[73ta]

I've got one coming in a week. Can't wait to get it installed and running on my 462. Currently running an MSD pro billet with no vacuum advance. Hoping to pickup some more power, driveability & MPG.

[Verdoro 68]

Originally Posted by ta man

I forgot the OP is using manifold vacuum, so it doesn't matter. I run ported vacuum advance so my idle timing needs a little help when it is cold.

I believe the instructions say to run full manifold vacuum with the Progression Distributor. Are you running yours with ported vacuum?

[ta man]

Originally Posted by Verdoro 68

I believe the instructions say to run full manifold vacuum with the Progression Distributor. Are you running yours with ported vacuum?

Currently until I add another source for manifold vacuum. My engine always liked ported vacuum..but with this distributor I know I can dial back the vacuum advance to make it happy at idle.

[73ta]

Originally Posted by lovedemnewfies

So I called progression ignition and their answer was that the tach was off and that the grey wire off the dizzy wouldn’t have enough power to run the factory tach. So I guess I need to have the tach refurbished to have the “guts” installed to make it work.

I talked to a guy that fixes taches and guages on second gen TA's. He said that the tolerance of those old tachs is =/- 10%. Mine is ok at idle but off about 500 RPM in the 2000-3500 and above range. He said he can calibrate them to be close at the top or at the bottom of the scale but not both.

[73ta]

Update, I replaced the tach circuit board with a new improved one. Tach is much closer now.

[68 Firebird]

Got one of the new PI HEI units for Christmas.
Got it installed and been tweaking timing table.
Any pointers on timing tables. Car is nice and
Responsive and interesting to see timing/vacuum while
Driving.

[Squidward]

I run FiTech with timing control, so it is a similar dealio, but the PI has more resolution. All I get to play with is idle/1100/3000/6000 and 2 different vacuum conditions (WOT and cruise).

I like a lot of base timing, and I use 28 at idle conditions. I'd be curious if your engine combo would like a simulated "manifold" vacuum advance condition. Right now it simulates a "ported" advance.

I see your "mechanical" is all-in by 3000. I usually liked that a little earlier on my engine when I ran a standard HEI. My normal around town cruise rpm is 2500-2600, so I like to have cruise timing in at that point - 42 degrees max for me. But my rpm breakpoint is 3000 rpm, so I have to do a little blending to get more high vacuum cruise timing. If I had more granularity in my system, I would go for more cruise timing like you have, somewhere close to 50.

I would be curious how your setup would respond by pulling in your wot timing from 3000 to 2500.

Isn't this fun? You can play around without spring changes or vacuum advance cams and tension screws!

[nytrainer]

What does the Y axis represent (20 - 101). Sorry if it’s obvious but I’m scratching my head on that.

[73ta]

MAP sensor.

[JLMounce]

Originally Posted by Squidward

I run FiTech with timing control, so it is a similar dealio, but the PI has more resolution. All I get to play with is idle/1100/3000/6000 and 2 different vacuum conditions (WOT and cruise).

I like a lot of base timing, and I use 28 at idle conditions. I'd be curious if your engine combo would like a simulated "manifold" vacuum advance condition. Right now it simulates a "ported" advance.

I see your "mechanical" is all-in by 3000. I usually liked that a little earlier on my engine when I ran a standard HEI. My normal around town cruise rpm is 2500-2600, so I like to have cruise timing in at that point - 42 degrees max for me. But my rpm breakpoint is 3000 rpm, so I have to do a little blending to get more high vacuum cruise timing. If I had more granularity in my system, I would go for more cruise timing like you have, somewhere close to 50.

I would be curious how your setup would respond by pulling in your wot timing from 3000 to 2500.

Isn't this fun? You can play around without spring changes or vacuum advance cams and tension screws!

That's all that the handheld lets you access Get your ProCal software running and you can control the cells between that are interpolated.

The PI distributor software is still has more resolution than the FiTech tables, but not nearly as much as the handheld imputs would have you believe.

From the table provided above, it looks like a good safe starting point. You may find it wants a bit more timing up top, for the timing to come in a bit sooner and it may tolerate more low load timing.

[68 Firebird]

Thanks for the feedback. Yes I wanted a safe curve as a baseline that was similar
to the curve in my HEI. My car likes a slower curve and dead stable timing in gear.
very minimal drop in RPM as the unit adjusts timing to load when dropped in gear.

still learning with this new toy, and had one long cruise last weekend. Saw that while
running down highway at 65-70, map sensor has me in 42 line of table. fun to observe vacuum and timing live on display. definitely more tuning needed.

Gerry

[chiphead]

I've got a PI distributor in my car. To make it easier on my brain, I tweaked the Y axis so KPA easily corresponds with vacuum. The KPA values are about 2" of vacuum apart from each other.

So from 36 KPA, its about 19, 17, 15, 13, 11, 9, 8.5, 6, 4, 1" of vacuum as you move toward the top of the Y axis. Makes it easy for me to correlate to the vacuum gauge. If you notice, I pull all the vacuum timing at 73 KPA, which is about 8.5" of vacuum. That's about where my power valve opens. So it drops the vacuum timing, the PV opens and I'm rich and retrded as I approach WOT.

For the vacuum advance, I copied the behavior of the aggressive advance cans from a late 60s distributor. The vacuum timing starts at about 8" and comes all in by 15" of vacuum. At 15", it adds 12 degrees of timing. There are some cells where it deviates, mostly around peak torque and high RPM cruise where I was being careful with the tune.

[68 Firebird]

Sunday was a beautiful day. Was able to do more fine tweaking.
After a nice highway run adjusted idle rpm on carb and now
she idles at 650rpm in gear, like butter.
Curb idle rises to 725ish when placed into park.
This is the map she ran best with. Very responsive from
idle thru WOT. She does not like a lot of VA, car feels milder.
16 initial
36 total @3000
8 vacuum advance
While running down highway gauge shows 2850rpm or so at 65.
3:08 gears are sweet for highway runs.
Cooler out and temp was only over stat while on highway. Dropped
To stat temp once off highway. 170 degrees NOS Delco stat.
I am paying attention to the vacuum gauge now that I have one.
In gear 15, at highway light load 19, decal coming off highway I surprised
To see 22. Does the vacuum numbers look in line with what should be expected.
Thanks and have fun.

Gerry

[JLMounce]

If you add a couple degrees to your idle timing you'll probably see a bit more vacuum at idle. Your cruise and decel figures are great, especially if you're using power brakes.

That said, if you are enjoying the way the car is behaving, don't let perfection become the enemy of good enough.

Based on your table, it looks like you're using 750 as your idle speed, but you've set the carb idle to 650. That may be adding some timing on it's own as it interpolates down to the 550rpm cell. I learned while helping my uncle that the PI software wants you to command total idle timing. Not base idle timing with vacuum advance added. I'd give it 18-20 degrees for total idle timing and set your idle rpm in the tune to 650.

[68 Firebird]

So I should set 550rpm column up to 650.
And add a few degrees to both 650 and 750 column?

Gerry.

[JLMounce]

Originally Posted by 68 Firebird

So I should set 550rpm column up to 650.
And add a few degrees to both 650 and 750 column?

Gerry.

No, tap on the 750 column footer and you should get a scroll wheel. Move that to 650 to match your actual idle. Then change everything in that column to 18 degrees. You're increasing timing, so this may result in a higher idle, you may need to re-adjust the carb to reset your idle at 650.

I would start by leaving everything else the same.

That 550 column is there in case the engine is trying to stall, ignition advance increases to help create more torque and increase engine speed. Leave that as is.