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Old 10-19-2008, 05:48 AM   #1
BailOut
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Hang Time: Exploiting ECU Fuel Maps for Fuel Efficiency

I call this technique "Hang Time". I discovered it while driving cross country with a group of other hypermilers earlier this year. I first noticed it on the 1st generation Honda Civic Hybrid we were driving and then confirmed it on the 2nd generation Honda Civic Hybrid that we also had. Any engine that employs VVT/VVT-i or VTEC/VTEC-E definitely has this feature but so do many other vehicles, including the Ford Ranger. The only way to know for sure on a non-VVT/VTEC engine is to use a ScanGauge II to verify.

It's a fairly simple technique. Here's how it works:

While driving at a constant speed and in the highest gear possible for that speed simply back off the accelerator a "notch". You will notice that your RPM and speed remain the same but you have, in fact, invoked a fuel flow rate that is roughly 10% lower than it was. You can hold this throttle position for a long time, usually until you have to adjust for the terrain. This is why I call it Hang Time.

If you have a ScanGaugeII you can see this effect (and dial it in much better) by monitoring TPS, RPM and iMPG. When the technique is properly invoked you will see your TPS drop by a few points while your RPM and speed stay the same but your iMPG goes up by around 10%. For example, while driving on relatively flat ground at 55 MPH in 5th gear my TPS is at 26, my iMPG is around 50 and my RPM is around 2540. When I invoke Hang Time my RPM and speed remain steady but the TPS now reads around 24 and my iMPG reads around 55.

----------

From an advanced perspective this technique can be combined with a form of Pulse & Glide (P&G) to really crank out some great numbers. A ScanGauge II is required for a "Hang Time P&G" as the movements are too sensitive to guess at.

Once you reach a speed slightly higher than your target speed invoke Hang Time but instead of just backing off one notch go for two. Using my 55 MPH example above the TPS will read about 22 in the second notch. You will start to bleed off speed but just slightly so (maybe 2 MPH per mile), and your iMPG will read 30% higher than usual at this speed. Hold this position until you bleed off to 5MPH below your target speed and then push the throttle in just one notch. You will see a TPS reading of just 24 or 25 but you will begin to accelerate while still maintaining better than 45 MPG! Once you are above your target speed again back off to the second notch and settle back in while you glide again.

You will see different TPS readings at different target speeds but the formula will remain the same.
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Old 10-19-2008, 09:41 AM   #2
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Good thread,Ive known this for awhile,you can also do this with your exhaust note,but since Ive got the new Magnaflow,its harder.
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Old 10-19-2008, 11:13 PM   #3
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Is this works to both A/T and M/T?
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Old 10-19-2008, 11:19 PM   #4
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Quote:
Originally Posted by jronald View Post
Is this works to both A/T and M/T?
Hello jronald,

It works with any form of transmission. It has been successfully tested on MT, AT and CVT transmissions.
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I often carry 2 carpool passengers and mountain bikes
or snowboards/skis over a 4,500 foot elevation difference.
Click the graphic above to see my detailed mileage logs.

Last edited by BailOut; 10-20-2008 at 02:02 AM.
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Old 10-20-2008, 01:41 AM   #5
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thanks.
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Old 12-11-2008, 02:37 AM   #6
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thanks
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Old 05-27-2009, 05:57 PM   #7
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Nice tip.
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Old 07-11-2009, 02:14 AM   #8
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Very effective tip, thanks a mucho! =)
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Old 05-15-2010, 03:39 AM   #9
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WOW great thread, im going to try this tomorrow
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Old 08-11-2010, 10:17 PM   #10
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I want to know the specs of my Yaris, since I am not sure if my engine is VVT/VVT-i or VTEC/VTEC-E .. is there anywhere I can see my car specs? I bought it new in Jan 2007 if that helps...
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Old 08-11-2010, 10:29 PM   #11
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It will work with your Yaris

http://www.google.com/search?sourcei...07+Yaris+specs
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Old 08-12-2010, 12:42 PM   #12
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Quote:
Originally Posted by imjustagirl8_05 View Post
I want to know the specs of my Yaris, since I am not sure if my engine is VVT/VVT-i or VTEC/VTEC-E .. is there anywhere I can see my car specs? I bought it new in Jan 2007 if that helps...
Your Yaris, like all U.S. Yarises, has VVT-i.
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Old 11-04-2010, 10:45 PM   #13
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have you or anyone else noted a difference in miles per tank back to back?
please repost with real world results as I believe scangauge are just real time estimates?
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Old 03-03-2011, 01:27 AM   #14
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Thanks!
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Old 04-25-2012, 03:18 AM   #15
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I've tried this but for me it wasn't worth the effort. Doing the same trip every day, I had to fuel up sooner with this technique. The problem is, I think, that in order to accelerate back to your higher speed you burn more fuel than you saved by lifting the accelerator a bit. As long as you're decelerating you burn less fuel, meaning more mpg but the time you accelerate you get only half the mpg's than before. For me driving at a constant speed has proven the best.
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Old 06-08-2012, 06:17 PM   #16
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I think its lag between the apps and throttle body.
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Old 03-12-2013, 01:33 AM   #17
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Hello Friends!
i have a problem, can you solve this?
I want to know the specs of my Yaris, since I am not sure if my engine is VVT/VVT-i or VTEC/VTEC-E .. is there anywhere I can see my car specs? I bought it new in Jan 2010 if that helps...

Last edited by libra23; 03-12-2013 at 01:34 AM. Reason: words mistake
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Old 03-15-2013, 05:42 AM   #18
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Quote:
Originally Posted by libra23 View Post
Hello Friends!
i have a problem, can you solve this?
I want to know the specs of my Yaris, since I am not sure if my engine is VVT/VVT-i or VTEC/VTEC-E .. is there anywhere I can see my car specs? I bought it new in Jan 2010 if that helps...
Toyota has VVT-i technology. Only type of Yaris not having VVT-i are the ones that can be run on leaded petrol. But I dont suppose you get leaded petrol in the US. Check the owners manual. It should be there. You also might see a sticky on the fuel tank cap reading "Unleaded fuel only". (Not sure if this is pasted in your country, but it is there in my Yaris)
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