Why would you time a spark ATDC?

[Pupp]

Just playing with the Emerald software and notice the range on the Ign map table allows -30 deg to +60 deg BTDC, anything 'less' than 0 being effectively after TDC... wondering why this range has been allowed as I always thought varying degrees of advance was the game?

What purpose might a tuner have for wanting to fire a plug, say, 20 degrees after the piston is at top dead centre? Guess traction control might be able to use a softened power stroke but any other uses come to mind? Maybe a means of modifying exhaust gas temps if the spark is retarded to the point of the valve opening on overun??

[Slinky]

Other than anti-lag/forced spool, I've no idea..

[BB-Q]

If you want to do anti lag (something I will experiment with in Megasquirt when the time comes) you need timing at about 20deg past TDC to get ignition going within the exhaust manifold/turbo. This is what gets the turbo spinning at launch rpms. Fks yer turbo though, apparently. Guess I'll find that one out.

[Vixpy1]

BB-Q said:

If you want to do anti lag (something I will experiment with in Megasquirt when the time comes) you need timing at about 20deg past TDC to get ignition going within the exhaust manifold/turbo. This is what gets the turbo spinning at launch rpms. Fks yer turbo though, apparently. Guess I'll find that one out.

Its bloody good fun though

[Rocket Pepper]

Don't some 911 turbos fire ATDC?

[Slinky]

BB-Q said:

If you want to do anti lag (something I will experiment with in Megasquirt when the time comes) you need timing at about 20deg past TDC to get ignition going within the exhaust manifold/turbo. This is what gets the turbo spinning at launch rpms. Fks yer turbo though, apparently. Guess I'll find that one out.

will that be an Auto or Manual box?

And yes, it does fook the turbo with MASSIVE rapid temperature increases..

[Pupp]

Slinky said:

BB-Q said:

If you want to do anti lag (something I will experiment with in Megasquirt when the time comes) you need timing at about 20deg past TDC to get ignition going within the exhaust manifold/turbo. This is what gets the turbo spinning at launch rpms. Fks yer turbo though, apparently. Guess I'll find that one out.

will that be an Auto or Manual box?

And yes, it does fook the turbo with MASSIVE rapid temperature increases..

Would imagine it can't be especially beneficial to the exhaust valve sealing faces either? That's assuming the delayed spark is the ign source, or is the 'theory' actually to actually allow the charge to self-ignite in the hot exhaust after passing through the combustion chamber before it sees a spark from the plug?

[BB-Q]

Slinky said:

BB-Q said:

If you want to do anti lag (something I will experiment with in Megasquirt when the time comes) you need timing at about 20deg past TDC to get ignition going within the exhaust manifold/turbo. This is what gets the turbo spinning at launch rpms. Fks yer turbo though, apparently. Guess I'll find that one out.

will that be an Auto or Manual box?

And yes, it does fook the turbo with MASSIVE rapid temperature increases..

that'd be on a Holset HX35 or 40 with a T5 gearbox. I was thinking of using a clutch switch as a master and a steering wheel switch as a slave. I'm concerned about turbo temperatures so hope to get it effective enough that I only need use it on the startline for a couple of seconds, coupled with a rev limit of wherever the engine produces maximum torque (I.E. a seperate msq activated by the switches).

Megasquirt is capable of all this and more, despite many rolling road operatives not liking it. It's the ECU of choice for those of us with a budget tighter than a wax dog's chuff!