Managing post-radiator air flow

[carnut169]

After changing my cooling system around a bit I am looking at ways to further increase the efficiency of the system. On the Stohr's they solved the overheating my cutting a series of vents behind the radiators (look like shark gills). In a similiar location, some 94/95 cars have a removeable panel.

Clearly, the panels can help evacuate heat.

I'm wondering if it's because air flows out of the pods there or because air flows in and creates a vacum pulling the hot air out of the pods with it.

Would it be better to just have an opening the the area indicated in the pis or a small naca duct?

[RussMcB]

Good topic. I'm planning to do something in this area, too.

I always thought (perhaps incorrectly) that the openings were to allow air to escape, not to bring it in to produce a vacuum. My simple mind thinks it all boils down to finding (or creating) a lower pressure area to vent to.

I'm thinking of adding little Gurney flaps ahead of my openings to hopefully encourage a lower pressure area outside the opening. I'm wondering if louvers might be another way to accomplish the same thing.

I haven't noticed the shark gill openings on Stohrs.

[Rick Ross]

I realize that I am stating the obvious, but increased cooling airflow has a price.....increased drag. Many reciprocating aircraft engines address this problem with pilot-adjustable "cowl flaps". These are moveable panels which alter the area of the cooling air exit flow. During high power, low speed conditions (such as takeoff), the flaps are fully open to allow maximum engine cooling. Then at cruise and during the descent at low power the flaps are closed, providing less drag and maintaining proper engine temps. BTW, there is a huge volume of research out there on cooling airflow, NACA ducts, etc. It's been over 20 years since I studied this stuff, but I seem to recall that the location of an NACA duct is critical, so make sure you put it in the right place.

Do the FB rules allow for cockpit adjustable cooling "flaps"? Or would this be considered a moveable aero device, even though they are not downforce producing? If adjustable flaps were allowed it would give you some control over oil/water temps while on the track. Even if cockpit adjustment was not allowed, you may want to consider a way to quickly and easily vary your coolant flow inlet and/or exit areas while at the track. You could then fine tune your cooling capabilities for the specific track and weather conditions.

I would love to have cockpit control of the cooling airflow on my DB4. At ambient temps below 70 deg my car over-cools the water and oil, requiring me to block off a significant portion of the air intakes. It would be nice to control this from the cockpit and keep the temps right where I wanted them.

[carnut169]

Here are those Stohr vents: (under rear wheel flap). Rick, I hear you about the drag, but a rod through the front of the block also slows you down a bit...

[Rick Ross]

Hmmm......can't really argue with that! A rod thru the front of the block would definitely increase drag.....I recommend only throwing rods thru the rear of the block if you wish to keep drag at a minimum.

[Brands]

Getting air out is important, and I remember from my F1 days how certain solutions would impact both cooling and aero performance. We always found that exiting the air out of the side pod side was bad for aero - the more we opened the car up the more downforce we lost, as well an increase in drag. Exiting the air out the back of the car was a good solution and helped keep exhausts cool (as well as everthing else downstream). As we found more aero performance from 'shrink wrapping' the rear bodywork, so cooling suffered. The snorkel or chimney and louvers where a reasonably efficient way of exiting hot air. We also had different shrounds covering the top exit exhausts which could be changed to effect cooling. One year we had a slight imbalance between oil and water so the right hand side (oil) shroud was bigger than the water. Not sure that's any help for an F1000 car, but if I did new side pods I'd look at top exit cooling.

*The NACA duct should only be used for air-intake* They are a specific type of duct that work in areas not exposed to direct air flow so work well on the side of cars. Without getting into the dull stuff they work by opening up the cross sectional flow area which decreases the static pressure thus 'drawing in the air. Vortices are shed from the top of the duct walls which also help pull air through the duct. Yawn. Oh! See below as well!

[Tom Sprecher]

NACA ducts work best when located toward the front of the car or surface where the boundary layer is thinnest and don't work as well as a scoop at higher velocities.

[carnut169]

Getting air out is important, and I remember from my F1 days how certain solutions would impact both cooling and aero performance. We always found that exiting the air out of the side pod side was bad for aero - the more we opened the car up the more downforce we lost, as well an increase in drag. Exiting the air out the back of the car was a good solution and helped keep exhausts cool (as well as everthing else downstream). As we found more aero performance from 'shrink wrapping' the rear bodywork, so cooling suffered. The snorkel or chimney and louvers where a reasonably efficient way of exiting hot air. We also had different shrounds covering the top exit exhausts which could be changed to effect cooling. One year we had a slight imbalance between oil and water so the right hand side (oil) shroud was bigger than the water. Not sure that's any help for an F1000 car, but if I did new side pods I'd look at top exit cooling.

*The NACA duct should only be used for air-intake* They are a specific type of duct that work in areas not exposed to direct air flow so work well on the side of cars. Without getting into the dull stuff they work by opening up the cross sectional flow area which decreases the static pressure thus 'drawing in the air. Vortices are shed from the top of the duct walls which also help pull air through the duct. Yawn. Oh! See below as well!

Would a series of gills help? Building a chimney is a little out of my league. Any other suggestions?

[Brands]

You could certainly try some louvers on the side pod top. You might look at an exit duct as well. I'd worry about cooling over aero performance (as I'm sure you are) for the moment. These cars don't generate much downforce and when I say that side exits where bad in F1 that needs to be put in context. With roughly 3000lbs of tdf (at a given speed) we could loose 100lbs + in cooling options, which might not sound like much, but when a 5 lbs gain will make it to production it is a big deal. The IRL cars I worked on had side exits with a rad exit duct - much like the reverse of the inlet duct. We had various blanking panels that we would tune the cooling/aero with. I'll have a think and let you know!

[Purple Frog]

Since I also have an Averill front wing, and the Reynard is overheating... not that there is any relationship.

Could it be that the front wing is diverting air away from the inlet?

Take a few laps without the front wing to test?

Maybe put a wicker bill around the outside of the rear of the sidepod?

Maybe the scoop behind your head (that isn't yet sealed to the intake) is producing some kind of weird high pressure in the engine compartment, pushing air into the rear of the sidepod? You may need a panel against the chassis separating the sidepod from the engine compartment.

Maybe that "tuck-in" at the rear of the sidepod is too restrictive?

I'm thinking a hole in the top of the sidepod, below that pretty SCCA decal would be the best solution. Maybe with a small backwards facing chimney. Sort of like hold vents in a speedboat.

Go look at Coop's car...

Maybe the rads just aren't big enough for a mc motor?

[Mike Devins]

Coop and I discussed several cooling improvements which he and Anna incorporated.

First was a 3/4 inch wicker on the exit of the side pod which resulted in a slight improvement.

Second was to increase the size of the radius at the inlet making sure that the new leading edge did not make the inlet smaller and also to close out the area between the sidepod and the exhaust all of the way from the rollhoop to the end of the side pod. During the race he saw 200 deg water temps, oil temps were still high.

Next step will be to put in a bigger oil cooler.

[carnut169]

I'll tell you the changes I've made thus far and post some pics later today.

I purchased two new coolers- a C&R radiator and a Setrab oil cooler. In the right side pod I had a tube & fin type oil cooler and one of my aluminum tube type radiators. I've swapped over to the C&R radiator and a small oil cooler installed behind the radiator. An 8" electric fan is installed between the two pulling air through the radiator and pushing it throough the oil cooler.
In the left pod I'll mount the Setrab in front of the other radiator. The Setrab is the more efficient style (all coolers are now this style except the left side radiator). Its about the same size as the radiator- 8x 16", 50 row. I'm thinking that as the oil leaves the engine it will enter the smaller oil cooler on the right side which should lower temps by maybe 20-25'. It will pass over to the left side where the majority of the cooling will take place. I've got a sensor at the exit to verify this.

The water will work the same way except the C&R should do the majority of the cooling and the 2nd radiator cooling just a bit more.

[Mark H]

Hey Man,
Car looks great!
Since your talking about side pod air outlet, what Mike said. The RF95(interchangable with the RF96) has a bigger, untapered outlet that I would think is still the best place to get rid of air. As Brands said the side and the top have greater aero penalties?

[Matt Conrad]

Sean,

I think the rad and cooler now sound up to the task, but I agree with a few other above in that I also think the air exit may be slightly restricted (right where the word "here" is on your above picture). A chimney or louvers might make a big difference.

Here's an image of the new Lola F3000 chassis that the guys out at the Russell School are now using.



I don't think you need to go this crazy with the lovers, as these are fairly exagerated, but I think you'll see what people are talking about. FYI...our new F1K.09 has a similar (but more limited) rad exit treatment....I'll see if I have a shot of the plug or an image from the computer later.

Matt Conrad
Phoenix Race Works, LLC

[Charles Warner]

I'm thinking of adding little Gurney flaps ahead of my openings to hopefully encourage a lower pressure area outside the opening.

Russ,

Standard affair on RT-4/5. Little winglets that would snap into the leading edge of the radiator duct exit. Had various lengths. Work great. Cheapest thing to try.

[Matt Conrad]

I promised a shot of the new F1K.09 car's post radiator air flow. You'll note both chimneys at the outer top of the sidepod, as well as the louvers on top of the rear of the sidepod.



Matt Conrad
Phoenix Race Works, LLC