recommend a torque engine for towing and high MPG

[miguelx]

Howdy all. I am currently back to the question that always seems to provide unsatisfactory answers for me. I've decided that maybe I am asking the wrong people so I'll give this forum a try... I am building a 1967 1 ton chevy dually flatbed 2wd truck for towing a gooseneck trailer and can't decide which engine combo to go with. The idea is maximum low speed torque across a low to flat rpm range that pulls and pulls yet still offers decent fuel efficiancy. I realize that this could be relative so I'll add that 6 to 9 mpg is not acceptable. I'll run 4.11 gears and 31 inch tires which should put rpm's at 65 mph at the 3100 rpm mark and with a manual overdrive providing a .73 or so 5th gear should bring this down to a decent 2263 rpm. Hence my desire for a low rpm flat torque curve. Every one wants to tell me their 500 ci Cadillac tow truck gives 18mpg or that their 454 Chevy does even better than that. I've never gotten better than 8 with these kinds of motors. I'll add that I am looking for a FI gasoline or propane fueled motor (as Diesel makes me physically ill to be around, unfortunately). An industrial motor seems best as higher speed cruising is not an issue. Thanks...

 

[GregLocock]

I recommend that you take the engine and transmission out of a Toyota Prius and use that. You will need to add a further final drive ratio.

In the unlikely event that you /need/ more than 70 hp, then:

Please specify what fuel consumption at what speed you need, also exactly the real towing performance that you need (ie weight, grade,speed), and the weight of the truck and the weight of the trailer.

What top speed on the flat do you need?









Cheers

Greg Locock

 

[miguelx]

Yeah, thanks for asking for the clarification. This truck will be an all purpose tow rig. I live in Montana and make the trip out to the coast frequently, seeing three real mountain passes and lots of flat in between. It also will be used for around town driving when not on the highways. The truck I imagine weighs around 6K lbs. and trailering involves everything from a six horse trailer to a much smaller car hauler flatbed (I suppose we can say upwards of of 10K plus gross on the trailer, but also smaller.) The final drive ratio part of your question I maybe didn't understand so will repeat that I'll run 4.11 gears with 31" d. tires. and an overdrive of .73 approximately. Currently my Chevy 350 V8 towing rig I drive very conservatively and hardely push over 65 MPH with 60 more like it because with no overdrive on this truck I am at around 3000 plus rpm. Adding overdrive to this motor doesn't make sense because that takes me out of my powerband. I get around 8 to 10 MPG now and would love to double that or better if possible. The Cummins turbo diesel guys claim MPG in this range but I don't know. Thanks...

 

[gbent]

If this could have been done effectively with gasoline, there wouldn't be so many diesel pickups around.

If you must use gasoline, try to rent or borrow (or a long test drive) a Chevy/GMC with the 8.2 and see how you like it. If it is acceptable, try to find one in a salvage yard. The no load/heavy load, 3 mountain passes/costal driving situation is about the worst possible for a carburated engine. Add in -40F to 100F yearly temperature extremes and it gets even worse.

As for final gearing, try to get the RPM as low as possible and still pull the load. This may require a 6 speed manual, and you may have to "row" the truck for best efficiency.

IMHO, you will spend much money and time searching for a gasoline combo that will, at best, only be as good as a poor factory diesel combination.

 

[miguelx]

Thanks gbent: The no load/heavy load, 3 mountain passes/costal driving situation is about the worst possible for a carburated engine. Add in -40F to 100F yearly temperature extremes and it gets even worse."

I am very handy with the fabrication issues and have no problem converting this older truck to Fuel Injection that is computer controlled -- this should take care of these problems you've brought up, somewhat anyway.

"As for final gearing, try to get the RPM as low as possible and still pull the load. This may require a 6 speed manual, and you may have to "row" the truck for best efficiency."

I have an old Spicer 8138 auxilliary industrial transmission which is essentially an over *and* under drive in one (3 more speeds --under, 1:1, over) this does add the extra gears but means alot more shifting which can be ok if it keeps me in the right range.

I really just don't know which motor to start with -- a test drive is always a good start although I was thinking of something more interesting like turbocharging a Ford IL 6 300 ci with boost in the 6 to 8 lbs range. Any turbo guys out there?

Also, as a last resort how can I make that Cummins diesel near complete burn so as to reduce particulates, tailpipe chemistry, etc. I've heard about propane injected enhanced burn -- anybody done this? They claim better burn and more power.

Thanks again!

 

[unclesyd]

There was a show on The Speed Channel (US) ,Two Guys Garage, recently where they installed an injector for Propane into the manifold of a V8 diesel engine. The system came as a bolt on kit. I wasn't paying much attention until they claimed (?125?) increase in horsepower, dunamometer, and other good stuff.
There is plenty info on the web.

Improving performance:

Checkout the last post by optimum:

Thread71-108825

http://www.sturmanindustries.com/main/index.htm

 

[bobqzzi04]

I would think the hot set-up would be the "new" Chevy LS1/LS6. They are available up to 6.0 liters and are plentiful in junkyards. They are a nice modern update of the smallblock-fuel injected with efficient ports and chambers. One might do in normally aspirated form. If you feel you need more power then there are multiplicity of forced induction kits available. Of course, you won;t get 16mpg towing with this engine, as others have stated, diesel is the way to go for that.

 

[ctmtwilliams]

Just saw a TV show on MSD's propane injection system, the web site is:

http://msdignition.com/2005/2005_13.htm.

They were claiming 75 hp average increase! "Nitrous for your diesel without the dangers" was the comment, I think. I have no idea what sort of milage you get for a gallon of propane "boost" so I'm not sure how cost effective it is.

 

[optimum]

What do you mean by "as Diesel makes me physically ill to be around, unfortunately"?? You should not smell it in your cab. Go to full service stations and avoid standing behind it.

You are asking for something tha can not be done with gasoline. You want to turbo charge a 300 six? Can we say EGTS!!!! If you are interested in fuel mileage you need a diesel. The bigger the better. Gear the truck down to 2.50's-2.73's and atleast a 6 speed manual. I would go up to a 33-35 tire if you can get them to fit. I would go with a C7 Cat. RPM is directly proportional to fuel mileage. By installing a large diesel you can run down the road at 1400 and return excellent mileage. The idea is to 'lug' the heck out of it. The engine will pull all the gear you can stuff in it. If that scares you too much drop a cummins 5.9, 7.3-6.0 Power Stroke or the 6.5 GM diesel.
If you must go with gas, dont be concerned with mileage but I would build a stroker BB chevy. 500 Cubes, 10:1 flat tops aluminum heads with air flow optimized for idle to 3500 rpms. A cam with fast opening rates and as little overlap as possible. You will have an engine capable of pulling a steep gear will not melting the exhaust off of it. It will be more efficient because it will run close to idle.

 

[miguelx]

Thanks Optimum.

Oh well, I wish it were that simple. What I mean by "physically ill" is that I am chemically sensitive to Diesel fuel and the exhaust these motors make. Simple. I trailer my horse trailer and other trailers often. I get in and out of my cab back and forth to locate hitches and balls and chains, making sure the lights work and all that is related to hooking up a trailer, loading and unloading a trailer. Guess what? With little imagination I think you can see that one stands in a cloud of exhaust fumes before long. Also if one hasn't figured it out I work on my own rigs. Diesel fuel, again, makes me ill to be around. Soaks into the skin and clothing and shop floor etc. I DO wish it were that simple. Oh yeah, self service stations in Two Dot, Montana? Right. Anyway. I am curious what you ment by "EGTS" in regards to a turbo charged 300 six? I have read more than a few articles on propane powered turbo aplications of low reving truck motors that are normally gasoline carbeurater aspirated. Unfortunately these are articles and not technically constructive. Keep in mind that propane boasts 106 octane, enters the manifold already fully vaporized and I am talking about low boost at low rpms. Seems like an idea worth contructively and objectively pursuing perhaps. Now, on to your VERY HELPFUL, thank you, diesel power ideas. It does bring me back to diesel though, something this exercise was trying to avoid. Inevitably, that is probably where I will end up it looks like...

PS What do you roughly estimate "Excellent Mileage" to be with your C7 Cat scenario?

 

[patprimmer]

If you seriously want better mileage, and mainly use it empty, try a second car, like a small Honda etc, and only use the truck to tow.

A slightly smaller, lighter, more aerodynamic truck would also help. Look at some Japanese or European designed light to medium turbo diesel trucks if you want good economy while towing 6 horses. Something like a 3 tonne Isuzu springs to mind.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[swall]

Guys--miguelx obviously needs a non diesel solution here.My ex-girlfriend had multiple chemical sensitivities, and it is a real problem. You simply can't be around the substance that causes the sensitivity, which in this case is diesel. Related story--when I lived in North Carolina an acquaintance ran out of gas on his motorcycle. A state trooper stopped to help and took him to get a one gallon can of gas. But on the trip back, the m/c rider had to hold the can of gas out the window, as the state trooper was chemically sensitive to gasoline fumes!

 

[optimum]

EGTS=Exhaust Gas Temperature's
A turbocharged gasoline engine towing will be in boost for long periods of time, in the mountains which will create lots of exhaust temp. Propane is a nice option but you would need dual fuel unless you know where all the propane refill stations are. A big diesel (Used Cat for Example) would get you well into the 20's for mileage unless of course you enjoy the torque to much. Your best bet would be a big gas engine built to be very eff. at low rpm.

 

[evelrod]

You have a problem, allright. $$$$$$--- Easy fix, just go with whatever big block SI engine that suits your fancy and live with the 6 to 9 mpg. You'll not get any better towing anything over a couple tons. A Cummins 5.9 in a 1 ton duelly with a 4.10 final will get you in the neighborhood of 16 to 18 mpg. and the Ford or Chevy a bit less on average. I base my opinions on a bit over one million miles towing race cars, horse trailers, transporters, etc. in the last 50 years!!! Take it for what it's worth. You will need to tow a bunch of miles to amortize the additional cost of going CI anyway!

Oh yes, empty my old 91 Dodge still gets something like 20/21 max and my 454 BBC gets about 12. My son's later Dodge electronic Cummins gets 24+ most of the time---all have 4.10 or4.11 final and same size tires.

Rod

 

[shbazjinkens]

Do you think exiting the exhaust above and behind the cab like a Semi-truck does may help? My father built a diesel truck like this and most of the exhaust clouds well above your head that way.

 

[miguelx]

I've thought of this and it may be a good solution. I have to say though that after reading all the "diesel is the only way to go" postings here I started crawling around some buddies diesel engine compartments simulating "working" on them and the diesel fuel seems to permeate everything. With not very good results concerning my reactivity... These were older rigs though and maybe a newer and tighter motor would help. One good thing about all this deisel talk is that I have learned what I am looking for. Basically a very low reving motor that produces all its torque at the bottom and not the top, with lower numerical rear end gearing to keep the rpms down. This is why BB Chevs have not been kind I believe -- they like to rev to produce thier power. On the other hand, such motors as the 472 Cadillac (upwards of 500 ft lbs torque!)like to cruise at around 2000 rpm and came mostly from the factory with gearing below the 3.08 range. Keep in mind this is with a 5000 lbs vehicle. The Cadillac forums universally claim 13 to 17 mpg (carbed)and the factory literature supports this. And with better cam choices today that have been computer designed even higher is possible. Then let's add computer controlled fuel injection and I think we are on the right track (I think it would be poosible to modify a chevy big block system for this with a new chip burned for the different engine characteristics.) Oh yeah -- then add a manual truck tranny like the NV4500 5 speed (its been done often apparently by the 4x4 crowd) to keep the engine where it wants to be rpm wise. So I think all this diesel talk has been helpful as it got me thinking in the right direction! Even better these motors are still plentiful and are CHEAP (3 to 5 hundred for a used runner) so the experiment won't cost too much to execute. Now the big question is will this motor do the same under HEAVY load? In any event, even if mpg drops under towing loads when *not* towing I can hope for better results it would seem. Any further ideas on this I would love to entertain... Thanks!