Modern superchargers have a bypass valve. No boost on coast or cruise.

I had a 2003 Supercharged Nissan Frontier and my wife (at the time, good riddance) had a 1997 Nissan Pathfinder. It was about a 1mpg difference between the two.

Josh

 

Couple of things:
Nobody puts a blower on that is really concerned about MPG.
Both of my GT500's beat the gas guzzler tax, by being able to get 23 MPG.
There is a dealer in the U.S. selling Mustangs with a Roush blower kit & a 3/36 warranty.
.

 

The big detriment with a supercharger is that it spins with the engine, which imparts parasitic drag that burns more fuel. Going down the highway the engine has to make power to spin the supercharger even if you're not using the added boost.

I wouldn't expect the MPG drop to be huge, but it will certainly be noticeable. More noticeable may be the reduced longevity of the powertrain that was never built to deal with the increased power load, but that may not come into play until well after 100,000 miles depending on how it's driven. Powertrain components will certainly fail sooner under the additional load...how much sooner is anyone's guess.

 

This is ironic, be cause the buzz I remember hearing back in the 90's was that ALL cars should have a supercharger. This of course was at a time when turbo lag was measured in seconds rather than the milliseconds we are used to today.
But many articles I remember reading in Car and Driver, MT and R&T touted the MPG gains vs un-boosted as the motor did less work doing the mundane work the daily drivers did. Unless you got on it, the mpgs went up by several.
Remember the late 90's grand prix GTP? Those were a dime a dozen, using a roots type SC and proved to be no less reliable than the other crap GM was putting out then that were NA.

A good SC install and tune on a 5.0 should yield decent mileage gains if driven in a way that would concern one of gas mileage.

Of course if you are anything like me, putting the pedal in the fun range happens as often as possible. I would happily be burning more fuel per mile.

 

Can you reference any of that? Just ran some quick numbers on the factory supercharged Bonneville vs. it's N/A brother. Supercharged model got 2 MPG less.



Exactly what is a supercharging going to do to increase combustion efficiency? Particularly when you incur the parasitic drag caused by spinning the unit whether it's providing boost or not?

 

Copy and pasted from various sites....

Will installing a supercharger kit kill my fuel economy?
How will a supercharger affect my fuel economy?
With the addition of a supercharger kit, your average miles per gallon (MPG) will change. That change can be an increase or decrease in fuel economy depending on your driving habits and application.

Often an increase in fuel economy is seen under standard driving conditions with the addition of a supercharger. A 2 to 3mpg increase is not unusual under normal daily driving conditions. This gain can be attributed to the supercharger reducing the pumping loss of the engine. This loss can be better described as the vacuum force produced by the engine that is required to actually pull the air/fuel mixture into the cylinder. The supercharger helps this process by equalizing cylinder pressure and effectively helping to ‘push’ the piston to the bottom of the intake stroke, increasing engine efficiency.

One reason owners often say there is a loss in fuel economy when adding a supercharger kit to their car is that most owners find it difficult to keep their foot off the mat! Under supercharged racing conditions, fuel economy decreases due to the engine’s increased ability to produce horsepower and torque. This increase is generated by consuming a greater quantity of fuel and air. Simply stated if you drive hard or race often your average miles per gallon will decrease. This is similar to the fuel economy loss seen in a naturally aspirated engine under extreme driving conditions.


.....
But wow, I guess I cannot find anything much more than that. And this is a company that looks like they sell superchargers.....so let's keep that in mind.

In my quick research I did read that roots type SCs are less efficient than centrifugal ones.

 

If you buy Roush Supercharger Phase 1 600HP option and have Roush Authorized Ford Dealer install it you cam also purchase $900 warranty 3/36,000 that covers everything that has to do with Supercharger Power/Train ... if you opt for Phase 2 650HP warranty is not available.

 

I have a 2016 roush 5.0 !50 . 18-20 on highway and 13-16 in town highways is at 85mph in town pedal to aluminum lol

 

These are impressive numbers!!

Have you hand calculating them or is this what shows up on the fuel mileage indicator?

 

I can only vouch for the 2.9 whipple supercharger and it was installed on a 6.2 liter raptor. It dropped from 15.5- 17.2Mpg to around 10-11 Mpg. It did have 20' wheels and 37's as well, so i wouldnt imagine as much of a drastic change with stock wheels and tires. HP at the crank was about 650Hp and it sure is a fun truck to drive.

 

When pressing on gas pedal hard do yoi guus have knock in the rear, feels like hard shift

 

I have a Roush F150 SC with the roots blower. My combined driving average lately has been around 17mpg per tank.

 

I am wondering if anyone with Roush Supercharger noticed or experianced this. When under hard acceleration I hear and Feel Loud Thumb coming from the rear ...it feels almost like a Hard Up Shift but sounds is like metal hits metal and I think its coming from the back. It only happends once under hard pull probably around 45 miles like I said feels like a hard UP Shift and sounds like a Knock.

 

5 Star Tuning Just got done putting a Roush Supercharger on a 2018 F150 5.0 XLT with great results check there Facebook page for 5 Star Tuning Mike is at it Again!!!