Tuesday, July 20, 2010

rear bumper...motorsports styled...

this is an option for the rear bumper...given the motorsports front end i am considering...




i'm not sure i like this as  much as the sheet metal parts i have been considering...but needed a parking space for the image...


rear sheet metal on a european 320...notice the 4 cylinder dual exhaust...and the european license plate holder...

source:  http://www.dtmfiberwerkz.com/product_info.php?products_id=425&osCsid=kvig8lln990onpm6lv0uv1q1e0

Monday, July 12, 2010

bmw model designations....

this was always so confusing to me...and recently i saw someone on the forums that asked the question i had once asked...it was fun to see someone else trying to understand what ended up being a really simple thing...
Originally Posted by mdwman View Post
\\what do the different designations (318, 320, 323, 325) represent? Mark


the 3 is for the series in the lineup of BMWs. the others being the 1, 5, 6, 7, Z, ect.

the next group ie; 23, 18 ect. is the size of the engine in liters. 23 is a 2.3 liter 6 cylinder and the 18 is a 1.8 liter 4 banger.

the next letter tells more about the car. if there is a "I", it's means fuel injected, "CSL" is coupe sport lightweight, "e" is something greek? for eta or low rpm - high torque.

if there is a "s" after that, it's has a sport package. a "x" is all wheel drive.

Sunday, July 11, 2010

Flywheel Lightened?? (part 3)

continued conversation from the e21 forum...

The purpose of a flywheel is to increase the polar moment of the rotating assembly. However, a piston engine's instantaneous output shaft speed varies throughout any given rotation due to the variations in instantaneous driving torques produced by the engine's intermittent combustion events. The increased movement of inertia provided by the flywheel's mass helps to smooth out these speed variations and the torsional vibrations that result from the angular accelerations/decelerations.

An engine with fewer cylinders will require a flywheel with a proportionally greater mass than an engine with a large number of cylinders. And with turbocharged engines, with their higher peak cycle pressures, will usually want a heavier flywheel than a N/A engine.

Lightened flywheel-

Better w/
-more cylinders
-Higher (numerically) rear gears
-Normally aspirated
-lighter car


Me? I really wouldn't want to lighten it ....Just my .02s....



My theory on longevity- On a 4 cylinder engine-a heavier flywheel would help out smoothing the shock on the rotating mass...However, if you're running a NA engine with low compression, I think it's a moot point.

Richard454

Flywheel Lightened?? (part 2)

the thoughts continue...

"When it comes to going fast, many concentrate on producing more power at the engine. Unfortunately, any experienced racer can tell you it is not the power at the crankshaft which propels the vehicle. In actuality, it is the percentage of this crankshaft power which makes it to the ground that is the true measure of performance


The Physics: In efforts to improve the efficiency, racers have experimented with everything from ultra-light flywheels to lightweight, low inertia wheel-and-tire combinations. In general, their attempts have improved a vehicle�s ability to accelerate and put power to the ground. In some applications, the side effects of an ultra-light flywheel negate the benefits. For example, drag-racing vehicles depend on a near-stock-weight or heavier flywheel to store the necessary amount of energy for an explosive launch. Since the launch is the most critical aspect of a drag race, most racers can�t afford to give up launch quality by using a lightened flywheel to pick up a slight improvement in acceleration. Of course, other forms of racing, which are less dependent on acceleration from a dead stop, can benefit from the use of lightweight flywheel setups. In contrast to lightweight flywheels, a lightweight wheel-and-tire combination has no real drawbacks as long as enough wheel strength is maintained..."


RESPONSE TO THE QUESTIONS ABOVE:   It also depends on how an engine is balanced, internally or externally. I am under the impression that BMW balances the rotating assembly separate from the flywheel and that the flywheel is then zero balanced (much like a chevy small block). There are balancing holes drilled on one of the counter weights of the crank (I believe the rear), and there are also balancing holes drilled on the flywheel. If they did them together, they would only need to drill balance holes at one point (the flywheel). Conversely, a big block is externally balanced, so the rotating assembly is balanced by machining the flywheel. Your clutch assembly should be "zero" balanced in much the same way so that it can be replaced without affecting engine balance, but realize that even this balance is not perfect so any time you replace your clutch, there is potential for affecting the balance of the motor. Center force dual friction clutches are notorious for causing major balance issues when the flyweights get stuck and don't slide out on the diaphragm. I broke my pressure plate strapping bands 300 miles from home in 2007 and the pressure plate disc was off center by over 1/8". It vibrated so bad you couldn't see out of the rear view mirror clearly. I made it home, replaced the clutch and the motor was fine. Over time, sure, you might wear the rear main bearing prematurely with an extreme case of imbalance like that, but a zero balanced flywheel will not cause an issue. Long story short, you're worrying WAY too much about this. Of course, any time you lighten a flywheel, it should be zero balanced.

My thoughts on an lightened flywheel on an m10: If you like spirited driving, you won't regret a lightened flywheel. We're only talking going from 15 lbs to 13 lbs, which is not enough difference to affect drivability, but is enough to actually make the car faster. I'm running an 8 lb aluminum flywheel with a MUCH lower moment of inertia than a lightened stock flywheel and I love it. It makes rev matches and gear changes soo nice.

the downsides to a lightened flywheel are less rotational inertia to get the car moving from a stand still, slightly harder to maintain steady speed on the highway, slightly worse mileage due to less rotational inertia, and maybe a slightly less smooth engine.

GM has been using aluminum drive shafts for years, most likely in an effort to minimize fleet average fuel consumption by .001%. On an e21 with a stock flywheel? Waste of money. Focus on lightweight wheels and the flywheel as they have a much great affect on rotational inertia and acceleration.

Saturday, July 10, 2010

lightened flywheels...

 If you want more acceleration, especially in lower gears, lightening crankshafts and flywheels is a good idea...it will NOT give you any more power, so top speed, will remain unchanged.  It WILL allow more power to reach the wheels under accelerating conditions because less energy is being wasted accelerating the engines rotating parts up to speed!...it may also result in a slightly lumpier idle, but will give faster throttle response when you blip the pedal!  Much like a motorcycle, because they have no flywheels....the gains are quite small and expensive but like all engine tuning you have to decide what you are trying to achieve....and everything should be a good balance of modifications that matches...The job of the flywheel is to smooth out firing pulses, stop vibration harmonics, and torsional twist. The most economical way for the factory to do this was to make the flywheel the weight it is stock.

Quote:
Originally Posted by 340i
View Post
so the flywheel is weaker than it was before, but it will presumably be getting more abuse? is that safe?

i dont want to freak you out, but have you seen what happens to flywheels when they break? byebye feet...

i wonder about this...and while a flywheel flying apart isn't my real concern...engine performance and engine longevity is...i have a new m10 rebuild and a fresh transmission rebuild but i have yet to put in the clutch kit and flywheel togther...i had the flywheel resurfaced but not lightened...i considered an aluminum flywheel but after talking with a lot of trusted friends...the conversation always turns toward comments about manufacture's proportions and engine balance, engine longevity, and the money spent on engineering and design by the factory...i know that the racing circuit has successfully lightened flywheels for years...but in the end i DID NOT lighten my flywheel YET...

i am seriously wondering what to do about it...should i...or shouldn't i...that is my question...i put a 292 cam in the engine so i expect that to increase some performance...but for a summer DD where is the "end point" of modifications is what i'm wondering...where does the line between performance enhancements and engine longevity meet?...is lightening a flywheel to much? if so...how much is too much lightening...what does experience say? i don't know these answers and i am not sure where to find them...i have discussed this with my machine shop and IE...and neither answer the question...at least the way i want them too...probably because there are so many possible variables...

any thoughts on this?


Consider The Following:   if we are serious about lightning bits and pieces to get a free revving engine what about a carbon fiber drive shaft?...it would rotationally flex more that the metal counterparts and reduce strain on the engine . . .if a metal drive shaft breaks parts can be thrown through the car!...a carbon fiber drive shaft is stronger but if it does break...it would generally only leave a 'broom' into 'harmless' fibers and little damage will be done to the car...and the same effect is achieved...lthough the uninitiated might only see the obvious lightweight advantage offered by a carbon-fiber driveshaft, there is areally a great deal more to it than simple weight reduction...along with being roughly 50 percent lighter than a steel unit, carbon-fiber driveshafts offer greater fatigue life, superior vibration damping and a much higher critical speed...the most obvious benefit of carbon fiber is its weight...unlike other weight-reduction measures, such as fiberglass hoods or ditching the A/C, carbon-fiber driveshafts actually aid acceleration, and deceleration...

this is just a theoretical question is am posing...i am highly suspect that using a lightened flywheel with a stock, non counter-weighted crankshaft requires using an equalizer pulley to dampen the harmonics, bending, torsional twist and vibration...without doing so would seem to cause premature case, piston, rod bearing and even possible crank damage...particularly, at high rev's which is the ultimate reason intended with lighten a flywheel...between a lightened flywheel, and lumpier cam in the 320i i am restoring...drive ability is my concern...while not actually increasing speed...it would increase response...but at the cost of consistent flow through acceleration and deceleration...not advisable for a summer season daily driver...

pistons, cams, and RPM's

6000 rpms...that is 100 times a second...i know that is nothing compared to chip speeds i suppose but .... we are talking cams, cranks, pistons...mechanical items those pistons above moving that fast...it is mind-boggling to me...this is a great example of the height of the mechanized society...and the beginning of the information based society...i love that....