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Final Drive Ratio For 1330 Mpi 5 Speed?


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#1 cartneil

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Posted 13 September 2021 - 07:17 PM

Hi everyone,

 

just after a bit of advice regarding which final drive ratio to chose for my set up. I have searched to check topics for answers, but they are usually for 4 speed gearboxes, where as mine is a 5 speed.

My full spec is - 

1330 mpi block

Specialist Components supersports head

SW5 cam

Specialist Components stainless exhaust

Specialist Components typhoon ECU

1.5 roller rockers

Minispares helical 5 speed close ratio gearbox X-pin diff

 

The conundrum is do I go for 3.6 FD ratio, as I have 5th gear as an overdrive, so will be equivalent to just under 3.2 in 5th.

The worry is I will be lighting the tyres up everytime I pull off with some welly, plus will I run out of legs quickly with a  3.6 close ratio. Plus equivalent 3.2 FD ratio - engine still revving quite high at 60mph?

Or do I go for 3.44 for more all round use? (in 5th that gives about 3.0 FD)

Also, the SW5 cam should be pulling well from quite low down, so won't need a 3.6?

 

It isn't a track car and won't be used every day, just for weekend country roads blasts, though do want to be able to cruise without the engine screaming (yes, even in 5th!)

 

Any advice/experience gladly recieved!!

Neil



#2 Magneto

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Posted 14 September 2021 - 03:06 AM

I think you're on the right track with the 3:44 final drive. I have a 3.0 in my car and in 4th I'm turning 3800@ just over 70mph on the highway....that's a good combination of power band and not running too many RPM on the highway.



#3 cartneil

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Posted 14 September 2021 - 06:29 AM

I think you're on the right track with the 3:44 final drive. I have a 3.0 in my car and in 4th I'm turning 3800@ just over 70mph on the highway....that's a good combination of power band and not running too many RPM on the highway.

 

Great, thanks for your reply!!



#4 Honda-Mini

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Posted 09 October 2021 - 11:53 AM

i have an MPi with the same box and a 3.44 diff... ive always thought it could stand a little taller diff so with your spec i reckon you could get away with the next one up... dont forget the original diff was a 2.76

 

have you tried guessworks gear ratio calculator? http://www.guess-wor.../Tech/ratio.htm






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