HIGH o2's and Detonation?

[dboosted1]

I was tuning today without the alky and my o2s were 850 yet I had 7* knock. Is this possible? Can it be false knock? Can a rich condition cause knock and if so is it as damaging? Thanks

PS. I do have a walbro, afpr, and all basic mods.

 

[TurboDave]

I wish people would get off the "tale" that somehow more fuel means less knock. NO sorry, it doesn't work that way at all.

Knock suppression is done with octane. That's what the octane rating system really is, the fuel's ability to supress knock.

Knock supression has nothing to do with the amount of fuel you're putting in. Although running WAY TOO lean can induce more knock.

 

[bruce]

Originally posted by TurboDave
I wish people would get off the "tale" that somehow more fuel means less knock. NO sorry, it doesn't work that way at all.

Knock suppression is done with octane. That's what the octane rating system really is, the fuel's ability to supress knock.

Knock supression has nothing to do with the amount of fuel you're putting in. Although running WAY TOO lean can induce more knock.

Oh really,
glad you're not tuning on my motor.
But all kiddin aside.
Feel free to do some reading at the NACA site about in cylinder cooling, and rethink what you've posted. For those of you not familiar with the NACA works, they actually did engine testing during WWII and generated the original paperwork that authors have rewritten and taken to expressing their feelings in rather then the actual research that was done, that documented how stuff really works.

If fuel had no purpose other then being fuel then you/ we/ everyone could run 14.7 at WOT.

You have to run richer then Stoich., for additional in cylinder cooling to keep the temps down, so the engine doesn't go into detonation.

Octane is only one element of the problem.

There's lots of serious reading material out there for understanding the in cylinder reactions. More then any one lil posting here will allow for.

Never mind raising the issue of preignition.

 

[Carolinaturbot6]

http://www.zhome.com/ZCMnL/PICS/detonation/detonation.html

dboosted1, some good reading on detonation is at the link above. Steve W. had posted the link earlier in the year. Pretty interesting stuff.

 

[bruce]

Originally posted by Carolinaturbot6
http://www.zhome.com/ZCMnL/PICS/detonation/detonation.html

dboosted1, some good reading on detonation is at the link above. Steve W. had posted the link earlier in the year. Pretty interesting stuff.

6. Monitor air/fuel ratio and use the cooling effect of additional fuel in your tuning.


You'll find this repeated, again and again, as you research tuning.

Also, remember there are different operating temps in an engine. Actual chamber temps., coolant temps, oil temp., etc.

Just as a case in point,
take lean cruise.
You're **robbing** the engine of cooler operating chamber temp.. So there will be more heat generated since you running just enough fuel for combustion, but nothing towards cooling the chamber. Just for grins, try running say a 13.5 AFR at cruise with the corresponding reduction in timing, and watch your oil pressure on a real hot day.

 

[Ken Cunningham]

I have gotten knock counts and retarded timing at some pretty high O2 levels: like 900-980. Maybe I should tell my engine about what all the research says...