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Discussion Starter #1
Since my tires kill my MPGs, I've decided that in the next year I'm going to put an STS Turbo on my truck.

Budget looks like this:

$2000 for STS Turbo Squires Turbo Systems - Universal
$700 for Uprev Osiris Tuner Package (I have free access to a Dyno)
$300 for anything else I might need

How many pounds of boost can I safely run on the stock internals? This mod is purely for MPGs, any performance will be secondary for a while. If I ever justify spending the money, I will upgrade all the engine internals and do head porting and all that goodness. I'm going to do the labor myself, as well as the tuning. Any input will be greatly appreciated, I will do a full write up when it's done.
 

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why doing it for MPGs your spending money and will never make your investment back
 

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Discussion Starter #3 (Edited)
Well if I double my MPGs like the vq motors do, then I would only have to burn through 50 tanks to get my money back.
 

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well i have seen some sentra turbo kits run up to 8psi (half bar) and they claim it's safe on the stock engine. however keep in mind that its the sentra fwd engine. but being that they are both qr25 engines, i would think that the blocks are atleast cast the same, with the same material and thus could handle the same pressure.

also, you may want to read on this for inspiration...
spec v turbo
 

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i ran 8psi in my z with stock internals and the vq35 runs 10.3:1, the qr25 i believe is running 9.5:1 and i think has steel connecting rods so you should be perfectly safe with 8 unless it has another weak point in it like maybe the head gasket or anything. 6psi would be very safe for sure if 8 has ya worried.
 

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Well if I double my MPGs like the vq motors do, then I would only have to burn through 50 tanks to get my money back.
i find that very hard to believe that you will double your MPGs also did you do the math on running 91+ gad because turbos need the extra octane
 

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the v6's are doubling mpg's with a turbo?!?
 

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Discussion Starter #8 (Edited)
Xterrahines gets 30 on the highway. And my parents stock xterra barely gets 16, and I'm sitting at 17.

i find that very hard to believe that you will double your MPGs also did you do the math on running 91+ gad because turbos need the extra octane
I did my math at $2.99 a gallon, which is about average where in live for 91.
 

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Xterrahines gets 30 on the highway. And my parents stock xterra barely gets 16, and I'm sitting at 17.



I did my math at $2.99 a gallon, which is about average where in live for 91.
if your parents are barely getting 16 on the highway then they must be driving with the overdrive off or something. i'm guessing you mean as their average they barely get 16 which you have to factor in alot there, like how much highway and city that is, how much weight they tend to have inside (how many people) your general weather, and driving habits. there are many many people that get over 20 on the highway in their vq40s so you really can't go so far as to say its doubled, and have you though about city driving. the fuel mileage benefits really depend on you staying out of boost. my twin turbo z could manage almost 30 on highway trips (not much over stock mpg of 26 highway) but in the city i generally got in the area of 13. i think my average with driving 50 miles a day (25 to work 25 home) being highway was still only 18
 

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Discussion Starter #10
The average is 16, with daily drives going 45-65 average speed. Very little start and stop. I live out in the hills of northern ca.
 

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The Turbo sounds nice but I wonder if you just do an m226 swap with the 4.56 gears, it may get you back to the correct ratio.

Also, can UpRev do anything for the tuning on the QR25 motor?
 

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Discussion Starter #12
the problem with miliage is not from gearing, with stock tires to do 65 in 5th the rmps sit at 3K, with the bigger tires they're at 2500, but it kills my milage in the lower gears.
 

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The average is 16, with daily drives going 45-65 average speed. Very little start and stop. I live out in the hills of northern ca.
even with little start and stop those hills aren't going to do you much good when it comes to MPGs on a turbo charged vehicle especially one with the weight of our trucks, your tires, and how little torque the motor itself produces without the assistance of boost will force you into a generous throttle pos when going up hill and you'll most likely see boost of a couple psi quite often in your drive. i really don't think your going to get the result that your wanting, it would be a very cool project none the less. gears would make it easier for your engine to turn those tires by transferring more of your torque to them so you'd be able to be lighter on the throttle to get yourself through the lower gears
 
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