94 Caprice Wagon 5.7L project--46 MPG so far

[oldtamiyaphile]

Love the project

I've always thought a big V8 can still hit great number with EOC, and I just picked up my own V8 project truck.

Regarding hypermiling and towing, I have the same issue, I do a lot of towing and towing in city traffic, so the ratio choice is always a big compromise. So, I've been thinking about sourcing a two speed (external overdrive) diff like was popular with British cars in the 60's-70's. Most often these could only be engaged in 3rd and 4th, but I don't see why that couldn't be modded out. Two speed diffs these days are still around in some smaller trucks like the Iveco Daily, which might be too big for your use, and the ratios might not suit, but it would be a lot easier than swapping diffs every time you want to tow something.

The other thing I'm going to to is build a much lighter trailer

[MetroMPG]

This is a great project!

It's on the front page now.

[elhigh]

It's like seeing an elephant in a hang glider and watching it sail away. 40+ in a Caprice is just so far outside what anyone would believe possible.

[Xist]

How about 50 MPG in a full-sized truck?

[roflwaffle]

The only thing I can think of adding is a L99 with AFM.

[Frank Lee]

Don't get me wrong, I find the results believable and awesome, but I'm just thinking: if all the V8 is ever- or mostly- called upon to do is putter around at sub-1000 rpm speeds, it is generating very little hp and torque down there and those hp and torque requirements could easily be handled by a smaller, lighter engine that doesn't have to be shut off and coddled as much. Could a six or even a four move that wagon around with the same acceleration rates and cruising speeds? A Suzuki G10 probably could!

Also I believe there's an optimum operating speed range for engines as witnessed by BSFC charts and if operating below optimum rpms some efficiency is being compromised by relatively more heat loss to the cooling system. But I suppose that mainly counts at steady and/or prolonged operations at certain rpms, not simply pulsing up to speed.

[funkhoss]

Originally Posted by oldtamiyaphile

Regarding hypermiling and towing, I have the same issue, I do a lot of towing and towing in city traffic, so the ratio choice is always a big compromise. So, I've been thinking about sourcing a two speed (external overdrive) diff like was popular with British cars in the 60's-70's. Most often these could only be engaged in 3rd and 4th, but I don't see why that couldn't be modded out. Two speed diffs these days are still around in some smaller trucks like the Iveco Daily, which might be too big for your use, and the ratios might not suit, but it would be a lot easier than swapping diffs every time you want to tow something.

Yeah, I've thought long and hard about other options, too--such as a Gear Vendors overdrive, a 4WD transfer case with the "transfer" part cut off, or a "Quick Change" rear end out of a race car or hot rod. All three of those options would allow for an easily accessible wider range of gearing. But any one of them would increase the time and expense of the project considerably, and also add a significant amount of extra weight and parasitic drag.

I don't tow that often, so to me the interchangeable axle idea seemed like the best compromise--minimum cost, with maximum efficiency and/or maximum grunt/durability depending on what's needed. But who knows...maybe I'll change my mind in a year or two.

[funkhoss]

Originally Posted by roflwaffle

The only thing I can think of adding is a L99 with AFM.

I actually have a 4.3L L99 V8 (with only 40,000 miles) sitting in my shed right now. It would bolt/plug in without any modifications.

I don't think I'm going to swap it, though. If I didn't use the kill switch, it might make a difference, since it uses less fuel at idle. But I never idle, and I can keep the LT1 in roughly the same BSFC range as the L99 by just shifting sooner and keeping the RPM lower.

[funkhoss]

Originally Posted by Frank Lee

Don't get me wrong, I find the results believable and awesome, but I'm just thinking: if all the V8 is ever- or mostly- called upon to do is putter around at sub-1000 rpm speeds, it is generating very little hp and torque down there and those hp and torque requirements could easily be handled by a smaller, lighter engine that doesn't have to be shut off and coddled as much. Could a six or even a four move that wagon around with the same acceleration rates and cruising speeds? A Suzuki G10 probably could!

Most certainly, a smaller, more modern engine would do the job (of passenger transport, at least), and probably be somewhat more efficient, too. But I would lose the ability to tow 7,000 lbs if I needed to, and it would make the project much more complicated and expensive. And I doubt there are very many other engines that could go 500,000 miles before needing a rebuild (as LT1's often do).

If I do any major engine mods, it will probably be one of two things. Either I'll convert it to run on wood gas using the LT1, or do a (bio) diesel swap. A 6.2 would be the easiest, but one of the new 2.8L Duramax engines would be both more powerful and more efficient. I'll have to wait a while until they're available cheaply in junkyards, though.

[M_a_t_t]

I have a 95 Astro and after reading your story I was looking at specs on your car (stock) and we have, or had, the same wieght, transmission (4L60E), engine, almost, I have 4.3 v6 yours had a 4.3 v8 option, and same towing rating. I wanted to just be able to get 30 mpg highway. I think with our vehicles being fairly similar and you getting 43-46 mpg I should be able to hit 30 with mine, despite it being less aerodynamic. Im planning on doing aeromods though. I would like to do a manual swap but that'd be a long ways away.
Matt