[DeTomaso] Steel vs aluminum flywheel

[Corey Price]

Dan,

BTW and not to hijack this topic, but RBT Transmissions website has a gear and RPM calculator...  It's helpful to me and has preset ratio buttons for Panteras, GT40's, M1's, etc.

Corey




On Feb 8, 2012, at 11:23 AM, Daniel C Jones <daniel.c.jones2 at gmail.com> wrote:

>> when I ran a Dynomation simulation, my motor would have twice the torque
>> at 1,000 RPM of a normally aspirated engine with a big cam and carb due
>> to the cam the turbos like, so I think either flywheel will work well on
>> the street.
> 
> Dynomation is quite optimistic at low RPM (below peak torque).  Also,
> the value it returns assumes WOT and tuning is largely irrelevant at
> part throttle, so the difference in WOT torque is not important.  More
> important will be the mild cam timing associated with the turbo engine.
> Assuming your first gear remains a 2.23:1 and you are moving from a
> 4.22:1 to 3.2:1 final drive ratio, a vehicle weighing 3200 lbs will
> now appear as if it weighs 4220 lbs when starting from a stop.  I've
> calculated and posted the numbers for the effect of reducing flywheel
> inertia before.  The effect is quite large in lower gears where you will
> be traction limited and negligible in higher gears so I'd go for the steel
> flywheel.
> 
> The T5 in my '87 Mustang GT has a 1st gear ratio of 3.35:1 and a 2nd gear
> ratio of 1.93:1.  It also has a final drive ratio of 3.08:1 which means
> the combined gear ratio in first is 10.318:1 and is 5.9444 in 2nd gear.
> With a 2.23:1 first gear and 3.2:1 final drive ratio, you will have a
> combined gear ratio of 7.136.  If my Mustang had the popular 3.55:1
> final drive ratio, starting off in 2nd gear would be equivalent to
> your Pantera starting off in 1st gear.  I wouldn't want that at all and
> certainly not with a lighter flywheel.
> 
> I think you'd be happier with a 3.56:1 or 3.77:1 final drive ratio combined
> with a shorter 2.86:1 second gear and taller 0.62:1 5th gear.  I think Kirk
> may have a 3.56:1 ring and pinion on hand.  When we discovered the corrosion
> problems in my red Pantera's ZF, I wrote a program to help me evaluate
> various gear ratio combinations.  It figures out the RPM the engine falls
> back to at each shift, assuming instantaneous shifts and no tire growth.
> Results for a few combinations I ran are below:
> 
> Dash 2 ZF with 4.22:1 final drive ratio, 0.705:1 5th gear, 335/35/17 tires
> Shifting at 6500 RPM
> Shifting from 1st to 2nd, Fall Back Engine RPM = 4284.8 at  53.9 MPH
> Shifting from 2nd to 3rd, Fall Back Engine RPM = 4598.6 at  81.8 MPH
> Shifting from 3rd to 4th, Fall Back Engine RPM = 5287.5 at 115.6 MPH
> Shifting from 4th to 5th, Fall Back Engine RPM = 5416.7 at 142.1 MPH
> Cruise Speed of 80 MPH is 3050 RPM
> 
> Dash 2 ZF with 4.22:1 final drive ratio, 0.62:1 5th gear, 335/35/17 tires
> Shifting at 6500 RPM
> Shifting from 1st to 2nd, Fall Back Engine RPM = 4284.8 at  53.9 MPH
> Shifting from 2nd to 3rd, Fall Back Engine RPM = 4598.6 at  81.8 MPH
> Shifting from 3rd to 4th, Fall Back Engine RPM = 5287.5 at 115.6 MPH
> Shifting from 4th to 5th, Fall Back Engine RPM = 4763.6 at 142.1 MPH
> Cruise Speed of 80 MPH is 2682 RPM
> 
> Dash 2 ZF with 3.56:1 FDR, 2.86:1 1st gear, 1.72:1 2nd gear and 335/35/17 tires
> Shifting at 6500 RPM
> Shifting from 1st to 2nd, Fall Back Engine RPM = 3909.1 at  49.8 MPH
> Shifting from 2nd to 3rd, Fall Back Engine RPM = 3930.2 at  82.8 MPH
> Shifting from 3rd to 4th, Fall Back Engine RPM = 5287.5 at 137.0 MPH
> Shifting from 4th to 5th, Fall Back Engine RPM = 5416.7 at 168.4 MPH
> Cruise Speed of 80 MPH is 2573 RPM
> 
> In addition to 0.62:1, I believe there are 0.642:1 and 0.655:1 5th
> gears available to replace the ZF 0.705:1 5th gear.
> 
> Dan Jones
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