Originally Posted By Rog
I believe there are few difference between a 4/4 and a Plus 4 Duratec of that age.

These are the ones that I know of :-

The cut of the wings to suit the tyres determines the width.
The diameter of the bore in the block to reflect the 200cc engine difference (the bore/stroke is square on a 1.8).
The diameter of the inlet/exhaust valves.
The 1.8 has a throttle body mod to prevent the butterfly fully opening to limit performance (that can be removed smile ).
And a huge price difference!

I think that I have just stumbled across another subtle difference between the 1.8 and 2.0 that might be worth a mention.

Since owning my car I have been on an obsessive mission to eradicate the pre-ignition that affects my engine. I have tried just about every trick in the book and then some. Although it has been improved significantly from the early days particularly with help from the factory, there is still a tiny bit remaining on occasions. After endlessly trawling the Ford forums for info on the dreaded Duratec pink there was a pattern regarding the 1.8’s that very often could not be fixed despite their owners relentless endeavours. This had been gnawing away at me for a while and curiosity got the better of me last week when I embarked on another little experiment that I had been musing over for some time. On the face of it a crazy thing to do but I loaded a standard 2.0L Plus 4 tune into a spare ecu and dropped it into the 4/4.

And what a surprise, it ran like a dream. And guess what, my last bit of stubborn pre-ignition had gone...totally! Typically previously when cursing say at a steady 2000rpm with the ecu in closed loop mode ( I assume), if I lightly pressed the throttle when the conditions were right there would be a brief metallic “clink clink” for a fraction of a second until the knock sensor retarded the timing. Barely audible I know and I’m sure most owners may not even care or notice but for Mr Picky it was really really annoying, a real spoiler hearing the pistons rattling. Now it is a delight to drive with just a deep exhaust note whenever the peddle is pressed. The other curious thing was the running temp was 4/5 degs down (I’ve had an obd reader connected) . So I suspect the lambda parameters may have been set different on these two engines and the 1.8 is configured to run leaner? I’m guessing but with a subtle tune difference and also the TB restriction, perhaps Ford intentionally de-tuned the 1.8 for economy.


Roger
2011 Plus 4