I have a 2003 f150 supercrew 4.6, when I bought the truck it was not as strong as my 2003 supercab 5.4. I bought a sct x4 and installed it on the supercrew, 87 octane tune made a bit more power nothing worth bragging about. The sct asks if you have a 4.6 or 5.4, I decided to try selecting 5.4 and it worked WOW WHAT A DIFFERANCE, my truck runs like a 5.4 was installed, no more 4.6 slugish lag this thing has a lot more power. Nice smooth running no pinging, just as much power or more than my 03 5.4. I was wondering if there will be any long term I'll effects ?

 

Doesn't make much sense honestly. Not even sure why the SCT programmer would ask you what motor you had cause none of mine every did. Whoever loaded the tune on the device should already know your vehicle so I'm assuming that you have canned tunes. If you are noticing such an extreme difference in power, which would be rare especially on 87 octane, I would think the "5.4l tune" is making your truck run very rich. Running rich for too long will have issues and running lean for too long has issues as well which is why it's important to have a proper tune for your vehicle's modifications/motor. Your 4.6L with a canned 87 octane tune should NOT be making power worth bragging about so it sounded like it was working the first time.

Just trying to be honest but as I said, a 2003 4.6L with a canned 87 octane tune is pretty much worthless in all my years owning these trucks. I wouldn't be surprised if you gained a little power but it shouldn't be as noticeable as you're saying, in fact it probably shouldn't be noticeable at all unless it was a custom tune.

 

I am in general agreement with the last reply.
Here is why,
the difference in displacement between the two motors is huge.
262 cu/in vs 330 cu/in displacements.
As such the fuel and ignition timing versus load will be greatly different in order to follow design guidelines and program self adjustability for normal operation.
A 5.4 tune, even stock in the PCM tables would tend to be to much timing advance for a 4.6 displacement.
The fuel and timing is derived from the final Logic decisions made in the PCM from all the sensors that have input to that decision making, at any given moment in time.
I agree you have likely saw a difference but is should not be radical because there is not normally that much power available from a software change without hardware changes to make the extra power.
For example a change in the transmission software control of main fluid pressure at shift time would be very noticeable but is not due to engine power but higher fluid pressure in the transmission. It could be mistaken for greater engine power just from the feel of sharper shifting (read as less slip).
But it makes good marketing.
Glad your happy with the result.
Good luck.

 

Fify.

 

Yes, I did mess up the 4.6 displacement.
Slip of the fingers I guess.
Good luck.

 

Hey thanks for the replies, yes I agree about the running rich, I will do some data logging and maybe pull a plug and have a look. The thing is it has the 5.4 low end torque that I have missed with this 4.6, it also opens the intake manifold tuning valve at 2500 as apposed to 3000 rpm. The lag between 2000 to 3000 rpm is gone. Off idle to 3000 rpm pulls a lot harder just like the 5.4, I have had 2 f150s with the 5.4, 99 and 03 both supercab, this 03 supercrew I bought because it has low mileage, I'll just leave it as be and if it blows I'll put a 5.4 in it.