$5.00 per gallon gas strategy

[YoDoc]

Originally Posted by JTM

I'm throwing the BS flag: There are plenty of people that still drive 55 everywhere, even in West Texas where the sign says 80, and their safety is only at risk because they think the left lane is where they should be.

Throw it all you want, you are still wrong. My wife and I both drive 183 twice a day, every day. Minimum speed (when you aren't stopped) is around 60. That puts you in the far right lane, which disappears and reappears with exits and merges and splits, and also puts you right in the way of people getting on the freeway who want to go 80 and not look where they are going. I don't know why you think that west texas traffic is the same as DFW or Houston traffic, but there is absolutely no comparison. 183 is disgusting. I'm talking 80 mph, one car length in front and behind, dangerous.

So, if you think you can drive at 55 on 183, when everybody else is doing bare minimum of 60, come on out, my friend. Don't ask me to come with you though. I'll be keeping up with the flow of traffic, at around 65-70. Rush hour sucks.

[Hood Ornament]

Originally Posted by SL350

Define traffic. It only took one to rear end me on the way to the beach in Corpus a couple of years ago. He was doing 90 and I 65. Not much traffic but it still was not safe.

If it has not already happened to me I might agree with you.

I've been rear ended sitting still at a red light..... TWICE. Has nothing to do with speeds, it has to do with idiots not paying attention to what they're doing.

[YoDoc]

Then why do many places have minimum speeds?

[bmcdonau]

Originally Posted by JTM

I'm throwing the BS flag: There are plenty of people that still drive 55 everywhere, even in West Texas where the sign says 80, and their safety is only at risk because they think the left lane is where they should be.

Back to topic: I tend to keep my Grand Cherokee around 65mph and I follow the advice of an older gentleman when I encounter hills or overpasses. I just hold the throttle in the same place and just let the vehicle slow down as you go up the hill; as you head back down then regain your pace. This netted me 24 mpgs with a small lift and slightly over size tires while cutting across Northern New Mexico.

You must be a joy too drive behind. Drive a consistent speed for gosh sake, you can spare the 2/10ths of a mpg.

[tshelfer]

On an open highway, he's probably not too much of an impediment.

Here's another trick of mine, particularly useful when towing. When I start up a hill, the Jeep'll go to any extreme to maintain a constant speed - meaning often dropping from 5th to 3rd. I'll cut the cruise off and, by nursing the gas peddle a bit, can usually make a long grade with a speed drop of 5 mph at the outside, but keeping the tranny in 5th or 4th.

[DFW_Warrior]

I ride a motorbike that gets 37mpg while I am cruising at 85-90mph. So I don't sweat the slow stuff, I just usually go around it.

And as a former delivery driver in the DFW area, and a long time motorcycle commuter I can promise that there are tons of people driving 55mph on each and every freeway that don't end up dead. They are annoying as heck, so it is kind of hard to miss.

[Hood Ornament]

Originally Posted by YoDoc

Then why do many places have minimum speeds?

I've often wondered that myself as I used to sit on 635 going 5 MPH. Obviously it's a useless attempt at trying to keep traffic flowing at a reasonable rate.

[YoDoc]

I don't think 635 has a minimum, do they? I'm thinking more along the lines of the open freeways between places. That's where I normally see them.

[Hood Ornament]

Originally Posted by YoDoc

I don't think 635 has a minimum, do they? I'm thinking more along the lines of the open freeways between places. That's where I normally see them.

I can only think of interstates having min's, and last I checked, 635 is an interstate.

[STman]

Just a little fun with numbers here. If one drives 15k miles per year and gets 20mpg, every gallon they consume costs them $750 per year per dollar of cost. In other words at $4 a gallon, it will cost that person 3K per year, at $5 per gallon $3750. That's really not a huge amount of money.

If $4 per gallon is killing their budget, the bottom line is they can't afford to drive a gas guzzler. There are many cheap to operate fuel efficient cars out there, so if Mr. and Mrs. Jones say they're going to have to start eating beanie weenie because it costs so much to fill up their suburban, well it's pretty hard to have much pity on them.

[CB700SC]

Originally Posted by Ben Eberle

EFI goes "open loop" when the absolute manifold pressure goes above a certain point, it amounts to the same thing.
The mixture needs to go rich at high power mostly because a rich mixture can take a higher compression ratio without detonating than a lean mixture can. At part throttle, detonation is less likely so the mixture can go lean for economy. This allows a somewhat higher compression ratio for better cruise economy.
The rotton egg smell you smell when a car is passing or climbing a hill is from unburned hydrogen in the exhaust combining with sulphur that collects in a catylitic converter to form H2S. This is because in "open loop" mode, the mixture is rich. When the car is cruising in "closed loop" mode, the EFI constantly moniters the oxygen sensor in the exhaust and corrects the fuel mixture for a stoichiometric mixture.

Many cars also have a feature called deceleration fuel cut off. If the throttle is completely closed and the engine rpm is several hundred rpm above idle, like when you coast downhill, the fuel is completely shut off. I don't think many bikes use this because it causes riders to complain about abruptness as you roll on the throttle in a corner. I think some early BMW K-bikes had it but riders didn't like it.

You are assuming the less common manifold absolute pressure system. Most EFI systems use a mass air flow sensor and do not know or care about the manifold's absolute pressure.

Mostly because one intake backfire will kill a MAP sensor, but a MAF can survive multple such events just fine.

Originally Posted by Hood Ornament

I can only think of interstates having min's, and last I checked, 635 is an interstate.

It is not, however, a rural interstate. If it was, it would be posted 75mph and might have minimum speed postings.

Originally Posted by STman

Just a little fun with numbers here. If one drives 15k miles per year and gets 20mpg, every gallon they consume costs them $750 per year per dollar of cost. In other words at $4 a gallon, it will cost that person 3K per year, at $5 per gallon $3750. That's really not a huge amount of money.

If $4 per gallon is killing their budget, the bottom line is they can't afford to drive a gas guzzler. There are many cheap to operate fuel efficient cars out there, so if Mr. and Mrs. Jones say they're going to have to start eating beanie weenie because it costs so much to fill up their suburban, well it's pretty hard to have much pity on them.

All the cheap used cars got trashed by cash for clunkers or snapped up by people who saw this coming. If you are talking about new, do tell me how spending $15,000+ on a new car is affordable when a fractional increase in fuel cost for that Suburban (which may already have been paid off) isn't? Also, pray tell how long it would take them to break even at $5/gal gas with that new car vice the Suburban.

[Ben Eberle]

Originally Posted by Hood Ornament

I can only think of interstates having min's, and last I checked, 635 is an interstate.

A former DPS officer told me that unless otherwise posted, the minimum is 20 under in Texas, but it only applies to free flowing traffic conditions. Obviously, gridlock is not free flowing traffic, neither is pea-soup fog or ice.
Also, during peak traffic density times, all lanes are needed just to handle the volume of traffic, so during rush hour, there's no such thing as a "passing lane".
Laws may have changed since then.

[Ben Eberle]

Originally Posted by CB700SC

You are assuming the less common manifold absolute pressure system. Most EFI systems use a mass air flow sensor and do not know or care about the manifold's absolute pressure.

Mostly because one intake backfire will kill a MAP sensor, but a MAF can survive multple such events just fine.

Air flow divided by engine rpm = cylinder fill, the computer still has a point were it switches from stoiciometric to rich.
Some engines, such as the one in the Prius, do a lot of the throttling with cam advance/retard instead of the throttle butterfly so there might be a high manifold pressure even at reduced power.
Instead of choking off the airflow with a throttle butterfly to reduce power, the intake cam is run very retarded for super late intake valve closing. This throttles the engine with lower pumping losses and makes for a much lower low power and idle fuel consumption.
Or so I hear.

[CB700SC]

Originally Posted by Ben Eberle

Air flow divided by engine rpm = cylinder fill, the computer still has a point were it switches from stoiciometric to rich.
Some engines, such as the one in the Prius, do a lot of the throttling with cam advance/retard instead of the throttle butterfly so there might be a high manifold pressure even at reduced power.
Instead of choking off the airflow with a throttle butterfly to reduce power, the intake cam is run very retarded for super late intake valve closing. This throttles the engine with lower pumping losses and makes for a much lower low power and idle fuel consumption.
Or so I hear.

Again, the majority of EFI cars out there aren't running MAPs. They switch from closed to open loop based on throttle position alone. Usually wide open throttle or high percentage throttle; some of them also go open loop at idle. This is why many EFI cars are very easy to add forced induction to while maintaining the stock fuel control computer and simply chipping it. MAP-equipped naturally aspirated cars require much more than that, starting with completely tossing the original MAP in favor of another one that hopefully is electrically compatible.

[Ben Eberle]

Originally Posted by CB700SC

Again, the majority of EFI cars out there aren't running MAPs. .

Did I say they were? I simply meant to say that you can get a good approximation of manifold pressure with the info sent by a mass air flow sensor if the computer knows the engine rpm and throttle position.

[CB700SC]

Originally Posted by Ben Eberle

Did I say they were? I simply meant to say that you can get a good approximation of manifold pressure with the info sent by a mass air flow sensor if the computer knows the engine rpm and throttle position.

The computer on most cars still does not behave as you describe - it does not "see" manifold pressure in the first place, so it does not go "Oh, I need to go open loop now" based on that alone. It also doesn't go open loop based on air flow. It goes open loop based on throttle position and coolant/outside air temp.

[SL350]

It is kinda funny how some argue that it is safe/not safe to drive or ride slow on the freeway as though there is a definitive answer. There is not one. How many have told you that riding on 2 wheels is never safe? You can tell me all day that it is safe to go 30 mph below but I would not feel safe. I still might do it but I will spend more time looking at my mirrors than the road ahead.

[YoDoc]

Originally Posted by SL350

It is kinda funny how some argue that it is safe/not safe to drive or ride slow on the freeway as though there is a definitive answer. There is not one. How many have told you that riding on 2 wheels is never safe? You can tell me all day that it is safe to go 30 mph below but I would not feel safe. I still might do it but I will spend more time looking at my mirrors than the road ahead.

+1

I'm with you here. Cruising around out in the country where I learned to ride? Psshhh. Drive however slow you want. Driving in Dallas on a motorcycle, at speeds that force semis to brake/change lanes/actively avoid crashing into you? No flippin' thanks. Unsafe, unsafe, unsafe.

[Ben Eberle]

Originally Posted by CB700SC

The computer on most cars still does not behave as you describe - it does not "see" manifold pressure in the first place, so it does not go "Oh, I need to go open loop now" based on that alone. It also doesn't go open loop based on air flow. It goes open loop based on throttle position and coolant/outside air temp.

OK, I'll take your word for it but if going rich was based on throttle position alone, wouldn't the engine be too lean under low rpm situations? If you leave a car in fifth gear while climbing a hill, the low rpm can mean a high percentage of cylinder fill even though the throttle is not open very far.
I would think that the open loop switch over point would or should be engine rpm dependent.

[STman]

Originally Posted by CB700SC

All the cheap used cars got trashed by cash for clunkers or snapped up by people who saw this coming. If you are talking about new, do tell me how spending $15,000+ on a new car is affordable when a fractional increase in fuel cost for that Suburban (which may already have been paid off) isn't? Also, pray tell how long it would take them to break even at $5/gal gas with that new car vice the Suburban.

I'm not talking about new cars at all. That's part of the problem, people buying cars they can't afford so $4 a gallon gas hurts them. I bought a used Honda a few years ago. Paid 5k for it, ran like a top from the day I got it all the way to 250k miles when I hit Bambi and the insurance company totaled it. Got 38mpg on the hwy. What some need to say is "I can't continue living beyond my means with $4 gas"