Aero mods for 1/2 mile

[FNBADAZ06]

My last trip to NFZ, I had some major front end lift which may have had an impact on my terminal traps speeds at the rolling start 1/2 mile. I can't fully quantify the impact it had on my standing starts as I was gear/rev limited to 163 MPH at the last event with my 315/35/17 Hoosier drag radial, but I know that turbulent air under the front end causes excessive aero drag. My rolling 1/2 mile runs had me at the high side of 166 MPH, running a short rear tire and having to shift into 5th gear which kills any acceleration. My nose up pitch also caused the instability at the steering with my ZR1 splitter capturing high speed air and causing lift on the front end.

 

 

To combat the lift and address my gearing shortcomings to maximize my trap speeds, I've changed to a new wheel/tire setup, and modified my aero to minimize drag (hopefully).

 

[FNBADAZ06]

First up is the switch to a different wheel/tire combo. My last event I ran my street tire up front, the 285/30/10 run flat (25.73" diameter) on a 19x10 front wheel, with a rear 315/35/17 drag radial (25.35" diameter) on 17x11.5 CCW's. Mixing run flats with regular radials didn't help, but having a taller tire up front really exaggerated my nose up pitch.

 

THis coming event, I'll be running a 205/50/17 front tire (25" diameter) with a 285/40/18 rear tire (Nitto NT05R advertised at 27.09" diameter). I tested the 2" diameter difference for any  issues with drag control/stability control messages or issues..check ok.

This gives me a nose down pitch angle, which should help with the nose up attitude at speed without having to adjust my factory settings for ride height 

 

My aim with this new setup is to help me reach my goal of hitting 165 MPH in the standing 1/2 mile runs. My calculations suggest 27" rear tire diameter should help me reach that goal without killing my acceleration rate too much. As a note, I ran a best at the standing start 1/2 mile in 17.68 seconds at 160.7 MPH last time. While this is a terminal speed event, nobody would brag about hitting 165 MPH while getting drug down the track and getting beat to the 1/2 mile stripe....evidenced by the many YouTube videos that have been posted about "beating" a particular car in the 1/2 mile while rarely discussing the trap speed....the Supra are well known for ET to trap speed differences (mid 10 second ET, but 150+ traps). The 27" tire will probably knock my ET back by a .5 to .75 second or so.....ET's in the 18 to 19 second area,

 

I could possibly run a taller tire to maybe hit a higher trap, but at the expenses of ET. Plus, I don't know if I have enough power to pull a really tall tire in a 1/2 mile standing start.....I'd probably run slower in both ET and trap with a 28" as it would REALLY kill my rear gear for standing starts.

Rolling starts with 1/2 mile plus 300' , the 28" tire might be worth something.

 

 

[FNBADAZ06]

My next mod is my aviation nerd showing up LOL . I was originally in school for an aviation career which I was never able to achieve, but still have a love for.

I have an understanding of aerodynamic drag coefficient, frontal area, airflow with regards to lift and drag, etc.

The more air that gets under the car, and with no belly pan running the length of the car to streamline the air flow, the more turbulence you get as the air tumbles under the car, causing drag. Many new high end exotics (and even the new electric cars who concentrate on max MPG) have employed active aero, to include front end shutters to limit airflow into the front engine compartment, to active front airdams which lower into place as speeds climbs to minimize airflow under the car, reducing drag and adding some down force. Many of these cars also have active rear wings/spoilers, which will retract at high speeds to maximize top speed.

 

For me, I noticed a significant impact on front end lift when I switched to the extended ZR1 rear spoiler. Not only did it cause the front end to become noticeably lighter, it created enough rear down force to compress my rear suspension enough for the rear fender lips to contact and rub on my rear tires...and I'm at factory ride height.

 

[FNBADAZ06]

To combat this aero drag, I'm reinstalling my factory OEM duck-bill "Gurney" spoiler to minimize drag and rear down force.

On the front, I have reinstalled my factory air dam, but with a mod.

I have added a 3.5" rubber airdam extension to my factory unit in an attempt to limit airflow under the car. I had removed the rubber air dam underneath the car at either side of the car which cause a high pressure area at the brake ducts under the Z06 front end to help cool the front brakes at the track. The center air dam is there to limit the airflow under the car, in an attempt to minimize drag and boost fuel economy. Both of these cause front end lift at high speeds.

 

I don't know if my new front air dam mod will have a significant impact on airflow and terminal speeds in the relatively short standing start 1/2 mile run, but 1 mile and 1.5 mile I think it will help a lot.

We shall see

 

 

[Ted Y]

I'm not sure about high speed effects, but it should have a significant impact on driveway entrances. 

[FNBADAZ06]

11 hours ago, Ted Y said:

I'm not sure about high speed effects, but it should have a significant impact on driveway entrances. 

I'll install it once at the track...but, you're correct on the driveway entrance. It is flexible rubber, though