Diesel vs gas

[VroomVroom]

Would a similar size diesel pull harder than a similar size gas tractor?

 

[Texasmark]

Closest comparison I have is a JD 4010 and 4020...You can www tractor data site to see the specs. The 4010 was diesel and the 4020 was LP. The difference to me was night and day in several areas. I got just as much work done with the 10 as I did with the 20 with a whole lot less hassle and operator discomfort.

I started with gas tractors Farmall Super A and then IH 464, 1974 model I bought in '79 with several hundred hours on it, used as a bush hogger. The A was unique to low hp magneto driven units. The 464 was modern and equipped as such. I kept it for 5+ years and it was problematic for me, main problems were fuel associated and getting it to start in cold weather....yes getting it to start in cold weather. I did have a MF TO 20 that was a good gasser considering it's capabilities and later a MF 35 that was nice, but gas. I had a MF 35 Diesel also and it's torque curve peaked at 1000 rpm with PTO at 1600-1800 forget which. It was a super tugger, much more than the gas version.

As time went by I sold off the gassers and stayed with diesels. Not sorry. They just run, work, fuel is safe (for fuel), easy to get and use, plenty of power, torque and they will sit for a year and with a fresh battery fire right up, no fuel issues (but I use Power Services products just in case).

For me, it's diesels, hands down.....When's the last time you saw a piece of heavy construction equipment that was a gasser?????

Never had a diesel pickup truck. Never will. 1991 Ford 350 dually, 460 V8, 4 (OD) on the floor; Ram Hemi, 2009 5 sp. auto P/U......... ruined any chance of me ever having a diesel PU. The Ram solved the only problem I had with the Ford...old technology engine....loved the gas pumps but it could work as could the Ram. That Ford was the only stick shift vehicle I ever owned that you could dump the clutch at idle with a load and it just smiled at you.

 

[Tractorable]

The high compression ratio of a diesel keeps the power coming on. It’s a stark difference between a L2501 diesel at ~25:1 compared to a 6:1 compression ratio on a Ford 8N, both about 25hp.

 

[dodge man]

25:1 compression? I doubt that more like 17:1.

As far as horsepower goes a gas engine of the same displacement will out perform a diesel. With tractors weight is not that critical so you slap a turbo on or just put in a larger engine.

The power curve of a diesel is also good for tractor work. If the engine gets loaded down and slows down there is still good torque at lower rpms where a gas engine falls on its face and will die.

 

[prof fate]

got my first diesel last fall - compared to gas tractors it uses a LOT less fuel - 1/2 as much for some things.
Diesel doesn't go bad like gas does sitting - here in the NE that matters as equip sits in the winter and the fuel goes bad..creates issues.

Diesels tend to have more torque and have it lower, but with an HST you're supposed to keep the revs up regardless so probably not a lot of difference - geared, perhaps more so.

 

[MossRoad]

IF the engines are rated at the same HP and the drawbar HP is the same, they will pull the same. HP is HP is HP and torque is torque is torque. No exceptions.

So you have to start by comparing apples to apples.

Start with displacement. The diesels will typically have larger displacement than the gas of the same HP rating. And the diesels will have longer strokes. Those long connecting rods are longer levers to push the crank around. This means more torque.

Diesels have the advantage of being able to hold in a good torque range longer than the shorter stroke gas engines. That's what you want when pulling loads. If the engine starts to bog, it has a better chance of recovering and staying in the torque range. But, again, it's not comparing apples to apples due to the larger engine displacement and/or turbocharging.

 

[Tractorable]

IF the engines are rated at the same HP and the drawbar HP is the same, they will pull the same. HP is HP is HP and torque is torque is torque. No exceptions.

So you have to start by comparing apples to apples.

Start with displacement. The diesels will typically have larger displacement than the gas of the same HP rating. And the diesels will have longer strokes. Those long connecting rods are longer levers to push the crank around. This means more torque.

Diesels have the advantage of being able to hold in a good torque range longer than the shorter stroke gas engines. That's what you want when pulling loads. If the engine starts to bog, it has a better chance of recovering and staying in the torque range. But, again, it's not comparing apples to apples due to the larger engine displacement and/or turbocharging.

I agree that mathematically HP is HP and torque is torque, no exceptions.

However, I recently had the opportunity to bush hog very thick grass using both a 2017 L2501 HST and a 1952 Ford 8N back to back using the same mower on the same property. The L2501 performed drastically better than the 8N despite having less displacement, shorter stroke, less HP, and less torque. The diesel was able to maintain rpm much better than the 8N. It’d be interesting to know the reasons why?

 

[buickanddeere]

The high compression ratio of a diesel keeps the power coming on. It’s a stark difference between a L2501 diesel at ~25:1 compared to a 6:1 compression ratio on a Ford 8N, both about 25hp.

There is Mechanical compression ratio and what actually does the work , the effective compression ratio due to cam timing and volumetric efficiency .
Besides the point, the engine makes power with the effective working pressure . With the same cam timing , rpm , bore and stroke . A gasser with 200psi compression pressure and 600psi combustion combustion pressure . The gasser will make more power than the diesel version with 600psi compression and 900psi combustion pressure .

 

[buickanddeere]

I agree that mathematically HP is HP and torque is torque, no exceptions.

However, I recently had the opportunity to bush hog very thick grass using both a 2017 L2501 HST and a 1952 Ford 8N back to back using the same mower on the same property. The L2501 performed drastically better than the 8N despite having less displacement, shorter stroke, less HP, and less torque. The diesel was able to maintain rpm much better than the 8N. It’d be interesting to know the reasons why?

.

Look at the torque rise between the two engines . The four stroke diesel diesel at max HP and rated rpm is rapidly loosing Torque due to loss of volumetric efficiency . No wonder that torque increases but power decreases when the diesel is lugged down to lower rpms where there is enough time to fully fill the cylinders with air .
The 8N and two stroke Detroit diesels have a reasonable flat torque curve .Once lugged to max torque they will loose rpm as torque does not increase as they are always fully filling the cylinders.
It is why a Detroit Diesel in a truck is still pulling hard when it hits redline and an upshift is required . A four stroke at redline is loosing both torque and power .

 

[MossRoad]

I agree that mathematically HP is HP and torque is torque, no exceptions.

However, I recently had the opportunity to bush hog very thick grass using both a 2017 L2501 HST and a 1952 Ford 8N back to back using the same mower on the same property. The L2501 performed drastically better than the 8N despite having less displacement, shorter stroke, less HP, and less torque. The diesel was able to maintain rpm much better than the 8N. It’d be interesting to know the reasons why?

Yes, it would be interesting.

I'm just guessing on a few these things:

For one thing, there's a 65 year age difference in the machines and the technology. Who knows how strong that 8n engine is. It could be low on compression, etc.... or it could be just fine.

Something else is a lot of people say the 8n isn't an ideal machine for brush cutting. It's geared too high in 1st. With the HST, you have infinitely adjustable speed and the PTO always stays the same RPM. The 8n doesn't have a live PTO. If you put in the clutch, the PTO gets disconnected from the engine, but stays connected to the drive train. So it slows down. And unless you have an overrunning clutch, the intertia of the spinning blades can push the tractor along unless you disengage the PTO.

The 8n also has tires that are about 4" larger in diameter, so that effects its gearing as well.