3 cylinder vs 4 cylinder debate

[mcfarmall]

There is a reason the industrial gen sets run at 1800 RPM.

The other reason is that the way industrial gensets are wound, you can get 60hZ at 1800 rpm versus 3600 rpm from your single cylinder "screamer" generator. 60 revolutions per second = 3600 revolutions per minute. 60hZ = 60 cycle per second. On your screamer, the voltage cycles one time per second. So if you wind a generator so that the output cycles twice as fast, (two cycles per second) you can run it at half the rpm.

Sorry to stray off-topic.

 

[LouNY]

The other reason is that the way industrial gensets are wound, you can get 60hZ at 1800 rpm versus 3600 rpm from your single cylinder "screamer" generator. 60 revolutions per second = 3600 revolutions per minute. 60hZ = 60 cycle per second. On your screamer, the voltage cycles one time per second. So if you wind a generator so that the output cycles twice as fast, (two cycles per second) you can run it at half the rpm.

Sorry to stray off-topic.

2 pole generator head requires 3600 rpm for 60 Hz power,
4 pole generator head requires 1800 rpm for 60 Hz power,
6 pole generator head requires 1200 rpm for 60 Hz power,
8 pole generator head requires 900 rpm for 60 Hz power,
12 pole generator head requires 600 rpm for 60 Hz power,
I have never seen a 60 Hz generator with more then 12 poles,
many of the older piston driven natural gas generators for power generation were 12 pole on massive stationary engines.

 

[mo1]

The other reason is that the way industrial gensets are wound, you can get 60hZ at 1800 rpm versus 3600 rpm from your single cylinder "screamer" generator. 60 revolutions per second = 3600 revolutions per minute. 60hZ = 60 cycle per second. On your screamer, the voltage cycles one time per second. So if you wind a generator so that the output cycles twice as fast, (two cycles per second) you can run it at half the rpm.

Sorry to stray off-topic.

That is not correct.

First, the synchronous speed of a motor is RPM = (60*Hz)/(number of poles/2) as LouNY's table shows.

Secondly, you have the concept of AC frequency and number of poles in a generator confused. AC at two cycles per second = 120 cycles per minute (120 Hz.) You would get 120 Hz by driving the generator head at twice the speed listed in Lou's table, so if you had an 1800 RPM engine, you would use it to drive an 8 pole head instead of a 4 pole head OR take the four pole head and increase the engine speed from 1800 to 3600 RPM. Things like this were done "back in the day" to run certain high-speed motorized equipment using AC induction motors; I have an old direct drive wood shaper with a two-pole motor designed to run at 120 Hz off of a motor-generator frequency changer to give a nominal 7200 rpm spindle speed. The motor-generator set had a four-pole 1800 rpm motor driving an 8-pole wound-rotor motor to give 120 Hz.

Third, 3600 rpm is a common speed for industrial spark-ignition (gasoline/natural gas/propane) engines, not just smaller single-cylinder ones as gasoline engines' powerbands are typically much higher than 1800 rpm. Generac uses Ford's 6.8 L V10 in many of its LPG/natural gas gen sets and this engine is rated to run at 3600 rpm. (Ford LSG875 & WSG1068 460 and 6.8 liter engines for dry fuel applications from Powertech Engines Inc.)

Fourth, the generator head may very well run at a different RPM than the engine driving it due to speed-change gears being present between the engine and the generator head. This includes pretty much every PTO generator made.

 

[Texasmark]

The sales brochure I got with my 3910 has a blerb from Ford about why they build their engines in that HP range with 3 low RPM (1800 PTO), either square, or over square engines vs old school diesels that had lots of cubes, long stroke, and low RPMs. Ford talks about piston speeds per rpm and flaunts the fact that theirs is low, reducing friction. 3 cyl is half a 6 cyl one of the most naturally balanced, smooth running engines (Ford flaunts the fact that their 3s don't have a crankshaft counter balance as a result) in use....just check out how many on and off the road large machines use 6 cylinder engines. My 3 Fords are extremely fuel efficient......but not as fuel efficient as my Newer Bransons with the Cummins licensed A1100 and B3.3NA engines. The 6530 run (per data sheet) 0.046 gallon per HP (being used at the time) per hour. My 3910 is close at 0.065 best I can measure and the 3000 is close behind. Never tested the 2000....figured it was a wast of time.....refueling is so seldom you forget where to find the fuel cap....well, almost. Grin.

 

[5030]

Interesting. I never knew that. Why is that? It's actually worse than that. They run at 3600 to make 60 hz.

Depends entirely on how many poles the generator head has. a 2 pole head to make 60hz has to turn at 3600 rpm. A 4 pole head, 1800 rpm. My standby diesel is a 4 pole with a JD turbo diesel, 1800 rpm.

 

[5030]

While on the subject of 3 or 4 cylinder diesels, Kubota made a 2 cylinder sub cut at one time... It was a shaker.

 

[Egon]

So I have been doing research on 3 cylinder vs 4 cylinder Diesel engines.

Has anyone actually tested if a 3 cylinder is more fuel efficient? Or tested which one is smoother, quieter etc?

For example I have a Mahindra 5555 with a 2.7L 3 cylinder engine (55hp) I believe it痴 same engine in 5570 (70hp). A friend has a LS 6168 with a 2.5L 4 cylinder engine (68hp).

It got me thinking which one was best. Not a tractor to tractor comparison but 3 cylinder to 4 cylinder comparison.

Note* (fun fact) my 3 cylinder rated 540 PTO RPM is 2059 engine RPM while the LS is 2500 engine RPM.

I have browsed and read a lot on this subject from multiple forums but most info seems to be opinion not factual testing.

It all depends on the engine design regardless of the number of cylinders. They can all be made to be well balanced. Fuel efficiency is again dependent on the design Of the systems involved and the situation used in.

There is no better or worse based on the number of cylinders.

 

[MHarryE]

When designing for Tier 4, a challenge was holding down costs. Improvements like common rail injection, variable geometry turbos, after treatments to control pollutants enabled us to downsize from a 6 to a 4 in the most popular model for which I was in charge. Same bore diameter, same stroke resulted in reduced swept area, reduced friction. When I moved to the division in 1989 one of the first projects was putting that 4 into a machine, 107 Max HP rating. Same 4, with tweaks like larger bearing journals and everything else beefed up, same engine had ratings up to 225 HP. Reducing cylinders does reduce parasitic losses; however, there are a lot of other parameters to consider. The 3 cylinder in my mini-excavator needs to be running around 1400 rpm before it smooths out. We had that same problem putting the same 3 into a small asphalt compactor but nothing compared to the 2 cylinder Hatz diesel the 3 replaced.

 

[mcfarmall]

That is not correct.

First, the synchronous speed of a motor is RPM = (60*Hz)/(number of poles/2) as LouNY's table shows.

Secondly, you have the concept of AC frequency and number of poles in a generator confused. AC at two cycles per second = 120 cycles per minute (120 Hz.) You would get 120 Hz by driving the generator head at twice the speed listed in Lou's table, so if you had an 1800 RPM engine, you would use it to drive an 8 pole head instead of a 4 pole head OR take the four pole head and increase the engine speed from 1800 to 3600 RPM. Things like this were done "back in the day" to run certain high-speed motorized equipment using AC induction motors; I have an old direct drive wood shaper with a two-pole motor designed to run at 120 Hz off of a motor-generator frequency changer to give a nominal 7200 rpm spindle speed. The motor-generator set had a four-pole 1800 rpm motor driving an 8-pole wound-rotor motor to give 120 Hz.

Third, 3600 rpm is a common speed for industrial spark-ignition (gasoline/natural gas/propane) engines, not just smaller single-cylinder ones as gasoline engines' powerbands are typically much higher than 1800 rpm. Generac uses Ford's 6.8 L V10 in many of its LPG/natural gas gen sets and this engine is rated to run at 3600 rpm. (Ford LSG875 & WSG1068 460 and 6.8 liter engines for dry fuel applications from Powertech Engines Inc.)

Fourth, the generator head may very well run at a different RPM than the engine driving it due to speed-change gears being present between the engine and the generator head. This includes pretty much every PTO generator made.

I thought hZ was cycles per second (1hZ=1 cycle per second, 60 hZ=60 cycles per second and so on) at least that's what I found on the internet. AC at 2 cycles per second would be 2hZ. At any rate, I have a meter that plugs into my wall at home and it reads 60hZ all the time. I would think that if the sine wave of AC changed 60 times per MINUTE (1 cycle per second), my lights would be flashing. Apologies for straying further off topic!

 

[Industrial Toys]

Actually I found a 1hz flash rate is very attractive when building flashing circuits. lol

 

[ZJ_HR]

You can see two 3-cylinder engines in my avatar.
Smaller one has licensed FIAT engine, known in Long tractors there decades ago, 2,34 litre 45HP@2400rpm,
Bigger one has SAME air cooled engine, 3,0 litre with turbo, 70HP@2350, know there also as AGCO5660 (version without turbo, 60HP).

My conclusion: I'll buy 3-cyl FIAT engine again, as it is smooth running, quiet, no vibration, very explosive engine, like run even to 2600rpm .
SAME engine has big vibrations (feel on steering wheel, especially under 1500rpm), high noise (even on liquid cooled engine version) with rattle sound, high peak torque, but low torque at nominal speed, and hate high rpm (over 2200). I'm regretting that I didn't buy 4-cyl version (4 litre).
So, it's up to the engine construction.

Today, Fendt produces 200 series tractors from 80-115HP engine with 3-cylinder 3,3 litre engine... In a old days 89...90HP was border to 4/6-cyl engine...
Bigger frame, Fendt 300 series , has 4-cylinder 4,4 litre engine in equal power range.

My 2 cents...

 

[Texasmark]

My 2000 is 4 cyl and 3000 is 3 cyl. putting out around 35 and 40 hp respectively. The 4 is quieter and smoother, hands down. That 3 is a smooth running (relatively speaking) slightly higher hp than the 4, and is quiet with minor vibrations. The 3910 upping the hp by 10, is a different block casting, seems to have much more casting braces added, and the only difference is the diameter of the piston moved from 4.2" to 4.4. The 2000 is "under square" (bore-stroke), the 3000 square, and the 3910 over square. The 3910 is very noisy and high vibrations with only 900 engine hours.....the 2 and 3000 have over 3500 each. Owners of the higher HP 3 cyl fords report on average, noisy engines. I had a 4600 years ago that was 4.4x4.4, 55 or so hp, forget exact amount, and it too was noisy.

The 6530 is 65 hp running PTO at 2600 rpms rather than the 1800 on the Fords, is 4 cyl, a Cummins design, License mfgred., and is smooth as silk and quiet. The little 2400 is swirl chamber 3 and sounds funny due to the swirl induction but it's smooth and quiet at 3 cyl, also a Cummins licensed engine.

 

[BrokeFarmerJohn]

My Mahindra 5555 is 3 cylinder and boy does it start easy in the cold weather.

Starts much easier than my “old” 2005 JD 4320 did.

 

[oosik]

I'm retired and have a better solution. When it's really cold outside - I stay inside. Yes my M6040 starts easily in really cold wx. But just the thought of laying my buns on that frozen vinyl seat - I'm having another cup of coffee.

Do I ever worry about the fuel consumption on my M6040 - H*LL NO. I'm a whole lot more concerned about getting the job completed.

Leave fuel consumption worries and tire slippage worries to the real farmers. These are worries that affect their bottom line .............

 

[3gunr]

I have 2 three cyl tractors and 1 four cyl . They all start easy but the 4 cyl is much quieter a smoother running . It does burn more fuel , but it is a hydro compared to gear. I dont think the number of cyl would affect my buying decision though.