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Help needed to get the most out of 5th gear at the drag strip

Help needed. Have appointment at Milan Dragway on the 19th of June (2015).

My car is not drag optimized, its got wicked stiff cortex dampers on it and a 3.55 gear. 5th gear will be needed in the 1/4 mile - 3.55 gear, 1.32 MT82 4th gear ratio, 7400 rpm max, small 25" Hoosier drag radial gets me 117mph. I'd rather shift at 7200 to save the motor that's only 114 MPH. Last year with a 3.15 gear at about 6800 rpm in 4th it ran 122 MPH.

Since i'm stuck with four gear changes is there a way to make 5 gears work better than 4 in a quarter mile? Shaun from AED said to avoid the shift to 5th if at all possible because it just reduces MPH and increases ET but that would not work for me.. engine would not be happy going through the traps at 7700-7800 rpm! :-\

edit: here is my power curve in case you want to look at peak torque vs. rpm vs. HP?

dyno-aed-vector.jpg
 

TMSBOSS

Spending my pension on car parts and track fees.
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Wingrider said:
Larger diameter slicks/tires? That would impact ratio tho.

Taller tires. Easiest/cheapest solution.

I top out 4th with 295s street tires running 12.4s.

Starting in second may be an option.....not a great one.

If you are running a Torsen diff, be caution of the abuse to the Torsen from drag strip launches.
 
I need the free option having just purchased my 15x8 drag stars last year along with this 9x25" drag radial. Hoosier drag radials 17315 (275/50/15) probably have 10-15 more runs on them. One good thing they are 10lbs a tire lighter weight than the 28" Radial pro from MT.


Only thing I can think of is shifting early from 4th to 5th to stay in the torque curve more but that wouldn't even do it. the peak torque is about 5500!
 
OK, drag race day is complete here are some observations.

there is no good way to make 5th gear work for optimized 1/4 mile ET or speed.. every time I went to fifth no matter what the circumstances it added 0.3-0.4 seconds to my time and knocked MPH down 3-4.

best ET was [email protected] MPH with a 1.74 60' that was coasting for the final 100 feet of the 1/4 mile since I was already at 7700 rpm in 4th. My poor non Boss GT rods! DA was about 2500 feet.

Lesson learned, I could have purchased larger slicks like the 28" radial pro and been perfectly setup. TMSBOSS AND Wingrider hit the nail on the head.
 

Wingrider

'11 GT500, 99% Track Car. Lots of mods & I coach
TMSBOSS said:
11:54 is a very respectable time.

A slightly taller slick and you should be dialed in.

Good luck.

Sell the slicks you have and get a taller set. Will also help you on launch a little. Less Wheel spin but maybe a minor impact on 60ft. Sort of a trade off unless you launch at a higher rpm.
 
Wingrider said:
Sell the slicks you have and get a taller set. Will also help you on launch a little. Less Wheel spin but maybe a minor impact on 60ft. Sort of a trade off unless you launch at a higher rpm.


Engine Speed 7600 RPM
Transmission Gear Ratio 1.32 in 4th
Differential Gear Ratio 3.55
Loaded Tire Radius 25" approximate measurement
Vehicle Speed 120.6 MPH measured at end of 1/4 mile

increase tire to 28" diameter radial pro same 7600 rpm in 4th is 135.1 MPH. Assuming a better 60' than 1.72 since most guys can get a 1.5x easily with that tire on our cars I should be able to hit 125mph. Or will my small block not have enough at the top end?

I must admit the feeling of first gear hooking up hard is addicting. This old 2012 GT mustang rocketed forward so bad I ground second due to my foot coming off the clutch pedal a little, fixed it by moving seat forward. My best race of the day was against a pal in his 2000 SS LS1 Camaro. Since we rented the track it felt just like hanging out on Saturday night and then backing up your shiznit talk with a full 1/4 track right there! He got me on the hit due to automatic but the mountain motor 302 caught and passed him right at the line. ahhh so fun! :)
 
Wingrider said:
Get the tires a little hotter, perhaps drop tire pressure a little for a harder bite at the launch.

Here is the video vs. my buddy's 2002 SS LT1. Its a nicely built engine with Lingenfelter heads, big tube headers, comp cams, etc.
https://www.youtube.com/watch?v=lqBsMMhS7n8

He did a 12.1 me 11.6 on this run most gains were after 330' for the big breathing Coyote.
 
I find it amazing you're going 120 mph N/A. As for your tire selection and rear gear combo, It would seem you need a 28" tire. I go through the traps with a 3:73 and 28" tire and the motor is begging for a shift.
 

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