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BMW twincam conversion engine build questions
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Author:  Kennomini [ Sat Aug 20, 2011 6:13 pm ]
Post subject:  BMW twincam conversion engine build questions

Ok I recently got my hands on a 11/83 BMW K100 8valve engine. After pulling the head off I played around with the block and had a brain spark....the BMW is a "boxer" type engine (basically cylinder 1 & 4 are both at TDC at the same time and cylinder 2 & 3 are at Bottom Dead Center). I then remembered Swift tune in the UK now make the came crank for the mini http://www.swiftune.com/Product/972/swi ... n-set.aspx
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Now I know this is an expensive option at 3199 pounds :shock: but it dose come with brand new special rods and pistons.
So a couple of questions;
Is their a major advantage in this design compared to the normal type of crank :?:
Is this design really worth the money considering it's what the BMW has :?:
IMO the twinky should run and perform better with this new crank but will it really :?:

Author:  TheMiniMan [ Sat Aug 20, 2011 7:03 pm ]
Post subject: 

Kenno,,, the mini already has 2 pistons up while the other 2 are down,,, the difference with that swifttne crank (& many other similar cranks) is that the counterbalancing is far better

that`s all

the "Boxer" engines are horizontally opposed,,, like early R80 Bimmer bike engines,,,, the Vee-dub donk & the Subaru WRX engine

but yes it`s a nice crank

& yes it will be smoother

Author:  Kennomini [ Sat Aug 20, 2011 11:38 pm ]
Post subject: 

TheMiniMan wrote:
the "Boxer" engines are horizontally opposed,,, like early R80 Bimmer bike engines,,,, the Vee-dub donk & the Subaru WRX engine

Yeah I was thinking about it after I posted and realized my mistake their :oops: .
Do you reckon it's really worth the price for the gain?

Author:  mini_mad_matt [ Sun Aug 21, 2011 12:55 am ]
Post subject: 

That all depends on how much all that money is worth to you. For me personally, no way is that money worth it. For someone that goes to sleep on a pile of cash then yea sure go for it.

But i'm sure lots of people will tell you a standard crank works just fine, but yes that crank would most likely be better.

Author:  Gareth_1330 [ Sun Aug 21, 2011 8:57 am ]
Post subject: 

Someone told me once that when modifying cars you spend 20% of the money getting the first 80% in gains, and the remaining 80% getting the last 20% gains.

I think this crank represents spending 95% to get a 5% gain.

Ask pristic, to go very fast all you need is a 1100 and a turbocharger. No need for BMW heads, trick cranks etc etc

Author:  Gareth_1330 [ Sun Aug 21, 2011 8:59 am ]
Post subject: 

and as for the cams and timing, firing order 1432 becomes 1342, changing two leads around is much cheaper.

Author:  TheMiniMan [ Sun Aug 21, 2011 11:45 am ]
Post subject: 

one of the beautys & major benefits of the Bimmer Twinky is it`s smooth-ness,,, the power delivery is just sooo sooo sweeeet... it`s effortless & niffty & responsive & it`s ability to produce a nice quiet smooth beautiful power curve is just the thing

the fact that they also produce a far greater quantity of that beautiful power is just a bonus

these new-cranks are similar ,,, where the "smoothness" of the engine is improved via the better counterbalancing ,,, & also "should" (i believe) have an extended life span compared to a std 40 year old fatigued mini crank

so yeah i like them,,, but yeah they`re expensive

& yes the twinkys design allows for the leads to be swapped around & can run on the mini engine in reverse direction, because the cams are "Concentrically" ground ,,, IE--> same opening ramp as the closing ramp.... (yes the Bimmer bike engines run anticlockwise & when we put the bike cyl head onto the mini motor we run them clockwise) so no need to change cams for the conversion

but again , having a pair of cams made to suit would be optimum if you had the money to spend,,, just like that special crank,,, & the turbo,,, & the sequential injection & the etc,,,,

if you have the money & you want the nice stuff that works well,,, then why not?... once you`ve driven a turbo injected twin cam mini , you will realize just how sweet they really are ,,,, it`s simply a far higher level of sophistication

Author:  NG [ Sun Aug 21, 2011 12:10 pm ]
Post subject: 

if it was me i would go

http://www.twinkam.co.uk/shop/article_S ... CK002.A%26

crank & rods

Author:  junior [ Wed Aug 24, 2011 5:20 pm ]
Post subject: 

matt
have you had a twinky running with the K injection using the computer from the bike?

Author:  Kennomini [ Wed Aug 24, 2011 5:57 pm ]
Post subject: 

NG wrote:
if it was me i would go

http://www.twinkam.co.uk/shop/article_S ... CK002.A%26

crank & rods

Yep that's way cheaper but not available to buy now :? .
I'll probably just end up running the standard crank but it would be nice to have one of these cams :roll: .

Author:  NG [ Sat Aug 27, 2011 6:57 pm ]
Post subject: 

yeh they sold out.

more being made you can put your name down it is a few weeks wait.

Author:  TheMiniMan [ Sat Aug 27, 2011 10:07 pm ]
Post subject: 

junior wrote:
matt
have you had a twinky running with the K injection using the computer from the bike?


Nah, just went straight for the after-market sequential job

the 8v computer is very old agricultural thing using the crappy "Trap-door" type air-flow meter & a simple "on-off" TPS,,, but the 16v computer may well be worth a go, it has a true "potentiometer TPS (Volume/Reostat type switch) & not a bad looking set-up really,,, i havn`t bothered with it either tho because aftermarket stuff is so good these days,,, also very good value for money,,, & we can easily & simply have a little "Play" to make it suit whatever engine configuration we want.... Oh & also Forced induction-able

Author:  poida97 [ Tue Aug 30, 2011 8:35 am ]
Post subject: 

I think Graham Russell also makes eight-counterweight cranks... GR, how do yours compare (both performance and pricing-wise)?
I'd love one of these for my K1200RS conversion, I figure that the better balancing would be a big help at the revs that the head likes. Obviously 3200UKP is not an option (well not a sensible option anyway). The fancy pistons and rods offset that price a bit but it still seems way too much to me.
AV

Author:  drmini in aust [ Tue Aug 30, 2011 10:54 am ]
Post subject: 

I think GR's 8 counterweight cranks (made in Melbourne) were around $4K.
But then you'd want some nice H beam rods to go with it... 8)

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