Engine "lugging"

[pete c]

I got into a conversation on another board with a guy about "lugging" my focus. I had stated that I wish there was a way I could install a higher 5th gear to get better mileage and thought it could easily pull a considerably higher gear because I could easily pull slight hills at 35 in 5th.

He thought that at that speed, I may be doing damage because I was lugging it. I disagreed because, judging by sound and feel, things were still operating smoothly, so long as I didn't call down to the engine room for anything more than a slight throttle opening.

My question here is at what point does lugging cause increased engine wear? Are you fine, so long as the sound and feel are good? Are you already doing damage if you hold a gear until the engine starts complaining? Is it better to just kick it down a cog well before lugging symptoms occur?

I guess this is yet another reason to invest in a scan guage type instrument as I would think that you would see a drop off in mpg before you felt any lugging symptoms.

And for the foci owners out there, I have an 05 ZX3 5 speed 2.0 duratec. What do you feel is a minimum acceptable speed for holding slight grades in 5th? Did this come with different "rear end" ratios? The guy I was talking to had a 2.3 duratec and it sounds like he may have had higher gearing which would explain his opinion on driving 35 mph in fifth. His claim was that with his car, you could basically idle in 5th on the flats, but anything requiring even the slightest throttle opening would result in a lugging condition. I find that I can idle along on the flats at 30mph in 5th, no problem.

[user removed]

The point I would even consider close to lugging is when you are climbing a grade and it gets steep enough that more throttle gets you no more speed. Combine this with the second ingredient, too low rpm and you might get closer to lugging at rpm 's below 13-1500.

Throttle position would never be close to WOT.

In the old carbed days with specific volume accelerator pumps, it was much easier to "lug" and engine by flooring it at much to low speed in too high a gear. Now you have doubled or tripled the fuel mixture, way too rich, and you can do real damage.

With modern efi that is impossible.


regards
mech

[Miller88]

There's various gearing available for the MTX-75. I believe my 2011 with the 3.58 gearset is the "tallest" that was available here in the USA.

I believe there is a warning about damage that can occur to the dual mass flywheel if you operate the engine at below 1250RPM with a load.

The transmission gearing is awful though. I'd like to find a shorter first and a taller 5th. I would be happy with a very wide ratio.

[California98Civic]

I routinely climb a 1.5 mile steep grade hill in fourth (I have the super tall VX/CX gearing), which I allow to drop to 1500 RPMs before shiftng to 3rd at about 38mph. I do that at part throttle, but about 75-80% load. That is not lugging by any definition I am familiar with. The ECU compensates for fueling issues. It actually leans out the fuel mixture very nicely. Here is a good discussion on a good discussion board:
How can I tell when I'm lugging my engine? | Mechanical /Maintenance Forum | Bob Is The Oil Guy

I hope that is helpful.

James

[JRMichler]

I regularly run as low as 600 RPM (18 MPH) in 5th gear. It will even accelerate, although slowly, from that speed in 5th. I've been driving that way since the truck was new. It now has 98,000 miles.

The alternator cannot keep up at that RPM, the voltage drops to 13 V.

[pete c]

I understand what the damage is, my question was more about when it starts to occur. Is running the engine just above the rpm where lugging symptoms occur, damaging?

[oldtamiyaphile]

If you take a production car to a race track you can measure engine life in hours (maybe 48hrs max). Low rpm operation is much more engine friendly. As Old Mech said, damaging detonation is a thing of the past, so IMO drive sensibly and don't worry about it. The ECU will protect you unless you're a complete tool, the fact that you even know what lugging is already puts you ahead.

My 1.6 petrol Renault will pull 5th gear at 20mph on level ground...towing a 1200lbs trailer. I wouldn't worry about what you're talking about, what RPM are you turning at 35?

[pete c]

Just shy of 1500. I find that I can idle along at about 25, no problem, on flat ground. By 40 it will pull a reasonably steep hill. I see no reason ths thing couldn't be geared to turn 2K or even a bit less at 60.