Zulu's Build Thread (Honda CR-Z)

[CigaR007]

Ok. So here is a quick tuft test to validate the airflow. The exhaust flow direction seems alright. Any thoughts ?

https://www.youtube.com/watch?v=rFYD...ature=youtu.be

Originally Posted by JulianEdgar

eg I'd guess that adding a vertical forward projection to the outside edge of the opening would increase the pressure at the mouth of the duct.

That's a good idea. I will try it out.

Thanks !

[JulianEdgar]

Originally Posted by CigaR007

Ok. So here is a quick tuft test to validate the airflow. The exhaust flow direction seems alright. Any thoughts ?

That's a good idea. I will try it out.

Thanks !

You can't do valid tuft tests with the car stopped. The pressure differences and so flow directions are not replicated by doing so. Buy a $50 Magnehelic gauge and measure pressures- you'll use it forever.

[CigaR007]

The static demonstration was just to visualize the exit flow in terms of the angle, not to validate actual dynamic flow behaviour.

[JulianEdgar]

Originally Posted by CigaR007

The static demonstration was just to visualize the exit flow in terms of the angle, not to validate actual dynamic flow behaviour.

It won't even do that, as exit airflow angle will be determined by airflow activity within the wheel arch caused by the spinning wheel and moving car.

[CigaR007]

Originally Posted by JulianEdgar

It won't even do that, as exit airflow angle will be determined by airflow activity within the wheel arch caused by the spinning wheel and moving car.

I am fully aware that the visualization above is not the actual behaviour when the vehicle is in motion.

The physical orientation of the exhaust (slightly outwards in this case) is something that will probably require some tweaking as it does offset the actual airflow activity.

Anyhow, I am planning another tuft testing session with your proposed idea to try and increase the pressure at the inlet.

Regards

[JulianEdgar]

Originally Posted by CigaR007

I am fully aware that the visualization above is not the actual behaviour when the vehicle is in motion.

The physical orientation of the exhaust (slightly outwards in this case) is something that will probably require some tweaking as it does offset the actual airflow activity.

Anyhow, I am planning another tuft testing session with your proposed idea to try and increase the pressure at the inlet.

Regards

It's great that you are doing stuff, but aiming a hair dryer at tufts on a stationary car tells you literally nothing at all, and using tufts to determine duct flow on a moving car only tells you if there is any airflow through the duct - or not.

I think that there is probably little flow through your duct, and that could have been determined (basically before you even started doing all the work) by measuring the pressure difference between the surface of the bumper (where you are trying to pick up air) and the front inner edge of the wheel arch (where you are trying to expel air).

My viewing of factory car air curtain ducts (viewing only - I haven't measured the pressures) indicates to me that they want a lot of air flowing, which means a big pressure difference.

By measuring pressures you would be able to see exactly what is happening, and what modifications to the intake are achieving (or not achieving).

[AeroMcAeroFace]

Originally Posted by JulianEdgar

Tuft testing will tell you airflow direction, but pressure testing will tell you airflow amount. Pressure testing will also tell you the results of small changes, eg I'd guess that adding a vertical forward projection to the outside edge of the opening would increase the pressure at the mouth of the duct.

adding a vertical forward projection to the outside edge of the opening This is a good idea, almost every air curtain I have seen has these forward projections.




And unfortunately according to wikipedia "This type of flush inlet generally cannot achieve the larger ram pressures and flow volumes of an external design" Ram pressure is what you want in this case, so maybe a NACA duct isn't the ideal inlet.

increasing the inlet area, and trying to get as much airflow through the duct as possible. Inlet area greater than outlet area is generally of benefit too.

"It's great that you are doing stuff, but aiming a hair dryer at tufts on a stationary car tells you literally nothing at all," I disagree, but only slightly, the tuft direction will tell you where the air is aimed at, which is important in curtain design, if it is aimed wrong then it doesn't work regardless of the inlet. But I do agree that it is in no way representative of what happens when the car is driving.

[Xist]

How much larger can the passage be?

[CigaR007]

I have been working on a box cavity extension for the CR-Z.

I am happy with the overall result. It is made of cardboard, hot glue, tape and plastic bags to protect the cardboard.

This is a proof of concept and will undergo some tweaks before I attempt to fibreglass and colour match it. Still thinking about integrating some sort of rear diffuser.

Let me know what you think. I am open to suggestions.

https://www.youtube.com/watch?v=LMw-Ia5dQFY

Cheers !

[Ecky]

Very cool! I don't see people doing things like this nearly enough anymore. Looking forward to any data you record.