Shaun said:
Kenntona I didn't know you studied at least somewhat, engine design. wah you know everything from engines to women to plato. very impressive!!!
Bro, my learning curve has just increased its gradient somewhat, after these many hours of surfing the BMW.SG forum. This follows some lifelong learning philosophy as advocated by some social aristocrats. And I do browse through some bimmer magazines while I am sitting on that toilet bowl of mine, contemplating on some aesthetic mods. When constipated, I will read those technical articles.
Still, all these would just be a minuscule effort in stark comparison to your depth and breadth of technical knowledge, probably acquired through extensive experience and intensive research on the academia of automobiles. A perfect analogy would be a pre-school starter versus a postgraduate candidate. Hence I would not dare to accept your compliment (“wah you know everything from engines to women to plato”) with grace. I would not even dare to think I know anything more than selecting the octane level of gasoline to pump at the cheapest petrol station within a 5-km radius around my place. In fact, quite the contrary, I know nuts about automobiles.
But on women and philosophy, perhaps I could give you a run for your money. Will share with you when you are back.
Shaun said:
regarding the extra cams, gears, and drives on the V6, what are your thoughts on single cam V6s and how it would be implemented?
I’m raw on this, but I’d supposed you are talking about single-cam pushrod in a V-configuration? You’d probably know this better than me, since you have a VR6 engine to toy with…… Please enlighten if I’ve shamed myself in sharing my humble thoughts……
The main reason to use twin cams is to allow for more intake and exhaust valves. Intuitively, more valves means that intake and exhaust gases can flow more freely because there are more openings for them to flow through. This increases the power of the engine. But those DOHC heads are so large that you will need a wider engine bay to fit the engine. Yes, they can rev to higher speeds, and those higher revs produce a higher peak power output. But I’ll bet you will prefer a low revving high torque engine that can run down to idle in top gear and still accelerate away in that same top gear. That will be the engine that most people want.
Back to the single cam. How does it work in comparison to double cam? Take the pushrod single cam, which has overall less valve surface and smaller lift and shorter duration. There is going to be relatively low power made at high revolutions because eventually little air/fuel mixture will be getting into the cylinders with the speed the engine is going. Also, the longer stroke does not bode well for high revving. So to compensate for this, a pushrod engine will have smaller bores and longer strokes to allow for more air/fuel mixture at low rpms which means more low end power, especially torque. The twin cam engine on the otherhand with its higher lift and longer duration is bad for torque production mainly due to too much overlap, and does not get peak performance till higher revs because then the crank is already rotating and the longer duration allows more air/fuel mixture to enter the cylinders at the high revs. The theory is that more valves = more air = more power. Don’t flame me if I sounded ignorant on this.
To be fair, a multi-valve engine with a single cam arrangement is just as efficient as a double cam one, although the trend is to use multi-valve engines with individual camshafts controlling the inlet and exhaust valves. There is also a concern on the space constraints with the cam-in-block design of the pushrod. But on a financial note, there is a cost factor against the twin cam – it is more costly to produce a twin-cam engine since there are more moving parts and more material is used.
On implementation, you should know the VR6 engine, constructed like an in-line engine. The two banks are merged into a single cylinder block with a single cylinder head housing the valve gears for all 6 cylinders. In contrast, a conventional V6 consists of 2 blocks and 2 heads. Thus the VR6 is not only smaller, but also lighter and cheaper to be built. First G VR6 has 2 valves per cylinder, single overhead cam serving each bank just like any conventional 2-valve V6, although the 2 camshafts are so close that they look as if a twin-cam design.
Shaun said:
what levels of applicability of the cooling statements about the V6, do you see with regard to the two main cooling options. Do you not think it is lopsided?
Not sure what you are getting at, but the V6 engine has one bank of cylinders mirroring another bank. As far as cooling is concerned, the air intake has to be from the center of the V and exhaust pumps out from outside of the V, since the inside of V cannot accommodate very hot exhaust pipes. Because of the closely-packed adjacent cylinders, there is no space for induction / exhaust pipes running to the same side. Induction manifolds take place at the top of the engine thus waste no space, but the hot exhaust pipes engage a lot of space (or length) of the car, especially is a certain clearance should be provided to avoid overheating to surrounding components. In a design sense, it is lopsided.
Shaun said:
been trying to figure out the balance/out of balance (primary and secondary, couples if any) for 72 vs 90 deg V10s. Can you help? A paint or freehand sketch will help... only takes 5 minutes for guys like you. Firing order suggestions assuming no space for crossovers? can?
Wah, bro, give an inch you wanna take a foot? Just kidding. But this takes an engineer. Me? Just a forumer who loves my car, make friends here, and enjoy playing Grudge Match or sharing interesting stuff with my fellow brothers. Just a PSLE graduate with an interest and enthusiasm to learn more about my car. Not really having an ambition to take my Ph.D in Automobile Design. Not a car saleman, nor a promoter of any particular brand of products or services either. So, save up your bullets, and shoot someone else instead. No point testing me on Ph.D stuff. No holds barred. Cheers.
Back to the Grudge Match:
Be a Big Fish in a Small Pond - thus pushing your weight around; or
Be a Small Fish in the Ocean - with more opportunities abound?
:laughing: 
