600 horses

I have a 99 silverado 5.3.
Performabuilt with 1200 flash stall
Latest factory tune
Custom CAI.
This is my daily driver and may eventually do more, but I'm wondering what happened to the mileage. I was getting around 18 mpg and now I can't get more than 15. I know it will use more fuel than the factory set up, but I didn't think that with the trans and CAI it would drop it that much. It isn't kicking any codes either. Any help is greatly appreciated.

terravast4

iTrader: (25)

i took a hit on MPG with my performabuilt trans and a 300 stall . I just installed a finish line level 7 and a circle d converter and immediately saw a difference in MPG. Im thinking it might have been the converter

Slow05CC

iTrader: (1)

The stall is what is hurting your mpg. I was getting around 18 mpg with longtubes, 430 gears and stock converter, on stock 20 with 275/55s and a custome tune. I lost about 3 mpg when I put the 3000 stall in and then lost about 1 mpg from the 220 cam. On average I get about 14mpg now, not too bad for a heavy crew cab with gears, cam and stall. Ok can also get about 5 mpg if I stay in the throttle!

600 horses

Thanks for the time. I wanted to make sure there wasn't something I was missing. Because my converter stays locked most of the time driving.

2xLS1

iTrader: (25)

If your CAI has a big open element air cleaner under the hood then it is really a HAI hurting performance and mileage.

GMC93

So you're saying that higher intake temps are to blame?

FFDP

iTrader: (2)

The warmer the air is, the more efficent the motor is. For fuel mileage that is, thats why you don't get the same gas mileage when it -10º outside comapred to 75º.

And there is likely maybe a 5 hp difference if that if you compared a HAI and CAI in real world conditions, it just doesnt matter that much.

erickcastillo95

iTrader: (1)

dam thats still good i get 9 mpg or less on my cammed 6.0 2 door tahoe it sucks i hate it ....and yea could be your converter

2xLS1

iTrader: (25)

Baloney. Hot air is less dense and makes less power. The pcm calibration pulls timing out of the tune as IATs go up. I see IATs of 160-190 degrees here in Okla on trucks with supposed CAIs with open element air cleaners. There was a K&N open element kit on my 04 when I bought it. I have data logs of my truck idling in traffic with IATs over 190 degrees. I took that crap off and gave it away. I'm now running a stock airbox with an Airaid tube. I love hooking up my scanner and showing people what their IATs are with their supposed CAIs.

madmann26

iTrader: (7)

Not trying to start a thread war,

But this is correct. In the IAT spark table, there are modifiers to pull timing if the IAT temp is X degrees. On the Gen3 motors, I think it can pull upwards of 10-degrees of timing at times.