And I think 140 ish might be achievable if you can improve the car's drag a little. Assuming you can get to 100 mph by the first 1/4 marker you are now travelling 146 ft/sec and will have less than 9 seconds to hit 120 mph by the 1/2 mile marker. You are now travelling at 176 ft/sec and in 5th gear and will have 14 seconds to accelerate from 120 to 140 (assuming hitting 190 ft/sec [130 mph] before the last 1/4 marker).

A base might have a slightly better run than a sport with no spoiler, smaller wheels and open diff. The gearing of the auto might also be more favorable.

So - borrow and auto base model and give it a shot :)

taller tires? Might give a little edge. Maybe skinny ones too, since its a straight line?

I was actually thinking shorter tires. It would give a gearing advantage similar to running a different rear end ratio.

shorter would accelerate a little quicker, but taller would give a higher final speed. If going for top end, I would think that would be better. My speedo is 10% off with shorter tires. Would be interesting to see final straightaway speeds with stock sized vs. what I run.

I calculate top speed as 160 mph in 5th with stock tire size. A 10% gearing advantage would make it 154 but he'll run out of road long before hitting that. The taller tire would work if it eliminated a gear change and he was able to hit the target in 4th. This works to my advantage on a couple of tracks I've run, can eliminate 3-4 extra up shifts a lap.

As pointed out, I will run out of track long before I hit the top speed of the car so acceleration and aerodynamics are the focus here. The other focus, not spending much money since this is a one-time event. The eventual focus for my car is still the road course so things that would be good for the standing mile, like skinny front tires, drag radials, etc. are out of the question since I will likely only be using them once. The goal here is to spend as little money as possible and by that, I mean the only thing I am spending on is sheetmetal and spray paint from Home Depot...and a new set of tires, which I need anyway and those tires are being purchased with the road course in mind, not a standing mile.

So the advantages my car already has over an off-the-showroom stock 370Z are as follows...

- 21 lbs. of weight savings from the Odyssey Battery
- Better acceleration from smaller OD, lighter wheels/tires
- Better grip off the line with 10mm wider, stickier rear tires.
- Adjustable compression/rebound to aide in a better launch.
- Lower ride height = less air going under the car = less drag.

Again since it's a one-time event I don't really want to spend any money on it. I have spent a total of $80 at Home Depot so far. Here's all I have planned to help improve my speed...

- Sheetmetal side skirt extensions to reduce drag by blocking air from entering under the car.
- Sheetmetal front air dam does the same thing at the front of the car.
- Sheetmetal front/rear wheel spats block the spinning tires from the air flow and forces air around them reducing turbulance/drag.
- Fold in side view mirrors to reduce frontal area and reduce drag.
- Tape & seal all seams on exterior to create a smooth surface and reduce drag.
- Brake duct block off plates (if I have the time and energy I may do a series of plates that block off part of the grille opening again, to create a smoother surface area and reduce drag.
- Remove passenger seat saves weight to improve acceleration.
- Remove spare tire/tools saves weight to improve acceleration.
- Run with as little fuel as I can to save weight and improve acceleration.
- Run max tire pressure to reduce rolling resistance.
- Adjust suspension to move weight to the rear under acceleration for better launch/traction in the low gears.

I also may try one or two runs with the stock rear muffler section removed. I know this doesn't add much, if any power but it will shed some weight. I have a feeling that the gaping hole left where the muffler used to be will negatively effect the aerodynamics to the point where I will actually be faster with it installed. Only one way to find out though.

By my calculations, the car should weigh in at around 3,350 lbs. with me in it come race day. Power wise, as of now, the car will be 100% stock right down to the paper air filters. I can't really think of anything else to do to the car that is easily reversable and free but if any of you have more ideas, let me know!

how about practing your launch? not a natural act for TT / road race guys

I started as a drag racer back in 2001....shhhhh.... :wtf2:

I am not planning on doing a traditional drag style launch, but more of a roll off start instead. A drag style launch, done perfectly in a Z is tough, especially if your tires are aired up to a high PSI like mine will be for reduced rolling resistance. I think a drag style launch can hurt me more than it can help me if its not done absolutely perfectly. Plus the shock of a traditional launch is hard on the car.

... not that there's anything wrong with that! haha

okay, another possible easy add on idea... vortex generators strategically placed to help with airflow separation on roofline and rolling off the rear hatch

these just showed up at my house this afternoon, in fact... now that I have no aero restrictions will be going on the car

http://i656.photobucket.com/albums/u...909-1535-1.jpg

also, can you ditch the side mirrors for the event? maybe that's taking it too far?

Following back up on an earlier topic... I measured my camber at last weekend's event... sure enough, the SPC arms did NOT hold camber... left measured ~1 degree, right ~3 degrees... unfortunately opposite of what I needed for a clockwise event

The vortex generators might actually be something worth trying. Seems you can find universal ones pretty cheap online. Here's a link for a set of 10 for $20...

Amazon.com: Vortekz Universal Vortex Generators Black 10 Pieces: Everything Else

Which ones did you get?

As for the mirrors, I have to drive the car to and from the event (about a 3.5 hour trip each way from Vegas) so I definitely want them on there for that. Probably too much hassle for what its worth to do at the event or between runs but you never know. If I am within 1 mph of my goal then I may just be persuaded to take them off.

I splurged for the ones that are proven to work on low-speed aircraft...

STOLSPEED VORTEX GENERATORS from Aircraft Spruce

$100 pack is probably enough to cover 2-3 cars, so I'll have some left over... but won't know until I get my car back in a few weeks - otherwise I'd send you half

Those are super tiny! Wondering if bigger ones are usually used on cars because of the lower speeds or because they are usually positioned on the roof instead of on a wing. Hmmm... may have to try and speak with people who are smarter than I on this one.

Doing some quick reading, choosing the correct height of a vortex generator depends on the thickness of the boundary layer of air where you plan on placing the fins. You want the same height fin as thickness of the boundary layer. Wondering if the profile of a car creates a much thicker boundary layer over the roofline of a car than an airplane wing creates over the top of its surface. Furthermore, if these work on the top of an airplane wing, wouldn't they then work on the bottom of a car wing to increase efficiency? Can't say I have ever seen that done before...

my understanding... they are used on a wing to help when the AoA exceeds 15% or so... they keep the flow more efficient in that situation in particular... for that reason, i'm not sure how useful they'd be on the underside of our wings... a question for the more educated on this subject for sure

re small fins... what I plan to do is put them a little further afield in the airstream where the boundary layer remains thin...

... but it would be nice to have some data that helps us understand how high the fins should be

these are used on kit aircraft by the way... those things cruise at 150-175

Autospeed has quite a few aero articles related to this sort of discussion

Vortex Generator 4 part series (They specifically test the vortex generators on the underside too):
Vortex 1
Vortex 2
Vortex 3
Vortex 4
Also in that article they show some data from Mistu EVO tests that seems to suggest that 25mm high or so is best.


Aero Testing 5 part series:
Aero 1
Aero 2
Aero 3
Aero 4
Aero 5

Underflow 2 Part Series:
Under car 1
Under car 2