Coupe/Formula Front End Aero

[Shaun41178(2)]

I think an oil to air cooler might be the best option. I am sure there are equations to determine what size you need based on direct airflow or no airflow

Mine is mounted in front of my pass rear tire. No direct air and no fan. I don't know my oil temps as I don't have a gauge, but I never ran it hard for extended periods of time like you. Its quite obvious the factory oil to water cooler is just too small, and wasn't designed for that type of usage.

Did I miss what weight oil you are using? You might need to step it up to a thicker oil.

[Series8217]

I think an oil to air cooler might be the best option. I am sure there are equations to determine what size you need based on direct airflow or no airflow

Mine is mounted in front of my pass rear tire. No direct air and no fan. I don't know my oil temps as I don't have a gauge, but I never ran it hard for extended periods of time like you. Its quite obvious the factory oil to water cooler is just too small, and wasn't designed for that type of usage.

Did I miss what weight oil you are using? You might need to step it up to a thicker oil.

5W40 Rotella T.

I really need to drop the pan and get a temp sensor on it so I can see what the oil temps are really like... but the next track day is in 2 months so that's plenty of time to just install the cooler first.

[Shaun41178(2)]

I would not drop your pan if you can help it. Where is your oil pressure sensor located? If it is down on the block by the filter, or up by the coolant fill, like on a stock 2.8 in an 88, then maybe it wuold be simpler to put a T fitting in, and screw the sensor into that. I am pretty sure the Autometer electric oil temps gauges come with a 1/8th npt adapter for the sensor. If so, that will screw directly into the block or off a 1/8th npt T adapter so you can still have factory pressure gauge, and temp.

It will still be fairly accurate since that reads right by the oil filter which comes straight from the pan. It will save from having to drop the pan.

[The Dark Side of Will]

I would not drop your pan if you can help it. Where is your oil pressure sensor located? If it is down on the block by the filter, or up by the coolant fill, like on a stock 2.8 in an 88, then maybe it wuold be simpler to put a T fitting in, and screw the sensor into that. I am pretty sure the Autometer electric oil temps gauges come with a 1/8th npt adapter for the sensor. If so, that will screw directly into the block or off a 1/8th npt T adapter so you can still have factory pressure gauge, and temp.

It will still be fairly accurate since that reads right by the oil filter which comes straight from the pan. It will save from having to drop the pan.

A temp sensor will not be very accurate unless it has flow over it or at least immediately adjacent, or is surrounded by bulk fluid. A temp sensor in the pan would be good, but T-ing the pressure sensor for a temp sensor, especially with the remote mount like the Fiero uses, would not be good.

[The Dark Side of Will]

http://www.fiero.com/forum/Forum2/HTML/129597.html
http://angelonearth.net/customfiberglass/fenders.html

However... I'm not sure it's possible to get enough duct area from behind the radiator to these vents... It might be a help without being the cure that a hood vent is.

[Series8217]

http://www.fiero.com/forum/Forum2/HTML/129597.html
http://angelonearth.net/customfiberglass/fenders.html

However... I'm not sure it's possible to get enough duct area from behind the radiator to these vents... It might be a help without being the cure that a hood vent is.

I don't know if its possible to get any duct area from behind the radiator to those vents.

With some holes in the rear of the fender liner they might help let air out of the wheel well though. Clearly I need to start taking some differently pressure measurements at speed.. its the first thing on my list now.

[The Dark Side of Will]

http://www.fiero.com/forum/Forum2/HTML/129597.html
http://angelonearth.net/customfiberglass/fenders.html

However... I'm not sure it's possible to get enough duct area from behind the radiator to these vents... It might be a help without being the cure that a hood vent is.

I don't know if its possible to get any duct area from behind the radiator to those vents.

With some holes in the rear of the fender liner they might help let air out of the wheel well though. Clearly I need to start taking some differently pressure measurements at speed.. its the first thing on my list now.

There isn't any room for any ducting between the fender liner and the body. None.
Any such duct would have to go from behind the headlight bucket, THROUGH the front compartment above the steel wheel houses and then back through the wheel house into the "door hinge volume" served by that vent.

[Series8217]

http://www.fiero.com/forum/Forum2/HTML/129597.html
http://angelonearth.net/customfiberglass/fenders.html

However... I'm not sure it's possible to get enough duct area from behind the radiator to these vents... It might be a help without being the cure that a hood vent is.

I don't know if its possible to get any duct area from behind the radiator to those vents.

With some holes in the rear of the fender liner they might help let air out of the wheel well though. Clearly I need to start taking some differently pressure measurements at speed.. its the first thing on my list now.

There isn't any room for any ducting between the fender liner and the body. None.
Any such duct would have to go from behind the headlight bucket, THROUGH the front compartment above the steel wheel houses and then back through the wheel house into the "door hinge volume" served by that vent.

Why would I go all the way back around the headlight buckets instead of just going straight back from the radiator, to the same destination?

[The Dark Side of Will]

Depends on how much cutting you're willing to do.

Going from behind the headlight buckets, which share a common volume with the hood vent, around the edges of the front compartment and then out to the door hinge volume results in the least cutting of body metal and the least intrusion into the utility of the front compartment.

Your car is obviously developing rapidly into a track car. Mine will stay a street car. As such, I keep spare tire, jumper cables, tow rope, ice scraper, funnel, etc. in the front compartment on a continuous basis.

[Series8217]

Depends on how much cutting you're willing to do.

Going from behind the headlight buckets, which share a common volume with the hood vent, around the edges of the front compartment and then out to the door hinge volume results in the least cutting of body metal and the least intrusion into the utility of the front compartment.

Your car is obviously developing rapidly into a track car. Mine will stay a street car. As such, I keep spare tire, jumper cables, tow rope, ice scraper, funnel, etc. in the front compartment on a continuous basis.

I would end up cutting less if I went through the front compartment. There's no metal in the way. Just the spare tire tray. If I go past the headlights I"d have to cut the headlights.

The other advantage to ducting through the front compartment is the air goes straight back out of the radiator instead of turning 90* to the headlight areas. I could duct the outlet of the fan.

I have all of the same things in the front compartment (except an "ice scraper" whatever that is ) plus a tool kit, but minus the spare -- it doesn't fit over my brakes and I have a battery taking up some space behind the crossmember. I carry a full size 17x7 spare in the rear trunk on long trips. There should still plenty of room for all of those things above the ducts. I wouldn't cut any of the metal, so the space above it would still be available for supplies.

[The Dark Side of Will]

I don't have my planned "silly" brakes on the car yet, so I still keep the spare. Since that's most of the volume requirement for the front compartment, eliminating that would certainly free up volume for ductwork.

[Series8217]

So it turns out all of those internal aero mods I did for cooling may have been unneccesary... I inspected my coolant tubes today at the suggestion of the other forum, and my right side pipe is kinked pretty badly by the rear quarter panel. I always knew it had been bent up a bit when I bought the car, but I never checked the topside. It's been reduced to probably 30% of the original cross-sectional area. That sure doesn't help with flow...

[Series8217]

This car is so easy to work on! I took the coolant pipe out without jacking up the car, then cut it in the middle of the kink with a hacksaw, straightened it by banging in some sockets to make each side round again, now waiting for my buddy to weld it back together. Net cost: zero. I took pics of each step so I'll do a writeup on the repair. Since '88 coolant tubes are no longer available I think it'll be useful for somebody.

So back to the aero stuff...

EDIT: Here's the writeup on my coolant tube repair technique: http://realfierotech.com/phpBB/viewtopi ... 14&t=17797

[The Dark Side of Will]

The '88 coolant pipes are definitely designed for easy removal.

It may be surprising, but the '84-'87 pipes can be removed without jacking the car up. However, this requires removing the front bucket in order to access the single bolt securing the coolant pipe to the top of the front suspension crossmember. R&Ring the pipe is pretty fussy, but can be done. All that is required is to turn the steering away from the side being worked on.

I've had good results straightening pipes in exactly the way you described.

[Series8217]

Got a chance to write up some data I gathered at the end of August...

All measurements were taken with a Dwyer 605-3 magnehelic differential pressure gauge. Cabin air was used for the pressure reference.

Positive values are above the cabin pressure. Negative values are below the cabin pressure (and I had to switch the remote hose over to the low pressure port, with the cabin on high).

Test configurations:

For reference, here is a rough sketch of an ideal radiator duct:


Note: Splitter installed with partial undertray (back to the front axle centerline with control arm reliefs) for all tests. Windows up and A/C on MAX with blower at high speed for all tests unless stated otherwise. In all tests except Test 1, the splitter was sealed to the air dam and tire spats with duct tape.

Test 1 - Measurement hose tube installed in the front compartment radiator area, taped to the top of the overflow tank, pointing toward the radiator. Splitter installed, but not sealed to air dam.

Test 2 - Same as test 1 but splitter is now sealed to air dam with duct tape.

Test 3 - Tubing located inside inlet diffuser region of front radiator duct. "Diffuser" in the diagram above

Test 4 - Tubing located at center of left fascia duct to radiator

Test 5 - Tubing located behind left cable on top of the splitter. "Inlet" region in diagram above.

1 inch of water ~= 0.036 psi
(-) indicates lower than cabin pressure
(+) indicates higher than cabin pressure

Code: Select all

Test Config #     Speed (mph)     Gauge (inches of water)    Notes
1 (behind rad.)     0                 0.0                     AC on / radiator fan off
1                   0                -0.1                     AC on / radiator fan on
1                   30                0.1                     ''
1                   65                0.35                    ''

2 (behind rad.)     35                0.3                     ''
2                   60                0.4 to 0.5              peaked when passed or passing on fwy

3 (in rad. duct)    35                0.3
3                   40                0.3
3                   48                0.4
3                   60                0.7 to 0.9              drops to 0.5 when drafting

4 (ahead of duct)   40                1.0
4                   45                1.4
4                   60                1.5                     seems to increase when accelerating
4                   65                2.0                     traveling opposite direction from prev line

5 (splitter)        40                0.5
5                   60                1.0

I will post photos of the test setups soon. My primary hard drive recently died so I haven't had a chance to reinstall all my software yet, including photo editing stuff.

Some basic data analysis:

Code: Select all

Difference between radiator inlet duct and outlet pressure
Note: Positive number means higher at the inlet than the outlet
Speed                   inches of water
35                        0.0
60                        0.2 (drafting) to 0.4 (clean air)

I had previously measured the negative pressure produced by the fan at the radiator, but I can't find that data. I'll add it here when I do.

Nice to see that the radiator inlet duct is working as expected -- the air slows down as it enters the diffuser region of the inlet and passes through the radiator.

Now to just make some changes to help get the air out of there!

[Series8217]

Time for some more experimentation! This time with brake/hub cooling ducts. I rarely get the brakes too hot but it does happen sometimes on some tracks. If I can drop the hub/rotor peak temperature it should improve the longevity of the wheel bearings too.

Starting with the splitter I built earlier, and some "small NACA ducts" from Racer Parts Wholesale. These aren't really NACA ducts, as they don't have the right floor profile, angle, or overall shape. Will they work anyway? Maybe!


The duct as it arrives from RPW needs to have the border trimmed and the center hole cut out with a 2.5" holesaw.




Shape transferred to the alumalite splitter and cut out with a portable jigsaw:




Test fitting the duct:


Viewed from the bottom side (inlet):


Ducts riveted to the splitter with 1/8" x 1/2" aluminum rivets


Top side (outlets):


On the car with the 3" brake duct hose installed:


Top side where the 3" brake duct hose attaches:


The zip ties hold the duct to the tie rod so that the duct is pulled away from the brake rotor when the wheel is turned.


Backing plates are the next item on the list. Right now the duct just points at the middle of the rotor. The backing plates will also help guide the duct and keep it off the rotor. Then I just need a single attachment point on the duct to keep it away from the tire when the wheel is turned all the way.


I'm hoping to have the car ready to track test this setup this weekend.

[The Dark Side of Will]

Isn't under the splitter a low pressure area? Break out the magnehelic!

I wonder if ducting the airflow from behind the radiator would help with higher pressure or hurt with higher temperature?

[The Dark Side of Will]

I've been thinking about a front-end aero package for my car.

For a while I was thinking that I'd keep my hood whole and duct hot air from behind the radiator through holes in the bulkhead where the headlights mount, duct the air through the sides of the front compartment where the washer fluid reservoir is on the right and the corresponding volume on the left, then duct it outboard through a hole I'd have to cut in the sheet metal to the volume between the fender and the body. At that point it could come out the bottom of the fender or through "Z3" vents on the sides of the fenders.

This was in an effort to do two things:
1. Not send hot air straight to the cowl plenum from which my air conditioning draws in outside air
2. Not advertise the car via a conspicuous hood vent.

#2 isn't such a big deal if I find a reason or method to have exceptional function from a hood vent.

I had been starting to think of building an aero package like yours, but using the fiber reinforced rubber that you found here: phpBB/viewtopic.php?p=117705#p117705

I'd like to use that because of its flexibility. Appropriate anchoring and reinforcement would keep it stiff enough to produce downforce while keeping it flexible enough not to break when I hit something on the road or track. I'd like to set it up to force *ALL* of the radiator air out a large hood vent. The front edge of the permanently mounted aero package would be at the stock chin spoiler.

I'd run a "linear hook" or piano hinge transversely across the front edge of the stock chin spoiler and use a temporary attachment to hang a rigid splitter from that, using cables to the crash beam under the fascia. The "aero" fascia has a more open underside, so the anchor cables/turnbuckles could likely be installed/removed just by reaching up under the nose and hooking them in place, the splitter would then fold upward easily when I hit something with it, but have the vertical support in place to withstand downforce.

Since this setup would be used with a hood vent, I'd lose some effectiveness of the A/C when I didn't have it set to recirculate.
I was thinking that instead of ducting the radiator air out the fenders, I could duct the A/C air *IN* through the fenders... seal off the top of the cowl to keep from getting radiator air, then duct into the sides of the plenum via NACA ducts where Z3 vents might go. That probably wouldn't give me as much static pressure as the original location, but it wouldn't be pulling hot air either.

Also, if I convert from sunroof to slicktop, I won't have to worry about stowing the sunroof in the front compartment, and I can trim the front bulkhead sheetmetal a bit to enhance the usable cross section of a hood vent.

EDIT:
For the "linear hook" I mentioned above, I'm visualizing something sort of like this:


It would take the shear loads generated by downforce, pivot when the split gets schwacked, and come apart when I disconnect the anchors and swing the splitter out of its static position.