GX470 Octane - Just some research is all-Talk among yourselves. (1 Viewer)

[hammerheadfistpunch]

I know the debate rages continually on the need for premium fuel for the GX470 and while I don't intend to answer the question I do want to shed some light on some findings of mine.

So people wonder why the 2UZ-FE in the GX470 should recommend premium (91) fuel where the UZJ100, 1st and 2nd gen US Tundra's and the J120 4Runner do not (87). I honestly can't answer that question but I did find a clue.

All the specs listed here come from Toyota's published product information specs and user manuals and not 3rd party. The only exception to note would be that the LX470 was pulled form the Lexus of Canada archives...I don't know if there is a difference but I would bet there isn't.

2007 Land Cruiser - 265 hp @5400 rpm / 310 lbs-ft @3400 rpm 87 octane recommended
2007 LX470 (dual VVTi) - 268 hp @5400 rpm / 328 lbs-ft @3400 rpm 91 octane recommended
2009 4Runner (V8 limited)-260 hp @5400 rpm / 306 lbs-ft @3400 rpm 87 octane recommended
2009 GX470 (dual VVTi) - 263 hp @5400 rpm / 323 lbs-ft @3400 rpm 91 octane recommended
2009 Tundra (2UZ-FE) - 276 hp @5400 rpm / 313 lbs-ft @3400 rpm 87 octane recommended

Now I should point out that different packaging requirements will result in slight differences in HP based on the nature of exhaust flow and other variables, however it is pretty clear (to me at least) that the Lexus version of the 2UZ-FE had a different tune than the Toyota versions and the net benefit is an increase in midrange torque. The difference being 18 lbs-ft for the J100 platform, and 17 lbs-ft for the J120 platform. Peak power is, more or less, a wash.

I have to speculate that the marketing team for Lexus required that its "premium" offerings beat out the more plebeian Toyota offerings, at least on paper, to given well-heeled buyers a reason to fork up the extra money. I'm not sure how well the pitch of "3 more hp!" brought the idea home but there it is.

I also can't answer the question if running regular will harm a Lexus Tuned 2UZ-FE, only to say that the only real damage that could occur would be:

Knock related damage
premature wear of emissions equipment.

As for the first, if you don't hear knock...its not happening and the knock sensors are doing their job, probably bringing your mighty Lexus down to lowly Toyota power levels.

For the second, this is debated but the general consensus is - no data either way.

Its worth noting that all the engines run the same 10:1 compression ratio, so mechanically they are the same.

A third consideration would be fuel economy - Would running more expensive fuel at a higher state of tune improve thermal efficiency? And if so to what degree? That might be worth taking on this summer just for S/G.

As for me and my GX? I run 87 unless I'm towing, then its 91. Do I notice a difference? Not even a little.

Something I find interesting is that the Tundra somehow sees nearly 10 hp more than the best SUV number...at the same rpm...but has a lower torque value than anything else that requires 87. I have to wonder where that extra power comes from.

 

[half k cruiser]

Wait, your supposed to run 91 in these things ? I didn't see anything to that affect on the dash. Been running 87 since we bought it in April. The only UZ I ever did premium on was the GS400 but it specifically called for it.

 

[hammerheadfistpunch]

Wait, your supposed to run 91 in these things ? I didn't see anything to that affect on the dash. Been running 87 since we bought it in April. The only UZ I ever did premium on was the GS400 but it specifically called for it.

On the Dual VVTi motors, its premium only. Not sure when the switch happened. Whenever they went to 260 ish hp. over 230ish

 

[JLee]

On the Dual VVTi motors, its premium only. Not sure when the switch happened. Whenever they went to 260 ish hp. over 230ish

2005.

I can't tell a difference.

 

[hammerheadfistpunch]

2005.

I can't tell a difference.

Adjusted mpg? Bigger tires?

 

[half k cruiser]

On the Dual VVTi motors, its premium only. Not sure when the switch happened. Whenever they went to 260 ish hp. over 230ish

Copy that, non VVT-I here .

 

[NMBruce]

After I got my 2006 GX, I believe the manual suggest 91 or maybe it was a 05 I looked at.
I ran 91 for 6 months and then I switch to 85 for 6 months and saw a very little change in MPG or power change.

with summer here and prices good, maybe I will try going back to 91 for a couple months and see what happens

 

[JLee]

Adjusted mpg? Bigger tires?

Yep.

 

[Dharma Dude]

I thought that if your engine doesn't knock with regular fuel then it's always safe to use regular. Am I mis-informed?

 

[hammerheadfistpunch]

I thought that if your engine doesn't knock with regular fuel then it's always safe to use regular. Am I mis-informed?

If your engine is tuned for premium then you'll always be on a less than optimal map and your mileage and emissions can suffer even without pinging. I think it's not a big deal with our engine but as a rule of thumb is the recommended for best results.

 

[kwkshift]

My '08 pings on 87. I could easily hear it inside. So, I've switched to 91 and all is fine.

 

[lndshark]

HP and even torque ratings aren't necessarily related to ECU mapping. Keep in mind, SAE rated power in production engines is measured at the drive wheels, not the flywheel as in the past. This introduces a few variables including tire/wheel size, exhaust length, exhaust manifold configuration (manaverter versus tubular header), etc. This can explain the vagaries between SUV/truck output measurements, especially with Tundras. When I worked at Toyota there was well over one hundred configurations available (which meant typically 7-10 applications to EPA for fuel econonomy and emaissions certifications). As for octane requirements, yes, some of this has to do with marketing. And if one UZ engine makes 205hp on 87 and another makes 210 on 92 RON, you can bet the sales literature will list it. Why should a GX be inferior to a Sequoia or 4Runner?

Real world emissions will also not be effected by octane levels on pump gas. Most emissions test are conducted at idle or a short-duration light load on a chassis dynamometer.

As for spark knock, it's a bit of a false statement to say that if you cannot hear it, it's not happening. Part-throttle knock is detectable by ear (and less detrimental to the engine). When you can't hear harmful knock is at WOT, under a load, when wind, road and exhaust noise mask it. When engines are durability tested in a lab on an engine dyno, they are outfitted with a myriad of instruments to detect knock. There is even a series of sensitive microphones in some engine test cells that technicians will monitor via amplifiers and headphones to note any unusual noises, including spark knock.

 

[JLee]

HP and even torque ratings aren't necessarily related to ECU mapping. Keep in mind, SAE rated power in production engines is measured at the drive wheels, not the flywheel as in the past. This introduces a few variables including tire/wheel size, exhaust length, exhaust manifold configuration (manaverter versus tubular header), etc. This can explain the vagaries between SUV/truck output measurements, especially with Tundras. When I worked at Toyota there was well over one hundred configurations available (which meant typically 7-10 applications to EPA for fuel econonomy and emaissions certifications). As for octane requirements, yes, some of this has to do with marketing. And if one UZ engine makes 205hp on 87 and another makes 210 on 92 RON, you can bet the sales literature will list it. Why should a GX be inferior to a Sequoia or 4Runner?

Real world emissions will also not be effected by octane levels on pump gas. Most emissions test are conducted at idle or a short-duration light load on a chassis dynamometer.

As for spark knock, it's a bit of a false statement to say that if you cannot hear it, it's not happening. Part-throttle knock is detectable by ear (and less detrimental to the engine). When you can't hear harmful knock is at WOT, under a load, when wind, road and exhaust noise mask it. When engines are durability tested in a lab on an engine dyno, they are outfitted with a myriad of instruments to detect knock. There is even a series of sensitive microphones in some engine test cells that technicians will monitor via amplifiers and headphones to note any unusual noises, including spark knock.

The bolded portion is untrue. SAE net power is the power of the engine with all accessories mounted, but it is not measured at the drive wheels.

Note the 460hp Corvette with a dyno result of 402whp.

 

[lndshark]

Well, I wasn't referring to Corvettes. I was trying to be Toyota specific as it pertains to the thread. Toyota rated, advertised power ratings in consumer literature is RWHP. When specific to J1349/J2723, yes, net HP is measured minus a driveline.

 

[JLee]

Well, I wasn't referring to Corvettes. I was trying to be Toyota specific as it pertains to the thread. Toyota rated, advertised power ratings in consumer literature is RWHP. When specific to J1349/J2723, yes, net HP is measured minus a driveline.

That is not SAE, then. I also don't believe that to be true; do you have a source?

https://www.toyota.com/content/ebrochure/2017/86_ebrochure.pdf

86 is now more powerful than ever, with its high-tech Boxer engine delivering up to an impressive 205 horsepower and 156 lb.-ft. of torque in manual transmission versions. And with a 7200 rpm redline, the thrills build with the revs. A close-ratio 6-speed transmission comes standard, giving you quickness off the line and the power you want in the corners. For the driving purist, the standard manual transmission gives short, precise throws for a driving experience like no other. And for those who prefer two pedals, the available 6-speed Electronically Controlled automatic Transmission with intelligence (ECT-i) features race car-inspired paddle shifters mounted on the steering wheel. So no matter your preferred driving style, you’re always in control.

2017 86 dyno

 

[lndshark]

You are correct and thank you for pointing that out.

 

[hammerheadfistpunch]

HP and even torque ratings aren't necessarily related to ECU mapping. Keep in mind, SAE rated power in production engines is measured at the drive wheels, not the flywheel as in the past. This introduces a few variables including tire/wheel size, exhaust length, exhaust manifold configuration (manaverter versus tubular header), etc. This can explain the vagaries between SUV/truck output measurements, especially with Tundras. When I worked at Toyota there was well over one hundred configurations available (which meant typically 7-10 applications to EPA for fuel econonomy and emaissions certifications). As for octane requirements, yes, some of this has to do with marketing. And if one UZ engine makes 205hp on 87 and another makes 210 on 92 RON, you can bet the sales literature will list it. Why should a GX be inferior to a Sequoia or 4Runner?

Real world emissions will also not be effected by octane levels on pump gas. Most emissions test are conducted at idle or a short-duration light load on a chassis dynamometer.

As for spark knock, it's a bit of a false statement to say that if you cannot hear it, it's not happening. Part-throttle knock is detectable by ear (and less detrimental to the engine). When you can't hear harmful knock is at WOT, under a load, when wind, road and exhaust noise mask it. When engines are durability tested in a lab on an engine dyno, they are outfitted with a myriad of instruments to detect knock. There is even a series of sensitive microphones in some engine test cells that technicians will monitor via amplifiers and headphones to note any unusual noises, including spark knock.

While I realize that different configurations mean slightly different power ratings (as I point out in my post) I do think its clear that the tune is different in the Lexus engines based on the power figures. In the case of the UZJ100 its the same exact car but with very different rated power and AKI requirement. without detailed information on the specific maps, I have to use what I can find and work my model backwards. Its also not a secret that the Lexus version of a Toyota engine shows a pattern of more power but on premium fuel. unless the engines are mechanically different the only reasonable assumption is the map and I don't have any reason to suspect they are different mechanically.

While I defer to your engineering background on knock, its not outside the realm of feasible for a person who is paying attention to hear knock at any engine/vehicle speed. I know I could when I was driving a supercharged 454. Though its unfair to say that it will always be easily detectable.

As for drive wheel power, I think we can safely say that these figures are NOT rwhp, but SAE net with accessories attached. There is just no way Toyota made the 4.7 produce rwhp in the high 200's when hooked up to the A750F. My accelerometer based dyno tool puts the actual whp of my gx in the high 100's low 200's. (still better than my 80 which tops out about 110 estimated whp)

 

[NMBruce]

I am thinking that the only real way to know what is what is to take a 4Runner with the V8 and test it with 87 and then with 91. After that take a GX470 and repeat the process.

I would guess that the 3-5hp could be from the octane difference, not from the tuning of the vehicle.

 

[hammerheadfistpunch]

I am thinking that the only real way to know what is what is to take a 4Runner with the V8 and test it with 87 and then with 91. After that take a GX470 and repeat the process.

I would guess that the 3-5hp could be from the octane difference, not from the tuning of the vehicle.

You won't get 1 more hp using premium on an engine tuned for regular. You might actually lose a little on account of it being more resistant to ignition.

Premium fuel offers no benefit without an engine meant for it.

 

[NMBruce]

You won't get 1 more hp using premium on an engine tuned for regular. You might actually lose a little on account of it being more resistant to ignition.

Premium fuel offers no benefit without an engine meant for it.

So your saying that the computer will not make changes?

In 1984-86, a Mustang SVO had a little switch that would change timing if you couldn't find premium fuel and a noticeable difference in power. Back in the mid 80's, engine could be made to adapt to fuel grades, so I gotta believe that modern engine and computer system could make some changes.