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'[TECH]: What is involved in making a selectablecyl'
|Back around 1980, Ford Cleveland Engine plant that made the 302 C.I. D.
(5.0) 1955- 1996 (now makes the 2.5L 4 OHC V-6), as a demonstration what
could be done with the cast iron V-8, to try and sell to management what
the plant could do at very little extra setup costs, made several inline
4 cylinders. Some of the issues were:
Firing order of the cylinders so you got even power pulses. To
change one needs a custom camshaft, it's not just moving sparkplug and
injector wires around.
Balance of crankshaft and other moving components.
Airflow in intake manifold. These are designed for the pulses of air to
each cylinder melt together for smooth flow through the intake system.
In the case of a carburetter, it's design may not allow the low air
velocity of half the cylinders. For injection, their probably is a mass
airflow sensor that would have similar issues,and the computer might not
know how to handle that situation and generate an error signal (OBDII code)
Long term valve stem wear since some of the lubrication comes from the fuel.
There are plenty of small engines around that could be fitted to
vehicles, but that may not result in better mileage. My experience has
been a big engine, driven reasonably will get at least and probably
better mileage with optimal gearing. Our 1996 Ford Bronco weighs 5300
lbs, 5.8L cast iron V-8, 4 speed overdrive automatic tranny, torque
convertor lockout, cruises at 65 mph at 1500 RPM on very little
throttle, easily 18 MPG. It goes up and down hills staying in overdrive
with the converter locked. Best mileage was Atlanta to Cleveland was
24.2 MPG with many miles at 35 - 45 mph parkway, and easy interstate.
This is with the 4WD front hubs unlocked. With them locked mileage drops
at least 3 MPG (17%). And if you don't mind a little gas guzzling, 0 -
60 mph is 9 seconds for that heavy iron!
I would look in other directions than cutting cylinders off. The vehicle
has air and mechanical drag, thinner lubricants, some low friction tires
are available. A properly tuned engine, which today means sensors
(oxygen, temperature, mass flow, etc.) that are feeding the computer
data in proper calibration. In the air drag, many little things will add
up, and don't have good input on that, other than check out the
homebuilt aircraft area, in particular the Longeze. There are some real
gurus in that arena. Check after market equipment, if it's a small
vehicle the"Tuner" area, larger try Summit Racing. Not all the equipment
in those areas is for the drags.
Alan B. Pearce
> What is involved in making a internal combustion ( gasoline or
> diesel ) engine with '"n" cylinders operate on "n" divided by two
> cylinders ? Does one just turn off the injectors ? Are there other
> requirements ? Does one vary the cylinder usage to reduce noise and
> wear ? Can a DIY meddler attempt such a project on a 1997 8 cylinder
> gasoline fueled SUV ? What are the fuel saving ramifications ?
> Ideally I would like to drive around on "4" cylinders and switch to
> "8" cylinders to pull a trailer.
I believe the BMW 750 can do this. It is a V12 engine with a separate ECU
for each bank, and if one ECU dies the engine will 'get you home'. I don't
know if the 735 V8 engine has the same facility.
'[TECH]: What is involved in making a selectablecyl'
|There are at least 6 variations of fuel injection for gasoline engines
1: One injector at the throttle body ( where the throttle butterfly is
located) Early Ford Escorts (1981 >>)had this. The Injector sprays
continually at varying rates.
2: Mechanical fuel injection, I don't know about this, but I think they
have a mechanical injection pump, like some (many newer are electronic
injected) diesels with a nozzle before each intake valve. Don't know
whether these sprayed continuously. Not really sure about -Early after
market (Hilborn), Mercedes (300SL), Corvettes?? Had this. In the mid
1950's the electronis as we know them today were non existent. :)
3: EFI (Electronic fuel injection) - Each injector was located before an
intake valve, sprayed continuously at varying rates. Became common in
1980's. My 1989 Ford Bronco with 5.8L Windsor (Ontario, Canada) engine
4: SEFI (Sequential Electronic fuel injection) - Each injector located
before an intake valve, Sprayed intermittently, timed to spray only
when intake valve open at varying rates. Became common in early mid
1990's. My 1996 Ford Bronco with 5.8L Windsor (Ontario, Canada) engine
5: I have seen recently some manufacturers (BMW, Mercedes ??)
advertising direct fuel injection. I am assuming this is like a diesel
engine where the injector sprays directly into the combustion chamber.
If that is the case, possibly spark plugs are not required.
6: A constant pressure pump with a throttle body that regulates fuel
pressure (flow) with throttle opening and vacuum. Fuel is distributed to
all nozzles located before each intake valve. Fuel flows to all nozzles
all the time. Most injected aircraft engines use this method. The move
to more efficient injection method has been very slow due to reliability
(an engine failure is not pleasant) and certification issues.
Sean Breheny wrote:
Yea, Dodge, does fancy stuff, but misses the easy stuff. Nearly every
Dodge pickup I drive behind, I can see the front axle U-joints turning.
while they drive down the highway. That's a lot of drag. With the front
hubs locked on our 4WD vehicles, the mileage was down more than 25%
compared to hubs and transfer case in neutral.
Herbert Graf wrote:
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