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Fast, Reliable But Not So Cheap - 1380 BMW K1200 EFI
https://www.ausmini.com/forums/viewtopic.php?f=5&t=96193		 Page 1 of 11
Author:  jpodge [ Sat Oct 21, 2017 1:27 pm ]
Post subject:  Fast, Reliable But Not So Cheap - 1380 BMW K1200 EFI
I've learnt a lot since I first bought my 76 clubby when I was 17 and in my first year of my mechanical engineering degree. Fast forward 5 years and I've now got an engineering degree which is about the equivalent of 3 squares of toilet paper and I'm also looking to bring my mini into the 21st century. I'm after reliability mainly so EFI was a path I knew I was going to take. After months of thought and not wanting to do a complete engine swap requiring a full front end rebuild, a Twinky conversion kit complete with BMW K1200 head popped up on eBay and seemed to be a good way forward.

I bought the kit off Michael B in Sydney and I think he is part of the forum. Now that I am back home after being away for the best part of the year it's time to start swingin spanners in the garage.

I got in contact with Matt Read of course, and I'm going to start by saying Matt has answered all my questions no matter how stupid, he's prioritized his work well and never kept me waiting. Matt sorted out a 1275 block for me bored out to 74mm and had the block plugged and drilled ready to fit the new head. So even though the build hasn't even begun, thanks heaps, Matt. You're a champ.

Here it is now, note the mini waiting eagerly in the background. She's more than ready to swap out her tired 998 that has done her well for so long.

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The block is in great nic and Matt has done an even better job with converting it for the BMW head.
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Matt even threw in some pistons to suit! The box is pretty aged, but hey! It's got my initials on it so I think it's pretty cool!
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The head seems in really good nic too. Of course it'll need a refurb but it provides a fantastic starting point. Look at all those valvessssssssssssss
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The aim of the build is to get reliability and power. Triple figures of the HP variety is what I am aiming for but if it starts and drives well, doesn't cough or change with the weather, I'll be a happy man.

I have some standard 1275 conrods on the way. I am going to go for a lightened flywheel but I am unsure what to do about the crank. Will a standard crank do the trick or should I aim for a lightened crank? Is there much difference between a lightened crank and a standard one is I guess what I am asking.

Those of you that have followed other twinky builds on this forum would know that the original cam shaft still needs to be used to operate the oil pump. I have this small bore cam lying around that I've had for years. I think it's a peg drive variety. If I delobe it, is it suitable for the build?
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I think I'll use a basic Haltech ECU to run it all. All I think I need is a crank position sensor, throttle position sensor, suitable sized injectors and some sort of ignition system.

I'll log progress of the build here and I'd say hopefully around this time next year she will be on the road. Don't hold your breath, grab a cuppa and lets go.

Joe
Author:  timmy201 [ Sat Oct 21, 2017 2:11 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
That looks like a fun project!
Author:  winabbey [ Sat Oct 21, 2017 2:16 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Great background to your project. Thanks for posting. Looking forward to the trials and tribulations as work progresses. :)
Author:  jpodge [ Sat Oct 21, 2017 2:24 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
timmy201 wrote:
That looks like a fun project!


Thanks Timmy. The flywheel housing that I picked up from you a few months ago will come in handy for this project!
Author:  Besser [ Mon Oct 23, 2017 3:54 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Hey get a finance qualification and you can make your 3 squares Teflon coated!
Crank balancing would help and loose a couple of pounds in the process. Just remember that crossflow 4 valve head needs rpm (tumbler not swirler) to function well so will pass into a 3rd or 4th crank harmonic. Fit a windage barrier + scraper blade while it's apart to lighten the rotating load and a centre cap strap.
Author:  jpodge [ Mon Oct 23, 2017 8:32 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Besser wrote:
Hey get a finance qualification and you can make your 3 squares Teflon coated!
Crank balancing would help and loose a couple of pounds in the process. Just remember that crossflow 4 valve head needs rpm (tumbler not swirler) to function well so will pass into a 3rd or 4th crank harmonic. Fit a windage barrier + scraper blade while it's apart to lighten the rotating load and a centre cap strap.


With the addition of the centre strap the main cap will have to be machined flat. Once that happens, will I have to get it line bored? Matt had it line bored before it got to me so if I can avoid having it done again that'd be ideal but ya gotta do what ya gotta do. I assume it would need doing.
Author:  9YaTaH [ Tue Oct 24, 2017 6:37 am ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
jpodge wrote:

I think I'll use a basic Haltech ECU to run it all. All I think I need is a crank position sensor, throttle position sensor, suitable sized injectors and some sort of ignition system.

Joe


MadMatttheMiniMan is probably a good person to advise on appropriate injection, ignition etc :idea:
Author:  jpodge [ Wed Oct 25, 2017 8:19 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
I've had a chat with a few people, mechanic mates and family and with the Haltech I have plenty of options to consider for ignition systems to use. At this stage I think poaching a coil on plug setup from a yaris or something would be not only cheap but easy as to wire in to the Haltech. I had a quick look of their user guide which is incredibly straight forward and literally tells you where each wire needs to go.
http://www.haltech.com/files/downloads/ ... e%20V1.pdf

It's a fair way down the track at this stage though and there is plenty of other hurdles to get over with regards to actually building the engine. Is anyone on here running a Haltech on their mini?
Author:  jpodge [ Sat Oct 28, 2017 6:22 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Got some conrods in the mail the other day. They still had some pistons attached, and bloody hell did they need some convincing to get off.

This is how they showed up. Pistons were buggered but that didn't matter. A good clean for the rods was in order.
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I didn't think that the pins would be too hard to get out but that was because I'd never dealt with press fit pins. I've only ever encountered circlip style when I made that postie bike that some of you may have seen. ( http://www.ausmini.com/forums/viewtopic ... 10&t=94808 )

I'm happy with the state of the rods. Ideally I would've gone for forged rods to save the weight and get a really fast revving engine but hey, maybe if I had a better job or you know... won the lotto would I have gone with the swifttune or MED rods.

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Author:  drmini in aust [ Thu Nov 02, 2017 8:14 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Couple of points:
1. I would lighten those rods by milling 8mm off the cap lumps (edit) and lighten them as per Vizard's book. Fit ARP bolts.
Note, A+ rods are lighter.
2. I would not weaken the cast iron centre cap by milling it flat. When I built my 1412 stroker I cleaned the cap face up then made a stepped strap out of EN25 steel. I dimensioned it to have a .003" gap at each end. When torqued down, the bore was not out of round.
3. It is a big journal crank, they all have poor counterweighting. I recommend you get it wedged. This reduces uneven wear on the centre main journal.

Here's a pic of my 1412's wedged big journal stroker crank and the stepped EN25 centre main strap. The strap was made from an offcut I had, why it looks short but it's long enough. Rods are Cooper S, narrowed to fit the crank.
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Author:  9YaTaH [ Fri Nov 03, 2017 6:00 am ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
1. ,,,,and at the same time, get them weight matched and balanced...

Doc, I thought the jury was out on centre main strap? Something about, the cranks like to whip a little and by restricting that movement you risk breakage?? :D
Author:  drmini in aust [ Fri Nov 03, 2017 6:42 am ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
Centre strap is only really useful on race motors, the cap can break on overrun if you overrev the engine to a zillion RPM during downshifts.
As for cap flexing, on all except (maybe) S blocks it is grey cast iron. Doesn't flex, it cracks instead.
It would rather break than bend.
I put a strap on this stroker but have not used one since.
Author:  9YaTaH [ Fri Nov 03, 2017 8:42 am ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
drmini in aust wrote:
Centre strap is only really useful on race motors, the cap can break on overrun if you overrev the engine to a zillion RPM during downshifts.
As for cap flexing, on all except (maybe) S blocks it is grey cast iron. Doesn't flex, it cracks instead.
It would rather break than bend.
I put a strap on this stroker but have not used one since.


Cheers 8)
Author:  jpodge [ Fri Nov 03, 2017 7:15 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
drmini in aust wrote:
Couple of points:
1. I would lighten those rods by milling 8mm off the cap lumps (edit) and lighten them as per Vizard's book. Fit ARP bolts.
Note, A+ rods are lighter.
Image


Sounds good! New ARP bolts are a given but unsure if I'll go down the lightening route. Should I have just gone for the fancy forged rods? Just unsure on the mahcining costs for the lightening you mentioned^^

How far do we go with builds like this? Better is the enemy of good!
Author:  drmini in aust [ Fri Nov 03, 2017 8:44 pm ]
Post subject:  Re: Cheap, Fast, Reliable - Pick Two or Pick Twinky
I have machined those rod caps before on my mill, it's a quick job for any machine shop to take 8mm off.
Worth doing, even of you don't lighten the rod otherwise.
Also sand the ears off the little ends, and then balance the rods and caps to within 1g.
PM sent.

{edit] for clarity.
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