Chimaera dizzy
Discussion
Hi,
your dizzy should have 16 degrees of mechanical advance.
If you have a good digital timing light you will be able to confirm this.
To achieve 28 degrees at 4000 rpm (typical setting for TVR rover V8 5.0 L) set the idle static timing at 12 degrees.
If you are only getting 14 degrees mechanical advance then you probably need to strip the dizzy and fix.
I've just overhauled mine and the mechanical advance base plate was stamped with an 8, confirming the 16 degrees mechanical advance (crankshaft degrees).
your dizzy should have 16 degrees of mechanical advance.
If you have a good digital timing light you will be able to confirm this.
To achieve 28 degrees at 4000 rpm (typical setting for TVR rover V8 5.0 L) set the idle static timing at 12 degrees.
If you are only getting 14 degrees mechanical advance then you probably need to strip the dizzy and fix.
I've just overhauled mine and the mechanical advance base plate was stamped with an 8, confirming the 16 degrees mechanical advance (crankshaft degrees).
Ive only measured 16' of mechanical advance on the crank on mine, so I assume one weight was jammed.I can understand that 16' worth of weights in the dizzy will give 32' work of crank advance as the dizzy runs at half speed- but its just to make sure wires are not getting crossed here?
Aussie John,
the springs looked identical, same length, colour and wire thickness. I pulled against both and they felt the same tension. I was surprised they were the same. The weights were identical also, same shape and thickness with a 1 stamped on them. The dizzy is from a late 94 Griffith 500, the dizzy build date sticker is of the same year, so no reason to think it is not the original. I don't know how this compares to those fitted to Land Rovers of the same year.
Ozstyle
the springs looked identical, same length, colour and wire thickness. I pulled against both and they felt the same tension. I was surprised they were the same. The weights were identical also, same shape and thickness with a 1 stamped on them. The dizzy is from a late 94 Griffith 500, the dizzy build date sticker is of the same year, so no reason to think it is not the original. I don't know how this compares to those fitted to Land Rovers of the same year.
Ozstyle
Hi Mark, I've only pulled two Rangerover dizzies to bits and both measured 22 degrees of advance but on looking at the base-plates they were marked 10.5 so 21 degrees. The thing was one had identical springs [both fairly weak] but the other had one similar and one very strong so I guess a different advance curve.
Blitz,
the dizzy does not work as you describe. If you ever strip one you will see. The weights and rotor shaft base are interlocked in a cam type arrangement.
If one weight is frozen solid (at rest position) there will be no mechanical advance even if the other weight is free. There is a physical stop on both sides of the base plate arrangement which only allows 8 degrees advance (16 degrees crankshaft). To get more mechanical advance you would need a dizzy with a different base plate as Aussie John mentioned.
If you are looking for max mechanical timing of 32 degrees BTDC, then the static timing at idle would be 16 degrees (if using a dizzy with 16 degrees of mechanical advance). It would appear other dizzys offering 22 degrees of mechanical advance would allow a more reasonable static idle timing figure of 10 degrees BTDC. Hope this all makes sense.
Ozstyle
the dizzy does not work as you describe. If you ever strip one you will see. The weights and rotor shaft base are interlocked in a cam type arrangement.
If one weight is frozen solid (at rest position) there will be no mechanical advance even if the other weight is free. There is a physical stop on both sides of the base plate arrangement which only allows 8 degrees advance (16 degrees crankshaft). To get more mechanical advance you would need a dizzy with a different base plate as Aussie John mentioned.
If you are looking for max mechanical timing of 32 degrees BTDC, then the static timing at idle would be 16 degrees (if using a dizzy with 16 degrees of mechanical advance). It would appear other dizzys offering 22 degrees of mechanical advance would allow a more reasonable static idle timing figure of 10 degrees BTDC. Hope this all makes sense.
Ozstyle
Its just safety margins-slightly retarded timing will allow for all engine conditions, loads and fuel octane, so by pushing it to its max you potentially do some piston damage by causing detonation if say the cylinder head had more carbon, so the compression was raised a bit. I recently read that the absolute maximum for this engine is 38', but Im certainly not going there.
Ozstyle said:
Blitz,
the dizzy does not work as you describe. If you ever strip one you will see. The weights and rotor shaft base are interlocked in a cam type arrangement.
If one weight is frozen solid (at rest position) there will be no mechanical advance even if the other weight is free. There is a physical stop on both sides of the base plate arrangement which only allows 8 degrees advance (16 degrees crankshaft). To get more mechanical advance you would need a dizzy with a different base plate as Aussie John mentioned.
If you are looking for max mechanical timing of 32 degrees BTDC, then the static timing at idle would be 16 degrees (if using a dizzy with 16 degrees of mechanical advance). It would appear other dizzys offering 22 degrees of mechanical advance would allow a more reasonable static idle timing figure of 10 degrees BTDC. Hope this all makes sense.
Ozstyle
Are- I had not gone into such detail!- Anyway the weights, springs, and Vacuum unit are in in the bin now, and its all locked solid, as Ive got the Aldon Amethyst mappable systm to work at last, so that fully mappable 14CUX and ignition at a fraction of the cost of going after market the dizzy does not work as you describe. If you ever strip one you will see. The weights and rotor shaft base are interlocked in a cam type arrangement.
If one weight is frozen solid (at rest position) there will be no mechanical advance even if the other weight is free. There is a physical stop on both sides of the base plate arrangement which only allows 8 degrees advance (16 degrees crankshaft). To get more mechanical advance you would need a dizzy with a different base plate as Aussie John mentioned.
If you are looking for max mechanical timing of 32 degrees BTDC, then the static timing at idle would be 16 degrees (if using a dizzy with 16 degrees of mechanical advance). It would appear other dizzys offering 22 degrees of mechanical advance would allow a more reasonable static idle timing figure of 10 degrees BTDC. Hope this all makes sense.
Ozstyle
- As a matter of interest the somewhat retarded idle ignition timing and ported vacuum take off are an emissions thing- apparently running the timing late makes the exhaust temp run hotter, so the exhaust is cleaner, so by blocking the vacuum off you can remove the vacuum advance at idle.Gassing Station | Chimaera | Top of Page | What's New | My Stuff