I ran an entire tank of high octane fuel through my car which felt really good and strong. However, I then filled it back up with regular unleaded and it seemed to lose a little of its punch. Am I crazy or does this really make a noticable difference? Thanks guys
Yes, it makes a big difference in a car with a high performance engine. Your Z comes with such an engine, known as an LS6.
Here's how it works. Your Z's PCM detects knock from lower octane gas and retards timing. Your power drops off accordingly.....if you want her to run her best, buy the highest octane gas you can get. The car comes from the factory set for fuel of about 95 octane.....
With a regular car that isn't driven for performance, like what your Grandma probabily drives, it's a waste of money to buy high octane gas.
Ensure that any high octane fuel you use, or any additives you put in to raise octane, are unleaded, or you will trash your O2 sensors.
As said above, I've read that higher octane fuel doesn't make the car run any better, but it prevents it from running worse (e.g. retarded timing due to knock with lower octane fuel), so essentially this is the same thing as better in my book.
As an FYI, I race on 100 or 104 octane unleaded and have more advanced timing in my car to take advantage of the higher octane (e.g. I can get more timing which is more HP without knock with the higher octane).
Do you mean there is a SOTP difference for you, or your lap times are better or both. How much HP are were talking about here? For me, 10-12 more isn't noticeable. Just curious.
You always want to use the highest octane needed to keep the car from pinging. If you use anything higher, you could actually hurt performance. The higher the octane rating, the slower the fuel mixture burns. If you want to optimized what octane rating you need, you should run a monitoring software on your car while doing WOT runs and then adjust the fuel accordingly. The best performance is just at the point of pinging.
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I will definitely from this point on use premium. The car is pinging more than usual without it....and I cant stand to not have all I can get. Thanks guys
Do you mean there is a SOTP difference for you, or your lap times are better or both. How much HP are were talking about here? For me, 10-12 more isn't noticeable. Just curious.
Zrod
Zrod,
I have never driven on the track without 100 or 104 octane unleaded race fuel, so can't really quantify the difference. I believe the PCMs tuned for 100 or 104 octane race fuel get about 10-15 more HP than prior to tuning. I also know (fortunately not from first hand experience) that if you put 93 in a car tuned for 100 and run it hard it will destroy the motor.
At the level of SCCA competition I am at, 10-15 HP is a noticable difference. I can't feel it by the seat of my pants, but I notice it as soon as I get next to another car who has it and I don't.
Octane makes a noticable performance difference at the track. 92 vs. 100 I can tell. And yes I do run better lap times with higher octane, maybe close to 1 second ( 92 out west sucks).
As previously posted 95 is enough and over that may be a waste. I use 100 at the track because it's what is available. I have as stock tune. My dyno below was with about 4 gallons of 100 mixed with 92. Those numbers are bone stock, stock air filter, paper plates. From what I see thats a high number for a stock car (about 8-10). Not so sure peak power is a real indication of how it drives with or without it. I doubt I could tell the difference the way I drive on the street, but you can tell shes a little lethargic at the track without it.
I hear, once your knock sensor backs the tune out. It takes 5 gallons before it resets. Not sure how this works, but search and you will find the details. So this would mean that if you add some octane boost to a dud tank it won't allow the pcm to see it. If you add 5 gallons and some boost you would be OK.
Most octane boosters add .30 to the rating 92 vs. 92.3. I understand the Lucas booster actually adds 2-3 points 92 vs 94-5. It costs about $12.
Use the fuel the car is designed for. If your car is designed for regular fuel, putting premium fuel is a waste of money and may hurt performance and is an old wives tale. Z06's love premium either 91,92 or 93 Octane. The higher the Octane the less hotter the fuel burns so putting 100 octane fuel in a stock Z06 may give less performance than 93 Octane.
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Never argue with an idiot. They drag you down to their level then beat you with experience.
Keep in mind that the Higher the octane the hotter the spark must be to ignite the fuel mixture. So you don't wan to go too high without mods. If you get fuel octane too low you will get pings and dieseling which is real bad and crappy fuel economy. The best recommendation is to follow the manual on recommended octane. But if you have mods on your car. I can recommend Nology Hotwires with Silverstone plugs used on the Flame front Ignition system.
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Cheers,
Charles
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Last edited by MikesZ06 : 12-14-2004 at 09:33 AM.
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