1FZ and higher octane fuel technical discussion...

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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.
 

NaterGator

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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.
Holy crap, if you can find the source to that I'll be mighty impressed. If the engine was engineered to be rebuilt at least twice and go almost 1,000,000km :eek:


Anyways, there is a common misconception that higher octane fuel contains more "power" etc. It is usually simply used to prevent knocking in high compression engines; something that no LC can control via computer or spark advance. That said little tweaks can be made (VVT is an example) but to my knowledge the LC is basically only setup for minor spark advance/retard.

Interested to see where this thread goes, though :beer:
 
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The higher or lower energy with the different fuels will come up a lot in this type of discussion. It's important to point out this has nothing to do with more or less energy in the fuel. Its entirely about the fuel anti-knock qualities and whether one fuel's anti-knock qualities will allow the engine to run at peak performance when it no longer has to compensate for the lower anti-knock fuel.

9 to 1 compression is not low and there's a misconception that it is. All things considered, 9 to 1 would normally need as high as 96 octane to prevent knocking, but computer management and fuel injection of the 1FZ and other engines that rate that high are able to compensate. However, if you could ever run 96, you wouldn't need to utilize the computer management system to retard timing and compensate for the lower octane and it would run at peak performance. There's a lot more to it than just compression of course, but that's where the theory is headed. Most engines, especially older EFI engines and just about any other engine with basic ignition advance systems, won't allow the computer to take advantage of the of the lesser knocking fuel, because engineers don't want to risk the engine going beyond safe parameters while still using a higher knocking, lower octane fuel.

Everyone seems to get stuck on the idea that there's no reason to design a motor that runs better on 92+ and especially 96+ when it's not available. It's not that engineers went out of their way to design the motor to run on gas almost no one will ever see. It's that the engines, via their higher compression these days and other factors, naturally will run better on the higher octane if the engine management system will allow it. But many don't for the reasons I just mentioned. It's not worth the risk in case the timing advances too far on low octane fuel and the knock sensors aren't working properly.

If you wanted to design an engine specificly to run only on 87 octane or even lower octane, the first thing you'd do is reduce the compression to as low as 7 to 1 or maybe 8 to 1 maximum. You're mechanically making the engine 87 octane friendly, and thus needing no or little management to compenstate. But when you mechanically limit the engine's performance, you limit it across the board. On a new engine with more advanced managment, its better to crank up the mechanical design and use the computer management to limit the engine's perfermance depending on which fuel it happens to be using.

That’s my theory here, based on what I’m reading and I think a lot of newer Toyota and a few other engines also take advantage of lesser knocking fuel, when available, because the engineers had more confidence in their anti-knocking system design.

So, a reasonable question would be then, why would engineers make any engine with higher compression than 7 to 1, if they are going to limit the management system as if only 87 octane was available. That's a good question and the answer may be that even with the engine compensating for knock, a compensated 9 to 1 compression engine will still out perform a non-compensated 7 to 1 compression on the same type of fuel, all else being equal.

Again, my theory, still researching......
 
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FirstToy

 
 
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Brian,
this is an extension of this discussion-maybe people can read it so they understand what you are looking for in this thread
https://forum.ih8mud.com/80-series-tech/220692-regular-supreme-gas.html

The OM says,
Select Research Octane Number 91 (Octane Rating 87) or higher.
Use of unleaded fuel with an octane # or rating lower than stated above will cause persistent heavy knocking. If severe, this will lead to engine damage.

If your engine knocks..
[steady knocking while holding speed on level roads, see your dealer]

However, now and then, you may notice light knocking for a short time while accelerating or driving up hills. This is no cause for concern.

lexus recommends use of gasolines that contain detergent additives to avoid build up of engine deposits.
__________________________________________

I look at the knock sensors opposite- you can run lower octane for similar performance.

9:1 compression ratio-
I always thought of this not as "high" or "low" but rather as an efficient ratio for a gas pass. vehicle engine.
For 87octane, 9:1 is pretty efficient. If you go lower than it looses thermal efficiency. I think most cars are around 9:1 (?)

another factor is that the 1FZ is not a high revving engine. It develops all its power low.
Compared to Toyota's modern truck 6 cylinder- the 1GR - which has 10:1 yet runs regular pump gas great, about 50hp more, 2x the mpgs and ULEV 2

I honestly feel it is not economically advantageous to run higher octane fuel, but to do so if your engine requires it (knocking) or you are boosted.

just my thoughts
 

agomez

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when the weather is cool no knocking with 87...when it gets hot 90 or above lots of knocking go with surpreme....
 
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Well a couple quick things. The 1FZ is not high revving, but this is not about WOT. The ignition tends to advance the most at lower rpms and higher throttle, such as accelerating from 20 to 50 mph. This is my observation at least. The 1FZ is a very hard working engine, because it has to pull a 3 ton vehicle from 0 up to 60 or 70 mph and that takes plenty of energy. Even under normal throttle, we're talking more h.p and more torque than most Honda's peak out at. I'm not suggesting that the engine is stressed by any means, but that any differences at WOT and higher rpms will be affected at lower rpms under normal driving conditions as well.

If the engine is compensating for the 87, then it appear to run OK, but its not running at its peak and its not likely taking advantage of whatever extra energy is available in the lower octane fuel. If the engine was not compensating was allowed to run on the edge, just above the point where damage would occur as another thread suggested some races engines do, then it probably would run better on lower octane fuel, but more than likely Toyota engineers have compensated the engine to keep it as far from knock as possible on 87 octane. We don't know at what point the engine compensation kicks in on 87.

If the 1FZ was designed to run its peak on 87, then 87 would not be the bare minimum and I'm glad you posted that info out of the owner's manual, because I was going do to the same thing myself to illustrate that Toyota calls 87 the bare minimum. Had the 1FZ been specificly designed mechanically and electronicly to run on 87, then it should be able to run on even lower octane fuel under normal circumstances, just fine, but with lesser performance as the engine compenstates. What Toyota is saying that the 1FZ is only designed to compensate down to 87 and under certain circumstances, such as extreme loads, heavy tower, long steep grades combined with extreme heat, it's no longer able to compensate and would require a lesser knocking fuel.
 
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Isn't all we need to know is whether or not the 1FZ has a knock sensor?

If yes, then higher octane = more power and more efficiency under a load that normally would cause the engine to knock on a lower octane fuel.

If no, then no difference.

I know that higher octane fuel doesn't make more power on its own and accept that lower octane fuel, all else being equal, possibly has higher energy content.
 

Onur

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Isn't all we need to know is whether or not the 1FZ has a knock sensor?
The 1FZ has 2 knock sensors.

I know the technical paper that Brian is talking about. I have a .pdf of it and while it is informative, it is far from being both complete or in-depth. It is a brief paper given at an ASE conference in the early 1990's.

The engine is designed to be rebuilt a total of 2 times at 300,000kms at each interval (~186,000 miles)...most trucks on MUD have already passed this milestone and thus proven that the 1FZ is indeed a conservatively working engine (and as cary has always argued, easy on oil)...
 
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Isn't all we need to know is whether or not the 1FZ has a knock sensor?
.
Not if the timing map of a given engine will not allow the engine to advance to a point where it would otherwise be dangerous on 87 fuel. Many engines only use the knock sensor as a back up and rely mainly on a predetermined conservative ignition map based on 87 octane being used. On these engines, the improvement might not exist or be so minimal as to not be noticable.

If anyone is getting heavy pinging with the 1FZ on 87 under normal conditions, there might be other factors at play. Extreme ambient temps can affect this as well as load, but also carbon deposits on the pistons, which is probably the most likely cause for most higher mileage engines. If any engine is pinging, I have to imagine the engine is seriously underperforming at that point, because most likely the ignition is at the very limit of its compensation and is definately not running at peak performance.

As for why Toyota chose 300Km for its rebuilt intervals, my thoughts are that its a nice round metric number and the engineers were basing their figures on the 1FZ's primary use, which is as a commerical engine in overseas 3rd world countries or countries like South Africa, Australia, etc, and the large amount of interestate driving that we do here does not apply. Think like putting 187,000 exclusively city and dirt road driving on these engines, as opposed to about half of that being on the highway at constant speeds for sometimes hours at a time. I believe the 1FZ was designed to be a high performance commercial truck engine above all else. If engineers were rating how the engine would last between rebuilds on U.S. highways, they'd probably come up with something closer to 250K miles, still being conservative.
 

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Brian,

Can you give us your mileage numbers? From your posts, I assume you are running Sepreme gasoline with the highest octane rating.

Have you tried any octane booster? In 1985 I bought a 1980 Mazda 626 (I think it was an 80) and drove it back and forth from Houston to Lubbock for college. I once used a can of octane booster and made it about 70 miles further than I ever had on a tank of gas. I was told it could hurt my engine and never used it again. At the time I knew nothing about engines, not much has changed since but it has always intrigued me

I absolutely think threads like these are worth the read and I appreciate your effort.

Buck Buchanan
 

Onur

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I've always liked to think of this truck as a tractor engine with A/C (IIRC, it was either one of the Patterson brothers who said this or Brian MacGyver....forgot whom at this point).

While this discussion is technically interesting, we do not have enough information from Toyota themselves to really know what they were thinking when they designed the 1FZ-FE. It would be very interesting to be able to find one of the original 1FZ-FE engineers and talk to them about the history and development of the 1FZ. The ECU's are not changeable, so that really hinders our ability to understand and mess with ignition, fuel control systems, etc.

It is my belief that you could put the crappiest petrol you can find in the world in this engine and it will continue to putt-putt-putt along...heck, I wouldn't be surprised if you could piss in this thing and make it go....

:D

-o-
 

turbocruiser

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It is my belief that you could put the crappiest petrol you can find in the world in this engine and it will continue to putt-putt-putt along...heck, I wouldn't be surprised if you could piss in this thing and make it go....

:D

-o-
That is totally incorrect; remember that time you stalled so bad on the trail, well, I pissed in your tank right before that! :D :flipoff2: :D
 

FirstToy

 
 
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For real world data,
I use exclusively 85 (regular). In travelling from 30F - 120F (in relatively low-zero humidity), from sea level to 11,000'. In the CA desert, one can do all those conditions in 1 day.

I have not had an issue with pinging and no issues. I am interested to hear what you find but it won't change the use of regular for me. Unless I get knocking or force induce my engine... the worker bee gets the cheap stuff and will like it mister! ;)
 

Romer

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I like these kinds of threads

Good technical discussion, even if it turns out that we don't know enough some folks will have learned something as the level of the discussion isn't to low a level that most people can't understand.

I would highly dis-courage others from taking a chat tangent here as thats what ruins a lot of these threads.
 

turbocruiser

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I like these kinds of threads

Good technical discussion, even if it turns out that we don't know enough some folks will have learned something as the level of the discussion isn't to low a level that most people can't understand.

I would highly dis-courage others from taking a chat tangent here as thats what ruins a lot of these threads.
I guess as I made a mention of in the other very recent thread on this subject. I don't know how we will ever quantify this in the real world and unless we can somehow quantify this in the real world all the postulating and presuming is useless. More importantly, as also already mentioned, the thing about higher octane for many including me (and prolly you too Ken) is not so much if it makes 'more power' or if it offers 'more economy' it is simply a function of what works with a Forced Induction, specifically a turboed (don't know if it is the same with superchargers), 1FZFE. The fact that anything less than the premium grade puts the turboed 1FZFE at pre-detonation risk is reason enough to use it exclusively. It is also to me proof that, to an extent, even with the dual knock sensors at a particular point the engine cannot compensate for lower than required octane. Think about that for a flash - if a turboed 1FZFE will knock and rattle and roll with low and even mid grade gas isn't that proof (although the real mechanism is the higher combustion chamber pressures and temperatures) that the knock sensors, as good as they are, do indeed bottom out on octane that is too low to go with the power demands during driving!?! Inversely, the more octane you are able to run with the turboed rigs the less likely you are to ever even activate the knock sensors at reasonable boost pressures. Further, push the boost to the point that you get a little knock going with premium pump gas and then goto the race gas ... little knock goes away again. I think you see the point ... for many people it isn't about any extra "power" or "economy" ... it is about the octane and proper detonation. If however we really are going to give this nut a crack on the power and economy factors, I suggest that we establish a very duplicable methodology to measuring the differences, otherwise, well, I think I used the word useless above right. You get my drift. :cheers:
 

Onur

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While I understand the want to discuss fuel economy, I find that the very notion of "fuel economy" and 1FZ-FE to be oxymoronic.

These are tractor engines--albeit very high-tech and finely tuned tractor engines.

Nonetheless, we do not know enough about the complex computerized systems on-board to really be able to do much with the information that we do have...

I like it slow and like a donkey.

-o-
 

Romer

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I guess as I made a mention of in the other very recent thread on this subject. I don't know how we will ever quantify this in the real world and unless we can somehow quantify this in the real world all the postulating and presuming is useless. More importantly, as also already mentioned, the thing about higher octane for many including me (and prolly you too Ken) is not so much if it makes 'more power' or if it offers 'more economy' it is simply a function of what works with a Forced Induction, specifically a turboed (don't know if it is the same with superchargers), 1FZFE. The fact that anything less than the premium grade puts the turboed 1FZFE at pre-detonation risk is reason enough to use it exclusively. It is also to me proof that, to an extent, even with the dual knock sensors at a particular point the engine cannot compensate for lower than required octane. Think about that for a flash - if a turboed 1FZFE will knock and rattle and roll with low and even mid grade gas isn't that proof (although the real mechanism is the higher combustion chamber pressures and temperatures) that the knock sensors, as good as they are, do indeed bottom out on octane that is too low to go with the power demands during driving!?! Inversely, the more octane you are able to run with the turboed rigs the less likely you are to ever even activate the knock sensors at reasonable boost pressures. Further, push the boost to the point that you get a little knock going with premium pump gas and then goto the race gas ... little knock goes away again. I think you see the point ... for many people it isn't about any extra "power" or "economy" ... it is about the octane and proper detonation. If however we really are going to give this nut a crack on the power and economy factors, I suggest that we establish a very duplicable methodology to measuring the differences, otherwise, well, I think I used the word useless above right. You get my drift. :cheers:

Shaun,
I don't think you understood my point. I don't expect to solve it or come up with an answer. I just enjoyed the level of conversation. Kind of like two guys at a bar drinking some beers wondering some things and not coming to a resolution, but enjoying the conversation.

Kind of like wondering what cdan thinks when he is looking at my avatar. Is he thinking "handsome devil", "Damn thing still hasn't washed off" "Damn that Hants White" or "Why do I copy that damn Canadian" Unless he tells us we won't know.

I am supercharged so I run Premium anyways.
 
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Brian,

Can you give us your mileage numbers? From your posts, I assume you are running Sepreme gasoline with the highest octane rating.
Actually this will probably surprise you all. I have not run a single tank of higher than 87 octane. So I've not tried this to see how it performs in my truck. This is just something new that I thought about recently. I'm still not sure that I would pay the extra money, but I might try at least one tank of it on a trip I'm taking next week.

Right now my mostly highway mileage is running about 11-12 with an occasional 13 average if I'm mostly highway and keep my speeds at around 60. If I mix a lot of city in there or dirt roads, it gets down to 10 or even close to single digits. That's with my mods and Oregon's now year round 10% ethanol gas and 87 octane.

One of the things I'm kind of curious about is to see if there's a huge difference with the ignition mapping using a higher octane fuel. The scangauge can allow us to see this. Unfortunately, the numbers jump all over the place, so it's really hard to see what things are doing, much less compare to other numbers. If someone had a scantool that could record and map out the ignition timing under the same conditions, but different octane, that might be interesting. The scangauge also seems to pump out fairly accurate mpg and brake h.p. figures, which would be interesting to see on a graph using the different fuels.

If I do run a tank of premium, I will defiantely be taking scangauge measurements with the 87 stuff and trying to compare under similiar conditions with the higher octane.
 
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The fact that anything less than the premium grade puts the turboed 1FZFE at pre-detonation risk is reason enough to use it exclusively. It is also to me proof that, to an extent, even with the dual knock sensors at a particular point the engine cannot compensate for lower than required octane. Think about that for a flash - if a turboed 1FZFE will knock and rattle and roll with low and even mid grade gas isn't that proof (although the real mechanism is the higher combustion chamber pressures and temperatures) that the knock sensors, as good as they are, do indeed bottom out on octane that is too low to go with the power demands during driving!?! Inversely, the more octane you are able to run with the turboed rigs the less likely you are to ever even activate the knock sensors at reasonable boost pressures. Further, push the boost to the point that you get a little knock going with premium pump gas and then goto the race gas ... little knock goes away again. I think you see the point ... for many people it isn't about any extra "power" or "economy" ... it is about the octane and proper detonation. If however we really are going to give this nut a crack on the power and economy factors, I suggest that we establish a very duplicable methodology to measuring the differences, otherwise, well, I think I used the word useless above right. You get my drift. :cheers:
There is definately a limit on how much the stock ignition can compensate for knocking. Stock 1FZs find themselves knocking all the time, if the temps are hot and they are towing uphill or they have carbon deposits. To me this is evidence that there isn't much margin of error on 87 octane even on a stock engine. Add higher compression with a turbo or supercharger and you pretty much have to run higher octane, apparently. This is why 87 is the bare minimum, not the standard fuel for all occasionals, even with a stock 1FZ.

It's not that knock sensors can't detect it or aren't activated, its that the ignition and computer can only compensate so much. I suspect if this engine was designed specificly to run its peak on 87, that it would take a lot more to get it to knock than it does. As long as the knock sensors are not activating, then the engine will push the timing to its design limits and it run the most effeciently. The moment the knock sensors kick in, you're running less than peak effeciency.

Have you ever wondered why the 1FZ can so easily be turboed or supercharged with minimal or no changes to the computer and ignition mapping systems, yet yeild significant increases in power? I sure have. Same for the Toyota 3RZ and 5VZ and 2UZ, all modern Toyota designs from the same or later era than the 1FZ. All with factory supercharging options, with minimal or no changes to the engine management system and a factory backed warrenty. I think the explaination is the wider mapping parameters with the engine management systems of these engines and Toyota's complete confidence in their anti-knocking system.

But this is just my theory.
 
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landtank

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I did some knock testing when I was evaluating my MAF housing. I have the auto enginuity software so it could be recorded. What I would do is place the tranny in 2nd start mode and take off at the bottom of a hill full throttle. I never saw the timing retard under those conditions running 87 octane gas.

I have always been under the impression that our ECUs don't advance the spark past a preset value and only retard the spark if needed. But I have not tried to prove that either way.
 
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