[bhill86]

So I’ve been debating on picking up one of those progression ignition distributors for some time now and I’m leaning toward pulling the trigger this spring but I noticed one thing that I wanted to ask you about.

In addition to setting up what would effectively be mechanical advance, you can set and adjust vacuum advance. I downloaded the app and have played with what I can without a device (distributor) to link and what I noticed in the timing table is in the idle column, no vacuum advance appears to be applied. With a standard vacuum can hooked you manifold vacuum, vac advance would be applied at idle. Isn’t that preferred for additional cooling? One reason I ask is after adding A/C late last summer I started having idle cooling issues I didn’t have time to fully resolve before weather turned cooler and ultimately I’d like to take advantage of any cooling effect I can.

Now I COULD alter the timing to able to add advance in the idle column as vacuum increased which would be easy enough but I wanted others’ opinion.

I did email them inquiring about it and this was their response:

“The table generator creates a table in which in the idle timing value doesnt increase with more vacuum. Its much easier to tune idle this way. You could edit the idle column to increase idle timing with vacuum if you want but it would have little effect in real driving conditions. If you watch the bubble moving around the screen when the car is being driven, it very rarely (if ever) moves over the cells in the idle column that are above the idle position. As soon as you touch the throttle, the bubble moves to the right and up. Thats why these cells have vacuum advance and the idle column does not. Thanks“

[JLMounce]

That's pretty standard and what you also see in programming for FiTech, Sniper etc. It's not really called "vacuum advance" in modern terms. Timing is calculated by load expressed as MAP in kPa units. Higher kPa = more load. The less load the engine is seeing, the more timing it will typically want.

The Progression ignition calculates MAP based on engine vacuum. I've not used one personally, but know a couple people using them and it seems to work pretty well.

The only thing you do here is just add a higher value for your idle target. If your car likes 12 degrees mechanical at idle and you want 10 degrees from a vacuum can, set your idle target on your spark map to 22.

[Formulajones]

Just as Jason has said, simply add the amount of additional vacuum timing you want to the base idle table. Most start with an idle target of 20 degrees and work from there. 22 that Jason suggested is perfectly fine.

[bhill86]

Ok i I think I understand. I’ll post two tables I was playing with. The first being with no idle adjustment and the second having what I think you’re suggesting. Let me know if I’m on the right track or not. The idle column in this case is the 770 rpm.

[JLMounce]

Yup, you're on the right track now. You can actually ramp in extra timing beyond 3000 rpm as well. The machanisms involved that require a ramp in of timing from idle to 3000 rpm don't necessarily change from 3000 to 5500.

That said you don't typically ramp in that much though either. I'm currently ramping in a conservative degree of timing from 3000 to 5500 on my setup and it's really helped carry power out a little further. I'd prefer to do this on a dyno where I can measure power output and watch for any spikes or dips that may imply detonation.

What you've got there looks pretty good an in-line with what I would expect from an iron headed poncho.

[Formulajones]

I throw this out there...

What I like to do as far as ramping timing, is pull a degree or 2 right in the torque peak area, then ramp it back in. Torque peak is where the engine is most prone to detonate.
Then once above 5,000 rpm or so I might add an extra degree or two above where engine made best power on the dyno as things are happening faster at those rpms.

Doing this sometimes yields a pinch of HP, and sometimes by pulling a pinch of timing at the torque peak area it will actually produce better torque numbers in that area if the engine is sensitive to it.

At the same time on the fuel curve where I'm pulling timing at torque peak, I'll add a little bit of fuel in that area just to keep the engine safe.

It's really best to have the car on a chassis dyno for all this to see if it's helping.

[JLMounce]

Originally Posted by Formulajones

I throw this out there...

What I like to do as far as ramping timing, is pull a degree or 2 right in the torque peak area, then ramp it back in. Torque peak is where the engine is most prone to detonate.
Then once above 5,000 rpm or so I might add an extra degree or two above where engine made best power on the dyno as things are happening faster at those rpms.

Doing this sometimes yields a pinch of HP, and sometimes by pulling a pinch of timing at the torque peak area it will actually produce better torque numbers in that area if the engine is sensitive to it.

At the same time on the fuel curve where I'm pulling timing at torque peak, I'll add a little bit of fuel in that area just to keep the engine safe.

It's really best to have the car on a chassis dyno for all this to see if it's helping.

Yup, agreed. pretty much baseline SOP for a performance street tune.

[Formulajones]

Originally Posted by JLMounce

Yup, agreed. pretty much baseline SOP for a performance street tune.

That's really the sweet thing about EFI and timing control. For those of us that really enjoy tuning and squeaking out power, even from a mild street combo, these setups are hard to beat.

Can't do any of this with a carb and mechanical distributor.

Well,,,,,, you can kind of do this with a Holley carb if you want to get fancy with aftermarket metering blocks with adjustable emulsion channels but that's another discussion, and lots of trial and error.

[bhill86]

Thanks for the replies. I just wanted to make sure I was on the right track. I believe, if I understand correctly, the table with no timing ramp in the idle column would probably be similar to a mechanical/vacuum setup with vacuum plumbed to a ported source.

I just thought, #1 my car seems to have good quality idle with manifold vacuum to the can, and #2 I believe added vacuum advance at idle can also aid in cooling so I wanted to see if I could replicate that if I make the switch to PI since like I mentioned adding AC last year raised some idle cooling issues.

I don’t even really NEED one. I just wanted to see what difference it might make in a warmed over 400 which is just a cruiser plus it’s much easier than trying to locate and try different weight/center plate setups. I doubt I will be at the point of tuning to squeak out bits of power as you described for quite a while but I appreciate the suggestions. Ultimately, I hope I don’t regret spending the cash on one.

[JLMounce]

How much advance (mechanical + vacuum) are you currently seeing at idle?

I don't think the PI is going to necessarily solve your issue here unless your current distributor setup is incapable of providing about 20-24 degrees of idle advance. You're not going to see huge performance or efficiency increases if you've already got a well dialed system. Some with diligent tuning, yes, but maybe not worth the price.

[bhill86]

Sorry, I may not be explaining clearly. The cooling “issue” seems to be a result of adding AC but is kinda secondary to my question. The PI distributor isn’t meant to solve the cooling at idle with AC on issue. I have a few avenues to explore with correcting that but I ran out of hot weather last year before I attempted.

But because that existed last year I want to avoid working backwards so to speak by installing the PI and potentially creating another problem if there’s no “vacuum” advance at idle thus possibly reducing cooling at idle.

To answer your question though, I’m set at 14° initial with 10° vacuum advance at idle (if I remember right).

[JLMounce]

Okay that makes sense though. Id' stick a timing light on that thing at idle without unplugging the vacuum can and see how much lead it's actually getting. If you're not actually seeing much, you may need to adjust the vacuum can, or this is an area that the PI dizzy could help.

[bhill86]

Originally Posted by JLMounce

Okay that makes sense though. Id' stick a timing light on that thing at idle without unplugging the vacuum can and see how much lead it's actually getting. If you're not actually seeing much, you may need to adjust the vacuum can, or this is an area that the PI dizzy could help.

I double checked my phone where I usually jot down such things and in Nov I recorded that I’ve got 14° Initial with 13° vacuum at idle.

[JLMounce]

Yeah you're good then, more than enough idle advance.