Author Topic: Dreamtuning: max stroke crankshaft that it will fit... (Read 12105 times)

nuvolarossa · « **on:** May 11, 2008, 04:55:20 PM »

Hi, I need to have an answer to my frequent dream, so that it will stop coming in my mind:D

Ignoring the friction, the undersquare thing, the rod lenght, piston velocity and overall money....

what is the crankshaft with bigger stroke that will fit without hit the bottom part of the block(without mods to the block)?

There is the clearence to go over 90mm of stroke? something near 99mm without modify the block?

Or who have a oilpan removed or engine dismantled, can measure how much clearence there is when the rod, as the crank turn, go near the block?

What's the Block Deck Height (This is the distance from the centerline of the crankshaft to the top of the block) on M42, and on M44?

nickmpower · « **Reply #1 on:** May 11, 2008, 06:57:00 PM »

you wonld want to go much higher then the m47, becuae of how much the pistons will stick out the bottom of the bores at BDC

strypt · « **Reply #2 on:** May 12, 2008, 05:04:58 AM »

I believe Hartge did a 2.3L M44 with 99.6 mm stroke? I would guess this is about max possible stroke on these engines

Dunno about modifications to those blocks.

Deck height is the same on M42 and M44 but I don't know the actual dimension.

RouteZeroDesign · « **Reply #3 on:** May 13, 2008, 06:48:38 AM »

Yeah, im fairly certain that the Hartge 2.3 kit is the max you can go with block modification.

DO you guys know what the maximum bore is, before the cylinder walls start getting too thin?

CePa318IS · « **Reply #4 on:** May 13, 2008, 02:53:43 PM »

can you use the m42 forged rods with the m47 crank without modification?

that m47 crank is 88mm correct? I have been thinking of stroking mine, but havent dug into the research yet.

RouteZeroDesign · « **Reply #5 on:** May 13, 2008, 05:42:53 PM »

CePa318IS
It would be great if you could do that, but you'd end up putting the stock piston through the head on the first turn over.

If you're using the stock pistons you would have to get rods that are 3.5mm smaller (I think the m42 crank is 81mm but i cant remember)
or
If you're using the stock rods, you would have to get pistons with a 3.5mm lower compression height (compression height=vertical distance between center of wrist pin and the top of the piston, excluding the dome)
The first option is better, because taller compression height is better for Forced induction...thats the route your going, right?

With a 88mm stroke and a rod length of 136.5mm (is standard 140mm?) the rod ratio would be 1.549:1
Whereas with the 88mm stroke and 140mm rod length the rod ratio is 1.590:1

Increasing the rod ratio reduces rod angularity, which reduces the side loading of the piston against the cylinder wall thrust surfaces.

As you can see its not really an easy choice to make, and the best solution is to go for aftermarket pistons and rods, that way you can have your cake and eat it!

Hope that helps

Paul

strypt · « **Reply #6 on:** May 14, 2008, 02:05:02 AM »

M42 crank is 81 mm - correct but rod length should be 3.5 mm shorter than stock, if original compression height is retained. Half the stroke is "positive" and the other half is "negative". I hope you understand what I mean

english is not my native languange.

RouteZeroDesign · « **Reply #7 on:** May 14, 2008, 01:12:30 PM »

lol, i cant believe i did that.
My mistake, thanks for pointing that out.

In my defense, it was 1:13AM.....i was very tired

Okay, its fixed now, just so nobody picks up false information

pungky29 · « **Reply #8 on:** November 18, 2008, 07:12:39 AM »

Hi All!!

The bore x stroke of Hartge 2.3L M44 is 86mm x 99.8mm resulting in 2,319cc
I've read in an article on old European Car magazine (1997 edition if I'm not mistaken) about E36 compact modified by Hartge using this 2.3L M44. It was mentioned in the article that Hartge used a steel plate glued (using special glue) on top of the block to accommodate the 99.8mm stroke. Unfortunately the article didn't mention the thickness of the steel plate
I think a new liner with 86mm bore is used to tie together the additional steel plate and the cylinder block
Hartge applied the same method in S52 B32 engine which enlarged to 3.5L

It's cheaper to use E36 M3 S50 B30 US piston (86mm diameter with 32.8mm compression distance) together with 135mm conrod length and 88mm stroke of M47d crankshaft to obtain 2,044cc. For sure we have to enlarge the M42/M44 cylinder bore, but considering the bore distance of 91mm, it's still enough clearance
The deck height is 211.8mm, 0.35mm lower than original deck height of M42 & M44 which can be neglected

M42 used 84mm diameter piston with 31.65mm compression distance, 140mm conrod length and 81mm stroke, 1796cc --> deck height 212.15mm

M44 used 85mm diameter piston with 30.4mm compression distance, 140mm conrod length and 83.5 stroke, 1895cc --> deck height 21.15mm (same as M42)

That's the beauty of BMW engines, we can interchange the internal parts to obtain larger displacement without having to buy custom made piston, conrod and crankshaft

Ciao,
Pungky29

hesgone2fast · « **Reply #9 on:** November 18, 2008, 07:59:30 AM »

hey guys, like said above, you wouldn�t want to go much more than 88mm stroke on this engine, maximum bore is about 87mm.
You could use the M47N crank (90mm) but requires some mods to it, and adding a custom front nose in two pieces (not very reliable).
more than that, it would be too much over square.
Stock M42 rods can be used with M47 crank with no mods. but the piston would have to be shaved until desired compression.
By the way, Tonight I will put my M47 crank(88mm) for sale up here... I live in Spain, so It�s a great opportunity for getting one in europe, as there�s no other for sale anywhere.

nuvolarossa · « **Reply #10 on:** November 18, 2008, 10:29:12 AM »

thanks pungky29 for the post about the hartge and its steel plate

I had a magazine of those years with an article about that hartge engine but I can't find it and at the time I wasn't really interested in engine internal mods

@hesgone2fast, as I wrote on title this is only dreamtuning, no one man here will do what there is in this post, as it's unrealiable, difficult, pricey....

it was just curiosity
...you made a mistake with the oversquare/undersquare thing in your post

hesgone2fast · « **Reply #11 on:** November 18, 2008, 02:33:38 PM »

Quote from: nuvolarossa;61139

thanks pungky29 for the post about the hartge and its steel plate
I had a magazine of those years with an article about that hartge engine but I can't find it and at the time I wasn't really interested in engine internal mods

@hesgone2fast, as I wrote on title this is only dreamtuning, no one man here will do what there is in this post, as it's unrealiable, difficult, pricey.... it was just curiosity
...you made a mistake with the oversquare/undersquare thing in your post

Don�t say no one will ever do what�s on this post, I�ve spent $5000 on my engine, I built it myself, I�ve spent 3 years collecting parts,gathering info,I bought an M47N crank and saw it was too risky to make it work, so I sold it...
What mistake did I make??

crazzy_hippo · « **Reply #12 on:** November 19, 2008, 02:48:00 AM »

Quote from: hesgone2fast;61159

Don�t say no one will ever do what�s on this post, I�ve spent $5000 on my engine, I built it myself, I�ve spent 3 years collecting parts,gathering info,I bought an M47N crank and saw it was too risky to make it work, so I sold it...
What mistake did I make??

I am curious, how did you managed to fit a M47N crank into M42? Cause I though only the original M47 fits?

pungky29 · « **Reply #13 on:** November 19, 2008, 03:23:36 AM »

I have compared the M47N crank (90mm stroke) and M47 crank (88mm stroke)
The M47N used different crankshaft bearing dimension
I've checked the ETK, using the part use facility and it turned out that M47 crank and M42 (also M43, M40 and M44) using similar crankshaft bearing
I don't know if we can machined the block to accept the M47N crank, but it's too risky I guess

hesgone2fast · « **Reply #14 on:** November 19, 2008, 04:30:24 AM »

Quote from: pungky29;61195

I have compared the M47N crank (90mm stroke) and M47 crank (88mm stroke)
The M47N used different crankshaft bearing dimension
I've checked the ETK, using the part use facility and it turned out that M47 crank and M42 (also M43, M40 and M44) using similar crankshaft bearing
I don't know if we can machined the block to accept the M47N crank, but it's too risky I guess

Guys according to reaolem.com, the crank bearing of the M47N crank is 60mm, the same as the M42 and M47.
what I meant by risky is that the front nose of the M47N crank is way too short, so a custom adapter has to be made to extend the nose,this would result in a two-piece crank, I would not trust a two-piece crank(especially with the chain sprocket beign in the extra piece)at 8000rpm...
The guys at MM say it�s ok with their adapter, ok, go for it...