Few questions for easy, $0.00 modifications

[FLAteam]

Hi, I'm new and I finally decided to join the forums. I drive a 96 Civic DX hatchback, automatic, in Florida (no problem with having a cold engine here). I average 32 mpg (EPA 29-36). Here's a few things I've done to increase my fuel economy:

Driving technique (slower accel, less braking)
Tire air pressure 40psi
General maintenence (spark plugs, wires)
Wash/Wax
K&N drop-in air filter
Slow fuel filling, filling when cold
Synthetic oil changes every 3000 miles

I believe in the "miles per dollar" method, so I'm not out to get high mpg just for the sake of high mpg, but rather to save money all around. I don't want to go spend $400 on some VX wheels with LRR tires just so I can get 1 mpg or $200 on an aftermarket header just so I can get another 0.5 mpg. It just doesn't make economic sense in my opinion.

My questions include:

1. What more can I do that would cost little to no money to get higher mpg? I'm not very technical, but I can do basic stuff like oil changes.

2. Would coasting in Neutral (my car is automatic!) help?

3. Would removal of the exhaust manifold heat shield help?

Thanks!

[EH3]

1. drive slower. install lower grill block.
2. NO
3. NO

[civic94]

1. remove weight from car, go on diet yourself
2. no, but putting it in N when car is stopped will help a bit, then go back to D when a green light comes
3. exahst heat shield is kinda heavy, it might benefit you

[FLAteam]

Well, I tried yesterday and today to drive at a lower top speed and put it in neutral at stop lights. I finally got 36mpg, a little above actually, based on 2 gallons of gas fillup. Thanks!

[PaleMelanesian]

Tire pressure even higher will help.
Coasting in Neutral will absolutely help mileage.
Exhaust manifold shield - no difference.

[RoadWarrior]

Well on the miles per dollar front, you could stretch your oil changes to 10,000 miles or every spring, since you're using synth.

[My Goal: 55MPG]

Well on the miles per dollar front, you could stretch your oil changes to 10,000 miles or every spring, since you're using synth.

Maybe get rid of the K&N, go with stock. In some of my cars, I have actually lost MPG because of a K&N. Increase your operating temperature by a couple of Deg. That will help a bit. Under car aerodynamics?, Under driving your accessories?

Hope this helps :cool:

Alex

[VetteOwner]

Well, I tried yesterday and today to drive at a lower top speed and put it in neutral at stop lights. I finally got 36mpg, a little above actually, based on 2 gallons of gas fillup. Thanks!

lol only 2 gallons? i can fit that much in the filler neck of my car...
go for at least half as tank then see what it is.

thats NOT a very accurate measurement at all, more fuel you put in with higher milleage number more accurate it is:D

[dosco]

Why the difference in opinion regarding coasting in "N" on an automatic trans?

[RoadWarrior]

Because most cars since the early 90s have had injector shutoff above certain RPM when the throttle is closed. Ergo, you could be using more gas idling the motor than letting it engine brake. Also if your tranny doesn't run the pump in neutral (most do) then you might burn the fluid when you put it into neutral when it's warm at highway speed.

IMO in most areas traffic conditions are such that you'll never get to coast very far in neutral anyway, and also aero drag at higher speeds seems to slow you quicker than the motor does, so unless you're in the wide open lonely spaces with straight roads you can see down for miles you'll probably get as much benefit out of the injector cut as you get out of neutral coasting.

[beatr911]

Grill block. Use discarded political sign material spray painted black.

[FLAteam]

I was under the impression that when an automatic shifts from N to D, it starts at 1st gear. Thus, when crusing at higher speeds in N and needing to gain speed again, you'd start at 1st gear (at high rpm, wasting fuel) when putting it back into D, negating any effects of gained fuel economy.

When coming to a stop, you'd rather keep going in D because you can engine brake, saving your brakes, because you know you're going to stop.

Thus, it seems like the only appropriate time to shift into neutral to save gas is when fully stopped at a red light. I guess you could also put it into Park? At the very least, you won't be using your tail lights.

[BamZipPow]

Neutral with the parking brake on... ;)

[PaleMelanesian]

Coasting in Neutral will still use gas - at idle level. In some cases, leaving it in gear will trigger fuel cut. But that will also slow you down faster. You have to balance the two as you drive.

Neutral with the engine running is 100% fine. No problem. It's neutral with the engine off that MAY damage an automatic transmission. Some are ok, some are not. If the owner's manual allows flat 4-wheel towing, then it's fine.

If you rev-match before shifting back into drive, there should be no jolt or anything - smoother than a system-controlled shift.

Coasting in neutral, engine on or off, is a critical part of getting super-high mileage. Pulse & Glide.

Grill Block is a good one. Use anything and everything that will fit. Some people use foam pipe insulation stuffed in the slots.

[dosco]

Because most cars since the early 90s have had injector shutoff above certain RPM when the throttle is closed. Ergo, you could be using more gas idling the motor than letting it engine brake.

In this case, how is a manual trans better? Is there no injector shutoff in a car with a manual transmission?

In other words, if we have 2 cars that are identical except the transmission, putting the trans in "N" and coasting will yield no benefit whatsoever. Correct?

This means there are - maybe - 2 prime benefits to having a manual trans:

1. Ability to pick shift points to maximize FE.
2. Lower mechanical losses.

(personally, I prefer the stick shift because it's more fun to drive)

[PaleMelanesian]

3. you can bump-start a manual.

[theholycow]

I was under the impression that when an automatic shifts from N to D, it starts at 1st gear.

Mine has never done this, and I doubt any would. It should go to an appropriate gear. I've often shifted between N and D at every speed up to at least 75 and never had it enter D at 1st gear. I've done it in at least 7 different vehicles, probably more.

Even if you found one that does, it would immediately shift to a more appropriate gear, before you even had a chance to apply the gas pedal.

When coming to a stop, you'd rather keep going in D because you can engine brake, saving your brakes, because you know you're going to stop.

Saving brakes is a negligable savings. How much brake life do you expect to save? Could you get 10% more brake life? Brake service generally costs between $50 and $200 and lasts between 20,000 and 100,000 miles...

Most automatic transmissions I've used won't use a low enough gear for engine braking when in D. However, if yours at least keeps the engine above 1000 rpm while coasting in D, you'll most likely get DFCO (Deceleration Fuel Cut Off), meaning no fuel is used during that time. If it has a towing, power, or sport mode, it might downshift more aggressively; I've been experimenting with switching to "Tow/Haul" mode in my truck while decelerating but it's not helping, I have to just shift it down to 3 and 2 myself.

Thus, it seems like the only appropriate time to shift into neutral to save gas is when fully stopped at a red light. I guess you could also put it into Park? At the very least, you won't be using your tail lights.

Agreed.

If you rev-match before shifting back into drive, there should be no jolt or anything - smoother than a system-controlled shift.

Wouldn't rev-matching waste gas? The torque converter always buffers the N->D shift comfortably for me.

Grill Block is a good one. Use anything and everything that will fit. Some people use foam pipe insulation stuffed in the slots.

I'm new here, can you direct me to a thread or document about grill blocking? I've seen it in a few posts and I'm curious as to how and why it helps.

In this case, how is a manual trans better? Is there no injector shutoff in a car with a manual transmission?

There is injector shutoff (DFCO). A manual transmission allows you to use DFCO much more easily.

In other words, if we have 2 cars that are identical except the transmission, putting the trans in "N" and coasting will yield no benefit whatsoever. Correct?

Doing so requires fuel usage to keep the engine idling. I prefer DFCO to keep it from using any fuel, but I have not yet experimented with a pulse+glide technique, where N would probably be more appropriate.

[dosco]

I'm new here, can you direct me to a thread or document about grill blocking? I've seen it in a few posts and I'm curious as to how and why it helps.

Use the search function. Basically it is an aerodynamic modification to "block" the airflow into some or most of the front end grill. Many/most cars have more duct area (cross sectional area of the grill inlet) than they need for normal use.

There is injector shutoff (DFCO). A manual transmission allows you to use DFCO much more easily.

Doing so requires fuel usage to keep the engine idling. I prefer DFCO to keep it from using any fuel, but I have not yet experimented with a pulse+glide technique, where N would probably be more appropriate.

So what you're telling me is that when I'm driving on the highway in my '99 Camry and take my foot off the gas, that the engine is essentially "off?" Not sure I buy that because I would expect MUCH more engine drag and therefore deceleration.

The next question is how is it "easier" to use DFCO in a stick vice an automatic? Are you suggesting that one would downshift at highway speed to take advantage of the DFCO?

Another question is about pulse and glide. Where, exactly, is the efficiency gain made? Is the idea to run the engine at its most efficient RPM followed by use of the cutoff?

Let me state that I've started to experiment with shifting to "N" where it seems logical. I have some data from my first fill-up, but I think I screwed the pooch b/c I didn't top off to "1 click" (my usual fill-up procedure) and my estimate of fuel used could be wrong. Reason I think this is that I do have data from last year indicating my typical mileage was 27 to 31 MPG, whereas my most recent data show 25 MPG (although the higher mileage was with August temperatures in the metro DC area).

[theholycow]

So what you're telling me is that when I'm driving on the highway in my '99 Camry and take my foot off the gas, that the engine is essentially "off?" Not sure I buy that because I would expect MUCH more engine drag and therefore deceleration.

It took me a while and a lot of discussions before I quite believed it. I assumed there would be more noise/vibration from the engine. However, if you think about it, everything is still running, there's just no fuel being injected.

Unless you have an extremely low top gear, there will be little drag just letting the wheels turn the engine. Think about all the torque required for the engine to turn the wheels in that gear; from the wheel's point of view, it's very easy to turn the engine.

This is why people trying to start the engine by rolling the car and popping the clutch use 3rd gear instead of 1st, and why you park a manual transmission in 1st instead of 3rd, 4th, or 5th.

The next question is how is it "easier" to use DFCO in a stick vice an automatic? Are you suggesting that one would downshift at highway speed to take advantage of the DFCO?

I've never feared shifting between N, D, 3, 2, and 1 on the highway. I've never driven a Camry, but I have driven a Tundra. I don't remember if I've tried it in the Tundra though I certainly wouldn't be afraid to. I seriously doubt Toyota would expose themselves to lawsuits and recalls to save five minutes worth of writing code or designing the valve body.

If it's a floor mounted shifter, you can probably move between D and N without pressing the button on the shifter. Consider that it's common for someone's elbow to accidentally knock it into N (as I once did in my mom's Ford Probe in 1988, scaring her since she was afraid to shift between N and D at highway speed); they would have required you to press the button if it was dangerous, as they require to shift out of P or from N to R.

However, I doubt that you'll need to at highway speeds unless your top gear is super tall. Below 1000 rpm is probably the point where DFCO quits, so as long as you're coasting in gear above 1000 rpm it's probably in DFCO mode. With an auto, if the torque converter isn't locked, then you'll have to coast faster to keep it above 1000 rpm than with a manual or an automated manual such as a SMT/DSG. I doubt there's any vehicle that won't keep it above 1000 rpm at 65 mph.

Sorry I can't answer any question about pulse & glide, I could only offer an educated guess. I need to learn about it too. I've intuitively done it sometimes, though.

[dosco]

This is why people trying to start the engine by rolling the car and popping the clutch use 3rd gear instead of 1st, and why you park a manual transmission in 1st instead of 3rd, 4th, or 5th.

I understand all that, no problemo.


I've never feared shifting between N, D, 3, 2, and 1 on the highway.

Not sure if you read my long-winded post, but I've been experimenting with shifting to "N" from "D." No problem.

My question is why do you think it is "easier" to employ DFCO with a stick rather than an automatic?

[PaleMelanesian]

A grill block helps in several ways.
- Faster warmup time - a cold engine burns much more fuel.
- better aerodynamics
- warmer intake air - usually gives you better fuel economy.
See this post (http://www.cleanmpg.com/forums/showpost.php?p=85834&postcount=31), click "my rides" for pictures of mine.

Some automatics are smoother shifting from N to D. My minivan's is rough - it revs up above 2,000 and then settles to 1500, so I rev-match to 1500 1/2 second before. Minimal fuel, maximium trans life.

Pulse & Glide - Neutral is a must. Leaving it in gear is completely wasting your time. Engine-off is even better, but only if your auto can be 4-wheel flat-towed (check the manual).

[theholycow]

Thanks for explaining the grill block. I figured it would affect aerodynamics, although I wasn't sure whether it would help or hinder; but I didn't think of the engine efficiency gains.

It's interesting to see where your comfort level and safety priorities are. Mine are quite the opposite. I would accept a rough N->D shift, considering that the torque converter is taking all the abuse and is made for such abuse; but I am totally not comfortable with (on a regular basis) shutting off my engine while driving in neutral...

[BBsGarage]

Thus, it seems like the only appropriate time to shift into neutral to save gas is when fully stopped at a red light. I guess you could also put it into Park? At the very least, you won't be using your tail lights.


I'll probably answer my own question, but can some one tell me why this is so?

In my own feeble mind the RPM's are lower when left in gear then when in Neutral, so how can it be using more fuel? Is it because it is under a load?

[PaleMelanesian]

On my minivan, it's already had the transmission replaced under warranty, and I hear this is the most common failure for this model. I'm being extra careful.

On my daily driver manual civic, it's already at 160,000 miles and still going strong, so I don't worry about wear. Safety - no power steering to begin with, and the brakes are good for several emergency applications before the boost runs out. I've played a lot with it on back roads and I know what the results are. If a situation does come up, I'm ready.

[theholycow]

I'll probably answer my own question, but can some one tell me why this is so?

In my own feeble mind the RPM's are lower when left in gear then when in Neutral, so how can it be using more fuel? Is it because it is under a load?

You did answer your own question. RPM alone does not determine fuel usage. Load, power created, throttle position, air/fuel ratio, temperature, and some other variables I can't remember off the top of my head are all part of it.

I eagerly await my state tax refunds or my economic stimulus check so I can buy a ScanGauge II and just get a direct reading on fuel rate in gallons per hour...

[dosco]

You did answer your own question. RPM alone does not determine fuel usage. Load, power created, throttle position, air/fuel ratio, temperature, and some other variables I can't remember off the top of my head are all part of it.

I eagerly await my state tax refunds or my economic stimulus check so I can buy a ScanGauge II and just get a direct reading on fuel rate in gallons per hour...


Just use this link for an explanation. It was exactly the info I needed.


http://www.autospeed.com/cms/A_110216/article.html

[theholycow]

Just use this link for an explanation. It was exactly the info I needed.

http://www.autospeed.com/cms/A_110216/article.html

Nice. That puts some additional science and math behind some of my own experiments and the theories that spawned them.

Also, it says something helps explain the efficiency of GM's gasoline direct injection (http://en.wikipedia.org/wiki/Gasoline_Direct_Injection) V6 that's currently in the Cadillac CTS and will be in the new Camaro:
Diesels, which we’ve not mentioned here, are much more efficient at low loads because they don’t have a throttle restriction in any type of driving – low loads are catered for by just reducing the fuel that’s injected.

[FLAteam]

Well, I tried a few techniques today. I drove about 110 miles and...

-I followed a semi truck @ 70mph, 2-3 car lengths away for a good 30 of those miles. Didn't seem to help much.
-Drove only up to 70mph, most of the time at 65mph.
-Put it in Neutral with engine on for a few of the downhills. Seems to really help, especially if going less than 60mph. I think my engine likes to brake a lot for me.
-Went up to 70 on the uphills.
-Engine off Neutral (on my automatic!) twice. It was kinda scary. Found out I don't have power steering. Seemed to help, but not much more than engine on Neutral (but I wouldn't know...my speedometer was at 0 and I don't have a Scangauge).

So what's the final verdict on going up and down hills? It seems like when you go up a hill, you gain traction due to your going against gravity, so you use every bit of the gas you burn, as opposed to downhill where you go with gravity and possibly don't have as much grip, burning fuel and not transmitting all that power to the road.

Also, maybe the air you have to move is less when going uphill. After all, now there's less air under you as you go up (and more pavement under you), so air has to travel over you. When you go downhill, it seems that you'd be affected by both wind above and below, making you waste more gas going against the wind.

[Pete]

FLAteam,

A couple of things not already mentioned unless I missed them...

Regular wheel alignments will help keep everything running true. Saves tyres as well as fuel.

Take out everything you are not using on that trip. Every pound costs fuel to transport so gut the car as far as you can.
Even taking out the street directory if you don't need it on that trip.

Good luck , Pete.

[theholycow]

You should have 100% traction/grip whether you're going up or downhill, under normal conditions. If you don't, you're either racing or you've got something very broken.

When you're going downhill, if you've got a modern engine and it's above 1000 rpm, it's using zero fuel. The only difference between coasting downhill in gear and coasting downhill in N with the engine shut off is that you'll gain a little more speed doing the latter, due to the road not having to turn the engine and operate the accesories. The energy used to recharge the battery after restarting is probably slightly less than the energy saved.

I disagree with your idea about aerodynamics. Your vehicle displaces exactly the same volume of air going up or down, has the same ground clearance and the same drag coefficient, and the same amount of pavement under it. Remember, the road's angle changes along with the vehicle's angle; so it's not like the vehicle pointed up will catch more air under and less air over or something like that.

Momentarily, when cresting the top of a hill or in the bottom of a valley, the vehicle's angle relative to the road changes, and at that point the balance of air going over vs. under changes momentarily; coming over the top, the bottom of the vehicle parachutes a bunch of extra air, while in the valley entering the uphill the ends of the vehicle are closer to the road and let less air under.

[PaleMelanesian]

-Engine off Neutral (on my automatic!) twice. It was kinda scary. Found out I don't have power steering. Seemed to help, but not much more than engine on Neutral (but I wouldn't know...my speedometer was at 0 and I don't have a Scangauge).


You should turn the key back to the ON position as soon as the engine stops! That's very unsafe not to! Your ABS, airbags, and any other electrical systems are turned off at that time! Besides, you're not registering any of the miles traveled, so your numbers aren't reflecting reality. ;)

[Mr. Pig]

In my Cavalier, per my ScanGuageII, when coasting in drive at around 55mph I see around 55-60 mpg, if I pop it in neutral I see around 125-130 mpg. I'm having trouble understanding how the fuel cutoff could be using zero fuel. If there was no fuel at all, the engine would die and effectively have to be bump started to get going again, which isn't possible in an auto. Perhaps it is just cutting fuel to a point that it is running super lean? Or is my GM vehicle just not the norm?

[PaleMelanesian]

The Scangauge is likely not reporting it correctly. It's only guessing - there's no code in the OBD-II protocol for fuel cut. It just guesses by the light load and rpm.
If it's in gear, your car's momentum is driving the wheels, which in turn are rotating the engine. That's how it stays turning with no fuel. If you're in neutral, the engine will require fuel to keep running, so there's no fuel cutoff in that case.

[theholycow]

In my Cavalier, per my ScanGuageII, when coasting in drive at around 55mph I see around 55-60 mpg, if I pop it in neutral I see around 125-130 mpg. I'm having trouble understanding how the fuel cutoff could be using zero fuel. If there was no fuel at all, the engine would die and effectively have to be bump started to get going again, which isn't possible in an auto. Perhaps it is just cutting fuel to a point that it is running super lean? Or is my GM vehicle just not the norm?

What was the tachometer reading?

If it's still in gear and the wheels are turning the halfshafts are turning the diff is turning the driveshaft is turning the transmission is turning the crankshaft, what's the problem with reducing the fuel until zero fuel is injected? As long as fuel is resumed before the RPM drops below idle speed, no restarting will be required.

A Cavalier isn't exactly the showcase of all the latest in modern technology; I suppose it's possible that it might not support DFCO, though I'd guess that it's more likely that it just wasn't revving high enough. 1000 rpm is the number everyone says for DFCO and it's definitely the borderline point for my VW, but I'm not sure that it's the same in all vehicles.

Pale: I hope your guess is wrong. I am planning to buy a SG and I'm counting on it being able to report actual fuel consumption volume. If it can't, I need to come up with some other gauge to do it.

[PaleMelanesian]

Test for DFCO: Do a controlled coast-down in gear with the engine on. Mark the distance/time results. Do it again in gear with the engine turned off. If the results are similar, you have DFCO. If the engine-on coasts longer/farther, you don't.

[RoadWarrior]

Ford EEC computers are meant to do it down to 1800 rpm on auto transmissions, I guess that's about where the transmission stops driving the motor.

[theholycow]

1800 is pretty high for DFCO to quit.

Mmmmm.....1800.....
http://tbn0.google.com/images?q=tbn:MNoQJDc28djnEM:http://www.tequilasource.com/bottles/pics/1800-anejo_4479_r2.jpg

[FLAteam]

well, I just filled up 10 gallons and got around 35.5 mpg. However, i filled it up super-slowly...so maybe next time it'll be higher.

[theholycow]

I found a free mod that is very easy and might help hypermilers with automatic transmissions. The link is about tuning for racing, but the same mod can be applied to us with one minor change:
http://www.autospeed.com/cms/A_1304/article.html

It says to adjust the cable so that your transmission will be more responsive, downshifting with less gas pedal input. However, if you adjust it in the other direction, you'll be able to use larger throttle opening at lower RPM.