im a little fogged on this.. i know a miniramed engine likes more timing.. but how high is to high.. it is my understanding that it is to high if your over 36* total.. am i wrong?

it was always my understanding that in an $8d speed density car your total timng was calulated by adding your base.. lets say 10* btdc then adding your spark at a given rpm and map.. lets say 29.9* at 100kpa at 5500 rpms. that gives you a total of 39.9*

according to some good sources this is not correct. there is another factor that plays a role... intial spark advance. which i have set at 6*.. taking this #, how does it need to be factored in?
and when should you adjust this value?

is there some formula to calculate total timing? i really dont want to start adding timing before im sure how to do it correctly.

 

Total timing is:
Base timing + timing added by ECM.
Base is usually set to 6 degrees.

Ex.
Base 6* and 30* in chip is 36* Total timing
(as long as the initial timing in the chip is set to 6*)

If you turn the dist. so you have 10* and not recalibrate prom, you add 4 degress at all rpm's/MAP's..

If you look at the SA tables in 8D code it shows total timing. The amount of timing the ECM is adding is the SA table minus the initial timing set in the prom.


/N.


The correct way to add timing is in the prom.

 

got it... i will just put my base to 6* leave my intial spark at 6*. and then my spark tables will show actual timing.. and i will adjust there.

so if i do that and i have a value of 36* at 5500 at 100 kpa. that is acually the timing im giving the motor..

 

ok maybe i dont have it..

ex. base 10*, 30* in sa table. and initial at 6*.. total =34* ?

i see you said the amount of timing the ecm is adding is the sa table minus the initial timing set in the prom.

with you saying that if my sa valve is 30* and initial is 6* that is 24* the ecm is adding. then i add my base of 10* that is 34*total right?

 

That's the simply way but the post said calculate total timing so here's a simple run down;
Actual timing = base timing - initial timing + main SA table lookup + cts SA table lookup - cts SA table bias
Now there are other considerations that effect the timing. Things like startup, cranking, choke, idle correction, PE mode, highway mode, EGR, etc. It isn't very easy to come up with a difinative number and for this reason it's best to zero out some tables or make them less influential (scale all values down) and focus on one table at a time.
It takes years before you get to the point where you can sit down, and within a half hour have a good running starting bin for some obscure engine combo.

 

Clarification on your setting,
If your base timing is at 10, then your prom setting for "initial" should be 10.
The initial setting is there to accomodate your "base" setting mechanically.

 

they will offset each other. so you might as well set it at 6* and 6*..

unless you want to add global timing via the distributor..

 

Setting the initial value to match base timing is important for a few reasons, the most obvious is that now your "max SA" value will be the max engine SA, not max + base. I've noticed that the cars also seem to start and idle best when they're matched. It's all in the code somewhere... I just don't have the skillz to sift through it all.