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Hello guys just started reading about this hypermilling stuff, i've been doing most stuff naturally trying to conserve gas myself, but i have a few questions.

My Car: 1998 Acura 2.3 Cl automatic

1. Acceleration - I am very confused about this still, which dictates how much fuel is being wasted throttle or rpm's?

Should i accelerate super slow with low throttle even if the rpm's stay high or should i try to get through the gears as soon as possible to get lower rpm?

Does the car automatically control fuel? say the throttle is at 50% but at 2,000 rpm and at another instance its at 50% throttle but 4,000 rpm which is burnng more fuel?

Please the more details you can add the better!


2. Pulse & Glide - Can you get fuel savings by using this technique on a non hybrid car without turning off the engine but putting it into neutral? And does this work at high speeds?

I tried it today on the highway after reading about it, but it seemed like i was just wasting alot of gas accelerating and when i was gliding it only lasted for about 10sec.

I was doing this on even road, In my opinion in sounds better to do this before a down slope and get more glide? What is the best way to apply this, it just seems like there is to much drag at high speeds to be effective. Please help again the more detailed the better.

3. This kind of goes back to the 1st question. One of the tecniques where you old the throttle steady on up hills and down hil you gain momentum, i forgot the name of the technique sorry lol.

Now when my car starts rolling downhill should i let up on the throttle or keep it the same to gain more speed and momentum? And this is where the #1 question comes into play, If i hold the same throttle and im going down hill and now my car starts accelerating faster and faster and rpms are going higher, is it wasting more gas? So same principal which dictates how much fuel is wasted rpms or throttle?

4. Should i use Cruise Control? - or the above mentioned technique for roads with not alot of hills maybe a few small ones like 10 degree grades or so.

I guess 3 out of the 4 can just be answered with the acceleration response. If RPM dicates fuel being burned then i guess CC would make more sense most of the time since it keeps it steady and does not accelerate faster.

And Lastly

5. What is good psi for tires in the winter? Mostly for highway driving, i know in the winter the tires can handle more since air compresses. I do 30psi now but i think 35 would be better. Would 40 be to much in the winter and highway? i don't want to hit potholes and have a bubble form on my tire have had his happen before thats why i dont inflate them that much anymore. Any big differences in mpg in more inflated tires? I know performance wise more preasure better handling.


Anyway Thanks for your time guys,
Elsid

In general, the throttle determines how much fuel is injected for every revolution of the engine. (This is a gross oversimplification, but it's OK as a first approximation.) But the higher your RPMs, the more often you are injecting that amount of fuel.

So if you are going the same speed (MPH) in two different gears, one at 2000 RPM and one at 4000 RPM, and you can maintain your speed with 30% throttle, you will burn approximately twice as much fuel in the lower gear at higher RPM.

For accelerating in a manual transmission car, I like to use from 25% to 50% of the throttle, and shift somewhere between 2000 and 2250 RPM. It's a lot more tricky for me in an auto, because I find it difficult to know how to convince the trans to shift when I want it to, and I am not good at figuring out what acceleration/throttle setting won't burn too much fuel but will get the trans to upshift.

RPM is usually a bigger factor than throttle position, except possibly when you go over 75% throttle or so, and the car goes into "full enrichment, give me power now!" open-loop mode.

For driving steady-state, you want the lowest possible RPM in the highest possible gear, with the torque converter locked up. That may turn out to be slower than you really want to go (in my CRX, that's 35-40 MPH, and I won't drive that slow on the freeway!) so you may have to adjust that figure.

The hold-the-throttle-steady technique is DWL, Driving With Load. The general notion is that you keep your throttle steady on the uphills so you bleed off speed. If the downhill section is shallow, you can keep that throttle setting on the way down to gain the speed back. If it is steeper, you may want to shift to neutral.

Pulse and Glide is generally easier at lower speeds. If you can find space to slow down and speed up a whole lot, you can probably get the high-speed P&G to work with a large "delta" (difference between your top speed in the pulse and the bottom speed in the glide), like 20 MPH or more. Usually for the pulse, you want to stay around 2000 RPM and 50% throttle. Convince the car to shift up by 2300-2500 RPM if at all possible. The folks with real instrumentation--read that as "Scan Gauge II"--shoot for specific load measurements, while the rest of us make do with guesswork.

I set my tires to the maximum sidewall pressure, summer or winter. Except my "winter" isn't exactly what most folks on the BBS would recognize as "winter"--more like "grey and sometimes rainy, but not very cold". So I have no idea about snow traction...

I hope some of this helps. And I hope others with more experience will chime in.

-soD

Welcome, Elsid.

Read the Beating the EPA (http://www.cleanmpg.com/forums/showthread.php?t=1510) article for fuel economy tips.

1. Generally speaking, rpms are a better indicator of fuel consumption than throttle position is. 50% throttle at 4000 rpm will consume at least twice as much fuel as 50% throttle at 2000 rpm - usually more, since air resistance increases with the square of velocity. My experience is you're better off accelerating as fast as you can without forcing torque converter slippage and/or gear kickdown. Typically, I try to keep the rpms under 2000 while building enough speed to get the automatic to upshift. If the TC slips and rpms increase to 2500 or 3000 rpm, it clobbers my fuel economy.

2. P&G works for me. I've driven the same 10 and 20 mile routes with cruise control, DWL, and P&G. DWL adds a mile or two/gallon over CC. P&G adds 3-5 mpg over CC with an automatic, but 20+ mpg with a manual. The benefits of P&G are highest when your glides are longest in proportion to your pulses. If you can pulse for 8 seconds and glide for 16, it's working. If you pulse for 8 and glide for 40, it's really working. If you pulse for 8 and glide for only 8, it's not worth your effort on that road at that speed and grade. P&G works best for me at slower deltas. 50-65 mph, or 45-60 mph in 5th gear, might get me 50 mpg. 25-40 mph in 4th gear might get me 60 mpg. 15-35 mph in 3rd gear might get me 70 mpg. Those are manual transmission results, with EOC. I can barely beat DWL by 2-4 mpg with AT P&G.

3. You're describing Driving With Load (DWL). You imagine keeping the throttle in the same vertical/horizontal position, so you ease off as you crest a hill, use minimal throttle descending the hill, give a little throttle on flats, and just enough on hills to make it to the crest.

4. Cruise control works, to a point, but it's dumb. Left to its own devices, it wastes fuel by causing torque converter slippage and downshifting on hills to maintain speed. You can beat it by modifying your DWL to build up more speed on flats prior to hills, and bleeding off that speed as you're climbing those hills. In my case, if I keep my load % below 70, I can climb most hills in top gear with my AT without slipping the TC and wasting any more fuel than necessary.

5. I inflate my tires to the sidewall maximum inflation pressure, but I don't have ice or snow on my roads. You'll need to experiment for yourself what pressures work for your winter tires under your road conditions.