Rolling Pulls - Starting Points

[Eatonian49]

So finally past the break in period and I want to hear if anyone has found a good starting gear/rpm on the manual for rolling pulls?

I'm thinking 3rd gear, 40 mph, around 3-4k rpm? 3.73 gearing.

My BIL is going to ask to roll race him someday and I want to be prepared haha.

Racing to the speed limit.....of course....

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[Idaho2018GTPremium]

3000 rpm is definitely too low to start a roll. 4500-5000 rpm is a solid starting point so whatever gear equates to that rpm range at the given speed. I don't remember the speeds for given gears at those rpms but you can figure it out pretty easily looking at your gauges.

 

[murick]

I'm thinking 3rd gear, 40 mph, around 3-4k rpm? 3.55 gearing.

Which car are you talking about? US Mach 1 with Tremec has 3.73 diff gearing. EU Mach 1 has 3.55 diff.

 

[LxMike]

Second gear….

 

[Eatonian49]

Which car are you talking about? US Mach 1 with Tremec has 3.73 diff gearing. EU Mach 1 has 3.55 diff.

Ah yes you're right, sorry about that. For some reason I thought 3.55 was standard. Ill edit that.

 

[murick]

Ah yes you're right, sorry about that. For some reason I thought 3.55 was standard. Ill edit that.

There is a site where you can produce nice graphs of the gear shift/RPM/speed for particular transmission, diff gearings and tyre diameter (https://legacypic.uk/transmission/graph.php).
I happen to have one for US Mach 1 with HP at hand, so here it goes

 

[Eatonian49]

There is a site where you can produce nice graphs of the gear shift/RPM/speed for particular transmission, diff gearings and tyre diameter (https://legacypic.uk/transmission/graph.php).
I happen to have one for US Mach 1 with HP at hand, so here it goes

Oh that's super helpful. Thank you!

So looks like @40mph 2nd gear 4.5k-5k or @60 mph 3rd gear 4.5k-5k seems like good starting points.

 

[murick]

Oh that's super helpful. Thank you!

So looks like @40mph 2nd gear 4.5k-5k or @60 mph 3rd gear 4.5k-5k seems like good starting points.

I have no idea how rolling-pulls work , but from purely scientific point of view, since the Coyote max torque (in Mach 1) is rated @ ~4900 RPM, your best bet would be to start around that RPM to get max. acceleration right at the start. 4.5k-5k looks like a good range.

 

[EFI]

You want to be in the 5000+ rpm range for a start, especially if you have the Tremec and it's longer gears.

 

[murick]

You want to be in the 5000+ rpm range for a start, especially if you have the Tremec and it's longer gears.

Against which gearbox has Tremec longer gears?

Starting at RPM higher than your max torque does not make sense (from theoretical point of view) for two reasons:
1) starting at the higher RPM means sooner you would incur a shift = less time to transfer the power down in the beginning without an interruption.
2) starting at the RPM past you max torque prevents you to max the acceleration.

Now these are "academic" reasons. I wonder what are the reasons to do it this way anyway?

 

[Eatonian49]

Your point 1 is what I was considering the most. If you're at 5k+ you're gonna have to shift almost immediately. But since it is at the best point for torque it may not matter?

 

[murick]

Your point 1 is what I was considering the most. If you're at 5k+ you're gonna have to shift almost immediately. But since it is at the best point for torque it may not matter?

If the rolling race has a set starting speed (e.g. 40 or 60 mph) you could only be choosing the gear as the RPM will be given anyway. And looking at the graph i posted earlier, there are not really many choices, 2nd for 40 and 3rd for 60. The debate we are having is good for understanding how to adapt, if the parameters (starting speed) change.

 

[Eatonian49]

If the rolling race has a set starting speed (e.g. 40 or 60 mph) you could only be choosing the gear as the RPM will be given anyway. And looking at the graph i posted earlier, there are not really many choices, 2nd for 40 and 3rd for 60. The debate we are having is good for understanding how to adapt, if the parameters (starting speed) change.

Yeah I understand. Trying to understand the nuances is what I wanted to llook into.

 

[EFI]

Against which gearbox has Tremec longer gears?

Against the 10R80.

1) starting at the higher RPM means sooner you would incur a shift = less time to transfer the power down in the beginning without an interruption.

Possibly, but by that logic you should start your roll at 2000rpm in 6th gear. Saves you 3 shifts right?

2) starting at the RPM past you max torque prevents you to max the acceleration.

Not sure if that's how it works, but then again I don't really have any factual data on that. There's still more power to be had at 5000rpm than 4200rpm where max torque is achieved.

 

[murick]

Possibly, but by that logic you should start your roll at 2000rpm in 6th gear. Saves you 3 shifts right?

You would get much less torque (= acceleration) to the tarmac at that RPM x gear. The compromise (or the optimal) should be between the lowest gear possible, while not being "too low" as to cut the optimal torque range.

Not sure if that's how it works, but then again I don't really have any factual data on that. There's still more power to be had at 5000rpm than 4200rpm where max torque is achieved.

Now you mention the RPM at max torque, it is interesting. The EU Mach 1 (and possibly any export Mach 1 with reduced HP) is tuned for having max torque @ 4900 RPM. It is in the tech. spec, there is even a graph from Ford showing that ( 2021 Ford Mustang Mach1 Tech Spec EU ).

However when looking at the US spec, it does not show the max. torque RPM for Mach 1 ( 2021 Mustang Tech Specs ). The user manual supplement says it is 4600 RPM. But when looking at some graphs posted by @joepro here (https://www.mustang6g.com/forums/th...having-less-hp-and-torque.179646/post-3624364), we can see that at wheels the max torque is at ~5000 RPM while 4-6k range is more or less symmetrical and quite stable.

Since the OP is probably more interested in torque on wheels than on the engine this seems to me as a good range to go by.

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