Best engine for a mini-RV?

[ThomCat316]

One of my fantasy projects is to stretch out a Gen-2 S-10/Sonoma ex-cab frame about 3-4 ft., plop a crew cab body on it, and build a streamlined camper uni-box to replace the bed. The box wouldn't exceed the cross-section of the cab at any point (while driving).

Sort of a super-streamlined RV/camper. I expect ca. 30MPG hwy. based on the Sonoma I'm driving now, and possibly better if I'm willing to pan the belly.

I have all the necessary knowledge to do this based on the 2.2L 4-cyl injected gas engine that is stock in the S-10, but a thought popped into my head... Is a diesel engine more appropriate to this? I did some reading, and found some pros and cons:

Pros -
More torque, allowing taller overall gearing.
Generally better instantaneous economy.
Fuel almost always available, esp. in remote areas.
Can be tuned for biodiesel if available.
Common-rail gives excellent economy.
Mechanical injection gives long service life.
Extremely simple to add tank capacity - I don't mind 1400-1500 miles between fuel stops.

Cons -
The fuel really stinks.
More torque may require replacement drivetrain components.
Long-term economy can be compromised by costlier repairs.
Mechanical injection is prone to soot production, especially at the targeted low cruise RPMs.
Common-rail is very finicky about fuel quality, and is very expensive to repair.
I can repair/rebuild the gas engine under a tarp-tent almost anywhere that UPS/FedEx can find with tools I already own... :-)

So I've thought about it a lot, and am leaning toward simply getting a 2.2L gas motor massaged properly by a local race shop, but I thought I'd toss this out to the more experienced members of the community and see what consensus develops.

Any thoughts?

Thanks!
Thomcat

[JRMichler]

If you make your RV/topper hinged, you will be able to get some impressive MPG with a gas engine. Something like this, except some fabric panels to fill the side triangles:

[UltArc]

I think 30 may be ambitious for the vehicle, especially while increasing cd(depending on design), and increasing weight.

[Sporty Modder]

A good read on rv's...
http://ecomodder.com/forum/showthrea...lly-13149.html

Also a good read on somthing more along your lines...
http://ecomodder.com/forum/showthrea...9-a-23152.html

[JRMichler]

I think that 30 MPG with a gas engine is not only realistic, but conservative. Make a hinged aero topper with some sort of fabric sides. The long box will allow the top to taper way down.

For the interior layout, google "teardrop trailer". Those trailers have solutions for a similar shape. I would put a piece of plywood over the wheel wells with a mattress on top. The space under the plywood would be storage plus a slide out kitchen. With careful design, the result would have room for two.

Use the space underneath and around the frame for more storage and a belly pan.

[elhigh]

I think 30 is completely achievable. I don't think the 2.2 that was the base engine on the 2nd-gen S-10 would be any fun considering the weight you're talking about adding, you might do better with the 2.8 LK5 engine. Still a four, but way torquier. And the S-10 could be had with a pretty twisty V6, so there's heavier-duty drivetrain gear to have on this thing, no problem.

Then again, you live in Florida, where hills aren't a big issue. You could be well served with the 2.2 if you don't plan on visiting the Smokies or Rockies.

Considering you'd be sleeping close to the fuel tank and the exhaust outlet, your mention of the smell of diesel is a serious concern. It can be hard to seal up an RV. Gotta breathe, right?

I think you could crack 30 with a gas engine.

[UltArc]

I am not saying it's impossible, and by all means I hope you exceed your expectations.

My experience with my Blazer was very reliable, but not very efficient, and over 4k lbs. I imagine being heavier, even with an efficient design, it will be a challenge. I look forward to following.

[ThomCat316]

So.... I had the first reply typed up yesterday, but things were so hectic that I didn't notice I hadn't sent it. Therefor, it's all gonna be in one post:

JRMichler:
That's pretty much what I'm planning, except....

Move the rear wheels back about four feet.
Get rid of the bed.
Make a replacement "bed" that starts out at the section of the cab and follows the "template" as closely as is reasonable to a small low oval truncated tail.

Overall length from the cab back of ca. 8-9 ft. - small "real RV" length and wheelbase, just in a smaller cross-section. I've also been thinking that a 4-door Blazer/Jimmy body might make a nice starting point - cut it off behind the rear doors and make a steel/composite full-length uni-box rather than a separate bed replacement.

UltArc:
I'm already past 30MPG with the naked, stock truck - heck, I get 24-26MPG towing my 5'x12' teardrop trailer. I know there's going to be an increase in surface (not frontal) area, but I think I can make up for it by carefully designing the cab-back section to have no areas of detached flow. As for weight, I know how to build light. I don't think I'll be exceeding the weight of the bed (to be deleted) by more than 250 lbs., maybe even as little as 200.

SportyModder:
Thanks for the good read! I really loved the link to the NASA "build-a-box" paper - really eye-opening! What I really want is a Vixen TD, but I can do this for about $10-15K less, and I don't have the spare money.

JRMichler & elhigh:
I think I'm going to keep it entirely a hard shell, perhaps with an opening hatch in the back for the galley. I've already built a nice 5'x12' teardrop trailer in fiberglass and epoxy over honeycomb, and that came out at 345 lbs. - I'm thinking I'll weld up a framework for this that will include the bed mounts, bolt some forms into it, build it over the forms as either top & bottom or right & left parts, remove the forms, and bond the parts together and to the shell frame. I'll also likely use compliant mounts between the shell and the truck frame to keep stress to a minimum.

So, after all these words, it's all still vaporware. I just wanted to bounce the engine question off those more experienced than I. I have also read some other forums, and I don't think there's a strongly compelling argument to put a diesel into this thing. I do think I'll plan on putting a custom gas tank in it, though, because stopping for gas every two days is somehow appealing...

Thanks to everyone!

[cRiPpLe_rOoStEr]

It would worth to take a look at those Kubota V2203 engines, which can be had for relatively cheap and can still perform decently with some mild tuning. But since you're in Florida, I'd rather advice you to try to get some Isuzu 4J-series engine.

Or if you would rather want a gasser, a Vortec 5300 (or even a 4800) would still be more suitable than the 2.2L 4-pot. I wouldn't consider any naturally-aspirated gasser below 2.8L to be so suitable for your project, but if you wanna go with a 4-cylinder engine I could tell you to consider either turbocharge the engine or to try a Miller cycle setup with a supercharger and a regrinded cam to get a longer intake timing.

[Sporty Modder]

I agree w Cripple Rooster, a v8 with cylinder bank deactivation. Thinking an cad northstar or something similar small displacement v8.
Another option would be a turbo 4cyl. Nissan sr20det is the first that comes to mind. Aluminum block, very durable, 200, hp and I 225 lbft tq(iirc) for the early ones and 250 hp for the later.