Getting Started -- Timing map for ACN's Squish Pistons

[thedrew]

Steve, thanks for the info! -- where do you see your peak torque?

and also, how big are your ITB's?

[Steve Arndt]

I've played with a 5 gallon can of Sunoco GT+ 104 fuel. Can run tons more timing there, 4th gear at 1000 lugging no ping. I sort of drive around it when running crap fuel.

2800 to 3500 or so is where my strange combo is most prone to knock under heavy load. Under full load I can start adding advance back in after 3500 or so at a linear rate.

45mm ITBs (48 previously). Heads are small L5 mini ports.

[thedrew]

Hey Steve,

what do you have your cranking timing set to?

Thanks!

[Steve Arndt]

Cranking timing is -2 degrees (negative two degrees, 2 ATDC). My engine has so much compression you can barely turn it over by hand when adjusting the valves. I can't even bump start it in second gear, too much compression The late timing at cranking helps prevent kick back. The cranking timing is for 0 to 350 RPMs. It goes to my regular ignition tables above that.

Idle timing is 10 degrees when fully warmed up. I use timing based idle speed with -5 and +20 authority. Also the coolant and air temp maps come in to play too.


Hope that helps.

[thedrew]

That does help, thanks!

[thedrew]

just an update -- heres my current map that i'm rolling with right now.....

so much fun messin around with this -- I just wish I knew more

[Steve Arndt]

From 80 kpa and lower pressure, I would continue to ramp up the advance at the same rate you have, up to 32 to 36 or so at least, from where you level off at 3300. Keep it increasing. There is very little cylinder pressure there so it needs more advance. Basically the bottom right quadrant needs to keep ramping up.

[Steve Arndt]

Your 90 - 100 full load cells are a good starting point. Add some advance to the lower pressure cells.

[thedrew]

Thanks for the tips!

Can you post your map so I can see exactly how you ramp everything?

Thanks!

[Steve Arndt]

Yep, I promise to some day. Haven't touched my crashed bug for quite a while now.

[thedrew]

Steve et all, can you look over my AFR targets table?

all comments welcome!

Capture.JPG

[Piledriver]

You can probably lean burn with those pistons very well.

If you get much past stoich you add more timing to compensate, as the burn slows down either side of stoich.

On my map I'm at 19:1 target over 2600 RPM and under 90KPA.
(not running SS pistons even)

I have to get >23:1 AFR before I start to get into any lean surge or misfire, as long as it has sufficient timing.
This effectively headshots CHT at cruise by >50F, below 70F outside air temp it overcools, so I have a "conventional" AFR target/timing map I run in cold weather to help get it and keep it warmed up.

[thedrew]

Do you run thermostat flaps? I haven't had trouble with getting the engine up to temp, but I have thermostat flaps with a stock thermostat.

[Piledriver]

Yep, stock thermostat setup, but it can only do so much.

[Passatman]

Yep, stock thermostat setup, but it can only do so much.

What do you mean by this statement pile. I thought john recommendation was to run all engine tin including the thermostat with his pistons.