Posts: 2,103
	Threads: 122
	Joined: Jan 2013
	
Reputation: 
9
Location: south west, devon
Car Model/Spec: Kingfisher Ph1 Dturbo S
Thanks: 1
	Given 7 thank(s) in 7 post(s)
	 
	
	
		So I got rid of my black DT and bought a moonstone hdi, just wondering whats best for a stage 1 map.
Decat standard centre pipe and straight pipe at rear
Decat. De centrebox and a nice back box
Or just full straight through? 
Just looking for something that sounds decent and will compliment a stage 1 map well
Cheers
	
	
	
	
		
	
 
 
	
	
	
		
	Posts: 15,646
	Threads: 541
	Joined: Dec 2011
	
Reputation: 
124
Location: Aylesbury
Car Model/Spec: 320bhp Impreza WRX
Thanks: 7
	Given 59 thank(s) in 58 post(s)
	 
	
	
		2.25-2.5" bore, no cat, no mid box and a straight through back box  of whatever size you want depending on the noise your looking for.
	
	
	
	
		
	
 
 
	
	
	
		
	Posts: 10,864
	Threads: 117
	Joined: Dec 2011
	
Reputation: 
119
Location: Southampton
Car Model/Spec: 306 HDi and friends
Thanks: 13
	Given 106 thank(s) in 106 post(s)
	 
	
	
		2.25 is standard, yeah. You'll probably find your current one is a pattern part though, usually around the 2" mark, maybe a little bigger.
	
	
	
	
		
	
 
 
	
	
	
		
	Posts: 15,646
	Threads: 541
	Joined: Dec 2011
	
Reputation: 
124
Location: Aylesbury
Car Model/Spec: 320bhp Impreza WRX
Thanks: 7
	Given 59 thank(s) in 58 post(s)
	 
	
	
		Yeah standard is 2.25" but tends to be a little less at certain points unless you have a pattern system where the ID in places could be well under 2"
Even 2.25" with proper mandrel bends would see gains.
	
	
	
	
		
	
 
 
	
	
	
		
	Posts: 6,482
	Threads: 226
	Joined: Dec 2011
	
Reputation: 
24
Location: Cornwall
Car Model/Spec: A3 TDi 
Thanks: 0
	Given 0 thank(s) in 0 post(s)
	 
	
	
		Isnt it just the stock downpipe thats 2.25 and the rest is slightly smaller anyway?
	
	
	
Doesnt even own a 306.
	
		
	
 
 
	
	
	
		
	Posts: 149
	Threads: 11
	Joined: Aug 2013
	
Reputation: 
1
Location: Durham (ish)
Car Model/Spec: Ph3 Meridian HDI
Thanks: 0
	Given 0 thank(s) in 0 post(s)
	 
	
	
		Iirc when I took the cat off mine I needed a reducer from 2.25 down to 2"