6-hemi ignition controller: Anybody using one?

[RockinRobin]

My 5.7 based stroker is carbureted and I'm using an MSD 6-Hemi controller.
I assume the base advance curve is pretty mild and I was wondering if any of you have experimented with the curve and have something you like that doesn't have detonation.
Thanks!

 

[Rat Patrol]

I am - and I have experimented with it.

First - Not only is the supplied curve fairly lazy - but the MAP curve is set up really weird.

This is important to understand - A MAP sensor or a vac advance on a distributors job is to add timing at low Man Pressure (Hi Vac) and slowly reduce to zero under WOT.

MSD have set this up so that as the Manifold Pressure increases under WOT, not only does the MAP advance drop off (as it should) - BUT it actually keeps dropping below ZERO -

This means the MAP is actually pulling timing out of your RPM timing curve under WOT. Which is crazy!

So here's the fix.

Step 1 - Change your MAP timing graph so that the line does not go BELOW Zero degrees.

The MAP curve is OK as far as how much timing it adds..and at what pressure it starts to reduce - Its just that it shouldn't go below Zero value.

Check these pics -

The 1st is the supplied MAP curve - note how it holds at 12 degrees added to your RPM timing and then starts to reduce as pressure builds - but THEN, it keeps going and starts to rip timing out of your RPM curve at 11 PSIa.

This is what it should look like - you don't want the MAP interfering with your WOT RPM curve at 11 PSIa and higher.

 

[Rat Patrol]

Now as far as your RPM timing curve -

I used a recommended timing curve which was fairly "safe" at start up - This one.

Reading this graph -

At cruise - it tells you that my RPM based timing at 3000 rpm was 23 degrees "mechanical" PLUS 12 degress MAP = 35 degrees at 3 PSIa (cruise manifold pressure)

At WOT - It tells you that at 3000 RPM at WOT ( 13 PSIa) my timing was 23 degrees.


So I hope that explains how it works

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After few tweeks on the dyno - we ended up running this one:

As a test - we upped the WOT timing to 30 degrees at 5000 rpm...and it made a whole 1.2 more RWHP...so 27 degrees was what we decided on.


Finally - I haven't experimented with a curve that brings the timing in any quicker - to me the risk of melting a hole in a slug wasn't worth the tiny improvement.

BTW - My car just ran 112mph at the track...so the motor is making good HP for its small cam and single carb.

 

[Rat Patrol]

BTW - what intake and carb are you running?

 

[Barracuda_Barry]

I run one on a basically stock 05 5.7 with a XFI273 cam and headers.
I haven't had the time to move timing around to find the best setup.
I started with 12 degrees initial and ramp it up to 26 total by 3000.
Map is 0. I don't care about driveability at this point.
Thought it would be a safe starting point with this low compression engine.

 

[RockinRobin]

BTW - what intake and carb are you running?

It is a copy of the Mopar Drag Pak intake and a 1050 Dominator modified by Pro Systems.

I don't have a map sensor on my motor, so I wonder if the MAP settings will affect anything, or if that's why the idle is so rough, need more timing from about 700-1400RPM to compensate for lack of MAP advance.
Thanks a bunch for the info!

 

[Barracuda_Barry]

It is a copy of the Mopar Drag Pak intake and a 1050 Dominator modified by Pro Systems.

I don't have a map sensor on my motor, so I wonder if the MAP settings will affect anything, or if that's why the idle is so rough, need more timing from about 700-1400RPM to compensate for lack of MAP advance.
Thanks a bunch for the info!

The nice part is you can sit there with your lap top and add more timing.
You can find out what it likes at idle pretty quick.

 

[Rat Patrol]

I'm reviewing my MAP graph...I'll let you know what PSIa my engine makes at idle and the at cruise so you have more to work with.

 

[RockinRobin]

I'm reviewing my MAP graph...I'll let you know what PSIa my engine makes at idle and the at cruise so you have more to work with.

Thanks. With no MAP sensor, I might have a weird curve that has lots of advance up to about 1200rpm then drops off before coming back up again. Considering removing the intake manifold and drilling a hole for a MAP sensor.
Merry Christmas!