I was wondering if anyone out there has made any attempts to modify their Xterra to simply improve their mileage. I love everything about mine, but am sick of stopping at the gas station. I want to make some mods, and wonder if anyone has any experience with this, and can make recommendations. Specifically, I am considering:
Under drive pulleys High flow exhaust Mod chip for computer Performance spark plugs New gears
I have heard that you can gain some improvement by shifting the manual trans once you hit 2300 rpm, and staying in high a gear as possible. I'm trying that out now, and it looks like you can gain 1-2 mpg, which is pretty good for something which is free.
Are you in the habit of blipping throttle on upshifts? I have a pet theory going that rapid changes of engine RPM uses a lot of gas. So even tho I still blip to practice my heel-toe skills, I think it's costing my 2 mpg on my Maxima. Also, of course, don't use the engine for braking, and don't accelerate any faster than you need to.
What's blipping the throttle? Have not heard that term before.
I never use the clutch for braking, and in fact, coast as often as possible. I am doing all the basics to improve mpg, watching tie pressure, following speed limits (that's a tough one), etc.
Entering a typical corner at an intersection, you will decelerate and downshift before reapplying throttle. Race drivers prefer to execute the shift during the braking phase of the corner, so they are ready to blast at the earliest possible exit point of the corner. During the braking approach to the corner, they use a technique called heel-toe shifting which tilts the braking foot partly off the brake to touch the gas during the shift and putting the car into the lower gear. The 'blip' of the gas is to rev-match to the lower gear, not necessary but a good idea on standard synchromeshed transmissions. Since you're using 2 feet to control 3 pedals, it takes practice. I learned to do it for my own amusement, and also because I intend to do some driving school and/or autocross in the future. I do it on the street sometimes now, and usually into the lowest possible gear. This wastes a bunch of fuel. Normal driving looks more like this: begin braking, drop car out of gear (either clutch in, or in neutral), coast around turn, engage in appropriate gear. To conserve fuel further with this approach, bring up the engine RPM smoothly and don't accelerate until the clutch is fully engaged (also saves wear on the clutch).
?? The plugs it came with are "performance" plugs, splitfires/ pltinum +4's etc are junk.
How about a smaller vehicle with a smaller lower HP engine? :-) Basically the problem is the aerodynamics of SUV's suck and they are going to eat gasoline because of it. What might do something would be to drastically lower it and do some aero mods?
I have never blipped on an upshift only on my heel-toe downshifts. What is the benefit? My 2004 Frontier averages 19-21 mpg (V6, Crew Cab, 4x4) in urban, suburban type driving. I rarely take it over 2500 when I shift and I do leave it in high gear pretty often. I doubt a chip or gears or plugs are gonna help. Try using 0W-30 Amsoil Synthetic, an Amsoil Air Filter, Redline MTL in the transmission and any synthetic in the transfer case (if yours is 4x4 ) and the rear end. You should gain at least 1 mpg from these changes.
What you, everyone else has said. New gears? as in higher gear ratio? Good for highway, may hurt in city. Chip mods are proly better for raw hp,but might help mpg's.
I try to keep my tires at 40 psi. 35 at least. And, some tires are much harder than others. Also style of tread. I got 95,000 miles on a set of Michelins that came w/ my Sub. Outback! But then, safety is an issue also. Lighter rims? Drive w/ windows closed.
Use the lowest octane you can, w/o knocking. Lower octane has more BTU/gallon, ergo more mpg. Texaco was sued by the gummint for implying otherwise. If knocking is a problem, get lower temp 'stats until the knocking disappears. Would be nice if variable temp stats were available. Then you could "tune" each batch of gas.
Diesel is close to kerosene. Kerosene is used to clean gas engine fuel injectors, and diesel supposedly lowers octane. So perhaps.... perhaps..... there is some optimal mixture of diesel/gasoline that would help mileage. Maybe somewhere between 6 oz (about the size of an injector-cleaner bottle), and a quart, per gas tank. I have not tried this, but I will (sooner or later), and will report back.
Bigger diam tires would help on highway, but might hurt in city.
A motorcycle friend of mine said that this Vortex gizmo you see on infomercials really works--even on fuel injected engines! I can't see how this could be true, but this guy is no hayseed. Supposedly a magazine or two verified this thing.
Funny thing: when my alternator went on my 1990 Mazda 929, I would charge my battery at home, and then at my machine shop, 25 mi away. Was a cupla wks until I was able to find a j'yard alt (damn, Mazda parts are expensive!!), and noticed my mpgs were WAY UP!!!! 3-5 mpgs!!?? Was thinkin about not fixing the alt at all, and just keeping two batts in the car!! Now that ahm gettin a PU truck, I might actually do this! Just put a switch/relay on the alt. output, for when I need it. They make a new kind of battery, MUCH thinner, but same amps (I think) as a reg. car battery. About 1/4 to 1/5 the weight. Maybe good for
0.05 mpg's, due to weight!
High gear is indeed very important. The lower the rpm, the more complete is the combustion. Probably don't want to "lug" the engine, either, so you have to develop a feel for what's "right".
If you have crankshaft-driven fan, remove the blades, change to electric fans. Also quieter. Crankshaft fan is good for a cupla horsepower.
Also, you have to be aware of how to accurately calc mpgs. Always fill your tank up, to the *same* level, which may seem obvious--but the only accurate way to do this is to actually be able to *see* the gas somewhere at the nozzle-level, which they say you are not supposed to do, for a variety of reasons. But which I do anyway. This way, you can *very* accurately determine mpg's (but not until the *next* fillup) to within a *fraction of a percent (!)*, AND determine who's selling shitty gas. With pretty constant driving conditions, I've noticed 5 mpg diff's in gas!!! This way, you can also "measure" the diff between high-priced high octane, and low octane. Also have to factor in the cost. You are not so much interested in high mpg's as you are LOW $/mile.
Lowering the car more to the ground supposedly helps. If not, perhaps a shroud, like racing cars. Would look sharp. Perhaps mud flaps before and after each tire.
Could also remove your cat. converter... :) :(
Also have to keep in mind that the ROI for increased mpg's is pretty long, depending on the cash outlay and the increased mpg's. As you say, increased mpg's "for free" is great, but too much cash outlay may never be recouped. For example, a Prius is about $10K more than an Echo, w/ about 6 more mpg's, according to Consumer Reports. Depending depending depending, it will take between 10 and 30 years to recoup that initial additional $10K outlay for the prius!! So, for example, new lightweight aerodynamic alloy rims, while in principle gas-saving, will likely never pay for themselves, gas-wise. But a new thermostat so you can burn regular gas definitely would--in short order.
Mark, I just bought an Xterra (2004 model). I'm researching better mileage too, because I love the truck other than the mileage. It appears that a 'Cool air intake' and high flow exhaust gives the most bang for the buck, along with keeping your foot out of it. I have a Volant cool air intake on order and am looking into maybe a Flowmaster exhaust (muffler only maybe). I will try to remember to let you know what kind of results I get. You can go to xterraparts.com and see some high flow exhaust systems. Both changes cost some bucks. If gas prices keep rising then the payback may be quicker. Good luck.
Mark, I just bought an Xterra (2004 model). I'm researching better mileage too, because I love the truck other than the mileage. It appears that a 'Cool air intake' and high flow exhaust gives the most bang for the buck, along with keeping your foot out of it. I have a Volant cool air intake on order and am looking into maybe a Flowmaster exhaust (muffler only maybe). I will try to remember to let you know what kind of results I get. You can go to xterraparts.com and see some high flow exhaust systems. Both changes cost some bucks. If gas prices keep rising then the payback may be quicker. Good luck.
I may be double posting here. My first time on this site. I just bought a 2004 Xterra and am researching better mileage. I love the truck. So far it looks like adding a cool air intake and free flow exhaust has the most dramatic effect. I have a Volant cool air intake on order. Am researching some free flow exhaust options. So far I have read about the Flowmaster 40. There is a performance exhaust system at xterraparts.com. Will try to post my results after I add my mods. Good luck.
Changing muffler and/or intake will not improve fuel economy. They will only reduce restriction in the engine intake and exhaust, increasing air flow. The peak engine output will improve some, but the fuel injection system will always increase fuel flow to match the air flow. In other words, it doesn't improve fuel economy - if anything, having a more powerful engine will give you the ability to burn more gas.
You assume these actually do anything for MPG... Do you really think they are NOT using a "cold air" source already? Any exhaust restriction if there is any is going to be BEFORE the converter not "cat back", the air has already cooled down enough back there where it's not as dense.
Adding a high-flow performance exhaust system (usually a cat-back system) WILL improve your mileage; I speak from experience. The first major mod I made on my '03 Frontier was a Gibson cat-back exhaust system. Sure, there are still some catalytic converters on the system, and I can't change the headers yet, but YES, adding an exhaust system does improve mileage. The reason why a lot of owners never realize the gas savings is b/c their foot is on the gas so much more b/c of the sound of the exhaust!
Putting on a CAI (cold-air induction) system will also improve your mileage. Again, however, these savings may not be realized since the owner will be putting their foot on the gas even more. I put a K&N filter on my truck too (no real CAI's for my pokey 4-cyl), and realized more savings.
Want results? For one week, I babied the truck, mostly driving highway to work (1 hour each way), coasting up to stop lights, etc, WITH the K&N and Gibson exhaust. Mileage??? 32.5 mpg. Now, granted, I have a 4-cyl,
5-spd 4x2, but still, EPA estimate is 23 mpg highway, 21 city.
The manufacturers look at bottom line. If my exhaust system was a stocker, high-flow design, it would have cost more to manufacture, so why add the cost??
Think about it, why would a high flow exhaust help at low RPM's where there is not enough flow to even start to stress the stock system?
Yea they put restrictive exhausts so they can then have to design dual cam 4 valve heads to make up for the lost power. Sure, a muffler is a LOT more money than a 4 valve, dual cam head costs...
Changing equipment and driving style, and getting a huge (almost unbelieveable) difference in mileage, I suspect three things: - your car was capable of this all along - your change in driving style is responsible for any real change in average mileage - your single data point of 32.5mpg needs to be repeated several times to believe it. 10mpg is gigantic - if I measured that I would continue for a couple of gas tanks, filling at the same exact pump with the same fuel. The average is the value that will be useful.
Honestly, it'd be difficult do duplicate now b/c I have racks on the back of it, which I put on in August.
Yes, I had driven like this before the other mods, and only got about 30 mpg.
The exhaust system was designed to provide max benefits from 2-4k, which is right at highway mileage. I notice more pick-up at highway speeds with the Gibson than the stock system.
Yes, as a scientist, I know that the results should be duplicable if the variables are the same for the second try. Realize, also, that this truck was getting about 25mpg in mixed driving *before* I put the exhaust on it.
Well, whatever. In another post you just said it was getting 30mpg, and after the upgrades you have a single data point of 32.5mpg. How that is so drastically different from EPA ratings, I'm not sure, considering that EPA estimates involve serious granny driving.
As far as repeatability, each gas pump fills 'up' to a different level. So to measure more accurately than ±1-2mpg, you either need to use the exact same gas pump, manually top off each time, or take several consecutive tanks to average out the effects. To put that .5 on is exaggerating the accuracy.
My point is I still don't buy it - aftermarket filters/exhausts haven't proven to save any gas.
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