The truth about "ram air"
Re: The truth about "ram air"
North American P-51 mustang was among the first planes that used LAMINAR wing shapes to assist the performance and flight range [ Berlin ]. Turbulance is lost power and not desired.
Some of the new lennox heat pumps that I deal with have SPECIAL shape blades and FLAT grill fins to reduce turbulence, I.E. Noise. Noise is a sign of turbulence and it is a selling point when the outdoor unit is not so noisy that you have to yell on your own back deck as it starts up.
THis is why I shaved the inlet of the throttle body and rounded the throttle plate as the air velocity is on the order of 175 MPH !!!!!!! Thats big if your having eddies or turbulence form at that point.
Woody
Please enjoy the read about the wing c/o NACA.
North American P-51 Mustang - USA
WW
Woody
Some of the new lennox heat pumps that I deal with have SPECIAL shape blades and FLAT grill fins to reduce turbulence, I.E. Noise. Noise is a sign of turbulence and it is a selling point when the outdoor unit is not so noisy that you have to yell on your own back deck as it starts up.
THis is why I shaved the inlet of the throttle body and rounded the throttle plate as the air velocity is on the order of 175 MPH !!!!!!! Thats big if your having eddies or turbulence form at that point.
Woody
Please enjoy the read about the wing c/o NACA.
North American P-51 Mustang - USA
WW
Woody
Re: The truth about "ram air"
Turbulent flow does have its uses when cooling, lamina flow does not scour the surface to be cooled and the boundary surface layer impedes efficient cooling. Turbulent flow removes the boundary, which is slow moving and the turbulent air or water contacts the surface to be cooled.
The boundary layer can be seen on the hood of your car when it is raining, the rain water slowly rolls rearward instead of moving at the speed of the car. When the water reaches the limit of the boundary it flies off in an instant. This is more evident on some cars than others.
You want lamina flow over your car but not over surfaces to be cooled.
Lamina flow occurs when the volume passing through a pipe is insufficient, increasing the flow or reducing the size of the pipe will create turbulent flow. The design secret is to achieve the desired cooling rate with the least amount of fluid.
The boundary layer can be seen on the hood of your car when it is raining, the rain water slowly rolls rearward instead of moving at the speed of the car. When the water reaches the limit of the boundary it flies off in an instant. This is more evident on some cars than others.
You want lamina flow over your car but not over surfaces to be cooled.
Lamina flow occurs when the volume passing through a pipe is insufficient, increasing the flow or reducing the size of the pipe will create turbulent flow. The design secret is to achieve the desired cooling rate with the least amount of fluid.
Re: The truth about "ram air"
Originally Posted by onehundred80
Yeah, this thread fizzled out like a damp cracker on the fourth of July.
I've been too busy to give this the attention I planned.
No time for research
Given the latitude and forgiveness of this bunch when it comes to facts of importance and spelin' I don't want to guess or shoot from the hip.
Although I will say Tom 2112 nailed it on laminar. The only thing I could add is that that the cars, on his laminar chart, do not all have to travel the same speed but may have progressively different speeds going from one side of the road to the other.
And maybe Woody was, but I know I did, look at the honeycomb for reducing turbulence in the CAI. No significant change in performance.
Later
roadster with a stick
Last edited by Franc Rauscher; 03-18-2010 at 04:43 PM.
Re: The truth about "ram air"
High efficiency coolers and radiators actually have turbulators in them to mess with the flow and scratch off the boundry.. Even Gas water heaters have a twisted bar in the stack to twist and stir the exhaust gasses for more efficiency. Woody
Turbulator - Wikipedia, the free encyclopedia
Boiler Efficiency
Turbulator - Wikipedia, the free encyclopedia
Boiler Efficiency
Re: The truth about "ram air"
the best option is to have a velocity stack on the end of the intake, to smooth out flow and make it laminar.
alot of high end filters (aem for example) have a molded quasi-velocity stack at the base of their filters that accomplishes near the same thing while providing proper filtration
alot of high end filters (aem for example) have a molded quasi-velocity stack at the base of their filters that accomplishes near the same thing while providing proper filtration
Re: The truth about "ram air"
I am no technical expert on all of this RAM AIR stuff, but I have a buddy who races Miatas and has experimented extensively with various CAI systems. He told me that just running a Dyno does not begin to show the performance gain. The faster you drive (to a point I am sure) the more air will be pulled in. The "cleaner" the design without extra turbulence will be something you feel that cannot be measured on a Dyno. At least that is what he told me.
Re: The truth about "ram air"
Originally Posted by 240M3SRT
I just dont know. The article does make sense.
But the dual cai with both filters (or scoops) on front does seem to be superior to the others.
But the dual cai with both filters (or scoops) on front does seem to be superior to the others.
Air entering the intake because the engine is pulling it out the other end is a normal function. Adding air to to the intake by force without the expense of using additional energy can only be a plus.
Logic therefore dictates that ram air is likely a positive force in the performance of the engine. The question remains, how much.
My experiments did not measure air compression of any significance. However they did measure higher static manifold pressure despite changes in the exhaust orfices used on the ram tube.
A closed 4.0" ram tube held 6 inches at 60MPH.
It read the same whether we had a 1/4" exhaust orfice or a 2.0"orfice suggesting some compression occured. At 4 .0" exhaust the presure dropped to 0 but was not measurably negative.
If, the intake opening allows enough air to enter to exceed the exiting orfice consumption( or bleed) then the manifold pressure should stay positive. This suggests more available air to the engine provided by the vehicle movement than just by the intake stroke of the cylinder. In other words, the piston does not have a negative force, or as much negative force, as a result of drawing it's air.
Further, since the manifold pressure is maintained higher, there is more oxygen available for the burn.
As you have noted, unless done in a wind tunnel, the dyno could not measure a performance gain. But simple logic suggest one must exist.
I would agree with your conclusions that the forced air intakes in the front would be superior unless tempeature factors are involved.
roadster with a stick
Last edited by Franc Rauscher; 05-02-2010 at 10:24 AM.
Re: The truth about "ram air"
I once saw a bird fall from a tree in the backyard and at the same instant heard a loud crashing noise from the frontyard so I ran around quickly to investigate. To my surprise there was a bus crashed into a tree in the neighbors driveway. If I had not seen it for myself I would have never imagined a bird falling out of a tree could cause a bus to crash...........
This article on Ram air theory is about as questionable as the previous paragragh
Ram air provides benefits on cars , motorcycles and aircraft.
This article on Ram air theory is about as questionable as the previous paragragh
Ram air provides benefits on cars , motorcycles and aircraft.
Join Date: Jan 2008
Location: Long Island, NY
Age: 37
Posts: 2,009
Likes: 0
Received 2 Likes
on
2 Posts
Thread
Thread Starter
Forum
Replies
Last Post
psuperti
Troubleshooting & Technical Questions & Modifications
85
10-15-2012 03:56 AM
Currently Active Users Viewing This Thread: 3 (0 members and 3 guests)