Ask AJ Hartman - Aero Questions

[Fabman]

I was going to suggest a junkyard hood. I cannot confirm, but I do believe a stock GT hood is compatible. There's a large number of GT500 bumper conversions on GTs floating around the net that appear to show them with the stock hood. Maybe pull the hood off your "Cinderella" GT and try fitting it to the Shelby to check?

Now that's a great idea!
I'd personally like to know for sure if they interchange......I've heard both yes and no answers.
How about it @blacksheep-1 ?

 

[blacksheep-1]

So now you guys want ne to dismantle BOTH cars....

 

[Fabman]

So now you guys want ne to dismantle BOTH cars....

Its a hood....you can handle it.

 

[blacksheep-1]

Wifey projects, so I can go out and play, remodeling her kitchen.

 

[xr7]

Are there any generalities that you can share? I just picked up a spare deck lid to mount my CAM spoiler. Here's the rule:

Rear spoiler may be added, but may extend no more than 10.0” from the origi-
nal body nor past the perimeter of the body. No rear wings may be added except
OE or equivalent.

Also, it can only be a flat plane spoiler. End plates or gurneys are not allowed. If they were, a spoiler off of a Modified would be a no-brainer.

My idea is to do 2 half-width piano-hinge 'stock car' spoilers which extend laterally as far as allowed and meet at a small angle in the middle. I'll cover the gap between the two with gaffer tape. The back side will be supported by strut rods and I want to have separate 'track' and 'highway' mounts which will be about 70 degrees of angle different.

It's kinda making chicken salad out of chicken $h!t. I didn't write the rules; just building to them.

TeeLew, I like your idea, have been thinking about getting a spare decklid myself. Once you have your hi and low mount angles figured out you could have a third piece that bolts in to fill the gap. I like the idea of the two piece because I can toss it in the trunk when I'm just going for a drive.
So it looks like you can't curve the outer ends of the spoiler to grab the air and push towards the central area of the spoiler?

 

[Duane Black]

I saw some earlier stuff about a flat floor - any updates regarding drag or lap time improvements?

For reference, my car is tge 2013 Hertz special.

I am looking at making panels to fit the floor pans and make a nice flat floor. I think I would leave the exhaust and transmission open for cooling, so that makes my surface area much smaller. I have a trailer hitch out back, so smoothing that out somehow with a plate should help.

I was thinking of some sheet aluminum for this project.

@AJ Hartman - is it worth it?

Other aero mods - the fender liner fell out. I also still have the panel that blocks the oil filter, but I thought it had something blocking the oil pan from the factory - should I build a replacement? And if so, any ideas how much better the top speed may be?

 

[mavisky]

Now that's a great idea!
I'd personally like to know for sure if they interchange......I've heard both yes and no answers.
How about it @blacksheep-1 ?

Aftermarket 05-09 hoods are interchangeable across all Mustang models aside from potential clearance issues on cars with top mounted blowers that may reduce clearance for hoods with deep vents.

As I recall the GT500 has a different bumper profile that's "pointier" than the regular GT so the hood was pointier to match. Otherwise the attachment points were all identical.

 

[Fabman]

Aftermarket 05-09 hoods are interchangeable across all Mustang models aside from potential clearance issues on cars with top mounted blowers that may reduce clearance for hoods with deep vents.

As I recall the GT500 has a different bumper profile that's "pointier" than the regular GT so the hood was pointier to match. Otherwise the attachment points were all identical.

I have dreams of getting one of these noses but between the price of the nose, the paint and also getting a new hood plus GT500 louvers is just a bridge too far I'm afraid.

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www.modularmotorsportsracing.com

 

[AJ Hartman]

I saw some earlier stuff about a flat floor - any updates regarding drag or lap time improvements?

For reference, my car is tge 2013 Hertz special.

I am looking at making panels to fit the floor pans and make a nice flat floor. I think I would leave the exhaust and transmission open for cooling, so that makes my surface area much smaller. I have a trailer hitch out back, so smoothing that out somehow with a plate should help.

I was thinking of some sheet aluminum for this project.

@AJ Hartman - is it worth it?

Other aero mods - the fender liner fell out. I also still have the panel that blocks the oil filter, but I thought it had something blocking the oil pan from the factory - should I build a replacement? And if so, any ideas how much better the top speed may be?

Unfortunately I did the flat floor the same time I swapped to hoosiers, but per the rules, had to add 250lbs to stay legal. So nowhere near an apples to apples deal. But having said that, even with the higher weight but same power, my mph was almost identical to previous events, maybe 1-2 mph slower. It definitely wasn't an apples to apples deal so keep that in mind. So I definitely want to revisit it, and would say they are generally worth it if they are allowed, but should keep an eye on things like trans and diff temps. And if you need to keep the whole center open for trans and exhaust cooling (good idea btw), the effect will be diminished to a degree.

 

[TeeLew]

And if you need to keep the whole center open for trans and exhaust cooling (good idea btw), the effect will be diminished to a degree.

Assuming there are no legality issues, would some sort of underside turning vanes (think the bow of a boat) to encourage the air to go around the open tunnel would probably be a good idea?

I'm in the process of doing a nose floor on my daughters Z. I'm starting with thin birch sheet from Home Depot and putting a single skin of glass top and bottom. That's a reasonable 'low buck' option. I'll post a pic when I'm done.

If doing a full floor, I would recommend making it in sections. Dropping the entire floor to service the engine or transmission sucks.

 

[AJ Hartman]

Finally got a chance to make it to the big tunnel mainly used by NASCAR and IndyCar. We now have the ability to compare direct data points from CFD, static floor wind tunnel, and moving tunnel. So much data to dig through still but the more data the better.

 

[blacksheep-1]

Now that's a great idea!
I'd personally like to know for sure if they interchange......I've heard both yes and no answers.
How about it @blacksheep-1 ?

They mechanically interchange, they are not the same the front of the hood on the Shelby has a lip that goes around the opening of the radiator entry. Probably 90% of the people out there wouldn't notice.

 

[Fabman]

They mechanically interchange, they are not the same the front of the hood on the Shelby has a lip that goes around the opening of the radiator entry. Probably 90% of the people out there wouldn't notice.

So, close enough. Excellent.

 

[AJ Hartman]

Forgot to add this video here. Tons of good data and can finally put to rest the "wheels aren't rotating" argument. Enjoy!

 

[Bill Pemberton]

Just a little note of caution using a sheet of birch or marine grade plywood, I watched my old Boss's 96 Viper GT1 burn to the ground using a wood underside. Later heard of a friend who had copied the idea on his car almost burn up too, and luckily it was caught in the pits.

Brake fluid, power steering fluid , engine oil , trgnnyfluid, diff fluid , etc. with small leaks, over time, soak into the wood and bingo you have a barbecue all ready for igniting. Bringing this up as many cars have some leaks on occasion and if you don't catch them all you no worries you have a tray to catch it all. Just a thought to consider before using wood ..........................

 

[Paul McWhiskey]

On the latest "Faster with Finnegan" they were V8 transplanting an '86 Fiero (Sheesh!). Mention was made that the Fiero had a reputation for catching on Fiero due to some models having a magnesium engine support that could become oil soaked from leaks and ignited. I imagine that any material soaked with enough flammable fluid can be ignited under the right conditions. However, one is well advised not to use materials that are fuel for said fire, which will ensure that the rest of the car is totally engulfed before fire crews can get to it.

Thanks. Good advice.

 

[TeeLew]

Just a little note of caution using a sheet of birch or marine grade plywood, I watched my old Boss's 96 Viper GT1 burn to the ground using a wood underside. Later heard of a friend who had copied the idea on his car almost burn up too, and luckily it was caught in the pits.

Brake fluid, power steering fluid , engine oil , trgnnyfluid, diff fluid , etc. with small leaks, over time, soak into the wood and bingo you have a barbecue all ready for igniting. Bringing this up as many cars have some leaks on occasion and if you don't catch them all you no worries you have a tray to catch it all. Just a thought to consider before using wood ..........................

In my opinion, using thin birch for a core is fine, but you have to skin each side with glass. Using it alone is making a candle wick.

 

[TeeLew]

I know the Fieros would catch fire, but I'm gonna call BS on oil-soaked Mag. There's gotta be a "By the way." I've had plenty of Mag bellhousings and gearbox pieces that never spontaneously combusted.

 

[mavisky]

Just a little note of caution using a sheet of birch or marine grade plywood, I watched my old Boss's 96 Viper GT1 burn to the ground using a wood underside. Later heard of a friend who had copied the idea on his car almost burn up too, and luckily it was caught in the pits.

Brake fluid, power steering fluid , engine oil , trgnnyfluid, diff fluid , etc. with small leaks, over time, soak into the wood and bingo you have a barbecue all ready for igniting. Bringing this up as many cars have some leaks on occasion and if you don't catch them all you no worries you have a tray to catch it all. Just a thought to consider before using wood ..........................

Underside as in under the engine, trans, exhaust?

That's definitely something that's an aggressive move especially given the heat from headers and cats and such.

Using one as a front splitter away from any spark/heat and most flammable fluids isn't really a concern. For a center body flat bottom I'd look into something like alumalite over plywood/fiberglass personally, but both would probably work.

 

[Paul McWhiskey]

I know the Fieros would catch fire, but I'm gonna call BS on oil-soaked Mag. There's gotta be a "By the way." I've had plenty of Mag bellhousings and gearbox pieces that never spontaneously combusted.

I was only repeating what was said on the show. Actually, I had the same thought as I wondered how so many magnesium parts have passed inspection on tracks all over the world.