GX460 ECM Remapping for Regular Gas? (1 Viewer)
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I have been running 87 in my 470 since the day I bought it. And I pull a camp trailer. I use 87 in my 460 also. I tested a tank of high octane and did not find any difference in power or fuel economy while towing. This has been debated a lot all over every forum. If you feel better paying more. Great go for it. My 470 has 175k on it and no issues. My 460 has 150 k and no issues. I did not buy them new but have put quite a few miles on them with 87 octane.
Worrying about the price of fuel and owning a GX dont really compute. I bought this thing knowing it gets horrible mpg and takes premium. I also know that it will last forever if i follow lexus requirements. Sorry, but I am not going to worry about $10 per fill up and take a chance on ruining my $40k+ vehicle.
^ This.
re_guderian
SILVER Star
Except there's literally no "chance" of you "ruining" your vehicle. At all. None. You will simply have paid $5,000-$8,000 more in gasoline costs over a 150,000 mile span. If you can't think of anything you'd rather do with 8 grand, then you got @BOUNDER kind of money... 
. You probably also think that changing your own oil will void your warranty. Or that 3,000 mile oil change intervals will prolong the life of your vehicle. But it won't, because if you've got THAT kind of money, you're not keeping this vehicle for the duration of time that would show a meaningful detriment to longevity of a 5-7,000 mi OCI v 3k.
I collected the data on another Toyota I owned that "required" premium. The extra cost paid never came close to making up for the slight increase in MPG. It may make "environmental sense", in that you're burning slightly less fuel, but if one REALLY cared that much about the environment, one wouldn't be driving a vehicle like this on the regular...
. You probably also think that changing your own oil will void your warranty. Or that 3,000 mile oil change intervals will prolong the life of your vehicle. But it won't, because if you've got THAT kind of money, you're not keeping this vehicle for the duration of time that would show a meaningful detriment to longevity of a 5-7,000 mi OCI v 3k.I collected the data on another Toyota I owned that "required" premium. The extra cost paid never came close to making up for the slight increase in MPG. It may make "environmental sense", in that you're burning slightly less fuel, but if one REALLY cared that much about the environment, one wouldn't be driving a vehicle like this on the regular...
Except there's literally no "chance" of you "ruining" your vehicle. At all. None. You will simply have paid $5,000-$8,000 more in gasoline costs over a 150,000 mile span. If you can't think of anything you'd rather do with 8 grand, then you got @BOUNDER kind of money...
I collected the data on another Toyota I owned that "required" premium. The extra cost paid never came close to making up for the slight increase in MPG. It may make "environmental sense", in that you're burning slightly less fuel, but if one REALLY cared that much about the environment, one wouldn't be driving a vehicle like this on the regular...
Something to consider, higher octane resists knock. Yes the ECU can compensate and that's where the slightly poorer performance and fuel efficiency comes in. Simply put for me personally I'll take the few extra $$ to make 100% sure nothing happens.
I agree about the last part, I bought both GX's knowing full damn well the fuel economy was s***. It just is what it is. This is one reason why I sold the 470 and bought a RAV4 Prime though, getting 35-90+ MPG week in and week out is starting to save some money with bidenflation's high fuel cost. Almost 3,600 miles in and we are at a lifetime average of just over 40 mpg total. We do a lot of highway miles @65-75 mph so the engine's MPG suffers a bit but still gets more than double the 470 we replaced it with and our 460. Check out these two examples.
re_guderian
SILVER Star
Yeah, I had a Ford C-Max Energi PEHV that I used for my city driving. ~80 MPG while I owned it. I'd go for days without the ICE ever starting, because I made so many short trips on electric only.
That's a good return. Precisely! The kid's school is 0.99mi away so the short inefficient trip and a lot of idling really costed us some serious coin. I wish Toyota would do a similar drivetrain in the next GX instead of that new Tundra V6 turbo hybrid thing. I just do not like that sort of setup. If I get the itch to sell my 460 after we move to Idaho I just might have to buy either an Atlis XT or a ... *cough* Tesla Cyber Truck if Toyota comes out with something I don't like in the next GX. LOL The Rivian while really nice and kitted out is just too much coin for my taste.
If there was a performance/knock issue associated with 87, it would manifest itself in reduced ignition timing, higher coolant temperatures, and probably higher long term fuel trims. I watch my engine pretty closely with Torque Pro and have noticed no quantifiable difference any any of those, regardless of if running 91/93 or 87 that is 10% ethanol here in MO.
There seems to be a slight reduction in fuel economy, but today I happened to get nearly 20 mpg on the way home from filling up with 87 - so I'm not even sure that's been "real" and it would take dozens of tanks of testing to confirm it either way. Either way, I don't think running 87 would cause potential wear of the GX or shorten it's lifespan, as none of the things I mentioned above really affect common wear items (piston bores, rod and main bearings, etc) that are oil-lubricated. Also, keep in mind that both of those Million Mile Tundras with the 2UZ were the 87-octane versions that were rated at 276 horsepower - a full 11 more than the 91-octane 2UZ in our GX's. The GX must have a slightly different ECU tune, but the engine internals are the same.
So, it seems the risk is low given the number of 87-octane 2UZ's hitting seven-digit mileage. I think that if anyone wanted to really quantify this that they could run 87 for a few tanks to get the ECU fully "learned", then pull some full-throttle and part-throttle data runs on the same stretch of road, and log all sensor values during the runs. Then, reset the ECU by unhooking the battery, start running 91 until the ECU is learned again, and repeat the same runs under similar climatic conditions. I think that if this showed all sensor/engine parameters being pretty similar, we could conclude there really is not difference. If they aren't the same, then we would have some definitive data.
Looking for volunteers
There seems to be a slight reduction in fuel economy, but today I happened to get nearly 20 mpg on the way home from filling up with 87 - so I'm not even sure that's been "real" and it would take dozens of tanks of testing to confirm it either way. Either way, I don't think running 87 would cause potential wear of the GX or shorten it's lifespan, as none of the things I mentioned above really affect common wear items (piston bores, rod and main bearings, etc) that are oil-lubricated. Also, keep in mind that both of those Million Mile Tundras with the 2UZ were the 87-octane versions that were rated at 276 horsepower - a full 11 more than the 91-octane 2UZ in our GX's. The GX must have a slightly different ECU tune, but the engine internals are the same.
So, it seems the risk is low given the number of 87-octane 2UZ's hitting seven-digit mileage. I think that if anyone wanted to really quantify this that they could run 87 for a few tanks to get the ECU fully "learned", then pull some full-throttle and part-throttle data runs on the same stretch of road, and log all sensor values during the runs. Then, reset the ECU by unhooking the battery, start running 91 until the ECU is learned again, and repeat the same runs under similar climatic conditions. I think that if this showed all sensor/engine parameters being pretty similar, we could conclude there really is not difference. If they aren't the same, then we would have some definitive data.
Looking for volunteers
Some interesting info in this thread last year
forum.ih8mud.com
GX460 KCLV for premium vs regular gas
So - in my pursuit of trying to figure out regular vs. premium gas use for my GX460, I got myself deep into the rabbit hole that is the Toyota/Lexus ECU mapping for injection timing in trucks, how Toyota engines calculate injection timing, and how the knock feedback works. I can’t find any info...
forum.ih8mud.com
I change my own oil. Always have. I also follow the manufacturers recommendations for intervals.Except there's literally no "chance" of you "ruining" your vehicle. At all. None. You will simply have paid $5,000-$8,000 more in gasoline costs over a 150,000 mile span. If you can't think of anything you'd rather do with 8 grand, then you got @BOUNDER kind of money...
I collected the data on another Toyota I owned that "required" premium. The extra cost paid never came close to making up for the slight increase in MPG. It may make "environmental sense", in that you're burning slightly less fuel, but if one REALLY cared that much about the environment, one wouldn't be driving a vehicle like this on the regular...
It seems that there are quite a bit of folks here with misconceptions on how knock systems work and what is the best choice of fuel with long ended debates with anecdotal evidence and never any real data. I'm not going to tell anyone what to do with their property and at the end of the day if you want to save a few $$ at the pump you do you. For background I work specifically on steady state operations within engine calibration at an OEM. Every OEM does this similarly these days and Toyota vs Ford vs GM etc it's all going to be a similar control method as combustion is the same no matter then engine unless you are venturing into high fuel economy miller cycle engines. The larger difference between OEMs would be algorithms in response to impact events, however, every OEM is poaching workers from the other so it's much easier to keep control methods similar enough for one to pick up the ball running when that happens. In regards to Lexus and calibration more likely residing in Japan it really doesn't make much of a difference as their SW is shared between NA and JP markets and the larger differences are fuel quality and emissions.
How knock systems work:
First there are the knock sensors that are calibrated depending on the sensor, most of the sensors are the same as Denso supplies almost every OEM these days. The feedback is registered per each engine depending on the individual engine noise-vibration-harshness (NVH). Once the sensor is calibrated the ECM/PCM is able to listen to the noise depending on the filter on the knock sensor and the internal resistances and chips in the ECM/PCM. Once the prior steps have been completed, thresholds are set for a knock or SPI event. Knock events are generally 4-6,000 kPa cylinder pressure whereas an SPI can vary from 15,000-27,000kPa in a single event; SPI is generally only on boosted DI engines with very very low tendency to happen in a naturally aspirated application but not impossible and these events happen primarily in the 1000-2500RPM range when lugging the engine in a high load situation. Either way once the general feedback for what a knock event is classified as the thresholds can be set for the engine to respond to.
This is where things get interesting in terms of short term feedback and long term feedback. The thresholds for a knock event are set by engine air per cylinder (APC) and RPM with threshold variation depending on ranges of APC. Depending on the company one will use a few different levels of thresholds depending on APC and it will be calibrated to each cylinder as every cylinder is individually different even if they are similar due to the NVH differences and depending on how the harmonics of the engine work out. So if you are cruising down the highway at 2000rpm & 800apc (about an average cruising load) the engine will start off on the basehi table and slew the cams to the desired IMOP/EMOP (intake/exhaust max open position) and if a knock event occurs there will be a fast retard event that quickly retards spark/IMOP/EMOP/injection timing to compensate for said knock event and then returns to the desired basehi table bringing fueling and cams back with it. Now if you were to get multiple knock events in a row you would get multiple fast retard events in addition to incrementing your long term scalar that will slew the overall spark to baselo as a percentage (e.g if you learn .3 scalar you would be permanently slewed 30% towards baselo). Now long term scalar will learn back to 0.0 over time and it will always want to learn to 0.0.
Now let's assume one fills up with 87 octane and how the system would inherently respond. 87 octane will cause more knock events to occur at first and eventually the long term scalar will slew you towards the baselo where one will have low impact knock events that might violate the threshold by a small portion or just cause false knock due to the excessive noise. When you get to a low knock area in your tables then the long term scalar will learn back to the basehi causing you to create more high impact knock events to learn towards baselo again. Nowadays knock events can be very quiet inside the cabin and you really need to listen carefully to hear anything; more likely you can feel the torque output change in real time than you can hear a low impact knock event. If you are using a top tier 87 octane fuel it's entirely possible that the knock events remain below thresholds enough to stay at your basehi table, but more than likely you are going to be slewed to baselo. Basehi is going to be your best fuel economy metric.
The larger effect of using 87 is going to be multiple repeat low impact knock events that do not violate the thresholds along with the occasional high impact event that will wear your piston rings and combustion chamber down more rapidly than with premium fuel not including carbon buildup due to poorer quality detergents which lead to misfires, valve seat damage and catalytic converter damage due to constant dumping of fuel into the exhaust. If you were to use 87 octane from mile 1 more than likely a premium fueled vehicle from mile 1 would last longer; if that engine replacement/rebuild occurs 50k, 100k or 300k sooner than the premium fueled vehicle there's no real way to tell without data unfortunately (I haven't seen long term data comparing both). The better bet would be to create a new basehi map that pulled 5-7 degrees off across the board and run 87 on that so you can remain on basehi without the negative occurrences of low impact knock events with constant scalar learning causing higher impact knock events occasionally.
My recommendation depends on what you really want with your vehicle, if you buy and sell vehicles a lot and don't care how long it will last you then stick 87 in, but know that it probably won't last as long of a life. Personally I put premium in as the spread from regular to premium is 30cents where I live; either way I'm paying almost $100 a tank now. I also have my wife's car that runs e85 and gets 30mpg to offset my costs. I plan on keeping my vehicle for the next 10-15 foreseeable years if not longer and perform all my own maintenance no matter the job. A good medium would be to fill up with 87 and rotate premium in occasionally to help clean with higher quality detergents, add octane booster to your 87 if the price difference between regular and premium is worth it, and/or do more frequent fuel injection and cylinder carbon cleaning with seafoam or other DI system cleaners that help with carbon buildup (yes I know it is not DI, but carbon buildup will occur no matter what just at a slower rate; don't forget EGR/PCV carbon buildup). Frequent oil changes will also help with oil dilution, lubrication and carbon build up too.
Hope this helps some people to make a more informed decision since everyone has their own individual needs.
How knock systems work:
First there are the knock sensors that are calibrated depending on the sensor, most of the sensors are the same as Denso supplies almost every OEM these days. The feedback is registered per each engine depending on the individual engine noise-vibration-harshness (NVH). Once the sensor is calibrated the ECM/PCM is able to listen to the noise depending on the filter on the knock sensor and the internal resistances and chips in the ECM/PCM. Once the prior steps have been completed, thresholds are set for a knock or SPI event. Knock events are generally 4-6,000 kPa cylinder pressure whereas an SPI can vary from 15,000-27,000kPa in a single event; SPI is generally only on boosted DI engines with very very low tendency to happen in a naturally aspirated application but not impossible and these events happen primarily in the 1000-2500RPM range when lugging the engine in a high load situation. Either way once the general feedback for what a knock event is classified as the thresholds can be set for the engine to respond to.
This is where things get interesting in terms of short term feedback and long term feedback. The thresholds for a knock event are set by engine air per cylinder (APC) and RPM with threshold variation depending on ranges of APC. Depending on the company one will use a few different levels of thresholds depending on APC and it will be calibrated to each cylinder as every cylinder is individually different even if they are similar due to the NVH differences and depending on how the harmonics of the engine work out. So if you are cruising down the highway at 2000rpm & 800apc (about an average cruising load) the engine will start off on the basehi table and slew the cams to the desired IMOP/EMOP (intake/exhaust max open position) and if a knock event occurs there will be a fast retard event that quickly retards spark/IMOP/EMOP/injection timing to compensate for said knock event and then returns to the desired basehi table bringing fueling and cams back with it. Now if you were to get multiple knock events in a row you would get multiple fast retard events in addition to incrementing your long term scalar that will slew the overall spark to baselo as a percentage (e.g if you learn .3 scalar you would be permanently slewed 30% towards baselo). Now long term scalar will learn back to 0.0 over time and it will always want to learn to 0.0.
Now let's assume one fills up with 87 octane and how the system would inherently respond. 87 octane will cause more knock events to occur at first and eventually the long term scalar will slew you towards the baselo where one will have low impact knock events that might violate the threshold by a small portion or just cause false knock due to the excessive noise. When you get to a low knock area in your tables then the long term scalar will learn back to the basehi causing you to create more high impact knock events to learn towards baselo again. Nowadays knock events can be very quiet inside the cabin and you really need to listen carefully to hear anything; more likely you can feel the torque output change in real time than you can hear a low impact knock event. If you are using a top tier 87 octane fuel it's entirely possible that the knock events remain below thresholds enough to stay at your basehi table, but more than likely you are going to be slewed to baselo. Basehi is going to be your best fuel economy metric.
The larger effect of using 87 is going to be multiple repeat low impact knock events that do not violate the thresholds along with the occasional high impact event that will wear your piston rings and combustion chamber down more rapidly than with premium fuel not including carbon buildup due to poorer quality detergents which lead to misfires, valve seat damage and catalytic converter damage due to constant dumping of fuel into the exhaust. If you were to use 87 octane from mile 1 more than likely a premium fueled vehicle from mile 1 would last longer; if that engine replacement/rebuild occurs 50k, 100k or 300k sooner than the premium fueled vehicle there's no real way to tell without data unfortunately (I haven't seen long term data comparing both). The better bet would be to create a new basehi map that pulled 5-7 degrees off across the board and run 87 on that so you can remain on basehi without the negative occurrences of low impact knock events with constant scalar learning causing higher impact knock events occasionally.
My recommendation depends on what you really want with your vehicle, if you buy and sell vehicles a lot and don't care how long it will last you then stick 87 in, but know that it probably won't last as long of a life. Personally I put premium in as the spread from regular to premium is 30cents where I live; either way I'm paying almost $100 a tank now. I also have my wife's car that runs e85 and gets 30mpg to offset my costs. I plan on keeping my vehicle for the next 10-15 foreseeable years if not longer and perform all my own maintenance no matter the job. A good medium would be to fill up with 87 and rotate premium in occasionally to help clean with higher quality detergents, add octane booster to your 87 if the price difference between regular and premium is worth it, and/or do more frequent fuel injection and cylinder carbon cleaning with seafoam or other DI system cleaners that help with carbon buildup (yes I know it is not DI, but carbon buildup will occur no matter what just at a slower rate; don't forget EGR/PCV carbon buildup). Frequent oil changes will also help with oil dilution, lubrication and carbon build up too.
Hope this helps some people to make a more informed decision since everyone has their own individual needs.
re_guderian
SILVER Star
Appreciate the detailed explanation. My sense is that for all practical purposes, the debate is mostly academic. You would need to quantify the last statement above to make it have any real importance, and anecdotal data all points to it being a non-issue over the typical lifespans of these rigs (up to about 300k) while there is virtually no compelling data that indicates meaningful negative impacts to useable life. I mean if we're talking about "only" lastng 500k miles v 600k, or 800 v 1M? We're clearly not talking about engine failure before 300k, since tons of folks have run GX's up to that point on regular with no "ruining" happening.
I’ve seen all kinds of failures with the majority not being fueling type related but the problem is the surrounding algorithms with torque control when you get into situations of consistent high knock; it really depends how oversparked the calibration is for 87. For instance Europe calibrators tend to find the knock line and then push past that for fuel economy where as North American market tends to back off 1 degree or so from the knock line. The system should learn it's way around the fuel either way, but for instance if the baselo table is also oversparked for 87 well then you will have knock no matter what without a recalibration of that map. My main point is that regular has a tendency to have higher intensity knock events than premium allowed within the knock system. Constant exposure will do damage, but there is not a way to quantify that without real failure data and unfortunately people are not doing engine teardowns upon failure or have live data of the failure occurrence.
If you’re smart about it you can avoid long lasting damage more than likely, but one really crappy blend of 87 from a no name station can break you. High heat and high load situations being your worst case scenarios such as hot desert runs without adequate cooling or fully loaded heading up Eisenhower pass etc I would not be pumping 87 in, even 91 octane will struggle if the baselo map is close enough to the knock line on premium. Daily driving under 3k rpm is more than likely not going to see large knock hits though; it just depends what you are doing and how much abuse the engine has seen prior to you owning it. If maintenance hasn’t been really kept up and carbon deposits are rampant then you already have a worse case scenario without proper cleaning. Knock events tend to kick these deposits loose and having them pinched between valve seats end with less compression/efficiency. It's all individualized per vehicle too; one engine might tolerate 87 for long periods of time while another might not like it immediately.
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Out west where I reside 91 isn't even an option. It's interesting that no mention of high altitude is in the owners manual. We have 85 or 86 for regular, 88 for mid grade and 90 for premium. I know that at higher elevations the oxygen level is lower. But if it were super critical that 91 be used then technically they shouldn't be sold here in higher elevation cities. And I'm only at a mile high. I usually put in premium but there are areas where only 85 or 88 is available.
By the way, I do use top tier gasoline when available.
r2m
Richard
For a trip over the continental divide, I'd go with the expensive stuff. Albeit, that's all I ever use, but especially for the high altitude and probably steep grades, I'd feel better with 91 - 95 octane (whichever you can get).
And again, for myself, I just plain seem to get better MPG from the more expensive stuff, which is a little bit of return on the extra $$ in the tank. So in the end I'm not really paying that extra .20¢/gallon, maybe more like .10¢ or .15¢ per gallon.
And again, for myself, I just plain seem to get better MPG from the more expensive stuff, which is a little bit of return on the extra $$ in the tank. So in the end I'm not really paying that extra .20¢/gallon, maybe more like .10¢ or .15¢ per gallon.
