Fuel Effecient V8

[Lextreme II]

I noticed GM are producing V8 engines that are very fuel effecient during cruising. Only 4 cylinders are working during cruising and all 8 cylinders kicks in during hard acceleration. I would think a bypass fuel system (perhaps the inlet air too) along with ignition cut off for the none function cylinders. The computer play a major coordinating these events. I wonder if this is possible for the 1uzfe engine with stand alone engine.

 

[Toysrme]

Ahhhh. been there, done that on my 3vz-fe v6 with my smt6.
I used a set of relays to cut off the front bank fuel injectors, tied the two o2 sensors together & corrected the fuel trim on my smt6 to keep the ECU happy & wound up having to cut the spark to the front bank too.

Im sure someone could do infinately better than I could. To me, it didn't really do much more than make the engine very, very unresponcive. Didn't like cruising on the highway without 75%+ throttle. Doesn't really do much for me. Like anyhting it's a balance. The idea is that one bank of cylinders pulling through a larger throttle opening are more effecient even after losses. The problem is without cam trickery, you're inccuring pumping losses.
That, most car engine guys can pick-up on as a first thoguht.

What they normally don't consider is ignition. You're still gunna suck fuel into the cylinders if you can't keep the intake valves closed on the dead cylinders. If you're sucking fuel, even if it's super lean, you're gunna burn it. It may not on a cold engine, but it sure will when it hits that hot combustion chamber!







That was my experiance with it. I don't want to sound like an expert, or anything. Heck, I'm bearly able to remember my grandfather cussing his 4-6-8 left and right. But unlike alot of people that talk about it, I did actually try it for awhile. It's good to drive down the driveway I guess if you can keep the ECU out of limp mode! (Where it may give you like 5mpg!)

 

[Toysrme]

Your idea of a dual intake would solve most of that.
Just use one of the throttlebody's that has the second plate behind it to close the cylinders when you turn it off.

Give it a try man. A v8 is gunna have a lot easier time than a v6.

 

[Peewee]

Last time I looked this saved 1L/100km, (less than a mile per gallon)

Simple enough to do though.
A switch to turn one ignitor off, and at the same time turn off the 2 corresponding injector drivers.

 

[Lextreme II]

I would like to see how the car would idle. Must be pretty crazy. I guess the Ignition and injector driver can be connected to the TPS. TPS would activate the system.

 

[Toysrme]

Do it, pull an ignition coil wire.
Trust me it'll idle, but the ECU is gunna freak somewhat. You may have to give it a pull of gas to give it a chance to catch up & work it's idle control magic.

*edit* addition


Hope it's an even fire engine too...

 

[Lextreme II]

Why do you think dual intake will work. What about single intake like what we have now.

 

[Toysrme]

It seems easier in my mind to close off the airflow to an entire bank of cylinders with a dual intake. As opposed to figuring out a way to close it off on a single intake.
You could add a flap to a single intake, just seems easier to me on a dual.

 

[Zuffen]

How would you reduce "pumping losses" without disabling the valve gear.

OHC's make it hard to disable the valve train.

There must be plenty of situations where 8 cylinders are not required.

 

[Toysrme]

You wouldn't disable pumping losses without disabling the valvetrain.
It's actually far easier to do it in OHC. vtec, just have one set of cam profiles blank! THat's what honda's done.

 

[Pro]

GMs engine has some serious problems inherent in it's design.

1) lifters designed to collapse on shut down cylinders. a computer controlling the oil pressure? WTF?
2) you still have to fire the shut down cylinders once in a while to maintain even heat distribution - also the car would run very lumpy even at cruise.
3) others i can;t think of right now.

DOD is a deadpan way to save fuel. it's a typical bandaid solution of a major car manufacturer so they don't have to re-engineer too much.

perhaps if they made their cars lighter and smarter - instead of 20km's weight of wiring harness and 100kg of sound deadener, and appropriate gearing, they might save more fuel that this stupid sh1te.

wasn;t this stuff tried on trucks a few years ago? didn;t they fail dismally due to reliability issues?

 

[Toysrme]

Or maybe if they would go back to using v6's with a turbo gnX, typhoon, or cyclone.
Think about what the modern Japanese v6's could do with a t3/t4 turbo LoL! High 20's for average mpg, and blat out around 350-400whp.


I digress, back to reality! LoL!



I don't know pro. I thought the last company to do it was GM with the v8-6-4 long ago. Everyone's doing it now. GM, Chrystler. While I don't care about them, Honda's doing it using their vtec cam lobe setup. If Honda does it... Atleast somebody can manage it without killing their engines! haha!(Variable Cylinder Management on the honda)

I gotta tell ya... I like Honda's way of doing it far better. Take a technology so proven it's been run into the ground (vtec), make some minor changes. Then call it mechanically done!






You know we could do the same thing... Except for the "i" in vvt-i doesn't stand for infinately! hahaha

 

[Pro]

the cam change in VTEC and VVTi is just oil pressure moving the lobe centres.

in other words, really quite reliable and effective because of it's simplicity.

if anyone can do DOD properly, then it won't involve collapsable lifters and 100% computer controlled oil pressure.

then i see it at a plausible solution.

then again, you could always buy a smaller car with a smaller engine and get the same performance due to the same hp/weight ratio and better fuel economy.

 

[stevechumo]

....then again, you could always buy a smaller car with a smaller engine and get the same performance due to the same hp/weight ratio and better fuel economy.

:cool2: Umh! I like the idea. This somewhat sounds like my past. A 4 cylinders Honda with a huge turbo system. At cruising, the gas is very efficient. For acceleration, it has a heart of a monster inside a tiny body. Those fast Hondas are not rare at any drag track. I didn't really go crazy on dragging but my fastest Acura made 305 whp with only 2/3 of the weight of my current SC400. I could boost it up but I decided to stop it there. Beside the gas thing and quick handling, other factors can't compare.

 

[GSMnow]

I have not seen how the new GM DOD system works, the old V8-6-4 system moved the rocker arms sideways off of the valves. Mechanical nightmare.
To me, the smallest pumping losses would probably result from keeping the valves partially open so the air can flow without compressing or creating a vacuum. If you are still squeasing all the air, I don't see it saving anything, you just burn twice the fuel in the remaining cylinders.

On a side note, In my turbo 22RE 4 banger, I cracked 2 pistons at a race event and after pulling the injector plugs and spark plugs I drove it home on 2 cylinders. It ran pretty good, and I even pushed it up into boost a couple times to pass on the highway. It sounded like a Harley, but it pulled decent and got me home 60 miles away from where it broke. I doubt the mileage was any record though. Full valve operation and the open spark plug holes made for wild noises under the hood. Now that yuo mention it, I would not be suprized if a little fuel mixture found it's way into those cylinders too. I pulled the coil off of the TEC so there were no sparks flying under the hood, but the open plug holes were aimed very close to my exhaust manifold and turbo. Hmmm.

Gary M.

 

[stevechumo]

For fuel efficiency, I'm recalled of the coal engine trucks that were used a long time ago. Those coal engine trucks look just similar like the U-haul trucks. I guess they operate like the old-time trains. One disadvantage is they drop the burning coals on the street that can damage or injure the people driving behind them. I don't know how their engines operate so can anyone can shed a light on them?

 

[Zuffen]

When you say coal powered I guess you mean steam powered trucks where coal is used to heat the boiler.

Basically the truck has a steam engine (like a locomotive of the 40's) and it is fed steam from a boiler installed in the truck. Steam doesn't require a change speed transmission as it developes maximum torque at astandstill.

The old coal burners were very fuel inefficient and left black clouds of smoke behind them. As well as in some cases the hot ashes to refer to.

Stanley and White were big manufacturers of steam vehicles. They died out because the self starter was invented and petrol powered cars were easier to start and drove off immediately.

Modern steam vehicles use flash boilers and fancy cocktails of liguid in the boilers. They can go from cold to driving in 30 seconds or less.

In the 1960/70's Bill Lear had steam buses running in LA but they were too costly, complex and insufficiently developed to catch on. Bill Lear also invented the Lear Jet. He was no dummy.

 

[Toysrme]

I think this would work better.
Throw down some 15:1 CR pistons, lean burn with however much water injection it takes to run it for an economy mode.

For a power mode, have a vvt, or vtec system kick the intake cam into big overlap (Atkinson cycle) to decompress the engine & make it safer for the turbo to come online & give the engine atleast some kind of balls.




Sounds like a fun project for my civic lol