What's up with the Spark Advance curves for the 305 MAF engines?

It looks like the folks at GM did a major compromise on performance and didn't do any 305 performance tuning. The 3D graph is FLAT across the top....

If you look at a graph print of ANZA bin, the latest greatest 1989 305 5 Speed bin, as compared to a Corvette 6 Speed bin for the same year (APYP) it is MUCH different on top, at the higer RPM's. Or if you look at ARAP, (which I think is for an automatic trans), it is also much different. I realize that both of these bins are used on 350 engines that probably used aluminum heads, thus the high timinig advance numbers, but still... If you were to compare the 305 curves to them it seems just wrong...

Does anyone have a "Players" 305 5 Speed bin? I wonder if it's Spark Advance was custom tuned like ARAP or the Vette's APYP...

 

One thing Ive learned about spark advance is its not about having more or less. Its about having just the right ammount. Ideally, the timing should be set to make sure that the mixture is done burning at just the right time. The only way to set the curve up will be to experiment with various ammounts of timing to see what works. At P/T, you want to set it up so the car is responsive and doesnt run rough, have detonation, or overheat the engine or exhaust. At WOT, you want to tune for max performance without knock or running rough.

 

I have a 1992 Player's PROM. Spark advance looks interesting. Curious things are spark reduction at the shift points (IE. going from 2-3 where the RPM drops to). I haven't look at it too much as I've been working on the MAF setups. I can try to post a pick of what the spark table looks like.

Mark.

 

 

Does this help?

If you are working with MAF ... I found the 305 "auto" pretty bland for spark advance. I ended up using a 305 standard and a 350 auto to create a baseline for my son's project. Still needs work ... but slowly progressing.

 

What bcc are you showing ?

 

BCC as in the code on the PROM? There is none, it's a race only part from GM given out to the race teams each season and then returned at the end of the season. This one is from a 1992 Trans Am, never raced.

 

Hey Mark_ZZ3 any chance of getting a copy of that bin?

 

 

Seeing as you are in Calgary ... we could meet up the next time I down that way. Have some Java and talk cars.

There are a number of Players car owners in your town.

The PROM's weren't calibrated as the "fastest" chip, but certainly were setup for wide open throttle driving AND making the engine's last.

My plans for the PROM are to map out the differences from stock and write up an article on it. Nothing too scientific. I'm curious about some code in the chip that doesn't seem to map out to stock at the end. Curious if there is more code in addition to changes in tables and such.

Mark.

 

As a 305 owner I would love to get my hands on that BIN to compare with mine!

Please post! I'll swap you my SLP Performance Package BIN for it?

 

New to PROMs but I would also like a copy of the players .bin as well as the SLP .bin.What would I have to do to get u gentlement to send me those files as well... Plz... maybe we can discuss cash through PM if need be

 

To the OP, the 305's smaller bore, smaller combustion chamber and iron heads dramatically change the timing requirements compared to an aluminum headed 350. Other huge factors determining timing requirements is is quench distance, spark plug location in the chamber, combustion chamber shape, fuel atomization, and velocity of intake charge which affects tumble and swirl. Dimented couldn't have been more correct when he said it's about getting the right amount, not more or less.

As for posting a copy of the GM "race" .bin for the 305s, that would be awesome, I'd love to see it.

 

Here is some excel graphs. I've been looking at various spark curves.

The top is the R7U, the middle is a stock 1989 non-vette, and the bottom is a hybrid I added spark from 5 speeds to make what I thought was an aggressive curve.

The R7U has an amount of spark removed in the 3200RPM range which is where the RPM's drop on gear change. My assumption is that they removed spark to avoid dentonation/knock vs. letting it occur and have the ECM retard timing. Most likely to keep the engine reliable.

 

Here is the spark table from the R7U bin ... CSV format. Cut paste and load into your editor.

,20,30,40,50,60,70,75,80,85,90,95,100
400,24.96,24.96,24.96,24.96,23.91,18.98,17.93,16.17,11.95,5.98,5.98,5.98
600,24.96,24.96,24.96,24.96,23.91,18.98,17.93,16.17,14.06,9.84,5.98,5.98
800,24.96,24.96,24.96,26.02,24.96,22.15,21.09,17.93,17.93,16.88,11.95,8.09
1000,24.96,26.02,28.83,29.88,24.96,22.85,22.15,22.15,22.15,17.93,15.12,13.01
1200,24.96,28.13,31.99,29.88,26.02,24.96,22.85,22.15,22.15,21.09,20.04,17.93
1400,24.96,28.13,35.16,30.94,28.83,27.07,26.02,24.96,26.02,24.96,23.91,21.09
1600,24.96,28.83,37.97,35.16,31.99,28.13,28.13,28.13,28.83,28.83,27.07,22.85
1800,24.96,28.83,37.97,36.91,33.05,30.94,30.94,29.88,29.88,28.83,27.07,23.91
2000,29.88,33.05,37.97,37.97,35.16,34.1,34.1,33.05,33.05,30.94,28.13,23.91
2200,35.16,35.16,37.97,37.97,37.97,35.86,35.16,35.16,35.16,31.99,28.83,23.91
2400,35.16,37.97,37.97,37.97,37.97,36.91,35.16,35.16,35.16,33.05,28.83,23.91
2800,35.16,37.97,37.97,37.97,35.16,36.91,36.91,35.16,31.99,28.83,24.96,22.15
3200,35.16,37.97,35.16,37.97,35.16,35.16,34.1,30.94,28.13,26.02,21.09,22.15
3600,35.16,37.97,36.91,37.97,37.97,35.16,30.94,28.13,26.02,23.91,20.04,21.09
4000,35.16,37.97,37.97,37.97,37.97,35.86,31.99,28.83,27.07,23.91,22.15,22.15
4400,35.16,37.97,37.97,37.97,37.97,37.97,36.91,34.1,29.88,28.13,23.91,26.02
4800,35.16,37.97,40.08,40.08,40.08,40.08,37.97,35.86,35.16,31.99,28.83,26.02
5200,35.16,37.97,40.08,40.08,40.08,40.08,37.97,35.86,35.16,31.99,28.83,26.02
5600,35.16,37.97,40.08,40.08,40.08,40.08,37.97,35.86,35.16,31.99,28.83,26.02