Ram air effect Air Box's????
Discussion
In my normal 'can't leave alone' way I have recently been thinking about fabricating an air box.
Two reasons.
1. to take full advantage of the air flow into the front scoop ensuring only cool air is collected by the air filter.
2. To stop hot air comming out of the scoop without just blocking it up and encouraging the engine to suck yet more hot air in!
Having read other threads I know I am not alone (STIG
).
I intend to fabricate one from Fibreglass to get a mould then make a final one out of Carbon fibre.
Has anyone done this?
Any other points or ideas before I (We) make a terrible mistake?
Two reasons.
1. to take full advantage of the air flow into the front scoop ensuring only cool air is collected by the air filter.
2. To stop hot air comming out of the scoop without just blocking it up and encouraging the engine to suck yet more hot air in!
Having read other threads I know I am not alone (STIG
). I intend to fabricate one from Fibreglass to get a mould then make a final one out of Carbon fibre.
Has anyone done this?
Any other points or ideas before I (We) make a terrible mistake?
A cold air box is very different from a RAM air box. RAM air is a type of forced induction that requires the airbox to be pressurised (not much good with a supercharger as the effect will be negligable) and this involve usually a series of pressure flaps to maintain the pressure in the airbox. It is very difficult to perfect (Honda spent millions developing RAM air for the CBR600).
If you just use a foward facing air scoop you will more than likely take in very turbulent air ruining fuel metering. The air needs to be drawn from a low pressure point on the bodywork and this involves windtunnel testing.
A cold air intake is good (fitted to original 427 Cobra's)and is normally just a heatsheild around the carb/airfilter; especially with a supercharged engine that has no intercooler fitted as the air temp. after compression could be critical; maybe consider a water exchange cooler or water injection - this should stop any detonation.
Again the air should be taken from a low pressure point on the body to maximise air charge entering the air filter. Often this is a rearward facing vent that prevents turbulant air entering the carb (if you read the instructions for a pancake airfilter it will tell you not to place it in the airstream!)
>> Edited by TFIVEUK on Monday 27th January 23:52
If you just use a foward facing air scoop you will more than likely take in very turbulent air ruining fuel metering. The air needs to be drawn from a low pressure point on the bodywork and this involves windtunnel testing.
A cold air intake is good (fitted to original 427 Cobra's)and is normally just a heatsheild around the carb/airfilter; especially with a supercharged engine that has no intercooler fitted as the air temp. after compression could be critical; maybe consider a water exchange cooler or water injection - this should stop any detonation.
Again the air should be taken from a low pressure point on the body to maximise air charge entering the air filter. Often this is a rearward facing vent that prevents turbulant air entering the carb (if you read the instructions for a pancake airfilter it will tell you not to place it in the airstream!)
>> Edited by TFIVEUK on Monday 27th January 23:52
I think that you mean a HIGH pressure point, not low pressure. If you look at the Trans Am Ram Air system (which is the only one I can think of on a production car, although I'm sure that there are more), it was rearward facing, just at the bottom of the windscreen. This made use of the high pressure air that exists in this area to give the ram effect.
I've known 2 people who have made DIY Ram Air systems. Although neither of them had access to a wind tunnel, they both managed to improve the power of their engines (although probably not by as great an amount as if they'd spent millions of pounds on wind tunnel testing).
Consultation of some literature on aerodynamics should help you to establish whether there are any suitable areas where you can collect pressurised air for your engine, although, with the low and slippery shape of the Ultima, I can't think of anywhere that immediately springs to mind. Even the bottom of the windscreen isn't going to give you much of a high pressure region, as the screen is so well raked back and curved. Basically, all the bits of the design that make it possible for the car to do 200mph+ are the same things that are going to prevent you using the traditional Ram Air design.
It's probably best just to stick to scooping up as much cold air as possible, and feeding it to your air filter with as little turbulance as possible.
James
Edited to add. The reason for not putting an air filter in the airstream has nothing to do with turbulance. It is because of the venturi effect, which would suck fuel and air out of the air filter (it's the same effect that makes spray guns suck up paint).
If you look at the design of the Ultima, you'll see that the air scoop has been carefully placed in an area where there is not going to be very much turbulance, and is probably about the highest pressure zone on the surface of the car. I know that Ted and co have done some work in the wind tunnel on the car (I saw the pictures). I suspect that one of the things they may have tested is the optimum position and size of the air scoop.
>> Edited by james on Tuesday 28th January 14:56
I've known 2 people who have made DIY Ram Air systems. Although neither of them had access to a wind tunnel, they both managed to improve the power of their engines (although probably not by as great an amount as if they'd spent millions of pounds on wind tunnel testing).
Consultation of some literature on aerodynamics should help you to establish whether there are any suitable areas where you can collect pressurised air for your engine, although, with the low and slippery shape of the Ultima, I can't think of anywhere that immediately springs to mind. Even the bottom of the windscreen isn't going to give you much of a high pressure region, as the screen is so well raked back and curved. Basically, all the bits of the design that make it possible for the car to do 200mph+ are the same things that are going to prevent you using the traditional Ram Air design.
It's probably best just to stick to scooping up as much cold air as possible, and feeding it to your air filter with as little turbulance as possible.
James
Edited to add. The reason for not putting an air filter in the airstream has nothing to do with turbulance. It is because of the venturi effect, which would suck fuel and air out of the air filter (it's the same effect that makes spray guns suck up paint).
If you look at the design of the Ultima, you'll see that the air scoop has been carefully placed in an area where there is not going to be very much turbulance, and is probably about the highest pressure zone on the surface of the car. I know that Ted and co have done some work in the wind tunnel on the car (I saw the pictures). I suspect that one of the things they may have tested is the optimum position and size of the air scoop.
>> Edited by james on Tuesday 28th January 14:56
Probably a bigger effect of a different air supply would be the colder air temperature going into the engine. The air must be well hot if sucked through the air filter in from the engine bay on the Ultima. I have run some software dyno simuations and shown 7-10 bhp and 12-20 ft lbs torque increase over much of the rev range for a 17 degree C drop in temperature.
Simpler solution, add a gurney just inside the scoop to direct the air towards the pancake filter. Otherwise it's more likely to just blow straight over it.
One benefit of the supercharger size is that it puts the filter right under the scoop so gets cool air, but avoids the most turbulent stuff.
Btw - great advice TFIVE.
One benefit of the supercharger size is that it puts the filter right under the scoop so gets cool air, but avoids the most turbulent stuff.
Btw - great advice TFIVE.
james said: I think that you mean a HIGH pressure point, not low pressure. If you look at the Trans Am Ram Air system (which is the only one I can think of on a production car, although I'm sure that there are more), it was rearward facing, just at the bottom of the windscreen. This made use of the high pressure air that exists in this area to give the ram effect.
I've known 2 people who have made DIY Ram Air systems. Although neither of them had access to a wind tunnel, they both managed to improve the power of their engines (although probably not by as great an amount as if they'd spent millions of pounds on wind tunnel testing).
Consultation of some literature on aerodynamics should help you to establish whether there are any suitable areas where you can collect pressurised air for your engine, although, with the low and slippery shape of the Ultima, I can't think of anywhere that immediately springs to mind. Even the bottom of the windscreen isn't going to give you much of a high pressure region, as the screen is so well raked back and curved. Basically, all the bits of the design that make it possible for the car to do 200mph+ are the same things that are going to prevent you using the traditional Ram Air design.
It's probably best just to stick to scooping up as much cold air as possible, and feeding it to your air filter with as little turbulance as possible.
James
Edited to add. The reason for not putting an air filter in the airstream has nothing to do with turbulance. It is because of the venturi effect, which would suck fuel and air out of the air filter (it's the same effect that makes spray guns suck up paint).
If you look at the design of the Ultima, you'll see that the air scoop has been carefully placed in an area where there is not going to be very much turbulance, and is probably about the highest pressure zone on the surface of the car. I know that Ted and co have done some work in the wind tunnel on the car (I saw the pictures). I suspect that one of the things they may have tested is the optimum position and size of the air scoop.
>> Edited by james on Tuesday 28th January 14:56
Interesting reading!!
I have fitted a homemade one-off airbox which has a square K&N inside. It works great. There is a lot of difference between the engine with a regular round filter (sucking hot air) and with the air box flowing the air directly from the air scoop. I think that there are some pic in my page http://personales.jet.es/jmarino
This one-off was a prototype. A new Kevlar/CF is in progress. I have the moulds......yyyuuuujuuuu
This one-off was a prototype. A new Kevlar/CF is in progress. I have the moulds......yyyuuuujuuuu
Gassing Station | Ultima | Top of Page | What's New | My Stuff