Turbo Charged Engines - Avoid or Buy?

[SPYDERLK]

Also, and maybe I am wrong here, but I don't think there is much turbo lag on a tractor, afterall you rev the throttle to a paticular RPM, and it stays there. The exhaust pressure is the same while you are driving or not. Might be a slight delay if you hammer the throttle and then the go pedal, but after that it should be constant power.

As far as turbo lag, that's mainly a gas engine problem due to the fact gas engines have a much wider rpm range. I had a toyota with a turbo that red lined at 8,000 rpm. A correctly designed turbo will need to provide the correct CFM. An engine turning high RPM requires a lot of air and a bigger turbo. The exhaust flow at low RPMs is just not powerful enough produce any boost. Some manufactorers have been installing two turbos on gas engines, a small turbo to provide boost at near idle engine speeds and a main turbo to provide the CFM needed at higher RPMs.

The key issue regarding lower lag on a diesel is the intake is always wide open. The engine is sucking as much air as it will and all that comes out at increased volume driving the turbo. When idling, slow or fast, there is not much fuel being burned and so theres not a lot of volume increase between intake and exhaust. This is a low boost condition -- the turbo is running slow. Still, its alot faster than one on an idling gas engine because that one is sucking on a closed throttle plate. The one in the diesel has a head start so to speak. It starts at a higher speed and so spins up quick when more fuel starts being injected to make the power needed to drive a load. It bootstraps itself effectively ... more fuel - more exhaust - more turbo speed - more boost - more intake - more exhaust.... This takes the engine quickly from a too rich condition in the initial response to a sudden load to the lean condition normal for diesels that are running below their HP rating. There is a brief puff of black smoke during the time it takes for the turbo to spin up.
larry

 

[EE_Bota]

I would buy the tractor I need / want, and if is has a turbo, so be it, and if not, so be it (not). I have heard of no problems with them regardless.

Since cars were mentioned, all things being equal, I would avoid turbo's in cars. If I just HAD to have a car that just happened to have a turbo, I would make sure it is oil lubed, but water cooled, rather than oil lubed and oil cooled.

My current car, a Subaru Baja, has a intercooled turbo, because I had to accept the turbo to get a 5-speed manual transmission, which I wanted. But as is typical, the compression ratio is lower on the turbo model, which has an adverse effect on efficiency until the turbo kicks in, and the car has to run premium fuel, which has an adverse effect on my wallet. The turbo model gets 23, but the non-aspirated version gets at least 28 mpg, and uses regular fuel. So, to a certain extent, a turbo in a gasoline engine results in operational circumstances that would be similar to having a variable compression ratio. Toss in variable valve timing (like my Baja) and who the heck knows what is going on then.

 

[RobJ]

The small power gain has nothing to do with the turbo. It is a design decision. Diesel engine power depends on fuel delivery (up certain limit) and I can guarantee you that, if given the fuel, turbocharged and even NA engine can deliver enough power to self-destruct. The designer decided to limit the power due to mechanical limits of the engine. Look at specs of some tractors they use the same engine displacement but the power of different models range from 67 to 95 HP. Typical tractor engine has 20 HP/Liter. That is why they last forever. It doesn't matter if they are NA or TC.
The TC engines are running cleaner and that is the primary reason for TC installation. To meet TIER II standards the engine is usually just turbocharged. To meet TIER III emission standard the engine will also have intercooler.
Speaking about reliability. Turbos are very simple devices that only rotate and put very small stress on the bearings. If properly designed (to keep the bearings cool) they will outlast the engine.
Typical industrial turbo compressor has at least 40,000 hours between overhauls and usually at least twice as much.

You can't just add fuel and get more power. That's like saying I'm going to run a mile sprint and breath normally. To get the fuel to burn you need more air. The stroke of an engine will pull in only so much air(the volume of the cylinder). The balance is in the air/fuel mixture. Change the amount of air by adding a turbo which forces or compresses in more air by volume, you can inject more fuel, which means more power.

If you are just driving around the yard with no or little load, the turbo isn't doing anything to help the engine....not enough heat being produced. If you are on the hwy next to a big rig, you'll hear the turbo kicking in that whine going up a hill. Going downhill nothing because the load is taken off. If you watch the exhaust temp, it will rise and fall a lot.

Turbos are great, but if you are not a heavy user of your tractor, I'd probably get the tractor without it if possible. Remember all those HP ratings are at peak load, not pulling a 6' finish mower in 4" grass. Put on a 6 row disk or subsoiler and find out what she will do!

Rob

 

[RobJ]

My current car, a Subaru Baja, has a intercooled turbo, because I had to accept the turbo to get a 5-speed manual transmission, which I wanted. But as is typical, the compression ratio is lower on the turbo model, which has an adverse effect on efficiency until the turbo kicks in, and the car has to run premium fuel, which has an adverse effect on my wallet. The turbo model gets 23, but the non-aspirated version gets at least 28 mpg, and uses regular fuel. So, to a certain extent, a turbo in a gasoline engine results in operational circumstances that would be similar to having a variable compression ratio. Toss in variable valve timing (like my Baja) and who the heck knows what is going on then.

Good example, but the turbo boasts more HP numbers I bet.

 

[megaboz]

Am I missing something here? Doesn't a tractor tend to run at one speed? Unless throttled up or down? If this is true then the exhaust is steadily flowing and the turbo is spinning at the same speed unless you bog the engine down. Engine speed doesn't change because you are driving around or running your PTO.

But more on point, turbos are old news and are reliable if the machine is maintained. Turbos generally require no maintenance unless something breaks.

As for the car comparison, personnally I think it has no bearing on this topic as these machine are not throttled up and down like cars and run on diesel.

 

[EE_Bota]

Am I missing something here? Doesn't a tractor tend to run at one speed? Unless throttled up or down? If this is true then the exhaust is steadily flowing and the turbo is spinning at the same speed unless you bog the engine down. Engine speed doesn't change because you are driving around or running your PTO.

But more on point, turbos are old news and are reliable if the machine is maintained. Turbos generally require no maintenance unless something breaks.

As for the car comparison, personnally I think it has no bearing on this topic as these machine are not throttled up and down like cars and run on diesel.

Tractors usually run at one speed for a given operation, but some had foot throttles.

Also, and I could be wrong about this, and particularly wrong about your tractor, but just because a tractor engine is running at a certain rpm does not necessarily mean it is running at a fixed throttle level. Many, perhaps most, are governed such that the engine may be running a given rpm, but when the governor senses a drop in rpm, it provides more fuel, which may result in more exhaust gases, and a faster turning turbo. My little BX is governed, and I think all tractors I have ever been on are governed.

 

[EE_Bota]

Good example, but the turbo boasts more HP numbers I bet.

Yes, it is a pretty peppy engine for a 2.5 liter four. It is essentially what they put in the WRX car, but instead in my little half truck. It would probably spin a wheel if not for the full time AWD, and limited slip differential in the rear.

According to this, 216 HP, 235 ft-lb.

MotorWeek: Road Test

 

[SPYDERLK]

Am I missing something here? Doesn't a tractor tend to run at one speed? Unless throttled up or down? If this is true then the exhaust is steadily flowing and the turbo is spinning at the same speed unless you bog the engine down. Engine speed doesn't change because you are driving around or running your PTO.

But more on point, turbos are old news and are reliable if the machine is maintained. Turbos generally require no maintenance unless something breaks.

As for the car comparison, personnally I think it has no bearing on this topic as these machine are not throttled up and down like cars and run on diesel.

Even tho it may run at one speed [set by you and maintained by the governor] it runs at different loads. More load requires more fuel to hold the rpm, which makes more exhaust which increases turbo speed causing more air to enter the cyls which causes more exhaust -- etc. The turbo does very little when the engine is idle regardless of the speed the engine is turning. As soon as load is applied ... see the second sentence, and post#32.
larry

 

[medicshawn]

Our fire trucks had superchargers (blowers). Quite different than turbos.

Everything we currently have is running turbos. I've never seen a supercharger on our equipment, but my department has pretty new stuff.

 

[piller]

What is the consensus about tractors with turbos?
.....
I can shorten this to say that I like the M6040 HST, M7040 HST and M59, but they are quite heavy and large for working relatively close to the landscaped areas, animals, barn, out buildings, and homes on our property. I have noticed that I could buy a slightly smaller/lighter turbo charged tractor (Grand L40 series) or a slightly larger/heavier M series.

I've got a Kubota M tractor with turbocharged engine and love it.
To the best of my knowledge you cannot get an HST transmission on an M6040 or M7040, although you can get the HD (hydraulic shuttle) which may be what you mean.