NACA ducts vs Inlet tube

[Ian Northeast]

Hello experts,

I apologise if this has already been discussed somewhere in this huge mountain of information but I couldn't find it.

Due to space configuration I have mounted my single turbo just above the passenger footwell in my saloon car. As it is, it sits a long way back from the front of the car and quite high up in the engine bay.
Obviously this allows me a nice short exhaust from the turbo (about 9" long) but the inlet needs to be sticking out of the top and side of the bonnet.

I may have room for a shallow NACA duct provided I can find one with a 4" tube or would I benefit from fitting some sort of inlet tube?

Someone has done the maths on this and knows either from practical experience or from a paper exercise which is the right way to go.

Your recommendations please

Ian

[WOODY@DDLLC]

http://www.landracing.com/forum/index.php?topic=17369.0

[tauruck]

I have a mold for a genuine NACA duct that I'm sure has a 4" tube. I'll check and get back to you.
The fake aftermarket junk looks similar but doesn't do the job.

[MAYOMAN]

Lots of data and design details at the forum below. Merry Christmas!

Landracing Forum ?
Tech Information ?
Aerodynamics ?
NACA vents vs. Hood Scoop question

[Old Scrambler]

Why not the FRONT of the Bonnet?  Steady source of cool, clean air.......and BTW......The initial few inches of the intake duct may perform better with flat sides versus a round or oval shape resulting in an overall smaller diameter 'tube' of no less than the size of the blower-intake.

[Ian Northeast]

Thanks Woody, as usual an awful lot of information and a lot to digest.
Tauruck I would be very interested in that, although there may be a small issue with depth. If you have dimensions that would be fantastic.
Merry christmas to you too Mayoman, again loads of information.
Old Scrambler that was my original plan but the turbo is a long way back from the front of the car and there isn't enough room below the bonnet to run a tube of the right size.

Ian

[Crackerman]

The base of the windshield typically provides a massive positive pressure change. Any air inlet there can provide positive pressure to the turbo inlet, without much additional drag from a dedicated inlet scoop, granted the naca duct should perform just fine in most instances.

[Sumner]

Hello experts,

I apologise if this has already been discussed somewhere in this huge mountain of information but I couldn't find it.

Due to space configuration I have mounted my single turbo just above the passenger footwell in my saloon car. As it is, it sits a long way back from the front of the car and quite high up in the engine bay.
Obviously this allows me a nice short exhaust from the turbo (about 9" long) but the inlet needs to be sticking out of the top and side of the bonnet.

I may have room for a shallow NACA duct provided I can find one with a 4" tube or would I benefit from fitting some sort of inlet tube?

Someone has done the maths on this and knows either from practical experience or from a paper exercise which is the right way to go.

Your recommendations please

Ian

What class are you running in?  Might make a difference in where you can put the inlet,

Sumner

[Ian Northeast]

Hi Sumner,

The class thing is a very good question.

In this particular case I am likely to decide not to run in a class. I have been running up until now in the classic coupe class, however the modifications I have now made put me squarely inbetween classes.

I am purely interested in getting my car over 200 mph, I am a long way off a record and could never afford to seriously challenge for it with this car. The intention for my part, is to build and race the fastest Jensen and then put the car to bed.

Obviously I would like to survive the process so I have introduced some relatively serious mods, some of which are at odds with the class rules.

We have now built a new 'sealed' front end and are planning on increasing the volume of water to avoid the need for a radiator. We also have a flat floor with rear diffuser and a larger rear wing than our last attempt. We also going to put the intercooler in an ice bath before each run. Rather than adding large amounts of weight at the rear we are hoping that the increased down force will aid the traction issues at speed.

There is a lot of very useful information on your website which we have used primarily to calculate the bhp we will need and we all seem to be working off the same page. Thank you for making the information available.

Ian