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Old 01-18-2013, 01:23 PM   #1
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My fellow gas-saving penny-pinchers, I've recently opened my world to the realm of hypermilling and the concept of P&G truly intrigues me. I've done many searches on a few forums and haven't come up with some straight answers to a few of my questions. Don't get me wrong, I've gotten answers, but they were rarely consistent between communities. I hope the expertise of this community will be of most help.

First, let me start off by saying I own a 2007 Hyundai Tiburon. It's a V6 automatic, and it's naturally aspirated (no mods). According to the EPA it can get an estimated 19/27 MPG. On a weekly basis, I have about 80-90% city driving. In my old car I got 29-31 MPG in a car that was only rated 28 on the highway. My goal is to do the same with this Tiburon. To be specific, my goal is 28 MPG average!

EOC does not thrill me, in fact it scares the bejesus out of me. xP
I wouldn't mind, however, to attempt to do a neutral coast. I actually did it today by accident. I was gliding down a hill with a red light at the bottom that I was almost guaranteed to have to stop at. When I got there, the lights immediately turned green and I had little choice.

And now, the holy grail of all my questions. The question that begs all other questions:
While switching into the pulse phase, are there any repercussions from putting an automatic transmission into D while the car is moving?

Is it necessary to "rev match" or rev the engine at all before transitioning back into the pulse phase?

If the need were to arise, would it be okay to rev the engine before putting it into drive in order to make an evasive maneuver?

In reference to cooling of the engine and tranny, are there any major problems with this while coasting? I use the Torque app on my phone to see real-time data, but my car does not support a tranny oil sensor, so monitoring this is almost completely out of the question.


I know these are a lot of questions, but I have a feeling that you will be the most-knowledgeable about this subject. Thank you for your help towards this topic.
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Old 01-18-2013, 02:40 PM   #2
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You should watch for fuel cut off when in gear and decelerating like in the case you had going to that red lights downhill. It's always good to rev match the engine when putting it in gear if you're moving, remember it's really a clutch with a friction surface that's getting the abuse so the closer you are to the correct speed the less wear there will be.
I have always then a proponent of reducing engine friction and drivetrain friction first so look into Teflon and graphite and Moly additives to your oil. Second would be combustion enhancers, like STP gas treatment, acetone etc. Since I stopped using acetone and Torco GP7 my tank averages have dropped from the low to mid 40 mpg to the high 30's.
Pump up the tires for sure, park facing out so you can start and go when the engine is cold. You take a big hit on mpg if you don't get moving, even slowly, right away.
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Old 01-19-2013, 10:20 AM   #3
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You should watch for fuel cut off when in gear and decelerating like in the case you had going to that red lights downhill. It's always good to rev match the engine when putting it in gear if you're moving, remember it's really a clutch with a friction surface that's getting the abuse so the closer you are to the correct speed the less wear there will be.
I have always then a proponent of reducing engine friction and drivetrain friction first so look into Teflon and graphite and Moly additives to your oil. Second would be combustion enhancers, like STP gas treatment, acetone etc. Since I stopped using acetone and Torco GP7 my tank averages have dropped from the low to mid 40 mpg to the high 30's.
Pump up the tires for sure, park facing out so you can start and go when the engine is cold. You take a big hit on mpg if you don't get moving, even slowly, right away.
Fuel cutoff is occurring when in gear and decelerating. However, with the increased engine breaking, I've found that there is more fuel economy gained when I let the engine idle down a hill in neutral.
I don't understand how/why but the Torque app says that there's also a small period of fuel cutoff directly after shifting into neutral. Is this actually happening, or a malfunction of the software?

I've not heard of these additives being in oil. Are they something you buy separately, or are they something that I should be looking for when buying the oil itself?

I've used fuel treatments before on other vehicles, but after calculation, I found that the financial gain was quite minimal (<$1). I will try it on this new vehicle for a few tanks to make an honest comparison.
Btw, isn't GP-7 for two strokes?

As for tire pressures, I monitor them closely on a weekly basis. I don't, however, over-inflate them (I assume this is your suggestion). Mfr suggests 32/35 (F/R). What would be a relatively safe compromise for over-inflation?
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Old 01-19-2013, 03:35 PM   #4
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Acetone 3-4 oz per 10 gallons in your gasoline
2.5-3 cc Torco gp7 to 10 gallons in your gasoline
Teflon graphite moly in the oil, if you can find decent additive packages Slick50 gave me good results but their formulation has changed over the years.

Tire pressure from the door sticker will give you a comfortable ride but if you set them closer to the max sidewall pressure you will see a good increase in mpg, just need to find what pressure you are comfortable with in terms of ride quality. Typically on a long trip on smooth roads you can go a lot higher without suffering much. If you drive on very bumpy roads you don't have much choice but to ride a little softer. Is plenty of discussions hear about how high some of the guys are pumping their tires up.
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Old 01-19-2013, 06:39 PM   #5
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There is a slight delay in the update of gph when you shift into neutral even on the scan gauge, sometimes several seconds before the idle gph starts to register. Yeah if you leave it in gear you save fuel but if you slow down too much its best to go as fast as possible if you are coasting, since the further you go while burning fuel at idle, the higher your instant mpg will be. Now if you have to stop then it's best to engine brake for as long as possible since all the time you are slowing down in gear you are not burning any fuel. So the trick is to prolong your deceleration to the red light so that you are not burning fuel at all as you are waiting for the red light so that you reduce your waiting time idling burning gas until it turns green.
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Old 01-22-2013, 07:10 AM   #6
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Quote:
Originally Posted by funkeywoookey View Post
Fuel cutoff is occurring when in gear and decelerating. However, with the increased engine breaking, I've found that there is more fuel economy gained when I let the engine idle down a hill in neutral.
I don't understand how/why but the Torque app says that there's also a small period of fuel cutoff directly after shifting into neutral. Is this actually happening, or a malfunction of the software?
You're on the right track. Learning the behavior and what techniques work with your car.

DFCO is different between make and model. You noted the engine braking leads to more fuel burned if you don't want to slow down. Cars with advanced valve control, like hybrids, don't have that slow down. Some don't engage DFCO right away. I have to downshift to get it to happen at speeds below 60mph. The wife's Sable delays it at cruising speeds so it can coast as well as in neutral.

As JanGeo said, make use of DFCO for when you want to slow down.

Other thing to figure is which gears have gates on the shifter. The button or pulling on a column shifter opens the gates. It isn't needed for all gear changes. The HHR can shift between D and N without it. So no worry about going to far and hitting R. The Sable has a gate between D and N, so I have to push the button. That, and its coasting in D behavior, keep me from N coasting often with it.

Also find out if your car can be flat towed behind a vehicle. The transmission gets lubrication when the engine isn't running. I wouldn't consider EOC at first either, but it can net some big gains when done right.

Quote:
I've not heard of these additives being in oil. Are they something you buy separately, or are they something that I should be looking for when buying the oil itself?

I've used fuel treatments before on other vehicles, but after calculation, I found that the financial gain was quite minimal (<$1). I will try it on this new vehicle for a few tanks to make an honest comparison.
Btw, isn't GP-7 for two strokes?

As for tire pressures, I monitor them closely on a weekly basis. I don't, however, over-inflate them (I assume this is your suggestion). Mfr suggests 32/35 (F/R). What would be a relatively safe compromise for over-inflation?
Acetone most likely improves mileage by removing water and cleaning out the system. If there was more to it, it is counteracted by the ethanol in most gasoline now.

There is an additive(PIB, IRRC) in the GP-7 that may improve fuel economy. However, I've read it is actually a higher molecular weight version of the chemical is what is the real economy booster. That compound is butyl rubber. If you have a hunk of it, throw it in a gallon of gas. Wait a couple days, and enough should have dissolved to have an effect on a tank.

There is a small benefit from the 2-cycle oil as an upper cylinder lube. You want an ashless formula like for boats. Even then the oil might contain additives harmful to the cat. convertor. The amounts most people use might not have effect for quite some time. Maybe even harmless at those concentrations. Just full disclosure.
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