i was talking to bundy today and he brought up a valid point. 'were will i get my vacuum for the advance from when the turbo is hooked up'. its on a A series blow through setup.

turbo....advance

not on the same engine, usually have the dizy locked and regraphed

probably be a valid question if you are running a booster, but then it gets vaccum off boost anyway

so how do you lock and graph the dizzy

Basically lock the vacuum advance plate so it doesnt advance the timing with vacuum, only mecahnically advancing. Then you set a higher base timing and play with the mechanical advance slot, springs and weights to get the correct advance curve for your cam. Not a exercise to be undertaken without some knowledge of ignition systems.

What carby are u running? i got my turbo running through a 350 holley, my vacuum advance runs to the carby where it usually is. I'm currently modifying a n12 pulsar elec. dizzy to put on.

edit: mines a blow through turbo on a Worked A14

if you still want the vacum advance, you could try running an alternator that has a vacum pump in it. Some diesels alternators like this.

Quote:From the same place you normally get it. It works on part-throttle cruising. But don't you have to modify the advance housing to put carb input (boost) onto the back side?

Easier to simply not use a vacuum advance. It's mostly for fuel economy. You don't need it.

And he'll remember that when he's on the side of the road with an empty gas tank

With manifold vacuum, in an ideal world, you want advance, but on boost, you need RETARD to minimise or eliminate detonation. It's detonation that can destroy your engine to a degree second only to a train wreck.

Its gonna be interesting how many of these turbo A series will end up running with some of the unexperienced advice i always read being given.

The stock location on the carbie is the correct position to pick up a vacuum signal for the dissy - regardless of boxed carbie or boost referenced. During various engine opereating loads, if this position is not giving a vacuum signal - the dissy does not require it.

Now when it comes to ignition RETARD being required on boosted engines - This is bullcrap. Retarding the timing is a means of limiting boost, yes to prevent detonation. Wastegate preload tension is another way.
How does Retarding the timing reduce boost?
Well the less advanced the ignition timing is before TDC the less exhaust gas volume will be produced. Less exhaust gas volume = less exhaust gas flow through the turbine housing (exhaust side of turbo) This meaning less inlet air is compressed = reduced boost level preventing detonation.

Now if for what ever god unknown reason you can not control the detonation buy reducing boost by means of wastegate preload tension.
You regraph the dissy to limit its total mechanical advance, so then it can not advance to a degree point before TDC where detonation is developing. (Note : Ignition timing is still Advanced BTDC and is not Retarded ATDC)

From experience we (friends and I) years ago now, ran a number of blowthrough A series and one remained a stock points dissy and ignition timing was advanced to the point that it was hard for the engine to crank over to start. At times running boost levels higher than the 30psi guage could read. The engine ran on premium unleaded and it never showed audible sounds of detination during winter.

You can buy your aftermarket electronic boost retard modules if you like. Im sure you will get a hectik sticker in the packet.