Hi guys,

I need some help tuning my HS6 1 3/4" draw through turbo setup. I have read so much general info but I can find any real answers. "just file the needle" tends to be the general comment

Im chasing the following:

1) Does the standard a series mech pump supply adequate flow for this setup? I know pressure is ok but will it refill the fuel bowl fast enough

2) what dash pot oil is recommended? I understand/believe heavier oil richens the mixture. I have proper SU oil 20w is that recommended?

3) what colour dash pot spring?

4) what needle profile code have people used as a start point then refined?

5) Did you use standard size main jet? And do you/did you adjust AFRs with the nut underside or set the main jet at the old school recommended 2 turns out then refine the needle profile?

Thanks in advance. These questions will help other draw through turbo guys. If I get this running right I will post a proper full log of the exact items and settings I used to help others if they are going down this path. There are so many things that arent mentioned in detail when doing the draw through a series turbo that would have helped me heaps if I had known at the start. :)

Quote:The standard A-series fuel pump flows twice what is needed for factory HP. So unless your turbo will make over 120 crank HP then your good to go

Factory Spec
* 1970-1972 A12 pump: 450ml/minute minimum
* 1979-1982 A14/A15 pump: 1300ml/minute minimum

Interesting question here. This I can give you some guidance on.
Some years ago I had a supercharged A14 with an 1 3/4" SU ( drawthrough) setup.
Originally this was in a rally car that had a big 2" ( or bigger? ) Jag SU on it but this carb was worn out so was biffed.
I engaged the services of a chap to tune it and after a number of hours of needle fiddling was told that it was tuned.
I drove it and while it ran okay it really felt quite flat.
Now here is the interesting bit-for reasons that I shall not bother explaining I took it for a drive and pulled out the choke which drops the jet and enrichens the whole mixture up-WHAT a difference!!
I took it back to the chap who 'tuned' it and he simply could not believe it.
He set to and essentially removed the bottom half of the needle and problem solved!
What profile he started with I cannot tell you but I would probably start with a standard one and machine the bottom 40% off it then try the choke trick and see how you go.
Cheers
Dave

Thanks DD great numbers I can quote to tuners/queries regarding fuel supply

Thanks for info Dave. I understand exactly what you are saying, I have played with the jet screw heaps trying to tune it.

General info I have been told is that you shouldn't be able to start the car without the choke on. If you can its set too rich for idle.

What you said re needle is exactly what I was expecting to have to do. The issue I have is the other variables that need to be fixed before you start to custom change the needle profile.

To be honest I think its beyond me. I have found a reputable tuner and have booked it in with him. I will let everyone know the results.

Once its running well I will note all the variables exactly and measure the needle profile with a vernier at the 16 spots so others can have a closer start point than me.

To be honest the entire turbo process has been so much more complex and involved than many people eluded to on the forums when I was first asking years ago.

To anyone considering this IMO if you have gone this far do it properly with EFI

I have updates but will post into my old original thread to help others:
http://datsun1200.com/modules/newbb/v ... id=482740#forumpost482740

long story short the needle you want or that will at least get you closest is a BCA profile

the rest of the info will be in my other thread