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  1. #1
    Silver Member
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    Sep 2004
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    107
    Location
    KY
    Tractor
    2004 Kubota L3130hst

    Default turbo 3 vs. natural 4 cylinder price/performance?

    As tremendously helpful as this forum has been, I have searched "turbo" in this forum and not found a thread about this (but suspect it is out there somewhere). I drove a 50hp turbo 3 cylinder for the first time this week, and hadn't considered buying one prior to this. And now my mind is muddled. More so than usual anyway!

    In the 45-55hp range, what are the advantages and disadvantages of a 3 cylinder turbo versus a 4 cylinder naturally aspirated?

    1) Is one better suited for one type of task than the other (i.e., one better for stop-and-go heavy loader work, bush-hogging, tilling, etc.)

    2) Is natural more fuel efficient than turbo?

    3) Is maximum torque available at lower rpms with turbo? (or hp/torque ratio different with turbo)

    4) Is durability compromised or long term maintenance higher with turbo?

    5) What kind of price differential would seem appropriate, all other things being equal, for the turbo 3 vs. the natural 4 producing similar hp?

    Thinking about operating this ten years from now, I wonder if it isn't better to have a naturally aspirated 4 cylinder than a 3 cylinder turbo producing similar pto hp. Anyone who can weigh in or point to a thread that explains this, it would be greatly appreciated.


  2. #2
    Gold Member ZJ_HR's Avatar
    Join Date
    Oct 2003
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    412
    Location
    Croatia
    Tractor
    '02 Same Argon70 4WD, '81 Store 402 4WD

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    You touch very good topic.
    I had dilemma 3y ago, when we search for tractor. We were looking to replace 20y old 45hp engine tractor with something new, similar size and weight, about 60-65hp. Several tractors came into consideration. Most of them were 3cyl. We narrowed choice to SAME-Lamborghini tractors. Difference between 60 and 70hpengine model was less than 1500$ (150$ per HP), so we decided for more hp, with equal frame size.
    As we have another FIAT based tractor, we look for NH TN too, but, it was 25% more expensive (not worth that difference, IMHO).
    Finally we ended with 3 cyl turbo, air cooled tractor.

    To answer some of your questions:

    1. Turbo engines are better for constant load work, like BH, rotovating etc. They need time to be warmed up, and time before shutting down.
    For occasional work, like loader, natural seems more apropriate.

    2. Natural is less efficient than turbo. Especially at higher power demand. You have one cylinder more, few bearings more...and this add more friction or resistance. And more heat (fuel!!!) to warm up.

    3. Maximum torque depends on engine size, and turbo setup.
    I have torque curves of SAME 3cyl turbo engine 70hp (3liter) and natural 4 cyl 72hp, 4 liter. Max torque is EQUAL (230Nm measured at PTO), at 1400rpm both. Natural seems better at full speed (2350rpm).
    Usefull range is over 1200rpm (turbo starts to fill).
    Turbo engines have bigger torque rise, so, easier handle overloads.

    4. Durability? Hmm, depends on several factors. Turbo engines run more hot, and need better oil (more expensive), and more carefull maintenance. They are more sensitive to cooling (easier to overheat).
    Every tractor, in class you look for (small ag tractor, not a CUT) will last without problems for 5-6000hrs with or without turbo.

    5. Turbo engines less smoke.

    6. Natural aspirated engines is easier to start in cold conditions, as turbo engines have lower compression ratio.

    7. Tractors equipped with 3 cyl turbo engines have shorter wheelbase, and are lighter, compare to natural 4 cyl.

    8. 3cyl engines produce more vibrations, and generally are louder

    Most of manufacturers tend to 3cyl turbo engines in this class. For sure, because of reducing costs. But today materials, oils and technology give us product good or better as before several years.

    I gave you my points of view. Decision is yours, as money you'll spend [img]/forums/images/graemlins/grin.gif[/img]

    Hope, this helps.

  3. #3
    Platinum Member EquipmentJunkie's Avatar
    Join Date
    Oct 2003
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    534
    Location
    SE PA
    Tractor
    Ford 1520

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    Well said, ZJ HR.

  4. #4
    Super Member JerryG's Avatar
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    Apr 2000
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    7,186
    Location
    Northwest Arkansas
    Tractor
    MF 1440-4 PowerShuttle

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    I have owned a pair of tractors that were almost basically the same tractor with the same engine, one naturally aspirated and other turbocharged. If you are really working the tractor, as in using all of the RPM and horsepower available, then the turbo is amazing. Example: cutting heavy thick Bermuda grass that is very tall. Where the natural engine will lug down the turbo engine will not. I have owned turbo engines for a long time in vehicles and now a tractor. I have had no problems with them, but you do need to use better oil and shut down different.

    <font color="blue">8. 3cyl engines produce more vibrations, and generally are louder</font>
    I have a problem with this one, because 3 cylinders are naturally more balanced than 4 cylinders. We have had a very long discussion about that here before, which you can look up. Lots of 4 cylinder engines have to have balance shafts etc to aid in their balance.

  5. #5
    Gold Member ZJ_HR's Avatar
    Join Date
    Oct 2003
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    412
    Location
    Croatia
    Tractor
    '02 Same Argon70 4WD, '81 Store 402 4WD

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    <font color="blue"> 8. 3cyl engines produce more vibrations, and generally are louder
    I have a problem with this one, because 3 cylinders are naturally more balanced than 4 cylinders. We have had a very long discussion about that here before, which you can look up. Lots of 4 cylinder engines have to have balance shafts etc to aid in their balance. </font>

    Agree with you. Lot of 4cyl engines HAVE balance shafts, even we don't know that, so feelable vibrations are less noticeable. That was my point. Thanks, Jerry. [img]/forums/images/graemlins/wink.gif[/img]

  6. #6

    Join Date
    Nov 2003
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    56
    Location
    South Central Kansas
    Tractor
    Kioti DK45C

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    I choose my tractor based on your turbo question. I appears to me that Kioti uses the same engine in both a natural aspiration and a turbo in different size tractors (DK45=2.2L=45HP, DK55=2.2LTurbo=55HP). I do not use my tractor every day and sometimes for months if it does not snow in the winter. I figured a) The same displacement with fewer horses has less engine stress over the years, b) Turbo's are less trouble if used regularly, and c) If size is not a problem, I prefer to buy cubic inches over a turbo ($/HP are generally the same price). Good question!

  7. #7
    Elite Member
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    Jul 2003
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    3,373
    Location
    Goffs Corner, KY
    Tractor
    IH 2444

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    I think given the same HP I would choose a 4 cyl naturally aspirated over a 3 cyl turbo. The main reason would be more reliability, one less expensive part to go bad.

  8. #8
    Super Member JerryG's Avatar
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    Apr 2000
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    7,186
    Location
    Northwest Arkansas
    Tractor
    MF 1440-4 PowerShuttle

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    Well, not exactly. I was trying to get at, for a 4 cylinder to even come close to the same balance as a 3 cylinder they would have to have other modification such as a balance shaft. A 4 cylinder is inherently unbalanced, where as a 3 is inherently balanced. The 3 cylinder also has fewer parts to wear out and or tear up, all in a smaller package.

  9. #9
    Elite Member Kyle_in_Tex's Avatar
    Join Date
    Oct 2002
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    4,245
    Location
    Giddings, Texas
    Tractor
    JD 4310,JD5420

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    I agree with slowrev, 1 less expensive part to deal with.
    We bought the 5420 instead of 5520 JD to not have to deal with the turbo. I know, the turbo is a great thing, torque and all, but as a manufacturing engineer, I like the KISS(Keep it simple/stock stupid) principle personally. We don't do ground engagement plow type work.
    I use the phrase, "a Model T with air conditioning" frequently.

  10. #10
    Gold Member
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    Jul 2004
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    251
    Location
    Sonoma County, CA
    Tractor
    New Holland TC45DA, New Holland TC18

    Default Re: turbo 3 vs. natural 4 cylinder price/performance?

    I don't know how it plays out in practice, but if used in the right way, a turbo charged engine producing the same maximum horsepower and torque as a larger naturally aspirated engine should theoretically deliver increased fuel economy. An example would be trucks that carry their loads at freeway speeds most of the time. Once the mass of the truck and load are up to speed, the horsepower needed to keep it in motion is a fraction of what is necessary to move the truck and load from a static state or maintain speed uphill. Theory suggests that ideal fuel economy can be achieved by utilizing two different sized engines, a large one when the mass must moved from a state of rest or accelerated, and a small one when the mass must merely be kept in motion. If turbocharging a smaller engine can enable it to produce on demand the same horsepower and torque as a larger engine, then there should be particular conditions of use where superior fuel economy (when compared to the larger, naturally aspirated engine) is realized. I say "particular conditions of use" because I know from experience that if the boost provided by the turbo is not used sparingly, the potential fuel economy advantage disappears. In boost mode, the turbocharged engine will suck gas as fast or faster than a larger, naturally aspirated engine producing the same horsepower and torque.

    How might this apply to CUT use? I haven't clue, but someone at JD is probably prepared to make the argument. They could also be trying to generate some saving in the size or weight of the engine itself, but in a CUT, I would think that the savings would be marginal at best and not particularly useful.

    Turbos can fail and are relatively expensive to replace when they do. They don't tolerate deferred maintenance well, and you need to incorporate some additional bells and whistles into the engine just to use them. Why would JD go through the trouble to replicate the power and torque of marginally larger and heavier naturally aspirated engines in its CUTs? One answer could be marketing, pure and simple. Some CUT buyers will gladly pay a little more to say to their neighbor that their tractor is "turbocharged," even if it performs exactly the same as their neighbor's comparably powered, but cheaper, naturally aspirated machine. Second, JD may be achieving cost or distribution advantages from using precisely the same sized engine to deliver different HP outputs. If I am not mistaken, when it comes to displacement, the "different" 4x20s all have precisely the same engine. The differences in rated HP are all due to differences in the turbo set up. To me, that suggests that the bean counters have hooked up with the engineers and decided that turbos are the best way for the company to go, even if it might not deliver a measureable advantage to the consumer.

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