CAI Length/diameter calculation
CAI Length/diameter calculation How would you determine the ideal length & diameter tubing for a custom CAI for LS2? Would you assume the factory setup was ideal or is there a calculation that you can run to determine what is optimal?
I am trying to run one on my TBSS, but I'm concerned that the pipe diameter and or length will ultimately hamper performance.
If you were able to design a "ram air" intake how would you factor the ram effect into this equation (ie is there a forumla for speed x intake diameter x some coeffiecient=ram effect (cfm) or something like that?
Its been a long time since physics and my knowledge ran out a long time ago.
I am trying to run one on my TBSS, but I'm concerned that the pipe diameter and or length will ultimately hamper performance.
If you were able to design a "ram air" intake how would you factor the ram effect into this equation (ie is there a forumla for speed x intake diameter x some coeffiecient=ram effect (cfm) or something like that?
Its been a long time since physics and my knowledge ran out a long time ago.
I would think that the longer the length, the larger diameter would be needed. The factory stuff is done for packaging and placement and not performance or power. Just look at how many different baffles and turns there are. A lot of that stuff is there to 'quiet' down the intake because most people don't want to hear the motor at all.
Ram air doesn't do a thing unless you are trapping like 150 in the quarter. I'll bet you aren't.
CAI are more there to straighten out the airflow. The factory stuff is no where near ideal for making power. It's designed to be quiet and not whistle.
A 4" pipe with few bends will net the most gain for your setup.
Or just buy a setup made by K&N or see what the sponsors have to offer.
CAI are more there to straighten out the airflow. The factory stuff is no where near ideal for making power. It's designed to be quiet and not whistle.
A 4" pipe with few bends will net the most gain for your setup.
Or just buy a setup made by K&N or see what the sponsors have to offer.
Is there any "proof" of the speed at which the "ram" effect happens? I'm just asking in an effort to learn. There are calculations for everything that's why I'm posting here. I talked with a CAI company and got some forumlas for calculating filter surface area needed for the 6.0L NA and with FI. There has to be specific info like that for these other isssues. By knowing the answers you can design a more efficient set up (ie don't over-build the setup do only was the engine needs).
The speed at which "ram-air" can have any real effect is easily calculated. The problem is that no one wants to hear the answer. You have to be running damn near 200mph to achieve 1 full psi of "ram-air" boost. The best that can realistically be expected of an airbox is to minimize restriction and provide unheated air to the motor. As far as tuned length, that can mostly be tossed out the window until you get behind the throttle body, after which it becomes very important.
Gray at SAM said the SAM SS race car trapped 149 with a regular induction system, and 150 with a ram-air type system, with no difference in ET. Don't waste your time unless you plan on going that fast. Even then, it's not a big deal.
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Even then, its still not statistically significant... Too many variables will still wash the 150 vs 149 as meaningless.
And further to the point, ramair will depend on how much air is on it, and technically the air will slightly compress negating any "cold air" benefit it might have added. Thought id add that to the fire.
And further to the point, ramair will depend on how much air is on it, and technically the air will slightly compress negating any "cold air" benefit it might have added. Thought id add that to the fire.
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Even then, its still not statistically significant... Too many variables will still wash the 150 vs 149 as meaningless.
And further to the point, ramair will depend on how much air is on it, and technically the air will slightly compress negating any "cold air" benefit it might have added. Thought id add that to the fire.
And further to the point, ramair will depend on how much air is on it, and technically the air will slightly compress negating any "cold air" benefit it might have added. Thought id add that to the fire.
You can achieve about .1 psi of boost at 75 mph with ram air. I did the calculations once for my Mercedes 300SD turbo diesel and it saved about 1/3 a hp of work done by the turbocharger just to compress the volume of air to an additional 0.1 psi . For a gasoline engine you would gain more power because unlike a diesel the air/fuel ratio is fixed. On a normally aspirated v8 engine you would pickup something like an additional 2 to 4 cfm of air flow.
The formula for calculating optimum ram air intake area requires you to know the cfm flow of the engine at a particular speed.
area in square feet = (cfm/60) / feet per second
ummm.... how will compressing cold air, thus making it even denser, negate any cold air benefits?
You can achieve about .1 psi of boost at 75 mph with ram air. I did the calculations once for my Mercedes 300SD turbo diesel and it saved about 1/3 a hp of work done by the turbocharger just to compress the volume of air to an additional 0.1 psi . For a gasoline engine you would gain more power because unlike a diesel the air/fuel ratio is fixed. On a normally aspirated v8 engine you would pickup something like an additional 2 to 4 cfm of air flow.
The formula for calculating optimum ram air intake area requires you to know the cfm flow of the engine at a particular speed.
area in square feet = (cfm/60) / feet per second
You can achieve about .1 psi of boost at 75 mph with ram air. I did the calculations once for my Mercedes 300SD turbo diesel and it saved about 1/3 a hp of work done by the turbocharger just to compress the volume of air to an additional 0.1 psi . For a gasoline engine you would gain more power because unlike a diesel the air/fuel ratio is fixed. On a normally aspirated v8 engine you would pickup something like an additional 2 to 4 cfm of air flow.
The formula for calculating optimum ram air intake area requires you to know the cfm flow of the engine at a particular speed.
area in square feet = (cfm/60) / feet per second
PV = nRT
P = pressure
V = volume
n = number of moles (lets say oxygen here)
R = constant
T = temperature.
Since the equation is an equilibrium, if we raise pressure, then as a result the temperature will also rise. Hence, this is why a turbo charger or turbo charger uses some type of intercooler. Granted, n, the number or moles of oxygen will rise, it is not as dramatic as the increase in pressure, hence the dramatic temperature rise.
http://www.7stones.com/Homepage/Publisher/Thermo1.html
This is the theory behind why you need a bottle heater for a nitrous bottle. As the pressure drops, it gets cold, as you heat it, the pressure goes up. Same thing with an intake stream. As you increase the pressure, ultimately the temp will go up a little bit.
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Pharmd,
perhaps this link will help
http://web.archive.org/web/200504220.../faq/naca.html
Note: Any where engine demand exceeds the ram air supply you will not achieve maximum possible ram air pressure. It will however provide some benefit .
The Alchemist,
Yes I'm aware of Boyles law. I also know how to apply it.
The only real reason you want cold air is because its denser than warm air. By compressing the air it should make it more dense and therefore allowing you to cram more of it into your cylinders.
Are you suggesting that a ram air system as it compresses the air raises its temp enough to make it less dense? (slight sarcasm implied)
perhaps this link will help
http://web.archive.org/web/200504220.../faq/naca.html
Note: Any where engine demand exceeds the ram air supply you will not achieve maximum possible ram air pressure. It will however provide some benefit .
The Alchemist,
Yes I'm aware of Boyles law. I also know how to apply it.
The only real reason you want cold air is because its denser than warm air. By compressing the air it should make it more dense and therefore allowing you to cram more of it into your cylinders.
Are you suggesting that a ram air system as it compresses the air raises its temp enough to make it less dense? (slight sarcasm implied)
Pharmd,
The Alchemist,
Yes I'm aware of Boyles law. I also know how to apply it.
The only real reason you want cold air is because its denser than warm air. By compressing the air it should make it more dense and therefore allowing you to cram more of it into your cylinders.
Are you suggesting that a ram air system as it compresses the air raises its temp enough to make it less dense? (slight sarcasm implied)
The Alchemist,
Yes I'm aware of Boyles law. I also know how to apply it.
The only real reason you want cold air is because its denser than warm air. By compressing the air it should make it more dense and therefore allowing you to cram more of it into your cylinders.
Are you suggesting that a ram air system as it compresses the air raises its temp enough to make it less dense? (slight sarcasm implied)
Again, I wasn't arguing the fact that it raises the temp enough to be an issue, just explaining why.
I believe boyle's law is a moot point in this case being that volume and number of moles are pretty well infinite in this case. I've seen actual pressure charts done on the viper naca duct intake and it was barely achieving 1psi of boost in the intake at 180+ MPH, ram air, while a novel idea seems to be almost a waste of time. Intake design is not however. Consider you air filter as a restriction between your throttle body and the real world, with this done you can start to think of your intake as a 2nd plenum feeding the motor, however no matter how large you make your CAI it will not hurt throttle response in any measureable way. A year or two ago I read an article in some ricer mag where they had tested various intake resonator (that thing most people remove) sizes on a honda with a stock intake setup. The larger the resonator (and intake volume) the more air was instantly available to the motor. I'll see if I can dig the article up but in a short story they wound up trying a 2 liter bottle at the end and posted some gains of 5 ft/lbs across the entire RPM band over a stock intake setup. CAI volume and size do matter but basically you want it to be as large as physically possible.
Who's arguing?
Agreed on 4" pipe, don't see any real gains over anything bigger, 4" is monsterous anyways.
Why not use some of this stuff until you find a location/routing you're happy with.
http://www.allstarperformance.com/product.htm?prod=592
Agreed on 4" pipe, don't see any real gains over anything bigger, 4" is monsterous anyways.
Why not use some of this stuff until you find a location/routing you're happy with.
http://www.allstarperformance.com/product.htm?prod=592
Last edited by Drew04GTO; Nov 3, 2007 at 01:14 AM.
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ram air does work and its more than just a cold air intake.
dyno results
http://www.sportrider.com/tech/146_9912_ram/index.html
Now the exact conditions can't be duplicated using the method they used to generate the ram air, however their method wont work as well as true ram air due to the temperature increase by use of the compressors. Any gains by ram air would be higher than these tests.
dyno results
http://www.sportrider.com/tech/146_9912_ram/index.html
Now the exact conditions can't be duplicated using the method they used to generate the ram air, however their method wont work as well as true ram air due to the temperature increase by use of the compressors. Any gains by ram air would be higher than these tests.
No ConnClark, it does not make any real difference other than providing cooler air. At WOT air is moving into the intake @ ~200 mph. How is a ram effect of 80 or 100 or 150 mph going to provide a pressure increase? Think about it.
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It will make a difference. At about 70 mph you get about 0.1 psi of boost. On most v8s that gets you about 2 hp and 2ft-lbs.
Go here and plug in the bore and stroke of your engine. set the boost and intercooler efficiency to 0. Look at the difference in torque and hp at an altitude of 0 and 190 feet.
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml
Go here and plug in the bore and stroke of your engine. set the boost and intercooler efficiency to 0. Look at the difference in torque and hp at an altitude of 0 and 190 feet.
http://www.not2fast.com/turbo/glossary/turbo_calc.shtml