4.2 and 4.5 exhaust

[gcpeters]

so i was out in the sun today, and was thinking, for some reason...

what is the difference between the 4.2 and 4.5 exhaust

why wont ones de-cats fit the other?

is the 4.5 better flowing? dif manifolds etc?

also whilst pondering i noticed a small control box behind the cigarette lighter/central speaker - what this for then!! (still never fixed my cig lighter)..

[Steve_T]

Re. the de-cats, they are different lengths between the 4.2 & 4.5 hence they cannot be swapped.

[optimax sniffer]

4.5 is 16 inches long
4.2 is 17.5 inches long

[Byker28i]

Why is that though? Is the manifold or head design different so the manifolds finish 1.5" further towards the front?

[gcpeters]

Byker28i said:

Why is that though? Is the manifold or head design different so the manifolds finish 1.5" further towards the front?

indeed!
why did they do that!?

reason im asking is im going for a 4.2 to a 4.5 upgrade soon and wonder if the exhaust might cause issues! and if there is benefits to the 4.5 one..!

[gcpeters]

gcpeters said:

Byker28i said:

Why is that though? Is the manifold or head design different so the manifolds finish 1.5" further towards the front?

indeed!
why did they do that!?

reason im asking is im going for a 4.2 to a 4.5 upgrade soon and wonder if the exhaust might cause issues! and if there is benefits to the 4.5 one..!

can anyone shed any light on this? or is it a mysssterrryyyyy lol

[SimonSparrow]

I think the 4.5 system is slightly larger diameter, hence 4.5 backboxes not fitting 4.2s. I know when I had my manifolds replaced years ago, you could only get 4.5 ones, but Andy at APM said they were 'bigger bore' which made me feel better at the time about the expense.

[robert dorman]

4.2 & 4.5 exh pipes are the same size the two pipes after the cats is the difference the 4.5 is longer, diameter is the same.

[350Matt]

robert dorman said:

4.2 & 4.5 exh pipes are the same size the two pipes after the cats is the difference the 4.5 is longer, diameter is the same.

not on my 4.2 old cerb, I replaced the back box with a 4.5one and had to fit some sleeves in order to get it to clamp onto the 4.2 pipes.

I'm pretty sure the entire 4.5 system is about 1/8" bigger bore throughout than the 4.2

possibly on later 4.2's than mine (98) the exhaust system was the same as the 4.5's?

Matt