What is the largest displacement anyone here is running? I have seen stroker kits for 4.0 and 4.2 (95 mm bore IIRC)but I just want to see if anyone had any experience.
Specifically, I am trying to find out what is the largest bore the m30 can handle and still have room to o-ring the block. (standard or figure 8)
Thanks in advance for your time.
Largest FI M30 displacement?
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thespeedfactory
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A few observations on going oversize with the M30.
The "base" casting is more or less identical to the S38.
The block has as its fundamental internal dimensions the 100 mm center-to-center distance for the cylinder bore centerlines.
The deck height from main bearing centerline to the top of the block is 217.5 mm.
These dimensions more or less "frame" what kind of displacement one can obtain.
To repeat a bit of the obvious, BMW built the S38B35 with an 84 mm stroke; stock bore is 93.4 mm.
The -B36 went up to 86 mm; bore is the same as the -B35--93.4 mm.
The -B38 went to 90 mm, but the bore got taken out to 94.6 mm.
The problems BMW experienced with the upsizing to the B=-B38 are well known, i.e., con rod bottom end bearing shells failing, bottom end failures destroying the block proper.
If one increases the length of the crank throws, it becomes necessary to shorten the c-to-c on the rods accordingly. One can decrease the wrist pin to piston crown distance only slightly. This to keep sufficient ring land height for strength and to allow the oil scraper ring to clear the wrist pin.
As one lengthens crank throw and shortens the con rods, there are problems with the angle of the rod to the cylinder bore. http://victorylibrary.com/mopar/rod-tech-c.htm.
This may be a bit technical, but what it says is that it is Not Wise to go much below a rod-to-stroke ratio of around 1.60. Yes, it can be done, but you will pay a price in terms of piston longevity.
Let's look at crank throws. As a rule of thumb, the longer the crank throw, the lower the redline. The accepted formula is 600,000/ crank throw in mm.
For the -B35 we have 600,000/84 = 7142 rpm. More on this in a moment.
For the -B36, 600,000 /86 = 6977 rpm
For the -B38, 600,000/90 = 6667 rpm.
When Paul Rosche designed the S38, it developed that the crankshaft had internal harmonics, known as eigenvalues, which showed up around 7250 rpm. Any and all mechanical contrivances have eigenvalues. Operate them in a manner where that harmonic shows up, much like a tuning fork, and the thing will eventually self-destruct.
To defeat these vibrations, we have harmonic balancers. Not a smart idea to remove them. It would appear that Dr. Rosche fully understood that going much shorter than 84 mm was an invitation to problems. Going longer began to push the rod ratio angulation issue.
Dinan did a run of 92 mm cranks in the 90s, this for his 3.9 liter stroker engines. There were about 48 of these cranks made. They are unobtanium. Some longer throw cranks exist, but these are one-offs.
Going longer on throws, we see 600,000/95 = 6315 rpm.
If PPM want s to go out to 98 mm, we get 600,000/98 = 6122 rpm. Somehow I don't think 6100 rpm redline is going to get the potential buyers for this engine all hot and bothered.
But assume for the moment you do get a 98 mm throw crank. Using a rod ratio of 1.50, this give a rod c-to-c distance of 147 mm. Which is nice, but doesn't leave sufficient distance for the upper half of the piston to support the rings, their lands and the piston crown.
Go to a rod ratio of 1.60 and the c-to-c distance becomes 156.8 mm.
The issues of casting rigidity and strength also come to the fore with the 98 mm stroke. The lower end walls of the crankcase are strong, but not infinitely so. Milling clearances for a 98 mm crank is going to weaken things significantly. This may be able to be addressed by laying in layers of cast-iron or low-hydrogen rod on the exterior of the block to increase (return) some measure of rigidity, then remachining all surfaces in a block prep machine to address any distortions from the machining/welding.
Now let's take a look at the cylinder-to-cylinder distance of 100 mm. This is an unalterable measurement. With the -B35's 93.4 mm bore, we have an intra-cylinder "siamesed" distance of 6.6 mm. Go larger, say out to the 94.6 distance on the -B38, that number goes down to 5.4 mm. This is very thin, especially so when one looks at the pressures within the combustion chamber/cylinder present on the power stroke. Try to go larger, and the odds of having the block casting crack are quite good.
But we are going to insist on getting to 4,200 cc displacement.
4,200/ 6 cylinders = 700 cc per hole.
Volume of a cylinder = pi * height * r^2. 3.1416 * 98 mm * square root of the bore diameter. Solve for bore diameter and we get a bore diameter of 95.3 mm. Wall thickness is now down to 4.7 mm.
Any one who is pushing displacement on this motor is not going to be babying it.
Care to guess how long before the block fails?
Possible solution.
Hog out the cylinders entirely. Replace with Darton sleeves. I tend to be skeptical if these sleeves, which will have a flat machined on them to mate up where the intra-bore "siameseing" is going to be necessary will be strong enough at a combined 4.7 mm wall thickness, but then, it's your dime.
I am here to tell you that the sleeves, plus the requisite engine building are not going to be done on your lunch money.
So if you want to be the first one on your block (nice pun. huh-huh-huh) to drop $7,500 plus-plus-plus on this deal, let us all know how it goes.
The "base" casting is more or less identical to the S38.
The block has as its fundamental internal dimensions the 100 mm center-to-center distance for the cylinder bore centerlines.
The deck height from main bearing centerline to the top of the block is 217.5 mm.
These dimensions more or less "frame" what kind of displacement one can obtain.
To repeat a bit of the obvious, BMW built the S38B35 with an 84 mm stroke; stock bore is 93.4 mm.
The -B36 went up to 86 mm; bore is the same as the -B35--93.4 mm.
The -B38 went to 90 mm, but the bore got taken out to 94.6 mm.
The problems BMW experienced with the upsizing to the B=-B38 are well known, i.e., con rod bottom end bearing shells failing, bottom end failures destroying the block proper.
If one increases the length of the crank throws, it becomes necessary to shorten the c-to-c on the rods accordingly. One can decrease the wrist pin to piston crown distance only slightly. This to keep sufficient ring land height for strength and to allow the oil scraper ring to clear the wrist pin.
As one lengthens crank throw and shortens the con rods, there are problems with the angle of the rod to the cylinder bore. http://victorylibrary.com/mopar/rod-tech-c.htm.
This may be a bit technical, but what it says is that it is Not Wise to go much below a rod-to-stroke ratio of around 1.60. Yes, it can be done, but you will pay a price in terms of piston longevity.
Let's look at crank throws. As a rule of thumb, the longer the crank throw, the lower the redline. The accepted formula is 600,000/ crank throw in mm.
For the -B35 we have 600,000/84 = 7142 rpm. More on this in a moment.
For the -B36, 600,000 /86 = 6977 rpm
For the -B38, 600,000/90 = 6667 rpm.
When Paul Rosche designed the S38, it developed that the crankshaft had internal harmonics, known as eigenvalues, which showed up around 7250 rpm. Any and all mechanical contrivances have eigenvalues. Operate them in a manner where that harmonic shows up, much like a tuning fork, and the thing will eventually self-destruct.
To defeat these vibrations, we have harmonic balancers. Not a smart idea to remove them. It would appear that Dr. Rosche fully understood that going much shorter than 84 mm was an invitation to problems. Going longer began to push the rod ratio angulation issue.
Dinan did a run of 92 mm cranks in the 90s, this for his 3.9 liter stroker engines. There were about 48 of these cranks made. They are unobtanium. Some longer throw cranks exist, but these are one-offs.
Going longer on throws, we see 600,000/95 = 6315 rpm.
If PPM want s to go out to 98 mm, we get 600,000/98 = 6122 rpm. Somehow I don't think 6100 rpm redline is going to get the potential buyers for this engine all hot and bothered.
But assume for the moment you do get a 98 mm throw crank. Using a rod ratio of 1.50, this give a rod c-to-c distance of 147 mm. Which is nice, but doesn't leave sufficient distance for the upper half of the piston to support the rings, their lands and the piston crown.
Go to a rod ratio of 1.60 and the c-to-c distance becomes 156.8 mm.
The issues of casting rigidity and strength also come to the fore with the 98 mm stroke. The lower end walls of the crankcase are strong, but not infinitely so. Milling clearances for a 98 mm crank is going to weaken things significantly. This may be able to be addressed by laying in layers of cast-iron or low-hydrogen rod on the exterior of the block to increase (return) some measure of rigidity, then remachining all surfaces in a block prep machine to address any distortions from the machining/welding.
Now let's take a look at the cylinder-to-cylinder distance of 100 mm. This is an unalterable measurement. With the -B35's 93.4 mm bore, we have an intra-cylinder "siamesed" distance of 6.6 mm. Go larger, say out to the 94.6 distance on the -B38, that number goes down to 5.4 mm. This is very thin, especially so when one looks at the pressures within the combustion chamber/cylinder present on the power stroke. Try to go larger, and the odds of having the block casting crack are quite good.
But we are going to insist on getting to 4,200 cc displacement.
4,200/ 6 cylinders = 700 cc per hole.
Volume of a cylinder = pi * height * r^2. 3.1416 * 98 mm * square root of the bore diameter. Solve for bore diameter and we get a bore diameter of 95.3 mm. Wall thickness is now down to 4.7 mm.
Any one who is pushing displacement on this motor is not going to be babying it.
Care to guess how long before the block fails?
Possible solution.
Hog out the cylinders entirely. Replace with Darton sleeves. I tend to be skeptical if these sleeves, which will have a flat machined on them to mate up where the intra-bore "siameseing" is going to be necessary will be strong enough at a combined 4.7 mm wall thickness, but then, it's your dime.
I am here to tell you that the sleeves, plus the requisite engine building are not going to be done on your lunch money.
So if you want to be the first one on your block (nice pun. huh-huh-huh) to drop $7,500 plus-plus-plus on this deal, let us all know how it goes.
Dook, the proctology specialty within the surgical profession has found solutions for an enlarged lower end.Duke wrote:Mehhhhhhhhh.................I have 5.7 L of displacement. 4.2 L is a baby engine.Ken H. wrote:But we are going to insist on getting to 4,200 cc displacement.
They can also assist with Chronic Leakage.
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Coldswede
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Damn Ken! I love it when you have these lucid moments!Ken H. wrote:A few observations on going oversize with the M30.
The "base" casting is more or less identical to the S38.
The block has as its fundamental internal dimensions the 100 mm center-to-center distance for the cylinder bore centerlines.
The deck height from main bearing centerline to the top of the block is 217.5 mm.
These dimensions more or less "frame" what kind of displacement one can obtain.
To repeat a bit of the obvious, BMW built the S38B35 with an 84 mm stroke; stock bore is 93.4 mm.
The -B36 went up to 86 mm; bore is the same as the -B35--93.4 mm.
The -B38 went to 90 mm, but the bore got taken out to 94.6 mm.
The problems BMW experienced with the upsizing to the B=-B38 are well known, i.e., con rod bottom end bearing shells failing, bottom end failures destroying the block proper.
If one increases the length of the crank throws, it becomes necessary to shorten the c-to-c on the rods accordingly. One can decrease the wrist pin to piston crown distance only slightly. This to keep sufficient ring land height for strength and to allow the oil scraper ring to clear the wrist pin.
As one lengthens crank throw and shortens the con rods, there are problems with the angle of the rod to the cylinder bore. http://victorylibrary.com/mopar/rod-tech-c.htm.
This may be a bit technical, but what it says is that it is Not Wise to go much below a rod-to-stroke ratio of around 1.60. Yes, it can be done, but you will pay a price in terms of piston longevity.
Let's look at crank throws. As a rule of thumb, the longer the crank throw, the lower the redline. The accepted formula is 600,000/ crank throw in mm.
For the -B35 we have 600,000/84 = 7142 rpm. More on this in a moment.
For the -B36, 600,000 /86 = 6977 rpm
For the -B38, 600,000/90 = 6667 rpm.
When Paul Rosche designed the S38, it developed that the crankshaft had internal harmonics, known as eigenvalues, which showed up around 7250 rpm. Any and all mechanical contrivances have eigenvalues. Operate them in a manner where that harmonic shows up, much like a tuning fork, and the thing will eventually self-destruct.
To defeat these vibrations, we have harmonic balancers. Not a smart idea to remove them. It would appear that Dr. Rosche fully understood that going much shorter than 84 mm was an invitation to problems. Going longer began to push the rod ratio angulation issue.
Dinan did a run of 92 mm cranks in the 90s, this for his 3.9 liter stroker engines. There were about 48 of these cranks made. They are unobtanium. Some longer throw cranks exist, but these are one-offs.
Going longer on throws, we see 600,000/95 = 6315 rpm.
If PPM want s to go out to 98 mm, we get 600,000/98 = 6122 rpm. Somehow I don't think 6100 rpm redline is going to get the potential buyers for this engine all hot and bothered.
But assume for the moment you do get a 98 mm throw crank. Using a rod ratio of 1.50, this give a rod c-to-c distance of 147 mm. Which is nice, but doesn't leave sufficient distance for the upper half of the piston to support the rings, their lands and the piston crown.
Go to a rod ratio of 1.60 and the c-to-c distance becomes 156.8 mm.
The issues of casting rigidity and strength also come to the fore with the 98 mm stroke. The lower end walls of the crankcase are strong, but not infinitely so. Milling clearances for a 98 mm crank is going to weaken things significantly. This may be able to be addressed by laying in layers of cast-iron or low-hydrogen rod on the exterior of the block to increase (return) some measure of rigidity, then remachining all surfaces in a block prep machine to address any distortions from the machining/welding.
Now let's take a look at the cylinder-to-cylinder distance of 100 mm. This is an unalterable measurement. With the -B35's 93.4 mm bore, we have an intra-cylinder "siamesed" distance of 6.6 mm. Go larger, say out to the 94.6 distance on the -B38, that number goes down to 5.4 mm. This is very thin, especially so when one looks at the pressures within the combustion chamber/cylinder present on the power stroke. Try to go larger, and the odds of having the block casting crack are quite good.
But we are going to insist on getting to 4,200 cc displacement.
4,200/ 6 cylinders = 700 cc per hole.
Volume of a cylinder = pi * height * r^2. 3.1416 * 98 mm * square root of the bore diameter. Solve for bore diameter and we get a bore diameter of 95.3 mm. Wall thickness is now down to 4.7 mm.
Any one who is pushing displacement on this motor is not going to be babying it.
Care to guess how long before the block fails?
Possible solution.
Hog out the cylinders entirely. Replace with Darton sleeves. I tend to be skeptical if these sleeves, which will have a flat machined on them to mate up where the intra-bore "siameseing" is going to be necessary will be strong enough at a combined 4.7 mm wall thickness, but then, it's your dime.
I am here to tell you that the sleeves, plus the requisite engine building are not going to be done on your lunch money.
So if you want to be the first one on your block (nice pun. huh-huh-huh) to drop $7,500 plus-plus-plus on this deal, let us all know how it goes.
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marc79euro645
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