I did a test a little while ago that might interest some of you.

I freshened up my motor about 6 months ago and left the turbo system off for the first month or so. Once I got the tuning dialed in NA I used the data logger on HP tuners to do a simple gas mileage test. I set the logger up to read the amount of fuel in the tank. This is much more accurate than using the stock guage. I then wrote down the current mileage on the truck. I drove on the freeway at 70 mph for about 30 minutes then recorded the mileage and fuel level again. I got about 16.8 MPG. I then turned around and headed back home and did the test again. This time I got about 17.2 MPG. That's an average of 17 MPG. Not bad for a healthy 6.0.

Then I installed the turbo system and did the same test. No joke I jumped up to 23 MPG! Granted this was strictly freeway driving with no boost involved but it was still a huge increase. This is what I love about a turbo. I can drive all day long without boost getting great gas mileage then when it comes time to have some fun I can do that too!

I would love to have more people do some testing like this and post up their results.

 

I have a subaru outback with the turbo and it gets way worse gas mileage than the na guys with the same 2.5l engine. It is still restricting air flow if it is not pumping so I see no way you can increase your mpg's adding a turbo. It is a drag on the engine. If I baby my outback I can get 26 going about 65-68. NA guys get over 30 easy. That being said, both of my vehicles are FI.

 

It can be said that most of the MPG gain was found via Tuning.

 

When I picked up my truck after the 365 install I put it on cruise 60 for about 35 miles. I showed 25.6 as the average...pretty remarkable. Shortly afterwards I started bangin' on it so I don't think I ever checked it again.

 

I just went to san antonio and back the other night and filled up before i left, and on the way back the mpg on the DIC was saying 17.7 I thought no way but I went and filled up the truck when I got back and sure enough I got 17.3 or so. Alot better than the truck got with the radix or na lol. This is a crew cab 4x4.

 

AFR, fuel trims and timing were virtually identical as far as the driveability so I don't think tuning was really the main factor. The turbo makes the air more "readily avaliable" at all times. When I am on the freeway now with the turbo I make less vaccum because the turbo is always spinning and pushing air towards the motor even if it isn't forcing it in.

 

I find that description of the gain hard to believe. I am sure you know that the pump wheel requires speed in order to move air out past the discharge area. Under normal driving conditions (no load) that turbo is not doing ANYTHING other than sitting there. In order for you to make less Vacuum you would need to be in boost....therefore making your statements of not being in boost during normal driving untrue. I would rather you make the statement "gas mileage was greatly improved due to the tuning, and power has increased from the turbo". This would have been a true statement.

 

Quote:
Originally Posted by Turbo 6.0 View Post
AFR, fuel trims and timing were virtually identical as far as the driveability so I don't think tuning was really the main factor. The turbo makes the air more "readily avaliable" at all times. When I am on the freeway now with the turbo I make less vaccum because the turbo is always spinning and pushing air towards the motor even if it isn't forcing it in.

Exactly what Brian says, If you have a MAF system and you are in a lessor state of vacuum (closer to atmosphere) while cruising than when you were N/A the computer sees that as more airflow to the engine consequently requiring more fuel flow (for a given TPS reading). If you have tuned the maf table vs. tps down to lean out your part throttle cruise I could possibly see this gain being a combination of Tuning and Turbo requiring less throttle input to get to speed and stay at that speed.

 

on the sts website they do this test on a corvette with the same results. from what i understand the turbo helps adomize the fuel at all times.

 

How could that be possible? Again, the turbo is not doing anything under normal driving conditions.