Timing @ shake zone

Discussion in 'PSI Superchargers Tech Questions' started by max, Jul 11, 2020.

  1. max

    max Member

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    Looking back at some old interviews and many tuners mention pulling timing at the shake zone. Any idea on how much timing they pull assuming a good track and conditions? How long do they keep it out for? Is it a vertical ram back in or more of a 45? Thanks for any advice.
     
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  2. max

    max Member

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    Referring to an NHRA legal TAFC
     
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  3. Mike Canter

    Mike Canter Top Dragster
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    Depends if you wheelbspeed at the shake zone is too fast or too slow. If it is too slow you need to add timing and too fast you need to take it away. If all else is correct I would start with a degree
     
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  4. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    The best simple answer I got when I started digging into this subject years ago was "it's just a number" ...whatever it takes to get the tire calmed down, if it needs to be calmed down.

    Shake zone - you have engine rpm, driveshaft rpm and a coupling unit between them (clutch or converter). More power pushes the rpm line up. The tighter the track and hook built into chassis/tire is a downward force on the driveshaft line. Tighter coupling (more clutch or converter) is a force bringing the two together.

    Sounds simple enough right? The chaos theory in this equation is sidewall gyration. Spin hooks start a coil/recoil cycle in the sidewall.

    Timing is not a direct knob to change driveshaft speed.
     
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  5. Randy G.

    Randy G. Top Alcohol

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    You need to read the track to make the right decision. More times than not I fixed shake in my TA/FC by getting after it rather than trying to slow everything down. Why is it the fuel funny cars run 9 flat sixty foot times or quicker yet I'm trying to get mine to survive well above that?

    The last race we ran with my car was the 2012 Winternationals at Pomona. 4 runs in a row it shook. Little tweaks here and there didn't improve anything. We somehow won first round and I knew we were toast if I didn't fix it. Just like when we won Las Vegas a few years earlier I fixed tire shake by putting it on wreck through low. And that's what I did for second round. It ran right down the track. .920 sixty foot, 2.43 330' after a disastrous 3 rounds of qualifying and first round. The next run against Bartone it went through the clutch and we somehow survived. In the final it went right down the track again and we won.

    However, when I was tuning Keeter Ray's car at the 2011 Seattle divisional it was hot and the rubber was peeling up from 30' to 120' out but the starting line was stout. They were not scraping the track at all. I launched his car with full timing and a big low gear jet open so it would get up on the tire early, shut the jet and pulled 10 degrees timing at 1/2 second which controlled wheel speed. I opened the jet back up and put the timing back in at 1.5 seconds and ran my normal program to the finish line. Keeter's car was smooth as glass (not real fast) but it was all we needed to win the event. Everyone else was shaking their brains out trying to run fast.

    Bottom line is, there is no right answer. What works one day may not even be close the very next day at the same track.
     
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    Last edited: Jul 13, 2020
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  6. Ron C

    Ron C Jr. Dragster

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    Back I Think in the 80's. Garlits had a information board just inside his trailer door. The heading was ...."How to fix Tire Shake"......it went something like this. More start RPM, Less RPM......More tire pressure, Less tire pressure.....More clutch,....Less Clutch. It went on with about 10 items.....but you get the picture.
     
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