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Curly1 · 10-10-2008, 09:44 PM

The tires (or lowering?) have helped. I was looking back over my notes and testing and it defnatly has helped. For instance I have went from 29.4 MPG @ 70 to 32.25 @ 70 MPH and if you add in the 10% speedometer error then it is 35.47 MPG. Note my GPS is only showing about 5% error? and all the tire web sites says there is a 10% difference with those tires?
That is with the air conditioner on high (it is Texas!) and I try to do the same 150 mile test run and test mileage at several speeds both directions. I try as much as possible to eliminate me as a variable. I record weather, altitude, wind, put it on cruise at the testing speed then clear the DIC and make a 20 or 25 mile test run.
Went from 37 @ 60 to 38.4 MPG and if you add in 10% speedometer error it is 42.24. RPM has been lowered 100 to 250 RPM at highway speeds.
One of the reasons I tested at speeds up to 85 MPH is because I do not feel the lowering and front spoiler will make much difference at low speeds such as 40.
I have not done any real testing with the front spoiler yet and not sure if gains will even show but I do not think it will hurt anything.

I think aero dynamic mods will help more at higher speeds and horse power like underdrive pulleys and removing wieght will help more at the lower speeds. Actually I think (hope) the underdrive pulleys will help at all speeds.

Once I get the mechanical mods where I want them then I will try to learn more how to drive effeciently. I know speeds over 60 or 65 is not effecient but it was needed for my testing.

My goals may be a little different than many here. I want to get the best mileage possible with out giving up my creature comforts. It is often over
100* here and I am not going with out my air conditioner. I drive a car to get to where I need to be so I want to tune my car to get the most out of it at the speeds I drive 60-70.
I am trying to build a car that gets good mileage, looks good, comfortable and is fun to drive. So what I consider "good mileage" may not be very impressive to many of you. Curly

10-10-2008, 09:44 PM	#11 (permalink)
Curly1 EcoModding Lurker Join Date: Oct 2008 Location: United States of Texas Posts: 43 Princess - '08 Chevy HHR LSSR 90 day: 23.66 mpg (US) Thanks: 0 Thanked 2 Times in 1 Post	The tires have helped The tires (or lowering?) have helped. I was looking back over my notes and testing and it defnatly has helped. For instance I have went from 29.4 MPG @ 70 to 32.25 @ 70 MPH and if you add in the 10% speedometer error then it is 35.47 MPG. Note my GPS is only showing about 5% error? and all the tire web sites says there is a 10% difference with those tires? That is with the air conditioner on high (it is Texas!) and I try to do the same 150 mile test run and test mileage at several speeds both directions. I try as much as possible to eliminate me as a variable. I record weather, altitude, wind, put it on cruise at the testing speed then clear the DIC and make a 20 or 25 mile test run. Went from 37 @ 60 to 38.4 MPG and if you add in 10% speedometer error it is 42.24. RPM has been lowered 100 to 250 RPM at highway speeds. One of the reasons I tested at speeds up to 85 MPH is because I do not feel the lowering and front spoiler will make much difference at low speeds such as 40. I have not done any real testing with the front spoiler yet and not sure if gains will even show but I do not think it will hurt anything. I think aero dynamic mods will help more at higher speeds and horse power like underdrive pulleys and removing wieght will help more at the lower speeds. Actually I think (hope) the underdrive pulleys will help at all speeds. Once I get the mechanical mods where I want them then I will try to learn more how to drive effeciently. I know speeds over 60 or 65 is not effecient but it was needed for my testing. My goals may be a little different than many here. I want to get the best mileage possible with out giving up my creature comforts. It is often over 100* here and I am not going with out my air conditioner. I drive a car to get to where I need to be so I want to tune my car to get the most out of it at the speeds I drive 60-70. I am trying to build a car that gets good mileage, looks good, comfortable and is fun to drive. So what I consider "good mileage" may not be very impressive to many of you. Curly