pierburg conversion

[michael tierney]

just got 38mpg on my first tank(37litres)of petrol,thats an extra 60kms per tank!! i was origionally tuning this carb because of the extra barrell and power but this has come as a complete bonus.i just kept the vacuum guage bellow the atmospheric mark for most of the time and i'll probably do another tank before i decide to rolling road it.the sizes are as follows
primary venturi;20
main/air corr.;97/130
idle;37 with 80 a/c
acc pump;35

[Scoff]

hi michael, how big is the 2nd choke ? and what size needle jet do they have generally ?

[michael tierney]

the second barrell is 30mm ,the venturi is 24 and i think the needle jet is 2mm!!needle jet seems ample and because of the small venturis torque should be good.when u take the top of these carbs off u find the same fine sealing ridge that the 32 DIS has and they seem to be made of alluminium instead of the zinc alloy stuff!!
When the primary venturi is that small u go-on to main jet very quickly which is good for drivability and the fact that the primary throttle is so small makes the progression airspeed more efficient!

[BlueFish5Gt]

Could I have more information about this because I've never heard of it before but it sounds interesting.

[michael tierney]

i hope to do a write-up on the project when i'm finished tuning it ,if its excellent and worth doing i'll do a step by step but at the mo time is tight!!theres a couple of pics in my folder!

[Scoff]

If you do a write up with pics michael I'll add it as an article to this site - the new articles section will be working soon. thats a 30-odd % increase in choke cross-section, they might work quite well on big power c1j's, escpecially if they cope with a 2.2mm needle or more! (sometimes even 2mm gets a bit small at 200+hp)

[raj]

what cars can you source this pierburg carb from..?

[michael tierney]

the 28/30 pierburg is from an astra and i also have a 24/28 from a polo.I have a haynes manual but even though it gives the car models and venturi sizes it does'nt give the throttle sizes!!the ideal manifold is a water heated GTL one but i'm going to modify a turbo one and see how it works!