Regular or Premium Gas?

[Rac3rX]

Where does it say "above 87 octane rating improves performance of stock engine"? Octane is added to prevent engine knocking. If at 87 octane rating, your engine doesn't, why use 93 octane gasoline? But hey...it's your money.
If you feel that higher than required octane makes your car run better, then by all means use it.
As far as modded engines go, that same principle applies.

Where did I say "above 87 octane rating improves performance of stock engine"?

In my manual it says "87 or above" as the sugested fuel (section 4-2) & I got a 02 Protege LX.

SPECIFICALLY it says;

Octane Rating* (Anti-knock Index)
87 [ (R+M)/2 method] Or Above (91 RON Or Above )

This sugest that 87 is the lowest Acceptable fuel. (RTM)

But WHO is talking about a "STOCK" engine?

Im talking with MODS, like intake/exhaust line/headers/cams/UDP ect.

With these Mods you get increased hp as a result of getting a greater amount of the proper air/fuel mixture into the engine. When more of the proper air/fuel mixture is in the combustion chamber, the cylinder pressure is greater than it would be in an unmodified engine. This increased cylinder pressure needs more octane.

Ive also heard that you should initially be guided by the vehicle manufacturer's recommendations, however you can experiment, as the variations in vehicle tolerances can mean that Octane Number Requirement for a given vehicle model can range over 6 Octane Numbers, even more on a modified engine. Remember to compensate if the conditions change, such as carrying more people or driving in different ambient conditions. You can often reduce the octane of the fuel you use in winter because the temperature decrease and possible humidity changes may significantly reduce the octane requirement of the engine. But When its hot, and you go to a track for a few hours, well you can run your 87.

I use 87 in winter, 89 for a long trip.

I use 89 in summer for reg driving, & 91 for when at the track and long trips.

 

[Bigg Tim]

The higher octane will help decrease detonation, thus help to increase performance. That doesn't necessarily mean better fuel economy, just better performance. I have a J&S safeguard in my car and I can see it light up if I don't have gas with high enough octane in it. So the octane definatly reduces knock. But if you are not worried about power, then stick with the cheap stuff.

 

[Rac3rX]

The higher octane will help decrease detonation, thus help to increase performance. That doesn't necessarily mean better fuel economy, just better performance. I have a J&S safeguard in my car and I can see it light up if I don't have gas with high enough octane in it. So the octane definatly reduces knock. But if you are not worried about power, then stick with the cheap stuff.

Yeah for me I dont drive hard in the winter so I go with 87 unless on a long trip (Like MTL to T.O.) I put in 89 to keep everything well while in extended use.

For summer Im more of a spirited driver, and traction is back, so I up it to 89 for some added spice.

At the track Ive been experimenting with 91 & 94 octain. I originally used 94, but have been finding 91 to be just right for my motor as she is.

 

[Pretzellogic]

I know I dont have a 3 but with my mp5 i put the good stuff in it al the time. Mainly because I can tell the difference in power between reg and the good stuff. Plus the good stuff keeps your fuel system cleaner.

I know comeof you guys think its the plocebo effect with me feelign more power but its not. I know this becuase my atc I can spin the tires from a dead stop with higher grade gas then with reg at the same intersection and weather beign the same give or take a degree in temp difference.

But does it have any damage to your engien I highly doubt it.

It is not making more power, unless you have a "repeal the laws of thermodynamics" switch installed. If anything, it is making less power. Sorry.

Higher octane = less detonation, not more power. I run 93 in my car because if I didn't I'd have a problem. Before the turbo, I ran 87.

ALWAYS put the reccomended octane in the tank. There really is no benefit to buying more expensive gas, other than the weight-savings from having less cash in your wallet.

 

[Rac3rX]

It is not making more power, unless you have a "repeal the laws of thermodynamics" switch installed. If anything, it is making less power. Sorry.

Higher octane = less detonation, not more power. I run 93 in my car because if I didn't I'd have a problem. Before the turbo, I ran 87.

ALWAYS put the reccomended octane in the tank. There really is no benefit to buying more expensive gas, other than the weight-savings from having less cash in your wallet.

Less detonation means MORE power, as you not losing any power FROM detonation. (shocked) (RTM)

Or do you really think your not losing any power when there is detonation? AHAHAHAHA

Any HP recovered from hp loss is hp gained.

Its recomended 87 or above, for STOCK motors.

 

[cbc]

so then, if you suffer zero detonation or knocking using 87 octane fuel......

 

[Rac3rX]

so then, if you suffer zero detonation or knocking using 87 octane fuel......

I do as I stated, in the winter.

But summer gets HOT, increase temps outside increase risk of detonation, especially when driven HARD, and at a track. On top of increased air flow resulting in increasing compression.

 

[Installshield 2]

Less detonation means MORE power, as you not losing any power FROM detonation. (shocked) (RTM)

Or do you really think your not losing any power when there is detonation? AHAHAHAHA

Any HP recovered from hp loss is hp gained.

Its recomended 87 or above, for STOCK motors.

You really hurt your own credibility when you argue with yourself, and are still wrong...Pretzellogic hinted at the core of what this discussion is all about, my guess is because he knows about this, and you are laughing at him?...why laugh and then continue to make incorrect statements? Not trying to be a dick to you or anything, but don't assume others are wrong when it is obvious that you really are not sure what you are talking about in the first place...

...less detonation does not mean more power...In fact there are several occasions where what could technically be called detonation, is creating more power than otherwise...

also...do not confuse what an octane rating is...It does not necessarily mean how much "octane" is in the gasoline you are using...it is just a calculated rating of the comparability of the gasoline in use to a mixture of heptane (compresses poorly) and Octane (handles compression well)...

This is where the ignorance runs deep...an Naturally Aspirated engine's needed fuel is determined nearly single handedly by the compression ratio...ignition advance and other things can be tuned for nearly any type of quality fuel...but the compression ratio is what is unavoidable...high compression needs stable gas...simple as that...the higher you go, the better the gas needs to be...Turbocharged cars the need for higher octane rated fuel is needed because of the ability of the charger to increase max volumetric efficiency over 100%...when you cram that much stuff in there, your static ratio is low, but your actual compression is much higher...thats the magic of breaking over 100%...by definition, a Naturally Aspirated engine can not do that...

higher octane ratings do mean this though...a slower more stable mixture expansion...while this is great for hindering autoignition, this is not the best for power...and brings me to my point on this whole post...

High performance engines are not using higher rated gas to make the power...they are using it to keep the thing tamed...flash detonation can give an engine very noticable extra power (a common occurance on a hot engine just approaching the too lean area)...this just leads to premature engine failure do to the hot spots...you are correct though that at a certain point the detonation will hurt performance, especially types like preignition...but a racing engine only needs the quality gas to do deal with extremely high compression...but in general lower octane rated fuel will be more powerful, just less reliable and can eventually destroy the engine...

the only little thing that can do it is long reach plugs...and part of the reason for needing slightly better fuel is that they actually increase the compression ratio slightly...not to mention ignite fuel closer to the middle of the quench...

if you are using 92 or whatever in a lightly modified FS...you are wasting your money...argue all you want about "feeling a difference", but you are actually making a very small amount less power than you would with a more volatile gasoline...

also not to sound like a douche, but everything I posted here was found in less than 1 minute on google...

 

[Pretzellogic]

Less detonation means MORE power, as you not losing any power FROM detonation. (shocked) (RTM)

Or do you really think your not losing any power when there is detonation? AHAHAHAHA

What?

Cool facts and explanations

Concise and to the point: thanks for that. I'm tired of arguing with people who think that if the number is higher and it costs more, it MUST make more power.

 

[Installshield 2]

np man...this can get pretty technical quickly, but I wanted to illustrate that all of this was extremely easy for anyone to find and read elsewhere on the internet...You know what is going on anyway...but if one of the several people replying would have done a simple "octane rating" google search before opening their mouths...they would have realized how simple it really is...and how off some statements are...

please...anyone taking this offensively...hold it together...i am not trying to start a know it all flame war or anything...it is just constructive criticism that anyone could benefit from in the world of message boards...research a little before you speak, especially if it is relatively technical...welcome to ignorance prevention 101...

 

[Rac3rX]

Your telling me I hurt my credibility when saying knock is no good for performance, & reducing it prevent power loss due to knock?

So your saying knock has NO ill impact on performance at all?

I just want to be clear.

 

[Trevoke]

Watch me I'm a n00b.

Rac3rx, no, that's not what he's saying. In fact, I don't think he's referred to knock even once in his post. All he has said is that a higher octane rating does not mean better performance, and posted an explanation (which he even said he found on Google -- brownie points for stating sources).

 

[Rac3rX]

Knock is detonation & has been the limiting factor in internal combustion engine power generation since the discovery of the otto cycle itself.

When knock occurs, there is uncontrolled combustion with multiple flame fronts, with only one of them being initiated by the spark plug. During knock, cylinder pressures experience an extremely rapid rise and spontaneous burning and release of the end gases' energy. If this unintended ignition occurs very early in the compression stroke, then the piston will be forced up against the increased pressure of the burning gas and will result in a form of abnormal combustion referred to as preignition. When this happens, the end result, if severe enough, is that the connecting rods bend.

 

[Rac3rX]

Google? I can use that also.

"Effects of Detonation
Other than running an engine without oil, there is probably nothing that you can do that is more detrimental to an engine than detonating it. In an ideal combustion cycle there is a controlled burning of the compressed fuel and air, but during detonation there is an exploding of the mixture with a instantaneous release of all its energy, regardless of where the piston is in its stroke. The timing of the auto-ignition will have a direct effect on where the damage takes place.

Detonation very early in the compression stroke is usually the silent killer that goes unheard by the driver. This form of combustion usually results in rotating assembly failure by attacking the connecting rods and bearings. Detonation that comes nearer to TDC or slightly after is usually heard as pinging and will likely result in the burning of the piston or the lifting of the ring land from the piston. The force from the colliding of the multiple flame fronts can be likened to the wake of two boats travelling in opposite directions on a lake. When the two wakes meet, they usually peak and absorb the energy of each other. The more dominant wake will still have some leftover energy and will proceed weakly in its original direction. The same holds true for colliding flame fronts in a cylinder. If you have one flame initiated at the spark plug and another started independently of the plug, usually the spark-initiated front is the dominant one. As the two flame fronts collide, the pressure in the cylinder rises from the compacting of the molecules. Historically, the normal flame front has enough energy to run over the abnormal one but uses a lot of its energy to do this. Add to this that the abnormal combustion has consumed a portion of the combustible mixture that filled the cylinder, and the least result is a loss of power, if not a damaged engine"

What I am saying is any power loss due to detonation you prevent, is power gained.

Just Like a Penny saved is a Penny earned.

I know the fuel property the octane ratings measure is the ability of the unburnt end gases to spontaneously ignite.

 

[Trevoke]

Okay. I see where your point is. He's wrong to disagree with you, but the rest of what he says is correct.

 

[Rac3rX]

...less detonation does not mean more power...In fact there are several occasions where what could technically be called detonation, is creating more power than otherwise...

Could you explain this a little more, as you say "In Fact" Id would like to see some of the facts showing this, for clarification.

 

[icspots]

But if the engine is already working fine increasing the octane isn't reducing knock if there isn't any to begin with.

If the extra money on gas makes you happy then go ahead.

 

[Rac3rX]

But if the engine is already working fine increasing the octane isn't reducing knock if there isn't any to begin with.

If the extra money on gas makes you happy then go ahead.

If I had a million dollars...

If I ruled the world...

There are alot of if's out there.

Im talking about a Modded engine getting more air flow then stock, & being used at levels much more demanding then regular use.

Lets go back to Google for a Sec

"Abnormal combustion got the nickname knock from the noise that is transmitted from the colliding of the multiple flame fronts and the increased cylinder pressure that causes the piston, connecting rod and bearings to resonate. Any sort of abnormality in the combustion process has serious consequences in the power output, longevity and emissions generation of an engine."

HOWEVER!!

"Detonation very early in the compression stroke is usually the silent killer that goes unheard by the driver."

& This is important as someone put it "This is where the ignorance runs deep..."

"When knock occurs, there is uncontrolled combustion with multiple flame fronts, with only one of them being initiated by the spark plug. During knock, cylinder pressures experience an extremely rapid rise and spontaneous burning and release of the end gases' energy. It is not uncommon to see a pressure rise of up to 8 bars per degree of crankshaft angle, or up to 50,000 bars per second. Anything that will either increase heat or retain heat in the combustion chamber will promote auto-ignition."

&

"Anything that will raise temperatures in the cylinder will help promote detonation. This rise in temperature could occur many different ways: very lean air/fuel ratios, heating of the charge air prior to entering the combustion chamber, compression of the air molecules from forced induction, or poor heat dissipation through the cooling system. Increase of cylinder pressure will also prompt detonation. Camshaft profile, compression ratio and quench area all come into play. Design criteria as to combustion chamber shape and mixture motion, spark plug location and piston design can all make an engine more or less inherently prone to abnormal combustion. Naturally, spark timing and fuel quality round off the list. "

With more hp from intake/cams/headers/exhaust line, ect, that hp comes from more of the A/F mixture being comressed, increasing the compression, on top of Denso iridium plugs and Nology wires, & Being pushed ALOT harder then what Mazda considers Regular use, on Hot Summer nights. The risk of detonation increases quit a bit.

If your riding Stock, and live under 4500rpm use 87 and thats it, But Im not stock, and live above 4500rpm.

 

[Installshield 2]

detonation, like mentioned, refers simple to irregular expansion of the mixture...detonation is only one term describing many different types...autoignition is generaly used to define a form of detonation that occurs when internal heat ignites the mixture...this can cause two or more flame fronts within a cylinder that all collide...and make noise...and hurt things...

Now flash expansion is also a form of detonation, of which the expansion reaction ends relatively quickly...this does not mean it is always bad for power...this occurs very often with near stoich mixtures while load increases...and it is not very hard to control under certain conditions...and can often create more power than otherwise because of the violent expansion...the only bad part is the crown scorching that can occur...because of hot spots...

but that wasn't the point of my original post...I didn't mean to single just you out...I just read your post to Pretzel...so started with that...that is all...

but my point was that an octane rating has nothing to do with how much power your car will make...

In your case for example, you are wasting your money...no offense or anything, but the stock ecu will not change your ignition timing to take advantage of a slower burning fuel...You need to advance the ignition timing before TDC more to offset the fuels slower expansion...your ecu will not do that...and the more stability is not needed for the mods you mentioned, mostly because the compression is still relatively low per high rated fuels stability...and the ecu is very mild on the ignition advance...the increased flow from a couple bolt-ons is nothing as far as the gas is concerned...an increase of cylinder pressure equated into ~15-20hp is rarely enough to need to switch fuel, unless there are some other things going on...

correct me if I am wrong though dude...its your car...if you were having problems with detonation, so be it...but I ran similar bolt-ons with long reach plugs for 40,000 miles on the old engine without any detonation at all...all while using 87 rated...and it ran great...

now if

 

[Installshield 2]

one other thing...on your last post; the lasts line...

Detonation is most prominent at max VE, which is where it always makes maximum torque...you are saying "you live above 4500", that is the least likely place for detonation to regularly occur because of the MPS at that point...piston speeds will demote detonation because of the quickness of the piston dwells...not to mention that our radically low rod ratio of 1.47 already has some of the shortest piston dwells around...

that can easily be backed up by all the good factual evidence you posted right above that last line...the first place detonation will show up is max VE, which is where you are sucking in the most air and the using the most fuel per cycle...and this is where the highest cyclinder pressure per cycle will be reached...if you are not detonating there because of your performance mods, you will most likely not detonate anywhere else as long as the tune is good...and with the richness of an FSs open loop, that is even less likely...

Max VE by the way is somewhere around 3700 rpm with your mods I would bet...