MSD 6530 with MAP sensor

[lippy]

I was inspired by Tom MSD 6530 with throttle postion sensor

I decided to swap out my old MSD box with the newer 6530, which is programmable and can use a MAP sensor. So far, it's been really nice.

Rewiring it was no big deal, but the harnesses are different. The size of the 6530 box is smaller as well, so I made an aluminum plate that bolted into the old screws, and I mounted the new box on that plate. I also had to lock out the distributor, which turned out to be harder than I thought. On an MSD FE billet distributor, the gear is press fit onto the shaft. After removing the pin, and even with a puller and a vice, it wouldn't budge. This made me think that if and when I do get it off, I won't be able to get it back on and aligned properly with the pin hole. So I took a different approach. I considered welding it at the top of the shaft, like some people do, but I wanted it to be reversible. Instead, I tapped and drilled a hole so the black hex machine bolt shown below locks the distributor, I added a dab of blue Loctite so it doesn't go anywhere. This worked perfectly.

The next thing I had to do was phase the rotor. I bought the MSD racing/phasable rotor top, drilled a hole in an old cap at the #1 post, marked the center of the rotor, and checked the phasing. Sure enough, it was off. Per MSD's instructions, I set it at the midpoint of the timing range I would be using, and I get good proximity at both the most retarded and most advanced timing settings I'm using.

The way the 6530 box works is that you set the timing at maximum advance, and you program in two retard curves. One as a function of RPM, and the second as a function of manifold vacuum. I typically run 37 degrees maximum mechanical advance without any problems, and I plan to add another 10 degrees under light load for part throttle responsiveness and cruising efficiency. My approach was to run it first without the second advance curve to make sure it's right, and then to add in the second advance curve. I also should mention you program these curves on a PC and then download them via a serial port into the MSD box. You need a USB to Serial cable, but not a huge deal.

I set the total timing at 47 degrees (maximum) and configured a pretty standard RPM advance curve. This curve retards at start and has all the timing in by 2500 RPM or so. It also retards a couple of degrees at peak torque. At this point, I hooked up the MAP sensor, but set the vacuum timing curve to -10 degrees across the board. This way, I will max out at 37 degrees. I took it out for a few runs, and everything worked perfectly.

During my test runs, I monitored my vacuum to see where I want to set the vacuum curve (and also my carb power valve). It turns out vacuum at idle with this new cam is 17 in Hg, vacuum at cruise is 14-20 in HG, and vacuum at part throttle (say 40%) drops to 9 in Hg. Accordingly, I went back and set the vacuum advance curve so I get the full 10 degrees of advance at idle/cruise vacuum down to about 10 in Hg, and at that point I start taking out timing until it is all out at about 8 in Hg. This way, if I add the two curves, I get up to 47 degrees (like a vacuum distributor) at light load, and with throttle it drops to 37 degrees, with a couple more degrees taken out at peak torque.

Last thing, I welded up a little bracket for the map sensor and attached it to the firewall using an existing heater mounting bolt. It looks fine. You can spend a lot on a MAP sensor, but you can also get them from Amazon or Summit pretty cheaply, and I don't think there is a big difference.

Between the new cam and intake, and the timing curve enabled by the 6530 box and MAP sensor, it's a different car. I'll try to post some photos later.

[patrickt]

That's a nice success story. I take it the car is now a little more docile to drive in bumper to bumper traffic?

[Gaz64]

Good on you Lippy.

You are probably only the third person after myself that I have read about that understands the system.

I see so many posts on the MSD website, where users can't comprehend it.

It is a great feeling when you can have your cake and eat it too.

[DanEC]

Lippy - that sounds like a really nice unit that is easy to play around with. Impressive to the old points and condenser guys like me.

[lippy]

Here are the photos:

(1) My method of locking the distributor, which I think is far easier than what MSD recommends

(2) The MAP sensor, insulated and mounted on the small stainless bracket I welded up

(3) The curves I'm using on the 6530 ignition box. The way this works is that you set the maximum timing, in this case 47 degrees, and the timing on the graphs is taken out of the total. Also note the vacuum curve is in PSIa, and not in Hg. It's easy to convert (e.g., 8.5 PSIa is 17 in Hg and 10 PSIa is 9 PSIa).

Vacuum Conversion Calculator

[Gaz64]

Originally Posted by lippy

Also note the vacuum curve is in PSIa, and not in Hg. It's easy to convert (e.g., 8.5 PSIa is 17 in Hg and 10 PSIa is 9 PSIa).

Vacuum Conversion Calculator

Not quite correct there.

Here is my table:
psia inches Hg
0----- 30
1----- 28
2----- 26
3----- 24
4----- 22
5----- 20
6----- 18
7----- 16
8----- 14
9----- 12
10---- 10
11---- 8
12---- 6
13---- 4
14---- 2
15---- 0

So 8.5 psia is 13 inches Hg, and 10 psia is 10 inches Hg.
By coincidence 10 is 10, but in any direction, the figures are obviously different.

5 inches Hg (typical Holley power valve) would be 12.5 psia.

Hope this helps.

Gary

[A98Coupe]

Jeff,

After reading Tom Kirkham's post last year I've gone down the same route as you, but I'm not finished with the installation yet. Your method for locking out the distributor looks far better than what MSD recommends. I wasn't looking forward to pulling the gear off the shaft! Great post and gives me some good retard map info. to get started. You could also add a notch in the run retard curve at 1000rpm to help keep the rpm steady - as per Tom's previous post.

Regards
Stuart

[lippy]

Originally Posted by A98Coupe

Jeff,

After reading Tom Kirkham's post last year I've gone down the same route as you, but I'm not finished with the installation yet. Your method for locking out the distributor looks far better than what MSD recommends. I wasn't looking forward to pulling the gear off the shaft! Great post and gives me some good retard map info. to get started. You could also add a notch in the run retard curve at 1000rpm to help keep the rpm steady - as per Tom's previous post.

Regards
Stuart

Once you figure it out it's really easy to adjust the timing and experiment. I started out by making the vacuum retard curve a constant -10 degrees just to make sure everything worked properly. Once I felt good about that I started adding timing on the vacuum curve. Of course you don't want too much advance, and that was the approach I took.

[A98Coupe]

Hi Jeff,

Just sent you a PM

Regards
Stuart