Academical : Advance timing on 2F ( 3F ) throughout rev range (1 Viewer)

[Yspen]

I have done a 2F-E build with aftermarket ECU

With this I have to set the timing throughout the rev range using two maps , the first map is basic rpm/timing advance and the second map is vacuum ( from MAP sensor ) / advance & retard .
So provision is made for load and rpm in the software .
What bothers me is that most cars run at about 25-30 degrees advance at High Cruiser to WOT . In my build the timing at High Cruise cannot be above 20 degrees - if I do accelerate out of High Cruise ( above 2500 rpm on Highway ) to car will ping badly if I go above 20 degrees . At WOT I have to keep it even lower at 17 degrees BTDC.

My question is re the stock 2F :
What is the stock advance timing of a 2F at WOT ?
Difficult question as the distributor uses weights and vacuum to advance the timing .
At Idle stock is 7 degrees but how far does the stock distributor advance the timing at 2500 rpm and high load ( vacuum advance ) ?

Idle = 7
Midrange light cruise = ?
Acceleration , mid range rpm , high load = ?
High Cruise ( Highway cruising, mid range load) = ?
WOT ( high rpm , high load ) = ?

If there is someone that has used Megasquirt to run a 2FE , your input can help a lot .
( I am beginning to wonder if I have not set up my distributor incorrectly making timing erratic . If though it corresonds with stock I will be happy )

 

[LAMBCRUSHER]

JimC has posted deetails regarding the mechanical advance curve, HAC, Vac advance and all in numbers at various engine speeds...Can't remember but think it is about 28-30 some degrees advanced all in at WOT. Seems wrong that you get pinging at 17* - 20* ...what is the static compression? IIRC you are running something similar to the Delta 859 grind on your cam

 

[Slow Left]

This information (see link below) doesn't answer your specific query (because it doesn't tell/measure the exact contribution that vac or mechanical advance plays at each RPM/Load for stock operating conditions...only the stock total available contribution of vac or mechanical advance), but I'll go ahead and post it up here because I am interested in this conversation.

23 degrees of centrifical advance
6 degrees of HAC advance
18 degrees VAC advance

http://www.globalsoftware-inc.com/coolerman/fj40/dizzyfaq.htm

The link appears to be a contribution by @Coolerman and @FJ40Jim

EDIT:
...and in this link, Jim C. & Co. from the 40 & 55 section helped orient my misconceptions on the topic...posts #6, 11 and 17 give expected conditions of vac advance at idle versus WOT, but still don't provide the data I think you are looking for:

https://forum.ih8mud.com/threads/2f-large-cap-dizzy-governor-springs.823545/

Post #6:
"The stock dissy will give 21-23* of mech advance at 4000RPM. Starting with idle timing of 10, the timing will be 31-33 when mech is all in.
Vac advance will be all in when the throttle is lightly opened (free revving the engine in the driveway)."

Post #11:
"Vac advance is zero at idle and zero under heavy load. Vac advance applies extra advance when the engine will tolerate it: at light load."

Post #17:
"ported vacuum is low / 0 at idle, rises at low throttle, then drops at WOT. This gives a smooth transition of rising advance until the mechanical advance catches up (at least as I understand it)."

 

[White Stripe]

The 2fe with its higher compression causes the pinging. What octane are you running? You should be running premium. I think with my tbi set up with stock compression on my 2f I am running around 50 degrees advance maximum. But stock compression is low on a 2f, like 7:1 or something.

 

[BC40]

maybe too lean? 17* total advance is not much...

 

[Yspen]

Thanks guys, this is valuable info .
I should reach 30degrees with the 2fe at 8,5:1 CR and mild Delta 250s cam at WOT.
Now that it is confirmed I can start looking for the cause of the pinging and not settle for it at 17 degrees.
Here in South Africa we only have one grade of fuel (95 Octane ) so it should not be that.
Not really lean - AFR 14,7 at cruise and then about 13,5 at WOT.

 

[Slow Left]

I should reach 30degrees with the 2fe at 8,5:1 CR and mild Delta 250s cam at WOT.

Yspen, I've got a couple of questions.

Is the dizzy on your 2FE the large cap, stock 2F dizzy?
If yes, does it have the stock governor springs and weights?
Is the governor stop pin bushing installed? - see link below
https://forum.ih8mud.com/threads/distributor-stop-pin-bushing-dimensions.784670/

If stock 2F dizzy with stock springs and weights and functioning mod for the deteriorated plastic stop pin bushing...and if the base timing is set to 10* BTDC, then according to the information above...@4000 RPM at WOT at Sea Level, then

Total Advance = 10* (Base Timing) + 21-23* (Mechanical Advance) + 0* (Vac Advance) + 0*(HAC Advance) = 31-33* Advance

...or so it seems to me...

 

[Yspen]

I fitted the 3FE dizzy . ( no weights or vacuum )
It could be that the wiring is incorrect that feeds the ECU from the dizzy . Leading edge vs trailing edge . That could mess up the timing.
At least I know now what the timing is supposed to be .

The timing at idle corresponds with the ecu ( what the ecu sees is the same as flywheel)
I need to get a adjustable timing light and see if the timing at 3000rpm also corresponds to what the ecu sees .

 

[Slow Left]

I fitted the 3FE dizzy

Oh...of course...that makes sense.