LS in a Brick

[XCRN]

I am in the process of building a new drivetrain for my LS swapped TJ Wrangler, and since starting from scratch I want to see what I can do to make it more fuel efficient, primarily to extend the range more than save money. Obviously a V8 brick can only go so far but I have what I believe to be realistic goals.

Now I am wanting to build a new powertrain, one that has a bit more power but can be more efficient. I have an aluminum 6.2 L92 VVT engine as a base with a 6L80 from an 07 Escalade. Given the nearly 6000lb luxory brick this motor came from can get 13/20mpg, I am sure my 3200lb brick could get better. Ideally I would like to reach or exceed low to mid 20s highway and 16 or above city. Obviously anything over would be better.

As a baseline, when this was a stock 4.0 and 5-speed no doors no top it got I think around 11-12mpg mixed city/country typically from what I recall but I have had it has high as 18-19 on the highway with doors and soft top. I remeber having to drop it down a gear multiple times and give it 100% throttle just to maintain highway speed on windy days.

With a cammed 5.3 LS from a 2000 Silverado with a Holley Terminator X using the Jeep 5-speed no doors or top I get a pretty consistent 13-14 mixed city/country. Since finishing the build I never really got solid highway data, it still struggles but not nearly as bad and I can stay in 5th the whole time with plenty of passing power. So it managed to get better slightly with 100 extra hp and an engine management meant for race cars.

So now my question with rebuilding this new 6.2 from scratch, what are some things I can use to make this engine more effiecient? Is there camshafts that would be better for fuel economy or is a factory cam the best? I have also considered the idea of destroking with a 4.8 crank, but not sure if that would make any worthwhile gains. I plan on using a factory E38 PCM, and because I will be going to some very remote areas with limited fuel options so I need to
safely be able to run 87 octane so a stupid high compression ratio is not ideal.

Right now I have a 6L80 6-speed auto that I could rebuild, is there anything I can do during the rebuild to help increase efficiency? Could I do more with a 4L60? would like to stick with a manual, but no way the stock NV3550 will handle the power without worry.

My primary concern is extending range, which making the engine more fuel effiecent will be a big part of this. Anyways I hope to hear from this knowledgeable community on reaching or exceeding my goals.

[freebeard]

So now my question with rebuilding this new 6.2 from scratch, what are some things I can use to make this engine more effiecient?

Since you ask.... boat tail!


https://en.wikipedia.org/wiki/Hafner_Rotabuggy

[cRiPpLe_rOoStEr]

Forget a de-stroking, as it would most likely make the engine more rev-happy and set the peak torque to a higher RPM when you could benefit more from low-end torque. Maybe it would be worth to look at the camshaft and the intake and exhaust headers in order to improve low-end torque, even though it would most likely sacrifice power and decrease the useful RPM band.

[XCRN]

Originally Posted by cRiPpLe_rOoStEr

Forget a de-stroking, as it would most likely make the engine more rev-happy and set the peak torque to a higher RPM when you could benefit more from low-end torque. Maybe it would be worth to look at the camshaft and the intake and exhaust headers in order to improve low-end torque, even though it would most likely sacrifice power and decrease the useful RPM band.

I have been looking to see what camshafts are out there for this application, and not suprisingly any of the low end power cams are a little extream and would probably negate any mpg gains. But I do know about what powerband I mostly sit at while crusing so I might be able to call a cam manufacturer and give them some data.

That makes sense on destroking it, but would doing the opposite of stroking this motor maybe do me better if I tend to stay under 2200rpm? Or would I be better off leaving the crank stroke as is? There is a shop near me that manufactures forged crank and rods and I can get everything to do the short block, including maching for a very decent price, and I have a few options for stroke length and piston options for compression ratio.

[brucepick]

It's shaped like a brick. It will have all the aerodynamic advantages of an open parachute. Give it a new body with an aero-optimized teardrop shape.

[XCRN]

Originally Posted by brucepick

It's shaped like a brick. It will have all the aerodynamic advantages of an open parachute. Give it a new body with an aero-optimized teardrop shape.

Agreed a newer body would help on highway and I am thinking of ways to possibly deflect air a bit better without affecting functionality of a Jeep, but I am planning a trip with roughly 500 mile drive on dirt/gravel road where I will not be going fast enough to benefit from major aero. Thats why I want to look at my options for an engine in particular since I have it on the stand now ready for machine work and new parts.

[freebeard]

I am thinking of ways to possibly deflect air a bit better without affecting functionality of a Jeep

Permalink #2 was a little over the top, since it was quick and easy.

Consider: Trailer hitch reciever > hitch mount crossbar clamps to existing bumper with wheelie bar[s] > cargo box or clamshell doors in a square or octagonal frustrum.. Front face the Jeep. back face a truncation.

For the front, a three-piece windshield like the Shalako buggy: http://www.dunebuggyarchives.com/sta...buggy004-1.jpg

[Ecky]

Drivetrain-wise, the low hanging fruit for highway driving is in the gearing. Having a cam that doesn't have a ton of overlap (e.g. a cam not for top end power) is generally going to deliver better economy too.

But as brucepick says, you'll likely get more mileage out of even subtle body changes. Smooth underbody paneling, wind deflectors in front of the wheels, maybe an air dam, fenders that close off the sides of the wheel well gap, maybe even some kind of diffuser for the rear.

Nice looking Jeep.

[ksa8907]

I mean no offense, but 6.2 v8 and fuel economy aren't really synonymous. You're putting an engine in your jeep that makes 2x the power you need with a stock tune.

You're somewhat in uncharted territory because nobody builds a 6.2 v8 for economy so cams and tunes are non-existent.

If you're using the jeep for jeep activities, use a truck cam if there is one more specific for low speed torque, otherwise stock will be fine. Beyond that, electric power steering?

[cRiPpLe_rOoStEr]

Originally Posted by brucepick

Give it a new body with an aero-optimized teardrop shape.

Not sure if trying to turn a Wrangler into a Rumpler Tropfenwagen replica would be so easy, yet the body-on-frame layout is quite well suited to some extreme bodywork to enhance aerodynamics.