Engine mods. for max MPG on 7.4 OBS

[SRB]

I'm all ears.

[N0DIH]

To go all out mpg you do lose some driveability. But in general tuning the PCM can help more than most things.

[Blazerguy]

The obvious answer is this (http://www.chevrolet.com/cruze-compact-car/)

I've played around with aggresive tuning such that mpg improves but as stated above driveability suffers. Normal calibrations are reached at WOT of course. Still working on my tune such that part throttle driveability is not so affected that I just give up and mash it...worsening mpg anyway. Getting there :-)

[PonyKiller87]

Yeah getting a cheap beater car that gets 30 mpg is your best way to save money on gas when you have a BBC. Only drive the truck when you have to and drive the car the rest of the time. Just get a beater thats halfway fun to drive. I picked up a 98 saab 900 with a 2.0 Turbo motor, that little thing hauls ass.

[SRB]

Thats waht Im looking for. Great link. As my truck gets older the economy decreases. Went from 13-14 to 10-11. I guess 12 was out of the question for the old girl. The engine has a hard time with hot stars. I do know the remedy for that. What type of injectors would work ther best for me. I dont run it hard. It pulls an RV and Stock tailer around at times plus occational trips into town. It stays parked most of the time only hass 98k on it. I am also looking at changing intake and exhaust soon. I just cant get rid of it and i want play around with a few things.

[SRB]

I have seen and heard of some outrageous claims as high as 17 pulling load running 80. I really think that is a little far fetched. But if someone here has done that or even consistantly maintained 14 Id really like to know what they did

[N0DIH]

Reality is the 454's don't get good mpg, but as for why, I would like to know more.

My benchmark is a 76 Olds 98 Regency weighs right at 5000 lbs, with 1000 lbs of most any of our trucks (shipping weight to shipping weight), my 99 K2500 Burb shipping weight is 5625 lbs, probably heavier than most on average (Dually CCLB would prob be heavier). And with 2.73 gears, CARB, nasty emissions, pellet type cat, small single exhaust, a cam that would be a shame to put in a 4.3L Olds V8, brick wall aero, not as high as our trucks, but just about as bad, was EPA rated at 12 city and 18 highway.

Note, no port EFI, no fast burn cyl heads, no overdrive, no lockup converter. And it is rated far better than most any 454 in a truck has ever got. Heck, 350's don't get close to that.

So, what is up? You are talking the best of the 454's are lucky to 14 mpg, and this one regularly got 18. And I had a 76 Olds Delta 88 Royale and mine got 18-19 highway at 75 mph and even a handful of times got 22-23.

So, my feelings are that all things need to be looked at and better mpg should be not too hard to do.

[SRB]

We can never make the 454 a tree hugger, but spending a little $ over time on modifications in order to make the 454 as efficient as possible without turing it into a 4 cylinder burning vegitable oil i think is worth the time and effort.I just lack the knowlege. Just found this forum and had no idea that there were no so many who loved this engine and body style of truck. I have no plans to ever sell mine. What ever i do to it will always be cheaper than a new one. Plus for me it is as comfortable as a new one and in my oppinon looks better. Hell its part of the family. I guess the first thing Im goiong to do after all these years of owning it is start with the air intake.

[N0DIH]

I can't knock it, the 454 can take a pounding and keep on rolling on. Its a tough ole bird!

I have thought about selling mine for a 6.0L Burb, but reality is the cost I would incur on the newer truck would never be recouped in mpg. Drive the old truck, and best of all it is a GMT410 Suburban! Love it!

It is only missing a DMax.... And I have thought about it!

[1998454]

I know a guy with a 1976 3/** 4x4 454, 400 turbo and 3.73 gears....3-4mpg over my 98...hard to understand what with his having the aerodynamics of a cinder block and a high tech q-jet....

[PonyKiller87]

I think it mainly comes down to the tranny and the tuning. YOu have a 4L80e which has a ton of loss and then you have things like Torque Managment that kill the out put of the engine in order to save the tranny and make it shift like a car.

Throw a better converter in it, kill the TM, crank up the preasure so you can eliminate as much of the loss as you can and I bet it shows big improvements.

[SRB]

Torque converter I understand. TM ? Crank up the pressure? Not a tranny man.

[1998454]

TM is torque management where the engine experiences reduced power during shifts. And the trans line pressure increase would help the trans deal with tm being removed. The converter wouldn't help me much because I get $hit for mileage on the highway with the converter locked the whole time. I just need a tune to start...
Torque converter I understand. TM ? Crank up the pressure? Not a tranny man.

[SRB]

Thanks. The trans will stay intact unles repair is needed. I think the intake will be a good place to experiment with.

['05TJLWBRUBY]

Coming from my modded Jeep that I run to the trails, drop in low range and lock it up, then unlock and hit the highway back home again, I'm used to squeezing every last drip of fuel out of the rig that I can. Jeep is a brick on wheels to say the least. Unfortunately the 3/4 ton Suburban 454 does worse than the Jeep!

What I've found is keeping the rig in top mechanical condition is your best bet. Don't let little problems or general maintenance stretch out far beyond recommended intervals. Meaning don't stretch your spark plugs till they hit porcelain. Don't just spray your TB-actually remove it and thoroughly clean with a good cleaner and toothbrush to mirror finish. Change the air filter regularly. I prefer standard Wix paper elements on both rigs. Resist urge to run big tires-or wide tires. On the Jeep, I run a 255/85/16 which is 33.5" tall and about 10" wide. The Suburban currently has a mis-matched set of 265/75/16s. Came this way when I traded for it. The rears are literally shot and almost racing slicks. I'll be doing new tires soon to replace all 4 of them and will be going a bit narrower with a 235/85/16 to see if I can't get a bit better mileage (MPG not tire life) out of a narrower size. My experience holds true on about every other rig I've run-narrower tires do take less fuel to turn, and highway tread are better than mud terrains. I run aggressive tires on the Jeep but the Sub will see a M/S rated highway tire. Thinking the Toyo ATs with Tuff Duty for this set. With that, tire pressure needs to be kept and maintained. You'll see better mileage with a bit more pressure in the tires. I run single digits off-road in the Jeep but on the highway bump them up to around 32psi for best fuel economy. The Sub will see a bit higher yet than that I think when I'm done experimenting.

Back to the maintenance bit. My rig is a '97 and in need of exhaust work. I am assuming that any new cat will perform better than 15 year old technology. A better free flowing exhaust (likely won't do headers, just can't afford it now) with new high flow cats and muffler will help. The tune will be the last of the equation and I plan to send it to Black Bear for the tune once I'm done getting all the little mechanical things fixed first. I'd like to believe with all of this done, I should squeeze a couple mpg's out of it and average at least a solid 16. Well, I'll be happy if I can do that. Winter fuel is another biggie for now and if you can find pure gas in your state, run that instead of the crap with ethanol. A simple fuel change to pure gas alone in our '07 Subaru yielded 5mpg better mileage on multiple tanks for IN TOWN driving and a 3mpg increase at highway speeds. In the Jeep, I saw a 2mpg increase at highway speeds consistently over multiple tanks, changing nothing but fuel alone. All 87 octane, pure gas, no ethanol. Since taking ownership of the Sub, this is all I've run through it so I don't' know what the difference would be there and I'm not going to switch to find out.

Air intakes-did that on the Jeep to make room for under hood stuff. Thought about it on the Suburban to smooth it out but it seems the factory setup is tuned and needs the resonators to help with the MAF. I'm not going to mess with this after all, leave well enough alone and just run a good Wix paper filter. Put the money where it will do the most good in getting the rig to optimum running condition first, or buy a couple tanks of fuel for the cost of a CAI kit. Would be money better spent.

Best of Luck,

Mike

[1998454]

I would hope the jeep would get better mileage than a big block suburban. My cavalier gets better mileage than my truck as well....
Coming from my modded Jeep that I run to the trails, drop in low range and lock it up, then unlock and hit the highway back home again, I'm used to squeezing every last drip of fuel out of the rig that I can. Jeep is a brick on wheels to say the least. Unfortunately the 3/4 ton Suburban 454 does worse than the Jeep!