Let's talk octane...

MightyBobo · 11-06-2011, 03:34 PM

Quote:

Originally Posted by XwChriswX

Since larger injectors will come with any Z TT kit, could you theoretically convert to E85 at the time you went TT? Or would you need even larger injectors than the ones that come with the kit being the kit has already compensated for the extra fuel needed for TT?

Depends on the injectors, but I'd hazard to guess you'd need to go even BIGGER. I dont know how close we are to maxing out the stock injectors with only basic breathing mods off hand, but I doubt any FI kits are going to come with HUGE injectors - just enough to handle the max HP of the kit. Whereas with an E85 setup, you'd need injectors 30% bigger than THAT, really.

Also, cant forget the fuel pump...one that can at least keep up w/ those injectors...

Red__Zed · 11-06-2011, 03:43 PM

Quote:

Originally Posted by Methodical4u

so back to my other question... since the VVEL cannot be changed, can the timing of the engine still be changed? Basically i'm saying... if I wanted to run race gas for a run down the 1/4 and I needed to tune for it, can the timing be advanced due to the higher octane to maximize power? OR is that all part of the VVEL?

You can advance timing within certain limits.

Quote:

Originally Posted by XwChriswX

Since larger injectors will come with any Z TT kit, could you theoretically convert to E85 at the time you went TT? Or would you need even larger injectors than the ones that come with the kit being the kit has already compensated for the extra fuel needed for TT?

like most things, it depends on what you are doing. the other thing you have to watch for when setting up for e85 is corrosion in your fuel system, which often requires running different components than what TT kits come with (not that familiar with Z kits though)

Methodical4u · 11-06-2011, 03:40 PM

so back to my other question... since the VVEL cannot be changed, can the timing of the engine still be changed? Basically i'm saying... if I wanted to run race gas for a run down the 1/4 and I needed to tune for it, can the timing be advanced due to the higher octane to maximize power? OR is that all part of the VVEL?

MightyBobo · 11-06-2011, 03:59 PM

Found it...

http://www.neufamily.org/images/67novagallery/

Jordo! · 11-06-2011, 04:14 PM

Octane refers to how easily the fuel will spontaneously ignite, as in from heat or pressure (which also increases heat); the higher the number, the less likely to auto-ignite.

Ideally, we want the fuel mixture to only ignite when there is a timed spark event. If it ignites at the wrong time, the force can turn the crank the wrong way (bad), and otherwise put tremenous shock and stress on the engine internals -- this is essentially what knock (preignition or detonantion) refers to: unplanned auto ignition of the fuel that can damage the motor from the stresses it creates.

Higher heat and cylinder pressure (affected by boost and piston CR, as well as timing advance -- spark events tend to have flame kernels that keep high heat on the piston, thus more timing, also means more in-clyinder heat that doesn't have as much time to dissipate before the next rotation) increase the likelihood that the fuel will auto ignite, so for applciations with higher CR's, boost (or even excessive heat under load), a higher octane is generally necessary (DI sytems can get around this somewhat, thanks to the super fine atomized high pressure fueling mix it creates and the ability to spray directly and precisely into the cylinder -- but that's another story).

There is a bit of a down side -- really high octane fuels are harder to ignite even when you want to -- thus a 120 octane fuel in a DD might be hard to turn over on a cold morning, and be more prone to misfires, whereas on a boosted, high CR track car that might work very well.

In general, there are no direct benefits running a hgiher than needed octane -- again, octane is all about preventing knock. The extra power is all based on cylinder pressure in the piston or engine speed, so unless you are running more timing, boost, higher CR pistons, etc, that might require a higher octane to run safely, it's not needed.

As a precaution on a very hot day (again, in-cylinder temps increase the chance of knock), running the car at constant high load on the track, the extra octane might be a reasonable precaution, in that it will prevent power loss/damage from possible knock events, but it will not give you any additonal power than you were already capable of making given your tune.

Incidentially, that is also why tuners will find better power on boosted cars by running a bit richer a mixture -- the extra fuel is not fully burnt, rather it just cools the piston, reducing heat, and therefore quenching possible knock.

Anybody want to add to/amend that?

Red__Zed · 11-06-2011, 04:44 PM

Quote:

Originally Posted by Jordo!

Octane refers to how easily the fuel will spontaneously ignite, as in from heat or pressure (which also increases heat); the higher the number, the less likely to auto-ignite.

Ideally, we want the fuel mixture to only ignite when there is a timed spark event. If it ignites at the wrong time, the force can turn the crank the wrong way (bad), and otherwise put tremenous shock and stress on the engine internals -- this is essentially what knock (preignition or detonantion) refers to: unplanned auto ignition of the fuel that can damage the motor from the stresses it creates.

Higher heat and cylinder pressure (affected by boost and piston CR, as well as timing advance -- spark events tend to have flame kernels that keep high heat on the piston, thus more timing, also means more in-clyinder heat that doesn't have as much time to dissipate before the next rotation) increase the likelihood that the fuel will auto ignite, so for applciations with higher CR's, boost (or even excessive heat under load), a higher octane is generally necessary (DI sytems can get around this somewhat, thanks to the super fine atomized high pressure fueling mix it creates and the ability to spray directly and precisely into the cylinder -- but that's another story).

There is a bit of a down side -- really high octane fuels are harder to ignite even when you want to -- thus a 120 octane fuel in a DD might be hard to turn over on a cold morning, and be more prone to misfires, whereas on a boosted, high CR track car that might work very well.

In general, there are no direct benefits running a hgiher than needed octane -- again, octane is all about preventing knock. The extra power is all based on cylinder pressure in the piston or engine speed, so unless you are running more timing, boost, higher CR pistons, etc, that might require a higher octane to run safely, it's not needed.

As a precaution on a very hot day (again, in-cylinder temps increase the chance of knock), running the car at constant high load on the track, the extra octane might be a reasonable precaution, in that it will prevent power loss/damage from possible knock events, but it will not give you any additonal power than you were already capable of making given your tune.

Incidentially, that is also why tuners will find better power on boosted cars by running a bit richer a mixture -- the extra fuel is not fully burnt, rather it just cools the piston, reducing heat, and therefore quenching possible knock.

Anybody want to add to/amend that?

good post, good info. Octane is always one of those confusing specs for most people. Maybe we should try and get a reference thread together for info on fuels if people would find that helpful?

wstar · 11-07-2011, 10:00 AM

Quote:

Originally Posted by Jordo!

As a precaution on a very hot day (again, in-cylinder temps increase the chance of knock), running the car at constant high load on the track, the extra octane might be a reasonable precaution, in that it will prevent power loss/damage from possible knock events, but it will not give you any additonal power than you were already capable of making given your tune.

Incidentially, that is also why tuners will find better power on boosted cars by running a bit richer a mixture -- the extra fuel is not fully burnt, rather it just cools the piston, reducing heat, and therefore quenching possible knock.

Anybody want to add to/amend that?

I'll add a little to this: what I've seen tuning this car with UpRev (various internet posts from dyno tuners, mostly lines up with what I heard from mine) is that on N/A cars, there's not much point tuning the timing on our engine. Whatever you set the tune to is basically just a baseline, and the car adjusts on its own based on knock sensor feedback. To quote from UpRev's own Tuning Guide:

Quote:

On the newer vehicles equipped with VVEL, the ignition advance algorithms rely heavily on knock sensor feedback. In
many cases it is not possible to make the ECU run more advance because as soon as you increase the values it hears
something on the knock sensor and adjusts accordingly. For VVEL vehicles you WILL still have to pull timing for forced
induction applications so that it won’t ping before it has a chance to do any learning. However for NA applications about
all you can do is pull back the high spots and smooth the table out. The ECU will do the rest on it’s own. In our testing
we found that pulling LARGE values from the main ignition table caused a LARGE power drop on the first run, but after a
few consecutive runs the ECU would advance the ignition right back to where it was before based on knock sensor
feedback.

Given the above, I think it's highly likely that if you reset the ECU and put in a little learn time on a higher-octane fuel, chances are the ECU will pick up a bit more timing advance on its own resulting in some small power gains. It might be difficult to manage switching back and forth between race gas and 93 octane this way though, without getting more knock than you want on the way back to 93 (hence it's better to have specific maps as decent starting points).

The track I was at this weekend sells an unleaded 98 (Sunoco 260 GTX. They also had a 110 but it was Leaded). I showed up with a full tank of my usual 93, and topped off with several gallons of the 98 as we went through the weekend, avoiding fuel starve issues. I figured as the heat went up it was good for a little detonation insurance policy, might help clean the engine out a little as well. I wouldn't have been surprised if a full tank of the stuff would net a slight power gain once the ECU adjusted, but IMHO it's really not worth worrying about. By the end of the weekend I was probably running about 40% 93 and 60% 98, and now I'll mix it back to all-93 over my next few gas station trips.

Methodical4u · 11-06-2011, 04:38 PM

good post... very informative. I started this thread because it seems like the exhaust/intake part of our engines is pretty well maxed out, so perhaps we could look to fuel to somehow add more power. I personally don't want to go FI... I also don't have the money to do so right now and if I did have it I wouldn't spend 10 grand to do it. The intakes are about as good as they are going to get. Motordyne's manifold, while very well made is sort of hit and miss from one car to the next... no cams because there is no VVEL crack... in general there isn't much left to do I guess.

MightyBobo · 11-06-2011, 04:53 PM

Quote:

Originally Posted by Methodical4u

good post... very informative. I started this thread because it seems like the exhaust/intake part of our engines is pretty well maxed out, so perhaps we could look to fuel to somehow add more power. I personally don't want to go FI... I also don't have the money to do so right now and if I did have it I wouldn't spend 10 grand to do it. The intakes are about as good as they are going to get. Motordyne's manifold, while very well made is sort of hit and miss from one car to the next... no cams because there is no VVEL crack... in general there isn't much left to do I guess.

If you cant get more air into the motor, adding "better" fuel is a waste of time anyway.

Methodical4u · 11-06-2011, 05:14 PM

Quote:

Originally Posted by MightyBobo

If you cant get more air into the motor, adding "better" fuel is a waste of time anyway.

so any idea on how to get more air?

Red__Zed · 11-06-2011, 05:18 PM

Quote:

Originally Posted by Methodical4u

so any idea on how to get more air?

Honestly, doing lots of "little things" to add power is just not the smartest path to take. You spend almost as much as you would to go FI, and it leaves the car just as (if not more so) unreliable as it would be with boost.

370guy · 11-06-2011, 05:31 PM

Ok, I had a GT500 before my Z and have tried every fuel possible. Heres What ive found.

Basics of higher octane, allows you to safely run more advanced timing without the fear of detonation. So it is more valuable on forced induction cars than NA builds because the FI have more to gain off timing changes. So now to the options

1. E85. corn fuel. Its cheap and has and advanced level of octane far exceeding regular pump gas. Advantages = more timing, more power, CHEAP! Disadvantages = very VERY corrosive, upgraded fuel lines, pumps fitting, and injectors required. hard on motor, hard to come by in some places

2. C16. 116 octane. come in 2 variants, leaded and non-leaded. non leaded required by cars WITH catalytic convertors. Advantages = BIG power, smells awesome (opinion i guess), basic fuel system upgrades required Disadvantages = Very Expensive, Terrible economy

3. 100 octane. sold in some gas stations same advantges as above but with basic tuning can be run on stock fuel system.

Know for the curve ball!!!
Methanol Injection! allows you to run advanced timing on pump gas! basically increases the effective of octane of what ever is in the tank. Advantages = Its washer fluid so its cheap! Horsepower. Disadvantages = Seperate methanol system required for us (pumps, lines, tanks etc...) when you run out car can bnecome unsafe (if its tuned for the Meth and it doesnt get it you have problems)

So in conclusion (sorry fo rthe long post) there are advantages and disadvantages for all fuels. You gotta choose whats right for you. But as a rule of thumb, NA cars dont need to super high octane 91-93 is generally good enough

Methodical4u · 11-06-2011, 05:44 PM

There are a lot of people who will tell you methanol injection on an NA motor isn't going to do a whole lot... i've done a lot of looking into it myself.

370guy · 11-06-2011, 05:47 PM

It wont for the sheer fact that the timing adjustments where the enhanced ocatane levels that methanol will let you achieve wont make a big difference on an NA car. you could pick up maybe 5-10 WHP MAYBE but with the price of the kit and all the tuning required to make it run well wouldnt be worth it at all. your looking at 500 for a basic Kit then install then who knnows how many hours of tuning. Id never put it on an NA car

Red__Zed · 11-06-2011, 05:49 PM

Quote:

Originally Posted by 370guy

It wont for the sheer fact that the timing adjustments where the enhanced ocatane levels that methanol will let you achieve wont make a big difference on an NA car. you could pick up maybe 5-10 WHP MAYBE but with the price of the kit and all the tuning required to make it run well wouldnt be worth it at all. your looking at 500 for a basic Kit then install then who knnows how many hours of tuning. Id never put it on an NA car

maybe with ITBs

11-06-2011, 03:59 PM	#4 (permalink)
MightyBobo A True Z Fanatic Join Date: Feb 2009 Location: Las Vegas, NV Posts: 8,465 Drives: No cars; only bikes Rep Power: 53	Found it... http://www.neufamily.org/images/67novagallery/ __________________ I don't own a car anymore.

11-06-2011, 04:14 PM	#5 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Octane refers to how easily the fuel will spontaneously ignite, as in from heat or pressure (which also increases heat); the higher the number, the less likely to auto-ignite. Ideally, we want the fuel mixture to only ignite when there is a timed spark event. If it ignites at the wrong time, the force can turn the crank the wrong way (bad), and otherwise put tremenous shock and stress on the engine internals -- this is essentially what knock (preignition or detonantion) refers to: unplanned auto ignition of the fuel that can damage the motor from the stresses it creates. Higher heat and cylinder pressure (affected by boost and piston CR, as well as timing advance -- spark events tend to have flame kernels that keep high heat on the piston, thus more timing, also means more in-clyinder heat that doesn't have as much time to dissipate before the next rotation) increase the likelihood that the fuel will auto ignite, so for applciations with higher CR's, boost (or even excessive heat under load), a higher octane is generally necessary (DI sytems can get around this somewhat, thanks to the super fine atomized high pressure fueling mix it creates and the ability to spray directly and precisely into the cylinder -- but that's another story). There is a bit of a down side -- really high octane fuels are harder to ignite even when you want to -- thus a 120 octane fuel in a DD might be hard to turn over on a cold morning, and be more prone to misfires, whereas on a boosted, high CR track car that might work very well. In general, there are no direct benefits running a hgiher than needed octane -- again, octane is all about preventing knock. The extra power is all based on cylinder pressure in the piston or engine speed, so unless you are running more timing, boost, higher CR pistons, etc, that might require a higher octane to run safely, it's not needed. As a precaution on a very hot day (again, in-cylinder temps increase the chance of knock), running the car at constant high load on the track, the extra octane might be a reasonable precaution, in that it will prevent power loss/damage from possible knock events, but it will not give you any additonal power than you were already capable of making given your tune. Incidentially, that is also why tuners will find better power on boosted cars by running a bit richer a mixture -- the extra fuel is not fully burnt, rather it just cools the piston, reducing heat, and therefore quenching possible knock. Anybody want to add to/amend that? __________________ Enjoy it. Destroy it. Last edited by Jordo!; 11-06-2011 at 04:23 PM.

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11-06-2011, 03:40 PM	#3 (permalink)
Methodical4u A True Z Fanatic Join Date: Jun 2011 Location: Maryland Posts: 1,393 Drives: 11 370 6mt pw w/sp Rep Power: 16	so back to my other question... since the VVEL cannot be changed, can the timing of the engine still be changed? Basically i'm saying... if I wanted to run race gas for a run down the 1/4 and I needed to tune for it, can the timing be advanced due to the higher octane to maximize power? OR is that all part of the VVEL?

11-06-2011, 04:38 PM	#8 (permalink)
Methodical4u A True Z Fanatic Join Date: Jun 2011 Location: Maryland Posts: 1,393 Drives: 11 370 6mt pw w/sp Rep Power: 16	good post... very informative. I started this thread because it seems like the exhaust/intake part of our engines is pretty well maxed out, so perhaps we could look to fuel to somehow add more power. I personally don't want to go FI... I also don't have the money to do so right now and if I did have it I wouldn't spend 10 grand to do it. The intakes are about as good as they are going to get. Motordyne's manifold, while very well made is sort of hit and miss from one car to the next... no cams because there is no VVEL crack... in general there isn't much left to do I guess.

11-06-2011, 05:31 PM	#12 (permalink)
370guy Enthusiast Member Join Date: Sep 2011 Location: knoxvile, TN Posts: 298 Drives: 370+Viper+Vette=Fast Rep Power: 14	Ok, I had a GT500 before my Z and have tried every fuel possible. Heres What ive found. Basics of higher octane, allows you to safely run more advanced timing without the fear of detonation. So it is more valuable on forced induction cars than NA builds because the FI have more to gain off timing changes. So now to the options 1. E85. corn fuel. Its cheap and has and advanced level of octane far exceeding regular pump gas. Advantages = more timing, more power, CHEAP! Disadvantages = very VERY corrosive, upgraded fuel lines, pumps fitting, and injectors required. hard on motor, hard to come by in some places 2. C16. 116 octane. come in 2 variants, leaded and non-leaded. non leaded required by cars WITH catalytic convertors. Advantages = BIG power, smells awesome (opinion i guess), basic fuel system upgrades required Disadvantages = Very Expensive, Terrible economy 3. 100 octane. sold in some gas stations same advantges as above but with basic tuning can be run on stock fuel system. Know for the curve ball!!! Methanol Injection! allows you to run advanced timing on pump gas! basically increases the effective of octane of what ever is in the tank. Advantages = Its washer fluid so its cheap! Horsepower. Disadvantages = Seperate methanol system required for us (pumps, lines, tanks etc...) when you run out car can bnecome unsafe (if its tuned for the Meth and it doesnt get it you have problems) So in conclusion (sorry fo rthe long post) there are advantages and disadvantages for all fuels. You gotta choose whats right for you. But as a rule of thumb, NA cars dont need to super high octane 91-93 is generally good enough

11-06-2011, 05:44 PM	#13 (permalink)
Methodical4u A True Z Fanatic Join Date: Jun 2011 Location: Maryland Posts: 1,393 Drives: 11 370 6mt pw w/sp Rep Power: 16	There are a lot of people who will tell you methanol injection on an NA motor isn't going to do a whole lot... i've done a lot of looking into it myself.

11-06-2011, 05:47 PM	#14 (permalink)
370guy Enthusiast Member Join Date: Sep 2011 Location: knoxvile, TN Posts: 298 Drives: 370+Viper+Vette=Fast Rep Power: 14	It wont for the sheer fact that the timing adjustments where the enhanced ocatane levels that methanol will let you achieve wont make a big difference on an NA car. you could pick up maybe 5-10 WHP MAYBE but with the price of the kit and all the tuning required to make it run well wouldnt be worth it at all. your looking at 500 for a basic Kit then install then who knnows how many hours of tuning. Id never put it on an NA car