no 93 octane
This is a discussion on no 93 octane within the Firebird / WS6 forums, part of the Vehicle Specific category; Octane is resistance to combustion, therefore the more octane you have in your fuel, the less total energy your fuel ...
05-12-2008, 08:10 PM #61
Octane is resistance to combustion, therefore the more octane you have in your fuel, the less total energy your fuel has.
However, because octane resists detonation, it allows you to run much higher compression and therefore gain more total output out of your less powerful fuel.
It's a give take relationship, but if you tune/build for high compression, you can easily overcome the power loss per given fuel amount.
05-12-2008, 09:05 PM #62
Very informative thank you, I never knew that. It's still beter to run 92,93 octane right but 87 won't kill it eather?.........well not yet anyway.
I am running stock compression basic mods, full exhaust, transmission tune, emission delet, by months end I'll have a high flow air intake, low temp thermostat and stage 2 tunning with jet performance tunner.
05-13-2008, 05:26 AM #63
- Join Date
- Apr 2008
- Ft Worth
- 94 TA GT
This engine has knock sensors in it. You can run 87, but it will retard the timing to try to prevent or reduce pinging, and you will loose some power as a result.
I have run 87 in mine, and it "feels" like I loose just a little power. Not a huge amount, but it seems a bit less responsive.
The owners manual calls for 91 octane but also says you can use 87, and if you haven't done anything to the engine that has increased the compression ratio, there is no need for anything higher than 91. I haven't yet tried 89 mid grade octane to see how it performs, but I would bet that on a stock car, you wouldn't be able to tell the difference between it and 91.
There has been some evidence though that premium fuels burn cleaner, and thus leave less deposits on your valves. Chevron and other stations are also reported as putting in a bit more of their cleaner additives in their premium fuels, and that may explain it.
Chevron Techron fuel cleaner is by far the best fuel cleaner out there, and is present (in a very diluted concentration) in all Chevron and Texaco gas now, though I think you need to buy a bottle of it and pour it in a couple times a year to really do you any good. The concentrations in their gas are pretty low. Something like a quart for every 1,000 gallons or so.
05-13-2008, 08:31 AM #64
05-13-2008, 08:35 AM #65
Oooops, didn't realize there was a page 4. My email link put me on the last post of page 3,,,,oh well.
Anyway,,,I checked the local BP and the Sunoco,,,neither of them advertise any ethanol mix.
05-13-2008, 08:38 AM #66
05-13-2008, 08:42 AM #67
Fred is correct although I don't 100% agree with the 89-91 comment. Although this isn't much of a change in octane ratings,,,,on a stock vehicle this may not matter. But to be sure I would have to find someone willing to log alot of miles with a stock vehicle,,,a tank of 89 and a tank of 91 and see if there is any knock detected.
Something you may not feel at the seat of your pants,,,,but it would certainly affect gas mileage.
Also elevation and heat/temperature both engine and ambient would all play a roll in this.
I still currently use 94 octane, and have the timing tables and fuel curves dialed in as such (on an internally stock engine). If I made the drop to 89 I would surely have knock issues, especially in the summer time when the temps climb.
Shucks I get a degree or two here and there when the temps climb in the 90's as it is.
I'm sure when I move to Arizona where 91 octane is highest available,,,I will have to retune the car, dropping 3 numbers along with summer heat will give me issues for sure.
Once done though, it's possible that 89 may not affect it so much. Only time and logging will tell for sure.
05-13-2008, 08:47 AM #68
We are planning to leave Ohio and move to Arizona,,,just getting too old for the snow and winters are getting rough.
Yes that winter grade gas is crap. They do something with it that lowers the flash point for easier starting in the winter and prevent fuel line freeze up etc.....but it sucks once the temps hit about 50-60 degrees. Which we sometimes get a few winter days like that,,,,,then the vapor lock crap starts It's not until late April or early May when they switch to summer grade,,,and the cars are much happier on it. Problem is that it also raises the prices. Thats what the latest price hike was about 3 weeks ago. There was an issue of short supply of summer grade fuel mix. Some gas stations were running out around here waiting for the trucks.
05-13-2008, 02:51 PM #69
- Join Date
- Sep 2005
- 2001 z28 lingenfelter 383
05-13-2008, 04:31 PM #70
05-13-2008, 06:45 PM #71
- Join Date
- Apr 2008
- Ft Worth
- 94 TA GT
If you really want to know if a particular octane grade is changing your performance, the easiest way to do that is monitor the output of the knock sensors and see if they are outputting a signal. If they are, then you know the computer is backing off the ignition timing to compensate. If they aren't putting out a signal, then you aren't knocking, and the engine is running fine on that grade of gas.
05-13-2008, 07:07 PM #72
05-13-2008, 07:12 PM #73
I wouldn't think so.
05-14-2008, 03:20 AM #74
05-14-2008, 03:22 AM #75
Most of the time you will be getting 2-3 and even 4 degrees of knock and you won't even know it. It's not enough to be audible, especially with loud exhaust. And the computer will pull that timing out anyway,,,and eventually learn a new timing curve from the low octane table if it persists. You really have to scan the car to see whats going on. Of course that costs more money,,,,the joys of modern technoligy,,,lol.
Last edited by Firebirdjones; 05-14-2008 at 03:28 AM.
04-17-2011, 12:01 AM #76
- Join Date
- Apr 2011
- The South
- 2001 Firebird Formula
Let's Clear the Air
Let's clear the air on this octane issue once and for all.
All the people who tell you it will damage your LS1 engine by using 89 or even 87 octane don't know what they're talking about.
From my 2001 Pontiac Firebird owners manual, and I quote:
"If you have the 5.7L V8 engine (VIN Code G), use premium unleaded gasoline rated at 91 octane or higher FOR BEST PERFORMANCE.
YOU MAY USE MIDDLE GRADE OR REGULAR UNLEADED GASOLINES, BUT YOUR VEHICLES ACCELERATION MAY BE SLIGHTLY REDUCED."
Case closed. End of story.
I have occasionally run 89 octane in my Firebird since gas prices are sky high and have noticed no discernible difference in most driving conditions.
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