Is Premium gas necessary?

[SR5]

There could be a difference in sulphur content with the octane rating.

In Australia, the Fuel Quality Standards Act 2000 set a maximum of 150ppm sulphur for regular unleaded since 2005 and 50ppm for premium unleaded since 2008.

I believe lower sulphur is better, less acid formation I think. Probably not a problem unless you run a low SAPS oil. In Europe I think they have 10 ppm sulphur fuel. Oz was 500ppm in the bad old days, better now, but not as good as Europe.

 

[Mik]

Originally Posted By: David_g

I'll assume that like your C14, the ZX14 has VVT


Wrong assumption... ZX-14 has no VVT...

 

[eddy21]

Originally Posted By: JetStar
Originally Posted By: pbm
While looking through the owners manual of my newly acquired 1998 Virago I noticed that 'Regular' (86RON) gasoline is spec'd. I always thought that Premium was called for in motorcycles but now I'm wondering if it's necessary.
I know that running Premium in a car that calls for Regular is a waste and I'm wondering if the same is true here?

Opinions wanted....thanks.


Use what your manual tells you. My FZ1 has 11.5:1 compression and never pings on regular. I think it depends on combustion chamber design and perhaps cooling more than anything else. If your bike is in a proper state of tune, you'll be fine.


A smaller bore is less susceptible to detonation.

 

[Cardenio327]

Originally Posted By: SR5
There could be a difference in sulphur content with the octane rating.

In Australia, the Fuel Quality Standards Act 2000 set a maximum of 150ppm sulphur for regular unleaded since 2005 and 50ppm for premium unleaded since 2008.

I believe lower sulphur is better, less acid formation I think. Probably not a problem unless you run a low SAPS oil. In Europe I think they have 10 ppm sulphur fuel. Oz was 500ppm in the bad old days, better now, but not as good as Europe.


In Mexico, yes: Premium (92 PON) supposedly has 88% less sulfur than Magna (87 PON). Premium supposedly has more additives than Magna too. Spark plug insulators run on Premium are dark red as opposed to yellowish-light red on Magna, supporting Pemex's claim to more additives.

I used to recommend my customers use Magna unless their manual specced Premium. Now I recommend Premium to all my customers to reduce TBN depletion, catylytic convertor damage, and injector spray pattern fouling.

On octane numbers MON (aviation) tests 8-10 points less than RON (automotive except North America). Pumps in Canada, USA, and Mexico display PON (pump octane number), which is an average of MON and RON, hence R+M/2.

If the OP's bike specs 86 RON, then all that is needed as a minimum octane for the OP's location is 81 or 82 PON declared at the pump. If the OP were to fuel the bike at an airport, he would be looking for a minimum of 76 to 78 MON at the pump.

 

[CT8]

Originally Posted By: HerrStig
Originally Posted By: FastGame
Originally Posted By: HerrStig
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.
I don't see how VVT can control combustion chamber volume. SAAB tried a variable volume combustion chamber in an I4 but it required a hinge on one side of the head. Didn't work out well.


http://www.enginebuildermag.com/2014/01/the-inner-workings-of-variable-valve-timing/

Even my old KZ 1000 compression ratio is dependent on the cam profile.
How does cam profile relate to the diameter of the piston and the length of the connecting rod in any way which could change compression ratio, which is calculated based on those measurements, and not on things "bleeding off"?
The same could be said of throttle opening or whether or not the air filter were clogged.
The camshaft does effect the compression. You have never built or worked with high performance engines I see.The compression ratio doesn't start until all the valves are closed. you are referring to a static compression ratio.

 

[HerrStig]

I always enjoy being told what I do or don't know. When manufacturers start publishing the "really really" compression ratio as part of their engine specs I'll be interested.

 

[FastGame]

Since this thread I've been using mid grade 89 in the C-14. So far all is well but I don't live in the upper RPM's or lug the engine.

 

[eddy21]

Originally Posted By: David_g
Originally Posted By: FastGame
My Concours 14 calls for 91 minimum octane because of the variable valve timing. I don't know how high the compression gets during normal riding but better safe than sorry.

The link you provided refers to "effective compression ratio" which I expect is what WANG called "dynamic compression ratio". Without qualifiers, "compression ratio" is what WANG called "static compression ratio", and it is not dependent on valve timing.

Dynamic compression ratio won't be higher than the actual (static) compression ratio of the engine. So if you wonder how high it can go, well it can't go any higher than that. If you look up numbers for that engine maybe you'd get the static compression ratio.

Engines especially high performance can fill the combustion chamber above atmospheric pressure through exhaust pressure waves and valve timind etc. This is causing increased cylinder pressures.