You'd have to drive this car pretty hard to need the VDC

 

Damn right - These cars are heavy but they still grip really well. In a snowy area VDC is an awesome addition. From what ive heard at the local dealer, it essentially gives you LSD's all round by braking whatever individual wheel is slipping.

 

Thought hard about a VDC but seemed a potentially complicated issue if it ever malfunctioned

 

Really its just ABS with a smarter computer.

I know I'm a little late here, (or a lot, oh well) but I've got an 01 Bean w/the H6 also. As for VDC I can't really say b/c I haven't driven it, but I CAN say that I haven't needed it. I routinely drive back and forth from CT to VT in the winters on weekends to go skiing, and even in the worst snow storms, I've never felt I needed anything more than what my car has got.

As for premium fuel issue, I feel it IS neccesary, and I really only say that because these H6 motors have 10.5:1 compression ratio's. I've always been told (granted, it may not be totally accurate - but it's what I've always known) that anything over 10:1 is going to need to run 92 or higher octane to prevent pre-ignition...which will kill your engine fast! For anyone unsure of what that is, the shortest answer i can give you, is that octane is resistance of fuel to ignite, and under higher compression (or higher temperatures) lower octane fuel has a tendancy to ignite before your engine is ready - before your plugs fire!

I'm not an expert here, but am very competent with a wrench, and that explaination has always been enough for me to run 93 in my car.

 

anyone feel different, with a better reason than I've always been told?

If the spark can be retarded arbitrarily far, the octane could be arbitrarily low. The question I guess would be can the computer retard the spark sufficiently far?

 

I think it can, and I don't worry about running 87 (heve never heard pinging or knocking), but I don't because it runs so much better on the higher-octane stuff.

 

Pre-ignition is devastating when it occurs early in the compression stroke, but is not caused by too low an octane, really, it's caused by hot bits in the cylinder igniting the charge early in the compression stroke. It can bend a rod very quickly if it happens early enough in the stroke. The hot bits can be carbon or a plug that's too hot.

 

Spark knock or detonation is the term here.

 

The octane rating of the fuel really has only a little to do with the ignitability of the fuel, if the fuel ignitability was low enough that 10 or 11 or even 12:1 compression were enough to ignite it, we'd all be seeing cetane ratings on gasoline pumps, as opposed to just octane ratings (and unlike a diesel, low cetaine ratings would be what we wanted).

 

Dave

Edited August 4, 200916 yr by CNY_Dave

CraigC, one cannot base octane choice on compression ratio alone. Your rule of thumb may be very prudent when there is no other information available at all, and I'd agree in a very general way that a compression ratio in that range is historically been reserved for premium-fuel cars.

 

However, it's actually cylinder compression or pressure rather than compression ratio that determines how resistant to pre-ignition your fuel must be. And, compression ratio is not the only thing that determines compression (or cylinder pressure if you prefer).

CraigC, one cannot base octane choice on compression ratio alone. Your rule of thumb may be very prudent when there is no other information available at all, and I'd agree in a very general way that a compression ratio in that range is historically been reserved for premium-fuel cars.

 

However, it's actually cylinder compression or pressure rather than compression ratio that determines how resistant to pre-ignition your fuel must be. And, compression ratio is not the only thing that determines compression (or cylinder pressure if you prefer).

 

A discussion of static vs dynamic compression ratios, cylinder filling, can porting be far behind, alright, this should be good for 7-8 pages!

 

Especially since the H6 has that variable valve timing widget...

 

Dave

According to Wikipedia, VDC is very soon going to be required on all new cars:

http://en.wikipedia.org/wiki/Electronic_stability_control

(scroll down to 'Laws')

A discussion of static vs dynamic compression ratios, cylinder filling, can porting be far behind, alright, this should be good for 7-8 pages!

 

Especially since the H6 has that variable valve timing widget...

 

Dave

 

 

you left out shape of the piston, piston cooling, shape of the cylinder head chamber, atomization of fuel (well that can be covered under porting), wether the moon is aligned with mars...

 

 

 

nipper