I'm interested in having a discussion about this issue with people who are open minded about the 1FZ and have some technical or practical experience to share.
Basically, the hypothesis is that the Toyota 1FZ-FE is designed run on a "minimum" of 87 octane fuel, but will perform better, both in overall power, economy and possibly even engine temperature, if higher octane is used, even as high as 96+ (U.S. rated, not RON). Yes, I said 96, which is much higher than most of us will ever see.
Where this idea got started is that I read a 1992 report that quoted Toyota engineers about several aspects of the “new” 1FZ-FE. Some of the comments included the fact that Toyota designed the 1FZ to be over bored and rebuilt at least 2 times with a total service life of more than 900,000Km.
When dealing with the new fuel system, they basically stated that the 1FZ’s ignition, engine management system allowed the engine to run normally on 87 octane fuel, while adding performance when using higher octane premium fuel. The article didn’t go into detail, so I did a little research to see if this could be true. Because until now, I was in the camp that premium had no benefit.
What I found leads me to believe that the 1FZ is not specificly designed to run only on 87 octane fuel, much like the 3F and 3FE before it. It appears to be specificly designed to peak perform on higher octane fuel, not unlike many newer engines today or other specificly higher performance engines, but it also has the added advantage of being able to run on the lower octane, faster burning fuel down to 87 octane, because of it’s superior engine management system that includes twin knock sensors.
Basically, most older engine ignition mapping systems and even some newer engines, including those with knock sensors and advanced computers are designed to run where the ignition is not allowed to advance to the point that knocking could occur under normal conditions when running 87. These engine's mapping systems do not allow for further performance or timing advance with premium fuel, because the knock sensor is a back up system only to help retard the ignition under abnormal circumstances when using the lower octane fuel. These engines "could" possible perform better with lower octane fuel, if they were manually advanced, but are otherwise limited by their computer and ignition systems.
The 1FZ appears to have a wider range where the computer will allow the ignition to advance to a point that would otherwise damage the engine on low octane fuel had there been no knock sensors, but because there are two knock sensors and they are reliable, Toyota engineers allowed the engine to run over a wider mapping range that allows it to take advantage of the lack of detonation of higher octane fuel.
This is what I believe based on my research.
So, what I’d like to know is to what degree the improvement is, however minimal it might end up being. There aren’t too many ways to quantify the difference in low octane and high octane use without a dyno, but many people have scangauges and these are about as close as we’re going to get.
So, if anyone wants to play experimenting between the higher and lower octane fuels, the things to look for are there any differences in MPG, HP, IGN and engine temp readings driving under the same conditions. As well as any quantifiable results in how the engine runs. When it comes to IGN, the difference are going to be most noticable at WOT and when first getting on the throttle off of idle or low rpm, I think. Remember, the IGN and other readings appear to lag realtime by a few seconds.
My goal is not to prove that it’s economically viable to run higher octane fuel, but to prove that there is a difference and figure out what the difference is, however small it might be. In the end, it may be so small, that other than a slightly smoother engine, the difference may not enough to significantly notice, I don't know. For example, a 5 h.p. increase or 1 mpg increase, however real, is pretty hard to quantify and prove, since very slight changes in other conditions can have the same effect. So, we'll see.
Basically, the hypothesis is that the Toyota 1FZ-FE is designed run on a "minimum" of 87 octane fuel, but will perform better, both in overall power, economy and possibly even engine temperature, if higher octane is used, even as high as 96+ (U.S. rated, not RON). Yes, I said 96, which is much higher than most of us will ever see.
Where this idea got started is that I read a 1992 report that quoted Toyota engineers about several aspects of the “new” 1FZ-FE. Some of the comments included the fact that Toyota designed the 1FZ to be over bored and rebuilt at least 2 times with a total service life of more than 900,000Km.
When dealing with the new fuel system, they basically stated that the 1FZ’s ignition, engine management system allowed the engine to run normally on 87 octane fuel, while adding performance when using higher octane premium fuel. The article didn’t go into detail, so I did a little research to see if this could be true. Because until now, I was in the camp that premium had no benefit.
What I found leads me to believe that the 1FZ is not specificly designed to run only on 87 octane fuel, much like the 3F and 3FE before it. It appears to be specificly designed to peak perform on higher octane fuel, not unlike many newer engines today or other specificly higher performance engines, but it also has the added advantage of being able to run on the lower octane, faster burning fuel down to 87 octane, because of it’s superior engine management system that includes twin knock sensors.
Basically, most older engine ignition mapping systems and even some newer engines, including those with knock sensors and advanced computers are designed to run where the ignition is not allowed to advance to the point that knocking could occur under normal conditions when running 87. These engine's mapping systems do not allow for further performance or timing advance with premium fuel, because the knock sensor is a back up system only to help retard the ignition under abnormal circumstances when using the lower octane fuel. These engines "could" possible perform better with lower octane fuel, if they were manually advanced, but are otherwise limited by their computer and ignition systems.
The 1FZ appears to have a wider range where the computer will allow the ignition to advance to a point that would otherwise damage the engine on low octane fuel had there been no knock sensors, but because there are two knock sensors and they are reliable, Toyota engineers allowed the engine to run over a wider mapping range that allows it to take advantage of the lack of detonation of higher octane fuel.
This is what I believe based on my research.
So, what I’d like to know is to what degree the improvement is, however minimal it might end up being. There aren’t too many ways to quantify the difference in low octane and high octane use without a dyno, but many people have scangauges and these are about as close as we’re going to get.
So, if anyone wants to play experimenting between the higher and lower octane fuels, the things to look for are there any differences in MPG, HP, IGN and engine temp readings driving under the same conditions. As well as any quantifiable results in how the engine runs. When it comes to IGN, the difference are going to be most noticable at WOT and when first getting on the throttle off of idle or low rpm, I think. Remember, the IGN and other readings appear to lag realtime by a few seconds.
My goal is not to prove that it’s economically viable to run higher octane fuel, but to prove that there is a difference and figure out what the difference is, however small it might be. In the end, it may be so small, that other than a slightly smoother engine, the difference may not enough to significantly notice, I don't know. For example, a 5 h.p. increase or 1 mpg increase, however real, is pretty hard to quantify and prove, since very slight changes in other conditions can have the same effect. So, we'll see.