105 MPG coast
 

I drove home from Wal Mart today and did a down hill coast (engine on in N) right before getting exiting on the off ramp. No big deal I've been doing this plenty of times. This time was different though. Today the SG2 reported 105MPG. It has never reported over 75. It stayed in the 80 to 90 range all the way down. Do you guys think it's because of the grill block that I added or maybe because I had the 19.4% correction on the SG2 last time I filled up?

I don't think it would be the grill block when you're in neutral. It's just your idle gallons/hour times you're speed. (unless you got coasting faster than usual.) Was it a blistering hot day? I had a great coast like this just yesterday and first saw 100+mpg. On my good coasting hill the car had already heated to where it reported 0.5gph in neutral versus 0.6gph. Bam, 20% difference right there. And who knows it might have been right on the cusp of rounding to the next tenth, so maybe it was a smaller difference than it appears. But 112mpg sure looks nice.

I started coasting at 40mph, which is normally what I coast on this hill. It was pretty hot but not unusual for where I live.

nice #s just keep working on it! you have improved really quickly and its sweet to see

I'm trying. We're probably going to New Orleans this weekend. About 70 miles from Biloxi. What would be the most effecient speed on a 70 mph I-10?

It seems somewhere between 40 mph and 50 mph.

So an off the wall and possibly bad idea I thought about was, your car is an auto and you don't really want to turn off the engine while rolling. How about hook a button up to the injectors so that you can stop them from firing and sit there and tap on the button so it is only getting gas half the time. That would double how much mileage you are getting while coasting in N. The car would idle badly like that but as long as you let it get enough gas not to die it should be ok.

Of course since it is probably an OBD2 car, the computer will probably hate you if you try it.

I wonder if there is some kind of electric booster pump that could be added to the trans so the fluid could be circulated while the engine is off. That would be a great way to let an auto trans do engine off coasting.

Coyote X I had the engine on in N. Please re read first post.

Coyote X: The idea you had doesn't work. The car uses the oxygen sensor to try to maintain a optimum air/fuel ratio. When you just shut an injector off, all it does is to add more air, but without fuel, so the computer tries to compensate and, well it doesn't work well.

popimp: From the scangauge data you got and some testing, I found that I have to hit about 43mph for the transmission to go into 4th and to lockup. Anything lower than that, in speed and either the lockup is not engaged, or the transmission is in 3rd gear, either of which equate to lower mileage.

If your on the interstate, I don't think you can legally go less than 45mph, but I would drive fast enough to stay out of the way of the Semi's. I think you'll still be surprised by how much of a help the grill block will make.

popimp,

Firstly, I've been following your struggles to improve your mpg since we've both got similar cars. Based on my recent experience, "getting out more" seems to help raise your mpg because you're travelling closer to highway speeds than city speeds therefore should raise your mpg closer towards the highway mpg and away from city mpg. Your mileage may vary but on my relatively long distance drive, I was puttering along at 55 mph or less due to at least three traffic jam pockets and got bored on the way home so was practicing pulse & gliding up to 60 mph then back down to 55 mph. That resulted in a relatively astronomical mpg boost to 28.32 mpg. For a frame of reference, the posted speed limit on the highways for my trip was 65 mph.

Godslow popimp. :)