Driving with no center console: reduced buffeting?

[TurboWood]

For a few reasons I ended up driving my car without the center console in place (2013 caterham CSR). Ignoring the obvious aesthetic and comfort negatives, what became very obvious was the huge amount of heat being pumped out. At the time this was mostly annoying, but thinking back on the experience I realized that I didn’t recall so much buffeting. I drove the car with and without doors. Without doors I probably only got up around 50-60 which isn’t that high, but plenty high enough to notice buffeting.

 

This got me thinking about the aerodynamics when air is allowed to vent out the center of the passenger compartment. I wonder if this could be a really good way to get high pressure air from the bottom of the car out and simultaneously add some pressure to the passenger compartment to reduce buffeting. 
 

So, before running down this rabbit hole I was wondering if anyone else had done this?

 

As a side note, I do see grease from the universal joints on the drive shaft all around the tunnel. So, I wouldn’t suggest anyone try this on a fresh build as there is likely to be some grease being flung around.

 

Cheers,

Daniel

[MV8]

A low profile scoop that snaps on to the top of the windscreen to direct air down behind the windscreen would have a similar effect without the heating. An acrylic or polycarb panel between the head rests would help too. I expect an S2 or S1 would have much less buffeting due to the narrower rear wings.

[Dave W]

"simultaneously add some pressure to the passenger compartment"  

 

I have an acrylic rear window that spans the roll bar. When completely closed, it increases the pressure in the cabin. The window has a center sliding section and opening up the center section 3 or 4" makes a noticeable reduction in buffeting.  The low pressure area behind the window does a good job of drawing the air out of the cabin area, which cuts down on the main cause of the pulsing. You will probably need a method to tune the air flow for best results.

[Croc]

@TurboWood  I tried what you did once, before and after the underfairing removal.  My CSR came with a smooth ali sheet fairing on the underside.  Only exposed underside was at the diff.  It went forward as far as the front end of the gear box.  Downside in that configuration was it pumped heat under air pressure into the center tunnel.   One of my experiments was venting heat from the center tunnel and I noticed the cockpit air pressure change exactly like you did. 

 

However, the heat was a bad thing so I discarded that approach and tried a mesh screen around the roll bar.  It was a bigger coverage variation of @Dave W idea.  A commercial product offered is here:

The Draught Reducer (softbitsshop.co.uk)

 

With my half hood on in summer, mesh screen across the roll bar at the back, my cockpit became a very pleasant place to be.  

[TurboWood]

Thanks for the feedback guys. A half good and some sort of adjustable block on the roll bar sounds like a winner.

 

Venting the center near the back will remain on my mind. Given the amount of heat being pumped through I also think it’s a good idea to get it out.

 

Daniel

[JohnCh]

On 12/28/2022 at 3:27 AM, MV8 said:

A low profile scoop that snaps on to the top of the windscreen to direct air down behind the windscreen would have a similar effect without the heating.

 

This is something I've been kicking around and plan to do some experimentation when the car is done.  I remember reading somewhere many years ago that drilling a large hole (2-3") in the lower center portion of the windscreen dramatically reduces buffeting.  From my own experience, very large wind deflectors make a huge difference, but at the expense of even more drag.  Given what they can do in racing with aerodynamics by redirecting and speeding up/slowing down air to create high- and low-pressure zones in very specific spots, I suspect there is an opportunity for air management to make things more acceptable.  i.e. use walls of air to change what's occurring rather than redirection by big pieces of Lexan.  At some point, I'd love to tape strings of yarn all over the car, then attach a 360 deg camera to the roll bar and get a good look at what's happening.

 

-John

[panamericano]

You might want to check one of the scoops available for Miatas.  Low profile. but might work?  It would be good to handle one to see if it would clamp to the skinny 7 windshield frame.

[JohnCh]

I've never heard of those. I'll need to research them.  If they work, it shouldn't be too hard to print up something that would mount to the windscreen frame.

 

Thanks,

John

[MV8]

Polycarb, acrylic, abs, etc can be formed in a normal electric oven over a wood stud (no pressure treatment) buck at around 200f (depending on the material) or less until it droops into shape. The height of the scoop should be no more than an inch considering the force it will apply to the windscreen frame at speed. Pickup two snaps. The rear edge should follow the frame top and back to aid the snaps to hold it in place. If the snaps are equidistant across the top, the scoop could be adjusted from side to side. Thin and flat, it would store easily.

[TurboWood]

I really want to try adding a vent to the  center console. I have two center consoles so I can run a bit of an experiment. I’ve done a tone of internet searches for vents, but haven’t found the right one. Back in the day I had a ‘94 Supra with nice round vents. I see Mercedes uses similar vents today. I’ve also found many RV cheap solutions, but nothing seems right. Can anyone give some ideas?

 

Thanks,

Daniel

[TurboWood]

Well, I did a thing. I’ll let everyone know how it goes.

[MV8]

Is that a cup holder with the bottom cut out to vent to a ball valve? Could be effective. I wonder if anyone has spaced the rear fenders away from the body an inch or vented front to back inboard of the tire to reduce the drag and high pressure that contributes to the buffeting.

[11Budlite]

5 hours ago, MV8 said:

Is that a cup holder with the bottom cut out to vent to a ball valve? Could be effective. I wonder if anyone has spaced the rear fenders away from the body an inch or vented front to back inboard of the tire to reduce the drag and high pressure that contributes to the buffeting.

 

When Gary May and Len Unwin were developing their Freestyle Caterham, they were using the SV axle with the S3 body/chassis to widen the rear track. I don't have a link to the LowFlying article but I do have a hard copy of it (2/16 edition).  This is a direct copy of a portion of the article discussing their result, and partially addresses your question: 

 

"Finding rear wings wide enough to bridge the gap between the S3's rear body and the extra length of the SV axle was more of a dilemma meanwhile, and Gary's first solution here was to create a mesh spacer to sit between the standard rear wing and the wheel arch.  'I liked it aerodynamically because it let the air through, but Len hated it - he said 'that's SO ugly'. So we changed it....and went instead for a new, wide wing."  

 

There were only 8 official Freestyle cars built, with number 7 residing in California when the article was written. I'm sure there were other standard Caterhams that were converted with parts supplied by Freestyle.

[TurboWood]

12 hours ago, MV8 said:

Is that a cup holder with the bottom cut out to vent to a ball valve? Could be effective. I wonder if anyone has spaced the rear fenders away from the body an inch or vented front to back inboard of the tire to reduce the drag and high pressure that contributes to the buffeting.

It’s a ball valve meant for light aircraft. I spent way more time than I should have looking at vents before settling for this one. It has a nice feel, opens and closes with a turn.

 

https://www.ebay.com/itm/193462649929?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=a5TtGP8MQn6&sssrc=2349624&ssuid=QzVVyFeGRe2&var=&widget_ver=artemis&media=COPY

 

Daniel

[JohnCh]

@TurboWood have you had a chance to test this yet?  

 

Thanks,

John

[TurboWood]

I’ve driven the car around a few times, but only short trips with the focus being on improving my tune. I haven’t had a chance to make a clean comparison of it open and closed (ideally with a passenger playing with it while I drive). 
 

That said, one of the trips I was driving around 60-65 with the doors off and wasn’t getting meaningful buffeting (vent open). 
 

I’ll try to convince my wife she needs to go for a ride ;).

 

Daniel

[TurboWood]

Ok, I’ve driven the car around with the vent a fair amount now. It’s definitely not as big of a benefit as no center console, but I do think there is some improvement. That said, I probably wouldn’t suggest other mimic this setup. A larger vent is really needed to make a worthwhile improvement.

 

Daniel