Does anybody know why most cars that require
"premium fuel only" or "92 cotane minimum" always say somewhere in the manual that "lower octane fuel may be used with decreased preformance". But in 2 strokes you MUST use the right octane or you can kiss your pistons goodbye. Don't 4 strokes detonate also??? And why in cars like ,for instance, the viper do you HAVE to run high octane??

Yes, 4 strokes do detonate. The difference is if there is an onboard computer that retards the timing when you use low octane fuel. Many high performance cars have this. Even my sons Polaris ProX440 snowmobile has a feature that you can select to run it on lower octane if you switch the ignition over to a different position.

RonJon,
You're actually referring to predetonation, not detonation. Modern cars (low and high performance) have knock sensors that can "hear" predetonation and will reduce the timing advance to help eliminate the predetonation. There are more factors to look at than just compression and boost, like cylinder head temperature and intake air temperature, but this could erupt into a very long and detailed post if I tried to explain it all.

You can use a lower than specified octane level, but you must do so at reduced load, or you're going to melt something down if the predetonation is severe enough. In [modern] cars, the computer will detect the predetonation and reduce the ignition advance, thus reducing power output (and protecting the engine)

The timing retard fuction, whether it is automatic (like in automobiles) or manual (like VOODOO's son's snowmobile) has only so much authority to reduce the timing advance and protect the engine.

For instance, a Viper would be fine putting around town on el cheapo 87 octane. Drive the **** out of it on a racetrack, and the engine may be in trouble. Likewise, jack up the compression enough and the computer may not be able to retard the timing enough to protect the engine--even with 92 octane pump gas!

Well is there any way to incorporate this tachnology into 2 or 4 stroke watercraft?
--OH...wait a minute....that would meen that PWC owners would not get to pay the watercraft makers thousands of dollars to fix or replace blown motors that could have been saved by this system you speek of. DARN! And I was just getting excited.
Come on all you techies out there,think about it.....:what is the single thing MOST people on this forum for the loss of thier engine??:...DETONATION!
Detonation this...Detonation that! Even the new 1300's are doing it with relatively modreate increases in compression. Or what if you have a ski w/ stock compression and you get screwed w/ bad pump gas?? Who knows how reliable gas from the pump is?....Anyone???.....EXACTLY!!...You don't.

generally speaking, its the cost which holds back the technology... for a true EFI system, with all the air sensors and other sensors which cost a butt load of money... its just would not be able to spread it over a relativley small market in comparison to the millions upon millions of cars sold... the price of a PWC would be very high... as if its not already high now...

now this is just my view point...

you are correct about the fact that PWC seem to have more maintainence then they ought to have... but as the old saying goes... a vessle is a bottomless pit in which one will constantly pour money into... its just the nature of the beast... engines dont fair well in a aqeous environment even worst, marine... lots of care is required to keep it in good running condition.

furthermore these PWC are constantly pegged at WOT, and even larger boats outboards and inboards engines suffer a short life spand if they are constantly pegged at 5,6,7 grand RPM's... your normal automobiles are not pegges at this level for long durations of time, not to mention the stress loads of in and out of the water... its just brutal on the engines... they are in essence race engines and race engines require lots of maintenance... etc.

just how it is with water toys.

I don't know about other brands but I do Know Honda has a knock sensor. It recommends 91 but states min 86. You can tell the difference in the gas by the performance.

Another thing to think about...you can hear the predetonation in a car (even with loud exhaust) and you can back off. I don't think you could hear it on a PWC. Also, in most cars (street driving), you're not going to be full throttle for several minutes, like you WILL be on a PWC. Like amoney said, our PWC engines are treated like race engines.

my friend is trying to develop something simmilar to what everyone is talking about for his race boat.

From what i remember, we talked a ford ignition that can send the correct signals to power a 2 stroke. I remember him saying that it had to be changed slightly, but in theory it he said it should definately work. I don't think it would allow a motor that needs 105 race gas to run on 93, but it would have been cool to test.

not sure if he got into making one. was a cool idea though.