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Hello All - I'm new on the forum, and have done several searches for revelant info to no avail. I have a 2007 Toyota Highlander Hybrid (HiHy) and am trying to find out it's potential for maximum Fuel Economy (FE) and the effects of tire pressure and road speed on FE.
Some years back I had a motorhome with a car in tow that I had rigged with a mpg computer. It had a real fuel flowmeter and a speed pickup from magnets on the driveshaft inducing a voltage pulse in a fix mounted coil. I noted that from a standstill with 0 mpg, it rose to a max. of 14 at 47 mph, and then dropped back to 9 at 60 mph.
This FE sweet spot at 47 mph then became my cruising speed when traffic allowed.
I would like to know if anyone has determined the FE sweet spot for the HiHy or any of the other hybrids currently on the market. I would also like to know what the useable tire pressure window (normal to max) is for the HiHy, and it's effect on mpg. Again I suspect a FE vs TP sweet spot for the tire pressure, unique to each model vehicle.
Also, I read with interest the article on Warp Stealth mode for the Prius II, and am wondering if such a mode exists for the HiHy.

Most people use max sidewall pressure as a rule of thumb. Basicly add a few lbs at a time until you get used to it. Jumping to max sidewall is some times too big of a jump for most people because you feel every bump. A gradual increase helps take the edge off.

Some of us go past max sidewall, but the higher you go the less of an effect it has.

Hi Tom and welcome to CMPG

Many of us here have a Scangauge that will show you where the sweet spots are on your THH. There are so many techniques to improve FE discussed here but I recommend you first read the Hypermiler articles on the home page if you haven't already.

The max sidewall pressure is the minimun I recommend. My FEH is 44psi and I now run 50psi with no problems. The other day I was drafting a dump truck untill he climb to 80mph. Then I gave up and went into a neutral for a glide. I went into a 35mph speed limit turn between 70-75mph and the tires started to slide well into the turn and it was to late to hit the brakes. It was a very controlled slide sideways and I managed to keep the FEH on the pavement. After my heart quit racing, I realized having the tires that high keep me from digging in and rolling.

Anyway, it sounds like your serious about FE and I would love to hear if the THH has the ability to push into the 40mpg range.

Good luck with it!

GaryG

Hi Tom:

___The following pic was taken by Eric Powers in a bone stock 4WD HiHy in July of 2005 while simply playing w/ P&G on some country roads local to him. I would not bet against the 2WD HiHy achieving a 60 mpg segment with the proper setup, right stretch of road, perfect temps, great traffic conditions and most importantly, a driver with the experience and a desire to really push for it.

http://www.cleanmpg.com/photos/data/504/HiHy_-_4WD_-_41_1_mpg_-_21_miles.jpg

___This is not the type of result you could expect day in and day out but I believe the HiHy is a 40 lmpg vehicle with most of the above given its hybrid qualities and a healthy 30.5 EPA combined.

___Good Luck

___Wayne

"Also, I read with interest the article on Warp Stealth mode for the Prius II, and am wondering if such a mode exists for the HiHy."
I'll partially answer my own question - YES a "Warp Stealth " mode does seem to exist with the HiHy. I was observing the dash gauge display (I don't have the scanguage) and observed periods of operation when the gauge indicated pure coast, and other periods where it was running in EV mode. The instantaneous MPG was indicating 99 during these periods. Essentially zero fuel consumption. :woot:

"Also, I read with interest the article on Warp Stealth mode for the Prius II, and am wondering if such a mode exists for the HiHy."
I'll partially answer my own question - YES a "Warp Stealth " mode does seem to exist with the HiHy. I was observing the dash gauge display (I don't have the scanguage) and observed periods of operation when the gauge indicated pure coast, and other periods where it was running in EV mode. The instantaneous MPG was indicating 99 during these periods. Essentially zero fuel consumption. :woot:

Hybrid operation for the HiHy is essentially identical to that of the Prius...total amperage i/o due to the larger battery and dual MGs (MG2 and MGR) mean the threasholds are slightly different, but all other basic parameters are the same. For instance...stealth is possible up to 41mph, hyperstealth is possible above that, gliding is possible, but takes significantly higher accelerator pressure to achieve than is necessary in the Prius. OTOH, electric only/stealth is easier to stay in w/ the HiHy than it is in the Prius.

I think 35mpg in warm weather w/ the HiHy 4wd is quite achievable with my usual route, and 40 is likely possible for those with ideal commutes who are dedicated to hypermiling. My wife is the primary driver of our HiHy and she's NOT at all a hypermiler though she's fairly aware of the basics of achieving good efficiency w/ a HSD system. Her LMPG is ~28mpg. I routinely average b/w 30-35mpg when I drive it using much stricter technique than she does.