that'* why i spend my time here as well. the first online forum that i became a part of, i got addicted too, even though i hated the people on it - they were always yelling at each other, and conversations quickly broke down to sounding like two 14 year olds were arguing back and forth...

*sniffs*

i love it here!

Holy jebus this thing exploded! All I had to do was type in caps? haha

OK sheesh I'm gonna take a few pieces and address those for the moment, I have to go to work soon

mkaake, Buzz38 - Detonation is not good, but it doesn't mean instant failure. Thats pre-ignition which can be caused by excessive and audible detonation. The key is that the PCM can re-learn a spark curve that will prevent detonation. If you consistantly get knock when you accelerate the computer will compensate until there is no more knock, then store that information.

http://www.autoshop101.com/forms/h59.pdf --- Page 2


Assuming GreenMacine remembers what he read in the manual, why would Pontiac only say that acceleration will suffer and not "HOLY CRAP, YOU'LL DESTROY YOUR ENGINE WITH 87 YOU IRRESPONSIBLE FREAK!" haha..but seriously? It doesn't seem the guys who made your car have too much of an issue with it.


Buzz30 - "It creates heat which in turn creates sludge, deposits, and can even lead to more knocking which means more timing pulled and so on"

Actually one of the tell-tale signs of "too much heat" is a lack of carbon buildup. How, in this case, does more heat cause buildup? Also one of the ways sludge is formed in the oil is by water forming which is burned off with higher temperatures. Maybe I'm missing something.

Foghorn - "Fact: The PCM can only retard timing by 15 degrees maximum."

"The effect of this is to cause the engine to lose power …. a noticeable amount of power. The other effect of this is reduced cylinder temperatures which immediately dissipates cylinder 'hot spots'. With temperatures down and 'hot spots' gone, detonation has been eliminated. The KR response by the PCM is limited to not exceed 25.5 degrees." http://www.zzperformance.com/zzp/inf...d/kr_about.htm

Rogue - Sorry you gave up so soon. I refer you to the above two posts on your 15degree comments and relying on it to save you from low octane. Hey, did you drop your debate about oxygenated fuel being more powerful or is that on-going?

Willwren - Sure I'll use some 87 octane but I think the longer I use it the more the computer would have compensated and the less of an issue it will be. Have we forgotten about the experiment that GreenMachine is doing right now?


Random quote of the day:

"The great thing about the PCM is its ability to read all this sensor infor-mation, consult its own data tables, and come up with a measured fuelamount precisely matched to numerous operating conditions, including fuel octane levels. Finally, after considering all these factors, the PCM turns on a fuel injector to spray the specified amount of fuel. More fuel is added by a longer spray time, not by changing the spray volume.When the PCM cuts back on fuel amounts, the injector’* “on” time is shortened"
http://www.autoed.com/resources/samp...Care_Chap5.pdf

Hey folks,

I drove my Bonnie for over 35,000 miles over a 9 year period on 89 octane with not a single issue. I never once heard audible knock. I never ran 87 before and thought it would be an interesting experiment and considering it has a knock sensor, I didn't see any danger in trying it. I will most likely go back to 91 after this test, but wanted to test the theory that since 87 burns hotter, it might improve gas mileage, and yes I am cheap, but not crazy.

When I bought the car 9 years ago, gas was cheaper, and in some ways I regret buying a boat with a gas guzzling engine. I average around 15MPG to 17MPG on my daily commute, and wanted to minimize my expense. Since the car is paid for, It is cheaper to continue to drive it, rather than sell it for an economy car, so that'* really my motivation. I love the car, but in the end it is just basic transportation to me. I drive it like a grandma, so I see little danger in running lower octane for awhile.

I see alot of mods to improve performance, not gas mileage, so I'm trying little things here and there. I have some other interesting findings, but I'm saving them for another thread.

You're so irresponsible :P

Thanks Jay, I hadn't looked at Bill Hooper'* stuff for some time. I should therefore correct myself to say it is not confirmed that the PCM can only retard the timing 15 degrees. I realise Bill say it retard 25.5 degrees but I have heard both Scott Cook and Zoomer say 15 degrees - maybe they are only referring to "Power Enrichment" mode?

No comments on the rest of my post?

Cheers,

If you hear knock...then the next sound you're likely to hear might not be very pleasing :P

Cheers,

Does 87 octane fuel burn hotter than higher octane fuels or is it just more volatile?

Cheers,

Do we know to what degree the PCMs in Bonneville adapt? What effect does this have, cummulative or not, when accelerating at WOT and hence being in "Power Enrichment"mode?

Cheers,

I've owned several cars in the past before computers were invented, and they all would ping on occasion, but I never blew up an engine. That quote from the owners manual about light pinging not being dangerous is not from memory. I just read it a week ago.
To reiterate, I never heard even light pinging, not a peep. The knock sensor is designed to pick up sub-audible vibrations, that'* why it works so well in protecting the engine.
Over time, it will detune the timing to compensate, resulting in less pinging over time, at the expense of power. I'll check the knock count after I use up a tank to see where it ends up.

my statement was made based on people saying that we could no longer say whether it was a good idea or not, or if it would hurt performance or not, but simply if it was bad for the motor.

is a little going to destroy your motor? no. i thought my post was pretty clear on that. but it is negatively impacting the life of it. and your horrible gas mileage is also a function of that. in fact, if you bumped it up to what you should be running, you just might find that your gas mileage will pay for the gas itself. that was the case with one of my old cars - an 82 cutlass supreme - with the 231 v6 - when i switched to premium, my gas mileage jumped up to where it cost me less to buy premium because of the gas mileage i was achieving.

so before anyone says that it'* not the point of all of this, and in order for me to get better gas mileage to begin with, it had to be running in less than perfect shape, well, that'* the point. your engine was designed for 91, so it will get better mileage from it.

and again, no matter what you say, running lower octane will reduce the life of your engine, even if it'* a small amount that you may never have noticed.

sooo, the talk of premium versus cheapo comes straight down to economy. in many cases, it'* more economical to run what you're supposed to run, instead of getting crappy gas mileage from your car because it'* pulling 25 degrees of timing (i know you'd have to be in some serious trouble if it'* pulling *that* much, but the point stands).

matt