turboale said:
All ECU’s are going to pull timing whenever there is knocking. The difference is probably compression ratio, fuel maps/timing advancement.
Regular Unleaded or Premium Unleaded?
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All ECU’s are going to pull timing whenever there is knocking. The difference is probably compression ratio, fuel maps/timing advancement.
hoser
SILVER Star
IIRC, ALL years of the UZJ100's recommend premium unleaded but can run on regular unleaded with "reduced" performance. Will somebody with an '00+ owner's manual give us the low down on this rumor?turboale said:
If nobody does before the evening, I found another 00 I'm going to go check out tonight, and it should have the book...
and yes, technicly your right... but if an ECU has mapping for both octanes, it could do a much better job of handling the lesser octane. (just throwing out ideas...)
and yes, technicly your right... but if an ECU has mapping for both octanes, it could do a much better job of handling the lesser octane. (just throwing out ideas...)
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Kaderabek
GOLD Star
I asked Christo if we needed to run 93 octane in our 1999 and he said yes. Every tank. That was enough for me, even when it was at $4.16/gallon here. 
TJK
(No, I didn't buy any that day.)
TJK
(No, I didn't buy any that day.)
Yeah,
I hear Asheville has up near the top in gas prices in the states. Definately high for the southeast! It was a good $.20 different from Savannah when the gas scare was going on...
ps, i cleared my inbox... didn't realize I only got room for 5 messages!??
I hear Asheville has up near the top in gas prices in the states. Definately high for the southeast! It was a good $.20 different from Savannah when the gas scare was going on...
ps, i cleared my inbox... didn't realize I only got room for 5 messages!??
ECU tunning from the factory is very conservative, they tried to tune the ECU for every possible situation like extreme heat, low octane fuel, high loads and then detune it one more step to be safe.
On a Honda Rice Rockets for instance, during a dyno pull with the lamba (O2 sensor) installed. It goes rich as you reach the last 2000rpm before redline. This is done to protect the engine from severe detonation at WOT which the ECU is on open loop mode. By tinkering with the ECU we were able to get another 5-7hp just by leaning the top end.
During part throttle and the ECU is on close loop, it is monitoring the O2 sensor, throttle position, RPM, ignition, MAF, coolant temp, knock sensor etc. If you are using 91 oct. fuel the ECU will advance the ignition timing to take advantage for the slower burning fuel. Wheras it will slightly retard ignition for 87 oct fuel. On more advanced engines there is a knock sensor for every cylinder so ignition timing can be advanced or retarded for a specific cylinder.
The burining of fuel and air mixture expands in different rates depending on altitude, octane and heat. The change of ignition timing is to comphensate for burn rate so that the maximum combustion pressure occurs about 45° ATDC (after top dead center) for maximum power.
A good example of slower and faster burn rate is when riding a bicycle. When trying to accelerate on a bike, you try and step on hard when the pedal reaches40° ATDC. In theory on a 91 oct. you continue to feed your weight on the pedal until it almost hits the bottom or 40° BBDC (before bottom dead center). While on 87 oct. which also has maxium cylinder pressure at 40° may already burn itself out sooner at 50° BBDC.
Octane requirements varies greatly on engine bore, stroke, combustion chamber design, the amount of EGR (exhaust gas recirculation) and how the fuel is introduced to the camber. The Toyota Prius runs a 13.5:1 and only requires 87 oct. and the new IS350 and 250 have 11.8:1 and 12.1:1 compression ratios and only requires premium but I think it the IS350 may make more power with race gas.
Back to the 2UZ-FE, I have no doubt 91 is capable of making more power than 87 on our engines, but the gains maybe marginal due to lower compression ratio. But I would definitly be putting 91 if I tow. Just my .02 cents.
Charleston
On a Honda Rice Rockets for instance, during a dyno pull with the lamba (O2 sensor) installed. It goes rich as you reach the last 2000rpm before redline. This is done to protect the engine from severe detonation at WOT which the ECU is on open loop mode. By tinkering with the ECU we were able to get another 5-7hp just by leaning the top end.
During part throttle and the ECU is on close loop, it is monitoring the O2 sensor, throttle position, RPM, ignition, MAF, coolant temp, knock sensor etc. If you are using 91 oct. fuel the ECU will advance the ignition timing to take advantage for the slower burning fuel. Wheras it will slightly retard ignition for 87 oct fuel. On more advanced engines there is a knock sensor for every cylinder so ignition timing can be advanced or retarded for a specific cylinder.
The burining of fuel and air mixture expands in different rates depending on altitude, octane and heat. The change of ignition timing is to comphensate for burn rate so that the maximum combustion pressure occurs about 45° ATDC (after top dead center) for maximum power.
A good example of slower and faster burn rate is when riding a bicycle. When trying to accelerate on a bike, you try and step on hard when the pedal reaches40° ATDC. In theory on a 91 oct. you continue to feed your weight on the pedal until it almost hits the bottom or 40° BBDC (before bottom dead center). While on 87 oct. which also has maxium cylinder pressure at 40° may already burn itself out sooner at 50° BBDC.
Octane requirements varies greatly on engine bore, stroke, combustion chamber design, the amount of EGR (exhaust gas recirculation) and how the fuel is introduced to the camber. The Toyota Prius runs a 13.5:1 and only requires 87 oct. and the new IS350 and 250 have 11.8:1 and 12.1:1 compression ratios and only requires premium but I think it the IS350 may make more power with race gas.
Back to the 2UZ-FE, I have no doubt 91 is capable of making more power than 87 on our engines, but the gains maybe marginal due to lower compression ratio. But I would definitly be putting 91 if I tow. Just my .02 cents.
Charleston
FWIW here's what my Toyota Land Cruiser 2005 Owner's Manual says verbatim:
"Octane Rating
Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher is recommended.
Use of unleaded gasoline with an octane rating or research octane number lower than stated above will cause persistent heavy knocking. If it is severe, this will lead to engine damage.
If your engine knocks ....
If you detect heavy knocking even when using the recommended fuel, or if you hear steady knocking while holding a steady speed on level roads, consult your Toyota dealer.
However, occasonally, you may notice light knocking for a short time while accelerating or driving up hills. This is normal and no need for concern."
It's been a long time (circa 1970s) since I worked in a gas station here in California. I can't remember what the primary number is on the label that's affixed to the pump: Octane Rating ... Research Number? or both?
My guess: "Octane Rating" ... comes in three flavors around here: 87, 89 or 91.
I use 91.
"Octane Rating
Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher is recommended.
Use of unleaded gasoline with an octane rating or research octane number lower than stated above will cause persistent heavy knocking. If it is severe, this will lead to engine damage.
If your engine knocks ....
If you detect heavy knocking even when using the recommended fuel, or if you hear steady knocking while holding a steady speed on level roads, consult your Toyota dealer.
However, occasonally, you may notice light knocking for a short time while accelerating or driving up hills. This is normal and no need for concern."
It's been a long time (circa 1970s) since I worked in a gas station here in California. I can't remember what the primary number is on the label that's affixed to the pump: Octane Rating ... Research Number? or both?
My guess: "Octane Rating" ... comes in three flavors around here: 87, 89 or 91.
I use 91.
I drive my LC about 8K mile per year, at 15mpg and with 91 octane costing around 15 cents more per gallon this works out to 22 cents per day more for 91 octane compared to 87 octane. Hey for that amount of money ($80.00 per year) I will stick with the 91 octane.
CivicFerio said:ECU tunning from the factory is very conservative, they tried to tune the ECU for every possible situation like extreme heat, low octane fuel, high loads and then detune it one more step to be safe.
On a Honda Rice Rockets for instance, during a dyno pull with the lamba (O2 sensor) installed. It goes rich as you reach the last 2000rpm before redline. This is done to protect the engine from severe detonation at WOT which the ECU is on open loop mode. By tinkering with the ECU we were able to get another 5-7hp just by leaning the top end.
During part throttle and the ECU is on close loop, it is monitoring the O2 sensor, throttle position, RPM, ignition, MAF, coolant temp, knock sensor etc. If you are using 91 oct. fuel the ECU will advance the ignition timing to take advantage for the slower burning fuel. Wheras it will slightly retard ignition for 87 oct fuel. On more advanced engines there is a knock sensor for every cylinder so ignition timing can be advanced or retarded for a specific cylinder.
The burining of fuel and air mixture expands in different rates depending on altitude, octane and heat. The change of ignition timing is to comphensate for burn rate so that the maximum combustion pressure occurs about 45° ATDC (after top dead center) for maximum power.
A good example of slower and faster burn rate is when riding a bicycle. When trying to accelerate on a bike, you try and step on hard when the pedal reaches40° ATDC. In theory on a 91 oct. you continue to feed your weight on the pedal until it almost hits the bottom or 40° BBDC (before bottom dead center). While on 87 oct. which also has maxium cylinder pressure at 40° may already burn itself out sooner at 50° BBDC.
Octane requirements varies greatly on engine bore, stroke, combustion chamber design, the amount of EGR (exhaust gas recirculation) and how the fuel is introduced to the camber. The Toyota Prius runs a 13.5:1 and only requires 87 oct. and the new IS350 and 250 have 11.8:1 and 12.1:1 compression ratios and only requires premium but I think it the IS350 may make more power with race gas.
Back to the 2UZ-FE, I have no doubt 91 is capable of making more power than 87 on our engines, but the gains maybe marginal due to lower compression ratio. But I would definitly be putting 91 if I tow. Just my .02 cents.
Charleston
Good example, except you get more efficiency if you carry the power stroke all the way to the bottom (BDC) on your bicycle example.
Simply put though, the higher octane rating allows more compression without having it “pre-ignite” therefore you can run more timing advancement.
In other words, if you run high test in a normal engine you will not see a difference because there will be no additional timing advancement. Only if you have timing advancement will you see more power.
Is Sport Trucks By Dean still in Moore Park?
I've got an 06 with the new variable valve timing engine. The owner's manual states that you should use premium, but that you can use regular and will get "reduced performance."
I always buy premium, but had one tank where I accidentally filled with regular. I noticed no difference in performance, and I had particularly good gas mileage on that tank.
Regardless, I'm not going to take any chances and continue filling with premium.
I always buy premium, but had one tank where I accidentally filled with regular. I noticed no difference in performance, and I had particularly good gas mileage on that tank.
Regardless, I'm not going to take any chances and continue filling with premium.
tech_dog said:
I'll trade you even for my 99, its already broke in
We don't seem to have "91" up here in NH. Our selections are 87, 89, 93. The door to tha gas cap says "91" so I run 93 to 1/2 tank, then 89 to 1/2 tank, then back to 93 and so forth - hence my mean average of "91" - how's that for math.
I've been back and forth several times since I bought in February. When running premium I get atleast 1MPG better and I definitely notice better performance. Maybe not extreme, but I notice it takes off the line with less pedal and it just seems smoother.
from the 2000 Owner's Manual...
"Fuel type: Premium UNLEADED gasoline, Octane Rating 91 or higher for optimum engine performance. However, if such premium type cannot be obtained, you may temporarily use unleaded gasoline with an Octane Rating as low as 87."
It goes on to warn of knocking risks for lower octane, etc.....
With a normally aspirated engine, I don't think timing can be varied enough to take full advantage of the 93 Octane I've been dumping into the car most of the time. The ECUs of forced induction cars are usually much more adaptive to varying knock conditions, and can step up the boost AND vary timing to take advantage of higher octane gas.
"Fuel type: Premium UNLEADED gasoline, Octane Rating 91 or higher for optimum engine performance. However, if such premium type cannot be obtained, you may temporarily use unleaded gasoline with an Octane Rating as low as 87."
It goes on to warn of knocking risks for lower octane, etc.....
With a normally aspirated engine, I don't think timing can be varied enough to take full advantage of the 93 Octane I've been dumping into the car most of the time. The ECUs of forced induction cars are usually much more adaptive to varying knock conditions, and can step up the boost AND vary timing to take advantage of higher octane gas.
I'm using 98 Octane Shell Optimax. I used to use BP, but they had a refinery issue over in Western Australia and you couldnt buy their 98 octane here for ages. Then i switched to Mobil 8000.
Then i saw a segment about octane ratings on the British TV show, Fifth Gear. So i switched to Shell. I did notice a difference in performance and economy.
Below is the link for a case study using 3 different cars and different brands of petrol and different octane ratings.
http://fifthgear.five.tv/jsp/5gmain.jsp?lnk=601&featureid=143
Well worth the read.
cheers
peter
Then i saw a segment about octane ratings on the British TV show, Fifth Gear. So i switched to Shell. I did notice a difference in performance and economy.
Below is the link for a case study using 3 different cars and different brands of petrol and different octane ratings.
http://fifthgear.five.tv/jsp/5gmain.jsp?lnk=601&featureid=143
Well worth the read.
cheers
peter
Stumpalama
Forum Junkie
There IS a difference in gas... even from your local gas stations. In states like Virginia there is no regulation on how the fuel octane is increased. So dicount gas stations like the pumps at a 7-11 or the like will increase the octane of their gas by adding alcohol. Which when applied to the fabulous r+m/2 calculation for octane results in a higher octane, but a hotter burning fuel with less energy per combustion and it scours the cylinders.
The big companies increase their octane ratings through the refinement process... thus (sometimes) the higher price.
Also, for some, like me when I had a little acura integra as my get around car, the discount gas doesn't matter too much. However, with larger more powerfull engines (and older, like my FJ40) I think quality is the way to go. So 89 from discount probably not as good as 87 from Exxon/mobile/texaco etc...
BTW, I use 89 in my LX450 and 87 in my FJ40.
The big companies increase their octane ratings through the refinement process... thus (sometimes) the higher price.
Also, for some, like me when I had a little acura integra as my get around car, the discount gas doesn't matter too much. However, with larger more powerfull engines (and older, like my FJ40) I think quality is the way to go. So 89 from discount probably not as good as 87 from Exxon/mobile/texaco etc...
BTW, I use 89 in my LX450 and 87 in my FJ40.
I recently towed my approx 3800# boat about 600 miles (half there, half back. I used 91 octane just because the owners manual said so. However, during this same time I actually put about 1000 miles on the vehicle, so I got to drive it some without towing using the 91 octane+ gasoline.
After I got back, I started using 87 again. I can't tell any difference performance wise or mileage wise using 87 or using 91-93.
After I got back, I started using 87 again. I can't tell any difference performance wise or mileage wise using 87 or using 91-93.
Plenty opinions here!
So I'll add mine: some manufacturers recommend premium in order to be able to advertise higher horsepower--the engine may only reach the peak hp with premium. I use midgrade in my '99 LC and if there's a difference in performance highway or city I ain't smart enough to detect it.
So I'll add mine: some manufacturers recommend premium in order to be able to advertise higher horsepower--the engine may only reach the peak hp with premium. I use midgrade in my '99 LC and if there's a difference in performance highway or city I ain't smart enough to detect it.
So if you drive 15K miles a year it will cost you $1.75 per week more to burn 91 octane over 87 octane if you get an average of 15 miles to a gallon. Thats 25 cents a day. That doesn't even account for any loss in mpg going from 91 to 87 octane. I just don't see myself worried about less then 25 cents a day when I drive a vehicle that listed for close to $70K.
