Dr2002

M10 Forged Piston Specs and Cyl Head Flange Specs for CAD

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I've been using the search function but couldn't find what I wanted. Thus I'm posting here and willing to accept the consequences.

Background- I am modeling the "airflow path" and pistons in SolidWorks to complete a powertrain analysis. I plan to create a new intake manifold, and potentially pistons & rings.

03.jpg

I'm looking for complete specifications and dimensions for a M10 forged piston. I would prefer for a late 70's 2.0L engine since this was the largest stock M10 of the correct era. I am assuming this is referred to as a M10 B20, 1990cc.

These are the dimensions I have:

compression height = 42.5mm

Piston Compression height is measured from the pin center line to the flat portion of the piston

dome height = 3.7mm

measured from flat portion to top of dome

total height = 82.2mm

measured from flat portion to bottom of skirt

pin diam = 22mm

pin length = 71mm

diameter = stock 89.01mm

Top ring thickness = 1.75mm

2nd ring thickness = 2mm

oil ring thickness = 4mm

The dimensions I am looking for are:

- ring land position dimensions from flat portion to centerline of ring grooves

- ring land width

- dimensions for dome

- piston crown thickness (thickness of top flat surface)

Also, if anyone has a 2D (or 3D) drawing of the cylinder head flanges for the intake and exhaust, that would be grand.

The pistons I would like to create are (refer to pic below):

* High ductility 2618 alloy

* Dual forced pin oiling

* Lateral gas porting (B)

* 1.5 x 1.5 x 3 mm ring pack or 1.0 x 1.2 x 2.5 mm

* Napier 2nd ring

* Fully machined

* Second land accumulator grooves ©

* Top land mini groove technology (A)

* Tapered skirts with coating

* Triple wound spiral locks

hrdp_0910_16_z+piston_ring_tech+.jpg

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Interesting looking piston, (the one used as the example with the arrows and letters) wedge head SB Chev around 10 to 1 with a long rod or 400 crank. I like your approach, personally I would use a Dykes or .043 top, as gas porting, vertical or horizontal on anything but a race motor can be problematic. The ports tend to clog with combustion stuff, and without the pressure backing the low tension tops can incur blow-by at speed. I like the oversize oil returns on the oil ring, great idea that really augments oil control. Your alloy selection is by far the most durable being the material of choice originating form WW2 allied aircraft power-plants.

You could try contacting Phil at JE Pistons, he might be willing to supply the dome data you need if you promise not to start making pistons.

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Background- I am modeling the "airflow path" and pistons in SolidWorks to complete a powertrain analysis. I plan to create a new intake manifold, and potentially pistons & rings.

Not sure I understand -- are you are just doing an exercise here, or do you actually plan to produce realistic drawings of workable parts? For any type of modeling to be useful, I'd think you'd need to establish a baseline with known parts. It would probably make sense to do that with a few variations of stock parts. To get the detail needed to actually do that, you cannot rely on message board info, you would be best to get the parts in hand to check all the features & dimensions. Once you've compared two or more versions of the stock hardware, confirm if your modeling shows the same difference that has been measured in the real world.

If you don't prove correlation between your modeling & known results of real parts, there is no confidence in the testing, and it becomes much less useful than it could be.

I'm looking for complete specifications and dimensions for a M10 forged piston. I would prefer for a late 70's 2.0L engine since this was the largest stock M10 of the correct era. I am assuming this is referred to as a M10 B20, 1990cc.

Here too, I'm not sure you're on track to get anything like a 'complete' piston drawing, because there is a LOT more you'd have to capture to get that done. Not that you need complete specs for a piston to get parts made, in fact it is much more common to rely on the piston company to use their expertise in working with the forgings they have available. You don't spec their forgings, so it is pointless to produce a 'complete' print that might include dimensions that don't comprehend the raw forging.

Typically the end user just defines the dome or dish (if any) and all the other normal features that can be readily customized. The only feature the customer might need to supply a detailed drawing for would be a dome, dish, or valve relief if needed.

These are the dimensions I have:

compression height = 42.5mm

Piston Compression height is measured from the pin center line to the flat portion of the piston

dome height = 3.7mm

measured from flat portion to top of dome

total height = 82.2mm

measured from flat portion to bottom of skirt

pin diam = 22mm

pin length = 71mm

diameter = stock 89.01mm

Top ring thickness = 1.75mm

2nd ring thickness = 2mm

oil ring thickness = 4mm

These specs you have above appear like some sort of stock piston, which I'm not sure relates to any type of desirable design for a forged piston.

There is no need to replicate antiquated features, like long skirts & long pins if you are talking forged pistons.

No BMW piston had the diameter as listed (diameter = stock 89.01mm ) that looks like the BORE diameter.

The difference between bore diameter & piston diameter is the clearance, and the fitted clearance for the stock cast piston won't be anything like what you'd need for 2618 alloy.

On that matter, the expansion rates of 2618 won't be like a stock piston, so the actual piston shape is quite different. While neither cast or forged pistons are round, the ability to predict what different diameters and how to shape them to be round at operating temp is beyond what anyone without more intimate knowledge of the actual forgings used could be expected to have.

The dimensions I am looking for are:

- ring land position dimensions from flat portion to centerline of ring grooves

- ring land width

- dimensions for dome

- piston crown thickness (thickness of top flat surface)

Still not sure the specs you have, or the specs you are asking for, will really help get a working drawing for a forged piston.

Dimension for what dome? A dome shape would chiefly depend on the cylinder head chamber, and the desired compression ratio. It would help to identify what you are after, otherwise the answers could be all over the map. Stock can be a lot of different types, and forged is not stock, so who knows?

Crown thickness of a cast piston won't be translated to the same requirement for 2618.

If you know what your applciation needs, then you need to ask the manufacturer if they can produce that thickness with their forging blanks & your compression height requirement. As all 2618 forged pistons for an M10 would be custom, there is no definate answer to your question.

The pistons I would like to create are (refer to pic below):

* High ductility 2618 alloy

* Dual forced pin oiling

* Lateral gas porting (B)

* 1.5 x 1.5 x 3 mm ring pack or 1.0 x 1.2 x 2.5 mm

* Napier 2nd ring

* Fully machined

* Second land accumulator grooves ©

* Top land mini groove technology (A)

* Tapered skirts with coating

* Triple wound spiral locks

This looks like a feature list from an aftermarket brand (ICON pistons?) If you are considering using them, ask them about what 2618 forgings they have to work with size-wise for your requirements. When you see a feature listed as "fully machined" that in particular is only relative to the forging blank used. It simply means they took all the steps they could to remove extra weight by machining away parts of the raw forging, and of course a different company with (perhaps) a different forging would not need the exact same material removed unless it was the exact same forging. How do you incorporate that in your drawing in advance of knowing what the raw forging is?

The number one tip I can share on selecting features for custom pistons is this:

Always start with finding if your desired ring type & widths are even available for your bore diameter.

Who makes a suitable ring set in the correct diameter, with those widths you've listed?

You can easily make pistons to fit any size ring, but you have to have the rings available first.

I would recommend using rings that have a normal radial depth (follow D-wall spec) in whatever set you end up with. Narrow ring widths are great, but there is not much available in proper bore size for an M10. If you have a 4.00" bore, there's a ton of choices, not so much for 89 to 90 mm in performance oriented rings.

The other thing is if you design your own dome, verify the location of the valve reliefs (assuming you need them.) I use an old M10 fuel pump rod sharpened to a point on one end, and pushed through a valve guide to mark the piston while it's at the correct position (not necessarily TDC.) I have seen custom M10 pistons sold by BMW specialists that do not have this correct.

Your plan to create a new intake manifold, pistons, and rings is quite ambitious, even if it is just for a drawing exercise. I still contend you should model the stock parts for baseline before you reinvent the wheel. Induction tuning can be modeled, but the pressure wave excursions are not anything like the steady-state flow on a flow bench so it is very difficult.

Good luck with the project, and please share the results here when you get something!

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isnt the flow path affected by combustion chamber as well ?

and as far as i know, the factory pistons where not forged, only the turbo ones where, and even there i am not 100% sure back then.

What is the goal exactly, there is plenty of aftermarket piston on the shelves already to suit all M10 needs, in terms of compression ratios and head matching.

Not to mention the non-bmw sources (toyota, olds,, vw)...seems like a nice engineering project, but why all thoses efforts?

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John_a

Very well written, you address some areas I never even considered, ring availability and which piston vendor has a forging blank compatible.

You are obviously well versed in engine design and a source of good data.

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Sorry, I was trying to be as simple as possible to not confuse my needs. The basic dimensions I need could be found by anyone who had an old piston on the workbench. What I am looking for is:

- ring land position dimensions from flat portion to centerline of ring grooves

- ring land width

- ring land depth (added this; od of piston under rings)

- dimensions for dome

- piston crown thickness (thickness of top flat surface)

I also wanted to verify the other dimensions in the post.

Otherwise, to answer your questions:

I have software for modeling 3D combustion that I use for OEMs. I am trying to put together a presentation using non-customer data and a 1970's BMW engine seemed far enough removed. It also has some personality to it.

I can manufacture any piston or ring design required. The image is from Hot Rod magazine which was for reference. The LS-engine (LS7 especially) was a very sophisticated piston/piston ring package which is the benchmark in the industry.

The plan is to show a stock BMW setup and then improvements gained by modeling a better piston, rings and combustion chamber. This may or may not be with the cam timing left the same (using a Schrick 294 grind since a friend had one available). The purpose is to show how limited improvements in the piston and piston ring can allow even a 1970's engine to meet modern benchmarks.

I may take this to prototype and run the engine to show correlation to the CAE results.

The piston data I garnered from the Mahle online database. I was unsure of the engine designation (called a M10 B 20, 1990cc):

http://www.motorenteile.mahle.com/eLIZA/mahle/query/engine/byParams

Piston Part No. 082 10 00

You are correct, looking again at the data the engine bore is 89.01mm. The piston appears to be 88.97mm.

The dome would be for the late 70's 320i head, looking like the pictures posted from the manual above. If no data exists with good dimensions I will find the piston to scan it. Accurate modeling of the "jelly bean" would produce closer results to actual.

And the cylinder head chamber would be the next hurdle. This would need to be scanned or cmm'd, but removing the head from a engine is a little easier than a piston! However, I can get close if I have the piston, the gasket thickness and the compression ratio.

For information, the 2618 alloy is the "gold standard" for forgings. Mahle (and others) manufactures pistons in 4032 alloy which is for OEM engines with piston-slap concerns (need tighter wall clearance for cold start and less expansion). My database has coefficients for both, but the analysis will not include cold start initially.

Everyone will also be happy to know that there are many forgings available in the 89mm to 92mm range. Some examples are for Honda/Acura, Cavalier, Nissan 240sx, Toyota, Subura WRX, Dodge Stealth, etc. While they may not be an exact drop in, the forging blank can be machined for a BMW application.

Thank you everyone for all the interest. If you could help with the dimensions, that would be very much appreciated.

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Piston Rings and gas porting:

The problem is trying to generate a sufficient ring seal while employing low tension (for reduced friction). Lateral gas ports achieve this, increasing the seal 15 to 50% only at higher cylinder pressures (after combustion). Therefore, you only pay the friction penalty during the event when you actually need the higher effort seal!

I have seen (and it sounds like you as well) the negatives of gas-porting. This is especially so when used with a carburetor (NASCAR not included). Modern EFI, combustion chamber design and coatings can almost eliminate this concern for a hobbyist (good gas, light duty cycle, proper engine care, etc).

Also, lateral gas ports are less susceptible than traditional vertical ports. As stated by Car Craft:

"Usually gas port holes are drilled vertically from the piston top down to the first ring land (right). But vertical holes can get carbon-plugged, and they may promote crack formation resulting in piston failure above the groove. An alternative method is “half-moon” lateral holes in the top of the groove (left)"

p151244_image_large.jpg

Also, someone was asking about 92mm forged pistons and available rings. While this is not a drop in (pin location off), it shows what is out there. The ring pack would be applicable, with a 1.2 x 1.5 x 3mm sizing. Other brands as well have 89, 89.5, 90, 90.5mm ring packs.

Item Code 14491

Vendor Name Probe Industries

Product Type Pistons

Product Model Sportsman Race Series - SRS

Engine Displacement (liters) 2

Engine Family SUBARU

Material 2618-t61 Forged Aluminum

Base Bore (in) 3.622 (92.0mm)

Stroke (in) 2.953

Rod Length (in) 5.135

Compression Height (in) 1.287

Top Type Dish Top

Net Head Volume (cc) -13.5

Weight Without Pin (g) 372

Wrist Pin Diameter (in) 0.906

Wrist Pin Length (in) 2.250

Wrist Pin Weight (g) 69

Pin Lock Type Sgl Spiral

Ring Set # 14491-STD - SWF20051-0

14491-.50 - SWF20051-2

Top Ring Groove Size 1.2 mm

Second Ring Groove Size 1.5 mm

Oil Ring Groove Size 3.0 mm

Quantity Sold in sets of 4.

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Also, on the subject of Piston Rings.

Looking further I found these below. What is nice is that they are for a 90mm bore, and come in at 1.0 x 1.2 x 2.8mm. Also, the price is $31 for a set. WOW!

Brand Wiseco

Manufacturer's Part Number 9000XX

Part Type Piston Rings

Product Line Wiseco XX Piston Ring Sets

Summit Racing Part Number WIS-9000XX

Bore (in) 3.543 in.

Bore (mm) 90.000mm

Top Ring Included Yes

Top Ring Thickness 1.0mm

Second Ring Included Yes

Second Ring Thickness 1.2mm

Oil Ring Included Yes

Oil Ring Thickness 2.8mm

Oil Ring Tension Standard

File Fit No

Gapless No

Top Ring Material Stainless steel

Top Ring Facing Material Gas nitrided

Second Ring Material Cast iron

Second Ring Facing Material Phosphate coated

Oil Ring Material Nitride coated stainless steel

Quantity Sold as a set.

Notes Single piston set.

High-quality XX piston rings from Wiseco.

Wiseco's XX piston ring sets feature a stainless steel, gas-nitrided, barrel-faced top ring. They also contain an under-hook style, cast iron, phosphate-coated, taper-faced second ring. Oil rings in the XX sets are 3-piece assemblies with gas-nitrided rails and a stainless steel, flex-vent spacer.

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The purpose is to show how limited improvements in the piston and piston ring can allow even a 1970's engine to meet modern benchmarks.

Good luck.

The

late 1970's 320
had no dome, so just draw yourself a straight line, make it a plane, call it done. It should sit about a mm below

deck height.

4 valves, EFI, high compression and a head that keeps heat in the chamber,

that's modern. I thought, 'wow, I could take an S2000 motor and gearbox

and ecu and make my 2002 into a potent little racecar'...

then I realized, shit, why not just race the S2000 and have modern suspension

too.

If you really think that the piston crown and ring package are all that

define a 'modern' motor... well... I've got some prime coastal

property in Arizona you might be interested in...

t

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I will research this further. I did uncover a whole host of combinations with heads (121, E12, 318i, 320i) and two different rod lengths (135mm, 144mm).

The engine I was targeting is from a 1978 BMW 320i that I found in a local junkyard. It is a true 1990cc engine (later 320i's we only 1.8L). It was running the Tii like cast aluminum intake manifold with CIS injection.

I am not sure about the S14 4-valve head though. That might be interesting as a secondary exercise. Tradition 2 valve heads, especially opposed valves, have great flow and the added expense, friction and complexity of the four-valve head is very minimal.

The S2000 is a great engine! Horrible torque though. I actually prefer the turbocharged 2.0L Ecotec, engine code LNF. It employs direct injection, a twinscroll turbo, a slick 5-speed for RWD. It puts out stock 260 horsepower (194 kW) and 260 lb.-ft. of torque (353 Nm).

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...ummm, where did you find a 144mm rod?

If you expand your search to Euro pistons, you discover that every head

had at least 3 'factory' varieties, and Ross can make you anything you

can't find.

and yeah, if you let an S2000 drop below 4k, it's just not the same...

t

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S14 Con Rod, 144mm E30 M3

I'll have to research the combinations further or just stick with the 1978 320i motor.

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Oh, righto- I thought you were sticking with M10's.

t

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Something interesting I read on the e21 forums that comes to light at the bottom:

A little engine background:

To stroke a motor you need to increase the stroke of the crankshaft. Every +1mm you increase the crank (I assume that the 2.0i s14 is a 135mm rod and 80mm stroke like the m10b20 but I could be wrong. Stock s14b23 connecting rods are 144mm) so if you increase the stroke to 81mm you are actually increasing your stroke by 2mm because you pull down 1mm and push up 1mm (remember there is an up stroke and a down stroke). So for every 1mm the gain is 2mm. If you move from 80mm stroke to 81mm stroke you will pull the piston and rod down 1mm further on intake stroke however on compression stroke you will also push the rod and piston up 1mm further into the head and valves (which is bad). We use different pistons to compensate for this. For simplicity we keep the same stock s14b20 connecting rod and we change from an 80mm stroke to an 81mm stroke

On the down stroke our stock rod pulls the piston down 1mm extra, on the up stroke it pushes it up 1mm extra. To compensate for this we relocate the piston wrist pin UP 1mm, which drops the piston DOWN 1mm. Now when we pull down on the intake stroke the piston pulls down 2mm extra (one from the crankshaft and one from the relocated wrist pin) but on the compression stroke the +1mm up on the crank is negated by the -1mm down on the piston wrist pin so we have a net of 0 meaning the piston comes to the same place but pulls down 2mm further - increasing stroke by 2mm for every 1mm change to the crankshaft.

The s14b23 crank is 84mm stroke (this I know) and the s14b25 crank is 87mm stroke. By going from s14b20 80mm to s14b23 84mm stroke we apply the same theory as above so we must relocate the piston wrist pin up the amount of the stroke increase, in this case 4mm. This gives us 8mm stroke increase and with a 95mm (i think) bore that is 300cc difference. The next thing engine builders look at is rod/stroke ratio - which is the ratio of the conecting rod to the stroke. On the s14b23 BMW chose the 144mm rod because it yields a rod/stroke ratio of ~1.68 which is considered by many to be ideal. If you change stroke at the crank you must also change piston wrist pin location. If you keep the 135mm rod (which is what I assume stock is) you will have a lower rod/stroke ratio of ~1.6 which means your piston speeds will be higher. as long as you are not racing or trying to rev up over 8,000rpm with your motor you should be OK using the s14b23 crank with stock s14b20 rods and get new pistons to match. I think that you would find cheaper pistons available with the 144.25mm stock s14b23 rod because the combination is so popular.

Short answer - when you change stroke by anything over +1 to +2mm you should expect to need new crankshaft, connecting rods and pistons.

Just to add that the 320is pistons can and should be kept. Actually they're an upgrade for the M3 e30 engine builders and this increases compression to around 12:1.

If you're using OEM cams it's a direct fit but if you plan using wilder cams just deepen the valve pockets around 1.5mm.

I advise you to deepen the pockets even if you're using the OEm cams for the simple reason that if you want to upgrade them later the pistons don't need to come out.

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