Idle Vcuum in-Hg

[joelittel]

I'm trying to generate an initial spark table and I need to know my idle vacuum in-Hg.

How do I go about finding this number?

[Blown88GT]

[nathaninwa]

Every combo is different. You'll have to get the car running to see what hot idle vacuum is

[joelittel]

Is it as easy as hooking a gauge up to a vacuum port on my plenum?

[billr]

Why not just read the MAP value and do the simple conversion? No extra gauge needed.

[slow_hemi6]

Or you could use the gauge that comes in tuner studio. I have it on one of my TS dashboards. Sensor inputs 1 > Vac/Boost

[billr]

After re-reading, I think the OP wants to measure the idle vac as it exists before the MS install. Yeah, a simple mechanical vac gauge will do it...

[joelittel]

I'd like to make sure my spark table is as close as it can be until I can get the car on a dyno and I thought this link would be a good start.

http://www.useasydocs.com/theory/spktable.htm

I just wasn't sure what value to use for the Idle Vacuum. The car runs pretty well as it is so I might just take the MAP value and conversion route.

[slow_hemi6]

You can put the Vac boost gauge right next to a Map gauge on a tuner studio dashboard, make direct comparison. I would not bother, just open up the spark table with the engine running, the blue dot will show you what cell it is using.
This is fairly typical SD table usage from idle. Orange WOT, Blue heavy, Purple mid, Green mild, Yellow cruise, Grey decel, moves Top to bottom.

VE Table.jpg

[dontz125]

That is absolutely fascinating - and it certainly illustrates why ITB mode was made!