Ford Mustang Forums banner

1 - 9 of 9 Posts

·
Registered
Joined
·
1,963 Posts
Discussion Starter · #1 ·
After adding heads, cam, injectors, afpr, and having my intake ported my milage has dropped in half. Witch can be pretty pricey when running 92 octane on a daily driver. WTF some guys are getting better than stock milage after h/i/c upgrades.

I'm idling a little rich but that is normal with a 15511 cam and speed density. My fuel pressure is at 40 psi right now. I turned it down to 37 psi and went throgh the gears to red line and then parked it and plugs looked a little white. So I turned it back up.

I pulled 8 psi of vacuum from the intake witch I thoght was kind of low(22 psi with stock cam). I spayed carb cleaner every where and could not find a leak. I had an exta set of intake gaskets so I reinstalled my upper and lower intake any ways, but it did not make a difference. All the vacuum lines are were they should be and seam in good shape.

Do you guys think a mass air conversion would help my milage. The Crowler cam I'm running is speed density compatable but as mention above does idle pretty rich. Thanks for the help guys.
 

·
Registered
Joined
·
417 Posts
i face the same problem! i dunno if converting to M.A. is going to help because i have a 93. my gas mileage sucks ass. anyone that can help us out, duffman and i will bring over a keg of duff
 

·
Registered
Joined
·
1,075 Posts
Is that Hypertech chip supposed to be compensating for those 24# injectors? If you are idling rich, it isn't. If you didn't have the chip burned to exactly match your combination, you will have problems with bigger injectors on a speed density car.

On a side note, any cam that costs you low end torque causes the engine to work harder around town - hence, lower gas milage in that situation. You might try checking your milage on an open road trip. You might find that the before and after highway numbers are a little closer. Also, I've found that I can improve my milage by getting a little of the lead drained from my foot. Lead in the foot tends to build up after HCI installs. :)
 

·
Registered
Joined
·
78 Posts
Yeah. The chip will do wonders for gas mileage. My car got excellent mileage with the chip and H/C/I compared to stock and no chip. Mileage was actually much better than stock.
 

·
Registered
Joined
·
505 Posts
It's really simple... your MAP sensor is only seeing 8"s of vacumme so it thinks your always at part throttle & dumping in that much more fuel.

The vacumme that that the MAP see's is converted into a signal
for the ECA that interprits the "load" on the motor. High vacumme = idle low vacumme = part throttle or WOT. That is how speed density computer determine the enrichment....(that & a few other sensors :))
 

·
Registered
Joined
·
162 Posts
i think your real problem is a lead...in your foot that is. The less you press down the gas pedal the less you burn gas. A simple consept.
 

·
Registered
Joined
·
505 Posts
Well i'm 100% sure on a Speed Density car that only see's 8" of vacumme will send the gas mileage to hell in a $#!t coated handbasket in no time
 

·
Registered
Joined
·
1,963 Posts
Discussion Starter · #9 ·
Lots of 5.0 experience said:
Is that Hypertech chip supposed to be compensating for those 24# injectors? If you are idling rich, it isn't. If you didn't have the chip burned to exactly match your combination, you will have problems with bigger injectors on a speed density car.

The off the shelf chip has a more aggressive timing and fuel curve than the stock computer, but it was ment for a mostly stock car. With my h/c/i and 24# injectors, I increased air and fuel flow farely evenly, and I did not get any detination or lean out so I tried running it for a bit. Plus I ran my car with stock injectors for 2 weeks after my h/c/i upgrade and it still idled rich.

Today I ended up pulling the chip and reseting the computer. Performance did not seam to change, but the car is still idling rich. I will let you guys know if my milage has improved.
 
1 - 9 of 9 Posts
Top