Sticky
04-20-2010, 02:28 AM
I wrote a fairly detailed article comparing the stroker options for the M3. Here is the full article: http://www.bimmerboost.com/showthread.php?1353-S65-Stroker-Comparison-Dinan-vs.-RDsport-and-the-History-Reason-for-Stroking
Since it is pretty long I'll include what I can here:
Many people love the S65 in naturally aspirated form and rightfully so. This is an absolutely amazing motor with great response in NA form. For those that want the maximum possible naturally aspirated gain, the best results will come with a built motor that has increased bore and stroke. Most people are familiar with the two main options in this area which are Dinan and RDsport. Those that truly want to stay NA and desire much more power should definitely consider either of the aforementioned but also consider a custom built option.
Why a stroker?
Well, why not? The stock E92 M3 S65 has a bore and stroke of 92mm x 75.2mm. To paraphrase Steve Dinan, the motor is just begging for more stroke. The stock piston speed at 8250 rpm is 4070 feet per minute. The stroke can be raised 7-8mm relatively easily. 83mm at 8250 produces 4493 feet per minute, well within the high end of the most stressed naturally aspirated motors. Half a liter of displacement is just sitting there waiting to be tapped.
If BMW could have done it from the factory but they did not, that must mean it is a bad idea or they would have done it, right?
No, not right. BMW is very crafty, very thorough, and they definitely know what they are doing. The stroke was going to be 75.2mm no matter what as the S85 V10 in the M5 already decided it. Why did BMW give themselves this room in the S85 and S65? Well, they gave themselves a cushion if they needed it or the market demanded it. Some of you might remember early rumors of the M6 having a 5.5 liter V10 and 550 horsepower.
These rumors had a strong basis in reality as insiders knew BMW could raise the displacement of the S85 to 5.5 liters at any time they wanted to. The M5 CSL that was shown happened to be a 5.5 liter 550-580 hp S85.
http://www.bmwblog.com/wp-content/uploads/BMW-5Series-281099134475341600x1060.jpg
BMW did not just get a new crank and new rods for one vehicle. I am speculating they already had this sitting around when they toyed with the idea of giving the M6 5.5 liters from the outset. The fact of the matter is the M5 and M6 received the same displacement to keep costs low. The same thing happened to the M3, bore and stroke was forced due to the M5/M6.
However, after the M5 CSL was announced and tested to honor the 25th anniversary of the M5, the M3 GTS was announced. What was the displacement? 4.4 liters, it used the exact same stroke as the M5 CSL test car needed to hit 5.5 liters on the V10. Coincidence? Not at all, BMW had this all planned out way in advance. Not only did they intend to carry over the stroke and the rod specs from the M5 CSL to the GTS, they gave themselves plenty of room in the S85 and S65 should they need to turn out higher performance models (CSL, GTS.) The competition never forced BMW's hand as the M3 is still the top of its class and the E60 M5 certainly was and arguably still is. Also, with the CSL and GTS, there certainly was a bit of internal pride presented through these models and BMW was showing the world they could still turn out top NA motors... but they now had to be environmentally responsible.
The S65 and S85 had the foundation to evolve for years if necessary. Unfortunately, we will never see these motors realize their full potential in official production as they have been abandoned for obvious reasons. However, this is exactly where the aftermarket comes in.
Dinan vs. RDsport
http://www.dinancars.com/store/files/master/Dinanpics/E90_E92_E93/E90%2092%20M3/S65-Stroker-Motor-rear-web.jpg
Cost:
Dinan has their stroker motor listed at $24,999 as of right now. It was listed at $22,999 at one point and it was also listed above $25k at one point. The price has jumped around a bit and I am not surprised at all. Dinan is gauging how much they can get in todays market which is rough to say the least. There is absolutely no reason to pay $24,999 especially once they showed that they would take $23k. Additionally, Dinan can't make the argument that there is significant R&D to recover when he already admitted to the V10 parts carrying over. He did not need to test a new setup or use different pistons and rods. He is just applying everything from the V10 here except the crank (although the crank is for the same stroke.) Dinan also does not include install in the price or any supplemental mods which does give the user more flexibility in choosing who their supporting mods come from. You don't have to bundle the Dinan exhaust, intake, or throttle bodies. It ends up being less than the RDsport retail but more than what the RDsport motor can actually be purchased for when everything is tallied up.
Continued: Here (http://www.bimmerboost.com/showthread.php?1353-S65-Stroker-Comparison-Dinan-vs.-RDsport-and-the-History-Reason-for-Stroking)
Since it is pretty long I'll include what I can here:
Many people love the S65 in naturally aspirated form and rightfully so. This is an absolutely amazing motor with great response in NA form. For those that want the maximum possible naturally aspirated gain, the best results will come with a built motor that has increased bore and stroke. Most people are familiar with the two main options in this area which are Dinan and RDsport. Those that truly want to stay NA and desire much more power should definitely consider either of the aforementioned but also consider a custom built option.
Why a stroker?
Well, why not? The stock E92 M3 S65 has a bore and stroke of 92mm x 75.2mm. To paraphrase Steve Dinan, the motor is just begging for more stroke. The stock piston speed at 8250 rpm is 4070 feet per minute. The stroke can be raised 7-8mm relatively easily. 83mm at 8250 produces 4493 feet per minute, well within the high end of the most stressed naturally aspirated motors. Half a liter of displacement is just sitting there waiting to be tapped.
If BMW could have done it from the factory but they did not, that must mean it is a bad idea or they would have done it, right?
No, not right. BMW is very crafty, very thorough, and they definitely know what they are doing. The stroke was going to be 75.2mm no matter what as the S85 V10 in the M5 already decided it. Why did BMW give themselves this room in the S85 and S65? Well, they gave themselves a cushion if they needed it or the market demanded it. Some of you might remember early rumors of the M6 having a 5.5 liter V10 and 550 horsepower.
These rumors had a strong basis in reality as insiders knew BMW could raise the displacement of the S85 to 5.5 liters at any time they wanted to. The M5 CSL that was shown happened to be a 5.5 liter 550-580 hp S85.
http://www.bmwblog.com/wp-content/uploads/BMW-5Series-281099134475341600x1060.jpg
BMW did not just get a new crank and new rods for one vehicle. I am speculating they already had this sitting around when they toyed with the idea of giving the M6 5.5 liters from the outset. The fact of the matter is the M5 and M6 received the same displacement to keep costs low. The same thing happened to the M3, bore and stroke was forced due to the M5/M6.
However, after the M5 CSL was announced and tested to honor the 25th anniversary of the M5, the M3 GTS was announced. What was the displacement? 4.4 liters, it used the exact same stroke as the M5 CSL test car needed to hit 5.5 liters on the V10. Coincidence? Not at all, BMW had this all planned out way in advance. Not only did they intend to carry over the stroke and the rod specs from the M5 CSL to the GTS, they gave themselves plenty of room in the S85 and S65 should they need to turn out higher performance models (CSL, GTS.) The competition never forced BMW's hand as the M3 is still the top of its class and the E60 M5 certainly was and arguably still is. Also, with the CSL and GTS, there certainly was a bit of internal pride presented through these models and BMW was showing the world they could still turn out top NA motors... but they now had to be environmentally responsible.
The S65 and S85 had the foundation to evolve for years if necessary. Unfortunately, we will never see these motors realize their full potential in official production as they have been abandoned for obvious reasons. However, this is exactly where the aftermarket comes in.
Dinan vs. RDsport
http://www.dinancars.com/store/files/master/Dinanpics/E90_E92_E93/E90%2092%20M3/S65-Stroker-Motor-rear-web.jpg
Cost:
Dinan has their stroker motor listed at $24,999 as of right now. It was listed at $22,999 at one point and it was also listed above $25k at one point. The price has jumped around a bit and I am not surprised at all. Dinan is gauging how much they can get in todays market which is rough to say the least. There is absolutely no reason to pay $24,999 especially once they showed that they would take $23k. Additionally, Dinan can't make the argument that there is significant R&D to recover when he already admitted to the V10 parts carrying over. He did not need to test a new setup or use different pistons and rods. He is just applying everything from the V10 here except the crank (although the crank is for the same stroke.) Dinan also does not include install in the price or any supplemental mods which does give the user more flexibility in choosing who their supporting mods come from. You don't have to bundle the Dinan exhaust, intake, or throttle bodies. It ends up being less than the RDsport retail but more than what the RDsport motor can actually be purchased for when everything is tallied up.
Continued: Here (http://www.bimmerboost.com/showthread.php?1353-S65-Stroker-Comparison-Dinan-vs.-RDsport-and-the-History-Reason-for-Stroking)