I'm curious does anyone have a ball park figure or guess on fuel consumption in closed loop vs open loop operation or a link? This would be a 93 V6 auto operating in warm weather.

I do not see a clear answer on the net.

 

An Auto in Closed loop ought to give better than 17MPG highway in ordinary conditions.

My manual tranny '95 Runner with 4.56 gears and 32 inch tires gives about 19.5 MPG at 60mph and it drops to near 18MPG @ 70 to 75mph.

What are your issues?? A professional scanner with period software can tell whether you're in closed loop, or not.

 

Some of us on the Toyota RV forum are having poor mpg issues. I'm reading a bit and find info on closed and open loop. But do not see any actual percentages or anything solid. I appreciate the 17 mpg but no one with a V6 auto RV are getting anywhere near that. Maybe the consumption between rich and lean is negligible and not an issue?

I have read at least 30 articles and seen only one number published claiming a 20% difference.

 

Well, ya didn't say anything about RVs. When you're dragging a giant box loaded with god knows what, all bets are off.

A pro scanner and a wide band O2 sensor can still help ya.

 

Added RV to my signature, need to look up pro scanner and wide ban sensor, all this is above my paygrade.

 

I would think that the difference between open loop and closed loop would change depending on how close the pre-programmed values and fuel "map" for open loop operation in the ECU matched to the actual operating conditions.

A closed loop system should perform better and get better mileage than open loop.

What fuel mileage numbers are you getting?

Are you thinking that the engine is not going into closed loop?

 

Long story, I do not tract my mpg but recently had a drop so significant that it was hard to miss, so checked my mpg. Only a couple tanks and varied driving so not a good mileage check but I was getting over 10 mpg. On a trip so I diagnosed as best I could and replaced the fan clutch. Again only a couple tanks and mpg seemed to be 10 to 11. But I started having issues with transmission not wanting to go into overdrive.

Took to Aamco transmission in Macon GA and they could find nothing wrong. Claimed transmission was in excellent condition, so I was not afraid to continue my trip home.

Started reading about poor mpg and learned a few things. Also figured out my motor was running around 165 degrees on a 93 degree day. Also read about this closed and open loop and wondering if this fits in someplace?

Did not like the way the aftermarket fan clutch operated so returned and replaced with an Aisin. The thermostat tested good, but I was not sure if it was OE so replaced with an OE Toyota stat. Engine is now running around 180 on a 20 mile drive and motor sounds much better. I am checking motor with a temp gun right after driving on highway. Do not drive the RV alot so will be some time before I can do a road test for mpg.

There are a few on the Toyota RV Face Book page that are experiencing poor mileage so hoping to find something that has been over looked. One owner could not get over 10 out of his V6 so got disgusted and sold it! 12 to 13 seems to be average mileage with some drivers claiming to be able to do 14. I would be happy with the 12-13.

So anyway curious about the open loop/closed loop and how much it affects mpg?

 

I would say the 20% difference is pretty a accurate bu that is merely a guess. The engine running around 165 is what was causing your transmission troubles. The ecu will not allow the transmission to go into over drive until it is up to temperature. I want to say they did this to warm the engine up faster for emissions.

 

Thanks for the response, out of curiosity I put it back together without the thermostat and it would not reach operating temperature and not even try to go into overdrive. So what ever controls that is working. I was also told by another Toy RV owner that when under load such as accelerating it requires that gas be let up on to shift into OD, but just cursing along it will automatically shift. I need to check this and mpg next time I take this out. Nothing about it in the owners manual.

Next on the mental list if I get no improvement is the O2 sensor. I believe mine is OE with 115000 on it. Many claim they should be replaced over a 100K??

 

Yes, changing the oxygen sensor would help. Its a maintenance item. The sacrifice of more $$ at the pump is a usual sign. Just over 100k is pretty good usage on them. Maybe ask those who are getting higher mpg while using their RVs if they are using wide band sensors to give you an idea of whether you should go that route.

 

I can't seem to be able to get a straight answer from the RV forum. So I would have to guess that the answer is no they do not use wide band sensors.

 

The 'wide band 'O2 sensor is not a replacement for the O2 sensor that talks to the ECU.

It is installed separately and sends a signal to a gauge that reads out a display of real time fuel/air ratio.

 

It (a wide band) can be hooked up as a replacement for the factory narrow band in many cases, I was just looking at these again the other day, some provide an output to simulate the typical narrow band signal which is intended to be hooked to the ECU..

 

Thanks for the reply's, I have been reading on the Wide band sensors, seems to be more of a enthusiast thing than I would be interested in.