why do 3400's get better mpg than 3100's?

[1QUICKHATCH]

The 3400 has more torque and torque is what gets you moving, the horsepower keeps you moving.

[robertisaar]

The 3400 has more torque and torque is what gets you moving, the horsepower keeps you moving.

which is why they were geared lower, just like the 3.8 and the SC3.8. gave it lower gears, and even though it made more power, they got better fuel economy.

the same concept could be applied to a neon that turns over 3200RPM at 70MPH. but they don't make enough torque to "comfortably" accelerate to that speed with any taller of a gear even though more fuel economy could be pulled out of it.

[Superdave]

it's all dependent on the gearing, weight, drag coefficient of the car, altitude, weather, tune and driver.


If i can keep my 3500 above 15" of vacuum in 5th (70-75 MPH) i can get 30+ MPG w/o using lean cruse mode and alot of timing.. With lean cruse mode and 40+ degrees of advance 35 MPG should be easy. I am fairly close to sea level though.

[SofaKingWeToddDid]

sounds good to me. ill trade you for my lumina... haha

[CNCguy]

Weight and drag have a huge impact on mileage. On Monday, I was talking to one of our customers with a LX9 MGB that had just returned from his fourth trip from Dayton to Vegas. He is a pilot and maintains excellent records about fuel consumption. Mack claims 35.8mpg average for the entire trip and a best of 41.9mpg per tank on flat open roads out west. The car is running a Ford T5 with a .63 5th gear, 3.89:1 rear axle and 215/60-14 tires.

I know it is comparing apples to oranges but they are some pretty decent mileage numbers.

[3400-95-Modified]

It's all in the power to weight ratio... Those 3100 equipped cars were underpowered for their weight so they got worse mileage.

I have been getting an average of 25-27 mpg on my .030 over 3400 in my Beretta that has a FD of 3.08 with a 2000 stall converter. That's combined highway and back roads, 45-50 speed limits.

I also got 27mpg with my 96 and at that time it was a 3.42 ratio, 3k stall converter and the big cam... Granted that was highway mileage but that was at a constant 75mph.

As other say there are too many variables to determine exactly why they get better mileage with a larger motor.

[PCGUY112887]

It seems that the gas station you use may set off your MPG's (if your calculating it that way) because different pumps don't seem to automatically click off at the same time, some fill your tank a bit fuller than others which will throw things off.

[robertisaar]

^ which is a good reason to go through multiple tanks of gas at the same pump using the same grade of fuel to get a realistic number...

[Rhedalert]

The 3100 in my sister's '02 Grand Prix is mated to a 3.29 FDR tranny. Any 3400 in the later W-bodies were 2.84 or maybe 2.93 or 3.08? This is probably the biggest contributing factor. The 3100 is not underpowered enough in this application to mess with fuel economy.

[nixtux]

My 95' Cutlass completely stock managed around 29MPG on the interstate (cruise at 70MPH.) Winter months I got around 27-28MPG. With a 16.5 Gallon tank in the summer
with A/C I could cruise 450 miles before I'd have to fill up. There wasn't much fuel left though.

Purely city, 30-40MPH I'd average around 20-22MPG.

I haven't had a chance to calculate the gas mileage on a 3400 since it started over heating after about 100 miles. But the tank was about 3/4 and in the end it was about a quarter tank. Seems to use more fuel but I don't know because I don't have any experience with it yet.

I will say the 3400 has a nice snap to it. But I hate the way the 4t40-e's shift.

[pocket-rocket]

I got 32-35mpg in the 92 on a long trip once a few years ago. Had the cruise set to 65 and was in a lot of nice wide open highway without much traffic or hills. I like lean cruise

[3400-95-Modified]

^ which is a good reason to go through multiple tanks of gas at the same pump using the same grade of fuel to get a realistic number...

Another thing you need to realize with MPG numbers... is the fact that some states are mandated to only sell E10% fuel... so those that don't have 10% Ethanol in their gas will get better mileage. I noticed a decent drop when that was mandated in my area.

[IsaacHayes]

^^ Yup, Everything here is now E10. Before it was in full affect there was one station who was last to convert. I went out of my way to go there because a tank would last quite a few more days.

[robertisaar]

then we get to factor in summer and winter blends of fuel....

summer=better MPG...

[no_doz]

whys that-does the stock tune go rich as hell with the addition of the computer sensing incoming cold air? if so... that sucks!