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Supra specific gear/diff ratio and tyre size calculator


Homer
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I've put together an Excel file which shows the effect of fitting various sized diff and gearboxes to the supra, it also contains a graphical chart showing the effect different tyre & wheel sizes and offsets effect both fitment to the hub and the effect on speed/acceleration. There are two main sheets on the file, Wheel size fitment and gear ratio calculator.

 

Before it goes to the tech reference section, can some of you please review it and see if there are any errors or faults?

 

Also, any suggestions for enhancement are welcome :)

 

It took a silly amount of time to research the data and put this together, so hope it's going to be useful to someone :D

 

Edit - updated with "final" version..

Supra Gear & wheel size Calculations.xls

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That is great. Just noticed that top speed is always calculated at stock red line not desired speed, unless I am doing something wrong.

 

Thanks for all your hard work, it is always much appreciated.

 

The gear/diff calculator really shows the impact of sticking an auto diff on the V160 box

Edited by Terminator (see edit history)
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Nice one homer you must have some amount of spare time on your hands

 

lol, I have no spare time at all, that's why it took 6-8 weeks to finally get the thing together :D

 

That is great. Just noticed that top speed is always calculated at stock red line not desired speed, unless I am doing something wrong.

 

Thanks for the feedback Phil

 

The top speed is indeed based on stock rev limit. If you need to find a the gear speeds at any specific rpm it can be entered in the "desired rpm" cell which will deliver the top speed in each gear at that maximum rpm. I will look into changing the top speed calc if a value is entered in that cell :)

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Thanks for putting this together it's pretty nifty :) Does the facelift 6spd definitely have the same final drive as the tt auto? No point in me swapping diffs if so.

 

According to all the info so far the facelift 6spd appears to have the same "smaller" diff as the auto. If you don't mind, would you be able to PM your VIN code details (chassis, model and diff code) so I can check on EPC to make sure it matches up with everything so far? Getting all the diff info summerised has been a nightmare!

 

EDIT - Rick, did you see the last revision of the file or the first one? I updated the ratio's just after posting for the facelift 6spd based on some further info from Nic. Sorry for the confusion!

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According to all the info so far the facelift 6spd appears to have the same "smaller" diff as the auto. If you don't mind, would you be able to PM your VIN code details (chassis, model and diff code) so I can check on EPC to make sure it matches up with everything so far? Getting all the diff info summerised has been a nightmare!

 

Yeh sure i'll just nip out and check. Will PM you in a sec.

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Works for me, maybe you could add the Desired Top Speed in a second window to appease Termi?

 

Or Termi edit the red numbers' field and replace the J11, J12 and J13 in the formula with N11, N12 and N13?

 

See attached.

 

attachment.php?attachmentid=91861&d=1241164739

Image1.jpg

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Idea's for enhancements, use dropdowns for the various options where appropriate, I can do that for you & send you the sheet back if you wish Darryl

 

Yep I agree that would help. I'd say go for it and post up a new copy :)

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Brilliant Darryl :)

 

If you're J-spec auto you could reach 60MPH in 1st with an 8,500 RPM rev limit :D

 

Or with a UK manual diff it'd only take 7k RPM and make it a ~230 MPH car, horespower permitting...

 

If I keep my diff and put a v161 in for track work, it drops the top speed from ~192 MPH to ~165 MPH (~171 MPH with a v160) - sounds perfect for the job given there's not many tracks where you're gonna get a chance to get up there but you will benefit from the improved acceleration.

 

(All with 265/35/18's)

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Darryl FYI:

 

I have created a new data sheet for the list info, I have given each list a name (you can see the name when you select the list contents where Excel would normally tell you which cell you are in). The lists are in alphabetical order (they need to be I think for LOOKUP to work correctly)

 

I used the Tools... Data Validation menu on the Gear sheet to refer to these lists by name.

 

I created 2 cells behind the graphs which lookup the names to their proper values (the values you had to type into the original sheet).

 

I modified all cells to refer to these now rather than the dropdown boxes :)

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Would this explain why my trap speeds at pod were 10mph out and I was bouncing off my limiter in 4th?

 

I have a pre facelift 1996 RZ-S with the larger diff casing, not sure what ratio that should be :search:

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