Running out of ideas
 

I drive a '97 Sentra with an automatic. I now have it up to 40 mpg. I still have a couple of body things to do, but mechanically, I am running out of ideas. I can't justify the cost of electric power steering and an electric water pump, as they are on the same belt. How much of a saving is there, and what else mechanically is a good investment for the Sentra's?

My 08 Altima peaked at 33-34 MPG using mild techniques (2.5 engine CVT 3100 pounds). Do not coast with the engine off, you will damage the CVT. Coasting with engine running is one of your best weapons.
I think you have reached a plateau and from here on the benefits will be fairly small.

I would not worry about modifications to steering and the water pump, costly and with a small benefit.

Fayette ville is hill country I believe. Hills can be an advantage if you use them properly.
With a 33 MPG highway rating you are at about 33% over Epa highway and that's pretty darn good. Lowering your average speed and anticipating any forced stops and coasting are probably already in your technique. Route strategy where you avoid heavy traffic and stay at 35-45 MPH speeds might get you a little higher, but as I said earlier I think you have reached close to your maximum potential.

The Nissan CVT seems to handle coasting and reengaging the gears well at almost any speed.

Regards
Mech

I have been debating larger skinny tires with a lowering kit for some time. This would drop the rpm's as about 80% of my drive is highway at 55 mph. It is hill country and I can actually hit 45 mpg around town. My daily drive is from Fayetteville to Goldsboro and back. 63 miles one way. Would a manual swap give a big enough payoff to justify? I am thinking about starting to look for parts for the project car :thumbup:

97 isn't CVT, but since it is a torque-converter automatic, coasting engine off is still pretty damaging.

[QUOTE=Sentraguy;291154 It is hill country and I can actually hit 45 mpg around town. [/QUOTE]

Wait just a gul dern minute. Hill country? I used to live in Wilson and drove through Goldsboro and Fayetteville regularly. I'm 6' tall and swear I could see right over the top of the biggest hill in that area when standing in the "valley" to the west and looking out onto the water inside the Outer Banks. Ya want hills, drive to Ashville. :)

It is a little hard to find taller and narrower low rr tires, but the difference in rolling resistance can be pretty large from lowest rr to highest rr: it's a roughly 1:2 ratio. The current Prius tires are fairly wide. The aero vs rr tradeoffs can be complicated.

If you look at a bsfc map for your engine, you could find that you don't gain a lot from longer effective gearing (whether from gear ratio, taller tires, or a combination.) You probably will, (in fact the probablility is high) but before doing a lot of work, it would be nice to know that you are getting closer to the engine's sweet spot.

It sounds like you are doing really well if you can get 45 mpg around town.

You'd have to check the final drive ratio of the manual (and the top gear ratio). They can go either way from the auto. The trans swap would be fun to try. I presume you are not doing engine-off p and g now, and the manual would permit you to do so.

Given your long time spent at 55, any additional aero mods would pay relatively big dividends. I'm impressed with how well you are doing already.

I don't do anything engine off as I personally feel that is kinda cheating the system. I mean no offense to anyone who does, I simply don't do it. I am working on a kammback right now, and waiting for time off work to do the rear wheel skirts, front tire skirts and side skirts (feel like a chick with all this talk of skirts :D ). I can get the manual for cheap, and the conversion is not hard at all. I just can't decide if it is worth the work it would entail. I was thinking of upsizing to a 175/70r14 to stay the same width I am now, at biggest a 195/75r14. Oh and we don't have hills down here, just hollers. Oh well, time to start working on a 3 wheeled design.

try a front air dam on the chin. petty easy to do.

I've already done the front air dam and spoiler on the front bumper.

Yeah, I'd recommend more aeromods. Smooth wheel covers, rear fender skirts, the kamm back is a great idea too. An alternator delete is a good mod, especially if you need a new battery and can nab a deep cycle instead of a starting battery.

Weight reduction would always out switching from your factory seats to racing seats would reduce weight