So i have been doing a little research on the topic of increaseing the diameter of the Rover Mini SPI throttle body. I have concluded that it is possible and that its quite a comman modification in Japan, they uprated the standard 41mm throttle body to 45mm.




My question is has anyone here attempted it and if so was there a noticably diffrence in power ?

This is the first i've heard of a bigger throttle body on an spi (though i do have an spi manifold thats been ported out to flow better)......its done on mpi's cause its easy and serves a benefit but on the spi's the throttle body isn't the power restrictor.
Realistically, the most power you would get from that modification alone would be about 1 hp, if you've already got extractors and exhaust, ported head, sports air filter and raised compression, then maybe it could work.

Specialised Components make an upgraded throttle body kit. It's one of the few places that do parts for spi engines

http://www.twinkam.co.uk/shop/article_S ... 218.001%26

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i offer this modification since years. not worth any HP if your engine is unter 85 - 90 HP. remember this TB was original fitted to Rover K series engines with up to 95HP before it found its way to the A series

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Rover 214 atm ....