Pontiac GTO Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
1,017 Posts
Discussion Starter #1
At idle my Throttle Position Sensor (TPS) it's at 16%.

During a freeway cruise it will read 27% - 35%.

Are these within specs?

I'm asking since my GTO is averaging 15MPG since my rebuild.

That is down from 20MPGs that I was getting before.

There are a few things that was changed that may have reduced the fuel economy:

- lower 10.5:1 compression ratio
- upgraded to Ferrea beehive springs (higher spring rates than stock?)
- swapping out the Maggie 112 stock 2.8 pulley for a 2.6 pulley.

Tuning my GTO for the new mods didn't make a difference in MPGs.
 

·
Premium Member
Joined
·
4,162 Posts
Well your compression could have an effect on MPG's and if the engine is still tight then that can have an effect too. The supercharger is pretty much unloading when crusing. Also the time of year and the change in fuel blends could have an effect too. My MPG vary all over the place and I don't really change my driving habbits. Most of it has to do with the season and fuel blends. I go fro 14-17.5 MPG city like driving. I don't do much highway but its usally around 23-26mpg if I do.
 

·
Registered
Joined
·
3,765 Posts
My fuel economy is about the same all year. 18-19.5 with mixed driving, probally 60-70% highway. I do think it goes down a little in the summer, not because of the fuel, but because I drive it more agressive since the roads are nice and clean.
 

·
Registered
Joined
·
1,017 Posts
Discussion Starter #4
Well your compression could have an effect on MPG's and if the engine is still tight then that can have an effect too. The supercharger is pretty much unloading when crusing. Also the time of year and the change in fuel blends could have an effect too. My MPG vary all over the place and I don't really change my driving habbits. Most of it has to do with the season and fuel blends. I go fro 14-17.5 MPG city like driving. I don't do much highway but its usally around 23-26mpg if I do.
I've got 3k miles on the engine so far using dyno oil for break-in.

Nothing has changed for the better. Maybe 1MPG improvement. My highway used to average 28MPGs at 2k RPMs in 6th gear. And city was 15mpg. Now everything has dropped where my average is like my city driving.
 

·
Premium Member
Joined
·
4,162 Posts
You have to realize that you went from an unknown tune that was possably really lean to begain with to a different setup with possably a better tune.
 

·
Registered
Joined
·
1,017 Posts
Discussion Starter #9
Swap it back and see what you get. It's not that hard to change, is it?
I may do just that.

First I need to have him check my TPS since the readings are higher than normal.

Dunno how much that effects MPGs.
 

·
Banned
Joined
·
2,777 Posts
At idle my Throttle Position Sensor (TPS) it's at 16%.

During a freeway cruise it will read 27% - 35%.

Are these within specs?

I'm asking since my GTO is averaging 15MPG since my rebuild.

That is down from 20MPGs that I was getting before.
TPS readings are totally normal. You will also notice that at WOT, TPS reads 88%. Explanation here HP Tuners Bulletin Board - View Single Post - 2005 A4 GTO Help please.

As for your mileage, your tune might be a little on the rich side. Without being able to look at a wideband, who knows? What do you know about your tune?
 

·
Registered
Joined
·
1,017 Posts
Discussion Starter #11
My AFR ratios at boost is 11.5:1

Dunno what non boost are.

There is no smoke coming from the tail pipes with straight threw exhaust at start up or WOT.
 
1 - 11 of 11 Posts
Top