I began wondering awhile ago if I could run my 4Runner on E85, mostly for cost savings. Recently, the high fuel prices in California had me researching this further. Here's my research; I'm going through this "showing my work" to make sure everyone here can follow along and tell me where I was an idiot.

Background:
E85, in the US, is 51-85% ethanol, and the remainder is gasoline. Usually pump gas is 10% ethanol. The main pros to E85 are... cost. It's cheaper per gallon. It also has a higher octane but burns cooler than gasoline. This is why a lot of forced-induction tuned cars make their best power with E85– it lets them really crank up the boost without pre-detonation and reduces cylinder temperatures at the same time. The downside? It is about 30% less energy dense than gasoline.

The energy density of a fuel is basically how much energy you can extract from it. Uranium is incredibly energy dense, while coal and wood... not so much.

E85, being less energy dense than gasoline, takes more of the same liquid to do equal work. This is why fuel economy goes down in FlexFuel vehicles running E85. Less boom in the boom juice. How do you overcome this? Well, those FlexFuel vehicles tend to have bigger fuel injectors and fuel pumps to keep up with the demand of the engine. Too bad the 5VZ-FE isn't a FlexFuel engine... or is it?
Starting out
As part of the supporting mods for my supercharger, 330cc Supra injectors were used in place of the stock ones along with an uprated fuel pump. This helps to keep up with the extra fuel demands of the extra air being introduced into the engine. As part of keeping an eye on the health of my 4Runner, and because I didn't wholly trust the word of the previous owner, I installed a combination AFR/boost gauge and an UltraGauge on the A-pillar. The AFR gauge was to make sure I wasn't running lean and the boost gauge was to see how much excitement I was having. I was checking to see what the fuel trims were for my truck to see if the previous owner had actually installed the bigger injectors like he claimed. What I found was the fuel trims hovered around -20%. (I have a picture of this, but I can't find it right now.)



FUEL INJECTORS
A note on fuel injectors and fuel trims. The fuel injectors are timed to open during the intake cycle. How much fuel to inject depends on the air that's coming in to the engine. More air, more fuel. And if that air is at sea level, you'll have more air coming in than if you were driving in the mountains at 10,000'. For best emissions and power, the ECU measures the air coming in (The MAF does this) and the air going out (the O2 sensor does this). Some fancy math later, and the computer knows if the engine is running rich or lean. If it's running rich, there's too much fuel, so the fuel trims get pulled back. If it's running lean, there's too much air, and fuel trims get increased.

Due to the natural variations of fuel, the ECU has to do this even if the temperature and altitude don't change. Some fuel is going to have slightly less energy than other tanks, and the fuel injectors will have to compensate by opening for some percentage longer or some percentage shorter. I was really surprised to see readings of -20 for my long-term fuel trim. That's basically saying the injectors are being pulled back to spray 20% less fuel. Stock injectors are 245cc, so the Supra injectors are capable of flowing about 35% more fuel. Injectors most accurate in a +/- 20% range around their ideal flow rates, so seeing my fuel trims so low was a bit surprising. Even under heavy acceleration, making 5.5psi, but not so hard the ECU went open-loop, the fuel trims "only" came up to zero. That... actually makes sense. Under high fuel demand, with the supercharger, it needed about 20% more fuel.
AN IDEA SPARKS
If I floored it and let the ECU go into open-loop during a pull all the way to redline, my AFRs stayed very rich, around 8-11:1. This means the wideband O2 sensor in the exhaust was calculating I had (at the "leanest" moments) 11 parts air to 1 part fuel. Which is good, even if the ECU is completely ignoring that detail and just dumping fuel into the cylinders as much and as fast as the injectors can flow. Both short and long term fuel trims stop being updated when the ECU goes open-loop, presumably because there's no point to it. They're just going to be maxed out, instead of being finely tuned to maintain the ideal AFR. The ideal ratio is 14.7:1, and this is what the ECU is constantly trying to achieve. Well... except technically it is chasing a Lambda of 1.000, but for gasoline this ratio is equates to 14.7:1. My aftermarket gauge is calibrated for gasoline, but the ECU reads the lambda.

Ah-ha, I mused. I have headroom for a less-energy-dense fuel. Something like... E85.
VEHICLE INFO
I'm going to take a quick break here to note some technicalities. My truck is a MY2000 CA-emissions-spec'd 4Runner with the 5VZ-FE. Most 4Runners sold don't have wideband O2 sensors. I believe they were just the CA-spec ones which had the wideband sensor upstream of the catalytic converters (yes, there are two), and a second "normal" narrowband O2 sensor downstream of the cats. The downstream sensor only gives a high/low signal; it tells the ECU there's too much or too little fuel, but not by how much. It is a check which lets the ECU knows if the cats are failing. I don't even know what model years had this configuration in California! I'm also assuming that the ECU actually makes use of this information to better-tune the fuel trims, instead of treating it like a narrowband with a simple high/low signal. But this gave me an opportunity. I had the factory wideband sensor, an aftermarket sensor, faster-flowing fuel pump, and the bigger fuel injectors to go with it all. I could see the lambda value off the ECU and compare it to the aftermarket AFR value to make sure both were reading accurately.

I also had a ton of raw, unbridled courage of someone who'd read a lot of articles on the internet. I started with just a couple gallons of E85 in a tank of 91. Honestly? No change.
STARTING TESTING
I did this for a few tanks, adding between two and three gallons of E85. I noticed no drivability issues, no loss in power, and honestly not even a change in fuel trims. MPGs suffered slightly, but within what I would consider a margin of error for this sort of test. (I really like the intake roar through the snorkel. Sue me.) The AFR and Lambda values stayed completely reasonable.

Warily, I filled up with 91, burned off half the tank (the easy part) and filled up with a half-tank of E85. Here, I was able to see a change in fuel trims. They came up a bit. Instead of hovering around -20, the long term fuel trim hovered around 0. Interestingly, I noticed that the long-term fuel trim climbed rapidly at idle, but would stay lower when driving.
MORE #TRUCKFACTS
My truck is a 5-speed, so at idle, the flywheel is the only thing connected to the engine and smoothing out each detonation within the cylinders. More ethanol means less energy, so it needs more fuel to keep the flywheel spinning and have a smooth idle. Once in gear, the wheels are connected to the engine and help to keep the engine spinning. Basically, more fuel is needed to idle and less fuel is needed once driving. This makes sense... for a stick. I don't know how an auto would handle the situation. I would expect fuel demand to rise because the torque converter needs to keep being spun, but I don't know how much more— or less— fuel would be needed. Try this at your own risk if you've got an auto.
E85!
After a few tanks of this half-and-half mixture, I grew braver. I started filling up about 3/4 of the tank with E85. Fuel trims increased again, but the ECU compensated. I could see "hunting" at idle, with the AFRs bouncing between rich and lean, especially after filling up. My suspicion is this was due to the varying ethanol content. Sometimes there would be more ethanol, and more fuel would be needed. Other times more gasoline would be delivered and fuel trims would need to be pulled back to keep from running rich. Either way, the ECU learned pretty quickly, and I never saw AFRs so lean as to be worried (16:1 for split-second, and only at idle). Usually it bounced around between 13-15 until the ECU "learned" the mixture for my tank, and then I was off to the races.

Not really the races. It's a 22-year-old SUV that weighs like 5,000 pounds. I'm not racing anything.

Anyway.



This is what an ethanol sensor in FlexFuel vehicles does... it helps the ECU learn in advance what is coming through the pipes, so it doesn't go too lean. It lets the ECU compensate ahead of time, instead of after combustion. This is really important for vehicles that see high boost; running lean for a moment when you're making 20 psi at 6500 RPM is going to end very poorly. For a just-barely-boosted engine like the ones in our trucks? A brief bit of lean running is to be expected occasionally.

Finally, I gathered my nerves. I ran an already 3/4 E85 mixture until the fuel light came on, and refilled with all E85. It was my cheapest fill-up in months, costing half as much as gasoline. Guess what?

The truck ran fine. There was the initial AFR hunting that I'd come to expect, and then... that's it. I could see fuel trims came up to the 20% mark, though. I kept my eye on it, but it didn't cause any issues I could see. That's still within spec, albeit barely. All was well, or so I thought. I wanted to see if I still would get pinging with the high-gear low-RPM situation. I shifted into 5th gear while going about 30MPH and floored it.
UNLEASH THE DEMON WITHIN
Guys? E85 made so much power that my RPMs shot nearly to redline. My head didn't snap back, though. I was making so much power my clutch started slipping. Sure, you might think it's because after 213,000 miles and 22 years and plenty of 4WD tracks that the clutch was on its last legs. But just between you and me? You're probably right.

Remember, I didn't do this to chase power. I did this to chase $$$ savings and lower engine temps. You can make heaps of power on E85... but that is not my goal.

Okay, so the pinging test will have to wait until I get around to a new clutch. Donations accepted. But there's another important test... a high-boost pull to redline. That's where fuel delivery is key, because there's the most air coming in and the shortest window of time to inject fuel.

It's kind of boring, if I'm honest. While making 5.5-6psi of boost, with my foot to the floor in 2nd gear, lambda readings stayed in the 0.8xx range and away from 0.9xxx. Indicated AFRs were 11-12:1, instead of the 8:1 with gasoline. The ECU was in open-loop, so it didn't bother updating fuel trims, but the more important things were that the engine wasn't running lean.

All good, right? Well... kind of. After the fourth full tank of E85, the long-term fuel trims began to hover around +30% at idle. This was enough to set a P0171 code, or "Bank 1 Lean". This is a case of the codes not telling you the entire story (I'm pretty sure). If you didn't have a wideband O2 gauge, it would appear that, yes, the engine was running lean and that's why fuel trims were so high. But for our trucks, it doesn't seem like a P0170 "Fuel Trim Malfunction (Bank 1)" code gets set, which is what I'd expect to see. The ECU even reports the lambda value as being in that 1.0xx range, and the aftermarket sensor reported 14.7:1 (remember, this is equivalent to a lambda of 1.000 with gasoline... and it doesn't know there's ethanol in there... so 14.7:1 is good) which seems like the lambda isn't being used to determine what code is set. And, if all you have is a high/low O2 sensor, it might make sense? Kinda?



I drove a bit, being careful, before adding about two gallons of 91. The fuel trim came down a bit, but still 20-25% at idle. As soon as I'm not idling, it falls to between 5-18 depending on if I'm accelerating, going up hill, etc. The UltraGauge has been reporting a pending P0171 code for a bit now, but the check engine light hasn't come on yet.
CONCLUSION
I think the sweet spot for around-town driving is 3/4 E85 and 1/4 gasoline. I haven't risked using 87 octane; I don't know enough about how the 100+ octane of E85 will mix with the lower octane gasoline. If you know, please tell me! But it's probably not worth the extra $1.50, especially after saving so much running on E85. If I was going on a longer trip, I wouldn't hesitate to use a full tank of E85. A long freeway drive will keep out of the high-consumption low-rpm idle range and have fuel trims low enough that the computer— and my wallet— stays happy.

Once I actually got to a trail, though, I'd probably fill up with regular gasoline. Enough trail driving happens at lower RPMs that I wouldn't want to push my luck with E85 fuel trims setting a code while out and about.

A few other notes.
"Don't you know ethanol will destroy your fuel system‽‽"
The EPA decided that E15 is safe to use in vehicles newer than 2001, in June 2011. 3G4Rs straddle this line; however, the fuel systems of a 1996 and a 2002 T4R are similar enough I would expect them to be fine.

Older vehicles might see their rubber lines degrade... but then again, those are older rubber lines. They may not be certified to handle ethanol. But for us? The hard lines shouldn't care. The fuel pump has to support enough flow, but for our era vehicles also has to resist ethanol anyway. The injectors have to tolerate ethanol as well.

"Ethanol fuel leaves residue and crap behind in my lawn mower!"
Yeah, get an electric lawnmower, problem solved. :-P But seriously... a well-sealed fuel system (like any OBD-II vehicle) isn't going to let enough air in to cause problems if you drive often enough. Just... don't let your truck sit for few weeks? Whenever I used to go on long trips, I'd fill up with fresh gas and add fuel stabilizer, then run the engine to make sure the stabilized fuel made it all the way through to the injectors. The only thing I'd do differently now, if I went on a long trip, would be to make sure to run a couple full tanks of gasoline through first to clear as much ethanol out as possible before adding a stabilizer.
"Your MPG must be terrible!"
Yes... it's a lifted SUV. Even before E85, my fuel economy was crap. Now, it's still crap, but it's cheaper. I have seen about a 15% drop in my MPGs. Totally expected. When E85 is 50% the cost of E10, I'll take the 15% hit to MPG. The math works out. Plus, bonus, there's never a wait to use the E85 pumps. I've probably saved weeks of my life already not sitting and waiting for a Costco pump to be open.

"What about cold starting?"
Ah, a good question. E85 in the US varies per season, just like regular gasoline. I've noticed on cold mornings a very slight hesitancy to start compared to gasoline... but nothing I'd worry about. That said, I live in San Diego. I don't know how the engine would handle starting after a night of below-freezing temperatures. Now that we're seeing the changeover to winter gas, E85 will go from being mostly ethanol to about 50/50 to make starting easier for FlexFuel vehicles. I suspect that will actually make things run better, since I was running more ethanol than that in the summer.
"What are your engine temps?"
Fantastic. 185˚F on the dot. Sometimes I see 190˚. Even on 100˚F days, since I started to use more E85, I haven't seen engine temps over 200˚. I still have the original radiator in my truck (I did flush it when I bought it to clean the old green crap out) and because it's a manual I'm planning on running that original radiator until it cracks. Then, we'll see. Maybe an aluminium one. Maybe another OEM. But anyway, I'll keep an eye out on both engine water temperature and cold starting throughout the winter and into the summer again.
"You're going to ruin your truck!"
Maybe? I dunno.
"What are you doing next?"
I've heard that E85 clears out the crap in a fuel system, so I bought a replacement fuel filter. My plan is to swap the filter (I did this once before, when I bought the truck) after a few tanks of E85 and then cut open the old filter to see what it looked like.
I'm also going to pull the spark plugs and stick a boroscope in to look at what the cylinder walls and piston heads look like. I'll also be able to see what the plugs look like at that time. I'm not expecting any surprises, because the sensors are reporting everything is good, but it'll be nice to know.
"How much power did you make/lose?"
None and none. The ECU is stock. It just thinks I'm a dummy who keeps putting fuel in that doesn't match spec and needs more of it. The computer isn't wrong. If I wanted to, I could find a tuner who could help better match the ECU to the fuel and probably squeeze out some extra power as well as eliminate some of the acceleration dead zones where the ECU hesitates to go open-loop. I haven't lost any power, though. The ECU adds fuel to compensate for that. And I don't think I'm making more power, either.
"What's your ignition advance?"
Good question. I've seen it hit 40˚ which is... a lot. But it usually is around 20˚ BTDC, according to the ECU. As far as I know, this is not modifiable without a tuner, and the ECU mostly manages this by advancing timing as far as it can, and retarding it if there's any knocking. 100+ octane helps prevent knocks, and ethanol helps to carry away the extra heat from the ignition advance. Technically, being able to have a greater advance should mean more chance at power, but again, I'm not chasing that. If I got an extra few horsepower, awesome. I could use it, especially because I want to add a winch, and that SOB is going to add more weight. What's the saying? Simplify and add lightness? I should try that sometime, just maybe not with a built 4WD.

You write good. That was enjoyable to read for both the prose and the content. Fun stuff!

I think you have a vacuum leak.


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Also, get a South Bend Clutch: Clutches for Toyota, PICK-UP (INCLUDING 4-RUNNER), 3.4L, 1996-2002 | South Bend Clutch | We Motivate The Shiftless

Thank you! That's my goal.

What makes you say that? I drove for years without a CEL or noticing any other symptoms of a vacuum leak. Aside from external stuff (bumpers, skid plates, etc.) I haven't touched anything engine-related for awhile. When I did my last major tune-up I also didn't notice any leaks. (I want to swap all the vac lines out for fancy silicone ones, but... effort.)

Any reason why? What's the advantage in the different types they offer (HD vs Daily vs Endurance)? I haven't really started the research into replacing the clutch yet. So long as I'm not in too high of a gear and don't floor it, the clutch doesn't slip. But it is definitely on its way out. I can literally taste it. Burning clutch... what a unique scent.

Speaking of scent. I've noticed with the back window down, the exhaust gas that gets sucked back into the vehicle isn't nearly as awful smelling when burning E85 as opposed to regular gasoline. Not that I make a regular habit of sniffing the exhaust, whenever the back window is down the front windows are too.

Your LTFT is way high. That supercharger at idle shouldn’t effect the airflow that much that it’s at 20. Especially with the big injectors you have over stock.

Extra air bypassing the MAF will cause it.

What is your MAF reading warmed up at an idle of 750rpm?

Just my opinion…..others with superchargers could chime in on their idle LTFT and their injector size and if their ECU is stock, same year and emissions category etc…..




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I ran E85 for many years on my turbo Volvo wagon, which was running about 20 - 24 psi of boost. Very ping resistant, to the point where it was possible to advance tuning pst peak and start hurting power, still without detonation.

I first started doing it way back when, 2007-ish time frame, using a standalone Megasquirt injection computer. It didn't have flex fuel capability, but I (mis)used the nitrous functionality - added an external switch to flip between my dedicated gasoline and E85 spark/fuel/boost tables. Advance the timing some, 25 - 30% more fuel, higher boost on E85. I'd just run it really low on one fuel, fill up with the other, run it a few seconds and flip the switch. And the E85 tune was always elusive, I was doing a lot of ongoing tuning.

Eventually I put an MS3X ecu on it, which supported flex fuel, and added a GM ethanol sensor on the return line. Where I discovered why the E85 tune was always a work in progress - the % of ethanol in a given E85 pump was pretty variable. Anywhere from 30% up to the advertised 85%. The flex fuel setup worked a lot better, interpolating between the two sets of tables based on the %, with a configurable curve.

Basically a little ethanol in the gas goes a long way, it's not a smooth curve between E10 and 85% E85, at least in terms of the effective octane rating. The good E85 acts like 110 octane fuel more or less, it's like race gas (other than the 'lo calorie' aspect).

I've since put a turbo 5.3 LS V8 in it, running lower boost (7-8 psi), and I'm running pump premium in it for now.

Gotcha, I'm following you. I'm not totally convinced, but I'll configure a page on the UltraGauge to put up STFT, LTFT, Lambda, and MAF reading. After doing some engine work one time I didn't quite tighten one of the hose clamps enough on the intake (about 1/8th to 1/4 turn too loose) and that instantly set a CEL. The ECU can tell, at least in some situations, when unmetered air is getting into the system, but then again I'm going out of spec on fuel so . Thanks for the advice, next time I take a drive I'll report back on what I find.

Maybe I should just buy a kit and replace all the hoses anyway...

Very Nice!

Will be adding a GM Flexfuel sensor to my 1uz turbo build so I can run E85 at-will, but don't have to run it as a mandate if I'm unable to find it.

E85 is some amazing stuff.

I started running E85 about a year ago, also supercharged. I found with the stock 4Runner injectors running E85 would max the positive fuel trim and set the lean code (P0171). On the other hand running the Supra injectors with regular gasoline would max out the negative trim and set P0172.

Prior to going full standalone for fuel with megasquirt, I found the best alternative seemed to be right around a 50/50 mix of E85 and gasoline to keep the fuel trim happy with Supra injectors.

You can mix lower octane gasoline with E85 and still have greater than 95 octane blend. The calculator linked below is easy to check what octane rating you'll arrive at based on your blend ratios. I typically would use a 50/50 blend of 85 octane gasoline (high altitude) and E85 for a resultant 95 octane mixture.

E85 CALCULATOR - ETHANOL MIX

Great process and thank you for documenting so much of your work! I am actually very surprised that it won't idle without throwing a code from maxing the fuel trims. Some OBD-II readers can show values above 30% so it may be beyond the maximum allowed amount. I wonder if the fuel at idle is not only controlled by the MAF but also the IAC? The throttle plate is normally only about 11% open at idle and once you start to accelerate, even slowly, it's higher around 17% and will need more fuel flowing. If you had a piggyback controller you could easily bump up fuel between 500-1000 RPM by 15-20% and it would be an easy solution.

If you do decide to replace hoses, also look at the EVAP hoses. The ethanol fumes cause these old hoses to crack faster than the rubber supply and return lines in the engine. The fuel line hoses are very stout and will probably be fine.

Well, you mention the burnt clutch. I roasted my stock clutch pretty early wheeling my truck pretty hard. I may not be supercharged, but I got a "Tuesday Motor". My truck is quicker than any other normally aspirated 3rd Gen 4Runner I've ever been around or driven. I have a few performance mods, which help quite a bit, and I drive like a loon most of the time. ;)

The South Bend Clutches hold more torque and take a lot more abuse than the stock unit. I have what they called the "Rally" clutch, which is now the Stage II Daily. This clutch has the same pedal feel as the stock clutch while dealing with more HP and Torque. If I was supercharged, I'd go with the Stage II Daily for sure. Contact them and see what they recommend for your vehicle and usage.

This.... Is awesome. Job well done, sir.

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I see on strait gas you’re LTFT was reported at -20 with the big injectors.

Was that at idle or driving around?

4 tanks later you started hitting 30 at idle. What was it at idle before you started coding for it
too lean at idle?

Our intake system was not designed for boost. Maybe it’s as simple as you blew a cracked hose off your intake manifold under boost.

MAF wise a good sealed up MAF reading at a 700rpm idle will be .500 lbs per minute for an NA engine. You can convert that to grams if your scanner is in metric.

For E85 you should be shooting for around 10:1 AF. When you mention lamda is it for gas or e85?

Just my ideas…..it’s how my brain works.


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Lambda is the direct WBO2 sensor reading, it's the measure of how much oxygen remains in the exhaust. That is interpreted by a gauge to show an AFR value, but that interpretation involves some assumptions about the fuel, and generally speaking most gauges (unless you deliberately reprogram them) will be expecting you to have burned gasoline.

But the number, even though technically not the correct AFR for ethanol or E85, is still useful for tuning. 14.7 is still stochiometric if you're burning gas or E85. There's no real need to convert it to an actual E85 AFR.

That said, E85 acts a little differently, and using a regular setup AFR gauge or not, you might want to do some different tuning under boost. Either way, really, it's more resistant to detonation, so you might not need to run as ruch under a given level of boost. And alternatively/contradictory, it will keep adding more power a bit richer than gasoline will, so if you're really wanting max power richen it up more than you would with gas.