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Old 11-03-2019, 09:39 PM   #1
clutch assisted
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Default Manual transmission racing on drag radials

I just read on dragzine that a guy by the name of Jonathan Adkins is racing his fourth gen. Camaro with a six speed manual transmission on drag radials. Hes using an 8 disc. The car was going 7.30s at over 195 mph this weekend at MIR raceway for the World Cup finals. I was always under the impression that drag radials didnt like manual transmissions. I guess things are changing?
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Old 11-04-2019, 12:40 AM   #2
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Default Re: Manual transmission racing on drag radials

I would love to hear how it's done, for the 5 speed SBC Nova.
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Old 11-04-2019, 10:13 AM   #3
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Default Re: Manual transmission racing on drag radials

Clutch technology, tire technology, and power management have come a long way. Also, MIR's surface is always on kill for the import vs domestic race. The yellow mustang they call TT minion has also been 7's on a drag radial.
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Old 11-04-2019, 11:10 PM   #4
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Default Re: Manual transmission racing on drag radials

I have been 1.26 60' on a 275 radial with a TTLS and a clutch @ 3480#.
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Old 11-04-2019, 11:27 PM   #5
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Default Re: Manual transmission racing on drag radials

Would love to hear some details!
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Old 11-05-2019, 02:54 AM   #6
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Default Re: Manual transmission racing on drag radials

Quote:
Originally Posted by Doc's Notch View Post
Clutch technology, tire technology, and power management have come a long way. Also, MIR's surface is always on kill for the import vs domestic race. The yellow mustang they call TT minion has also been 7's on a drag radial.
you are dead on...its in the clutch and power management these days... I'm truly amazed at how fast those guys go
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Old 11-05-2019, 10:06 AM   #7
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Default Re: Manual transmission racing on drag radials

DHR Darren, Id like to hear more about what youre using for a clutch, power management, etc.... Docs Notch, are you on a drag radial? Id like to explore my options with a naturally aspirated car that runs bottom nines, and should go high eights with more seat/tuning time.
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Old 11-05-2019, 10:23 AM   #8
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Default Re: Manual transmission racing on drag radials

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Originally Posted by clutch assisted View Post
DHR Darren, Id like to hear more about what youre using for a clutch, power management, etc.... Docs Notch, are you on a drag radial? Id like to explore my options with a naturally aspirated car that runs bottom nines, and should go high eights with more seat/tuning time.
I drive the car on the street with a radial, but on the track it has a 26x10.5 stiff wall slick. I am thinking about trying out a 275/60 radial pro once i get the car ironed out. Not going to change tires on a brand new combination.
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Old 11-05-2019, 02:05 PM   #9
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Wouldnt new setup be perfect time to switch to radials as it will be nowhere near a bias ply setup
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Old 11-05-2019, 02:57 PM   #10
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Default Re: Manual transmission racing on drag radials

No. I know how the car works on a slick, and I can get the clutch in the ballpark just knowing how much more power it makes. Anything with a radial would be a complete shot in the dark.
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Old 11-05-2019, 10:10 PM   #11
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Default Re: Manual transmission racing on drag radials

Calvert split monos, Menscer shocks all around, BS3 EFI & AMS 1000 boost controller, mcleod twin disc. Leave on 8# and ramp it all in by 1.75.
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Old 11-05-2019, 10:14 PM   #12
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Default Re: Manual transmission racing on drag radials

I believe they run Long style Black Magic clutches. And the Black Magic guys were at World Finals helping them tune the clutch.
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Old 11-06-2019, 02:05 AM   #13
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Default Re: Manual transmission racing on drag radials

I have 2 pluses then, I pray. I buy from both Cale, and Menscer.
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Old 11-06-2019, 01:08 PM   #14
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Default Re: Manual transmission racing on drag radials

The big things to consider with stick shift and radials is...
...1- that the radials need to dead hook.
...2- there's an energy release that happens on the shifts.

On my 4spd car, the 1st/2nd ratios indicate an 8500 shift point would drop to 5900 after the shift. That may not sound like a big deal, but you need to consider that the entire rotating assy is basically a flywheel that stores energy as it gains rpm, but then discharges that stored energy as it loses rpm.

Lets say you have an entire rotating assy (crank/flywheel/pressure plate) out of the engine and spinning on bearings at 1000rpm. That rotating weight spinning at 1000rpm contains a fixed amount of energy that can be put to work. One way to measure that stored energy is to apply a braking force to the rotating assy and then measure how long it takes to bring that rotating assy from 1000rpm to a full stop. Lets say a braking force of 100ftlbs can take that rotating assy from 1000rpm to a full stop in 1 second. Basically the energy contained at 1000rpm is 100ftlb/seconds. Sounds pretty reasonable so far, right?

Now consider that the energy contained in the rotating assy is exponential. Spin that rotating assy at twice the speed, it contains not double but 4 times the energy! Doubling it's speed it goes from 100ftlb/seconds to 400ftlb/seconds. Spin that same rotating assy all the way up to 8500rpm, now it contains an amazing 7225ftlb/seconds of energy! Said one way it's 7225 foot lbs of work for one second, but said another way it's also 722.5 ftlbs of work for 10 seconds. Sounds like you could just spin the engine up to 8500 and just make a pass on flywheel energy alone, but remember at the end of ten seconds rpm would be down to zero.

Now lets consider what happens when you shift. At 8500rpm, that rotating assy contains 7225ftlb/seconds of energy. But let's say that after the shift, rpm drops to 6000. At 6000rpm, that rotating assy contains only 3600ftlb/seconds of energy. That's a difference of 3625ftlb/seconds. What this means is that the rotating assy must shed over half of it's stored energy in the length of time that it takes to complete that shift. If the shift took a full second, that's a 3625ftlbs energy release that needs to go somewhere. If shift time is cut in half to 0.5 second, the intensity of the energy release gets doubled to 7250ftlbs over half a second. When you look at a wheelspeed graph of a clutchless shift, it's that energy discharge that causes those big wheelspeed spikes. That energy has to go somewhere. Spinning the tires for a few fractions of a second usually doesn't cause any harm, but very little of that energy spent knocking the tires loose actually gets recovered to make the car quicker. Put radials on the car, now knocking the tires loose makes the car slower.

Basically with a radial you need to manage that energy discharge to a level that the tires can handle. More gears (4spd vs 5spd) is an effective way to reduce rpm drop on the shifts, which effectively reduces the amount of energy that needs to be released. You can also use clutch engagement rate to spread the energy discharge after the shift out over a longer period of time. You need a clutch that can take some abuse, but careful management of clutch engagement can spread that energy discharge over a much longer time period. The goal is to spread the discharge over a long enough time period that it's reduced to a level that the radials/chassis can handle. When that isn't enough, last resort is pulling just enough power during the shift to keep the radials stuck. Comparing ET to MPH will tell you a lot about whether a car is recovering that energy discharge efficiently or simply reducing power thru the shifts to make it all work.

Grant
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Old 11-07-2019, 05:42 AM   #15
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Default Re: Manual transmission racing on drag radials

I would like to try radials one day but as mentioned above, I somewhat know what will work with a bias slick so that’s where I’ll start. I do believe there is much to be said about shocks (on any application, I suspect more so on a stick / radial attempt).
I am back-halving my car right now with CM tube and a 4-link. I am also going from AFCO DA’s all around to Santuff up front and 4-way adjustable Ohlins out back. Advanced Clutches Billet Single 8” clutch assembly. Should be interesting.
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