Any secrets for a bumping MPG on 1998 305?

[L31MaxExpress]

I know the 0411 swap has been mentioned, but I haven't seen anyone recommend a tune yet which is surprising.

I implied a tune with the mention of the 0411 swap. Factory 0411 itself even if you merely deleted the VATS and installed it with the factory L30 van tune will give a little better MPG. The other added benifit is the 0411 can easily control electric fans. Electrc fans run only when needed so that helps MPG.

While I did them for power, the March Underdrive pulleys and 1.6 roller rockers gave my 350 a little better mileage too. Every bit of power loss recovered from reducing friction helps mileage.

I used synthetic gear oil in the rear-end, synthetic wheel bearing grease when I did the front brakes, and used synthetic caliper grease on the slide pins to help keep them moving freely. Also replaced the calipers and all 3 brake hoses. I had a caliper sticking and just shot gunned the front brakes because I used the larger 8800 GVW calipers for better stopping.

 

[PlayingWithTBI]

thanks for that detailed response, I knew it was a thing from PWTBI but I never really understood what it was. makes sense to me I think.

yeah, it works. Some people think you'll create too much heat in the combustion chamber but, after miles and miles of data logging I saw zero Knock Counts and engine ran nice and cool.

 

[454cid]

Its basically a mode that is in the PCM that comes disabled in the US, but was active in Australia. At crusing speeds and light loads does exactly as the name suggests. It commands the air/fuel ratio leaner than 14.7:1 and ignores the 02 sensors since they do nothing leaner than 14.7. At 50-80 mph on flat road or downhill, I cruise about 16.5:1 with 3-4° more timing than at 14.7:1. If I need power to climb or go into a headwind the added load richens the mixture back up for added power. Works similar to a power valve or metering rod setup in a carb.

So what's the down side? It being disabled make no sense to me in a day and age with CAFE, unless maybe more emissions... maybe NOx?

 

[PlayingWithTBI]

unless maybe more emissions... maybe NOx?

Yep

 

[L31MaxExpress]

So what's the down side? It being disabled make no sense to me in a day and age with CAFE, unless maybe more emissions... maybe NOx?

Yep NOx. The way GM used the EGR system on the vortecs was not for MPG either. Purely NOx reduction. The EGR valve is wide open for acceleration up until the Power Enrichment mode is activated above the 90% TPS trigger, the time delay and rpm lower limit is reached and almost completely closed at normal cruising speeds. My Express van always had a slight but noticeable hesitation off-idle with the EGR enabled, disabled it disappeared completely. At say 20% throttle moving away from a stop, even at 1,200 rpm it was opening the EGR 60-80%. At cruising speed not uncommon to see 10-30% EGR opening commanded. For purely fuel economy reasons EGR would be disabled under higher engine loads and fully open at crusing speeds. With the EGR fully open pumping losses would be minimized at cruising speed.

 

[wb292]

Reducing rolling resistance is the key. This applies to every moving part in the truck. From the internal resistance of the engine spinning to the tires rolling. There is no one thing that can be done, but a lot of little things add up. A lighter weight oil in the engine will reduce the amount of power needed to rotate. A 75w90 oil in the axle instead of a 85W140. Airing the tires up to their max pressure on the sidewall will reduce the contact patch and reduce rolling resistance. Not the other way around. Reducing back pressure in the exhaust makes the engine work less to remove the gasses from the cylinders. Therefore less throttle is needed to do the same work. Using quality tune up parts can help. Like spark plugs and wires with less OHM resistance to get a bigger spark and a more complete burn. This will require less throttle to maintain speed. Remove ANYTHING that is not needed for the truck to operate safely. The less weight the truck moves the less fuel it takes to move it. Also your right foot is the biggest factor. When cruising slowly back off the throttle until the truck starts to slow. Then apply just enough the maintain the speed you want. You can use more throttle with out increasing speed this will burn more fuel.

 

[F4U-1A]

Do you still have original poopete fuel injection or have upgraded multi port? Running your tires at 35 or a little more is ideal, there is no great advatage doing a math problem for max psi on an LT tire. The max psi is for operating at max load capacity. There is no decernable benefit. Now if you want B 777 Freighter with 35 ply 24's, dry oil free nitrogen adjusted for standard day plus 6, pressure altitude plus 850, we can do that. Did anyone mention get a 350?

Worked on and calibrated Aircraft weigh scales, for DND Canada. Each one could take a lot of LBs, KGs. One per wheel, too get a take off weight for a loaded C130.

 

[Frank Enstein]

Put a vacuum gauge in the truck and make a game of how high you can keep the vacuum.

Back in when you come home and when you leave don't let the engine "warm up". Just drive slowly and smoothly until the engine gets to operating temp. A warming up engine gets zero mpg.

Index the spark plugs so the side electrode is up. Some engines really respond to this. Same with larger plug gaps/hotter ignition.

 

[F4U-1A]

My 5.7 (350) gets 20MPG ( US Gals). When my wife pilots it!

 

[F4U-1A]

Put a vacuum gauge in the truck and make a game of how high you can keep the vacuum.

Back in when you come home and when you leave don't let the engine "warm up". Just drive slowly and smoothly until the engine gets to operating temp. A warming up engine gets zero mpg.

Index the spark plugs so the side electrode is up. Some engines really respond to this. Same with larger plug gaps/hotter ignition.

Simpsons? Skinner?