Maximizing mileage with 1.4T

[RichieRocket]

My commute has a lot of stop-go. As others have said abotu short-shifting, I have been re-tuning my driving style to short-shift much earlier. So in a normal, no rush situation,
1st to 2nd 2300~2500 rpm
2nd to 3rd 2000
and the others at less than 2000

I've found even at 1500 rpm, you can still accelerate 'mildly' by getting the boost up a bit, to 3-4 psi.

The other thing I've been trying out is where to keep the boost while short-shifting.
Is it better to keep the throttle so you get ambient pressure in the intake, 0 psi or on the boost a bit, 2-3 psi?
The turbo is supposed to make the engine more efficient, the intake does not have to pull the air past the mostly closed throttle plate...the turbo is pushing it in.

I'm also shutting down during long red lights(we've had this discussion before, some people are strongly opposed to this ).
I only do it if the timing is right, like when you roll up just as the light changes to red. This turns out to be only a half-dozen times per week. Some of our lights, with left turn lanes and stuff go 90 seconds to come around...

 

[Danny5]

Some of the steps here are classic hyper-miling.

Shutting down a car at stop lights is a common technique. In extreme temperatures, this may not be feasible.

Another good technique is super coasting. Get up to 5 over the speed limit and then shift into neutral. Resist the urge to get back in gear for as long as possible.

Some people can get 100mpg out of their prius by shutting down the car while super coasting. That is just nuts, since it would make accident avoidance an issue.

I shift all gears before 2000rpm, not just first. 6th gear by 35mph will get you 70mpg!

If you travel a lot on freeways, you can maximize mileage by staying behind large trucks. I certainly wouldn't advocate breaking the 2second rule, but this is a good way to reduce your frontal area by staying in a trucks low pressure wake.

Would like to see more tips, not just limited to motor type, but applicable to all cars!

 

[keto06]

Shutting down a car at stop lights is a common technique. In extreme temperatures, this may not be feasible. (not personally a fan)

I shift all gears before 2000rpm, not just first. 6th gear by 35mph will get you 70mpg!

If you travel a lot on freeways, you can maximize mileage by staying behind large trucks. I certainly wouldn't advocate breaking the 2second rule, but this is a good way to reduce your frontal area by staying in a trucks low pressure wake. (Im not tailgating, Im drafting!)

ive heard this before, and while it may work in the 1.4T, dont most cars require more throttle and therefore more fuel by short shifting to accellerate vs keeping it in a lower gear with less throttle?

 

[wingman]

Being a truck driver I have been through many classes for driving safely and some of them include the fuel economy discussion.

Coasting in neutral will not yield better mpgs. Same as sitting at a light in neutral. A slow deceleration, with foot still on right pedal gradually lifting and slowing as slowly as possible. Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy - Popular Mechanics Downshifting also helps.

Short shifting-Good. You can shift when the car tells you which is about every 6-7 mph. I hammer 2nd, straight to 6th as long as Im above 40 mph. This is just my lazy way of not shifting so much. I havent tried for a maximum mpg, but driving the way I described I hit 34+ in the city alone. Havent really had it on a long stretch of highway yet.
Look ahead! Scanning close and as far as you can see for signs of slowing traffic, or stale red or green lights. You can adjust your speed from far away and change or maintain your speed.

Cruise control-debatable. I have heard you get better mpgs without it, especially in the hills. The car cant anticipate hills, but the driver can.

Drafting-Thats a big 10-4 cmon! We run in packs for that very reason. But there are wrong ways to do it. You cant just jump behind and be like "hey I'm drafting!" You have to maintain the speed of the vehicle in front of you and stay in the slipstream. If you are constantly having to speed or slow behind a semi trailer or car, you might as well go around and maintain a steady speed of your own.

Shut it down if your gonna be sitting there a while. Just remember to have your lights on if its dark and theres no one behind you!

 

[Danny5]

Correct me if I am wrong, but the lights won't shut off unless you open a door.

Coasting in neutral yields HUGE jumps on my MPG meter. It is different for every car. For instance, in my Subaru, far less gas is supplied to the motor when off throttle in gear than while idling. I have not seen evidence of that in our Sonic.

Downshifting vs. lugging. I saw this discussed by Click & Clack, and lugging your engine always provided better mielage, even if your accelerator was down furthur than it would be if you had downshifted.

 

[Eric Smit]

By the way, Prius drivers can get 100 mpg by using a technique called pulse and glide. there is no accident avoidance issues in a Prius because it shuts the engine off on decel as part of the hybrid technology. You can do it in your sonic, which will be a danger to accident avoidance as such;
1) Accelerate to 65.
2) Clutch in.
3) Shut the car off, but make sites it's in ACC so your steering doesn't lock.
4) Decelerate to "55." I used quotes because it's hard to tell the speed when your speedo is digital. D'oh!
5) Let your clutch out to restart the car.
6) Repeat.

 

[AndrewGS]

I just started shifting before 2K RPM today. We'll see if the traffic buildup behind me pays off at the pump.

 

[wingman]

Correct me if I am wrong, but the lights won't shut off unless you open a door.

Coasting in neutral yields HUGE jumps on my MPG meter. It is different for every car. For instance, in my Subaru, far less gas is supplied to the motor when off throttle in gear than while idling. I have not seen evidence of that in our Sonic.

Downshifting vs. lugging. I saw this discussed by Click & Clack, and lugging your engine always provided better mielage, even if your accelerator was down furthur than it would be if you had downshifted.

I keep my lights on auto, and if I turn the key completely off, lights go off.

 

[RichieRocket]

ive heard this before, and while it may work in the 1.4T, dont most cars require more throttle and therefore more fuel by short shifting to accellerate vs keeping it in a lower gear with less throttle?

keto06, yes, the higher gear needs more throttle, BUT the rpms are lower so the airflow (and therefore fuel flow) into the engine will be similar. The engine still needs to produce the same power for a given road speed, but the engine is more efficient at lower rpms/higher throttle.
I posted up an article on Brake Specific Fuel Comsumption (BSFC) a while back: http://www.sonicownersforum.com/forum/t773/
In the charts they have, the engine is most efficient when it operates in that red island in the middle. For our cars, that's about 1500-2000 rpm and 3/4 throttle. Of course you can't operate at that point all the time, but short-shifting keeps the engine running close to the efficiency 'island'. It's all about keeping the friction low and reducing flow restriction of the intake air.

The main question I had for the 1.4T is how much boost to accelerate with for max efficiency. No one answered that. -2, 0, +2 psi?
I was looking for a turbo BSFC chart, but can't find one...

Some of the steps here are classic hyper-miling.

Shutting down a car at stop lights is a common technique. In extreme temperatures, this may not be feasible.

...

I shift all gears before 2000rpm, not just first. 6th gear by 35mph will get you 70mpg!

We have had discussions about shutting down and auto stop-start systems like they have in Europe a while back. A few people were strongly opposed to it...they believe the old myth about re-starting takes so much fuel you could idle the car for a 'couple minutes'...LOL! Not on modern EFI cars!

Danny5, you may have misunderstood my post, I do try to shift below 2000rpm in all gears also, not just first. The rpms climb quickly in first, so I over-shoot 2000rpm. I'll try to shift 1st-2nd sooner...

 

[bryandrews78]

I also have been trying to experimenting with 2nd gear starts. I live in an area with a lot of hills so it not possible all the time. I have a hard time telling if it is saving on gas or if the engine is just breaking in. I would be interested if anybody is having any success with this.

 

[Papasonic]

With all of the emphasis on fuel economy; Isn't there more concern with engine wear and damage caused by lugging the engine. Most of these efficiency techniques, including short shifting, and operating in too high of a gear ratio in relation to road speed which places extreme loads on engine internals. My concern is that there has already been piston failures in the 1.4 engine, and this practice of engine lugging for the sake of economy may not be worth the fuel savings. I'm all for saving fuel, but not sacrificing the engine to achieve that goal.

Papasonic

 

[RichieRocket]

With all of the emphasis on fuel economy; Isn't there more concern with engine wear and damage caused by lugging the engine. Most of these efficiency techniques, including short shifting, and operating in too high of a gear ratio in relation to road speed which places extreme loads on engine internals. My concern is that there has already been piston failures in the 1.4 engine, and this practice of engine lugging for the sake of economy may not be worth the fuel savings. I,m all for saving fuel, but not sacrificing the engine to achieve that goal.

Papasonic

Papasonic, well like many things in life, it depends...

What I'm talking about, I'm accelerating mildly, ~30% throttle, boost pressure of 0.0 to 1.0 psi. So I would not call that lugging. The temperatures and pressures are still low. If I need to accelerate harder then I just rev it a bit higher.

If I were 100% throttle from 1000 rpm, and pushing 12 psi boost at 1800 rpm, then yes, I would call that lugging. I don't think anyone here is doing that...

On the piston cracking issue, I may not be up on the latest info. Is there new info?
http://www.sonicownersforum.com/forum/t1069/
This thread said it was only on early 2011 Cruze, either a manufacturing defect in the piston or oil getting into the intake from the PCV...

 

[RichieRocket]

I zoomed in on my RPM vs. Speed chart to show the short-shift rpms. I added orange downward arrows at the shift points if you shift at 2000 rpm each shift. If anyone wants a copy of the spreadsheet to play with the shift rpms, pm me and I can send you a copy.

The reason it's tough to shift 1st to 2nd before 2000 rpm is that the gaps between gears are bigger between the lower gears. So if you shift 1st to 2nd at or below 2000, you end up down near 1000 rpm.

1st-2nd 2000 - 1060 rpm 940 rpm drop
2nd-3rd 2000 - 1280 rpm 720 rpm drop
3rd-4th 2000 - 1490 rpm 510 rpm drop
4th-5th 2000 - 1550 rpm 450 rpm drop
5th-6th 2000 - 1650 rpm 350 rpm drop

 

[Papasonic]

I guess my definition of lugging an engine is when the vehicle will not readily accelerate in the chosen gear ratio. I'm ok with allowing an engine to work, but the gear chosen should match the load encountered.

 

[wingman]

In the tips that I posted, any of those techniques would not involve lugging. Just wanted to clarify that. Sometimes I short shift and have found if I am above 1200 rpm after the shift with a mild throttle roll on, no lugging.

 

[RichieRocket]

I guess my definition of lugging an engine is when the vehicle will not readily accelerate in the chosen gear ratio. I'm ok with allowing an engine to work, but the gear chosen should match the load encountered.

I think of 'lugging' as high load at low rpm. Like 100% throttle at 1500 rpm

Since we are talking about low throttle, 'mild' acceleration, I don't consider that lugging. I am only using a small portion of the available power at that condition.

Keep in mind this is not aggresive/race track driving, we are going for fuel economy. I'm accelerating at less than average rate. If you want to accelerate at a certain rate, say:
25% throttle in 2nd gear, 2500 rpm, -4 psi boost
Why not just short shift to 3rd and accelerate at the same rate with:
35% throttle in 3rd gear, 1600 rpm, 0 psi boost

The short shift will still give you same desired mild accel, but at a more efficient running condition.

If you suddenly need to accelerate, then just down-shift. Of course one of the requirements of using this technique is paying more attention to the raod conditions. If you anticipate traffic, passing, merging, climbing a hill, etc.......then do not short-shift! Save it for when things are calmer...