steve spedd Posted September 30, 2016 Share Posted September 30, 2016 (edited) Evening all, I don't post on here much and keep my build quiet. Well I've just had my Soop mapped and it's running really strong. I've been NA-t since 2007 but changed parts recently and re-built the engine totally. Running the R154 @.08/0.9 bar 500hp and 400lb torque. Problem I have now is that before you know it I'm in 5th gear nearly at the red line. Presume with a different diff this would be better (better Cruzing revs and higher top speed) Does anyone have any suggestions? Please... Edited September 30, 2016 by steve spedd (see edit history) Quote Link to comment Share on other sites More sharing options...
David P Posted September 30, 2016 Share Posted September 30, 2016 Here you go. http://www.mkivsupra.net/vbb/showthread.php?225050-Supra-specific-gear-diff-ratio-and-tyre-size-calculator Quote Link to comment Share on other sites More sharing options...
Noz Posted October 1, 2016 Share Posted October 1, 2016 The auto TT diff will bring down the ratio per rpm. It'll give you longer drives, though it'll affect all the other gears and therefore cause a bit of lag to get there. Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 3, 2016 Author Share Posted October 3, 2016 Yeah that's what I'm thinking. Need to find one if those now... Quote Link to comment Share on other sites More sharing options...
David P Posted October 6, 2016 Share Posted October 6, 2016 Have you checked out the link to Homer's calculator? You could achieve the same by simply increasing the tyre width and or aspect ratio and for a free bonus, get better traction too. Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 6, 2016 Author Share Posted October 6, 2016 Hi David, Yes I have looked, really useful and I can get a little more but not much. It's more the cruising speed/RPM i'd like to reduce rather than the top end. With the current setup @ 70mph in 5th the revs are 3000 and I think that's a little high. Just think the car is revving too much? with the set up and the A02B @ 3000rpm i'd be doing 80mph or am I worrying about nothing? I was also concerned how much power the NA diff can hold and for how long... thoughts welcome. Quote Link to comment Share on other sites More sharing options...
berg Posted October 6, 2016 Share Posted October 6, 2016 Exact reason ive just put an a02b on my car with the r154 It was annoying on the motorway with the a01b Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 6, 2016 Author Share Posted October 6, 2016 Yep that's the one! much better I presume? Struggling to find an A02B diff. Think Jamie has killed them all! Still hunting for one... Quote Link to comment Share on other sites More sharing options...
David P Posted October 6, 2016 Share Posted October 6, 2016 (edited) Hi David, Yes I have looked, really useful and I can get a little more but not much. It's more the cruising speed/RPM i'd like to reduce rather than the top end. With the current setup @ 70mph in 5th the revs are 3000 and I think that's a little high. Just think the car is revving too much? with the set up and the A02B @ 3000rpm i'd be doing 80mph or am I worrying about nothing? I was also concerned how much power the NA diff can hold and for how long... thoughts welcome. The A01A & B are same strength as A02A & B. What are your present wheel and tyre sizes? Edited October 6, 2016 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 6, 2016 Author Share Posted October 6, 2016 Rota Force Drift: 9x18 ET35 front and 10.5x18" ET40 Fronts: 235/40 Rear: 265/35 Quote Link to comment Share on other sites More sharing options...
David P Posted October 6, 2016 Share Posted October 6, 2016 (edited) It's more the cruising speed/RPM i'd like to reduce rather than the top end. Laws of physics dictate that these are joined at the hip. Your present (theoretical) top speed is 166mph at 6,800rpm. (5th gear 3k rpm = 73.4mph) (70mph @ 2861rpm) Swapping your 4.083 for a 3.769, would give you a (theoretical) top speed of 180mph at 6.800rpm. (5th gear 3k rpm = 79.5mph) (70mph @ 2641rpm) Alternatively, swapping your 265 35 tyres for 295 40's, would give you a (theoretical) top speed of 179mph at 6,800rpm. (5th gear 3k rpm = 79.2mph) (70mph @ 2651rpm) Either of these ratio's would be a good match for your power level and demonstrates there's more than one way to skin this cat. The same difference can clearly be seen and the tyre swap option results with better traction, better handling and better ride comfort from spending less money doing an easier job, it looks cool too. I have tried it both ways and can assure you that changing the tyres is the better choice. Here's a pic of mine running Hybrid auto transmission, 4.083 A01B diff, 18x10 ET45 wheels 285x40 tyres, (theoretical) top speed of 189mph at 6,800rpm. If I'm ever silly enough to try and get into the 200mph club, I could fit 285 45's and raise the rev limit to 7,000rpm for a (theoretical) top speed of 203mph. Edited October 7, 2016 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 6, 2016 Author Share Posted October 6, 2016 thanks David, so do you think I should still try and find an A02B? they appear to be like Rocking horse sh*t... Quote Link to comment Share on other sites More sharing options...
David P Posted October 6, 2016 Share Posted October 6, 2016 thanks David, so do you think I should still try and find an A02B? they appear to be like Rocking horse sh*t... You can lead a horse to water................ Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 8, 2016 Share Posted October 8, 2016 thanks David, so do you think I should still try and find an A02B? they appear to be like Rocking horse sh*t... Yes, he was just lying / drunk / fooling about when he made this statement: "I have tried it both ways and can assure you that changing the tyres is the better choice." Quote Link to comment Share on other sites More sharing options...
David P Posted October 10, 2016 Share Posted October 10, 2016 Invisible ink, a useless telephone app or too much information to sink in? Quote Link to comment Share on other sites More sharing options...
steve spedd Posted October 11, 2016 Author Share Posted October 11, 2016 not sure if that was for me or not? think I may have sorted this so thank you for all your help Quote Link to comment Share on other sites More sharing options...
David P Posted October 12, 2016 Share Posted October 12, 2016 (edited) Before you fit that A02B, or I flog an old wives horse to death? Do yourself a favour and stick on a pair of pre-loved 295 40's and give yourself the opportunity to experience the way easier, far cheaper and much better option. After you have toasted the tyres, should you then fit the A02B you could find out the expensive way that it will then cost a lot more money to convert back to the preferable and formerly cheaper option. There's a decent pair here with 6mm tread for £135 including free fitting not far from you. http://www.ebay.co.uk/itm/2X-PART-WORN-TYRES-CONTINENTAL-CROSS-CONTACT-295-40-20-110Y-XL-6MM-FREE-FITTING-/112156518057?hash=item1a1d0ca6a9:g:QJ8AAOSwYIxX8neg You may need to roll or trim the top of arch lip to clear? Edited October 12, 2016 by David P (see edit history) Quote Link to comment Share on other sites More sharing options...
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