New guy to ford products. anyway here goes. I bought a 95 F150 swb with a 5.8 engine. So far all I know is it has a 3.08 Non L-S with E40D transmission. I have read some of the 95 5.8 are speed density and some are maft. What the heck is speed density and is this a good thing and why. Also the gas mileage on this thing is brutal. What can I do to improve it, the truck has 48,000miles. I am definitely changing the stock muffler out and if the gas mileage is this bad, what would happen if I put a lower gear ratio in and would it help performance. Help, new to fords, I need alot of help. I know fords use to run 351 clevelands and windsors, what is this 351 I have and help me feel better about this truck and its potential.

Thanks in advance.

 

To check to see if it's S/D(speed density) or MAF(Mass Air Flow)
look for 2 tube's coming from the air box all the way to the throttle body. Then it's S/D.
If you see one large tube going from the air box then it split's into 2 tube's just before the throttle body then it's MAF.

S/D, takes preset operating parameters and regulates the engine operation with those numbers.With M/A, the computer measures the air temerature and air flow traveling into the engine and is constantly adjusting the engine accordingly. most people, myself included, feel that mass air is much more responsive to modifications than speed density

Here's a pic of my 4.9L with MAF, ignore my FIPK K&N and you can see the MAF single large tube.

 

damn, mine is speed density.

Glad I learned this!


Pete

PS- I am fairly new here too and I also have a 95 F150 5.8L engine! strange!

 

I have a 93 F150 Super Cab 6 ft bed 4X2 with the 5.8 and a 3.55 rear

I get 16.5 higway 65-70 mph with tonneau AC off

I get 12 in the burbs

 

I got 13.5 @ 70-75mph with my '89 4x4 3.55's 5spd. OUCH we drove 1600 Miles. Gotta try a tune up.

Your engine is a Windsor with roller lifters (a big plus IMO).
Improved exauhst flow should improve performance and MPG's slightly. Lower gears will improve your performance but probably decrease your MPG's slightly.

 

The 351s do munch some fuel, and I've personally never seen real big gains in this area compared to the 302s and 300s. The taller gear should help some but don't have too high of hopes. Many recommend locking out overdrive below a certain speed to increase mileage, but I have found the opposite to be true on my 302. I lock out OD in some instances to save the truck from shifting more frequently, but have found that at any speed the truck will lug in OD my mileage goes up. If the 302 has enough torque to lug a lower gear and increase mileage, I'm sure the 351 does.

As for the SD/MAF debate personally I think it's overstated as a bonus. The sequential injection on the 302s gave a very slight torque increase, but I don't think it was due to the MAF but rather the injection system change. There are a lot of trucks with heavy mods and speed density systems, including blown 1st Gen Lightnings with lumpy cams.

 

I'm not sure of exactly what you mean but I pulled my 300 in my truck and dropped in the 351. Having had both in the exact same truck/driveline, there is no comparison between the two. The torque is substantially more while the HP difference is unreal. I found that I always had my foot to the floor with the 300 and never got any better than 14 mpg's with it even with complete tune ups. I've heard of guys getting 17-19 on the hwy but I never did. I am getting the same fuel economy now out of my 351 with twice the power, so no complaints here. I've not driven a truck with a 302 so I have no basis for comparison between them.

 

Spaceman,

I was comparing responses to efforts to increase mileage, not the power. Simply stated, I don't see many getting good mileage out of the 351s, but the 300s and 302s seem to improve easier in this area.

As an example my truck is a 4x4 extended cab, and with the 302 and some minor mods I average over 15 in town, and break 20 on the highway.. and that's with a slush box.