Ways to increase the efficiency of a GM 5.3L

[Isaac Zachary]

Originally Posted by Solarpowered

I'm not sure if there are any lighter pistons that would increase efficiency. One would think that forged pistons pack more material into a smaller package. Thus increasing the density, and increasing the weight.

It's not just the weight. It's mainly the clearances. Forged pistons are stronger (good for racing applications) but expand more. Therefore you need greater clearances, therefore the pistons rock and slap more, therefore you get more friction and wear.

Here's an example:

https://www.youtube.com/watch?v=rN2ND_FPnUA

[Isaac Zachary]

Originally Posted by Solarpowered

As for the cylinder head thing, that's something I haven't really been able to work out well. You can port and polish, but where is the stopping point? There must be a sweet spot somewhere, and if you go over that, now you have to spray more fuel.

But there comes a point where you increased power by doing that, and thus you might have increased efficiency somewhat.

Intakes are more about keeping the fuel atomized. Rough can be better because of that.

Usually your best bet is getting OEM stock heads and getting the valve seats cut right. The company that build the original engine probably did more testing and research than any aftermarket company. If you want great atomization you need to do a lot of work. Wetflow is a lot of trial and error, something probably not worth the extra 5mpg.

https://www.youtube.com/watch?v=f8XG9T8v-ng&t=7s

https://www.youtube.com/watch?v=BFypM7ADAA0

https://www.youtube.com/watch?v=lcxp9ufC1DY&t=5s

[oil pan 4]

Simple Aerodynamic mods would out preform that entire list.
No aluminum crank shaft, not even single cylinder engines use aluminum crankshafts.
The 5.3L connecting rods are already as light as they can be. After market will tend to go heavier and stonger.
The 5.3 manifold is already very well flowing. The only way you might be able to improve on it noticeably is go with ridiculously long tube headers optimized for cruise RPM, which means they will end up being like 8 foot long primaries.

[Isaac Zachary]

Originally Posted by oil pan 4

Simple Aerodynamic mods would out preform that entire list.
No aluminum crank shaft, not even single cylinder engines use aluminum crankshafts.
The 5.3L connecting rods are already as light as they can be. After market will tend to go heavier and stonger.
The 5.3 manifold is already very well flowing. The only way you might be able to improve on it noticeably is go with ridiculously long tube headers optimized for cruise RPM, which means they will end up being like 8 foot long primaries.

Exactly! Unless this is used at low speeds only.

One note about intake flow, unless it's a diesel, your greatest restriction is the throttle. Unless you remove the throttle or at least drive around with it wide open, there's no point in reducing intake restriction and increasing flow. Your best bet is an intake that keeps the fuel atomized, and that's all that really matters.

[Isaac Zachary]

Originally Posted by Solarpowered

13. Aluminum or carbon fiber driveshaft
...
16. Internally balanced. The crank itself is balanced, and does not need a harmonic balancer or balanced flywheel? Seems like less rotating mass if no harmonic balancer

With number 13 I'd have to ask at what point would it be better to just get a different truck? I mean, it's one thing to tune the carb and advance the timing. It's another to pour thousands or tens of thousands into an old truck.

With number 16, a good balance will never completely remove all imbalances in a crossplane V8. But it may be good enough to not need a harmonic balancer.

[Solarpowered]

Originally Posted by Isaac Zachary

With number 13 I'd have to ask at what point would it be better to just get a different truck? I mean, it's one thing to tune the carb and advance the timing. It's another to pour thousands or tens of thousands into an old truck.

With number 16, a good balance will never completely remove all imbalances in a crossplane V8. But it may be good enough to not need a harmonic balancer.

And if you managed to lower the total rotational mass of the engine by 10%, well that's 10% less power needed to start that push, every cycle. So ideally the computer would detect this and spray less fuel. There's all manner of varying opinions here, but all these 1 and 2% increases add up. In the end, if you were able to squeeze out a 25% gain in fuel efficiency from the engine, I'd call that a big win. Even if it were quite expensive, if you're going to drive that vehicle for a very long time (and many of us are) then it will still be worth it. You'll eventually reach the point where the fuel savings have paid for the cost of the changes, and everything after that would be money saved.

As for the aluminum or carbon driveshaft, it sounds like you may be thinking they're more expensive than they actually are. An aluminum driveshaft is an excellent upgrade to any old vehicle with a cult following, like the 73-87 "Squarebody" chevy trucks.

And to reply to several posts at once, yes of course aerodynamics, tire pressure, the driver's foot pressure, etc ad infinitum are also important. I kinda took that as a given.

[Isaac Zachary]

Originally Posted by Solarpowered

And if you managed to lower the total rotational mass of the engine by 10%, well that's 10% less power needed to start that push, every cycle. So ideally the computer would detect this and spray less fuel.

The rotational mass or inertia is only part of the total inertial mass. So if you lower the rotational inertia by 10%, but rotational inetia is only, say, 20% of total inertia, then you only saved 1%.

The drive shaft also doesn't have a lot of inertia, even if it has a lot of mass. That's because 1. it usually spins slower than the engine, at least when starting out and 2. its mass has a small diameter, not a large one like the flywheel or the wheels.

I could be wrong, but I read somewhere that around 80% of the rotational inertia is in the flywheel. That's why you usually start there before reducing other things.

Aluminum also doesn't fatigue well.

But yes, every little thing adds up. However, there are things that may help only a fraction of a percent, and other things that would be better to put that money towards and get you more percents. Tuning each cylinder for fuel and spark would be one of those things.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

One note about intake flow, unless it's a diesel, your greatest restriction is the throttle.

No wonder some newer engines are either getting rid of the throttle at all, or only keeping it as a quick vacuum provision for brake boosters. And since most throttle-bodies are electronic nowadays, sometimes it's possible to have a remap allowing the throttle to stay wide-open at a broader RPM band.

[Solarpowered]

Originally Posted by Isaac Zachary

The rotational mass or inertia is only part of the total inertial mass. So if you lower the rotational inertia by 10%, but rotational inetia is only, say, 20% of total inertia, then you only saved 1%.

The drive shaft also doesn't have a lot of inertia, even if it has a lot of mass. That's because 1. it usually spins slower than the engine, at least when starting out and 2. its mass has a small diameter, not a large one like the flywheel or the wheels.

I could be wrong, but I read somewhere that around 80% of the rotational inertia is in the flywheel. That's why you usually start there before reducing other things.

Aluminum also doesn't fatigue well.

But yes, every little thing adds up. However, there are things that may help only a fraction of a percent, and other things that would be better to put that money towards and get you more percents. Tuning each cylinder for fuel and spark would be one of those things.

Sure, and I'd like to know what that list is. You said aluminum flywheel. I have heard somewhere that they do "wear out" and need to be replaced eventually. But what about that harder aluminum? Maybe not cost effective in this case. All the racing guys seem to love aluminum driveshafts. So it would at least be good for a bit of power, if not actual fuel economy gains.

Back to this list of proven mileage increasers, maybe low rolling resistance tires should be considered. You'd just wait until your tires were worn out and had to be replaced anyway.

Is there a master list for typical internal combustion engines somewhere on this forum? Seems like there would be something like that by now.

I did find more efficient alternators:

Well I can't post a link.

[Isaac Zachary]

Originally Posted by Solarpowered

Sure, and I'd like to know what that list is. You said aluminum flywheel. I have heard somewhere that they do "wear out" and need to be replaced eventually. But what about that harder aluminum? Maybe not cost effective in this case. All the racing guys seem to love aluminum driveshafts. So it would at least be good for a bit of power, if not actual fuel economy gains.

I didn't say aluminum flywheel. I take it this is a stick shift?

At any rate aluminum does wear down from fatigue in something that's constantly getting "bent" back and forth. For surface wear there are ways to extend it's life if it's something like a flywheel that's not going to be flexing back and forth due to it's shape. Nikasil coatings come to mind.

One thing to keep in mind, and what I'm trying to say, is that racing guys will use aluminum, but they're not after longevity. Some races you rebuild the engine and replace important parts after every few races, or even after every race. Aluminum does last a long time for some parts, like pistons. But I'd be weary about things like a drive shaft.

Originally Posted by Solarpowered

Back to this list of proven mileage increasers, maybe low rolling resistance tires should be considered. You'd just wait until your tires were worn out and had to be replaced anyway.

Low rolling resistance tires are a good idea for fuel mileage.

Originally Posted by Solarpowered

Is there a master list for typical internal combustion engines somewhere on this forum? Seems like there would be something like that by now.

Yes, but maybe not as in depth as you want. The 65+ Efficiency Mods button up at the top of the page is that list.

Originally Posted by Solarpowered

I did find more efficient alternators:

Well I can't post a link.

Cool! I think you have to be on the forum for a certain amount of time to get the privledge to post links.