Weight difference: Power vs manual windows.
 

I was having an informal discussion recently with some engineers about weight saving in cars and some of the mods people can do themselves when the topic of windows came up.

The general thoughts of this group were these days the weight savings were about nil as modern power window mechanisms weighed about the same as their manual counterparts.

Does anyone have any numbers or comments on this?

Peter.

I don't have numbers but that sounds right. Also I've heard the Insight 1 came only with power windows for weight saving reasons- that is also the car that had special lightweight carpet?

Lupo 3L has manual windows and the total window lifting mechanism weights about 1.5 kg. (took them out) Although today the electric window lifter version is lighter, but the difference is not big. If I remember correctly one kilo saving for four side windows etc.

In my 89 Jeep, I took the power motor from the back and moved it to the front to replace the dead motor, and put manual in the back. The manual was lighter for sure, but not by a whole lot.

If you want lighter, don't fight gravity.
and use slider windows, not roll-up and down windows.
I'm still trying to figure out how to do the windows on the MGeo as light as possible, and thinking sliders.

basjoos-type aero > any weight reduction carving
But that is just my opinion.
EDIT: I got to thinking, what if your average speed is low, lots of light to light, stop and go?
I keep assuming people live in the more wide open spaces where you can get rolling, like Basjoos. That is a bad assumption on my part.

I'm not sure what this disregarding weight reduction I'm hearing lately.
perhaps because you can't get high MPG in stop-n-go traffic.
Bragging about big MPG is going to need highway runs and aero is big there.

Lower weight is also a big factor in highway mileage too, why?
Because a very lightweight car CAN USE A MUCH SMALLER ENGINE
to get it up to speed, and thus get better highway mileage..because it has
a much smaller engine. Of course if you have an existing car and can't change engines, the lighter car isn't going to matter much for HIGHWAY mpg.

And I didn't even mention that a lighter car will accelerate faster, and make driving more enjoyable and even safer, oh I just did.

Or

You could take a page from the drag racing hand book and use a seat belt strap to raise and lower the window. (Hurst Hemi Dart)

Some old (50s and 60s) race cars used leather belts to raise the windows. Lexan window, of course! Attach the belt to the bottom, make sure the window fits in the tracks, run the belt out at or near the top of the inside of the door. Have a hook on the inside that one or another of the holes in the belt hook on, and you can keep the window at that height.

-soD

I have a related question.

We know that open windows are horrible, aerodynamically speaking and AC saps multiple hp from the engine.

Considering that most everyone in america spends at least part of the year needing one or the other, has anyone come up with an aerodynamically cleaner way of getting sufficient airflow to avoid using AC? I would guess that intake vents drawing air from under the car and exhausting it in the rear where there is a low pressure area to suck the air out, might work well.

I can get a gale-force wind through the knee vents in my '59! :thumbup:

I put a moonroof in one of my Tempos and even slightly cracked it lets a lotta heat out when parked and moves air nicely when going. I think the aero hit on a window that tips up like that vs retracting is quite small.

Power vs Crank windows: do these weight estimates include all the extra wiring and switchgear? Power windows and locks really make for fistfuls of wires going all over, especially to the driver's door.

why have automakers stopped making cars with those vents? is it because just about every car out there has AC now?

Probably just cost reduction.

Those vents hafta be waaaay cheaper than a/c! :eek:

Probably consumer demand for a/c made them redundant; then it was too tough to fit them to only no a/c vehicles, of which there are damn few. :mad:

In summer, during the four warmest months of the year, I drive a convertible. If it isn't raining, the top is always down (along with the power windows, and the A/C being off.).

If you really think the weight of a power window motor is going to have any measurable effect on MPG, then this is the wishful thinking list. Or the OCD list. AKA the Ecomodder list<?> :rolleyes:

They already have to have AC available for the higher trim levels. It makes more sense for the manufacturer to slap the system they already have into the lower trim levels than to engineer a system of vents and controls for the lower trim levels because that'll never pay for itself. If it were an "eco" feature that they could charge extra for, then it probably still wouldn't make sense to build.

Weight reduction still makes a lot of sense around town. Doesn't every 100 pounds use 15 hp? With stop & go, you're accelerating all that weight all the time.

need to move that decimal point over. If 100 pounds = 15 hp
my truck needs more power than a veyron, and about 2000 hp with the trailer :)

Same question, but concerning power and manual seats. Any ideas on the weight difference?

Power seats annoy me because they are way to slow to adjust. The only thing I like about them is the memory ability for multiple drivers (which I don't use yet since I'm not married).

I had read a magazine article once that casually mentioned it, but I never examined it.

For acceleration it's about power and weight. My car, with a curb weight of 3355 pounds and 250 hp has 13.42 pounds per hp. After I plant my 200 pounds in the driver's seat, each of those poor horses now has to push 14.22 pounds off the line. I'd need to add 15 hp worth of cold air intakes and ricer decals to bring the lb/hp back down to 13.42 again- or I could find 200 pounds worth of interior trim to get rid of. So for accelerating my car, 100 pounds is more like 7.5 hp. On the sporty things that most magazines like to review, 10 or 15 hp per 100 pounds shouldn't be all that unreasonable to see.

Anyhoo, the brisk acceleration that you want in your pulse & glide or stop & go can be more efficiently acconplished by reducing the weight that you are accelerating.

I like power seats because they have more than just a few notches to choose from. Of course they're heavier and if something breaks then they're obscenely expensive.

I can tell you that the difference is very noticeable on my wife's car, a 1982 911. We have a power-adjustable "sport seat" that we put in for track days, and the non-power "standard" seat that we put in for daily driving. I can certainly feel the difference when picking the seats up. Probably something around 10 lbs difference, possibly more.

Some of that is due to the sport seat being a bit larger (more bolstering) than the non-sport seat, but some is definitely due to the electric motor and actuators. Those are much heavier than the manual adjusters.

Of course, that is 1980s tech. Electric motors have gotten smaller, lighter, and more efficient since then. I'm not sure what the difference would be these days.

-soD

True that acceleration will be quicker with less weight, and I agree about the benefits of reducing it. However, the added weight will also extend the glide portion of the pulse and glide technique. While it may take longer to accelerate, it will also take longer for speed to bleed off.

My motorcycle is terrible at the pulse and glide because it's so aerodynamically inefficient compared to the weight. The instant I'm off the throttle, speed plummets. It takes a heck of a steep down-hill for me to maintain speed at coast. The same hill in my car would produce too much speed.

I'm not doubting or disagreeing with anything you said. With a maximum difference of 10 pounds, do you think that by reducing that 10 pounds it would provide any measurable gain in fuel economy in any vehicle?

There are some here that suggest that it would, or that it should be done out of devotion or compulsion for the hypermiling belief, and therefore it would always be beneficial, or at least virtuous. That is what I am questioning.

Most modern cars remove manual window options for simplicity in manufacturing and design, increased profit margins and marketability and weight savings in modern systems.

The Corvette C6 advertised their transition to electric door locks and handles due to the weight savings. Modern micro motors are powerful, reliable and light weight which all make for a superior option for the engineers, marketers and customers.

then again, VW (and Skoda and Seat) put manual windows in the base versions of the Up! (Citigo and Mii) on price grounds.

Bean counters can be weird ;)

Another advantage of motorized seats, mirrors, windows, etc is that the motors produce a known amount of force. All of the components required to transfer that force into motion can then be designed to withstand that known force. With manual windows, some margin of extra strength must be built in to accommodate He-man window closers. Taking the human out of the equation produces more reliable results.

This is true. I have broken few sidewindow cables with too much force when the window was frozen and still tried to open it...

Brute. :)

Nothing weird about this.

If the manufacturer expects a considerable percentage will opt for the manual windows, it makes sense.

I've never had any issues with manual windows.
On the Volvo, the driver's side powered window is rattling in its tracks.

I think it's all about money. The power windows, mirrors and locks help the manufacturer justify a higher price on the MSRP. They save money by not having to design and stock the manual components, not having to train someone to install the manual components, etc. They make money by selling repair parts and services when they fail sometime down the road.

I could not care less for power windows and mirrors, but power locks are important to me so I can have remote keyless entry. Much nicer as I run toward the car on a rainy day. :thumbup: And, I kinda like power seats, because my wife is short. With power seats, she moves forward and upwards and she appreciates that. Not too many manual seats in the domestics go upwards. At least they did not in the past. I've only been driving an import for a bit over 2 years now. {Not likely to by another Kia to replace this one though.}

I've had many issues with manual windows. Only recently my TSX power window has been making noise that concerns me. The takeaway from my story is that anecdotes are next to worthless when trying to determine the truth of the matter.

There are a number of imports that have seats that raise and lower. My MINI is one such.

-soD

never liked power windows