What is "Bad" MPG for a '94 5.7L ?

[bluetahoe]

On my old TBI G20 Ethanol free 91+ octane was worth a good MPG gain as long as the timing is advanced 6-8° from stock spec. The engine made alot more torque.

That's a good point. HIgher octane with ethanol vs regular non ethanol. And being able to advance the timing.

I've not done the 411 swap to make the programming easier and so haven't tried to play with timing.

I'm kind of waiting until I get more miles on it then do an LS and tranny swap.

But, I'm pretty happy with the MPG I'm getting on the highway. BTW, I get about 12 to 14 in town.

 

[bluetahoe]

On my old TBI G20 Ethanol free 91+ octane was worth a good MPG gain as long as the timing is advanced 6-8° from stock spec. The engine made alot more torque.

I can see the higher octane with timing advanced.
I'm having trouble posting so may be a repeat.

 

[LVJJJ]

back to the air box. Rip it out throw it away. And, you don't need to go buy any fancy cold air intake, just a 4" aluminum dryer duct, goes right into the hole in the fender and you squeeze the air cleaner end to oblong slip it over and secure with tape. Take out the little flipper door in the air cleaner intake, I took every part in there out for better air flow. The little tube you are missing is to heat the flipper door to open to help with cold starts. I think they are worthless, never had a bad cold start Takes the place of the choke that TBI doesn't have, or need. I tried a K&N but it robbed power so went back to stock, much better. Like I said, I cut a second hole in the air cleaner body and ran a 4" duct from the left fender, drilled a hole with a 4" hole saw. Engines need all the COLD air they can get.

 

[Trenton]

If it makes you feel any better, every mod I've done to my '98 K3500 with the 5.7 Vortec has resulted in no MPG increase although, i somehow managed 16.8 mpg on a 180 mile stretch of road in western colorado. I guess the premium fuel tune and high elevation helped a lot. After a performance coil and distributor, 8.5mm spark plug wires, ACDelco Iridiums, Volant cold air intake, single exit cat-back exhaust, and a Black Bear tune, I still manage only 10 mpg around town, same as it was stock. On the other hand, I still get 10 mpg even with going up to 33s on a 6 inch lift, so maybe all that did help lol.

 

[name]

back to the air box. Rip it out throw it away. And, you don't need to go buy any fancy cold air intake, just a 4" aluminum dryer duct, goes right into the hole in the fender and you squeeze the air cleaner end to oblong slip it over and secure with tape. Take out the little flipper door in the air cleaner intake, I took every part in there out for better air flow. The little tube you are missing is to heat the flipper door to open to help with cold starts. I think they are worthless, never had a bad cold start Takes the place of the choke that TBI doesn't have, or need. I tried a K&N but it robbed power so went back to stock, much better. Like I said, I cut a second hole in the air cleaner body and ran a 4" duct from the left fender, drilled a hole with a 4" hole saw. Engines need all the COLD air they can get.

I will rip that flipper door out of the stock air cleaner and run the dryer vent over to the passenger fender, But I would like to see some picks of the MOD you did to run the second hose to the drivers side .

 

[HotWheelsBurban]

Please don't spray WD40 on anything but tar on your fenders or a wet distributor (WD40 = Water Displacement formula #40), once dried it'll actually make things stickier. These R4s are known to be loud sometimes, it's a rotary piston pump and may have sloppy bearings and/or pistons internally. Run it until it dies and get a quality rebuilt, check your air gap on the clutch (s/b 0.020" - 0.030" pressed fit, the nut doesn't do anything to adjust it), flush the system, change the orifice tube, accumulator and/or condenser, but that's a different story, ha ha.

One of the issues with the R4 and newer style GM air compressors is they don't have an oil sump like the old school A6 long style does. When GM first came out with these in the late 70s if the system leaked down and you didn't suction it out and replace the dryer and orifice tube, the compressor would go out again. This design is way more sensitive to system leaks because the only oil supply is in the freon flow. I grew up in a parts store then and we all took the GM a/c training course; we had a lot of fleet customers in the Houston summer that needed to have working a/c!

 

[HotWheelsBurban]

My 99 5.7 stock vortec suburban gets around 12 to 13 in city driving, 15 or 16 on the road, even loaded and with a utility trailer. It's a big heavy slightly aerodynamic box, the brand new one doesn't do a lot better

 

[DerekTheGreat]

...Take out the little flipper door in the air cleaner intake, I took every part in there out for better air flow. The little tube you are missing is to heat the flipper door to open to help with cold starts. I think they are worthless, never had a bad cold start Takes the place of the choke that TBI doesn't have, or need..

That flipper door isn't for help with cold starts and it does not take place of a choke, carb'd cars had them for years.. It is there to prevent the throttle body from icing/slushing up.. Temps under 40F combined with high humidity are the perfect cocktail for that situation to happen. It's never happened to me personally but I run the stock system as it is. If you live in a an area that doesn't see those conditions ever, you can remove it. Otherwise, just lubricate it and make sure the mechanism moves freely as it needs to and it'll open up completely as needed when warmed up. Provided the stove pipe thing going down to the exhaust manifold is connected and in good shape. The engine does get cold air from the stock intake, it pulls from the fender which pulls from the core support.

 

[Supercharged111]

I was under the impression it was to mix warm air with the fuel?

 

[name]

What is that round thing that looks like some kind of sensor, that sits right behind that flipper door ?