A15 turbo help

[CSP]

Im looking at building a draw through turbo a15 for my ute.

-2 inch SU carb
-t25 turbo(carbon sealed)
-warmish cam
-slight port and polish
-custom inlet/exhaust manifolds

What I am wondering is what do I have to do with my timing setup so it wont kill itself. Do I need a re-curved dizzy?

also, I am looking at lowering the comp so it is more boost friendly. I have heard that you can machine out the "bowl" from the stock a15 piston to leave it dished. is this a feasable idea or will 12+ psi see me killing pistons every weekend.

Any more ideas from people would be much appreciated as I know a few of you(*cough* Bart *cough*) have been down the forced induction route before.

Cheers, Dave

[Bartman]

It does pay to limit your total advance. There are a few ways of doing this. One means is to dismantle your distributer, and build up the ends of the slots which the centrifugal weights move through. (when you get it apart, you'll see what I mean) Here's a nifty secret to check how much mechanical advance you have. Go to a stationary shop and buy one of the those 360' degree protractors. Rivet it to an old rotor button. Then hold the lower end of your dizzy shaft in the vice. As you twist the protractor you'll be able to see how far it's advancing. I don't know how much total advance is ideal for a forced motor, but someone like palmside will have an idea about that. The other way, Probably better is to take your vac advance diaphram to Quality rebuilds in fenhall st russley. And get Barry Emmes to dismantle your diaphram and reassmble it so that the spring is pushing it to full advance at rest, and when the motor comes on boost it pushes the diaphram arm to retard the timing. You'll need to retime your static accordingly of coarse. The new diaphram method is better (I think) because it still allows you to have full advance when you're off boost. IE at cruise throttle on the open road etc.
Increasing your chamber volume is probably the better way of dropping the CR too. With a happy tune, you should be able to run decent boost. A bit of crudeamentry water injection will help limit detonation too.

[nick_m]

The other (read:cheap) way i have heard people doing it is just to lock the dizzy, I.E. no advance and just set your static timing to whatever gives you the most horsepower without detonation.

[_Jake]

I havnt got mine running yet, but im running an electronic dizzy off an e15 engine. A few mods needed but should do the trick. Im going to get it professionally tuned and possibly look at water or methanol injection... but yeh ill let you know how it turns out

[Bartman]

Locking the dizzy is the lazy way. I've read this absolutely kills your off boost performance though.