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Old 04-08-2011, 09:42 PM   #1
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Octane, and why SVT's need 91 or more.

Rabble-RABBLE-rabble-Rabble-RABBLE-rabble!

Yes. SVT's are OEM Built and Tuned for 91 Octane fuel.
Yes. Gas prices are currently "LOL", "OMG" and "WTF?", with SVT's requiring "WTF?" or higher.
Yes. Selling your SVT and getting a ZX3 or SES is as much an option as getting over it.


Sorry, but I had to. With all the inadvertent thread hijacks lately I thought you guys would appreciate a thread to discuss and vent some frustrations.

This isn't a topic that is likely to ever go away, so let's lay the myths to rest, so that people can better understand and accept the fact that they will be paying more for their gas for their duration as an SVT owner.

Fact: Octane rating indicates how much pressure gasoline can withstand before it becomes unstable and spontaneously ignites.

Fact: Unless you LOWER your car's compression and adjust your timings, you cannot safely run 89 octane fuel or lower in your OEM SVTf.
Doing so can cause excess wear and damage in both the upper and lower halves of the engine, including spark plugs, piston rings, valves and seals, etc, and ultimately cost you more money in the long run than you saved in the short term.

Fact: Just because you don't hear knocking, doesn't mean that it isn't happening. SVT's have Variable Cam Timing (VCT), can detect misfires and knocking, and can compensate for those by retarding (slowing down) your timing, which causes these engines to lose efficiency. In addition, the engine can only compensate so much, which only keeps you mildly safer at low RPM's.

Would you like to know more?

Question: If the engine compensates when you use lower grade fuel then it should actually be safe, shouldn't it?
Answer: No. The engine cannot compensate by altering it's compression ratio, and you still run the risk of detonation.

You should only use lower grade fuel if you have no other choice:
-Some Gas station in BFE doesn't have 91+ Octane fuel.
-You forgot your wallet at home, are running on vapors and have to gather loose change from under the seats, et cetera...

Note: If you do find yourself forced to use lower grade fuel, keep your RPM's below 3500-4500; it will reduce chance of detonation, but it can still happen. You should also top up with 93 and/or add octane booster as soon as possible to bring the octane back up to a safe level.
Your engine's efficient operating range tends to be around 4-7k RPM, and the engine cannot retard the timing enough for this range (and no engine I know of can adjust compression), so the engine WILL eventually experience detonation and start taking damage proportionate to RPM.

I'll let you guys take it from here. Any useful replies will get added to OP for as long as I bother to maintain it. Let's see what we end up with and whether it sticks.

--------------------------------------------------------------------------
Quote:
Originally Posted by JCH841 View Post
If you're heading for BFE, why not grab a bottle of octane boost and throw it in the trunk. Then if you're on fumes and can't find 91 octane, break out the bottle and no problem.
Quote:
Originally Posted by standard View Post
here's another thought people ALWAYS overlook.. If you spend $0.20 a gallon MORE for premium fuel, and you fill ALL 12 gallons up, you manage to spend an extra $2.40 cents on your fill up for using premium.
Quote:
Originally Posted by bmylez View Post
Just need to clear things up. The VCT only changes *CAM* timing. The VCT solenoid is not a knock sensor. It only changes the intake cam timing based upon input from the ECU (load, RPM, etc). [...]The knock sensor, which is mounted on the back of the block, is what tells the ECU to pull timing when you put below 91 oct in it.





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Old 04-08-2011, 10:00 PM   #2
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Nice work on this post dude. Plus Rep for you!
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Old 04-08-2011, 10:01 PM   #3
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This thread has perfect timing... I just had some @ss today give me crap for putting "High Octane" in "just a focus" and it doesn't make it a "race car".

I swear to Christ if one more MotherEffer makes another comment about me and my racecar, and putting 93 (not very much 91 in my area) in my car I'm going to punch them right in the redneck.

Wow... it's good to vent. Sorry I didn't add to the OP, just wanted to vent. Thanks.

P.S. I love my Focus and I'll put 93 in it even if it gets up to $11/gallon (just filled up @ $4.09/gallon today).
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Old 04-08-2011, 10:19 PM   #4
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Nice work on this post dude. Plus Rep for you!
Thanks! I was starting to think people forgot the button was there, lol.
I'd seen and heard enough people trying to say that its 'safe' to run mid-grade that I decided to put this together. It's one thing to be mistaken, and something else entirely to pass incorrect information on to others.


Quote:
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This thread has perfect timing... I just had some @ss today give me crap for putting "High Octane" in "just a focus" and it doesn't make it a "race car"[...].
I can't say I've had that happen to me, but I've definitely been expecting some clerk or bystander to eventually point out that I've 'mistakenly' chosen premium fuel at the pump. lol.
...and yeah, prices are the same out here. I'm just thankful to be working full time now; still hurts the wallet though, especially since I'm doing about 100mi a day.
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Old 04-08-2011, 10:29 PM   #5
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Yeah some people dont like to listen. But when the engine fails cause they have been putting the wrong fuel type in thats a hefty bill >_<
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Old 04-09-2011, 08:34 AM   #6
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If you're heading for BFE, why not grab a bottle of octane boost and throw it in the trunk. Then if you're on fumes and can't find 91 octane, break out the bottle and no problem.
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Old 04-09-2011, 09:29 AM   #7
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here's another thought people ALWAYS overlook.. If you spend $0.20 a gallon MORE for premium fuel, and you fill ALL 12 gallons up, you manage to spend an extra $2.40 cents on your fill up for using premium.


Aka, who gives a shit.
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Old 04-09-2011, 09:59 AM   #8
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^^exactly Damn cry babys. Ok so its. Alright to buy a $7 cup of coffee at starbucks or buy 1 energy drink. But an extra $2.50 at the pump for 91 (cali) absolutely kills ur wallet lol some people just don't no what they r spending. I laugh when I see someone complaining about gas prices when they are wearing $200 pair of shoes lol.
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Old 04-09-2011, 10:04 AM   #9
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^^ or have a brand new iphone/android or whatever.

I had a random guy comment on putting 91 in my car. But, i am good at completely ignoring people. I never said a word, just finished and drove away

Nice write up
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Old 04-09-2011, 11:52 AM   #10
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^^exactly Damn cry babys. Ok so its. Alright to buy a $7 cup of coffee at starbucks or buy 1 energy drink. But an extra $2.50 at the pump for 91 (cali) absolutely kills ur wallet lol some people just don't no what they r spending. I laugh when I see someone complaining about gas prices when they are wearing $200 pair of shoes lol.
No more calls, please.....we have a winner....

I also have an old(er) BMW. I am amused by the first time car owners who think they can buy and maintain a BMW on a Kia budget. When someone on a forum posts, my car's running hot and I checked the coolant but I don't have $ for a thermostat or new radiator - those effers are $250! so I went to a junk yard and that radiator leaked. I put in some Bar's Leaks, it didn't work and now I think my head is cracked...OMG, WTF, GTFO....

KIDS, DO THINGS RIGHT THE FIRST TIME!! AND IF $2.50 PER TANK OF FUEL BUSTS THE BUDGET, USE FUEL MONEY FOR BUS FARE...Live in the boonies with no bus line? Don't waste your time with a "Turbonator" just use the CORRECT fuel and learn how to use right foot to regulate fuel consumption.
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