Hi All

I posted this in the general forum but was told to repost here.

We own one of the first 400h's in the states, 23rd i believe. We are very disappointed fuel econmy. 23mpg average. Living in Washington DC we drive mostly in the city. What are the chances for getting a softwear modification from toyota to get the gas engine to turn on later, thus improving FE. I am also wondering about the number of 400h and HH owners willing to sign a petition to get toyota to do this if indeed it would be wanted.

On another slightly related note, is there an electric only mode modification for the 400h. I know there is one for the new prius.

thx
-Alex

 

Alex,

I share somewhat in your feelings of disappointment. However, some of that can be alleviated by practicing some of the various fuel economy techniques and tricks posted on this site. You should be able to get 25 mpg without much modification of your current driving style and still preserve the levels of power/acceleration that you would expect from your Lx400h.

I believe the basic problem is that the Lx400h and the HiHy both have V6 engines which is inherently more gas guzzling than some of the other V4 engine hybrids, like the Ford Escape. However, comparing the Lx400h/HiHy hybrids against the FEH is a little bit like comparing apples and oranges. If you did have a regular non-hybrid SUV, a V6 engine would have a real-world FE of probably 18-19 mpg. So 25 mpg relative to that (35% higher) is pretty good.

We tradeoff poorer fuel economy for more horsepower. The Lx400h/HiHy get 268 hp which kicks butt over all V4 SUVs. Sometimes I forget about this until I drive another SUV or mini-van and cringe at their lack of power.

I think Toyota could tweak some of their logic to further improve the FE, but given the V6 engine, I would expect those improvements to be modest (maybe another 10-20%). I think if they really want major increases (e.g. FE~30 mpg) they will have to somehow provide a method to dynamically shut off some of the cylinders so that the engine behaves like a V4. The Honda Odyssey currently does this trick, but it comes at a price. There's a dip in power when you try to accelerate the Odyssey as it transitions from a V4 to a V6. Perhaps with an electric motor assist, Toyota could avoid this dip in power... Random speculation of course...

 

I'm sure if you contacted the company that did the Prius mod they may have a mod in the works. After all, it's the same HSD.

I drive the HH in LA traffic every day and I manage about 29mpg over 4 tanks since I've had it. I have modified my driving style somewhat though. I start slow and get up to 20 or 25 then drive normally. I also brake much earlier and take my foot off the gas a lot more.
Just ideas. If you find info on the HSD for the 400 or HH please post it.

good luck

 

Since you have one of the earliest 400h's, have you checked to see if the ISC Learning procedure has been done? This is a TSB that I saw mentioned in another HH forum. It apparently can make a measureable difference in gas mileage.

Here's a link to the Lexus TSB:


http://www.alldata.com/tsb/Lexus/114...-05/index.html

 

This isn't a software issue. Turning on the ICE later (ie. using the battery for acceleration more if I interpret your post correctly) would lead to LOWER FE numbers.

I'm afraid this basic misunderstanding of how the HSD works is indicative of the fact that your FE issues are more than likely related more to your driving environment (stop/go traffic/city, etc.) and your driving technique.

I wrote an article about improving your FE that's posted somewhere on this site that I strongly encourage you to read. Some things you won't be able to change, but some basic driving technique changes can lead to some significant improvements in MPG without making you drive like a granny.

 

HOLY CR@P! Every time the battery is disconnected, you need to run to the dealer for a service call like this?! GEEZ!

 

Does this apply to the Highlander as well, or just Lexus?

 

This applies to the 2006 Highlander Hybrid also.

Note that you can probably perform the procedure yourself.

The scan tool mentioned in the procedure checks the coolant temperature to make sure it is at full operating temperature and checks the engine loading to make sure the load is sufficient to charge the battery and finally checks the status of the ISC learning parameter. It is not necessary to monitor these parameters if you do the procedure carefully.

1) Make sure the vehicle is fully warmed up. Do the procedure immediately following a long drive that runs the engine (highway speeds are best - not long gliding stealth runs at low speeds with the engine off). This will insure the coolant temp is at FULL operating temperature - it is not necessary to actually measure the coolant temperature if you warm up the engine sufficiently and don't let the engine shut down too long and cool off before doing the procedure.

2) With the vehicle stopped and in drive, press firmly on the brake to keep the vehicle from moving and then step on the accelerator while watching the power meter (to the left of the speedometer). Press down on the accelerator to keep the needle between 1/2 and 3/4 up the scale. You will find that the engine management system will automatically limit the engine load no matter how far you press down on the pedal so the amount you press is not critical as long as it is either 1/2 scale or to the engine's self-limiting load value. Keep the engine loaded for a full 30 seconds but not longer than 40 seconds (this procedure brings the hybrid battery up to a maximum state of charge - if you watch the battery symbol, you willl see it tick up to a "full" display).

3) Shut off the engine and place it in park
4) Wait 5 seconds.
5) Turn the ignition key back on to display "ready"
6) make sure the A/C and heater system controls are set to off
6) Lightly step on the accelerator pedal until the engine starts -then immediately take your foot off the accelerator and let the engine run until it stops by itself.

This completes the procedure.

 

I had this procedure performed at the Toyota dealership shortly after my intial 5K service. It improved my fuel economy by approximately 10%. Don't let the ney-sayers BS you. Just because theirs were programmed properly doesn't mean that someone didn't disconnect YOUR battery and neglect the programming sequence sometime in it's lifespan between when it was built and when you got it. Mine is a Highlander Hybrid and no driving technique were changed. Only the ISC learning procrdure was done. They did change oil (over filled it of course) during the 5K service but they didn't actually perform the ISC until I "insisted" a couple of days later. I checked fuel economies after the 5K service and before the ISC and then again right recently. Went from and average of around 25MPG to around 27.2MPG currently. Not a hige difference but probably enough to make me feel better about the truck's capabilities itself.

PS - Oil level is still "overfilled" (from the 5K service) but I figure I'll wait a another tankfull before I reduce it to the proper level just to remove that variable from the current findings.