Speaking of DFCO, Lauren:

I have a DashHawk (more feature-filled version of a scanguage) and I have a menu set to purely fuel-information page.

I can see when I let off the gas, the fuel PSI remains at the lowest, the injection amount per cyl turns to zero, and the gallons-per-hour goes really low.

How do the injectors still have PSI!?

I'll take a video or record actual numbers, rather than going off the top of my head.

 

I can understand how people misspell my name when they only hear it spoken... but I'll never understand why people get it wrong on a forum.

Your fuel injection system should maintain a nearly constant fuel pressure at the fuel rail at all times. This is pressure, NOT flow. The fuel injectors pulse on and off to provide fuel to the engine. Keeping the pressure constant, the ECU can precisely control the timing of the injector pulses and know precisely how much fuel is being delivered at any given time. Cool, huh?

If you have DFCO and actually engage it, the GPH should drop to absolute zero because the fuel injectors have stopped pulsing altogether. (but you'll still have that constant fuel pressure there and ready for when the ECU decides the engine needs fuel)

It's exactly like closing the nozzle on the end of a water hose. When you close it, water stops flowing, but there's STILL water pressure in the hose behind the nozzle.

 

i dunno how much better the DFCO really is. i believe my car has it, and because of it, the engine braking is much more noticeable than putting it in neutral. so while no fuel is actually being used, the car doesn't "coast" as far due to the inertia of the car having to now spin the rotating mass of the engine..

 

You're right, with DCFO, the engine drag is going to be more than it would be if the engine were idling under its own power, and definitely more than coasting in neutral. But, to really know what works better, you have to monitor how it effects MPG over time.

Now, admittedly, I haven't done a lot of scientific testing on my own, but I know some people who have. Generally, they have found that you get better overall results by using DFCO under most circumstances. The exceptions are those really long hills where you can coast for half a mile at 60 mph in neutral without losing any speed... a situation that we don't have a lot of in Florida.

For city driving, I think DFCO is a great thing. Almost anytime you're "coasting" in city driving, you're already decelerating and you don't need to extend your coast. In fact, more often than not, I use the brakes to scrub some speed at the beginning of my coast so that I can coast slower, but for a longer period of time as I approach the stop light or traffic that I'm slowing for. If you time it just right, you can use almost no fuel from the time you spot a yellow light until it turns green simply by timing your coast so that you never fully stop for the light. (only works for quick lights and usually only if there are a few cars ahead of you and not a bunch of aggressive drivers behind you) Worst case, you do have to stop, but you've stretched your DFCO coast (not using fuel) for as long as possible so that you minimize the amount of time you sit at the light idling (using fuel).

It's tricky, but believe me, you can get huge improvements in fuel economy by learning to use and abuse DFCO. Even in city traffic... in fact, it seems like *especially* in city traffic. Couple it with gentle acceleration, and you're doing an exaggerated version of the "pulse and glide" technique.

All I know is that my Yaris is supposed to get something like 32 mpg in the city, and I can easily get 40 in the city and 44+ on the highway. (all with the AC on) I'd say the two major reasons for that are very conservative acceleration and extensive use of DFCO.

Should I be surprised to see the Deacon in the Green forum? I guess we're all trying to save a little money on gas these days. And the pursuit of higher fuel economy on the street is almost as addictive as the pursuit of lower times at the track, eh?

 

nah no suprise to see me here. i was actually contemplating an E85/E100 build....i know its off topic but generally speaking, the higher octane rating of the fuel, and how these flex fuel cars are built dont utilize the full potential of that higher octane rating...i would like to see if i could make a strictly E85 car double output and get better gas mileage. biggest problem i have is that nothing more than E10 is allowed to be sold in FL.

 

Hmmm... have you met Jeff(treekiller)?

 

no, not that i recall.

 

He's been playing with home-brew E-85 in his Sentra.

 

That's a big Negative. E85 is not only Legal in Florida but available at several locations, here is where I get mine. (all verified by me to be active public stations)

First Coast Biofuels
1170 U.S. Hwy. 90
Lake City, FL 32055
386-754-2616

Midway U-Gas
210 NW 79th Ave
Miami, FL 33126
305-269-7006

Turkey Lake Service Plaza - Florida's Turnpike
Mile Post 263
Ocoee, FL 34761
407-291-6329

Falls U-Gas
14395 S Dixie Hwy
Palmetto Bay, FL 33176
305-969-1494

Ft. Pierce Service Plaza – Florida’s Turnpike
Mile Post 145
Port St. Lucie, FL 34984
772-879-3870

Kangaroo Express
3500 N Monroe St.
Tallahassee, FL 32303
850-562-1159

Hallandale Beach U-Gas
990 W. Hallandale Beach Blvd.
Hallandale Beach, FL 33009
954-454-1744

West Hialeah U-Gas
7950 W 28th Avenue
Hialeah, FL 33018
305-818-0564

a 13:1 compression (Or boosted) E85 engine should be pretty close to it's low compression gasoline counterpart. with more power, only high cylinder pressures are going to offset the ~20% less chemical energy per gallon that pure ethanol has. it's a fact. although 93 has less then 87, but I won't get into that. to achieve your goal of getting better mileage you would have to reduce displacement so your power is the same post conversation as pre. then you could see a significant increase. (or with boost, you can run less boost to make the same power and higher compression = better economy)

This is why I'm looking for an 87 Chevy Turbo sprint. small displacement Port injected inter cooled turbo can make decent power and get great mileage on Ethanol.

I have gone full flex capability, with my highest $/Mile ratio being close to a 50/50 mix. it's still less then gasoline, but I need 90 octane so it saves me money.

 

no i know the energy isnt there compared to gasoline, the higher SCR was what i was going to use to gear the car more toward straight E85 use and not a flex fuel. but with more SCR, i can make more volumetric efficiency. start tweaking the DCR aswell and i can make more power too

and i cannot find any E85 station near me here in south pinellas.