Posted By: feets
What RPM would you shift? - 01/06/22 08:21 PM
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.
Posted By: madscientist
Re: What RPM would you shift? - 01/06/22 08:26 PM
If you want to go fast run the RPM up.
Posted By: CSK
Re: What RPM would you shift? - 01/06/22 09:12 PM
lots of TQ, is that with the EFI intake you showed me , same heads ? very good, that should move that heavy car
Posted By: fast68plymouth
Re: What RPM would you shift? - 01/06/22 09:23 PM
Really nice numbers for “at the wheels”
Posted By: Stanton
Re: What RPM would you shift? - 01/06/22 10:22 PM
Seems to me you'd want to launch at around 3k and shift at whatever rpm to be at 3k at the bottom of each shift. Then run it out at the top end.
Posted By: ZIPPY
Re: What RPM would you shift? - 01/06/22 10:28 PM
That must be the latest supercar (Mercedes, wasn't it?)
Posted By: A727Tflite
Re: What RPM would you shift? - 01/07/22 12:24 AM
Run a shift loop at the track when you get there.
Start 500 below max power, and increase you shift points by 2 or 3 hundred until the car falls off for ET and MPH.
Then change your stall speeds on the line the same way until you get your best 60’.
Posted By: Cab_Burge
Re: What RPM would you shift? - 01/07/22 12:25 AM
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
Posted By: furious70
Re: What RPM would you shift? - 01/07/22 01:02 AM
9 GRAND AND DON'T LOOK BACK
Posted By: feets
Re: What RPM would you shift? - 01/07/22 01:50 AM
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.
Posted By: Gtxxjon
Re: What RPM would you shift? - 01/07/22 10:54 AM
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...
Posted By: TheOtherDodge
Re: What RPM would you shift? - 01/08/22 01:55 AM
Feets, leave it in drive... I had a E55 with a "level 1 tune" and went 11.80 with a "spinning 60ft". I have never heard, though I am sure it happens, where a driver controls the shifts on these cars and runs better than if they left it in drive. Just my .02. And for fun, with a tune, I estimate it to run in the mid 11's if you are on a decent tire.
Posted By: BSB67
Re: What RPM would you shift? - 01/08/22 10:21 PM
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.
.
Posted By: feets
Re: What RPM would you shift? - 01/09/22 05:08 PM
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.
Posted By: moparx
Re: What RPM would you shift? - 01/09/22 08:01 PM
boy, a tenth and a half ain't very much in the grand scheme of things.
you should be able to easily figure that out with not much practice.
pretty good outing i would say.