Aero mods and cooling

[Brick]

i still think [MENTION=1391]Siestarider[/MENTION] and [MENTION=636]RAAMaudio[/MENTION] need to make build threads so we can just reference all their pictures in one spot. I cant keep track of the bazillion threads they have added input on topics of interest.

 

[RAAMaudio]

I have a build thread of sorts but not many pics, most of my pics are scattered around the forum and I know I need to clean up the thread and put them there, sorry I haven not been the best at this.

 

[Siestarider]

Stealth is my automotive religion, and I practice it by minimizing performance profile. Hence no build for me. My view is Fast Fiesta should be a non sequitur for as long as possible.

I have learned a lot from the folks on this Forum, so I try to give info back when I learn something that might be useful.

 

[Wimp Lo]

We do have stealth on our side most of the time. WRC vents are not really stealth but most people don't know what WRC is. I think we can get away with it unless we have a Ken Block replica paint job.

A splitter will look racy if it is extended too far forward or has a visible air dam that looks too low. The look of an extended splitter can be mitigated a bit if you make it look like factory or an unmodified bolt on (fake aero) part.

Under trays are total stealth.

 

[RAAMaudio]

Even the TR splitter on a moderately lowered(using suspension geometry limits instead of visual limits that negatively effect handling if going very low) still rubs and causes severe angle approaches to driveways, etc...at least it adds to the look of the car but not look at my wanna be pretend racer.....

On the right color car, black mostly, painting WRC style vents body color would help make them less noticable.

My car is silver, not sure how that would turn out....

What I really need is something to cover the leading edge of the tires and look like it belongs on the car, I might just add a lip to the fender openings and paint them black, it does help quite a bit and would not look to boy racer.

 

[Siestarider]

I have switched back to undertray testing, going to try closing the space between stock air dam and pierce bar, see what that does for aero and cooling. I am confident WRC style hood vents would help, but if I can get equal cooling with concealed parts have to try that first.

Meanwhile the CMbuildz Racing brake cooling plates showed up, nice pieces, but i plumbed my vent for 3" hose so have to work out a reduction to 2", just ordered several parts hoping some combination will work well.

 

[Siestarider]

I installed a belly pan from stock air dam back 3" past Pierce 2 point brace. First surprise is how much quieter car is. With front aero so quiet, mirrors are now the noisiest aero, take them off and car would be really silent. Except for 3" downpipe and exhaust.

First glance, coast down tests indicate 4.3% more drag than without pan. Makes no sense yet. Need more data.

Manometer tests generally show engine bay pressures twice as low as air dam extension testing showed. So cooling should be enhanced, but have to track it to really tell.

Have some pics, will post after game.

 

[Wimp Lo]

I'm anxious to see the pics.

 

[Siestarider]

Belly pan cut from 1/8" ABS, rough side up.

Aluminum bars riveted on for attachment behind OEM air dam. Nylon zip ties (added another to each pair of holes) ready to zip around Pierce 2 point. Zip holes are set so that tightening them pushes pan forward into bottom lip of air dam.

View from front of installed pan.

View from side installed pan. Yes these are poor pictures accurately reflective of my poor photographic skills.

Here are some pics of the fog light vents from outside. I tried to get backlight on the first one to show 3" vent connection on rear side.
The other two are at least better than prior posts. Hard to show details when its all black materials.

Pic of IC opening, I used the same bug screen as fog light vents, shows up a little better here.

I taped off the fog vents for coast down testing and manometer testing. Right now passenger side open, driver side to Mountune lower airbox inlet hose. But next mod before track is hooking them up to CMBuildz Racing brake ducts for testing.

Weather conditions for coast down testing were 65 F and NE wind 10-15 mph. Prior testing I am comparing to was 88 F and wind SE at 10-15 mph. Same road, same tires, but I admit I forgot to check tire pressures and have not since it cooled off here, so I could be getting some lower tire pressure effects. Plus denser air.
So I am not taking coast down testing results as final, just preliminary.

Pressure tests all conducted as priors, 80 mph, test hose taped at right angle to assumed air flow direction.

Front center outside open part of grille +0.5"
Front center radiator +1.2"
Rear center radiator -0.8"
Front center IC +2.4"
Rear center IC -1.2"

Engine bay pressures generally -0.6 to -0.8" on sides and top rear areas, dropping to -0.4" with hose taped to top rear center of belly pan. Note some of the engine bay pressures I measured were wonky results, I assume due to turbulence, so unless I had reasonably steady readings I did not record them. But the recorded are about double the pressure drop measured with the 2" air dam extension previously tested.

I made no attempt to connect front fender liners to pan, so there is a 2" gap each side of pan at lower edge of front fender liners.

I cut away small triangles at the outside rear edges of pan to clear lower A arms just in case, probably cannot reach pan on road, but jacking up a side the arm might have drooped far enough to interfere.

I believe the data indicate conflicting results for pan aero, it may be adding drag. But the rest of the data suggest cooling should be enhanced. Far as I know, wringing it out on track is the only way to find out if cooling is actually improved.

The first few laps will be more about stability than cooling, I don't know how front end will feel with pan in place at higher speeds. Felt fine at 90. Everything held together in testing, but its obviously a temporary mount so I will add some structure before tracking.

 

[Chuckable]

Thanks for the pics! Have any showing the reverse side of the fog light trim? Wondering what ducts you used and what you did with the windshield washer reservoir?

 

[Wimp Lo]

That looks pretty nice. With those aluminum bars it looks strong but if it deforms at speed, that might explain a poor result (if it's not the weather).

One thing that I can't see for sure is it looks like the pan might not be exactly flush with the bottom of the air dam. If there is an indentation behind it, it might create turbulence.

I really need to buy a Triple R splitter to see the mounting and start making a combination splitter and under tray part.

 

[ogsigh]

Nice fog ducts

 

[Siestarider]

Thanks for the pics! Have any showing the reverse side of the fog light trim? Wondering what ducts you used and what you did with the windshield washer reservoir?

Here is with and without duct connections shown from inside nose.

I currently have drivers side vent going to lower Mountune airbox inlet, had to deform the hose to get it between IC hose and WW bottle. But both vents are taped shut for aero and pressure testing right now.

When I test the CMBuildz Racing duct plates, I will only put passenger side on and connect that ducting system, leave driver's side stock. Waiting for parts to reduce hose from 3" to 2" so vents will connect. Then use temp paint on outside edges rotors and below calipers near hubs and compare ducted to non-ducted.

Little bit of a problem with this test method, temp paint measures peaks, not averages. Ducting should reduce averages more than peaks, and lead to longer pad and rotor life tracking.

On a clockwise track, passenger side front brake pads should get more wear due to torque vectoring even when ESC is fully off and LSD is working, but I have no idea how much. I will log front wheel speeds and try to tease this effect out, but my first guess is the ducted cooling will have to be a lot better than stock for these test methods to show results.

If anyone has a better idea, I am open. CMBuildz should have a fair comparison test for their parts.

 

[Chuckable]

Thanks for the pics! The testing you'll do on the CMBuildz ducts, while not 100% perfect, should be very useful since it'll be a real world test rather than predictions and estimates. Variables like tires, number of left vs. right turns, and maybe even level of traffic will all influence the tests. But, I'm hoping to hear that the CMBuildz ducts really work!

 

[Siestarider]

Update:

Aired all tires to factory spec, taped the exterior edge of air dam to undertray so there is no lip exposed, logged two coast down runs each way, averaged results and was within 0.1 sec of average of 8 prior tests from Monday under near identical weather. IE within 0.2% of Monday tests.

So adding a belly pan the way I did reduces aero efficiency vs stock.

Retested a few spots in engine bay, same results. Definitely pulling more negative pressure than stock.

So this mod increased Cd by 4.3% with frontal area unchanged.

And I doubt cooling is being enhanced, if it were, more air would be flowing through heat exchangers, and engine bay should not be going to greater negative pressures.

The first thing comes to mind is to try shortening tray, maybe I over did the length and did not leave enough room for heat exchanger airflow to leave engine compartment and join faster moving air under car.

Or maybe tray just not stiff enough to get good results. It can flex a little, but its tight fore and aft. Does not rattle or hum.

At least results replicated, now the pondering...

 

[Siestarider]

Having read some wheel well aerodynamics, pondered, today cut both rear corners off belly pan and sealed wheel well liners to pan in front.

Improved coast down to better than OEM. Not quite as good as 2" air dam extension though. Pressures look better too, lower in front of radiator and higher behind it.

The two pieces removed were less than a sheet of paper total area.

 

[RAAMaudio]

I may of not done it correctly and have not tested but as advised added a duct to direct air into the bay and increase the air flow through it, if that makes any sense

I was going to add two NACA ducts but ran out of space on the passenger side so build one big one at the rear of the tray aiming up towards the DP in hopes to flow more air out of the bay while also over the hottest part of the exhaust to help keep temps under control near the firewall, brake and fuel lines etc....

I am keeping track of your progress on this and will use what you have learned and make changes accordingly, thanks!!!!

Rick

 

[Wimp Lo]

Having read some wheel well aerodynamics, pondered, today cut both rear corners off belly pan and sealed wheel well liners to pan in front.

Improved coast down to better than OEM. Not quite as good as 2" air dam extension though. Pressures look better too, lower in front of radiator and higher behind it.

The two pieces removed were less than a sheet of paper total area.

Could you take pictures of the pieces you removed?

 

[Siestarider]

Our stock radiator is 1" thick, 25.5" wide and 14.5" tall. Slightly larger but same thickness as a 1986 3.8L Ford Taurus radiator I found was used in a Masters Thesis done by Paul Reuter, a Texas Tech ME. Condenser dimensions just slightly smaller than radiator. Also tested a 1994 F150 radiator 1" thick, 30" wide and 17" tall.

This paper evaluated the combination of blockage of radiator face by narrow gap AC condenser mounted in front of radiator, of interest because our cars have this configuration. And it reports measured pressure drops across combined heat exchangers under SCFM rates of 800 to 4000. Disregarding some gas law temp and gauge pressure variables, a rough estimate air inflow to our cars assuming 1 square foot of effective grille opening at 60 mph would be 5280 feet/min x 1 sf = 5280 ACFM.

Full Taurus condenser/radiator combo produces a pressure drop of about 0.6" H2O at 3000 SCFM. But pressure drop curve is not linear, it increases faster than linear with SCFM, so extrapolating curves suggests pressure drop at 7000 ACFM (80 mph) should be around 1.5-1.8"" H20, pretty close to what I am measuring under stock configuration.

Clues to my problem with original undertray were increase in pressure in front of condenser/radiator and decrease in pressure behind it. Hence I was not optimizing air flow through heat exchangers, apparently due to outlet restrictions at wheel wells. Small relief there made a big difference. So now with Reuter data I have a baseline of optimum pressure drop to shoot for.

Found some old airplane radiator design papers that indicate intake cowl area should be 30-50% of radiator area, and expanding in a horn shape to heat exchanger. But most important performance parameters are shape of inlet diffuser and heat outlet diffuser and location. Looks like next step is measuring some of the basics to see how aero optimization might work better for more cooling with less drag.

 

[RAAMaudio]

This is still one of my favorite threads of all time, keep it coming