Haha I like Red MX5s description of lugging. Bwaaaaaaaaaaaaa!

If you are cruising 40mph in 6th (I think at or about 2500rpms), you CAN accelerate in this gear up to 60, just not swiftly or linearlly. You have to barely increase your throttle that you are using to maintain speed. This way, you speed up a little, without lugging, then, as you progress in speed, you can lay down on the throttle a little more.

If you were to graph speed of the car vs. throttle applied in 6th gear, to optimize acceleration and minimize lugging, the graph would get exponentially larger , would look like x=y^2.

It is not the fastest way, but it is in no way dangerous to the engine.

 

Well, the reason that the acceleration is not occurring as swiftly, is that at detonation, the expanding gasses face a higher resistance in pushing the piston out of the way.

The piston cannot move as fast under the pressure of the expanding gas due to the resistance from the tranny. The same gas expansion pressure is present, the pressure just cannot move the piston out of the way as quickly.

This translates to extended time in the high pressure cycle or longer durations of higher pressures exerted against the piston, rings, and attached components.

The quicker the piston can move out of the way, the quicker the pressure will decrease in the the cylinder.

In the end, I would guess that applying pressure against components is a factor in wear. As such, I would think that keeping the pressure/duration curve lower, is better.

 

It doesn't matter if you're cruising on 6th while doing 40mph.
It depends on how much throttle you're using as well.
Very light throttle on 6th @ 40 mph is not lugging the engine.

For me, I normally cruise around 3.5k rpm.
Basically, I barely shift to 6th around town.(up to 50mph)

Dan

 

I think you may be hurting your fuel economy.

 

I don't know exactly what you mean. Light throttle or heavy throttle is irrelevant since we're talking about "cruising" speed. If you're cruising at 40mph in 6th, you're maintaining a specific throttle position, if all things equal of course, meaning no major elevation changes. Too light of a throttle and you will be under 40mph. Too heavy of a throttle and you will be over 40mph. 40mph at 6th is simply 40mph at 6th. Bottom line...you're lugging the engine.

 

I decided to try this out today and cruise at 40mph in 6th, it can be done and it was definately over 2k rpm. I dont think the rpm's went too low to cause 'lugging'. Now if somebody tried and accelerate heavily in 6th gear doing 40mph is just plain retarded, although im pretty sure thats not what the people here are doing.

Just my personal preference I still wouldnt go into 6th unless im doing at least 50ish, I like having a decent amount of power on tap without having to downshift just in case. And the car just doesnt feel "right" to me when the rpms are that low just a personal preferrence though

 

Harder I drive my car, it gets better gas mileage.

I used to just drive calmly around town.. I got 22-23
I hit redline every couple times and i get ~25/gal.

Odd.

 

Dan, I searched for a better definition and could not find one. I'm inclined to think of lugging as being like pornography. I may not be able to define it, but I know it when I see it.

I'm inclined to think that lugging can be caused by a number of factors, either together on individually, rather than being caused by a single factor like hydrodynamic wedge. For example, my old X-1/9 made peak power at close to 9k, and reved to 9k, but back then we were stuck with a single cam profile, so the engine had horrible drivability below 4k or so, even in the lower gears. Trying to accelerate from 3,000 RPM in third generally resulted in bucking and sounds I associate with lugging, and obviously made the little engine very unhappy. You had to let that little puppy spin to get it to pull smoothly, but with stock cams and tuning, the same engine would pull smoothly from 3k in fourth gear as long as you used a light touch on the throttle. It seems to me that letting the engine fall below the point where it makes power smoothly, and asking it to accelerate, is also a form of lugging, and falls within the "labour" definition. Maybe this isn't really lugging the engine, but it has the same "look and feel," which leads me to believe that there must be more than one factor involved.

I guess it's pretty obvoius that I've never looked into this in any great detail. I haven't studied pornography either, because I'm just not interested. I know it when I see it, and that's all I really need to know. But, now that it's come up in this thread, I'm curious. Have you (ZDan) actually looked into this enough for me to look to you to further my education?

 

I've tried it too, and you can actually accelerate from insanely low speeds, in sixth, if you us a light enought application of the throttle and are willing to wait for the leasurely acceleration you can get without lugging the engine. It's not easy, and IMO, not very smart, but it is possible.

I know I said this in an earlier post, but when I'm in traffic, I tend to upshift between 4k and 6k, and most frequently at very close to 5.5k. Once the flow of the traffic is "up to speed," I shift on up through the gears, or not, depending entirely on the prevailing conditions. I am likely to start downshifting sooner than really necessary, and except for the time I spend at a constant speed, I'm pretty sure I spend most of my time at least a gear lower than I really need. I don't really care if I'm getting 1-2 MPG less; I want to have plenty of zip on tap when and if I need it, and I drive the car for pleasure, not for economy. If I want economy I drive the Benz, and if I wanted more economy that that, I'd get a Prius. 1-2 MPG just isn't enough to worry about. But that's just me, and *my* preferences. Keeping the car out of VTEC does save some fuel, but what's the point of having a performance car, if you're not going to use the performance? That's the one part of all this that I'm having trouble understanding.

 

You had a FIAT that revved to 9k?! Reliably?!

I always thought X1/9's were cool, but never researched them much, assuming they were small-displacement but low-revving rustmobiles. Guess I was wrong! About the low-revving part anyway...

No, i haven't looked into "lugging" much further than having enough mechanical sympathy to "know it when I see it", and not floor it in a tall gear at low rpm. I know that high load at low rpm does a few bad things, including increasing propensity for detonation, and high loads on reduced cushion (i.e. hydrodynamic wedge). On top of the inherent mechanical issues, there is also the issue of whether or not the engine is out of it's "tuned" range (less a problem with modern automobiles".

My 240Z has a big torque dip at ~4000 rpm. If I punch it at that rpm, it doesn't want to pull as hard due primarily to (I think) flow reversion and multiple carburetion. But at that rpm, it's not at much risk for detonation or overloading of bearings due to weak hydrodynamic wedge. You could call it "lugging", but IMO it's not really doing harm to the engine. It's just not operating at any kind of decent volumetric efficiency. Pulling out of turn 3 at NHIS (now NHMS?) I have to endure a lull in acceleration when I shift from 2nd to 3rd as I catch the top end of the torque dip. But I don't think I'm hurting anything.

Call it "bogging' instead of "lugging", maybe...