Getting better mileage

Steamguy · 05-12-2006, 02:18 PM

Hello fellow TitanTalkers...

I've been doing a series of tests over the last ten tanks of gas in an effort to find out where the mileage peak is on my particular Titan.

Test conditons: Mixed city/highway driving during the same commute to work, same errands every week, same meetings at church; all drives by the same driver. No racing. No 'FY-Buddy' roar-aways. Fuel is the same brand, from the same station, all the same octane - 87. The weather has been very regular lately, with no great variations so that factor is fortunately fairly level. Highway tests were conducted over a series of long drives to family events, fuel still bought at the same place.

Truck is a very early '04, non-tow with standard paper air filter but custom exhaust (FM50, dual in-single out with 3" pipe). Tires are Continental 10 ply, at 5 PSI above door sticker recommendation. Oils are synthetic engine, standard Nissan J-Matic trans and transfer, synthetic diffys; all at recommended weights and levels.

Tester's notes: Many engines have a 'sweet spot' where everything all comes together. This particular engine's good spot was at about 2350. Yours of course will be different, depending upon mods, etc.

I found that I could signficantly increase the fuel mileage by just getting COMPLETELY off the gas about a block or so before a full stop. Experimentation has revealed that the optimum distance is about a block and a half on my truck. Also, I used the technique I learned a long time ago with a VW beetle I owned: Get to speed quickly, then get off the gas just enough to maintain speed.

One thing also helped, and that was to keep the pedal depressed at a constant level. Small accelerations cost in fuel. Collorary for the Titan: Make cool exhaust sound, pay at pump.

Gathering the 3000 RPM data was difficult, as many idiots thought I was racing them. Wait until next time, you guys...

Anyway, I hope this helps. I'll check back a few times and answer any questions.

Wiscdave · 05-12-2006, 02:36 PM

Nice write-up. The coast to a stop is huge.

I find that 2350 a suprise, I was thinking below 2k but it takes forever to get up to speed.

kman · 05-12-2006, 03:13 PM

interesting read. clarification, when you say 2350rpm, do you mean that is the optimal shift point when accelerating?

Steamguy · 05-12-2006, 08:58 PM

Quote:

Originally Posted by kman

interesting read. clarification, when you say 2350rpm, do you mean that is the optimal shift point when accelerating?

No, by this I mean "point the tach at that number and hold it there". This is only possible because we're working with an automatic transmission. Otherwise I would agree with you if we were using that as a shiftpoint for a manual.

And about holding it at 2000 or below, I was really surprised at that, too. I even ran an extra tank of gas to check that one out. And it stayed consistent. My thinking is that you're holding the throttle open longer to hit speed, so you end up dumping more fuel through the engine system in the end. Plus it feels like it takes so much longer... it actually takes approximately five seconds longer to hit speed, let's say 60 MPH, when doing it like this.

Oh yeah, I forgot to mention: I was going to do a 3500 RPM test, but this was getting a lot of instant attention from the local constabulary, so I was not able to consistently accelerate in this manner. Sorry about the lack of data there, but I value my insurance rates more.

Thanks for the kind consideration...

FuzzyLogic · 05-12-2006, 10:13 PM

Quote:

Originally Posted by Steamguy

No, by this I mean "point the tach at that number and hold it there". This is only possible because we're working with an automatic transmission. Otherwise I would agree with you if we were using that as a shiftpoint for a manual.

And about holding it at 2000 or below, I was really surprised at that, too. I even ran an extra tank of gas to check that one out. And it stayed consistent. My thinking is that you're holding the throttle open longer to hit speed, so you end up dumping more fuel through the engine system in the end. Plus it feels like it takes so much longer... it actually takes approximately five seconds longer to hit speed, let's say 60 MPH, when doing it like this.

Oh yeah, I forgot to mention: I was going to do a 3500 RPM test, but this was getting a lot of instant attention from the local constabulary, so I was not able to consistently accelerate in this manner. Sorry about the lack of data there, but I value my insurance rates more.

Thanks for the kind consideration...

At 2,350 rpm, I believe I'd be going well over 70mph. I have the 3:36 Big Tow gears...

Steamguy · 05-13-2006, 10:22 AM

Quote:

Originally Posted by FuzzyLogic

At 2,350 rpm, I believe I'd be going well over 70mph. I have the 3:36 Big Tow gears...

You missed the point. I mean put the tach to that number and hold it there while you're accelerating...

Or are you just yanking my chain...