Any timing experts out there that can explain some some timing paremeters

[Rickysnickers]

Originally Posted by 1970-CST

10” of manifold vacuum is pretty low. The 30-30 cam in my vintage vette made 10” and it needed A LOT of timing.

For discussion purposes, that engine (327/365hp 30-30 cam) idles at 1200 RPM, and setting base timing is near impossible, as the mechanical fly weights begin to add centrifugal advance around 700 rpm, lower then engine idles. So setting 10* initial timing was deceiving, as some of that was mechanical. In this case, I unhook the vacuum adv hose, and rev the engine until no more advance is added by the fly weights, in this case that was 2450 RPM. So at 2500 RPM I would move the dist. to set 38* advance.

If I set it at idle, I was leaving 6* of timing on the table, as the fly weights were contributing to the timing at idle. So setting 10* on the tab, was actually 4* base timing. When optimizing for performance, 6* is a HUGE amount.

What is your Idle RPM?

Timing is everything, and all the tuning and widgets to make HP are worthless unless you can optimize the timing map for your particular setup.

One needs to remember that “ported” vac adv, and low initial timing was a bandaid to get the engine across the emissions finish line. It was FAR from optimum.

Here is the engine I am running, https://blueprintengines.com/product...lock-bp4002ct1 . I have the ECU set to idle at around 850 rpm. As per the Edelbrock instructions, the initial timing is set at 12 degrees. This is set for the firing of the injectors and that they are firing correctly. The distributor included with the fuel injection is all electronic. There are no vacuum lines to it at all. The timing and vacuum advance is done through a tablet.

[Rich72C10]

I know we gotten straight on the MAP sensor, vacuum and pressure stuff. Yesterday during our confusion I had emailed Progression Ignition and I thought I'd share his reply. Since it is nice to have someone actually take the time to respond with details.

Originally Posted by Theodore@Progression Ignition

The first thing to know is what the units mean. Kilopascals kPa is a unit of PRESSURE. The sensor we use is an absolute pressure sensor. It will tell you the ACTUAL pressure in the intake manifold. Vacuum is not an absolute measurement. Vacuum tells you the DIFFERENCE between the pressure outside the intake (atmosphere) and the pressure inside the intake. This is the most common misunderstanding. As an engine tuner you want to know the actual pressure as this is what determines how long it takes for the fuel to burn. Also, vacuum readings DO NOT compensate for changes in altitude. The timing table in the app is set up so that high pressure is at the TOP of the screen. At wide open throttle, there is no restriction to the air coming into the intake manifold. Therefore, you will see atmospheric pressure at WOT. At sea level, atmospheric pressure is approximately 101 kPa. This is why the top row is 101 kPA. A naturally aspirated engine won't go higher than this. The bottom of the timing table is 20 kPa which is low pressure (high vacuum). You will only reach this level when the throttle blades are closed and RPM is high during deceleration. As manifold pressure DECREASES from WOT (top row), the fuel needs more time to burn because the fuel/air molecules are becoming further apart from one another. This is why more timing advance is needed at low pressures. You are starting the burn sooner to allow the fuel to burn completely before the crank descends too far down the cylinder.
So as far as the app settings are concerned, here is what they mean. Using the standard settings of 8, 80, 20. Max vacuum advance- this is the max number of degrees that will be added at the max vacuum point of 20 kPa. Start vacuum advance at- this is the pressure level at which degrees will begin to gradually be added. This is just under WOT which is good for street drive cars. Remember low kPa=high vacuum.

[1970-CST]

Originally Posted by Rickysnickers

Here is the engine I am running, https://blueprintengines.com/product...lock-bp4002ct1 . I have the ECU set to idle at around 850 rpm. As per the Edelbrock instructions, the initial timing is set at 12 degrees. This is set for the firing of the injectors and that they are firing correctly. The distributor included with the fuel injection is all electronic. There are no vacuum lines to it at all. The timing and vacuum advance is done through a tablet.

From the specs of the engine it says 32-34 at 3500 rpm. That’s a pretty lazy timing curve, but that is where I would start, as it is what the engine mfg recommends.

The tabled has the ability to do you want.

12 initial plus the 15* in the vac advance setting. Will give you 27* of idle timing

If it pings or knocks when you punch it, you can back the initial to 10, or 8 and add 2-4 to the vac adv setting to make it 17-19. You want no less then 20* TOTAL idle timing. I would shoot for 24-28.

[Rickysnickers]

Ok, thanks!