Author Topic: Stroking + FI (Read 4585 times)

projectmick · « **on:** September 17, 2008, 02:44:30 PM »

I have an m44 engine that I basically want to extract more power from, and have been looking into stroking it using the m47 crank etc.

What I am having trouble getting my head around is compression ration and piston heights etc, as I am not very sure about what is needed.

What I want to achieve is to increase the displacement of the engine, as in the long term i want to go FI with the project, and, please correct me if i'm wrong, a larger displacement should yield a better response from FI?

However I do not want to raise the compression ratio too high with this in mind, as I am planning on building the engine up with forged parts to replace the cast rubbish that lives in there atm, so dont want to find I have to take it apart again in a years time to replace with lower compression parts.

So, say I have the m47 crank 88mm stroke and a bore of say, 86 or 87mm, can I then use something like the MM pistons to lower the comp? Will this at least lower the cr to stock levels, so I can run a low boost application?

Or can I just use the m47 crank with low compression standard size pistons and rods? Will this fit? If so I can run higher boost when I go FI

Sorry for my complete lack of knowledge on this

halcron · « **Reply #1 on:** September 17, 2008, 09:40:30 PM »

You are planning the same engine as me. I am planning to buy the engine parts from MM as they offer the M47 crank with conrod + pistons and bearings etc. This will result in 8.6 compression.

hesgone2fast · « **Reply #2 on:** September 18, 2008, 02:55:14 AM »

Both of you guys are building the same engine as I have already built with FI in mind. there are many options on piston/rod combinations.
What I have now is the m47 with 360� oil main bearings, m42 rods, and M3 (S52 3.2L) 86.4mm pistons shaved to have zero deck height. this yields a CR of 11.5:1.
Of course is way too high for FI, but like I said,I built it with FI in mind, so I know basically all options available. The perfect combination of course would be MM rods and pistons that give 8,6:1, but a little pricey at $1400 or something like that. I bought a set of S52 pistons and rods in california. the rods ended up being 135mm long, and have the exact same dimensions as the M42 rod, except being 5mm shorter (same big end diameter, same piston pin diameter)
What I�m triying to say is that using the M47 with stock S52 rods and stock M3 pistons (without shaving them)would give a displacement of 2064cc, and a CR of about 9.2:1 with aproximately a deck height of 2mm.
I paid $250 for the set of 6 pistons and rods including shipping to Spain, so as you can see is a better option for the wallet.
As far as reliability of the combo, well I�ve seen many people putting a nice 8psi on stock M3 engines (stock CR 11.5:1) and holding up together pretty good. So I think this combo shuld be reliable with a CR of 9:1 and lets say 10psi of boost.
Sorry for the looong story, but just triying to leave things straight.
If some number is incorrect, please correct me.
Thanks!

nuvolarossa · « **Reply #3 on:** September 18, 2008, 04:10:34 AM »

sure there are more economical possibilities than MM $$$$ parts.
all sized are in millimeters.

S 50 B 30 US,
L6 Gasoline, 2990 cm�, 180 kW (245 PS), 10,5:1
4 Valves,

compression height 32,8
Valve recess depth 0,52
Valve recess depth 3,11
combustion chamber depth 3,5
Total piston lenght 51,8
outer pin diameter 22
pin lenght 56
nominal cyl diameter 86,00

S 52B32 US,
L6 Gasoline, 3201 cm�, 180 kW (245 PS), 10,5:1
4 Valves,

compression height 31
Valve recess depth 3
Valve recess depth 1,62
combustion chamber depth 4,08
combustion chamber diameter 75
Total piston lenght 53
outer pin diameter 22
pin lenght 56
nominal cyl diameter 86,40

now double check calculations with these specs

PS: don't go lower than 9:1 CR, use the money that you will save in respect to MM parts to buy a great standalone

projectmick · « **Reply #4 on:** September 18, 2008, 05:09:37 AM »

Thanks for the info guys - I will sit and have a look at al those numbers today!

So just to clarify, the stock bore on the m44 is 85mm, so I could use the mm stuff if I wish (live in England so exchange rate is favourable atm) alongside the m47 crank?

If I decide to bore out to 86mm then m3 pistons will work? Are these the E36 or E30 ones? And is it euro or US spec you have used?
Finally, as you said above, stock m3 rods work with these pistons, would stock m44 ones work also? (with regards to length - I would get forged ones made)

With regards to CR as long as I can keep it to stock CR with forged internals that will be fine as I only want to run a low boost application anyway.

Thanks again guys!

nuvolarossa · « **Reply #5 on:** September 18, 2008, 07:07:45 AM »

guys, please take a minute and go in your user panel and insert your location, at least to let us know if you are in europe or in america.
It will help to give suggestions and to have a reference when speaking of bmw engines, as some of them are different between two continents... and so internal parts may be different.

thank you.

projectmick · « **Reply #6 on:** September 18, 2008, 07:21:28 AM »

Sorry, I'll go and do that now - I presume that the parts mentioned above will still fit and that I will just have to order from the US? I have no problem getting parts from abroad if they will work, so all suggestions were welcomed.

hesgone2fast · « **Reply #7 on:** September 18, 2008, 08:28:08 AM »

Quote from: projectmick;56925

Thanks for the info guys - I will sit and have a look at al those numbers today!

So just to clarify, the stock bore on the m44 is 85mm, so I could use the mm stuff if I wish (live in England so exchange rate is favourable atm) alongside the m47 crank?

If I decide to bore out to 86mm then m3 pistons will work? Are these the E36 or E30 ones? And is it euro or US spec you have used?
Finally, as you said above, stock m3 rods work with these pistons, would stock m44 ones work also? (with regards to length - I would get forged ones made)

With regards to CR as long as I can keep it to stock CR with forged internals that will be fine as I only want to run a low boost application anyway.

Thanks again guys!

Yes, the M44 has a 85mm bore, Now that I have mine bored to 86,4, I recommend you to go with the 86mm pistons, since Its a little hard to match the headgasket (biggest available is 86mm bore) so mine hangs 0,4mm into the combustion chamber, not very happy with it though...
I have order a lot of stuff from MM, so yes now is a good time to import parts from them, but shipping is a little pricey...
The M3 pistons I used were from a 1997 M3 3.2L(S52) e36 US version
S50 pistons (E36 M3 around 1995) are 86mm
I don�t know what is the piston pin diameter on the M44, but some people here say M42 rods are better than the M44 ones. specially for FI. someone here put 27psi on stock M42 rods with no problems...
I believe Eagle Makes M42 forged rods with 135mm lenght, I remember seeing them on ebay for a very good price (about $200-$300 if I rememeber correctly)

About CR, the guys at Grassrootsmotorsports, put the Downing atlanta superchrager which blows 8psi, on stock internals on a E30 M42 tired motor (CR 10:1) and got pretty good numbers with no problems

nuvolarossa · « **Reply #8 on:** September 18, 2008, 08:58:54 AM »

I wrote to Cometic asking how much it would cost a MLS gasket as the ones they make, but with 87mm bore. I told them that there may be some people interested in these... I will report the answer in a new thread.

piston diameter on M42 and M44 is 22mm. Eagle Rods are cheap on ebay.COM for our engines(and sellers ship in europe too), but as there are two version (one 140mm and one 135mm) check and read CAREFULLY the auction's text.

hesgone2fast · « **Reply #9 on:** September 18, 2008, 09:14:33 AM »

Quote from: nuvolarossa;56935

I wroted to Cometic asking how much it would cost a MLS gasket as the ones they make, but with 87mm bore. I told them that there may be some people interested in these... I will report the answer in a new thread.

piston diameter on M42 and M44 is 22mm. Eagle Rods are cheap on ebay.COM for our engines(and sellers ship in europe too), but as there are two version (one 140mm and one 135mm) check and read CAREFULLY the auction's text.

I would definetely be interested in one!!!
That�s what I was talking about, the stock M42 rod is 140mm, but eagle makes them in 135mm, so good for FI, but check with the guy who sells them for big end dimensions, because I remember someone saying they were diferent... I think the big end of the M42/S52 rods (with no bearing) make 48mm, and I think I already asked the guy about this and seemed confused about the rods being different...

Thanks for sharing the info on the cometic gaskets!!

projectmick · « **Reply #10 on:** September 18, 2008, 07:04:04 PM »

I dont know if anyone has used this company before, but it seems they can build custom gaskets etc to your spec and bore etc.

http://store.nexternal.com/shared/StoreFront/default.asp?CS=vacmotors&StoreType=BtoC&Count1=443264186&Count2=360404610

Don't know if this is any help to you, I'm not sure about price, whether it is competitive or not but seems ok to me.

projectmick · « **Reply #11 on:** September 18, 2008, 07:07:10 PM »

Oh yeah m42 rods are better, I believe they e forged, wheras m44 are cast - part of the reason I was going to change it all up.