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DISCUSSION => Engine + Driveline => Topic started by: sh123 on November 12, 2015, 06:41:53 PM

Title: Big bore throttle bodys
Post by: sh123 on November 12, 2015, 06:41:53 PM

hi,

Ive been reading up a bit on big bore throttle bodys, people seem to get ok results from them, one guy claimed to get 12 bhp extra on hi supercharged m42 after a bbtb(big bore throttle body) was fitted. I would fit ITB's but due to rallying regulations I cant. so to help me a bit I was thinking maybe going for a bbtb.

my main question really is, is there a larger throttle body that will fit the m44/2 that comes standard on another bmw? m50? I know the m4x has two butterflys and the bolt patter is rectangular shape but so is the m50 but has only one large butterfly?

maybe i should try and find a cheap one on ebay. but I havent got my tb or manifold to try and match at the moment.

Title: Re: Big bore throttle bodys
Post by: MoMansi on December 10, 2015, 02:05:13 PM

actually, the M44 and the M42 share the same throttle design and measurements but:

you can bore out the second plate to 57mm from 54mm, this will make a difference you will feel, leave the small one as is, and no need to retune or anything , the DME will read the changes!

Cheers

Title: Re: Big bore throttle bodys
Post by: sh123 on December 10, 2015, 02:53:00 PM

hi MoMansi,

Thanks for the reply. ive found companys here in the uk who can do it.

but since i posted this topic. I seem to have aquired a new shell so my build may take a different direction in the future.

cheers though
Sion

Title: Re: Big bore throttle bodys
Post by: bmwman91 on December 11, 2015, 01:06:56 AM

You will want to be careful boring it out. Going too big will hurt air velocity and while it will be good for high RPM power, it will cost you some low/mid RPM power (which the M42 already lacks). For the record, I am doing just fine with a stock TB on my strung-out 2.1L M42.

Title: Re: Big bore throttle bodys
Post by: sh123 on December 11, 2015, 05:42:51 AM

Quote from: bmwman91 on December 11, 2015, 01:06:56 AM

You will want to be careful boring it out. Going too big will hurt air velocity and while it will be good for high RPM power, it will cost you some low/mid RPM power (which the M42 already lacks). For the record, I am doing just fine with a stock TB on my strung-out 2.1L M42.

Ill leave it standard for now but need to decide if i go down itbs, s14 or s54 route