Ford KA Rally Car Exhaust sizing help?

[RedLexus]

Hi all , I use a 1300cc Ford KA Rally Car with the Endura Engine (injected Ford Crossflow FWD), engine specs that I know of are ; bigger (single) throttle plate , fast road cam , mildly polished cylinder head , Motec ECU , with a 4-2-1 Exhaust system , running a single silencer . I need to build a new system , from the 2-1 collector back , what would be the recommended exhaust Inner diameter ? These engines in rally trim deliver approximately 90-100bhp . I normally rev it to 6500 rpm , top end power is not good at all though . I would like it to have most useable power between 4500 and 6000 . Thanks in advance.

[RedLexus]

I should have added , the secondary pipes are 38mm outer diameter , So I assume they are approx 35mm I. D ? and the current system is 45mm OD near the collecter , and steps up slightly near the rear section . I suspect the rear , from the axle back , including the (Janspeed) silencer is a "fast road" item . One rarely sees fancy rolled stainless/chrome trims on Rally exhausts!

[RedLexus]

I did read the thread viewtopic.php?f=1&t=4 "Fiat/Lancia Twin Cam exhaust systems" , and noted that in particular this quote "If the manifold is a 4-2-1 I would go for secondaries of 25% larger than the primary and keep the same diameter for the exit pipe downstream of the secondaries." Going by that , if my secondary pipes are 35mm-36mm I.D . , that the 38 mm system should be ok? Or does the act it's not "straight through" , affect that?

[Guy Croft]

Can I have the ex valve size and port size please?

Assume ex port is circular?

GC

[RedLexus]

Can I have the ex valve size and port size please?

Assume ex port is circular?

GC

Ah..I was afraid you'd ask that . I don't have those dimensions , the head hasn't been off , and no-body I've asked can tell me . Would the diameter of the primaries be any use GC?

[Guy Croft]

Take the header off and give me the port size only then.

Could you please email me with your Pat's phone no? (re the 16v unit).

BTW I know the exact cause of the 'walking cambelt' now but can't find the thread, perhaps you can and put the link here to save me time.

GC

[RedLexus]

BTW I know the exact cause of the 'walking cambelt' now but can't find the thread, perhaps you can and put the link here to save me time.

GC

here you go my friend .
viewtopic.php?f=6&t=1599&p=8358#p8358