K100 Small Bore - To Turbocharge or not?
Turbo Mini Forums

Fuck me - I've been trying to figure out who Paul S is and why he's just appeared and knows shit loads about stuff that newbies shouldn't.

Then i noticed:

Paul S
1436 Posts
Member #: 573

Formerly Axel

Northants





duuuuuuurrrrrrr!

lol it got me too for a bit.

I thought it was about time I stopped using my middle lads nickname.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

cool !!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

just had a thought,

would it be easier to ofset bush the small ends to bring the piston down the bore?

could also gain a bit on the bigend if you machine the rod and re bore it.

It looks like the later 850 cranks use the same centre bearings and thrust washers as the 998, so it may be just a matter of accumulating the right parts.

I'm not worried about losing a few CCs and it's easier than machining rods to shorten them.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Just replied to this thread:

http://www.turbominis.co.uk/forums/index.p...7917&lastpost=1

Well, I am now the proud owner of a complete 850 engine and box.

So I just need to find the time to strip it down and find which bits are interchangeable.

I'll have to use the 850 crank, but not sure about the block.

The 850 block will allow more offset of the bore to match the head, but maybe not as strong as the 998 A+ block.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Just got a quote from Kent Cams to regrind the cams at a shorter duration for £196.00 plus VAT.

Looks like this might just work.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Might be worth having a word with Kent to see how much they knock off if they were to do two pairs of cams.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i shure you are all aware of these guys..

seem to use the stock cams

http://www.rbracing-rsr.com/bmwturbos.htm

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I've shot myself in the foot!

I want to keep the compression ratio high to make best use of the aluminium head and good engine management.

Just done the compression ratio calcs and with the 850 crank, I still need the pistons at the top of the bore to get 9.5 to 10:1 compression ratio.

Bugger, the main reason for the 850 crank was to get the pistons down the bore to avoid the valve cut-outs.

So the valve cut-out problem has not gone away, unless I get the cams re-profiled at the cost of £196 plus VAT.

If I get the cams re-profiled I might just as well use the 998 with a slight dish in the pistons.

So, whats it to be?

1. 952cc, 10psi, 152hp, 100 lbft, 8000rpm

2. 1062cc, 7.5psi, 133 hp, 100 lbft, 7000rpm

I'm sticking to 100 lbft as I intend to use helical gearing.

I like the idea of the 952 but the use of the 850 block and flimsy crank worries me, plus it would cost a lot more.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Wasn't the combustion chamber of the K100 about 26cc?
Perhaps if you advance/reard the cams then you need less to be cut from the pistons although the profile might not be optimal anymore...

Just do the 952cc with 7.5psi and high CR. It might be doable with good ignition and turbo boost control.

The SC build guide states 22cc chamber volume for the K100 and it looks about right.

The larger LSA (Lobe Separation Angle) would be beneficial in reducing the revs at which peak torque ocurrs.

The 1062cc would be much cheaper and have more useable torque.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The answer to the original question is YES.

After lengthy deliberation, the planned spec is as follows:

998 A+ block, offset bored +0.120", centre main strap and custom thrust washers, decked 0.156"
Hypatec +0.120" pistons, teflon buttons
850 crank, wedged, nitocarburised and balanced
998 A+ rods, lightened and balanced
K100 cams reprofiled to 265 degrees duration
SC conversion kit etc
Ultralight pre-verto flywheel etc
Std drops and gears, rebuilt.

GT1752 on custom manifold
Megasquirt ignition and fueling.

This makes 981cc from 68mm stroke and 67.6mm bore, virtually square.

Theoretical 150hp/100lbft from 10psi at 7500 rpm.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Hi,
That should make a cracking screamer!
Yet the high CR and mild cam would be good for a daily driver :)
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

I'm hoping that this will produce the holy grail as well - 60mpg.

My 5 port 998 turbo will still be going into the car in the next couple of months - once the fuel injection is proven.

This cold weather and man-flu has really slowed things down.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I searched for an answer to this question, sorry if I missed it elsewhere.
Can you use the K100 pistons? I tried looking up the stock 67mm Mahle piston, part number 082 90 00. I can't decipher the data sheet fully, but it seems to be saying the pin height is 32.7mm and the pin diameter is 18mm. The 67mm bore is about as big as the small bore Mini block can be bored, the pin height difference would drop the top of the K100 piston down the bore by .046", so decking could fix that, but I don't know if the little end of a 998 rod could be opened up from 5/8" to 18mm. Anybody tried this?

You can now get +0.120" pistons for the 998. Thats about 67.6mm bore. According to Vizard, the 998 block can be bored to take Imp pistons at 68mm and some blocks even more.

I've measured up my 998 block and it has approx 7mm thick walls so plenty of meat to take out. So i'm offset boring to get closer to the K100 chamber spacing.

Those Mahle pistons sound interesting. I would think that the rods could be taken out to 18mm small end. The early bushed ones must be about that.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

8Valved Bimmers are 1000cc & 16v are either 1100cc or 1200cc for the later ones

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""

oops, sorry, only read the first page of this thread when i typed that, silly me, getting old & blind
carry on...

www.miniman.com.au

"""LazyGoodForNothingSmartArseKnowItAllBackYardMiniMechanic"""