It's on propane, electronically controlled and NEVER going "rich".

It will run always at max fuel economy air fuel ratio, and run higher boost if need be. I understand your concern, but this is not "conventional" in any fashion.

Good answers, every one. The last one about being the coolest kid at the Camp Jellystone trumps all naysayers, as far as I'm concerned.

>>>Remember, fuel consumption per horsepower produced in a gas engine (throttled) requires you use a large percentage of available power. That can be achieved by chugging down the road at 1300 rpm, too, but thre are inherent inefficiencies, mostly thermal, involved in running that slow.

I'm not totally sure about this line of thinking because a: I haven't had a buttload of experience with turbo/blown motors and b: I have very limited knowledge of propane and how it relates to thermal effieciency. Seems like you would be moving an awful lot of the stuff, and that means everything is going to be cold, or at least cold is going to be a different problem than in a gas engine. The turbos should heat things up a bit, but there are a lot of unknowns.

A while back on this site there was a flurry of posts about putting Ford transmissions behind the /6. That might open up some options for you.

I guess the only thing you really can do is build it and hope it works. I'm rooting for the 6, because it's so oddball (as if the poly wasn't oddball enough). I'm getting the vibe from this thread that the poly is basically an orphaned engine, and that will cause you no end of trouble. Parts is parts, but it's nice to be able to get jerky wear parts at Autozone in a pinch.

Regardless, even if you put a 360 in it, this is going to be one cool rig. Have you thought about hardwood floors for the cab?

Kip-on-Truckin'

_________________
1965 Valiant wagon Turbo slant (work in progress)
2000 Chevy 155" cargo van - The Abductor
1970 Newport convertible
1996 Buick Roadmaster Wagon
1966 CruiseAire motor home
1990 Toyota 1 ton box truck TURBO slant (scraped)

Kip, its still my opinion that the 318 poly is one of the best motors ever to come from mother mopar. It's simply just expensive to build. I'm still learning about all of this slant six business. I'm very new to the /6.

6 cylinders has never interested me until recently seeing what crazy things can be done with such a stout motor.

I still think I favor the old Poly though. There are forums sites and tons of die-hard poly fans, just like there are here for the slanter.

I have nothing against the poly engine. This being the third I've owned, I am a huge fan. This is one time, however, I'm making choices based upon predefined parameters.

I think I'll try the stroked poly in a motorhome, if I can find a suitable classic, like a Travco... That would have the auto and closer ratio gears, etc. It would also need the higher horsepower and gobs of torque for the auto to suck up and turn into hot oil...

No. And now that the idea has been considered, no.

In fact, I want to coat the underside, the inside, and then lay down padding and insulation and then carpet over that... for QUIET.

I even want to insulate and soundproof the doors, the ceiling, the firewall, the back wall, the sides... Put foam in everywhere there's a gap, put on sound deadners anywhere it can be done, stop every air leak and make it as warm/cool as possible.

I want a full airbag rear suspension, with nice riding springs in the front, all set up for lots of travel, and then serious sway bars front and back. In other words, a nice ride empty and the ability to stiffen it right up for towing and hauling.

Shag carpeting on everything................

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I thought I'd address what I have found written on the topic, and that is that as you slow the engine rpm down, the expanded air (after the fuel burns) loses more and more percentage of the heat to the piston and cylinder walls, and begins to drop in pressure more than if the piston moved faster. In other words, you lose more heat to the pistons and walls, than if you run it faster.

The balance here, is that there's roughly two slopes... one that slopes forward, with the largest losses at the low rpm side, and one that slopes backward, with the highest losses at high rpm. Best economy is obtained in the valley between these.

Now, it is VERY hard to predict, given what small amount of information I could find, other than theoretical and observed generalized results, exactly where to run one of these engines... All I can do is just use practical rpm ranges, and realize that I'm going to be in the valley somewhere if I simply don't go radically up or down in the rpm range.

Now, of course... If this doesn't work, I can probably swap engines... and that twin turbo sl6 would flat out RIP in some light car...

Interesting. Where did you find BSFC numbers? I was always given to understand that best BSFC occurs at the engine's torque peak. And that BSFC and peak torque are really one and the same thing.

I did a test once with the Toyota, driving 200 miles nonstop in 3rd (1:1) and then a second 200 mile leg (same day, same road) in overdrive. I got substantially better mileage in 4th. Can't say why with any certainty, other than frictional losses should go up linearly with engine speed. On the other hand, maybe it's nominal at speed under,say, 4000 rpm. What you are talking about doing with the turbos, compression, cams, intakes, etc is really just a way of moving the peak torque to where you want it.

But I REALLY like your backup plan mentality. If the worst case scenario unfolds and the engine just doesn't cut it, you can pop that thing in a Valiant and have a great hot rod.

On the other hand, we are not talking about insane amounts of torque needed for your app. Seems do-able to me. Between boost, propane, and the general freshness of the engine it doesn't seem like an impossible goal.

My buddy got all crazy about soundproofing his van. He spent alot of money on that silver backed adhesive stuff that feels like sheets of refrigerator magnets. The results were so-so. I haven't Shutz'd a car in 20 years, but I seem to recall that stuff worked pretty good. Otherwise, I think you are going to have to build a multi-layer custom carpet. And yes: thick purple shag NEVER goes out of style.

Kip-on-Truckin'

p.s. Yours is the coolest build idea I've run across in a long time.

_________________
1965 Valiant wagon Turbo slant (work in progress)
2000 Chevy 155" cargo van - The Abductor
1970 Newport convertible
1996 Buick Roadmaster Wagon
1966 CruiseAire motor home
1990 Toyota 1 ton box truck TURBO slant (scraped)

There is always Lizardskin.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

YES IT DOES! It was never "in" in my estimation

I found lots of theoretical discussion... And I could not find a single chart for car engines anywhere. But I did find some race car engine information and some airplane engine and some industrial engine information, and they all shared common traits...

There's a LOT of research being done to try to figure out how to reduce pumping losses and friction losses, to improve economy. Variable cam timing, variable valve timing, variable stroke engine, variable displacement.... You name it.

The "sweet spot" for the engine appears to be about 40 to 55% of the max horsepower RPM, and then the BSFC drops on each side of that. Most engines are checked at full throttle only. SOME dyno work has been done to establish the actual BSFC for a throttled engine and relate BSFC to percentage of load.

I found only ONE engine's results mapped out, and this engine had a best BSFC at full throttle and about 2100 rpm. But the economy was pretty good up to around 3000, and then it tapered off. It also fell off below 2100. Not badly, but moderately. This particular motor had a "best" around .35, but at 1200 rpm and 25% throttle, it was over 1 - WELL OVER 1. However, it was climbing and it was about half that (the lower number, the better) in the "sweet spot", which was around .7 or so, and that was from 1800 to around 3000. Now please understand, this is not EVERY engine, but every throttled engine will have a somewhat similar curve.

Cam specs, stroke, bore, breathing capability, etc, all change how this works.

A large cammed engine will have low pumping losses, but due to reversion and overlap letting exhaust contaminate the mix, it will still be low on the low end and light throttle.

As far as I can tell, BSFC is maximized where:

1. Best cylinder filling occurs, and is adjusted by:
2. Where the combination of 1 and best breathing occurs, so that exhaust is pushed out, overlap doesn't leave lots of old gasses in the engine.
3. high cylinder pressures
4. lower piston speeds and least frictional drag
5. least exhaust backpressure.

Turbo engines have between 10 and 20% poorer BSFC at full load, because the drive pressure for the turbo causes pumping and friction losses. It takes fuel to drive the gasses out of the chamber and shove them through the turbo nozzle.

So, to minimize that loss, maximize breathing capability, and use the least possible back pressure and boost necessary to achieve the horsepower required.

Thus, this is why I want to use two turbos. I also want to have these turbo wastegates pulled open by intake vacuum. That is, when you close down the throttle, the wastegates open, creating the least exhaust flow resistance. With a draw through turbo, the compressor side wheel has minimal resistance to spinning whle under vacuum, as well, so the turbo will still continue to spin moderately.

Yes, it will increase low speed turbo lag, but that can be disabled easily if you need that done. Also, a draw through turbo has minimal resistance at low throttle. The compressor wheel spins up easily since the lower the air density in it, the less resistance it encounters. Sudden opening of the throttle uses the turbo's inherent momentum to help sharpen the throttle response and then the exhaust's burst of heat and velocity takes over.

The engine will be cammed and otherwise optimized for torque over 1500 and under 3000, and the turbos should not boost much, if at all, under about 1200 to 1400. Likewise, they'll have minimal exhaust restriction, so it will simply have a torque curve that looks like a naturally aspirated /6 until it hits around 1500 or so and then starts upward sharply and continues upward to probably 2500 to 2800 and then falls off slowly to peak horsepower, which I hope to make around 4K.

Porting for velocity, cam timing for early torque, probably by advancing. At first I was leaning towards a wide lobe angle, probably 112 to 114, but since then I've decided that narrow is good, to peak and narrow the torque range down lower.