Coupe/Formula Front End Aero

[AkursedX]

I don't have a Fiero anymore, but if I remember correctly, there are two screw-in bump stops on each side of the decklid. How about running a steel cable with eylets on each end that you could run through the decklid latch and then secure them on each side with the bumpstops or a bolt and washer?

[ericjon262]

sounds like a PITA when you could pull the weatherstripping and do the same thing. maybe throw a couple of washers under the latch to get a little more lift.

[Series8217]

I don't have a Fiero anymore, but if I remember correctly, there are two screw-in bump stops on each side of the decklid. How about running a steel cable with eylets on each end that you could run through the decklid latch and then secure them on each side with the bumpstops or a bolt and washer?

That should be doable.

[fieroguru]

There is a product on the market for the C4 corvette rear hatches. It snaps to the hatch latch and then snaps into the stock catch and raises the rear hatch about 3" to improve venting and reduce buffeting when you have the windows down or the targa off. Should just snap in place for the fiero front hood latch, but you might want to make some stands on the outer edges to keep them from flapping at speed.
http://www.corvettegadgetman.com/products.html

[The Dark Side of Will]

I was going to suggest something like that... a little bar to latch into the stock hood latch with a cable that would clip to the stock latch loop on the hood. The length of the cable determines how far the hood can come up with the gadget installed.

[Series8217]

Some in-progress teasers:





Still need to make the passenger side wheel spat and mount both of them, add a seal between the splitter plane and the air dam, paint everything black, and set the angle.

Huge thanks to Alex (FieroGTRwideboby on the other forum) for his help in making this possible.

I took many pics during the process, and I plan to do a full write-up when its done.

I may also get a chance to do some dry lake-bed high speed aero testing this weekend. Crossing my fingers for that.

[AkursedX]

Awesome idea! What material is the splitter made of?

[Shaun41178(2)]

Looks good. Because racecar

[Series8217]

What material is the splitter made of?

1/4" alumalite. It's an aluminum/plastic composite with thin aluminum sheets on the outside and corrugated plastic on the inside.

[Series8217]

I tested it today on a dry lake bed at a bit over 100 mph. The front feels well planted. I still plan to add some wheel spats.

The splitter extends to the front crossmember and must be blocking some radiator airflow as I had some cooling problems. Venting the front compartment is the next part of the project that I need to tackle.

EDIT: Turns out the cooling problems were due to my fan relay having failed

[Series8217]

On the lake bed, showing finished front splitter:



The edging is 8672K42 UHMW Polyethylene trim. I wish it came in black!

[ericjon262]

looks good! can't wait to see the spats.

[Series8217]

I drove on Big Willow during a NASA HPDE for many laps. The splitter worked well at the track. No front end instability at up to 105 mph (20 - 35 mph headwind, so air speed was at least 125)



I didn't have time to build the spats yet. The car definitely needs drag reduction. I couldn't break 110 on the front straight due to a 20 - 35 mph headwind. The car never felt floaty; the front was in good shape even in a 100 mph turn.

My front left headlight cover popped up at ~95 mph with a 20+ mph crosswind. Unfortunately it opens more than its supposed to when it catches the wind and scratched the back of the headlight cutout on my freshly painted hood .

I think I'll get some of the headlight restraint cables from WCF to prevent further damage until I work out some fender or hood vents. The WCF restraints hold the headlight door to the headlight assembly, with just enough slack to be able to open the hood with the headlights down. This means the headlight doors can't open when the headlights are down, since the doors are secured to the lights. It won't help with front end aero, but it'll save my hood paint (and the doors).

My front tires aren't being fully utilized -- I need to run more static camber. Once I do that I think the front end is going to stick enough that I'll need some rear aero to help balance the car.

[Series8217]

My upper turnbuckle mounts are getting pretty banged up from hitting driveways with the splitter, so I'm going to try to source some cables in the next few weeks and convert the mounts. I will have a short adjustable section, and a crimped steel cable holding tension on the splitter. When it hits something the cable will become slack and allow the splitter to move up. When there is a positive pressure differential from the top to the bottom of the splitter, the cables will be in tension and prevent the splitter from bending downward.

[Series8217]

I switched to cables a few weeks ago. Despite some steep driveways and a couple offs, the splitter is holding up great. The cables allow unconstrained upward deflection, limited by the stiffness of the splitter.

The seal on the other hand, began to lose adhesion to the splitter and got pushed under the factory air dam by airflow. I added some duct-tape at the last track day as a temporary solution.

Even though I added the thermostat bypass line back to my engine's cooling system, I still experienced elevated temperatures at the track. I found some charts in Competition Car Aerodynamics by Simon McBeath showing delta pressure for a NASCAR race car with and without a splitter. The splitter actually slightly increases pressure under the car, in particular behind the front fascia. Since that's the only place for radiator air to get out, it's a possible explanation for my cooling issues. The figures in McBeath's book also show increased pressure in the wheel wells when using the splitter... which further reinforces the need for wheel spats on my design.

While it's possible to bend alumalite into the radius of the wheel well, it's not easy and I wasn't happy with the results, so I ordered some 1/16" ABS. I was looking for the 3/32" ABS I used for my previous Fiero's underbody tray, but it wasn't available. Unfortunately the 1/16" ABS is pretty flimsy and I'm not sure how well it will hold up at high speeds despite the small size of the spats. Nevertheless, I'm going to give it a try. I'll be adding the wheel spats pending differential pressure measurements of the front end regions critical to cooling airflow, so that I can quantify the results of adding them.

[Series8217]

Finally got around to weighing the splitter. It's 10 lbs. That doesn't include mounting hardware, which probably adds a couple pounds.

[Series8217]

Finished the first generation tire spats:

Closeup:


Mounting:


The next ones are going to be wider.. these don't completely cover the tire when viewed from the front. They're just flush with the splitter.

I also shortened the back of the splitter so I can get a jack and some jackstands under the front of the car. This also gives the radiator exhaust a bit more room to get out.



Also here's a closeup of the cable supports. They're ugly but they work:


The splitter can deflect upward as far as it wants to go, but the cables are immediately in tension when it has any downforce.

I don't think I showed the rear mounting points before; here is the bottom:


... and the top:


There's a round spacer between the splitter and frame to space it down level with the fascia. The hole in the crossmember was pre-existing.

I also revised the radiator duct by adding side panels cut from 1/16" ABS, and I moved the factory duct floor up so it's flush with the duct inlets on the front fascia. This should help reduce flow separation at the entrance to the radiator, and improve airflow.



In other cooling airflow news, I added a high-performance Spal radiator fan (p/n 30102082). This fan draws 22 amps and pulls 2470 CFM with no load. It's only slightly louder than the factory fan. I was able to make the factory fan shroud fit with some minor modifications and a foam gasket.

[The Dark Side of Will]

Sweet looking setup. You're putting a lot of work into this project.
No wonder your concerned about the stock fan wiring.

[Series8217]

Sweet looking setup. You're putting a lot of work into this project.
No wonder your concerned about the stock fan wiring.

I stopped using most of the stock fan wiring years ago. My fan power comes directly off the front-mounted battery with an inline fuse and goes to a standard 40A automotive relay mounted on the frame panel.

[Series8217]

Engine coolant temps reached upwards of 230*F today while pushing it hard, along with some lifter rattle (i.e. oil temp must have been horrible too), so I'm going to need a more comprehensive cooling package up front.

I didn't do the hood vent yet on this car because of the affect it had on the AC, but a friend brought up the idea of relocating the inlet. That may not be so hard to do, so I'm going to look into it.

Other options? Better ducting to the wheel wells or elsewhere... thicker radiator.. secondary radiator(s)..

Also going to add another oil-to-something heat exchanger... the air to water does no good if I can't keep the water temps down. I'm thinking under the right side quarter panel with a fan on it and a duct out to the engine bay vent, or wheel well if that would be effective.