Does LX Really Have 2 More HP?
- Thread starter Evoking
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The same engine makes approximately 2 more HP when rated for premium fuel. (The official numbers are always suspect, and advertised horsepower numbers are often curiously round). I have been using regular for a while and there is zero difference in acceleration (identical 0-60) or calculated MPG. Always around 13.5 MPG.
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Yes, on account of octane. The LC is tuned for 87 octane. LX is tuned for 91 octane.
Given the same engine with all the same parameters and compression, octane allows for more timing or ignition advance. This allows for incrementally higher peak cylinder pressure after the cylinder reaches top dead center (TDC), making more torque per combustion event (and more hp, as hp is a function of tq and time). Over multiple combustion events, higher octane also allows for more timing overall as the higher octane fuel is more resistant to spontaneous ignition (knock) from increased heat.
Which is why octane really starts mattering on a highly loaded engine (i.e. towing, 35" tires, fully loaded, etc.). To run lower octane on an engine tuned for higher octane, especially in these use cases, is asking more wear and tear. It's because the base tune is for higher octane, and will cause nominal knock, for which the knock sensors will then detect and retard base timing. Note that knock will have occurred, for the ECU to then pull timing. It doesn't sense fuel octane pre-emptively.
Which is also why an engine tuned for lower octane, may not necessarily take advantage of higher octane, because of the lower base timing. It may even make less power on higher octane fuel, because octane itself is an ignition inhibitor. Higher octane fuel actually burns slower, but can be compressed more (i.e. timing advance), to release more power.
That said, the LX570 weighs considerably more (200+ lbs), so that extra hp and tq may not help it win a drag race.
Given the same engine with all the same parameters and compression, octane allows for more timing or ignition advance. This allows for incrementally higher peak cylinder pressure after the cylinder reaches top dead center (TDC), making more torque per combustion event (and more hp, as hp is a function of tq and time). Over multiple combustion events, higher octane also allows for more timing overall as the higher octane fuel is more resistant to spontaneous ignition (knock) from increased heat.
Which is why octane really starts mattering on a highly loaded engine (i.e. towing, 35" tires, fully loaded, etc.). To run lower octane on an engine tuned for higher octane, especially in these use cases, is asking more wear and tear. It's because the base tune is for higher octane, and will cause nominal knock, for which the knock sensors will then detect and retard base timing. Note that knock will have occurred, for the ECU to then pull timing. It doesn't sense fuel octane pre-emptively.
Which is also why an engine tuned for lower octane, may not necessarily take advantage of higher octane, because of the lower base timing. It may even make less power on higher octane fuel, because octane itself is an ignition inhibitor. Higher octane fuel actually burns slower, but can be compressed more (i.e. timing advance), to release more power.
That said, the LX570 weighs considerably more (200+ lbs), so that extra hp and tq may not help it win a drag race.
Good information.
Here is my question. Did they really design two different tunes for a mere 2 additional horsepower?
In any case, I have heard from someone who has gone over 100,000 miles so far on regular in a LX with no wear issues to speak of.
LX is a premium, USA only, and Lexus deemed this warrants the best/top fuel. it's all about perception.
Absolutely. To not, and require increased octane, is leaving power and efficiency on the table. And to some extent, emissions performance.
BTW, I tune turbo'd Lexus's and my own turbo Porsche.
Octane is a bigger variable than most understand, unless they're in the performance world. Then it's all about octane.
I have tunes on my own car for CA 91 piss grade fuel. Then 93 octane that the rest of the US has. The timing maps even between these two are distinctly different, with very measurable output differences of 20hp+. I also have maps for 100 and 108 octane. Which can see 100hp+ differences, as it's turbo and I can raise timing and dynamic compression (i.e. boost) to take advantage of more octane.
Lexus absolutely tuned for higher octane. It's a fundamental parameter in engine tuning, and a well understood science. It even says right in the manual that more knock may occur. Though OEM knock sensor are super sensitive, to protect from bad gas (or end users).
BTW, I tune turbo'd Lexus's and my own turbo Porsche.
Octane is a bigger variable than most understand, unless they're in the performance world. Then it's all about octane.
I have tunes on my own car for CA 91 piss grade fuel. Then 93 octane that the rest of the US has. The timing maps even between these two are distinctly different, with very measurable output differences of 20hp+. I also have maps for 100 and 108 octane. Which can see 100hp+ differences, as it's turbo and I can raise timing and dynamic compression (i.e. boost) to take advantage of more octane.
Lexus absolutely tuned for higher octane. It's a fundamental parameter in engine tuning, and a well understood science. It even says right in the manual that more knock may occur. Though OEM knock sensor are super sensitive, to protect from bad gas (or end users).
Markuson
SILVER Star
Man, I would hate to spend an extra $7 per tank for about 0.5% power increase...
I'm with @Willy beamin on this one. Purely a sales perception thing of "upscale" since luxury folk might not abide a premium brand that takes "regular" anything... They might have eeked out a tad more according to the math, but it wouldn't be enough to notice on the throttle.
I'm with @Willy beamin on this one. Purely a sales perception thing of "upscale" since luxury folk might not abide a premium brand that takes "regular" anything... They might have eeked out a tad more according to the math, but it wouldn't be enough to notice on the throttle.
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Thought I'd run a compare of part numbers between the 200 series LC and LX. I found the website toyodiy.com reports the same part number for the engine control unit for multiple years and production date cycles. Confirmed by checking online parts sites for a 2010 model year for both Toyota and Lexus. I suppose they could run different firmware. But I would expect different part numbers, or at least an additional suffix to the part number if that were the case.
It's closer to $11 extra per tank here. With an average amount of miles per year, that's about $4,000 more $$$ over 5 years.
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I've ran 87 since purchase as that's what the manual states. I am curious though, as my pig is pretty darn heavy if I would be better off running 91? Around here 87 is $2.19 and 91 is $2.43, so with a 20 gal fill up the difference would be $4.80 per tank.
@TeCKis300 what say you?
@TeCKis300 what say you?
Run the octane the car was designed for. If you own an LC, run 87. If you own and LX, run 91. Those will be the optimal fuels to run. Running 91 on an LC would be akin to throwing away money as the tune may very well not take advantage of it. Running 87 on an LX, would be asking for incrementally more wear, especially on a loaded rig.
Some performance cars, notably Porches, do have programming strategies to probe and take advantage of higher octanes when available. This is not typical for most cars though.
Some performance cars, notably Porches, do have programming strategies to probe and take advantage of higher octanes when available. This is not typical for most cars though.
Separate topic, but what's your thought about installing a unichip and having it tuned for 91?
yes LX have 2 more ponies, one name yoko and other name poko
Markuson
SILVER Star
I'm torn on this for several reasons.
1) For a sports car, chasing numbers either on track or dragstrip, I can see it being worth the effort. For a 3 ton truck, I personally don't see the point. It may show incremental power improvement on a dyno, or on track. Lexus got a conservative 2tq/2hp. Aftermarket, with more aggressive tuning and some other parts to increase flow, may see ~5-10hp. In real life use, I don't think there would be any appreciable difference for the relatively small power gain. It's a cost/benefit thing in my mind. Quite a bit of effort/cost, both initial and running costs, but not enough benefit.
2) The unichip certainly has the hardware capability to bump timing. But the challenge with these things in my mind is to find a tuner that's familiar with the hardware, and to a lesser degree, the platform. I've seen some horrendous installs and tunes, that most definitely compromise reliability. And would make questionable power at best.
3) Hacking (flashing) Toyota ECU's has been the holy grail for the aftermarket. Just about every other platform is now open and has flash tuners. Toyota's encryption has truly stood the test of time. As I understand it, the industry may be on the cusp of a solution (starting on the IS-F). After messing with tons of standalones and piggybacks, that invite their own issues and reliability concerns, my preference by far is stock ECU hardware with flash tuning. But we're not quite there on Toyota's yet.
FinallyGotOne!
SILVER Star
I raced an LC on US65 just last week. We flew down the highway side by side, neck and neck for a mile. I just couldn't get ahead of him. Then I remembered the secret switch only we LX owners know about and are sworn not to reveal to the LC guys. One push and those two extra horses were unleashed and off we went to a glorious win! Leggy Chicks and Champagne all around!
Markuson
SILVER Star
Thinkin maybe the LX drives the equivalent of 2HP faster...because the wallets of premium fuel buyers are just that much lighter. 
The TRD push start button upgrade adds at least 5 HP.
Great article from AAA, studying the use of different grade fuels on different cars, some requiring only regular, some recommending premium, and others requiring premium. Studied Ford Mustang GT, Jeep Renegade, Mazda Miata, Cadillac Escalade ESV, Audi A3 and Ford F150 XLT EcoBoost. They strapped the cars to dynamometers and ran various drive cycles with simulated grades of 0, 2, 4, and 6%.
http://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pdf
Takeaways:
1) The heavy vehicles saw the biggest mpg benefits.
2) The vehicle requiring premium (Audi A3) actually started knocking on lower grade fuel.
3) HP differences were mostly moderate, but F-150 gained the most at 11hp.
4) The comparable vehicle to ours, Escalade ESV V8 6.2L naturally aspirated recommending premium. Using regular, saw a 7.1% loss of mpg, 6hp reduction, and higher exhaust gas temps.
Note that the LX570 requires premium rather than just recommends premium on the Escalade.
Food for thought for owners of the LX, wanting to run regular. Premium may never yield cost benefits from the added hp and mpg. But to run regular will very likely cause more wear and tear on the motor.
http://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pdf
Takeaways:
1) The heavy vehicles saw the biggest mpg benefits.
2) The vehicle requiring premium (Audi A3) actually started knocking on lower grade fuel.
3) HP differences were mostly moderate, but F-150 gained the most at 11hp.
4) The comparable vehicle to ours, Escalade ESV V8 6.2L naturally aspirated recommending premium. Using regular, saw a 7.1% loss of mpg, 6hp reduction, and higher exhaust gas temps.
Note that the LX570 requires premium rather than just recommends premium on the Escalade.
Food for thought for owners of the LX, wanting to run regular. Premium may never yield cost benefits from the added hp and mpg. But to run regular will very likely cause more wear and tear on the motor.
