Racing fuel in a Z

kannibul

It's amazing how much octane is thrown around as a way to increase HP.

The car is designed to run on 91. Running less than that trips the knock sensors to retard timing. It won't advance timing due to higher octane - in fact, the car won't even "know" that it's running on higher octane, it simply knows that the knock sensors aren't tripping.

imag

I understand the benefits of oxygenation as well as energy density. However, it is not uncommon for modern high performance moderate-high compression motors (like ours) to have small amounts of detonation with 91 octane gas, especially when the motor is hot and/or the air is hot and dry. Likewise, they can adjust the timing to can take advantage of moderately higher octane fuel (94-96) when conditions warrant - like being on a dyno or on a race track.

Edit - sorry - missed the second page. RCZ is exactly right.

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Stillen CBE, Stillen track cooler, Stillen Gen3 Intakes, B&M short shift kit

kannibul

I think that the Z is built on spec for 91 octane to run properly under all conditions, and as a safety will retard the timing if it detects a knock.

Gas that is delivered to the gas stations are "more or less" 91 - so some days you might be pumping in better than 91, other days less than 91. Depends on what gets delivered from the supplier.

If you doubt it, look at the sticker on the pump where it was tested.

Soemthing also to consider for those who top-off often. There's fuel in that hose all they way from the pump - that's about 1-3 gallons worth of whatever was put in there by the last customer. So, the first 2-6 gallons you put in are more than likely "mid grade" - 89 octane...even if the gas in the tank is on-spec, you won't reach a perfect 91 octane even if you fill up...

ianthegreat

Oops *104-105

I cannot comment on his car as I do not own a 370z. I've not ridden in it w/ fuel nor seen it run at the track w/o fuel. It just seemed quicker, but you are right.. could be a placebo effect.

I've never run fuel in a NA engine before. Admittedly, I know little about it other than it's improving my cars performance.

My AFR's are fine. Stock compression ratios are already high. I may make a switch from fuel to meth though as fuel is just getting way to expensive. I am consistently trapping higher on fuel - 109mph vs. 112.9mph over nearly 30 runs. I am tuned though, but none of my logs have shown me knocking on 93oct. I'm actually riding the factory knock sensor - the tune is not adjusting timing at all.

I need to go back and review the logs, maybe try different parameters, and see if I can see anything.

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