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possibility for strengthen the MT 6speed gearbox ( for TVS1900CC)

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have anyone tried to strengthen the MT 6speed transmission? just getting my tvs1900 chargecool and komotec gearbox cooler installed and will dyno tune next week, i understand with forged internal the engine is good up to 550-600 at crank, and the charger have ability to do that, the week point of the car will be transmission, BOE claim the gearbox is good up to 435whp wich is about 480hp~500hp at crank(about 500NM gearbox torque specs is 400NM) , guess that why Harrop only tune the car 480 as standard, ( they do offer more but the risk is on your own )
i been searching everywhere couldn`t find a single case , i don`t want to give up 6speed for sequential or pricey DCT, a manual 600hp lotus will be a dream to own
Edited by 34Vette
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6 hours ago, IanA said:

The EA60 manual 6spd transverse transmision (Aisin BG6) is good and strong with updates (around 2016). Aisin now rate it for 450 N-m torque. 

do u have refrence for that ?

i only know that it was only rated for 400NM 


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On 14/06/2021 at 07:54, IanA said:

Here is Aisin BG6 spec -(Toyota EA6X)


the gear ratio in the chart is not the one lotus put it in exige 

i guess is different verison of EA6X

lotus 3th gear  is 1.41 and 4th 1.090


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Yes ratios are different to the close ratios that Lotus put in.  There are about 6 different ratio sets/ diff pinion combinations for this box across a number of car makes using the EA6X box.

Lotus ratios are in second column but they replace 3,4-5 (common drive wheel) and,6. You will see that 1 and 2 ratios and the pair of final drive ratios are as per the Lotus box ratios.

Because the output gears are split over 2 output shafts (power-split), the gear wheel widths are substantial and the shafts cant flex. This is a very strong box and the only gear failures that I have heard of in out light cars (other than issues with the first batch of Lotus CR gears) is inadvertent miss-shifts from 5 down to 2 in track conditions. This can be avoided by allowing crossgate to centre momentarily before pulling into 4th.

A pic showing gears -


Edited by IanA
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MWR gears and shift forks are Toyota parts and Lotus CR parts. MWR offers oem Toyota forks with brass contact pads. Worthwhile changing the pads on your shift forks to the brass ones if you are rebuilding an EA60 box. SSC Aust have a brass shift fork pad kit to replace existing teflon ones on EA60 shift forks.

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  • 4 weeks later...

Well unfortunately someone else will have to push hard to break parts and find out. Altho by that time most will just go DCT.

I'm trying to get a built low comp long block by KT and they dont even have a lead time available 

Edited by DangerousDave
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