I have a 2003 focus st170 and have a 4-2-1 race manifold to go on and was going to put a scorpion race cat on and then a full scorpion back system on.Now people r saying I should just decat it that that would be better but what about the lambna sensors will they not put up the eml light and will that then not put correct fuel mix in and be heavy on fuel. Also when I change the manifold can I keep the heatsheld of so I can c the nice chrome manifold without having any heat problems in the engine. Thanks

 

lets face it the st170 is shocking on fuel anyway so if your expecting economy then a 4-2-1 and a scorpion system was a mistake but as you have them I would not worrie,on a st I would heat wrap it as well known for cooking the sump

 

I never said I was looking economy I said bout the sensors and the eml coming on I know its already hard on fuel.So what do I do bout the sensors and eml if I decat it?

 

It's got a 4-2-1 manifold as standard. You will see no noticeable gains on doing any of that, the standard ST170 exhaust system is very good.

 

As I understood it they also have a sports car as standard too. When I had my 170 and looked into it I got told a decat will make virtually no difference. I'd just go cat back for noise and looks personally. If you want a power increase get a vernier pulley

 

It doesnt have a 4-2-1 manifold as standard or a sports cat either.I might not no much bout cars but I definitely no that the st170 did not come with them fitted.If u dont no what ur talking bout u shouldn't be trying to advise people on things u no nothing about.

 

Er, suggest you go look under it then!

 

kyle offered valid advice and if you dont wish to listen then fine but theres no excuse for blatent rudeness





sort of prooves you DONT know MUCH about cars, ST170 Std exhaust manifold btw 4-2-1

 

I was going to say mine had a 4-2-1 manifold that was standard and every other st170 I've seen had one fitted. I did say I wasn't sure if the original cat was a sports one but I had been told they were which is why I never went for a decat.

 

yes the original ford cat is a sports one but i dont know if many people replace them with originals so it could be lottery on a older high miler.