When am I lugging?

[Exrald]

Originally Posted by humfrz

Waaaaay toooo late.

Back-in-the-day, my engine stayed below 3000 rpms AND the transmission (which consisted of a idler pulley, that when manually tightened up against the belt between the pulley on the driveshaft and the pulley on the drive axle) would make the car go faster .....or less fast. Did ya get all of that .....??

I started with a auto transmission (called a centrifugal clutch) and converted it a manual transmission (described above) ........because ......

A MANUAL TRANSMISSION WAS MORE MANLY in my roadster .....


humfrz

You like to control her (your roadster) with a stick huh? Lol jk 😜

Sent from my SM-G920I using Tapatalk

[Tcoat]

Originally Posted by humfrz

The one time that I remember most was in a semi-tractor trailer hauling bulk milk. Coming off of a Interstate off ramp at night, waaay too fast, went to gear down, got all tangled up in the gears, a stop sign with a "T" ahead, I panicked and locked up the trailer brakes to stop ...... while I sorted out where I was gear wise.

The fellow behind me WAS NOT impressed with my trucker skills.......


humfrz

That note on the plate that says "Do not change range while moving in reverse". Ya, they really mean it.

[Clipdat]

Nice cat.

Originally Posted by humfrz

Waaaaay toooo late.

humfrz

Crap, he traded with me too! I remember his car feeling great above 4k, especially with that catless header. Then he told me afterwards he was in 4th gear through the corners I was going through in his in 2nd and 3rd. O.O

Originally Posted by Ultramaroon

I knew something was up. My car was never the same after we traded, that day.

[Ultramaroon]

Originally Posted by Clipdat

Crap, he traded with me too! I remember his car feeling great above 4k, especially with that catless header. Then he told me afterwards he was in 4th gear through the corners I was going through in his in 2nd and 3rd. O.O

lol

Wish he still hung out here. I Miss him.

[anutjob]

There have been a lot of replies on this topic, but I'd like to put in my opinion as well.

12mph is about 20km, you'll bet I'm still in 1st gear during upshifting. I have accelerated in 3rd at this speed. I wouldn't consciously do that again. IMO, either 1st or 2nd gear is fine at this speed.

I haven't had this car for long. I have 2800km on the odo. In general I find the car happiest when I stay above 2500RPM. Yes I sometimes go lower when I'm not putting much stress on the engine, e.g. going down a slight hill.

The reason why I always try to keep it at at least 2500 RPM is that under that RPM, I can often hear what sounds like early detonation when I try to accelerate. It almost doesn't happen when I'm above 3000 RPM.

In short, if I'm going on flat ground, I cruise at about 2500-3000 rpm. When going uphill, I'm never under 3000 rpm. When going downhill, I sometimes go as low as 2000 rpm, or I downshift 1-2 gears to utilise the engine breaking while staying at the speed limit.

I haven't noticed a difference in fuel economy when driving at 2-2.5kPM vs 2.5k-3kRPM, but your experiences may vary.

When in doubt, always go to a lower gear.

[Ultramaroon]

Originally Posted by anutjob

The reason why I always try to keep it at at least 2500 RPM is that under that RPM, I can often hear what sounds like early detonation when I try to accelerate. It almost doesn't happen when I'm above 3000 RPM.

Welcome to the forum.


You probably hear the sound of the free gears rattling in the gearbox. It's really nothing. I regularly idle along in first or second as low as 1000 rpm when in slow traffic. Just avoid stomping on it.

[86MLR]

Throttle control
RPM
Road speed
Gear choice

If you think about these things, and you understand the reasoning of why you are thinking about these things, you will be golden.

Me, I just wring it's neck, or, when stuck in traffic, use the above principles.

Disclaimer: I give no cares for fuel economy, my cares revolve around induction, spool and a nice sound coming from the exhaust.

[gravitylover]

Originally Posted by Ultramaroon

Welcome to the forum.


You probably hear the sound of the free gears rattling in the gearbox. It's really nothing. I regularly idle along in first or second as low as 1000 rpm when in slow traffic. Just avoid stomping on it.

Yeah you kind of roll into it. It helps if you can do it on a small downhill and the car naturally does it for you. It can make you feel like a real pro

[callisto]

After years of investigating, I think I have found the gear shift indicator thresholds; they would be useful for estimating when "lugging" could occur, but they're calculated in part using the engine load, which isn't shown on the dashboard anywhere. This isn't a perfect answer to the original question, much less the years of debate since then, but it's helpful for estimating, because it specifies a clear range of rpms at which the car would suggest you upshift; at higher rpms in lower gears or on an uphill incline, at lower rpms in higher gears or on a downhill incline.

The process for firing the GSI in gen1 is:

- given the engine's current load (0.0-1.5)
- multiply it by a correction factor based on current gear (1.35x, 1.15x, 1.00x, 0.85x, 0.80x for 1st-5th)
- look up the threshold in the load-to-rpm table (1600-3000rpm)
- if your rpm is at or above the threshold, and your speed is 10km/h or higher, trigger the GSI

That's a lot of calculations to ask of people that are driving, which is why they reduce it to a flashing light, but there's some useful derivations here.

Subaru is unlikely to have programmed the car to tell you to upshift into damage-inducing lugging so long as your goal is to maintain your current speed at your current load after shifting, so these values provide a safe guideline for coasting without lugging assuming no change in road incline.

My engine idles at 0.18 load, so my absolute minimum upshift speeds assuming a vertical downhill incline (gravity's doing all the work but my wheels are turning) are from 1st->2nd at (0.18 * 1.35) = 0.243 -> 1875rpm, ..., 5th->6th @ 1600rpm. Looking at a random datazap log trimmed to >1600rpm, typically I only see load 0.1 when I let off the gas altogether and usually I'm at load 0.25-0.3, so for practical purposes that's (uncorrected) 1800rpm; which, after correcting for gear-

Minimum upshift thresholds assuming NA gen1, flat level road, no significant headwind, and very tentative estimates on the resulting rpm after the shift:

1st->2nd @ 2400rpm -> 1500rpm
2nd->3rd @ 2100rpm -> 1450rpm
3rd->4th @ 1800rpm -> 1400rpm
4th->5th @ 1500rpm -> 1250rpm
5th->6th @ 1450rpm -> 1150rpm

In each case, these should leave you not lugging the engine so long as you just maintain the speed you shifted at. Which means, yes, you can absolutely end up in 6th gear at ~1100rpm without lugging the engine so long as you don't ask anything more of it other than just staying the course. (In practice, this is likely to demonstrate just how not level most roadways are.) So, given that shifting pattern and my napkin estimated rpm conversions - and keep in mind these are very, very approximate, so I may come back and redo this formally with a spreadsheet later:

Minimum downhill rpm for each gear, assuming you're coasting downhill with your foot off the gas and the headlights and air conditioner are off:

2nd gear: 950rpm
3rd gear: 1100rpm
4th gear: 1250rpm
5th gear: 1200rpm
6th gear: 1100rpm

Minimum level rpm for each gear if you're trying to coast at a given speed on a level surface:

2nd gear: 1500rpm
3rd gear: 1450rpm
4th gear: 1400rpm
5th gear: 1250rpm
6th gear: 1150rpm

Minimum max load capable rpm for each gear, assuming either a vertical incline or you wish to be able to floor it without lugging at any time:

2nd gear: 1800rpm
3rd gear: 2100rpm
4th gear: 2300rpm
5th gear: 2400rpm
6th gear: 2350rpm

Practically speaking, you're probably not upshifting into the highest possible rpm and then expecting to floor it, but hopefully this provides a better sense than just 'you'll know it when you feel it' or 'only shift at 4000rpm' or whatever.

And if that's all too complicated, TLDR: lugging in 2nd-6th at sea level on 91oct is below 1200rpm downhill, 1500rpm level, 2400rpm steep uphill.

(Oh, and you can always upshift at 3000rpm without lugging it, apparently.)