What RPM would you shift?
#3002637
01/06/22 04:21 PM
01/06/22 04:21 PM
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Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
OP
Senior Management
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OP
Senior Management
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Posts: 28,067
Irving, TX
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I got some numbers for my new toy and was trying to figure out how to best get it down the track. 5200 lbs with driver. 5 speed auto. 1st: 3.587 2nd: 2.186 3rd: 1.405 4th: 1.0 5th: 0.831
26" rear tire. 2.65 rear gear.
Would you ride the HP plateau or reach farther back and grab a bucket load of that torque?
Unfortunately, it'll be a little while before I can try it out at the track.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: What RPM would you shift?
[Re: feets]
#3002640
01/06/22 04:26 PM
01/06/22 04:26 PM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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master
Joined: Sep 2014
Posts: 4,457
Washington
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If you want to go fast run the RPM up.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: What RPM would you shift?
[Re: madscientist]
#3002642
01/06/22 04:41 PM
01/06/22 04:41 PM
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Joined: Jan 2003
Posts: 13,357 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,357
Marion, South Carolina [><]
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CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: What RPM would you shift?
[Re: feets]
#3002649
01/06/22 05:12 PM
01/06/22 05:12 PM
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Joined: Aug 2011
Posts: 2,853 Pattison Texas
CSK
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master
Joined: Aug 2011
Posts: 2,853
Pattison Texas
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lots of TQ, is that with the EFI intake you showed me , same heads ? very good, that should move that heavy car
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: What RPM would you shift?
[Re: feets]
#3002681
01/06/22 06:28 PM
01/06/22 06:28 PM
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Joined: Jan 2003
Posts: 17,840 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,840
S.E. Michigan
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That must be the latest supercar (Mercedes, wasn't it?)
Rich H.
Esse Quam Videri
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Re: What RPM would you shift?
[Re: feets]
#3002707
01/06/22 08:25 PM
01/06/22 08:25 PM
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Joined: Aug 2003
Posts: 43,126 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,126
Bend,OR USA
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Take it to a 1/4-mile track and test shifting it at 4500, 5000, 5500 and 6000 RPM, then look at all the incremental numbers and decide what RPM worked the best If it went fastest shifting at 6000 RPM try 6300, and then 6600 RPM, you need to find out what the car likes for the best results
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: What RPM would you shift?
[Re: furious70]
#3002734
01/06/22 09:50 PM
01/06/22 09:50 PM
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Joined: Jan 2003
Posts: 28,067 Irving, TX
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OP
Senior Management
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Irving, TX
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9 GRAND AND DON'T LOOK BACK AMEN BROTHER! This is my Mercedes CL65. Bone stock. I'm changing the turbo bypass valves this weekend. That will allow us to tune the V12. The boost will be a bit higher and hold on longer. Most tunes add 100-110 torque and 60-70 hp. The torque will be hard to hold since it already lights the tires at 50 mph. However, it's the torque that makes the car so nice. 60-130 mph locked in 4th gear took 10.2 seconds. The best it has turned using second and third gears was 6.9 seconds. Not too shabby for an old pig boat. As for my 541 build, it's waiting on me to wire and plumb the EFI.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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Re: What RPM would you shift?
[Re: feets]
#3002795
01/07/22 06:54 AM
01/07/22 06:54 AM
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Joined: Nov 2020
Posts: 348 Isle of Sheeps
Gtxxjon
enthusiast
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enthusiast
Joined: Nov 2020
Posts: 348
Isle of Sheeps
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Most times at the track you ‘take it too the max’... You can feel the ‘drop-off’ if you go past peak power... Never found that ‘short shifting’ ever worked for me? Saves the engine but kills the ET, (phone home) lol...
Carpe diem, quam minimum credula postero, thanx Horace!
There’s no point trying to fix stuff that ain’t broke,,, 'but if ain’t broke',,, you is not trying hard enough...
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Re: What RPM would you shift?
[Re: feets]
#3003238
01/08/22 06:21 PM
01/08/22 06:21 PM
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Joined: Feb 2005
Posts: 4,311 Prospect, PA
BSB67
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master
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Posts: 4,311
Prospect, PA
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In theory, maximizing the hp under the hp curve should yeild the best et and mph. This theory works well with my cars, but I have a stock torque converter. I think this theory breaks down with higher stall race converters when the motor is back into the converter at the shift recovery rpm. The cam LSA and ICL probably play a part as well, and mine are not conventional..
Your shift/shift recovery rpm ratios are 0.61, 0.64, and 0.71 for 1-2, 2-3, 3-4 gear changes respectively.
With that, assuming you have a tight converter, I'm in the 5700-5800 camp at least for 1-2, and maybe 2-3. The 3-4 shift.might be 5400-5500. That's just eye-balling the graph and pushing the shift recovery hp up close to the shift hp.
This has played out pretty well on both motors I had in my charger with a torqeflite (0.59 and 0.69) . My 508 peak power was about 5600, but after a bunch of track testing, I shift 1-2 at 6500, and 2-3 at 6200.
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Re: What RPM would you shift?
[Re: TheOtherDodge]
#3003434
01/09/22 01:08 PM
01/09/22 01:08 PM
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Joined: Jan 2003
Posts: 28,067 Irving, TX
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OP
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Irving, TX
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I took it out for the last run of the 2021 Texas Muscle Car Club Challenge. It was an 1/8 mile whice is NOT where this thing belongs. I was surprised the Michelin PS4S hooked as well as they did. It had to be in the track prep. I left it in auto with sport on and ESP off. About 300 feet out it hazed he tires for a couple seconds. Naturally, it starts to feel good at the shift into third at 80 mph and speed builds rapidly but the 1/8 comes up quickly. I was lined up next to a Challenger 1320 on stickies. He sent me home by a tenth and a half but I felt good about having 2 mph on him. This thing is an awesome highway cruiser but it's short game is week.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
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