Aero mods and cooling

[RAAMaudio]

Dumbbass I sold the TC to lost the rear wing the first week, cutup the cage, traded it off, new owner bringing it back to live, it only had 8k miles on it after 8 years of owning it.

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Flat bottom, etc....

I would have done it by now if not for having an 8x14ft garage in the toyhauler and 95% of my tools in storage

 

[Levi1.0]

Sad. That was a good looking tc too.

I hear ya... I have an apartment carport to deal with. Makes modding and working on cars an unpleasant and time consuming experience.

 

[RAAMaudio]

That car was the one I should not of sold, foam filled chassis, CF/Kevlar roof, caged with removable bars for street use and NASA legal, Racetech seats and 6 points, full interior minus rear seat but upholstered and carpeted, sound deadened, audiophile competition winning sound system with 15" sub that hit 138.4db on music, batter sunk into rear floor, amps as well, custom rear sway bar, coilvers, bushings, engine and trans mounts as well as LSD, 275lbs lighter than stock, close to what my lightened FiST weighs. 265 wide race tires I drove on the streets on occasion, custom BBKs.......on and on and on.....

At first I just wanted to see what I could get with the TRD SC, 11 hours on the dyno, day two of a Redline TT event blew the engine, cost more for the dyno time than a replacement engine, started a big turbo build, huge hours later, nearly done, fell in love, traveling to see my wonderful lady, lost interest, car sat a few years, finally just sold it.

Interesting is that a reliable daily driver the 2.4 is only good for 350WHP, have to build the engine to make more and expect it to last which includes 6 bolt crank caps, then good for huge WHP but a very costly build to say the least.

I was offered a partial sponsor build, rods, crank caps, cams, ported and polish head, etc....$7k, damn good price, could make far more HP than I could use, should of done it as spend a few hundred grand building other projects instead, now retired and no money in the bank to speak of....had fun though

This is the first and only turbo manifold I designed and built, hybrid twin scroll, firing order sequence for twin scroll, equal length within mm, single WG to save weight and space restrictions, very well approved by one of the top turbo experts in the world....50+hours into it.

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Oops, thread is aero mods and cooling.......I had to move the radiator, AC, IC and oil cooler to fit this manifold and GT3076R turbo and build all new ducting, notch the bumper, etc.....

 

[Siestarider]

I would mount that header over the fireplace if it were mine. But my tribal totem already has that spot.

That is tonight, cold down here, last of the evening fire warming the house. Had to download today's aero mod pic anyway.

Trimmed rear corners off undertray to match RS photos, poked around lower engine bay looking for ways to improve air flow, realized my Mountune lower intake hose was a prominent vertical obstruction through lower driver's side so I took it off and taped up the bottom hole in the intake box. Had fog light intake vent closed for aerotesting anyway. Maybe tomorrow it will not be too windy to test the car.

 

[Wimp Lo]

Not really related to cooling but I think a stock or closed bottom air box with a Velossatek Big Mouth is more likely to generate positive intake pressure than the Mountune setup.

With a DHM Race intercooler, crash bar and opened up grill, I don't think the grill opening it "obstructs" would do anything negative for cooling. The prospect of more air at speed is making me try it.

 

[Siestarider]

I too see the big mouth as more likely to pull cool air, plan to replace Mountune air box with Velossa to stock air box so I can loose the Mountune lower intake hose for good and route both fog vents to brakes.

more air pressure at front of heat exchangers should help as long as pressure behind them also goes up some but not too much, indicating more cfm and lower pressure somewhere downstream is working for you.

 

[Wimp Lo]

The delta between front and rear is what determines flow through a fixed obstruction.

High pressure behind the radiator means air has a harder time getting out of the engine bay and if you jam so much air through the radiator that your pressure under the car rises, you are going to have less ground effect and higher drag. That is why racers tape radiators.

 

[GAbOS]

I have a Mishimoto intake elbow and Big Mouth in hand but not installed.

Installed is a stock airbox (w/drop in) in the high Sierra at 91 on a basic Tune+ etune.

How should I test?

 

[Wimp Lo]

That is a good question for Adam.

What I would try is data logging IATs, boost and mass air flow. If there is less vacuum or more positive pressure in the intake, the turbo will spool quicker and possibly produce higher boost levels. If MAF is increased that means more air and fuel burned, that should be power. Low IATs are generally good too.

 

[TrickSTer]

re: exhaust emptying into diffuser - Formula 1 speak: "blown diffuser" pioneered by Red Bull - highly effective - banned after 1 year. For 2017 rule changes they are considering changing from 1 regulation size exhaust pipe outlet in a specific location to allowing same exhaust pipe in same location, plus twin bypass exhaust outlets, possibly outleting to diffuser.

 

[RAAMaudio]

Though somewhat related F1's are basically ground based aircraft, under full throttle the majority of the time with huge heat generated, braking zones very short, the diffuser exhaust outlet is likely to have more benefits than an actual car but still a likely small percentage of the overall downforce. F1 is to the point tiny things are what they gain speed with. I discussed this with a race car engineer with extensive aero experience.

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One issue with the Big Mouth is blocking airflow to the "radiator", ditch the crash bar beam or make holes in it and whatever else you can do to increase direct airflow to the coolers.

That is why I have a true velocity stack offset out of the direct path but since a high pressure area it will stiff have a bit of ram air effect and allow plenty of smooth flowing air into the piping.

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The manifold, GT3076R turbo, DP, exhaust pipe, Emanage Ultimate, etc....in the garage in the RV so I will finally sell it, the manifold, turbo and DP were on the shop wall for years, my only full turbo build was hard to get rid of. I built one before but it was a rebuilt log manifold, the rest my son and I built and it was schedule for a photo shoot and magazine cover but sold it to help a "friend" that later burned me, severely

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Back to aero and cooling, the oil cooler I picked is a Setrab which is a top quality brand, dual pass with inlet and outlet on same side so not in the air flow to the other coolers, mounts as well are out of the flow. It is offset and in front of some of the radiator support which I opened up there to allow out more air instead of forcing it through a narrow area and into the the flow out the rest of the cooler and through the radiator.

Even though the DHM crash bar is far better than the stock bumper for air flow it is round which is not very good a flowing air over so I was looking for a wing shaped bar or something similar I could form a light weight cover to go over the exposed area that shows in the grill.

As mentioned in several posts, not sure if this one, there is quite a bit more flow out the rear of the IC if you drill holes in the grid pattern of the lower radiator support. I went even further and cut it out and made an aluminum bottom so I could lower the radiator 2" and it has barely any surface area behind the IC. Once I redo the ducting for all the coolers there would be little more I could do other than an idea of nicely patterned holes in the bumper cover between the grills. I am holding off until I see the results on a hot track day.

I am paying much attention to all the info and ideas here, I will have to do some serious instrument testing most likely as well)

 

[Siestarider]

What I am finding with manometer testing are pressure gradients. Where you measure is important. First, have to measure at a surface perpendicular to air flow, otherwise turbulence leads to wonky readings.

Second, measuring pressure drops across heat exchangers can inform, but you need to test the full air path to understand it.

I found when testing the undertray with full width all the way back to front axles, I had lower pressure right behind radiator and higher in front of radiator. So, theory says more air flow, right?

Wrong. Coast down test at same time indicated overall aero was decreased. Which meant in the bigger pictuire I was not getting more air through condenser/radiator (than stock), I was getting less. More manometer tests within engine bay showed greater pressure drops moving back and down. I concluded the full undertray was reducing flow through heat exchangers in nose, and pulling lower pressures further back in engine bay than stock, hence I measured more drag, not less.

We know from hard testing of condenser/radiator combo in controlled environment (P B Reuter) that flow through them with high air pressure applied to front and gauge at rear, 3000 SCFM flow will result in 0.6" of pressure drop across combo, measured at front and rear faces. We also know that pressure drop increases faster than linear increase in air flow because he published the curves.

So, assuming maximum clean air flow through heat exchangers (HE) and extrapolating (see earlier post in this thread) we can estimate how much pressure drop should be present at "full" flow capacity at higher speeds, ie higher cfm. Now that I know I am looking for about 1.5" pressure drop at 80 mph, anything more than that and I have too much drag. Cannot expect less drop that that, that is all the system will flow.

I realize that optimizing all this for 80 mph is arbitrary, and is based on my personal objective of attaining maximum cooling and maximum aero efficiency with an undertray at an average lap speed I have not attained (yet).

So test objectives are to get as close as possible to optimum pressure drop across heat exchangers with minimum drag, which means maximum coast down time for this particular test approach.

Cutting off the back corners of undertray just a little more yesterday may have little effect, but until tested don't know.

Also, assuming HE's air flow must divide toward both wheel wells to bypass engine obstruction, we can see drivers side and passenger side have very different diffuser sections behind radiator and IC. My test undertray is still symmetrical, but the air ducts above are not. Hate to add another variable, but its there.

 

[Wimp Lo]

Hang on a second, you say undertray gave you increased differential across radiator and less coast down distance and you get reduced air flow through the radiator?

Those first two observed results do not suggest the third necessarily.

Increased cooling will increase drag. The trick is to increase cooling just enough and then look for drag reduction everywhere else.

 

[Siestarider]

Well, when you put it that way, sounds wrong to me too. This would all be a lot easier to show in four dimensions, at least 3.

Lets start with 2" air dam extension. Compared to stock, engine bay pressures slightly lower, no measurable change in exterior nose pressures, slight increase in pressure drop across heat exchangers, improved aero over stock.

Removed air dam extension and added full width Undertray with sealed wheel well openings at front, measurably higher pressures outside nose, measurably lower inside nose, measurably lower pressures everywhere else in engine bay except on underside of hood, generally lower further back and further down. decreased coast down time vs stock.

So my eventual take was that air flow through heat exchangers was not adequate to supply the low pressure areas behind them, resulting in higher pressures measured at grill opening. Does not mean flow was reduced, I believe Wimp is correct, more air had to flow through heat exchangers based on pressure differential, just not enough to make up for the undertray sealed engine bay.

Then when I first cut corners off rear end of tray, aero improved significantly, pressure drop across HE's was reduced, exterior pressures reduced.

 

[Dustys318]

I just read through all your testing and I came to same conclusion about using the WRC style/location vents. I did the same string taped to hood and video'd it but for pressure testing I used a magnehelic gauge. I bought some vents but haven't installed them yet (winter lingers) but what I did to "test" the theory was to raise the rear of the hood but sealed the entire rear hood area with foam insulation hose. It forced under hood hot air to back corners, about as close to where the WRC vents would be mounted. It was my crude test but it validated my concern of venting the high heat under hood temps... I posted my testing using the magnehelic gauge somewhere in this forum last summer (?)... but I'm glad things are getting tested and discussed...

 

[Siestarider]

Just analyzed today's measurements. Short version, cutting off more of the rear corners of undertray moved the aero efficiency backward. Slight but measurable and consistent decrease in coast down time. Slight but consistently less pressure drop across HE's. Better pull all the cut off pieces out of trash in case an asymmetric approach is the way to go.

Dusty318 has pioneered lots of stuff, if anyone knows where to find his data maybe they can be linked with this. I am using a digital manometer rather than a Dwyer magnehelic (analog) but there should be no difference in pattern of results.

 

[Siestarider]

Sudden insight! Duh.

Big front came through here Saturday, testing aero on Sunday ambient was 60 F and Barometric pressure 30.15. Just checked air density vs other recent data, yesterday air was 7% more dense than typical conditions around here. Air density is a linear factor in drag equations, so it alone could account for the decrease in coast down time I recorded and then some.

Good thing to record pressure, temp (forgot to record relative humidity, but its a very small percentage of overall air density). Anyway, I need to go back and correct data to reflect air density, may find aero was better with a little more undertray clipped off, not worse

As an aside, I logged a couple 3rd gear runs too, uncorrected VDyno showed 210 hp peak. Corrected for temp and pressure, showed 199 hp.

Compared with other recent SAE corrected logs, closing the lower Mountune air inlet and relying solely on stock intake made no difference in hp.

Hope Velossa big mouth shows something.

 

[McRib 1s Back]

This is a fantastic thread, thank you. I'm new here and just catching up...

For my project car I decided to remove the AC heat exchanger (and the AC with the help of a new FRPP idler pulley and belt -- FRPP has the wrong size belt, probably made for the older Spec B car). I have the Gates part # for anyone else that wants to remove the AC.

I also removed the "crash bar" that has the ABS sensors on it, and apparently unique to the USDM! This really allows a nice clean path to the radiator.

Wide-open radiator with guides:
http://photos.motoiq.com/MotoIQ/Project-Cars/Project-Ford-Fiesta-ST/i-st23NxH/0/X3/IMG_2460-X3.jpg

I'm running two bottles of Water Wetter and water. I've only had the car out on the track one day, and it has been cool. For reference with a stock setup, it ran quite hot with an ambient of 107 deg F! I'll get some numbers on this setup, but I'm pretty optimistic that it will be good enough.

My front splitter is really too high off the ground to provide the intended effect, but it's a nice belly pan. I still need to sort out aero, but I'm less concerned about cooling needs now. The FWD hatchback Honda cars are definitely worth a close look.

 

[Siestarider]

I was following your car on Moto, esp the Ford ABS module application attempt. Fascinating build. Must be very quick.

My LSD is fantastic, but TVC still intervenes on power exits, I was trying to find a way to reduce that primarily for brake wear on track. This next track day I will log both front wheels and tease out just how much inside front brake I am getting, maybe its not enough to worry about.

I am torn between continuing undertray experiments or just going back to lower air dam, it produced better aero and cooling than undertray has so far. But a superior undertray is stealthy and would be a better option if I could just find the right recipe.

 

[McRib 1s Back]

Thank you. The car is a lot of fun, and despite the lost time on the module, I have TVC permanently disabled (while preserving ABS). I hear the FiST deals with TVC reasonably well when coupled with the diff, but I can tell you that TVC is plain wonky on a built car at the track.

The car is very good, but I haven't pushed it hard yet. As a clarification, I meant the finished car has only seen one track day.

I have a Quaife diff and Spec clutch/flywheel, but tested the car without those components. I'll have them in for my next event in a couple weeks.