1998 pcm?

[jgemienhardt]

I was looking up some specs today, and noticed that the 1998 Expedition is listed at 230hp and the 1999 is listed at 260hp. I have looked over both models, and I am not seeing anything different. Could I just swap the PCM from a 99, and get better numbers? I was thinking it might just have a better programmed tune from ford on the 99 vs the 98. Any and all thoughts are welcome. Thanks.

 

[bedrck46]

The below information was copied from the 98 and 99 owners manual

98
Engine 4.6L engine 5.4L engine
Cubic inches 281 330
Horsepower 215 @ 4400 rpm 230 @ 4250 rpm


99
Engine 4.6L V8 engine 5.4L V8 engine
Cubic inches 281 330
Horsepower 215 @ 4500 rpm 235 @ 4250 rpm

Also its not just a matter of swapping PCM'S as any change in the PCM has to be reprogramed to the vehicle that it is being installed in

The other thing to consider is that there are wiring changes that are different between the 98 and 99 model years

 

[FordandPolaris]

The main difference is that the 99 utilizes PI heads and the 98's do not. That is where the HP bump comes from.

 

[toms89]

The main difference is that the 99 utilizes PI heads and the 98's do not. That is where the HP bump comes from.

^^ This. PI heads and intake!

 

[jgemienhardt]

thanks everyone for the info. Not really worth the time and effort for a 5hp gain. Although, on an F150 forum I read that if the PI head is put on the NON PI block it would bump the compression from 9.0:1 to 10.5:1. there were no actual numbers on the hp gain it would give, but while I am still at an automotive tech school that has a dyno, I may just do it for fun and see what Ol' Blue Thunder puts down. lol I will post my findings in a few weeks.

 

[toms89]

98 - piston 10.49cc dish, non-pi heads 51cc combustion chamber
99 - piston 18.10cc dish, PI heads 42cc combustion chamber

So yes 98 pistons with PI heads does raise the compression to near 10 to 1. With the PI swap you would see slightly better power than the rated 260 hp for 99 and up 5.4 2v motors. You may consider backing off the timing accordingly at high loads though ford does leave some timing on the table for safety so how much is questionable. A premium fuel tune should see some appreciable gains in performance with the higher compression.