I'm gunna try to list things on the back of my head now..
1.8L>2.0L Bore, Camshafts, Cam Gears, Pistons, Rods, Valve Springs, Fuel Pump, Fuel Rail, Injectors, Port Matched, Port & Polish, Ecu.... etc...
too much to list on my track car.

It's not a bad thing. You said you did internal work which probably raised your compression ratio that rasied ratio usually will cause a car to Ping (detonate) running lower octane (87,89,91) rated gas. Running 94 will allow you to take advantage of the mods that you did to your engine by tuning.

Higher Octane dosen't increase HP/TQ it just helps to keep Pistons from coming out the side of the block or through the oilpan by helping reduce Knocking and Pinging. Tuning is where you get your HP from.

That would raise your compression def. over what 91 would safely let you handle. How high where you reving and what compression where your pistons ?

Sorry, I thought you were driving a Z.

What do you do if you can't get 94 octane?

Why go to 94 octane unless you're running 12:1 or greater compression?

I think she drives a type R or has a type R swap those are 11.5:1 from the factory so giving that list of internal work I'm assuming it's been rasied to the 12:1 or higher. Most that I know go 12.5:1 on their B-series if they're sticking to NA.

Does anyone here realized that you get less miliage on Octane 94 than 91?

And I honestly can't tell the different between the two except for my pocket.

This is spot on and 100% correct. Operating your car with anything higher than required to prevent knocking is just wasting your money. Octane rating does not relate to the energy content of the fuel. It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Octane is not something you add to a fuel, it is just a rating on a fuel's resistance to preignition (knocking). Certain additives are added to the fuel to increase the octane rating. Until the 1970's, Tetra-ethyl lead was that additive (hence leaded gas) but has been since replaced by MTBE as the additive used for health and environmental reasons.

A fuel with a higher octane rating can be run at a higher compression ratio without detonating. Compression is directly related to power, so engines that require higher octane usually deliver more motive power. Engine power is a function of the fuel, as well as the engine design, and is related to octane rating of the fuel. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber. When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines. Many high-performance engines like the Z's are designed to operate with a high maximum compression, and thus demand high-octane premium gasoline. A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power.

However, burning fuel with a lower octane rating than required by the engine often reduces power output and efficiency one way or another. If the engine begins to detonate (knock), that reduces power and efficiency for the reasons stated above. Many modern car engines feature a knock sensor which detects knock, and then sends a signal to the engine control unit to retard the ignition timing. Retarding the ignition timing reduces the tendency to detonate, but also reduces power output and fuel efficiency.

While working on my undergraduate degree (mech eng) I took a course on internal combustion engines and my professor was an expert in this field. I clearly recall him telling us that using a higher octane rating than required was a waste of money. He suggested that if your car did not ping or knock while going up an incline or hill (where this usually presents itself first) then you were fine with your current octane rating. We even had a lab where there was a Ford V-8 on a test stand hooked up to a dyno that we ran tests on comparing power versus different variable such as fuel mixture and octane rating. Our tests showed that there was no appreciable increase in power when using a higher octane rated fuel but there was definitely a decrease in power when using a lower octane rated fuel at the higher end of the RPM spectrum.

Now, would you like me to prove that Force=mass x acceleration or are you going to take my word for it?

Thank you for the detailed explanation. It makes perfect sense. I don't suppose you have any video clips of this dyno test or even just the graphs, do you?

Yes, USNA94, please prove what the optimal octane is for the 370z.

Well, to be fair, the question of what the optimal octane for the 370Z is, and whether or not higher octane produces additional power, are two separate questions. Given the level of detail in USNA94's explanation of how octane works, I have no reason to doubt the information. It'd just be cool to see some definitive evidence is all. After all, unless he's making up stories, he was privy to such evidence by virtue of his lab test. It'd be nice if he has the graphs from that test or something to share with us.

You are absolutely correct and explain it well.Unfortunetly there are those that when they hear the word "race gas" they right away believe it will make the car run faster.
As you said the only reason for race gas which is higher grades of octane is only needed for high compression to avoid detonation.It is hard for someone that isn't familiar with building engines or the mechanics of a motor to understand.
So all they are doing is wasting money.Hopefully what you stated will sink in and some will believe.There are of course those that no matter what will believe what they want to believe regardless!

Well, it will if it's oxygenated, won't it? Or am I missing something? I understand the higher octane won't do anything, but the oxygenation helps doesn't it? (Not that I'd spend the money on that stuff to run on a regular basis, mind you.)

Optical would be whatever octane you tune it for before it starts knocking and pinging ... its hard to say what its tuned for stock because the ECU is the learning type so it can adjust itself to whatever premium gas is avaliable to it. You could say that its tuned to 91 and will increase performance with 93 as it "learns" it or that its tuned to 93 and decreases performance with 91. Whatever works best for you I assume.

I wish I did but as I took this class over 15 yrs ago (damn I'm getting old) all that stuff is long gone. But maybe if I poke around this interweb thingie some more I can find some data/graphs posted some place. Honestly, this is a pretty common lab experiment to run in engineering classes.

If you would like to provide me your engine, a test stand, and a dyno (I'll supply the gas of various octane ratings because i'm generous like that) I would gladly provide this information with some pretty graphs and everything. If not, I suggest going with what the owners manual states. I hear those Japanese engineers are pretty sharp.

USNA94, do you by chance know what 98 RON means in relation to, say, 93 octane here in the US? I'm curious because of the post below:

98RON equates to about 92 octane here in the states.

Here in the states we post the average of the RON and the MON. Other countries sometimes only post the higher number.
The below explanation is copied from: How Much Octane Do I Need?

What is octane? How can it help my engine? two laboratory octane numbers determine the overall octane quality of a gasoline. Both numbers are determined in single-cylinder, variable-compression-ratio engines. The first is the research octane number (RON), where operating conditions are mild. This is the number that gas stations in the 1960s put on their advertising signs out in front, numbers that ranged from a little over 100 to as high as 104. If an engine is detonating (pinging) at part throttle, it usually needs more RON.

The second laboratory octane number is also determined in a single-cylinder, variable-compression-ratio engine and is called motor octane number (MON). The MON test is conducted under more severe operating conditions (higher rpm and higher inlet temperature) than the RON test, and as a result, the number is lower. If an engine is detonating at wide-open throttle, a higher MON will usually satisfy it.

The number shown on the black and yellow sticker on the service station gas pump is the average of the RON and MON, or antiknock index (AKI). If the sticker shows an AKI of 92, RON is typically between 96 and 97, and MON is typically between 87 and 88. The RON and MON can vary slightly but still must average a minimum of 92 to have a pump posting of 92. Higher octane unleaded fuels will have a greater difference between RON and MON. For instance, 76 Unleaded Racing Gasoline has a RON of 106 to 107 and a MON of 94 to 95, which gives an AKI of 100 to 102.

Well, I might just spend some time and money on dyno'ing with 91, 93, 94 and share the results with you all. One of these days...

I agree that with an older engine/ECU, given a fixed set of engine parameters from the factory, running a higher-than-necessary octane rating is total waste in every respect. However, we know that even on a traditional engine, higher octane fuels allow tuning headroom. When tuning the A:F ratios and the spark timing, you can account for higher octane fuel and get more power that way. The flipside is by tuning for say 110 octane race fuel, you've now made a car that will knock on regular pump gas.

The big question mark with our cars is: given a stock ECU, is the stock ECU smart enough to tune itself upwards for a higher octane fuel automatically? We already know that the stock ECU knows how to de-tune itself when presented with lower-octane fuel by using sensors to detect the onset of knocking and making the appropriate adjustments.

There seems to be some evidence that, when given a much higher octane fuel, our ECU will slow retune itself for higher power using those same sensors as a guide. I find it a bit hard to believe myself, but someone did do a dyno with some 110 race fuel and showed some statistically significant gains a while back.

Edited to add: Even without "oxygenated" fuel, just plain higher octane does allow a higher horsepower tune. By making the fuel more knock resistant, the timing can be advanced further without knocking, which results in more power.

Not really, we oxygenate gas to to reduce carbon monoxide that is created during the burning of the fuel. It's an environmental thing, not a performance thing. One of the additives used to do this is ethanol and we all know what that does to performance.

Don't know if this was posted yet, but in the users manual it mentions to run 96 oct

or mix until you can find better gas.

Got a kick out of that when i read it.

Makes me miss Ohio, (sunoco 94) =)

Hmm... in that case, do you know what accounts for the 14whp gain that was achieved from the XXX Oxygenated Race Fuel?

It's my understanding that it "tunes" itself using the knock sensor. There is no octane sensor. When it detects the onset of knock using the knock sensor the ECU throttles back thereby reducing performance. If there is no knock when running 91 octane and definitely no knock when running 101 octane, the ECU would never know the difference and run the same. It doesn't open up the throttle any more or provide more power. It just knows there is no knock happening. And the energy content of the gasoline does not go up with octane. 91 octane fuel has ~32MJ/liter of energy, 101 octane fuel has ~32MJ/liter of energy, 121 octane fuel has ~32MJ/liter of energy so the power of the engine is the same. The higher octane will allow you to run a modified engine with a higher compression ratio to get more power though.

Here's a screenshot of what it says in the manual.

http://www.the370z.com/attachment.ph...1&d=1252020193

I'm not sure what they mean by "Research octane number" though. :confused:

This "RON" system is used in Europe,all Asia,Austraila & of course S'pore....

I agree, if your car was made for regular than you burn regular. I mean yes in my civic I have ran a few tanks or premium with a fuel injector cleaner and a few times on race night but there was no real reason for it. If it takes a certain kind of gas that is what you should use. End of story.

104
 

104 Sunoco race fuel on a re-tune!!

Apparently this is one of those subjects that you can beat to death.As I said in my last post there are those that insist race gas will make more power in the Z because they just don't know any better.
The 370Z in stock form is NOT going to make more hp with race gas instead of the recomended fuel by the manufaster.Plain and simple!
Some know the real deal and others are lost.It is a shame that these gimmicks catch some and they waste there money!
So anyone advertising any different are looking to draw attention,don't know what they are talking about or looking to make a buck on the public that just isn't familiar with the performance world.
As for the additional 14 hp on just race gas with a stock 370z is pure bull at its best!
Guys in the race world spend thousands of dollars to gain every little bit of hp to have an edge over there competiter but a stock motor with premium fuel versus race gas is a waste of money!No advantage power wise unless its been modified with the compression raised to the point it will detonate on pump fuel!
As to the oxgeanated fuel that is a whole different type of fuel.The first post if I recall was about higher octane fuel.

This is what I've been saying all along. :)

Yes. Let's talk about at the pump of the majority of gas stations. It's not about educating people about race gas, 120 Octane gas, or the "more octane is always better" mentatility. It's about finding out what the 370z runs best on and possibly saving money to boot.

Let's talk about what almost all members here can get:
91 vs 92 vs 93 vs 94 AKI

External factors aside (engine condition, temperature,), will a stock 370z be able to gain anything performance-wise by pumping higher than 91 octane gas?

hahaha well I just think it's better to give my baby better food :p

it's at 12.1
you're on the right track it's 12.1
It's a Type R :p and it eats most of the k-swaps in town :D

We agree on this, although I think the new knock sensors are supposedly picking it up much earlier, when it's a tiny hint of a knock. You don't actually have to get to where you're risking damage to have the sensor "see" it and adjust.

Here's where we potentially differ (not that I'm solidly in the other camp either, I'm just playing out their side of the argument as best I can, and it's reasonably sound, but has question marks):

The way that the ECU responds to knock is not to "throttle back" literally with the throttle, but to retard the timing, which eliminates the knock at the cost of performance and efficiency. You mentioned this yourself in an earlier post, but I just wanted to be clear on that issue:

Similarly, if you put 110 race gas in a car that was designed and tuned for 93, there's lots of "knock headroom", so to speak. With the higher octane fuel in the tank, a tuner can go into the ECU parameters and advance the ignition timing more aggressively than stock to create more power than was possible on 93 octane due to the higher resistance to knocking the 110 fuel has (the inverse of what we described above, where retarding it reduces power and helps avoid a knock). There's still only X MJ/liter of energy in the higher-octane gas, but by being more knock-resistant, it allows a more aggressive spark timing advance, which results in increased horsepower.

I *think* we both agree on the above - that by tuning the ignition timing manually with an ECU programmer up as far as you can without knocking, on any modern-ish car where that is possible, you can get more horsepower out of 110 gas than 93 gas, even though they both have the same MJ/liter of potential energy within them.

The question mark is whether the ECU is smart enough to do this by itself. Some have claimed that when it detects absolutely no hint of knocking, it slowly advances the timing more aggressively until it finds the first hint of it, and thus self-adjusts upwards (more aggressive spark timing, more power) for higher-octane fuel in much the same manner that we know it self-adjusts downwards for crappy fuel.

Nobody has put out any hard evidence that this is true, but people have mentioned it, and the 110 race gas dyno results seem to indicate that *something* is going on, and this explanation kinda fits the bill.

I agree with all of your points. :bowrofl:

As far as the ECU being smart enough to adjust up on it's own I don't know enough about how it works to say. Would be cool if this were true though I wonder what the limit is as you can only adjust timing so much I would think.

I think this is more of a terminology issue than anything else.

To me, oxygenated is meant in the government regulation sense in which oxygenation is used to control emissions and reduce pollution.

Maybe they use "Oxygenated" differently because it sounds better and sells more gas but really what they are selling is a blended fuel that has a higher energy content and is more appropriate for racing and most likely not street legal. This could count for the documented Hp gains. JP-5 or aviation fuel has a higher energy content than standard gasoline. I'm sure it would boost horsepower as well but i'm sure you would have some serious knock. :eekdance:

Psh Home made race gas(via your local chemical wholesaler or work hookup) One gallon of Propylene oxide(Oxygenator in the nitromethane kind of way)which EXPENSIVE, one gallon of Tolulene (sherwin williams for $14 bucks, omit if not advancing timing or increasing boost/compression) to ten gallons of premium gas. The propylene oxide may be federally controlled now (F**King anti-terrorist laws) but it's good for about a 6% boost in power, and the tolulene is a knock inhibitor that bumps the octane rating of the fuel to around 110-115 letting you crank the boost. You will go through A LOT of fuel but it's power in a can.

Very few of the octane boosters at the advance auto work the one that worked the best was the NOS octane booster in the box used 2-3 per tank and it would let you run a 100 octane map. The ones that say they will raise your octane 6 points mean .6 octane hence 6 "points." The gallon of tolulene beats all in that department ~7 full numbers for $14 and ~14 for $28. Careful though the PO and Tolulene will take their toll on plastics if you use them continously so i'd save it for track days and flush it out with 93 at the end.

this topic is getting hot~!

Wow! Rep for that knowledge. Very informative :tup:

I'll PM Ryan at Injected Performance (one of the forum's sponsors) and ask him to chime in on this, seeing how he's the one who did the test and made the video. I'll let him know that you're calling him out as a liar and a fraud.

OK, sorry! :)

:tiphat: