ThatGuy1295

Air's getting in there. And with no fuel thats ok, but with some fuel it would have to be progressively more as the rpms went up to prevent backfiring. Right? Anyone?

Dirt Driver

That's why I use the vent when running the heater. I'm usually moving fast enough for air to be pushed through the cowl without help from the fan.

1.) And you're actually using more fuel by doing that instead of engine braking.

2.) Speaking from a purely theoretical standpoint, acceleration is the only time the extra weight requires more energy from fuel. That energy is converted into momentum, which is then available to keep the vehicle rolling until friction and drag deplete it. That energy is wasted as soon as the brakes are applied. In practice, I have noticed a negligible difference in highway economy with my truck whether the shell is off or on...and the shell does not reduce aero drag. City economy, however, does measurably improve when I ditch the shell and 50lbs of stuff I keep in it.

As has been mentioned later in this thread, the ECU cuts all fuel in an engine braking situation. The service manual, surprisingly, even lists the RPM ranges where the fuel is cut. The technique goes by multiple names, but I know it as "overrun fuel cut." Auto manufacturers have been using it as long as they have been using computerized EFI. I believe the 22RE ECU also monitors the brake light circuit for this reason, too. Why burn gas if you're trying to slow down, right?

The biggest gain in fuel economy I ever saw was ~3mpg from changing my driving habits. Beyond that, the only improvements I see are from mindfully driving only highway miles or getting a fluke tailwind.

What I would be really interested in seeing is a BSFC chart for a 22RE.

92dlxman

dirt driver: awesome
thatguy: the rogue hello wasnt directed toward you, it was toward our neutral or even better clutch-coasting friends. i realize the idle passage, but with the ecu being minded toward cleanliness, no fuel is better than trying for a neutral burn.

to our neutral-coasting friends: i see your point, brakes are much cheaper than motors and trannys. my first job i had to drive an old mechanic around sometimes. the work truck was the first truck i ever drove on pavement with 3 pedals, and put it in neutral before i ever hit the brakes. he conditioned me not to due to the lack of control, and because the output side of the tranny is still spinning anyway

dirtdriver: whats a bsfc chart?

Dirt Driver

Brake Specific Fuel Consumption is the mass of fuel that an engine uses to generate each horsepower for one hour. In metric terms, it would be measured as grams per kilowatt-hour. BSFC varies substantially over the rev and load range of an engine. Where the sweet spot is varies with design.

Honda and Subaru utility engines are provided with a single BSFC number since they are designed to run at a steady load and rpm.

92dlxman

ohhhhhh. basically shows at what rpm the motor is most efficient?

not necessarily going to be in the "peak" on a dyno chart i take it.

thats interesting

ThatGuy1295

Not to be stuck on this word but what causes backfiring then?
In a fuel injected engine that is, obviously a malfunction of some sorts, but is it because fuel isn't being cut at coasting like its supposed to be?

Dirt driver, thats interesting, I imagine that plays more of a role in engine design then actual power output these days.

4Crawler

iTrader: (3)

Short of engine-specific info, minimum BSFC is usually around the peak torque RPM:
- http://www.land-and-sea.com/dyno-tec...using_bsfc.htm
so 2800 or a little higher on the 22RE. This jives pretty close with what I have observed with different gearing. I found better MPGs with 5.29/33 gear/tire combo that let me run about 3000-3100 @ 65. With the same tires and 4.88 gears, I am turning closer to 2800 @ 65 and get lower MPG. I think part of the difference is due to having the engine work harder w/ 4.88s and also, that is is right at the peak torque RPM and any increase in grade or headwind and it drops the RPM below 2800 and you need to down shift. With the 5.29s, you have a few hundred RPMs to work with before the torque falls off so you downshift less.

Backfiring might be due to a mis-adjusted or missing dashpot on the throttle linkage:
- http://www.4crawler.com/4x4/CheapTri....shtml#Dashpot

That device slows the throttle closing to prevent back firing when you let off the gas pedal. The ECU takes a little time to cut off the fuel, so the dash pot gives it time to adjust.

Dirt Driver

1.) Partly. A BSFC chart considers both RPM and load.

2.) There again, BSFC is dependent on RPM and throttle opening. Maximum engine output does not necessarily exclude maximum efficiency.

1.) Backfiring through the exhaust is caused by a flammable accumulation of air and fuel that reaches ignition somehow. Something that can prevent overrun fuel cut is a maladjusted TPS sensor. If the ECU thinks you're applying any throttle at all, it won't cut fuel on deceleration.

On a side note, anyone ever use a wideband O2 sensor on an EFI car with the original ECU? It pegs full lean on decel, right? That's overrun fuel cut at work. I was paying attention today and noted when my truck stops the fuel and when it cuts back in. I let off the throttle and about a second later, after the dashpot bottoms out, I feel the engine braking increase a lot. If I don't do anything but keep slowing down, I can eventually feel the braking abruptly decrease; that's when the fuel comes back online.

2.) Output and fuel economy sell cars and, ironically, improving efficiency will improve output. As technology invariably advances, the gap between them gets smaller and smaller.

That reminded me about port wall-wetting. It's a relatively unavoidable phenomenon with conventional injection. Accumulated fuel on the port walls flashes to vapor much more readily under low manifold pressure, so there can be a rich spike when the throttle is chopped. The opposite is also true: the port has to be wetted again when the throttle is opened and manifold pressure increases. This is reason for carburetors having an accelerator pump and EFI having acceleration enrichment.

runs-on-4

iTrader: (1)

alright can anyone answer this.- in my 85 4runner with 4:10s and 34's 4inch lift i went from bothell to eugene 300 miles- ONE TANK in my new to me 88 p/u with 22re 33's 4:10s 4 inch lift portland to bothell about 150 it took me a about a little over 3/4 of a tank... oh and i had 233k on my 85 and the 88 has a new motor under 5000k is it not broken in completly resulting in poor fuel efficincy






















;

ThatGuy1295

Is one of those places down hill both ways?



Seriously though is their a tank size difference?

AMSevo8man

What size is the tank in our trucks? Well mine anyway... Its a 92 p/u. I read somewhere its a 13 gallon tank.. that seems pretty small... I use to get 22 miles to the gallon. The truck had a 22re 4:10's and a set a bald 31x10.50x15 tires. No I only get 18 miles to the gallon... same 22re engine and 4:10 but now with brand new 31 inch tires and I did a tune up. Why would it go down so much?

ThatGuy1295

How much do you put in @ fill up?

runs-on-4

iTrader: (1)

bothell washington to eugene oregon and i had a 17g tank in both trucks.

chrisorbics

My truck has gotten 17.95 mpg when I first got it. I have gotten 305 miles to a tank. I have to see what I am getting now. It know it does not seem to want to go 300 miles on one tank anymore. 1995 pickup 22re 5speed 192,000 miles 31x10.5-15 toyo all terains. 4.10 gears I believe.

I have noticed one thing in the time I have owned toyotas. The mpg is not hurt by reving it. I always thought it was better to lug it around but that is bad for the engine and fuel mileage. I am letting it rev more now.

My old truck which was a 1994 automatic with the same size tire 4.56 gears stock because it was automatic would get alittle less mpg in town but on the highway it would get 23mpg. There was no tachometer but I can tell you it was reving high. Plus I would bring it up to 80mph before I got to a big hill. Also that was loaded with camping gear and two bikes. With a fiberglass cap on it.

So I think that keeping the rpm around 3000 is good for mileage with a 22re. Obviously not with your foot in it. I haven't had my current truck on an all highway run yet to see the mpg.

chrisorbics

I was just thinking what would happen to the fuel mileage if I put on the stock 235 75-15 tires. My 1994 had 225 75-15s on it when I bought it off of the original owner. They didn't stay on for long. I think it would make a big difference in town since there is more stop and go. It would be so hard to go back to little tires. I would like to go bigger to 33s but I would want to regear it at that point and then you might as well make the jump to 35s.

AMSevo8man

I usually fill up when it gets to 1/4 tank and its about 10 gallons I think

HiredMind

I'd bet that it's not actually illegal. But it IS bad practice, which is why your friend failed the driving test. When you're coasting, there's not as much power to accessories - the important ones here being the power steering pump and the brake booster - as when you're not coasting. So it's not as easy to steer or brake while coasting, which could be a safety issue. It's also easier to kill the engine when you're closer to idle rpm, so you're in greater danger of losing all power. These are the reasons that driving authorities frown on it.

Dirt Driver

I'll take that bet for my state since you haven't listed yours anywhere.

http://dmv.ca.gov/pubs/vctop/lov/lovd11.htm

Vehicle Code Appendix B List of Violations Division 11 Rules of the Road:

Code 21710: coasting in neutral on a downgrade.

I'm assuming that fork's location "out in the Pacific" means Hawaii. I looked and looked on their government sites and couldn't find anything about their motor vehicle code.

sidebarr7

You could start experimenting with a HHO kit,,check out ebay

Dirt Driver

Do NOT buy an "HHO kit." You end up burning gasoline to run the engine to drive the alternator to power the electrolytic reaction. Every time energy changes form, some is lost from inefficiency. Ultimately it takes more energy to make the electrolysis reaction happen than you can get out of it by burning the gas produced, resulting in a net loss. That, and an electrolysis device small enough to fit in a car and not overwhelm the charging system won't produce enough gas to do anything.

Also, the name "HHO" and "Brown's gas" is joke in itself. Neither hydrogen nor oxygen are monoatomic gasses(existing as a single atom), so both actually occur as pairs of atoms in the form of regular old H2 and O2, not some miracle gas called HHO.

I've also seen the argument that H2/O2 increases burn efficiency in the engine and improves economy that way. Truth is that modern engines(and by "modern" I mean less than ~50 years old) don't have nearly enough room for improvement here to break even with the energy input, let alone see a gain.

Long story short, HHO kits are a scam that costs you more, not less. Just like putting acetone in your gas.