This subject came up at our Irvine lunch meeting today (thanks for putting it together Ted).

Will replacing the stock pipe with the Z-Tube increase your gas mileage? Does the less-restrictive and cooler airflow make a noticable difference. I'm getting 17-18 MPG and any increase I might get with the new tube would more than justify the cost. I imagine the same question would apply to a pop-charger as well.

Z-Tubers what have you seen?


Thanks,

Doug

 

More and cooler air will require the ecu to add an appropriate amount of gasoline to maintain the mixture at 14.7 AF at cruise.

I doubt that any changes to the induction system prior to or after MAF can change things [air flow or temperature by more than 1%].........actually 1-2" WC/27.7=0.0722 x 0.068 ~~0.049 so really 1/2% is more like it for air flow and 5.5F drop would be another 1/2%..........these are gigantic improvements over oem designs........not sure they are realizeable from Z tube.

 

My milage got worse....cause I am addicted to that awsome growl that it provides, not to mention the extra pull that I get with my foot on the floor! LOL!!!
MB

 

What about less restrictive exhaust, will this help gas mileage?

 

My gas mileage stayed the same.


BLKSNAKE - '04 G35 Coupe
Check out my hidden sub! [img]/w3timages/icons/laugh.gif[/img]

 

i know this is off topic..but ithought the CAI helps gas milage...wouldn't it be the same case?

 

Nothing you add can help gas mileage, because at cruise rpm the input and output restrictions are almost non existent as the air flow is so tiny. Restrictions only begin to show themselves above 4,000 rpms and only become significant above 6,000 rpms.

The throttle is the major restriction at all rpms except WOT otherwise the engine would run wide open and explode.

Using a non oxygenated fuel will help [3-5%] since oxygenates fool O2 sensor feedback system.

At a constant speed the engine must turn X rpm to make that speed ...........less air less fuel required.......unfortunately the catalytic convertors require 14.7 AF ratio.

Manufacturers look for every tiny improvement because they are taxed on MPG.

Obviously you could redesign the diff ratio [and change speed sensor] so that at a given speed the engine turns fewer rpms.

Many so called performance mods actually decrease MPG in acceleration and at best do nothing at cruise rpms [under 3,000 rpms].
Some air filter housing mods screw up the calibration of MAF and make mpg worse until O2 feedback loop corrects the error.

 

Hmmm ive seen a lot of people with the pop charger and z tube combo, but does anyone have feedback on any of the aftermarket CAI systems AEM/Injen/Stillen/Typhoon etc? and has anyone used the Bltiz SUS intake? Even though mileage may not improve a substantial amount i was wondering which option would be the best to choose for performance?

 

Measure the vacuum restriction of oem air intake system infront of TB and compare with any less [more] restriction of an aftermarket..........that will be accurate to a 1/100 of a percent in telling you how much more air is flowing.

Reading the grams per second peak flow thru MAF [via OBD2 scan tool] corrected for temperature and barometric changes will tell you within 2% accuracy how much more air is flowing into engine.

11F hotter temperature will reduce air density by 1% so will a 1.0" HG barometric pressure change. Humidity can change density by up to 2% depending on temperature.
http://www.engineeringtoolbox.com/8_680.html
http://wahiduddin.net/calc/calc_da_rh.htm

Winter to Summer 32F>100F can reduce density by 11% at the same barometric pressure.

 

i dont know if the z tube is right for you if you are concerned with fuel economy. it is a "performance " upgrade. not a fuel economy upgrade. in order to benefit from the z tube you need to hit high rpm's the dyno sheets of before and after show that you lose quite a bit of low end torque but gain a bit in he upper rom range. i dont know about you but 90 percent of my driving is done between 1k and 5k.

 

Many of the convoluted things the factory does are to tweak out the last 0.01 mpg highway.........sometimes it is very important as 24.491 mpg [would be shown as 24 mpg] suddenly becomes 25 mpg.

 

Q45tech,
I always feel enlighted after I read your informative posts. Thank you!



BLKSNAKE - '04 G35 Coupe
Check out my hidden sub! [img]/w3timages/icons/laugh.gif[/img]

 

"Nothing you add can help gas mileage"

The plenum will increase gas mileage significantly!

2003.5 DP 5AT Sedan (E-thing but Nav)
14.2 @ 97.18
Z-Tube
K&N Drop In & Airbox Mod
10 Wire Hyper-Ground
Crawford Plenum (V4)
UR Crank Pulley
Polk EX-3500 Tweeters/Shock Sensor/H-Liner

 

My mileage initially was worse, but after about 200 miles after install my mileage went back to normal. I avg. 19-20 MPG. My car feels faster to me now and I'm happy with the Z-tube.

Charog
"I'll Be Your Huckleberry"

 

Would loosing weight (car not me...) help in increasing mileage? Say....lighter rims and....I'm really not sure what else you would do..take out the spare? But thats not that much weight....just a thought...