When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Practical comparison 87 e0 vs 91 E0 in 2015 Lexus IS350 RWD f sport
I am gonna use this thread to post results of a practical comparison between those two fuels and the effects on performance they had on my 2015 IS350 RWD f sport (with blue f sport air filter). Everything else is stock on the car. I am also gonna reset the ECU ever time I fuel the car.
Pretty useless unless a robot is driving the car the exact same way every time, under the same exact conditions. Too much variable with the human factor and placebo effect. The gas *you* want to win will win and you'll press the accelerator pedal as such, even if not on purpose.
but sure I guess if you want. Go for it. Tell us what you find.
Pretty useless unless a robot is driving the car the exact same way every time, under the same exact conditions. Too much variable with the human factor and placebo effect. The gas *you* want to win will win and you'll press the accelerator pedal as such, even if not on purpose.
but sure I guess if you want. Go for it. Tell us what you find.
I think if he did the test long enough, the results could be validated.
Years ago I used to keep every gas receipt from my cars, and calculate the mpg for them. They were all over the place, of course, even using the exact same pump 98% of the time, but after a while you see patterns emerge. If he did that, and then switched only the fuel, he could make valid assumptions.
But I agree that just a few tanks, no matter how technical, isn't really going to prove anything.
Absolutely agree. I am not making any claims on the repeatability of the results
And even a robot will not let you control env. parameters like air pressure and temperature, road conditions, traffic patterns and traffic lights patterns.
Nonetheless, I will attempt to test two cases - low RPM high gear WOT pull and high RPM low gear WOT pull. Those are slightly easier to repeat, because you just have to stomp on the pedal as quickly as possible.
my primary interest is in how ecu will retard timing for 87. Mpg results are less of interest, especially because I am not sure I wanna run 87 for more than 1-2 full tanks.
Okay, so here is the data.
Conditions were about the same for both sets. It was dry and about -2 to 3C outside temperature.
I did two types of pulls - high RPM pulls (3rd-4th gear from 65-74 mph to 85, from 0 to 80mph, WOT) and low RPM pulls (from 70-ish mph in 8th gear, WOT).
There were roughly about 20-24 pulls for each type of fuel (10-12 for low RPM and the same for high RPM).
I simply clumped together multiple pulls on the graphs, so I could look at all the data for the same fuel + type of test (low rpm or high rpm).
Also, I added averages, which are shown as thick marks to the right of each plot.
Low RPM data sets (left - 87, right - 93)
It is quite clear that the average timing for 87 was 10 deg, while for 93 it was 15 deg. RPMs (shown in blue *100) are about the same on average. Green value of 69 indicates that the throttle pedal is being pressed to the floor, but without activating that accelerator button at the end of the pedal travel. Pressing through that button would give 72 or so).
------------------------------------
High RPM data sets (left - 87, right - 93).
The average timing for 87 was 22 deg, while for 93 it was 24.5 deg.
I am actually wondering if I need to retest high RPM pulls for 93 with traction control being OFF, as to not cut the timing, when the ECU senses the wheel spin. That might explain those really low "negative" peak values on high RPM 93 fuel chart. I don't think it would matter for the low RPM tests, though.
I thought it was just odd that 93 octane has the timing cut, while demonstrating that the timing on average is higher than what 87 showed, while producing more power. My guess is that it does produce more power and enough of it to trigger TC. Matt Farah, Savagegeese and Everyday driver did mention that TC sucks life out of the car. So, it looks like it is a good theory for why timing gets cut on that 93 highrev graph. It is time to test it.
You getting any info on pre-det and knock? Pushing the engine hard with low octane (anti-knock) would show the timing pulled back like that. I haven’t bothered to look around and see if you can pull data from the Lexus knock sensors. If the engineers say use 91+ I use 91+. Having seen what knock and pre-det does to engines.
You getting any info on pre-det and knock? Pushing the engine hard with low octane (anti-knock) would show the timing pulled back like that. I haven’t bothered to look around and see if you can pull data from the Lexus knock sensors. If the engineers say use 91+ I use 91+. Having seen what knock and pre-det does to engines.
I can't imagine that Toyota would even allow knock in this day and age. I guess it's possible, but would be extremely difficult to make happen/cause an issue.
You getting any info on pre-det and knock? Pushing the engine hard with low octane (anti-knock) would show the timing pulled back like that. I haven’t bothered to look around and see if you can pull data from the Lexus knock sensors. If the engineers say use 91+ I use 91+. Having seen what knock and pre-det does to engines.
I dont, because my OBD2 scanner does not read that parameter. But I thought that timing will get affected by the ECU, when it detects knocking, so I might as well just use that.
Modern ECU will not let the engine knock for long. Repeated signals from one of the knocking sensors will be enough for the ecu to cut the timing sufficiently to stop the knocking. Besides, in the official manual, it is said that occasional knocking sounds should be of no concern. In other words, they know that the Ecu will keep the motor safe, and they also know that it is impossible to prevent the knocking in 100% of the cases without compromising performance.
But if you stop it immediately right after it starts, the engine will be fine long term. It is not the knocking that destroys the engine, but rather HOW LONG you have that condition in relation to how long you run the engine.
I am not planning on running it on 87 anyway. It was just an experiment (allowed by the manual, btw).
I dont, because my OBD2 scanner does not read that parameter. But I thought that timing will get affected by the ECU, when it detects knocking, so I might as well just use that.
Modern ECU will not let the engine knock for long. Repeated signals from one of the knocking sensors will be enough for the ecu to cut the timing sufficiently to stop the knocking. Besides, in the official manual, it is said that occasional knocking sounds should be of no concern. In other words, they know that the Ecu will keep the motor safe, and they also know that it is impossible to prevent the knocking in 100% of the cases without compromising performance.
But if you stop it immediately right after it starts, the engine will be fine long term. It is not the knocking that destroys the engine, but rather HOW LONG you have that condition in relation to how long you run the engine.
Haha true. Though with enough boost pressure you really only need knock for a short period.
these engines have decently high compression, so that window is a lot smaller compared to older engines with mild to medium compression. I do trust Toyota’s engineers enough to not worry. Just curious to see if you had the data. My scanner doesn’t show it either.
"A minimum 87 octane fuel is recommend for most vehicles produced since 1984. Older cars with carburetors could operate with lower octane fuel at higher elevations. Regardless of legality fuel with an octane rating of less than 87 is generally not offered for sale in most states. However 85 and 86 octane gasoline can still commonly be found in several rocky mountain states."
I am actually wondering if I need to retest high RPM pulls for 93 with traction control being OFF, as to not cut the timing, when the ECU senses the wheel spin. That might explain those really low "negative" peak values on high RPM 93 fuel chart. I don't think it would matter for the low RPM tests, though.
Nice work on collecting data to show the difference in ignition timing when using 87 octane vice 93 octane. Definitely turn traction control off to eliminate the potential for the engine to cut back on power when tire slip is detected. With the cold weather, breaking traction will likely be the norm and not the exception.
Originally Posted by Darqhelmet
You getting any info on pre-det and knock? Pushing the engine hard with low octane (anti-knock) would show the timing pulled back like that. I haven’t bothered to look around and see if you can pull data from the Lexus knock sensors. If the engineers say use 91+ I use 91+. Having seen what knock and pre-det does to engines.
You are able to pull data from the knock sensors (Knock Correction Learn Value [KCLV] and Knock Feedback Value [KFV]) but AFAIK it can only be done from one of two methods:
1) Techstream
2) The OBD Fusion app with the Toyota/Lexus Enhanced Diagnostics add-ons.
Tracking these values will give you additional information on how the ECU is responding to the lower octane fuel (For KCLV, a value of 20+ means ignition timing advance is functioning at its peak).