Getting air to Turbo

[landracing]

There has been discussion before about intake air ram for NA motors, with most talk about cars. How about bikes. Does the sizing to the intake of the turbo really matter since a turbo in a sense with draw in its own air. I assume there can be some efficiency gained by getting incoming air from the front of the bike and plumbing it to to the intake of the turbo.
How can one decide what size the tubing should be is 2 1/2 to big, or is 2 to small. Like my turbo has an inlet opening of 2 1/4", Wouldn't a 2" tubing to it speed of the velocity of air into the turbo?

Jon

[Peter Jack]

Jon:

Great to see the forums back, THANKS!

My experience tells me that you'd want to keep the passage into the turbo at least the same size as the passage in the turbo itself. I would think that the important thing would be the shape of the intake at the inlet end, i.e. - a bell mouth of some sort. It would also be important that the air into the intake be as little disturbed as possible or definitely rammed. Things to look out for might be flow off the front wheel or a fairing which might limit the airflow to less than one would think. It's possible you might find significant difference between a dyno run and an actual run because of airflow around the bike.

Pete

[landracing]

Peter that is what I was kinda leading to. That on a dyno run all is perfect, usually without bodywork. But actual running of the vehicle with air moving around it, it would seem best to pull air in from the front of the bike. However, real world scenario is it is never a straight shot, it would be a curvy to get there since the air from the front of the bike is usually best in front of the fairing. Now with moving around some corners wouldn't it seem best to increase the diameter of tubing. Like from 2 1/4 to 2 1/2

Jon

[Sumner]

There has been discussion before about intake air ram for NA motors, with most talk about cars. How about bikes. Does the sizing to the intake of the turbo really matter since a turbo in a sense with draw in its own air. I assume there can be some efficiency gained by getting incoming air from the front of the bike and plumbing it to to the intake of the turbo.
How can one decide what size the tubing should be is 2 1/2 to big, or is 2 to small. Like my turbo has an inlet opening of 2 1/4", Wouldn't a 2" tubing to it speed of the velocity of air into the turbo?

Jon

Maybe Mike will jump in here on this, but I was considering a NACA duct on my lakester, but was worried about positioning it in the right place to work.  Mike uses one on Ack Attack, so I asked him.  He said (and Mike correct me if I'm wrong) that if the streamliner was running NA he wouldn't run a NACA duct for concerns about it working correctly, but would use a scoop like we use on the Stude or like on Jack's/Rick's streamliner and others.  He feels that the turbo will get the air it needs and you can supply what you want to the engine with where the boost is set at.

My only concern with that is if you could get 1 to 1 1/2 lbs of free boost with a properly designed scoop then that would be 1 to 1 1/2 lbs less boost that the turbo would have to supply and I would think that then the air would be cooler going to the engine than if the turbo had to compress all of the air for the boost.  Now he is also running an ice water intercooler, so that will probably more than make up for it and also in his case no scoop up there in the air means better aerodynamics which is freeing up HP.

Now for your specific question if I understand it right you could size the scoop opening using the spreadsheets on my site and I think you also might have some.  Mine will allow you to put in the boost factor and will re-size accordingly....

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

If I understand the principal right if you went from a smaller inlet opening and tapered to a larger plenum (maybe in your case right in front of the larger turbo inlet) the air speed is going to drop, but the pressure (good thing) is going to go up.  I think Nish's experimented with all different size plenums and a couple years ago had that monster one on the car.  I think they also have different inlet sizes for different engine combinations.

If I can help in sizing a scoop for your particular situation I'll be glad to,

Sum

[Sumner]

Peter that is what I was kinda leading to..............wouldn't it seem best to increase the diameter of tubing. Like from 2 1/4 to 2 1/2 Jon

If the opening is larger than needed and the motor can't use all the air that is available at the opening then the unused air piles up and has to go around the opening and thus hurts the aero.  This of course is a fine line to walk and who knows without wind-tunnel time what is really happening.  I sized our scoop about 15% large on the Stude.  The less air you have piling up and having to go around the scoop the better, or so it would seem to me,

Sum

[SPARKY]

on the Dyno an Extreme Velocity blower hat cost my 555 80 HP---crossover is around 215 I think---

[Peter Jack]

It always amazes me the number of bikes that pull the air into the engine at 90 degrees to the direction of travel. That generally creates a low or negative pressure at the air inlet entrance.

Pete

[landracing]

Peter that is what I was kinda leading to..............wouldn't it seem best to increase the diameter of tubing. Like from 2 1/4 to 2 1/2 Jon

If the opening is larger than needed and the motor can't use all the air that is available at the opening then the unused air piles up and has to go around the opening and thus hurts the aero.  This of course is a fine line to walk and who knows without wind-tunnel time what is really happening.  I sized our scoop about 15% large on the Stude.  The less air you have piling up and having to go around the scoop the better, or so it would seem to me,

Sum

I guess we are talking two different players here Sum. I am trying to talk about it on a bike and you refer to a scoop on a car. 

So for instance a leading edge on my front fairing with a 2" inch opening, IF this is to small and you say the air piles up, then what does it matter, it would be like the hole never existed and air would flow around the fairing anyway. If it was to large, or at what point is it to large, that is where I am confused.

I tried your worksheet and it didn't prove to me anything, it says I need a 1 1/4 inch opening. That seems kinda small.

Jon

[Sumner]

Peter that is what I was kinda leading to..............wouldn't it seem best to increase the diameter of tubing. Like from 2 1/4 to 2 1/2 Jon

If the opening is larger than needed and the motor can't use all the air that is available at the opening then the unused air piles up and has to go around the opening and thus hurts the aero.  This of course is a fine line to walk and who knows without wind-tunnel time what is really happening.  I sized our scoop about 15% large on the Stude.  The less air you have piling up and having to go around the scoop the better, or so it would seem to me,

Sum

I guess we are talking two different players here Sum. I am trying to talk about it on a bike and you refer to a scoop on a car. 

So for instance a leading edge on my front fairing with a 2" inch opening, IF this is to small and you say the air piles up, then what does it matter, it would be like the hole never existed and air would flow around the fairing anyway. If it was to large, or at what point is it to large, that is where I am confused.

I tried your worksheet and it didn't prove to me anything, it says I need a 1 1/4 inch opening. That seems kinda small.

Jon

The piled up air is turbulent though and not as good as air that just comes straight and hits the fairing. 

The inlets always look small and it will depend on the speed you are figuring for.  Look at the size of ours for 400 blown cubic inches.  Look at Rick's and how small it is for probably 500-600 hp, but it is probably set to work right at over 300.

If it is too small the worst that will happen is you will run rich as you won't be getting enough air.  A lot of these seem small at lower speeds like in our case, but we can't make big HP down there anyway without spinning the tires.

When I came up with the size for the one on the Stude everyone said "too small", but now I don't hear that much any more.  Same when I did the one for Phil's car.  People are so use to seeing the large ones on drag cars that they can't believe one of these small ones will work.  Difference is that they have traction and slipper clutches and need to make big HP while the car is at a relatively slow speed at the beginning of the run so they need a big opening to get the air at that end of the track.

c ya,

Sum

[joea]

x hp requires x cfm, no matter the application usually....

try this great tech article posted on this site many moons ago.....

http://www.landracing.com/index.php?option=com_content&task=view&id=22

positive pressure can be good.......it reduces the difference in pressure between
the inlet and outlet sides of the compressor.......easier work.....less heat as
sum mentioned....

[Peter Jack]

Jon:

Sum may be on to something if you ran a scoop off the fairing facing forward. At the same time I think you may have something in running the larger ducting behind the scoop down to the turbo to make up for the losses through the bends. In that case the transition to the turbo inlet size would probably be critical to eliminate turbulance at the entrance to the turbo.

Pete

[Graham in Aus]

Ricks inlet for N/A 1350 I believe, the intake for the turbo motor was a bit bigger 2" round?

 

I hope he doesn't mind me posting, the pictures are right there on his site 

http://www.yacoucci.com/

[landracing]

Joe,

Did you determine based on that formula from Dr. Mayfield and adequate opening of your turbo application?

If so would you care to share it.

Jon

[landracing]

I made a online form, using the data Dr.Mayfield used and plugged the information in and it comes up just like Sumners formula. I guess It is what it is.

You can try it out here. And ill be creating some more online based forms for other formulas. I have made two try at your own will and results may vary.

http://www.landracing.com/formula/hoodscoop.htm

http://www.landracing.com/formula/nomograph.htm

Jon

[Sumner]

I made a online form, using the data Dr.Mayfield used and plugged the information in and it comes up just like Sumners formula. I guess It is what it is..............Jon

Jon you are right about needing the cfm, but the scoop is moving forward through the air.  Now depending on your tire size, gearing and rpm which will determine how far that scoop moves in two revolutions you will see how much air the scoop "scoops" in during those two revolutions.  Hopefully you size it so that it provides that cfm you need. Take the same motor and put in a slower final gear and then a higher final gear and you will see that the size decreases as the gearing gets higher (bike is faster).  Seeing that you can then put in final gearing for say 3rd, 4th and 5th if you have 6 gears and see that the scoop should be bigger in those gears, but like I posted before you don't usually need all of the HP in the lower gears.  If you do then you are going to have to make a scoop size decision where it might be larger than needed on the top end, but will give you the air you need before that.  As we talked about before with the turbo that isn't as much of a concern, since it will suck in the air it needs unlike a NA motor.

Now think about a hot scoop going through some ice cream.  The scoop will fill itself and leave the the ice cream alone on the sides of it.  That would be the ideal situation with us also, car/bike.  It would be great if our scoop during the distance it travels in two revolutions of the motor (4 stroke) would just slice the amount of air the motor needs and leave the rest undisturbed.  Can we do that exactly, no, but the closer we come the less disturbed air goes past the scoop.

The scoop inlet is small on Phil's car......



.............. and on Hooley's car, and ...........................



........ the scoop body is big and looks like a lot out there in the air, but it allows us to taper to a larger plenum which should slow the air and help pressure wise some, but more importantly this big scoop is more aero than the flat windshield behind it.  In Phil's case where he is running NA there are rules as to how tall the scoop can be and that one goes almost to the limit of the rules.  If he ran blown where there is no height requirement I would have taken it to the top of the roof line like we did on Hooley's car.



If I had a bike like Joe's (picture) or yours I would at least try putting a forward properly size snout out the front of the main fairing body if I could figure out how to smoothly duct the air from there down to the turbo inlet in a progressively larger duct.  I know John (WZJUNK on here) could make one out of glass if he had a shaped mold from the inlet to the turbo.  I don't know if the bike rules would allow that or not.

c ya,

Sum