I have an EFI system, how would it make no difference? Would the engine read power and mixture adjustments and correct for the alteration?

 

The spacer is doing nothing if it is not downstream of the injector(s)

As burnout said, it may make a difference with TBI or a carburetor but will do nothing for you except make your wallet lighter.

 

check emission control components. depending on what ex mods you have, they could be throwing some sensors out of whack

 

Yup, the only way they'll work is if the air/fuel mix goes through it. On a multi-port system only air is going through the throttle body and the fuel doesn't get injected until the last moment.

 

Another thought. On most modern cars, there are two engine temperature senders. One goes to your gauge on the dash. The other goes to your engine computer. If the one going to the computer is malfunctioning, it might cause your engine to eternally run in the warm up mode. This gives the engine a richer fuel mixture than it needs, thereby wasting gas.

You may have a fuel leak somewhere. You should park your truck running and warmed up on some clean pavement so you can check for drips. Locate the fuel lines under the truck and follow them all the way up to the engine.

Also, like others have said, check your emissions controls and accessories for proper operation. Make sure the bulb in the Check engine light is functional. It should come on when you turn the ignition to on, then off when you start up the truck.

 

I recently put new tires on my truck and a new exhaust sytem and i've been driving it lightfooted. I have managed to bring my mpg up by about 1.5 per gallon, that might not seem like much but IMO, every mpg matters. I currently get close to 12mpg.

 

You covered the problem right here!!!!! Every time you make it sound "good" your fuel mileage goes right out the tail pipe!!!!!!

You don't have to floor it to kill your MPG, just on and off to make it sound "good" will do it to.. Smooth and steady will help as much or more than anything else!!

So modify your driving habits or pay at the pump... Your choice!!!

 

I also agree that this is your problem! Everytime you "blip" the throttle to make it "sound good", you mileage is going out the window. I remember when I was a kid though, it was hard to not show off a little, but we all learn in due time. If you want good mileage, don't do any hot rodding at all, and lke stated above, you don't have to floor it to get terrible fuel mileage. Change your driving habits and I bet you anything that your mileage will go up. There's not add on that will help.

 

Yup, what he said. Throttle up nice and smooth when takin off from a stop, back off early and let her coast a bit when comin to a stop. Sound good, sure. But you'll pay for it. My 351 sounds great, but idle fuel flow at 600 RPM without a/c or air compressor runnin hangs around .60 GPH (Gallons Per Hour). Get on the loud pedal and it climbs and climbs and climbs... at full throttle I've seen 12.

Yeah, 12 gallons per hour... that's around $43 an hour in fuel. Of course I don't run my engine at full power all day long but even then at cruising speed I still see around 3.25 GPH runnin unloaded at 65 on the highway with 3.55 gears and E4OD.

I do love to hear healthy engines run...(not 4 banger imports). V8 gas, V8 diesels, V16 diesels, old John Deere 2-cylinders, turbofans, straight turbines, reciprocating...

so what I do is get loud exhaust. Since I hardly ever get on it, it's hardly ever real loud but I can hear it just fine cruising or under mild throttle.

Also...

Don't haul junk around. Got scrap metal in the bed waitin to go to the yard? Put it next to your house til you're ready to take it there. More weight, more fuel.

Inflate your tires to the recommended pressure, or the max pressure shown on the tire sidewall, whichever comes first.

Driving with your tailgate up/down makes no apparent difference in my truck. Yours might be different. Experiment with it.

Do you really need to go thru the drivethru at McDonald's? What's the harm in parking the truck and walking in instead of lettin it idle while the person in front of you with a minivan full of kids tries to get their order straight?

Driving offroad gets you crap mileage. Exploring trails while crawlin along at 5 MPH is fun, just be sure to plan for the fuel usage accordingly.

 

If anything leaving it up will HELP with aerodynamics/mileage. It's been shown that with the tailgate up the air in the bed rolls and the air coming off the cab just goes right over it, whereas if you put it down or take it off there is turbulence behind the cab which has a kind of suction effect.

 

Yep. The only ones who argue against this are rednecks. Those who have tested it scientifically say tailgate up. With the tailgate up, there is a "bubble" of circulating air behind the cab that allows most of the air to flow smoothly over the top--"laminar air flow". With the tailgate down, that bubble doesn't form, and there are many small vortices that disrupt the airflow over the top, adding to drag.

I think I did hear that the one exception is short bed, full size trucks.

I agree with the others, though. Tune it up and take the lead out of your shoes.

Jason

 

The ideal is as I said before, a toneau cover. By my understanding short and long make a difference. But a short bed should always be better with the tailgate up. The only truck that might do better tailgate down is a crew cab long box. There is much more time/distance for the air to settle in between the grill/windsheild and the tailgate.

 

Yeah a bed cover is ideal. I personally don't like those things. I have a pickup so I can toss stuff in the bed, not crack it open like a car trunk. But that's just me.

 

I've had two longbed trucks, and I've had enough loose junk in the bed to see the effects--the airflow is down in the back near the tailgate and up near the rear window--and it's not high-speed air, it's the slow bubble of air. I've even seen stuff caught in the bubble doing loops.

I have a good friend who went through the Aviation Engineering program at Purdue. They did all the calculations--it's tailgate up on a longbed for best mileage. Mythbusters tested it also--tailgate up. Sorry, my friend, but you're on the wrong side of science.

Jason

 

Did mythbusters test a toneau? I red an article in some 4x4 mag that was laying around at work that said tailagte up too but they said a toneau was best overall. They tested in a wind tunnel too.