13 replies to this topic

[minivanman8]

I have 1293 with eaton M45 and SW5 cam (Vmax)

59D dizzy, with magnetic pickup and accuspark stealth black box for advance curve.

Can someone recommend some figures for the advance curve and a procedure for setting timing?

I assume idle timing is done without vacuum and full advance timing is with vacuum attached?

Stuart mentioned 12 idle and 27 full advance, but with 12 idle without vacuum I currently get nearly 50 degrees full advance with vacuum attached!

[HUBBA.HUBBA]

Ditch the vacuum dizzy. Can you map the stealth box thingy? You really need to have full control of your curve, quite high at low revs and low (24degees ish) at high revs

Edited by HUBBA.HUBBA, 15 May 2016 - 05:40 PM.

[minivanman8]

Ok. Yes, it has advance curve, dwell angle and rev limiter programmable.

Only trouble is I have no idea what advance curve or dwell angle should look like!

[HUBBA.HUBBA]

Ok. Yes, it has advance curve, dwell angle and rev limiter programmable.
Only trouble is I have no idea what advance curve or dwell angle should look like!

If its programmable then lock the dizzy.
Can have a look at what mine was if you like. When I first had my amethyst I was running 1293 with m45 and the same cam

[HUBBA.HUBBA]

Don't know if this any good to you.

[minivanman8]

Fantastic, thanks.

Dizzy is already locked out (bought as a locked out dizzy)

Guess I just need to set the physical timing to 10 degrees at 1000rpm and make sure there's 22 degrees at 4000?

[HUBBA.HUBBA]

I don't understand, if your dizzymis locked then why is it advancing on vacuum.
Yes those are rough settings that are safe, but you will need to experiment as all engines are different. Yes I had it at 22 degrees at 4000 but I have the rev limiter at 5000.

[minivanman8]

Mechanical advance is locked. Currently vac unit is not connected to carb.

[mini13]

okay, few points here,

 

at idle you want to be seeing in the order of 15 to 20 degrees with the vac attached, your likly to be in the right area if you time it up at 12 deg with the vac detached as stu says.

 

full advance will be at full throttle so there will be no vacum, obviously this varies engine to engine but i would expect that about 22-24 deg would be more like what you need on a blown engine, this is taken care of by the centrifugal advance...

 

vac advance is only active during idle and part throttle... mainly part throttle, its there to advance so the engine runs better at part thottle, i would expect somthiong in the order of 35-40 degrees of advance at uising speed.

 

one thing I have seen is dizzys welded up and timed at about 18 degrees on forced induction motors, ok for idle and ok for very high boost, and then fitted with a vac advance to make them drive ok.

[HUBBA.HUBBA]

okay, few points here,

 

at idle you want to be seeing in the order of 15 to 20 degrees with the vac attached, your likly to be in the right area if you time it up at 12 deg with the vac detached as stu says.

 

full advance will be at full throttle so there will be no vacum, obviously this varies engine to engine but i would expect that about 22-24 deg would be more like what you need on a blown engine, this is taken care of by the centrifugal advance...

 

vac advance is only active during idle and part throttle... mainly part throttle, its there to advance so the engine runs better at part thottle, i would expect somthiong in the order of 35-40 degrees of advance at uising speed.

 

one thing I have seen is dizzys welded up and timed at about 18 degrees on forced induction motors, ok for idle and ok for very high boost, and then fitted with a vac advance to make them drive ok.

 

Why would a welded up dizzy need a vacuum advance? Surely when it is welded its not going to move. Even very strong springs stop it advancing. I had the same issue when I first had a super charger , I was first advised to have a vacuum advance (can't remember the range). No matter what I tried it would always advance too much.

IMO the only way to do it is a properly locked dizzy, electronic ing and programmable curve.

 

I am suprised at the 40 degrees at cruse.

[minivanman8]

So if I disconnect the vacuum pipe and plug it and have the lock on centrifugal advance and set advance curve as discussed above, that should be ok? I'll have a play when I put engine back in (new primary gear bush needed at the minute so the engines in the shed!)

[Ethel]

Think of the dizzy as a record turntable. The centrifugal advance would move the needle to fast forward the track. The vac advance would be equivalent to moving the record on the turntable like a 90's DJ.

[mini13]

 

okay, few points here,

 

at idle you want to be seeing in the order of 15 to 20 degrees with the vac attached, your likly to be in the right area if you time it up at 12 deg with the vac detached as stu says.

 

full advance will be at full throttle so there will be no vacum, obviously this varies engine to engine but i would expect that about 22-24 deg would be more like what you need on a blown engine, this is taken care of by the centrifugal advance...

 

vac advance is only active during idle and part throttle... mainly part throttle, its there to advance so the engine runs better at part thottle, i would expect somthiong in the order of 35-40 degrees of advance at uising speed.

 

one thing I have seen is dizzys welded up and timed at about 18 degrees on forced induction motors, ok for idle and ok for very high boost, and then fitted with a vac advance to make them drive ok.

 

Why would a welded up dizzy need a vacuum advance? Surely when it is welded its not going to move. Even very strong springs stop it advancing. I had the same issue when I first had a super charger , I was first advised to have a vacuum advance (can't remember the range). No matter what I tried it would always advance too much.

IMO the only way to do it is a properly locked dizzy, electronic ing and programmable curve.

 

I am suprised at the 40 degrees at cruse.

 

because you can either weld up just the centrifugal advance, or the vac advance... or both,

 

the centrifugal is in the bottom so you would have to fix the top and bottom shafts together, the vac just moves the base plate.

 

easiest thing to do is look at a 3d map from an ecu, attached is mine, its actually running 30ish degrees at cruise, but would see 40 degrees on overun so I was a bit off there.

 

 ign.jpg   79.05K   16 downloads

[HUBBA.HUBBA]

Mechanical advance is locked. Currently vac unit is not connected to carb.

That'll do