure are actually generated in the Kawasaki's intake system at speed and relate them to the dyno results.
Phase two
Had we been NASA or a top G-team, the next step would have been easy. Strap a datalogger to the bike, rent a private test strip and go play for a couple of days. We weren't, so the manometer was cunningly strapped to the gas tank, green food coloring added to the fluid for added visibility, and a portable datalogger -yours truly- mounted to the bars.
Just riding from the dyno facility to the strip was illuminating. We'd reckoned on needing 90 mph before boost would register, but at an indicated 70 mph the manometer already showed 8mb of boost.
At the strip we were able to give the big Kwakker its head, with one eye on the slowly rising column of green fluid and the other on the rapidly rising speedo. At the end of each run we logged boost pressure agains indicated speed.
The results were even better than we'd hoped for. At lower speeds (under 120 mph) the gauge was easy to read and the result quite consistent: at 70 mph pressure was 8mb; at 80 mph, 10mb; at 100 mph, 12mb; at 110 mph, 14mb. From this point things really took off. At 120 mph (indicated) the airbox pressure was approximately 19mb, 130 mph about 23mb, at 140 mph, 26mb and at an indicated 150 mph, the gauge was beginning to pump out green liquid as it bubbled over the 30mb limit.
At a real speed of 167 mph, past experience shows that the ZX-9R speedo indicates 181 mph; there was obviously even more to come, perhaps as much as 30 mph worth of additional air pressure. Plotting the air pressure figures against speed for a rough representation of the way the air pressure increases suggests that the progression isn't linear.
This is as we'd expeted. Air drag doens't increase at a linear rate but relative to the square of the speed. At above 25 mph, air resistance builds proportion to the square of the air speed over the motorcycle: twice the speed, four times the resistance. The faster the bike goes, the greater should be the increase in pressure and thus intake pressure. When we plotted the rough course of the pressure increase on a graph and continued it upward we came up with a projected 44 mb (or more) of pressure at an indicated 180 mph, when the bike would actually be traveling at its real top speed of 167 mph.
So what does it mean?
The maximum pressure we were able to generate on the dyno was approximately 30mb, which gave a peak of 131 bhp from a ZX-9R as compared to the 123 bhp measured at rest. In other words, each 10mb increase in inlet pressure is worth approximately 2.6 bhp at peak on a derestricted 9R.
At an indicated 150 mph on the road, the inlet pressure had already neared the 30mb figure. We can therefor say with confidence that the ZX-9R is producing at least 131 bhp at the rear wheel in real world conditions - 8 bhp more than at rest on the dyno.
Flat out, however, the Ninja indicates another 30 mph on the speedo. If boost at this speed was, as seems likely, 40mb, then the gain over atmospheric pressure would be approximately 11.5 bhp, giving a peak figure of 134.5 bhp. If inlet pressure reached 45mb, which it might well do, then the increase would be as much as 12 bhp, of a peak of 135 bhp.
In other words, 123 bhp measured normally on a static Dynojet rolling road dynamometer could translate to as much as 135 bhp or more on the street. Ram air works.
Implications
An extra 12 bhp sounds like an extraordinary power gain for nothing except a bit of wind, but it's important to remember that at lower speeds the increases won't be as significant. Up to 120 mph when the boost hits 20mb, we're only talking about the odd bhp. From then on it gets progressively stronger. As the effect is speed relative, it's most pronounced at very high velocities; the faster you go, the stronger the boost. But, hey, how many of you ride at 150 mph on the street? Never mind, don't answer that.
Having said that, the effects of even small amounts of boost on throttle response haven't really been investigated and may help to explain some of the surging acceleration typical of big Kawasakis.(JDR: see my dynojet page)
It does, however, clarify the impressive figures that Kawasakis deliver at the strip and explain why a ZX-7 putting out the same power as a GSX-R on a static dyno will romp away under speed testing. It also begs the question of when someone is going to bring out a fully functional aftermarket pressurized-intake system.
Finally, it explains why Honda's jewellike CBR600 has finally gone the ram-air route in its quest to head off the ZX-6R.
So I did another track day on Sunday, same track but I swapped back stock intake snorkel to get some data with OEM set up to compare with RAM CAI. The only difference between the two track days was temperature/humidity. RAM CAI was run with ambient temperature in the low 70s and higher humidity while OEM intake was run on much cooler day where high temperature barely reached 60F with much colder morning. This shows in IAT. Despite this both intakes produced evenly matched MAR g/s readings overall, however my lap times were consistently faster with RAM intake despite higher IATs. You can see speed and MAF reading rebounds faster with RAM vs OEM intake between gear shifts and off/on throttle transitions.
Last edited by Nadrealista; 03-16-2021 at 12:06 PM.
Hm looks like I need to make lip on my intake scoop edges, essentially roll them backwards like in figure 9.
Scoop looks like this now:
Would something like this ram more air in despite being smaller?
Inlet Size (Pipe Side): 4" (101.6mm); Outlet Size (Bell Side): 170mm
My scoop is 4.5"x8.5" so 38.5 sq inches of area, where this velocity stack is going to have ~ 29 sq inches area. Clearly airflow through it would be smoother but air still has get though the hose/airbox/filter and there is velocity stack in the airbox that will smooth it out. so goal here is to get as much air as possible into airbox and create a bit positive pressure in there...
Last edited by Nadrealista; 03-16-2021 at 02:56 PM.
If you want to see if the intake is performing better, pick one speed, let's say 70mph, and WOT condition, and boxplot the MAF rate for both days at that speed. Those graphs are obfuscating the real story, need quantitative methods to tease out small differences.
There are many reasons you may have gone faster or slower on a given best lap. It actually looks like the Ram best lap gained speed slower than stock in the second half. For the most part it looks like you did a couple of turns better to get the better laptime, your top speeds are pretty samey. You'd expect more power to make you faster after a straight.
If you want to see if the intake is performing better, pick one speed, let's say 70mph, and WOT condition, and boxplot the MAF rate for both days at that speed. Those graphs are obfuscating the real story, need quantitative methods to tease out small differences.
There are many reasons you may have gone faster or slower on a given best lap. It actually looks like the Ram best lap gained speed slower than stock in the second half. For the most part it looks like you did a couple of turns better to get the better laptime, your top speeds are pretty samey. You'd expect more power to make you faster after a straight.
There are many ways to slice and dice the data, but my main takeaway is that with RAM intake I was able to consistently run faster laps (1 sec faster on average over the whole day - see last table in my post) despite higher IATs (RAM intake day was hotter than OEM intake track day, there was 10-8C delta in coolant temps and 3-4C delta in IATs). I can send you the file with data if you want to play with it.
Last edited by Nadrealista; 03-17-2021 at 02:57 PM.
03-02-2021, 05:05 PM
