Thread: Why diesel?

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    Default Why diesel?

    I volunteer from time-to-time to crew an ambulance. A bystander asked me the other day why our ambulances ran on diesel. And indeed, our rigs have turbo-charged diesel engines. I have to admit, the guy had me. I have no idea why diesel versus regular gasoline, and now I'm curious. Our ambulance is just a big van (a type II, I believe it is called). Other than perhaps the cost of the fuel, is there some advantage to running diesel over gasoline?

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    Diesels are more efficient (better MPG), their overall operation is somewhat simpler than conventional gas engines (easier to repair, less to break), and they are far more durable and longer lasting.

    Both of my personal vehicles are Diesel, for these and other reasons.
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    I am not much for the motors, but I have been under the impression that Diesel engines are better for idling.

    mechanics , is this accurate ?
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    Prolonged idling is considered severe duty for any engine, requiring shorter oil change intervals. Diesels superior low speed torque (twisting power) makes them the choice for heavy vehicles. Because of a Diesels much higher initial cost you must run them continually to see any fuel savings on a lightweight vehicle. Fordís Diesel option adds $5,300 to an F250. Diesels also last longer. However, todayís gas engines are routinely going 200,000 miles. Diesel fuel is much less volatile & therefore safer than gas. As for being easer to repair. It used to be any shade tree mechanic could get your gas engine going, but if you had a Diesel you were stuck. Todayís engines Diesel or gas because of the electronics, all require special training & tools.

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    I remember the days when the Ford rescues had the 460 gas engines you could never keep cool or running. The advent of the diesel increased reliability many times over. The diesel just makes more sense for reliability due to the nature of the operation and yes they will idle for long periods with far less problems than gas. Technologically we still have a ways to go in the development of the diesel to effectively perform at a proficient level on alternative fuels such as CNG, bio-fuel etc. but no doubt it will happen.

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    Jonathan,

    The main reason ambulances have diesel engines is because of insurance claims. Diesels put less deadly exhaust into the box if there is an exhaust system leak and diesel fuel does not explode like gasoline in an accident.

    A Ford chassis with an ambulance package is only available with a diesel engine. The same chassis with a heavy duty towing package, instead of the ambulance package, is available with a gasoline engine.

    Brad

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    Wrench is right on with this, I ran in the day of gas engines, milage was terrible, but they were fast. They did not last engines would blow up on calls. At a 100000 miles they were junk.

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    Quote Originally Posted by sklump
    Wrench is right on with this, I ran in the day of gas engines, milage was terrible, but they were fast. They did not last engines would blow up on calls. At a 100000 miles they were junk.
    ditto skump.............Brad .........I dont think thats the correct answer but a good guess.
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    At one time Ford had a major problem with gasoline powered ambulances catching fire. I don't know if they ever determined the cause. But Ford made a corporate decision to only provide diesel engines with their ambulance prep package. After that, Ford QVM (Qualified Vehicle Modifier) builders were not allowed to build ambulances on Ford chassis with gas engines. To the best of my knowledge, that's still the case.

    Stay safe out there, everyone goes home!

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    Simply because Ford had a problem with their gas rigs didn't and shouldn't make diesels a standard. You could still get gas ambulances...and perhaps still can...just not a Ford. Chevy offered 454 3500's and 3500HD's with Type I boxes well into the 90's. Dodge was used for the occasional Type III ambulances with the 360 Magnum.

    The expense of a diesel cannot be paid with fuel savings unless you run 300,000 miles. Even then the savings is cents per gallon.

    On our recent 2004 squad purchase...we went with an F550 4x4 V10. Ford Truck Body Builder Advisory Service (Fords truck division for commercial vehilces) approved our use in writing as long as we didn't install a high idle kicker or transport patients. Again...this is their thing and not an industry standard. High idlers are Ford OK on every other vocation...just not rescue type. This is due to THEIR history and experience...and lawsuits.

    The V10 saved tons of cash, has tremendous power and speed, and isn't bad on fuel at all. Its better suited for quick medical calls around the city and warms up much quicker to operating temps. Its a heavy duty design that sees 300K to 400K miles of service in other types of uses. Power companies here use them and run them for 8-10 hours solid day in and day out.

    A typical truck for light rescue will never utilize a diesel to its ratings. Letting them idle for extendended periods kills them too. No modern diesel manufacturer recommends prolonged idles. With todays modern fuel injection and computer controls...unlike the 460 Big Blocks of yesterdays ambulances...gas engines are more viable than ever.

    All we did was install a 200 amp alternator (and associated wiring upgrades) and a follow the remainder of Fords recommended upfitting practices. Its a great truck, its quiet, doesn't stink like diesel...and I will never ever own a 6.0 powerstroke engine. They are trouble, have a terrible history of trouble, and if you think repairing a Powerstroke is easier than a modular V10...go pop the hood on one.

    For big rigs...there is no other option than diesel...nor should there be with the weights and sizes. However one could get by with a GMC 7500 basic 1000 GPM pumper along with a V8 8.1L gasser. Its definately got the power and torque.
    Last edited by fpvfd502; 08-28-2006 at 04:40 PM.
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    Diesels are more efficient, last longer and can idle for extended periods of time with no problems. They also produce more HP and torque than gasoline engines

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    As far as efficiency goes...one would have to really do a comparison of oil equivalents as it takes about 20% more crude to make a gallon of diesel than a gallon of unleaded gasoline. Diesel costs more nowadays. And the maintenance costs are definately higher.

    I've witnessed V10's go over 300K and still run perfectly. I've seen PowerStrokes give up below 200K. Of course...in general diesels can last longer since they are built "heavier". Duramax and PowerStroke's are considered light-heavy duty engines whereas a Cummins ISB 5.9 is EPA labeled as a medium-heavy duty for example. Not all diesels are truely "heavy duty". Look at the connecting rods in PSD's...you'll see what I'm talking about.

    Diesels can not idle for extended periods of time without any problems. Cummins recommends against this since a diesel cools when idling. The oil temperature can drop below operating ranges which can lead to buildup on valve stems and guides. Eventually the buildup can seize them and you'll end up with a bent valve and serious damage. They put that in writing. So do other diesel builders for various reasons. With todays higher emission standards...extended idling does have consequences.

    Todays computer controlled gasoline engines can idle all day without problems as well as any modern diesel. Look at taxis and cop cars. But I have yet to see the day in 10 years of fire fighting where any engine we have HAD to idle all day. I doubt I'd allow it anyway and find other ways to block roads etc.

    While todays diesels out torque gassers...they are still both big numbers and still comparable for the job at hand.

    For horsepower...2007 Ford 6.8L V10 = 362HP. The 2007 Ford 6.0L V8 Diesel = 325HP. Thus the gasser has more horsepower in this comparison.

    Ambulances used to get by OK with non-turbo 6.9L and 7.3L International Diesels with weak HP and torque ratings by todays standards. Todays gas engines make diesels of even a few years old look bad.

    A 2000 Cummins ISB 5.9L Turbo had 235HP and 400 ft-lbs torque. A new 8.1L GM V8 has 325HP and 450 ft-lbs of torque. So the numbers are not all that different.

    I'm a diesel fan as I own a Dodge Cummins truck. But don't get me wrong. I'm not saying everyone should switch to gas engine vehicles. I'm simply saying one could if they wanted to. Thats my belief.
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    I certainly can understand why you bought a gas engine and I am sure as diesels get more and more expensive there will be more gas engines in use on medium trucks, but there is really no way around the incredible underhood temperatures a gas engine will produce. Rubber and plastic parts and wire insulation under the hood will start disintegrating on a vehicle that is driven slowly or stationary more than it is operated at highway speeds.

    Also how did you arrive at the conclusion that the gas engine would have to run 300,000 before paying for itself? My last calculation on this (on a pickup no less) indicated it would take less than 100,000, which we will definitely run it. Around here diesel varies seasonally, from cheaper than regular unleaded to about the same as premium, about even as far as time is concerned.

    Birken

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    Of course it has been a couple years since I ran this calculation and fuel prices and diesel option prices have varied. From memory, 300K seemed like the number which was ran on a diesel pickup forum I belong to.

    But lets look at today for kicks. Gas here = 2.75 per gallon. Diesel on Saturday was $3.10. I've seen diesel as high as $3.30 or more.

    On our F550 cab/chassis the V10 was standard with "N/C" on the 4-speed automatic while the Powerstroke 6.0L was a $6440 upcharge including the automatic 5-speed Torqshift The V10 can get 13-14mpg more or less and the 6.0L can get 17-18mpg more or less. My buddies who claim over 20 in a big SuperDuty 4x4 Powerstroke are grasping at straws. This is empty highway driving. The diesel will do better than the V10 pulling a load...but our load isn't a 15,000 lb trailer either.

    (2.75x/14mpg) - (3.10x/18mpg) = $6440.

    "x" therefore equals 268,333 miles. That isn't 300K I know...but I don't remember the variables a while ago. Rounds to 300K.

    Basically in 268,000 miles...the gasser will consume 19142 gallons at $2.75/gallon for a total of $52,642 spent at the pump.

    The diesel in 268,000 miles will consume 14,889 gallons at $3.10/gallon for a total of $46,155 spent at the pump.

    $52,642 - $46,155 = $6,487 saved in fuel (which pays for the diesel option).

    Plus I factored in the higher maintenance costs of the diesel too. Price an oil change and fuel filter change at Ford and you'll notice the difference.

    On top of that...who knows where the actual break even occurs when you factor in the unreliable 6.0L engine which is plagued with major problems. When warranty runs out...the costs to repair will be astronomical. We just got our first 6.0L ambulances. The other 6.0L squad SuperDutys don't have the miles to have problems just yet.

    I'm not trying to justify gas for the emergency services. This calculation was for one particular truck which served a very specific purpose on our department...to make medical calls in city with the ambulance...then return home...all within 25 minutes. The calculation was something I did on my own when considering a diesel for myself.
    Last edited by fpvfd502; 08-29-2006 at 04:39 PM.
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    [QUOTE=fpvfd502]Diesels can not idle for extended periods of time without any problems. Cummins recommends against this since a diesel cools when idling. The oil temperature can drop below operating ranges which can lead to buildup on valve stems and guides. Eventually the buildup can seize them and you'll end up with a bent valve and serious damage. They put that in writing. So do other diesel builders for various reasons. With todays higher emission standards...extended idling does have consequences.QUOTE]

    That is why it is recommended to idle them up to 1000 rpm or so when they will be idling for a while. I drive a truck for a living and it runs nonstop for days at a time....Thousands of hours idling and not one problem. Take that times the millions of trucks running around and thats alot of hours of idling for a diesel engine

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    Default hi-idle

    Our rescues with the Cummins engines all have an automatic hi-idle feature when they are placed into neutral with the park brake on. It just makes sense for both the engine and with all the electrical items and a/c turned on.In fact all of our rescues, even back to the gas days, had hi-idle features. Anybody remember the Vortec systems and then the Ford programmable hi-idle systems? I still want diesel.

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    People will buy trucks and do with them whatever they want to. Either they hold up or they don't. I read Fleet Manager magazine and the industry trend of large truck fleets is to reduce and/or eliminate extended idling as its proven to waste fuel and may harm the engine in the long run. It is discussed all the time in these publications. Fleet managers see big dollars being wasted in those millions of trucks idling and potentially causing higher maintenance costs later on. Whether or not folks do that is up to the individual or company policy. If you have a need to idle...then thats fine. I am simply just repeating what manufacturers have put in writing. Our trucks sometimes end up idling for longer than they should. But I don't let it worry me.

    Ford puts it in writing not to idle the PowerStroke for more than "X" many minutes. Cummins does the same...as does other companies. Most modern diesels run so much more efficient and pump so much cool air into the heads...they can be harmed by extended idling. Its their words...not mine. I just try and follow their suggestions to avoid warranty problems later.

    In speaking of idling...I wasn't talking of increased idle speeds. I was refering to low idle. Our trucks with the exception of the V10 have high idle switches for when sitting in cold weather or when its known they must be kept running. Thats a different story. They will run at 1200 rpm to keep temps up and systems charged.

    Some trucks are going with compact diesel generators on-board to keep the main engine coolant warm for heat, and to keep the electrical system of the truck functional for laptops, fridges, A/C etc. They claim they will pay for themselves.

    But this is really off topic for the question of why diesels in fire/ambulance applications. Totally different needs and job description. A lot of big trucks can get by with low idle for durations because they will heat way up on the highway for many hours to burn off carbon etc. Some fire apparatus won't see hours of use on a daily basis and suffer more.

    Again...don't take me wrong. I'm not advocating a V8 Gas engine in a 100' tower ladder. Pumpers deserve diesels. I'm just thinking its possible to go gas in an ambulance or light rescue...or chief truck etc without severe consequences these days. If you look at the Freightliner Sprinter vans...you don't need all that much horsepower to make a decent sized ambulance go down the road well.

    We gotta keep in mind the original question of the bystander asking about ambulances specifically and why the need for a diesel in this specific application. Ford got away from gas busses in the 80's. There have been major improvements in gas engines since.

    As far as less chance for carbon monxide entering a patient compartment...I'd say keep the exhaust inspected. Many a gas van haul around little league teams and the like...and nobody mentions carbon monoxide entering the compartments here. Or family cars or ???
    Last edited by fpvfd502; 08-29-2006 at 07:47 PM.
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    Diesels are still more efficient than gas....any way you cut it. Per gallon of fuel, diesel engines produce more hp and torque than gassers. Also its not the manufacturers that are trying to crush the idling....Its the EPA and tree huggers. It is harder on an engine to start and stop than to idle.

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    Quote Originally Posted by Frmboybuck
    Diesels are still more efficient than gas....any way you cut it. Per gallon of fuel, diesel engines produce more hp and torque than gassers. Also its not the manufacturers that are trying to crush the idling....Its the EPA and tree huggers. It is harder on an engine to start and stop than to idle.
    No it's not. The Slick 50 people were the ones who propagated that fallacy. When an engine is idling it is wearing itself out and burning fuel without any benefit to the owner. Cylinder packs are a lot more expensive than starters and ring gears. Shut it off when you can.

    Old diesels were even worse because of lower operating temperatures and inferior injection systems. Ever seen what a 3208 does after it has idled for half an hour? Could fog the whole freeway. Even the last PLN Cummins engines could get fuel dillution in the lube oil from long idling. I imagine the common rail ones are better. The Powerstrokes don't seem to have any problem with it. But just the same shutting an engine off and restarting doesn't hurt it one bit. The oil remains in the bearings, etc. The oil pressure is not what holds them apart, the residual oil does that just fine, and don't use the dash mounted gauge to tell you that anyway. The engine has oil pressure to the galleries within 1/2 of a revolution, probably before it even fires.

    There, did I miss anything?

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    Well in 735K on my C-12 I have replaced the starter 5 times and never touched the engine besides 1 injector and normal maintance. My 3406 was the same way. I did all the injectors at 750K and never had one problem with the engine. I sold it at 1,200,000 miles and it still ran great. The 3208 was a really bad excuse for an engine anyway. Every one of them smoked like a chiminey.
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    OK, but how did you arrive at the conclusion that it is harder on an engine to shut it off and restart than to idle. Contrary of course to what you find in the basic operator's manual. And have you not seen the fuel dillution in lube oil, upper cylinder wear from fuel washing the lube oil, and valve stem/guide problems that are the most common problem with long idling?

    Birken

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    Default torque

    what is the comparison of torque between a triton v10 and a powerstroke v8? also, will chevy allow the gasser on an ambulance?

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    Powerstroke = 570 @ 2000
    V10 = 457 @3250

    Both numbers are substantial when compared to engines of even a few years ago.

    The Cummins "B-Series" in Dodges used to have 400 ft-lbs for a long time...and that was considered enough to move a house.

    My department once considered purchasing a used 1996 Chevrolet 3500 4x4 Type I ambulance as a support vehicle. It was built by one of the bigger builders...I don't remember which. It had a 454 EFI engine.

    More recently...an area combo department bought a light rescue unit in 2001. It was one of the last Chevy 3500HD's (19.5" wheels) available in the old body style...but was available with the newer 8.1L V8 Gas. They like it.
    Last edited by fpvfd502; 08-31-2006 at 11:14 AM.
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    Maybe to help bring the question to a close (diesel vs. gas discussions in pickup forums have been known to go on forever)...Ford Motor Company only sells their vehicles with the Powerstroke if you want the Amb Prep Pkg. Their legal definition of an ambulance is "a vehicle which transports patients and/or carries life saving equipment similiar to that of an ambulance...and uses a idle kicker device..."

    Ford QVM manuals and Incomplete Unit Body Builders manuals are very very informative and give many details of what Ford expects from upfitters. They do not leave any stone unturned and describe wiring modifications, heat shielding, body mounting, frame alterations etc. Its more than an average person wants to read. I've read them and read the new ones as they come out. There is ALOT of information available from Ford on the web on ambulance topics...and all other vocational topics.

    Since we don't transport and we don't have an idle kicker...Ford had no problems with our use of the V10. They said it would serve our needs well...and it does just that. Our truck in not considered an ambulance. As a side note...they do have a manual on how to install a high idle kicker on gas engine equipped trucks. It will show all the PCM taps required etc. But...not if its a gas engine on an ambulance.

    But with ambulances...Ford has literature why they do not wish to offer a gas ambulance. And if you know Ford ambulance history...you'll know their elevated underhood temperatures in E-Series trucks with gas engines was not a total success. I won't go into their reasoning. Their literature library is very extensive and the information is actually neat.

    Point being...they don't discuss the efficiency of diesel versus gas...nor the horsepower/torque required to move an ambulance. They discuss heat sheilding requirements and fuel systems in general. They wish to only offer diesel platforms in the Prep package for ambulances.

    Thus...the answer to the original question is simple. Ford ambulances do not use gas engines because Ford Motor Company has chosen to only focus on a common platform which they feel comfortable with has a proven track record of not causing them (FoMoCo) problems. They are not going to devote the engineering and time required to develop a gas platform...although possible. Most want diesel anyway...and sales of gas platforms would probably not meet the goals Ford would have. If there was a large demand...they would most likely follow suit. Departments like having one type of fuel for rigs...and the ideology of "diesels are heavy duty engines".

    For us...the $6000 price tag couldn't be justified.

    I think thats the real reason to the original question. Its not because they save so much fuel, have so much more power that both the taxpayers notice a substancial savings and patients get to the hospital faster. Ambulances are junk at 100,000 miles anyway. Your taking a risk pushing them any further do to chassis wear etc.

    Man...I think I'll bow out at this point. Not to offend anyone...its been a great discussion...but I'm tired of typing. And all of this is just my opinion. Maybe Nascar should go diesel. Refuel less and more power??
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    Actually Cummins had a diesel race car in the 1950s. It did very well but DNF for some dumb reason or another. Too bad it did not continue.

    Birken

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