CAI design and assoc power losses and gains?
06-16-2003, 11:37 PM
#1
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CAI design and assoc power losses and gains?
I was wondering if we could take an advanced look at the design of the available CAI's for LT1's. I know the debate has been ongoing between Ram Air and the traditional CAI as far as which makes more power and the Ram Air always seems to pick up a MPH or two.
What I want to know is how much if any air flow is lost in the two 90* bends the air is forced to take. Is a straight shot design better since the air has no turns to take? Since GM utilizes a straight shot design for the LSx motors it would be assumed that this would be a superior design.
What got me thinking was this set up right here . Would this set up have the potential to make more power? It suppossedly is used on the fastest cammed/stock LT1 in the country.
Better yet(this is assuming no MAF ie. speed density LT1's) why not just stick an air filter on the TB?
What I want to know is how much if any air flow is lost in the two 90* bends the air is forced to take. Is a straight shot design better since the air has no turns to take? Since GM utilizes a straight shot design for the LSx motors it would be assumed that this would be a superior design.
What got me thinking was this set up right here . Would this set up have the potential to make more power? It suppossedly is used on the fastest cammed/stock LT1 in the country.
Better yet(this is assuming no MAF ie. speed density LT1's) why not just stick an air filter on the TB?
06-17-2003, 02:49 AM
#2
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it's even better when you add the rest of that intake
http://www.impalaperformance.com/pho...lled_2_big.jpg
The problem with doing that on an F-body is the lack of room between the TB and radiator.
http://www.impalaperformance.com/pho...lled_2_big.jpg
The problem with doing that on an F-body is the lack of room between the TB and radiator.
06-17-2003, 06:18 AM
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You want the densest possible air charge in the cylinder. This means you need the highest possible pressure AND the lowest possible temperature. The temperature is going to be determined solely by where you pick the air up at.... outside the engine compartment is generally cooler than right above the radiator.
Pressure is a little more difficult. The ambient air pressure is "fixed", but the fact that the car is moving alters the pressure available on the various surfaces of the car.... air pressure builds in places like the point where the hood and the windshield meet, and it can be either positive or negative (relative to ambient) at other points on the surface of the body. You want to take air from the highest pressure point. The surface of the hood, midway from the bumper to the widnshield (ala SS) is probably one of the worst locations, since the boundary layer of slow moving air generally occurs there. That's why the Pro Stock "scoops" are located 12-18" above the hood, to get out of the boundary layer, where pressure is unaffected by the boundary layer. The NACA style ducts are beneficial, as I recall, because they allow the boundary layer to seperate and leave the path open to air flow into the opening.
Once you find the high pressure point, you need to be able to move the air to the intake manifold. Anything that touches the air will likely reduce its pressure. The friction from the side of the tubing, any bends, sudden contractions or enlargements, or any kind of obstruction in the duct work. A 90-deg bend costs pressure drop, so straighter is better. A sudden enlargement causes pressure drop, so a tapered transition is better, and the angle of the transition can be optimized.
So, directionally:
-find a high pressure area on the body, that is near the intake
-stick an large opening, with rounded edges facing the front of the vehicle, to pick up "velocity head" (ram air) - not as much as its made out to be
-use the largest diameter, shortest length, straightest connecting path you can find.
-minimize or "streamline" any obstructions.
Just to put the ram air concept into perspective, you can do some rough calculations that indicate, if you are lucky, you might add 1% to the air pressure at 100mph..... so you have the potential to add maybe 1% power through the "ram air" or velocity head affect. A poorly designed opening can destroy most of the potential gain. And the pressure "boost" is proportional to the square of the velocity, so at 50mph, it pretty much dissapears.
When running a mass-air sensor, you also need to be sensitive the the uniformity of the air as it approaches and leaves the sensor. The screen is there to provide a nominal pressure drop that smooths the air flow, distributing it uniformly accross the cross-section of the sensor, and eliminating some turbulance.
That ought to be enough to get things started.
My approach
Pressure is a little more difficult. The ambient air pressure is "fixed", but the fact that the car is moving alters the pressure available on the various surfaces of the car.... air pressure builds in places like the point where the hood and the windshield meet, and it can be either positive or negative (relative to ambient) at other points on the surface of the body. You want to take air from the highest pressure point. The surface of the hood, midway from the bumper to the widnshield (ala SS) is probably one of the worst locations, since the boundary layer of slow moving air generally occurs there. That's why the Pro Stock "scoops" are located 12-18" above the hood, to get out of the boundary layer, where pressure is unaffected by the boundary layer. The NACA style ducts are beneficial, as I recall, because they allow the boundary layer to seperate and leave the path open to air flow into the opening.
Once you find the high pressure point, you need to be able to move the air to the intake manifold. Anything that touches the air will likely reduce its pressure. The friction from the side of the tubing, any bends, sudden contractions or enlargements, or any kind of obstruction in the duct work. A 90-deg bend costs pressure drop, so straighter is better. A sudden enlargement causes pressure drop, so a tapered transition is better, and the angle of the transition can be optimized.
So, directionally:
-find a high pressure area on the body, that is near the intake
-stick an large opening, with rounded edges facing the front of the vehicle, to pick up "velocity head" (ram air) - not as much as its made out to be
-use the largest diameter, shortest length, straightest connecting path you can find.
-minimize or "streamline" any obstructions.
Just to put the ram air concept into perspective, you can do some rough calculations that indicate, if you are lucky, you might add 1% to the air pressure at 100mph..... so you have the potential to add maybe 1% power through the "ram air" or velocity head affect. A poorly designed opening can destroy most of the potential gain. And the pressure "boost" is proportional to the square of the velocity, so at 50mph, it pretty much dissapears.
When running a mass-air sensor, you also need to be sensitive the the uniformity of the air as it approaches and leaves the sensor. The screen is there to provide a nominal pressure drop that smooths the air flow, distributing it uniformly accross the cross-section of the sensor, and eliminating some turbulance.
That ought to be enough to get things started.
My approach
Last edited by Injuneer; 06-17-2003 at 06:21 AM.
06-17-2003, 03:22 PM
#4
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Fred, what do you think of the RAISS intake for the Impala SS that I linked to?
- the grille has got to have high pressure
- grille again
- The diameter is 3" with the stock B-body MAF, but larger if you go with an F-body MAF. There is a sheild directing some of the air for the radiator up over the radiator support and under the hood into a scoop. The length from the base of the air filter to the TB is the length of the MAF plus about 3-4 inches. On my car the TB is lower than the scoop, but it's a straighter shot than the fender mount air pickup.
Originally posted by Injuneer
So, directionally:
-find a high pressure area on the body, that is near the intake
-stick an large opening, with rounded edges facing the front of the vehicle, to pick up "velocity head" (ram air) - not as much as its made out to be
-use the largest diameter, shortest length, straightest connecting path you can find.
-minimize or "streamline" any obstructions.
So, directionally:
-find a high pressure area on the body, that is near the intake
-stick an large opening, with rounded edges facing the front of the vehicle, to pick up "velocity head" (ram air) - not as much as its made out to be
-use the largest diameter, shortest length, straightest connecting path you can find.
-minimize or "streamline" any obstructions.
- grille again
- The diameter is 3" with the stock B-body MAF, but larger if you go with an F-body MAF. There is a sheild directing some of the air for the radiator up over the radiator support and under the hood into a scoop. The length from the base of the air filter to the TB is the length of the MAF plus about 3-4 inches. On my car the TB is lower than the scoop, but it's a straighter shot than the fender mount air pickup.
06-17-2003, 11:45 PM
#5
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I really don't know where the air comes from in that setup.... are you saying it is breathing air that came through the grill? Does it flow below the front plate and enter a slot in the front of the box, with the rear box sealed to the closed hood? It looks like it would be a great setup with a scoop at the leading edge of the hood.
Is there any insulating material on what appears to be the aluminum shield? Doesn't that cone filter look a little small, considering the lower 1/4 of it appears to be shielded?
I like it, except for the items noted above.
Is there any insulating material on what appears to be the aluminum shield? Doesn't that cone filter look a little small, considering the lower 1/4 of it appears to be shielded?
I like it, except for the items noted above.
06-18-2003, 01:48 AM
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For the most part I agree with injuneer hear, but would like to add, that in general, actual airflow is not the issue here (should be sufficient with any of these setups), the air temp is. Lower air temps not only let you make more power because of a denser air/fuel charge, but intake air temp has a significant impact on detonation sensitivity. Now in general, the higher you get your air off the ground, the lower the air temp will be. On a sunny summer day I once tested air temps to be 18* higher within 1’ of the ground then they were at 4’. WRT to the open air cleaner element exposed to air in the engine compartment (behind the radiator) that’s a bad idea all around.
06-18-2003, 09:31 AM
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Originally posted by WS6 TA
For the most part I agree with injuneer hear, but would like to add, that in general, actual airflow is not the issue here (should be sufficient with any of these setups), the air temp is. Lower air temps not only let you make more power because of a denser air/fuel charge, but intake air temp has a significant impact on detonation sensitivity. Now in general, the higher you get your air off the ground, the lower the air temp will be. On a sunny summer day I once tested air temps to be 18* higher within 1’ of the ground then they were at 4’. WRT to the open air cleaner element exposed to air in the engine compartment (behind the radiator) that’s a bad idea all around.
For the most part I agree with injuneer hear, but would like to add, that in general, actual airflow is not the issue here (should be sufficient with any of these setups), the air temp is. Lower air temps not only let you make more power because of a denser air/fuel charge, but intake air temp has a significant impact on detonation sensitivity. Now in general, the higher you get your air off the ground, the lower the air temp will be. On a sunny summer day I once tested air temps to be 18* higher within 1’ of the ground then they were at 4’. WRT to the open air cleaner element exposed to air in the engine compartment (behind the radiator) that’s a bad idea all around.
Originally posted by Injuneer
You want the densest possible air charge in the cylinder. This means you need the highest possible pressure AND the lowest possible temperature. The temperature is going to be determined solely by where you pick the air up at.... outside the engine compartment is generally cooler than right above the radiator.
You want the densest possible air charge in the cylinder. This means you need the highest possible pressure AND the lowest possible temperature. The temperature is going to be determined solely by where you pick the air up at.... outside the engine compartment is generally cooler than right above the radiator.
06-18-2003, 03:00 PM
#9
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Since we are talking about cold air induction and one of the most common "old school" cold air intakes has to do with a cowl induction hood, I've got a question about them.
How would a cowl induction hood with a 2" lift compare to a forward facing scoop only 2" off the hood?
About how high is the boundary layer on cars up to 100mph?
And Fred, I was just about to answer some of your questions about that intake I posted about, but I had another thought about it that I'm going to try out before posting about that again
How would a cowl induction hood with a 2" lift compare to a forward facing scoop only 2" off the hood?
About how high is the boundary layer on cars up to 100mph?
And Fred, I was just about to answer some of your questions about that intake I posted about, but I had another thought about it that I'm going to try out before posting about that again
06-18-2003, 06:29 PM
#10
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Originally posted by AdioSS
And Fred, I was just about to answer some of your questions about that intake I posted about, but I had another thought about it that I'm going to try out before posting about that again
And Fred, I was just about to answer some of your questions about that intake I posted about, but I had another thought about it that I'm going to try out before posting about that again
There is just over 1" of clearance between the hood and radiator support. However, the scoop is 32" wide so that's 32 square inches of air, right? That is about 3 times as much as will fit in the MAF at any time...
What do you guys think?
06-19-2003, 04:52 PM
#11
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i am using http://bellsouthpwp.net/L/T/LT1ultraz/Mods/FIPK.jpg
LS1 K&N FIPK..it fits right in the UltraZ hoods opening, and i have a space under the filer cutout as well for some more air
Seems to work pretty well. I was wondering if i would benefit if i went with a LS1 Lid/FTRA combo?
Thanks
Marcin
LS1 K&N FIPK..it fits right in the UltraZ hoods opening, and i have a space under the filer cutout as well for some more air
Seems to work pretty well. I was wondering if i would benefit if i went with a LS1 Lid/FTRA combo?
Thanks
Marcin
06-19-2003, 05:01 PM
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Marcin, I think you would benefit a little from having the FTRA. I have always liked your setup like that but need an after market hood for it to work. There has got to be a way to pull some cold air from under the front nose straight up without a modified hood. Since I removed the AC, there is a lot more room in there now with the condensor out. Maybe I will try fabbing something up after I get this cam installed. Bye Bye to my new Vortech elbow if that happens.
Marcin, you ever try switching between your setup and a regular CAI at the track or dyno to see what kind of results there are? I am interested to see.
Marcin, you ever try switching between your setup and a regular CAI at the track or dyno to see what kind of results there are? I am interested to see.
06-19-2003, 05:58 PM
#13
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i have always wondered about combining the two types of cai/ram air. imagine the stock ws6 box but the elbow branches off to a T and there is also a cold air system rigged up there. would that work at all
like this
ramair--- T------maf--etc....
...............l
...............l
...............l
........CAI
watcha think?
like this
ramair--- T------maf--etc....
...............l
...............l
...............l
........CAI
watcha think?
06-19-2003, 10:16 PM
#14
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In theory, the "ram air" intake builds pressure. The potential at 100mph is 0.18psi. (You will not "recover" all of it though). If you put another connection between the ram air inlet and the intake manifold, you could just be bleeding off that little bit of pressure, particularly if your "cold air" system happened to be connected to a body location that suffered from reduced pressure at high speed. And as pointed out above, the air a couple feet above the road is always cooler than the air right on the road..... asphalt is a giant sponge for solar heating.... 150deg asphalt isn't unheard of.
Adding the FTRA (I assume you mean cutting the opening in the bottom of the LS1 airbox to allow air to flow in from below as well as up high from the hood) might have the same affect.
All of this is sort of like "tilting at windmills"..... you are not going to gain of lose a lot of pressure based on where you get the air. The sensitivity to temperature is probably more important. Cooling the intake air 10degF can easilly gain you 1.8% on density = power.
Adding the FTRA (I assume you mean cutting the opening in the bottom of the LS1 airbox to allow air to flow in from below as well as up high from the hood) might have the same affect.
All of this is sort of like "tilting at windmills"..... you are not going to gain of lose a lot of pressure based on where you get the air. The sensitivity to temperature is probably more important. Cooling the intake air 10degF can easilly gain you 1.8% on density = power.
Last edited by Injuneer; 06-19-2003 at 10:22 PM.
06-20-2003, 03:09 AM
#15
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Interesting thread. Intuitively it makes sense to get the air from outside the boundary layer. But wouldn't the pressure outside the boundary layer be free-stream/atmospheric pressure? And that would defeat the purpose of pressure increase??
Boundary Layer for a Camaro at 100 mph, assuming flow is incompressible (due to low speed) + lamilar flow is about..oh.. .2-.5 inches from the car surface..
Temperature reasons make perfect sense. Get the scoop as high as you can where the air is cooler and a bit more dense.
The intake cooling thing has me going as I just told my buddy heat shielding the entire intake won't do much for power..
It's more important to get the intake charge from a cold source then keep the actual intake pipe/filter cool right??
Considering the air intake charge doesn't seen more then a second of heating in the intake piping/filter/throttle body/intake manifold?? I see a lot of folks at the track icing their intake manifolds and piping..Just Wondering.
Alex
Boundary Layer for a Camaro at 100 mph, assuming flow is incompressible (due to low speed) + lamilar flow is about..oh.. .2-.5 inches from the car surface..
Temperature reasons make perfect sense. Get the scoop as high as you can where the air is cooler and a bit more dense.
The intake cooling thing has me going as I just told my buddy heat shielding the entire intake won't do much for power..
It's more important to get the intake charge from a cold source then keep the actual intake pipe/filter cool right??
Considering the air intake charge doesn't seen more then a second of heating in the intake piping/filter/throttle body/intake manifold?? I see a lot of folks at the track icing their intake manifolds and piping..Just Wondering.
Alex