OK, I titled it this way because, realizing there are SO many factors involved, there can't be a good single answer.
Here's the general theory:
A "stock" 2.3L motor at stock HP will, in general, give good mileage because of its heritage as a four cylinder, and the way that the head, CAM, and exhaust are configured. I also understand that later, turbocharged 2.3L motors have reasonable fuel consumption in regular driving, because again, they are four cylinders.
Here's the question(s):
In considering an engine change, can someone please help me understand why and/or why not each of the following statements would be TRUE or FALSE?
NOTE: Each of these scenarios considers standard driving as "commuting" or "pleasure driving". Each also considers good mileage/reasonable fuel consumption as being in the realm of 20 mpg.
1) Putting a V8 in a Pinto will still achieve reasonable mileage, because the amount of power and torque generated by the motor easily moves the mass of the lightweight vehicle
TRUE OR FALSE? WHY?
2) A mildly modified 4 cylinder (slightly bigger cam, head work and carbueration) will get reasonable gas mileage in regular driving
TRUE OR FALSE? WHY?
3) A heavily modified 4 cylinder (heavy cam, aftermarket head, and carbueration) will get reasonable gas mileage in regular driving
TRUE OR FALSE? WHY?
Sorry if these seem like ridiculous questions (sounds like a physics class exercise, it's the engineer in me), the aim of the question(s) is to determine what would be "profitable" in terms of building a car that gets decent mileage, but still "gets on it" when asked to.
Besides, picking your brains is fun - I love the wealth of knowledge here ;D
Chris
#3: Depending on the mod.s you will have a tough time driving it on the 'street'.
Without getting into 'absolutes', think of an internal combustion engine as an air-pump. The more air that goes through it, the more fuel it burns; it needs a presice air/fuel mixture.
Larger engines or ones with more cylinders tend to be lower 'rev.ing' and have lower idle speeds. This might make you think that there is a equalization point somewhere.
Keep in mind that OVERALL GEARING (including tire size) is very important too.
How does all of this come together for fuel economy? Keep your foot out of it!
Bill
Got 1977 Pinto with a 302, it gets the same gas mileage as my 5.7 liter Expedition.
The Expedition gets 13 miles to the gallon (combination city/Highway)
It is big and has allot of drag, it also is engineered to get as good mileage as is possible with a pig of a vehicle. Throw in fuel injection, computer control, etc. (Modern Design)
My 77 Pinto has a 302, it has a carburetor, it is set up to drink gas and zoop air, as much as is possible in a 2300 Pound car, this also makes it fun yet expensive to drive. It too gets 13 miles to the gallon with a whole lot less weight and drag, but no efficiency in this motor and definitely no computer to adjust fuel economy. Just a big engine in a little car, 20 MPG is a dream.
i dont know much about effects of mods on fuel consumption. to be honest, if i was modding it, i never really cared about fuel consumption. as far as a heavily modded 4 banger with lots of compression and a big bumpstick....i dont know how friendly it would be for "regular driving" if you mean it as a daily driver. my last mustang, 91 lx 5.0 5 speed with 3.73 and some performance goodies got about 21-23 mpg on the freeway. id imagine it would be better in a lighter car due to the fact it takes less to move it. as far as an efi turbo, youll get great milage out of it AS LONG as you stay out of boost....which is hard. they have a boost refrenced fuel pressure regulator to increase fuel pressure under boost. i think turboford has the calculator to show what different pressures do to different sized injectors. obviously, more air....more fuel.
just some of my .02.
bob
sorry, that fuel milage was freeway. thats about 95% of my driving.
bob
OK, Modifying for performance and milage????
I have received real good HP results using the stock 2.0 carb.
"sorry to the 2.3 crowd I can only speak about the 2.0 but most should work no-mater what engine"
Anyway.. If the stock carb is used and it is the restrictive in the engine equation...
Pulling air/fuel through the venturi would be the same A/F ratio IF installed on a 2.0 or a 5.0.
The 5.0 would only rev to a certain point and then power would fall off.
If you take a car with a 390 C.I. engine with a 2V and install a quadrajet carb, small primary's and BIG secondaries. The 390 will be a totally different engine if you put your foot to the floor.... :fastcar:
Anyway IF you had a 2.0 with the stock carb and raised the C.R. to say 10.5 to 1 but left everything else alone the engine would make more power and be better on fuel
More C.R. = better efficiency.
Now some MAY argue???
The 10.5 to 1 is a variable.
Ask yourself....
Do you really think that the engine is really getting fully filled at idle?
the 10.5 is a SWEPT VOLUME not true C.R.
Y do you think poorly maintained and poorly tuned engines PING at WOT???
Raising the C.R. will make better low end torq over the RPM curve.
And that is where you do most of your crusing on the freeway.
More C.R. = better throttle response
From Pintony
a big motor in a little car is a nce thought but only IF you can keep your foot out of it. want to learn about driving for mileage? get a vacuum guage and try to drive at the speed limit with the HIGHEST VACUUM reading-the HIGHEST GEAR-the LOWEST RPM at all times. (be prepared to have other drivers on the road to become intensly hostile)
in my experience an efficiently driven, slightly modified small CID motor will out mileage the larger motor car.
source: (long since retired) '71 4spd, 2.0, 3:73 rear gear(speedo corrected & accurate), turbo. 24-25 mpg at freeway speeds over many several hundred mile trips.
street mileage? couldn't tell 'ya. gas was cheap & I was too busy with my foot to the floor on weekend cruise nights :laugh:
Well.... My Pinto made three trips from Southern California to Salt Lake City and back and I averaged 26.45 mpg and easily passed the smog sniffer test (1986 Mustang Lx specs) without a catalytic converter.
When I first got the car it ran the quarter mile in 21 seconds flat at 64 mph and I never got out of second gear, got 13mpg and would barely pass smog without any modifications. When I was finished I was running 18.25 seconds in the quarter at 76 mph. Doing some math guestimation on my quarter mile mph I estimate I was making about 94 hp after all of the modifications, that's with a short block with somewhere in the range of 300k miles on it.
I added a Hooker headder with all of the smog fittings (I don't think Hooker offers these anymore), a 2 1/2" exhaust system with an early 1990's Flowmaster two chamber muffler, which is louder inside the car than it is on the outside.
I rejetted the stock 5200 carb up to (if I can remember right) 72 primary jet and 74 secondary jet and switched from the hot water choke to an electric choke and readjusted the vacuum choke pull off to pull right at engine start. I also modified the EGR spacer plate from a two hole unit, to an open plenum ( I lost some bottom end responsiveness, but at the 1000 ft mark in the quarter I can really feel the car pull harder.)
I then had the distributor recurved for 10 degrees initial and 34 degrees total timing at 3000 rpm and left the vacuum advance setting stock. For street use I would keep the setting at 8 degrees initial timing (the stock starter motor was having a hard time starting the car at 10 degrees initial)
Installed the biggest Iskendarian cam with a smooth idle (I forget which grind it was but I think it had .420" lift).
I also installed a 190 degree thermostat and a 14lb radiator cap (be careful with the radiator cap, I popped the top off of my stock radiator tank with this cap and had to have the radiator strapped to keep the pressure up.)
Believe it or not, I kept the EGR valve fully functional because the car would ping at the first hint without it, but when the EGR was working, I could run 87 octane gas without a problem.
For the transmission, I added a B&M shift kit and the torque converter only stalls at 1000 rpm.
The differential has 3.40 gears and the rear tires are 235-60X14's and the front tires were 185-60X13's. I later switched to 205-60X13 front tires and lost two tenths in the quarter and my gas mileage went into the 25mpg range.
What I plan to do now is to add a stock Ranger roller cam, new pistons and rings, bearings etc., an Esslinger windage tray, and install an 8" differential with 4.62:1 gears and a Gear Vendor overdrive for the C-4, and I found a high stall, high altitude torque converter .75" pilot (I have no idea of where it stalls at but I had one before and when I had the transmission rebuilt they installed the 1000rpm converter which took a full second off of my quarter mile times). I will be running 235-60x15 tires in the rear and 195-70x13 tires in the front, with 2" dropped spindles (which I hope fit!!!).
I hope some of this info is helpful.