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Old 04-16-2019, 08:06 PM   #1
Marc
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Default Any downside to lowering cruise RPM?

After a couple test passes today to make sure the car is ready for the season, I decided to mess around with cruise RPM for no other reason than to see how the car responds. I dropped from 4200 to 3600 and noticed an almost 2 mph increase with nearly a full second less stop time to run 9.90. Datalogger shows an equally flat cruise RPM at the lower RPM and 20 mph less wheel speed when coming off the stop. The car was very good all year with the higher cruise setting, but I'm liking the little extra MPH and shorter stop time. Anyone experience a downside to this?
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Old 04-17-2019, 02:20 PM   #2
Lenny5160
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Default Re: Any downside to lowering cruise RPM?

As long as the car comes off the stop clean and you are still on the stop when you cross the 60' timer, then you should be good.

There is not really a need to be on the stop across the 60' timer, but I personally think it helps a lot to have some kind of ET number that remains constant even after changing the throttle stop timer to give an indication of track conditions or why you were quicker/slower than you intended.
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Old 04-17-2019, 10:10 PM   #3
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Default Re: Any downside to lowering cruise RPM?

As long as it stays flat on the stop you are better off. Less numbers in the timer.
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Old 04-18-2019, 09:42 AM   #4
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Default Re: Any downside to lowering cruise RPM?

When I tried this the only time I got into a bind was in really poor weather conditions where the car was not making much power. The lower setting with the bad air (4500 DA+) would create a little hiccup coming off the stop. I liked to run the car a little on the rich side always so I'm sure that played a part in the issue. I tried not to make a bunch of carb changes throughout the year.
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Old 04-28-2019, 08:05 AM   #5
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Default Re: Any downside to lowering cruise RPM?

It's easy to get caught up in the mph game. But what gain do you actually see from 2 mph on the race track versus an opponent? I have found that a lower t/s rpm raises many more variables. Drastic weather conditions would change the rpm more. But the biggest issue is wind. At a lower rpm, you are "coasting" through the wind, and not "driving" through it.
But that's just my free opinion. You can take it for what its worth!
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Old 04-29-2019, 09:08 PM   #6
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Thumbs up Re: Any downside to lowering cruise RPM?

Back to back finals this weekend, crazy wind , 1/8 mile ,then 1/4 mile , great job Mark . Jim Fordyce
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Old 04-29-2019, 10:03 PM   #7
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Default Re: Any downside to lowering cruise RPM?

Good information thanks...that's exactly what I was looking for.

I am actually coming off the stop before the 60ft (1.6 seconds of stop time and 60ft is 1.9x) so 60ft times are moving more than before, but that's about the only downside I'm seeing. I'll be curious if like the one guy said bad air might cause some consistency issues. So far so good though the car was repeating very well in my first two races.
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Old 04-29-2019, 10:05 PM   #8
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Default Re: Any downside to lowering cruise RPM?

Quote:
Originally Posted by 1752supgas View Post
Back to back finals this weekend, crazy wind , 1/8 mile ,then 1/4 mile , great job Mark . Jim Fordyce
Thanks Jim...definitely a good start to the season. Would be nice to win one at some point though.
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