Programmable MSD 6AL-2 questions

[SSLance]

I am swapping out the CCC Quadrajet, Distributor and ECM for a mechanical Quadrajet, Pro-Billet MSD #85551 Distributor and MSD #6530 Programmable MSD 6AL-2 ignition box today. The CCC system ran very well but I had a few issues with it that were not correctable so I decided to go this route vs upgrading this engine to EFI.

After gathering up most of the parts, I put power to the ignition box on my bench to test and make sure the serial to usb adapter I picked up would let my laptop see the box, it did.

I bought the box gently used from a somewhat local guy that told me he had changed the rev limiter and timing curve in it, so I tried to view them to change them back to a somewhat factory default setup for my initial start. I found the rev limits easily and could change those, but in the MSD Pro-Data software I can not figure out how to see and\or change the timing cure. I"m certain I'm just not pressing the right button or something stupid but it has me befuddled. Is anyone proficient in using this software that can help a newbie get his feet wet in this area?

My engine is a crate GMPP HT383, basically a 9.1 compression, vortec heads, Camshaft Type (P/N 14097395): Hydraulic roller Camshaft Lift (in.): .431 intake / .451 exhaust Camshaft Duration (@.050 in.): 196° intake / 206° exhaust with an aluminum dual plane intake and 1 5/8s mid length headers.

It shouldn't take anything really radical or special for a timing curve, the book suggest 32 degrees total timing with a 6000 RPM max. Cruising RPM is 1700-1800 RPM in 6th gear and the car weighs 3500#s or so. I probably could have gotten by with an just an e-curve MSD with or without a 6AL box, but I picked this box up for a decent price and MSD said the best distributor to use with it is the 85551. Plus, I like tinkering with things and this box will really let me fine tune the ignition for my needs.

Anyway, I realize this isn't EFI and computer timing, but if anyone used to mess around with old school ignitions and primarily has used this programmable ignition box and software and can help a newbie learn it, that would be great. I kind of want to make sure I know what's in the box before I fire it up for the first time if you get my drift.

[SSLance]

Wow, I must have had a really good night's sleep because I dove back into the software and I discovered the "add dot" button on the timing graph and I am not plotting a timing curve!!! :idea: :computer: :clap:

So, given my engine parameters above...should I put it at -22* at 0 RPM and ramp it up to 0* say at around 2000 RPM for an initial set?

That would be like 10* initial timing with 32* total, correct? That puts the cruising advance at about 26-27*.

[68Cuda]

You can add a MAP sensor input to the box and tweak advance vs. engine vacuum. It actually works backwards... you add advance, then pull it out based on a vacuum vs. retard curve. This will allow you to run more advance under low load...

[68Cuda]

Make sure to lock the distributor.

Also look a the programmable start retard function. This box has a lot of cool features.

[SSLance]

I did get the distributor locked out and got it installed in the car. I'll have to wait until I get some expert carb help to straighten my q-jet out before I can attempt to fire it up though.

I did read that about the MAP sensor. I actually have a MAP sensor on the car now that the CCC system used. I need to do a little digging to see which one it is and if it will work for this application.

I'm pretty stoked about being able to fine tune the ignition side with this box, should be fun.

Transferring the file to the MSD...

https://lh3.googleusercontent.com/-dYhwVw7WN1E/VJ7fTSMAG3I/AAAAAAAAR88/fbl1VAirB7M/w1215-h685-no/IMG_20141227_102754_147.jpg

The basic timing curve I'll start with to get it running.

https://lh3.googleusercontent.com/-H2yM2t7VUJg/VJ7fg70odCI/AAAAAAAAR9I/DAFi6r_lD5g/w1215-h685-no/IMG_20141227_102818_165.jpg

[SSLance]

With the factory ECM and harness out of the way, it looks like the new MSD box will slide right into the pocket the ECM used to set in and the wires will feed right out the same hole the CCC harness used.

https://lh3.googleusercontent.com/-Y20nCIdhhEQ/VKgoRV6aDTI/AAAAAAAASDk/wRss5jIp9AU/w913-h685-no/DSC06048.JPG

https://lh5.googleusercontent.com/-AEGL-TCRzRA/VKgoREZRBbI/AAAAAAAASDg/01yk7AjLhPk/w913-h685-no/DSC06047.JPG

https://lh5.googleusercontent.com/-QmmK2sMswxc/VKgoPWe8b5I/AAAAAAAASDQ/SqSaLgPUi2c/w913-h685-no/DSC06046.JPG

Does anyone see any issues with me just sliding the MSD box into this slot in the plastic kick panel to hold it in place?

It almost seems too simple and easy... :D

There isn't room in the slot to put the rubber feet the MSD box comes with though, the box itself just barely fits into the plastic pocket. Not sure if the box creates too much heat for the plastic or if the plastic will transfer to much vibration to the shell of the MSD box? I can't imagine either being a problem though as the box is digital now and the factory ECM has been riding in that slot for 30 years now with no issues.

[Che70velle]

Lance, i ran MSD in my racing days, and I'll tell you, I always had a spare one in the hauler, wired up with quick connector, ready to go. I can honestly say that I had more MSD box failures, than I had flat tires, in all the years I raced. If I were you, I'd get a spare box, and have it ready to go.
I ran the 6ALN box, which never really got hot. I'm not sure about the particular box you have, as far as heat goes, but I'd think that there would be ventilation in the kick panel area? I don't feel that vibration or harmonics should be an issue from the plastic panel. If you strapped it directly to something metallic, that would be a different sermon. I like what your doing with your car this winter.

[SSLance]

Thanks Scott. MSD says in their instructions that they do not recommend installing the box in an enclosed area like a glove box. This area has open slots on the top, bottom and toward the firewall for air to circulate through but would have plastic right up against the top and bottom of the box. With the box being all digital I can't imagine vibration or heat being an issue...plus it'll be a much nicer environment for the box there than out on the inner fenderwell.

I'll probably wait and ask the MSD tech on Monday before permanently running the wires but I think this is where it's gonna end up.

[SSLance]

Looks like MSD approves of the spot...

that wil work out fine... if the ecu was mounted there ...I really don't see any problems.

[SSLance]

Alright, an update... I've had the car running again for about a week and man, what an improvement in horsepower so far. Haven't had it back to the dyno yet but my butt dyno approves so far.

I ended up plotting the retard curve to 7* advanced at idle (20" vacuum) and a pretty linear curve starting at 1000 RPM at 7* ending at 32* advance at 3000 RPM. I believe it would actually like a little more timing on the top end and a little less timing at idle but the box is limited to 25* of retard so this is the happy medium so far. It runs great, starts great, idles great, and I haven't heard even a hint of detonation anywhere and I've tried to get it to ping.

You can add a MAP sensor input to the box and tweak advance vs. engine vacuum. It actually works backwards... you add advance, then pull it out based on a vacuum vs. retard curve. This will allow you to run more advance under low load...

Okay, I have a 1 bar MAP sensor hooked up to the box and manifold vacuum...but no boost retard curve plotted yet. This is where I need a little bit of laymans help once again helping me understand vacuum advance and how to use it to better the performance from my car.

I finally have almost gotten used to thinking about timing advance in reverse with this box...but vacuum advance, boost retard is still real foggy to me...not to mention how to set it up to work best in my situation.

Here is my graph at idle as it sits now.

https://lh3.googleusercontent.com/-VJM7qyHQOoM/VPs1dxU8YmI/AAAAAAAATHE/FgQhtJ8VeGs/w1218-h685-no/0307151129.jpg

and like I said it's pulling 20" of vacuum at idle

https://lh6.googleusercontent.com/-s6AXMVBqBBg/VPs1kjOGZAI/AAAAAAAATHQ/TRJV18-WxlY/w1218-h685-no/0307151129a.jpg

When I had the initial at 10* it was idling at 1100 RPM and pulling 23" of vacuum.

Can anyone help me with a easy to get tutorial on how to set up a boost retard curve that will help this engine using the MAP sensor?

Or just tell me what I need the MAP sensor to tell the box what to do...where and when do I want it to add advance and where and when do I not want it to add advance?

If someone can help get that through my thick head, I believe I can figure the rest out. I have to say, it was pretty effing cool to grab a dot on the graph, drag a line, and hear the engine change when responding to the change I made. I really dug that. I believe I could do the same with the boost retard curve, I just need to understand exactly what I'm trying to do first.

Thanks...

[68Cuda]

Or just tell me what I need the MAP sensor to tell the box what to do...where and when do I want it to add advance and where and when do I not want it to add advance?


Overall adding vacuum advance will make the car run better under "normal" driving and have no effect on performance under full throttle.

So your MSD boost graph in the menu is in PSI. 14.7 PSI at sea level is 0 vacuum... every 1 psi = about 2" of vacuum. So, 10" vacuum is about 10 PSI and 20" vacuum would be about 5 PSI... now, if that does not confuse you, the graph adds retard, not advance. So, not only is the pressure graph kind of backwards to conventional thought, so is the advance.
EDIT: I think this is because this is usually used for BOOST retard... for example 10PSI boost (only airplanes use inches of boost) would be 24.7 PSI absolute. 14.7 PSI absolute pressure is no boost AKA 1 bar, AKA 0" vacuum.

Make sure you have the correct MAP sensor (1 bar) and the setting for that is correct on the MSD.

So, if I want 15 degrees advance at 20" of vacuum, I set 15 degrees more initial than previous, set my retard to 0 for anything up to 5psi, then slowly ramp in 15 degrees of retard all in by 14.5 PSI. This would give you a linear 15 degrees of "advance" from 0 to 20". What is the best curve - I don't know. I think the stock distributers can give you somewhere around 20 degrees at 20". I would start with, maybe 14, see how it likes it, progressively try more. This will cause you to have a higher advance while at idle, but that is OK, it will idle a little smoother, take less throttle screw and be less likely to diesel when you shut it off.

[SSLance]

now, if that does not confuse you, the graph adds retard, not advance. So, not only is the pressure graph kind of backwards to conventional thought, so is the advance.

:waveflag:



So, if I want 15 degrees advance at 20" of vacuum, I set 15 degrees more initial than previous, set my retard to 0 for anything up to 5psi, then slowly ramp in 15 degrees of retard all in by 14.5 PSI. This would give you a linear 15 degrees of "advance" from 0 to 20". What is the best curve - I don't know. I think the stock distributers can give you somewhere around 20 degrees at 20". I would start with, maybe 14, see how it likes it, progressively try more. This will cause you to have a higher advance while at idle, but that is OK, it will idle a little smoother, take less throttle screw and be less likely to diesel when you shut it off.


I don't think I want any more advance at idle...do I? The throttle blades are completely closed and it's idling at 14.7:1 AFR at 850 RPM. Any advance at idle I add just increases the idle RPM and vacuum. I guess I could start fiddling with the idle air screws to dial them down, but am I just chasing my tail here? Heck I was trying to get the initial down to 6* to try to slow the idle down a bit more.

It's good like it is. It drives great, no issues anywhere. Maybe just a bit of a stumble when lugging it with the primary side about half open, but giving it just a bit more gas clears that right up.

I guess maybe that means it wants a bit more advance say at 1000-1500 RPM with high vacuum...right? and as soon as that vacuum drops (throttle opens) take that advance away so it doesn't detonate.

[68Cuda]

I don't think I want any more advance at idle...do I? The throttle blades are completely closed and it's idling at 14.7:1 AFR at 850 RPM. Any advance at idle I add just increases the idle RPM and vacuum. I guess I could start fiddling with the idle air screws to dial them down, but am I just chasing my tail here? Heck I was trying to get the initial down to 6* to try to slow the idle down a bit more.

It's good like it is. It drives great, no issues anywhere. Maybe just a bit of a stumble when lugging it with the primary side about half open, but giving it just a bit more gas clears that right up.

I guess maybe that means it wants a bit more advance say at 1000-1500 RPM with high vacuum...right? and as soon as that vacuum drops (throttle opens) take that advance away so it doesn't detonate.

I can't imagine you are going to surpass 20". I say try it out. It would only take a few key strokes to change it back.

[SSLance]

I'm not sure why I'm not getting this, I'm certain that the people that are helping me know what they are talking about, but it's like they are talking in different languages and it's not making any sense to me at all.

And I don't want to be the guy that is asking someone else to do the work for me, I really want to understand this myself.

The MSD Tech replied with this...

you will use the boost curve....and a 1 bar map sensor ( typical gm from 92 to 96 car or truck )

remember :...with key on ...a thin red line will appear...
left of the line is vacuum
right of the line is boost

and this graph...

https://lh4.googleusercontent.com/-ZO8HQippD_8/VP88BRAoPGI/AAAAAAAATLA/JmcHEJQrrAM/w663-h520-no/MAP%2BEXAMPLE%2B6530.JPG

I guess what I'll do is rig up a long piece of vacuum line and get the vacuum gauge and my laptop (hooked to the MSD) in the passenger area of my car and go for a little drive. I can't really see what the vacuum and advance are doing in their current state without putting a load on the engine, which I can't do in the garage.

Maybe once I see what all of the gauges and graphs are doing as I load the engine, I'll have a better idea of what to change to make it better.

I'll probably hook the GoPro up pointed at the gauges as well to record what I'm doing.

I took the AFR meter out as it was not hard wired yet and I didn't want the fab shop to have to worry about heating the O2 sensor up every time they moved it...maybe I'll throw it back in the car as well to watch it too since the fab shop won't be ready for me until this weekend now.

Wish me luck and thanks for all of the help...I really appreciate it.

[68Cuda]

and this graph...
https://lh4.googleusercontent.com/-ZO8HQippD_8/VP88BRAoPGI/AAAAAAAATLA/JmcHEJQrrAM/w663-h520-no/MAP%2BEXAMPLE%2B6530.JPG


OK... is this your boost retard graph, if so it is currently doing nothing!

This is an "example" curve to dial in 10 degrees of retard progressively with 10 PSI of boost. Your car is naturally aspirated - correct?

The 14.75 point you see on that chart where the red and blue meet is "0" boost -or- "0" vacuum. It is the 14.75" reference point of atmosphere, the same pressure as your outside air.

If you are not running boost, to get 14 degrees of "advance", do the following: From 0 to 5 PSI on that chart set the "degrees of retard" to "0" (same as it is now). Then, from 5 PSI to 14.5 PSI have the chart slope down from "0" to "14" degrees of retard. From 14.5 PSI to the right leave it at "14". After setting this curve, set your timing to your current 7 degrees initial with the vacuum unplugged from the MAP sensor. When you plug in the MAP if the vacuum is 20", it should jump to 21 degrees. If you have a hand vacuum pump you can test this through the range to make sure it does what you think. Anytime you want to disable the advance and go back to your base curve it can be as simple as unplugging the vacuum line from the MAP and capping the manifold port. This will dial in the full 14 degrees "boost retard" and effectively put you bask to your 7 degrees base timing.

I took the example they sent and superimposed the curve I described as a purple line, why MSD does not illustrate this is beyond me. If you like the outcome and want to dial in more, say, up to 20, then instead of going to 14, go down to 20 at the same point and reset your base timing.

[SSLance]

Okay, I think this is starting to sink in...thanks...

How my brain looks at this now is 14.75 PSI on the graph is zero vacuum or WOT and at that point there is no advance from the MAP sensor\boost retard curve. When the throttle is closed and vacuum increases, the graph moves to the left and the further it goes to the left the more advance is being added to the distributor. Furthest left is full advance at max vacuum at idle (based on your curve shown anyway).

Last night I drove the car with the laptop and vacuum gauge inside the car so I could watch. At idle and when at high vacuum when running the red line in the Boost Retard graph stays right around 7.00 PSI with the vacuum gauge at 20"

I never saw the red line go less than 7.00 PSI. So should I start the left side of the curve at 7.00 PSI or at 4.00 PSI as in your graph. And the bottom of the curve should level off at 14.75 PSI all of the time right?

The one thing I'm still fuzzy on, the relation of the 20" on vacuum gauge to 7.00 PSI on the graph.

[SSLance]

Sometimes I do some of my best thinking in the shower in the morning... :D

I did some playing around with the curves, please let me know your thoughts on these. I haven't put them in the box yet.

First, my engine likes 7* at idle and 32* total. Actually I think it would like 6* and 33* better, more on that in a minute.

Here is my current Run Retard curve

https://lh3.googleusercontent.com/-ehGxY-P6gWM/VQBZfWRuH7I/AAAAAAAATMM/n2T6s3ALXEQ/w435-h563-no/Run%2BRetard%2BCurve.jpg

I don't think I want to add any vacuum advance in at idle, I think I want it to kick in just off idle...so here is my idea for a Boost Retard Curve...

https://lh6.googleusercontent.com/-XRgmLpkE_rU/VQBZfYZNUXI/AAAAAAAATMQ/uwJHLg07USU/w435-h563-no/Boost%2BRetard%2BCurve.jpg

It currently idles at 850 RPM and around 7 PSI

Now...and this is where my brain starts kicking in... :D Can I use the Boost Retard Curve to pull even more timing out at idle, say instead of the curve being at 14.0 from 6 PSI to 8 PSI, can I put that at 16.0 to pull another 2* of timing out at idle?

This would let me bump my full advance up to 33* and still let it idle at say 6*...

[68Cuda]

I don't think I want to add any vacuum advance in at idle, I think I want it to kick in just off idle...so here is my idea for a Boost Retard Curve...

I would not make sharp transitions like that, it could cause the engine to surge, oscillate between two points or do something funny. Sharp transitions in control systems are never a good idea.

Why the aversion to running so much advance at idle under no load? It may actually let the engine run cooler. As soon as you put a load into it the advance will drop out. People run locked out distributors at full advance on race cars, I don't think your idle speed is going to run away or anything funny. Just try it out and see how it behaves, you can always plug off the vacuum port and disconnect the MAP sensor until you can change it back if it does something you do not like. Disconnecting the MAP sensor will trick it into thinking you have no manifold vacuum and it will pull out all the timing. If you are worried try a smaller amount to begin with, like 7-10 degrees. Just match the amount of advance you put into the initial timing with the amount you take out with the "Boost Retard Curve".

It doesn't matter much if you start at 4" or 7", it just changes the amount of advance a little. Starting at 7" should be fine since that is where your MAP sensor is telling you the engine runs. You can also cheat the end point on the right a little. When you disconnect the vacuum from the MAP does it read 14.75"? I would want the full amount of spark advance pulled out before that point, maybe set it to 14" even to have some margin

The difference between 5" and 7" could be the MAP sensor calibration or your vacuum gauge, either or both could be a little off. 20 sounds like a lot to me for an engine that is not stock, maybe your gauge is a little generous or non-linear. It does not matter much, it is just a reference point, use the MAP sensor since it will be controlling the spark.

[SSLance]

Now that I'm getting a good handle on the timing and can make changes easily and monitor them immediately, I'll get back with my carb guy and discuss how to make changes to the carb as well.

As the carb sits now, with 10* of initial timing it was idling at 1100 RPM with 23" of vacuum with the throttle plates closed. If he says it's an easy enough adjustment to the idle\air screws (that a noob like me can handle) I'll make those changes today and report back.

I put the O2 sensor and air fuel meter back in the car last night and plan on driving it to work today and should have some time to tinker, drive, tinker, drive etc...

Thanks...

[SSLance]

Pretty interesting and educating trip to work this morning. I was mainly looking at vacuum and AFRs at cruise speeds.

In 5th gear at around 2200 RPM (70ish MPH) the engine was extremely happy. Pulling 20-22" of vacuum, barely touching the throttle, would pull any hill with no effort...and AFRs at around 15.7:1 and steady.

I didn't have the laptop hooked to the Ignition box so I don't know what the timing was or what the MAP sensor said the vacuum was...but with no Boost Retard Curve installed, it was just Advance Retard working which would have put the timing advance at around 20* advanced.

In 6th gear at around 1700 RPM (70ish MPH) the engine was not happy. Vacuum was bouncing between 10-15", way more throttle input to keep it moving, lugged down on hills...and AFRs got fat, down to mid 12s to 14:1. Timing would have been around 15* advanced.

Engine certainly needs vacuum advance if I want to use 6th gear on the highway.

[68Cuda]

Pretty interesting and educating trip to work this morning. I was mainly looking at vacuum and AFRs at cruise speeds.

In 5th gear at around 2200 RPM (70ish MPH) the engine was extremely happy. Pulling 20-22" of vacuum, barely touching the throttle, would pull any hill with no effort...and AFRs at around 15.7:1 and steady.

I didn't have the laptop hooked to the Ignition box so I don't know what the timing was or what the MAP sensor said the vacuum was...but with no Boost Retard Curve installed, it was just Advance Retard working which would have put the timing advance at around 20* advanced.

In 6th gear at around 1700 RPM (70ish MPH) the engine was not happy. Vacuum was bouncing between 10-15", way more throttle input to keep it moving, lugged down on hills...and AFRs got fat, down to mid 12s to 14:1. Timing would have been around 15* advanced.

Engine certainly needs vacuum advance if I want to use 6th gear on the highway.

Sounds like you are starting to get the hang of it and also getting a better feel for things... once you dive in and start tweaking will be the fun part. Testing and observation is where you will learn the most, then you can come back here and tell us how it is done!

[SSLance]

I talked with my carb guy and he's a bit afraid that he's got too much idle air bleed in the carb itself which is a simple repair, but one that he'll need to do at his shop. For now, I'm going to try to turn the idle air mixture screws in a half turn and see what that does to the RPM and AFR at idle, then test on the way home.

It's funny because if going by the seat of the pants feel, the car drives GREAT... No hiccups at all, in the old days we would have left it as is...but by watching the data I can tell it's off in a few places and by dialing those in it'll only get better.

Man... I've had fun driving this thing around the last few days though. HUGE increase in upper RPM power. This was a much needed upgrade over the ignition and carb I was running before.

[Flash68]

Very cool Lance. Who says playing with carbs can't be "techie"? :D

I have not ran mine yet but my initial program is ready to test out after chatting with a couple of the MSD techs.

http://i236.photobucket.com/albums/ff245/flash68/null_zps2ee06904.jpg (http://s236.photobucket.com/user/flash68/media/null_zps2ee06904.jpg.html)

[SSLance]

A couple more test drives under the belt, along with several changes...and the car just keeps getting better and better and better.

It didn't like any adjustments to the idle air mix screws, just a quarter turn leaned it out too much and didn't change the idle so I put them back.

I decided to put some more timing in so I set the initial at 9* and bumped the rest of the curve up so it was all in (32*) at 2800 RPM. This put the advance at cruise speed in 6th gear at around 20*. The car really liked this in every way except it idles at around 950 RPM. Awesome power everywhere, no lugging and loading up, VERY smooth off idle on takeoff, no more shudder, and pretty decent pickup on 3000-6000 butt horsepower yet again.

So...still no pinging...lets add more timing! :D

Turned the distributor to 34* total and adjusted the curve to 9* initial once again with it all in at 2800 RPM. Air fuels are great still, low - high 14s cruising just depending on what I'm doing with the throttle and under WOT it's high 11s-low 12s. Did I mention it's FASTER!!! Man... :morepower

I don't think I'll mess with the vacuum advance until I can get some adjustments made to the carb. I've been told I can move the MAP sensor vacuum to a timed port and trick the box to not put any vacuum advance in until the throttle is cracked...but it's so good now, I think I'll just leave it as it is for now until I get some time to send the carb back to Bob. I'd like to get the carb to idle at around 700-750 RPM with as much timing as I can through at it before messing with the vacuum advance.

Thanks for putting up with me through this thread...hopefully some others will try this box as well now that they've seen a noob like me can figure it out. It really is cool to be able to tune the timing with a flick of your mouse. I've saved up a little stash and my next purchase is a back up box which will get loaded with the same tune and always be available it needed.

[68Cuda]

Very cool Lance. Who says playing with carbs can't be "techie"? :D

I have not ran mine yet but my initial program is ready to test out after chatting with a couple of the MSD techs.


Assuming... you are running about 34 total, that would be the equivalent of running 24 "initial", 10 "mechanical" advance, and an extra 10 "start retard". Not bad. Good performance strategy, and easier to start.

I know some folks that will weld slots in the distributor to be able to limit the mechanical to only 10 so they can run more initial. This makes it pretty easy doesn't it.

Do you have a MAP? Brave enough to try some "vacuum" advance?

[SSLance]

Very cool Lance. Who says playing with carbs can't be "techie"? :D

I have not ran mine yet but my initial program is ready to test out after chatting with a couple of the MSD techs.

http://i236.photobucket.com/albums/ff245/flash68/null_zps2ee06904.jpg (http://s236.photobucket.com/user/flash68/media/null_zps2ee06904.jpg.html)

That should work...but did they teach you the trick of starting the curve at 0* and then bringing it down to 20* at 200 RPM or so? This gives the engine advance for initial starting and reduces the chance of the engine kicking back (or something like that). That probably comes into play more with a higher compression, larger cam engine than mine, but I put it in mine anyway.

Let us know when you fire yours off and get to play with it a bit.

[68Cuda]

I'm still trying to figure out what I will be doing with mine. I bought it assuming I was going to run a carb.

Shortly after I bought it I ran across my dream intake up for sale that I had been keeping an eye out for a few years. They are kind of rare, I did not think I was going to find one honestly. Considered by many to be the best cast intake ever made for this engine. Of course this intake was developed for super stock racing in the mid 70s and never was intended to go on a street car. It has some nasty idle mixture problems due to the design of the upper plenum. One way to solve that issue is to not put fuel into the upper plenum, no way for it to come out of suspension and puddle in that instance. Of course that means eight injectors at the base of the intake, AKA EFI. And, since this is a street car of course it needs to have traction control. The EFI system does this through spark retard. So, now I have an EFI system that can do all the same spark control that the MSD box is capable of and traction control.

So, I will have a locked out distributor and the program for the box will be set for 0 everywhere. I guess my back up box does not need to be a programmable unit. I guess I just keep the programmable as a back up box.

[Flash68]

Assuming... you are running about 34 total, that would be the equivalent of running 24 "initial", 10 "mechanical" advance, and an extra 10 "start retard". Not bad. Good performance strategy, and easier to start.

I know some folks that will weld slots in the distributor to be able to limit the mechanical to only 10 so they can run more initial. This makes it pretty easy doesn't it.

Do you have a MAP? Brave enough to try some "vacuum" advance?

30 degrees total here. This is an SB2.2 headed engine. Highly efficient combustion chamber.

And I was just gonna run a locked out distributor with standard 6AL again like on my 377 before, but a friend talked about using one of these so I kinda decided to just try it. And you nailed the goal -- performance with easier start up.

No MAP and no bravery here. :lol:

That should work...but did they teach you the trick of starting the curve at 0* and then bringing it down to 20* at 200 RPM or so? This gives the engine advance for initial starting and reduces the chance of the engine kicking back (or something like that). That probably comes into play more with a higher compression, larger cam engine than mine, but I put it in mine anyway.

Let us know when you fire yours off and get to play with it a bit.

I should be firing it for first time in the car in the coming couple months.

Do you mean starter kickback? That is all the MSD tech mentioned being aware of. Here is his final comment on my baseline tune:

-------------
Yes, that's near the money. You could play with the cranking timing up to the point of starter kickback: 10-15 degrees, and your idle timing: 12 - 20 degrees for idle quality.

Eg: you may end up at 13 cranking so it starts well, and 18 idling.

[David Pozzi]

Here's my cheat sheet for PSIA to Vacuum conversion.
On this one, I was trying to leave 4 deg more advance available in software so I could try adding more later without having to re-set the distributor.
Another good trick is to set up the retard wire to a rocker switch so you can pull out 2 to 4 degrees if you ever get some bad/low octane gas and hear pinging.
I mounted the MSD in a place where I couldn't see the L.E.D. but found a fiber optic flashlight extension and used that to "pipe" the light to an area I could view it.

[SSLance]

Thanks David, you always bring great tech to any thread...

I love how people take what this box gives them and then try to figure out ways to trick it do even more than MSD suggests with them. All great ideas...

I wonder why my vacuum gauge and MAP sensor via the MSD screen vary so much from your cheat sheet? Mine very clearly shows 20" of vacuum corresponding with 7.00 PSI.

I currently have the vacuum gauge hooked to a timed port on the top front of the carb (same as goes to the choke pulloff) and the MAP sensor hooked to a manifold vacuum port at the back of the carb base next to the brake booster port. I guess I should rearrange one of both of them to really see what is going on... Where should I put each connection for the best info gathering source? This is a 1977 mechanical quadrajet with an electric choke.

I also noticed the other day that my heater controls aren't working properly so I'm going to cap those vacuum ports off for now as well as I might have a vacuum leak there that could be affecting things.

[SSLance]

So, a year later I am revisiting this topic. It was interesting to read back and see what I bailed on last year and attempting again this year with the new engine.

Last year I disconnected the MAP sensor and just ran the run retard graph in the box and it did pretty good all year. With the new engine, and new train of thought...I'm trying to program in a "boost retard" curve once again.

My engine builder concentrates on race engines and we dynoed this engine at 32* locked out 0-6500 RPM. I initially started with the run retard curve in the MSD that I ran last year that pulled 10* out at idle ramping up to all in at 2000 RPM. (22* at idle, 32* 2000+RPM) It ran pretty well but the idle was a bit unstable, most wouldn't have noticed it but while trying to tune the carb it was kind of giving me fits. I finally took the builder's advice and locked in 32* 0-6000 RPM. That cleaned the idle up a lot and I was able to get the carb dialed in nicely. It pulls about 17" of vacuum idling at 850 RPM with an AFR of 14, cruise AFRs are right around 15 and it gets a bit fat under WOT around 12-13 depending on what RPM I start the pull at. It runs very smooth, makes great power, and is safe if I get a bad tank of gas somewhere.

The only issue is it will ping if I lug it down under 2000 RPM in 3rd, 4th or 5th gear. I have to try to make it ping, under normal driving circumstances I can not hear any detonation.

So I have put the MAP sensor back in place and am working on using the Boost Retard function to try to pull some timing out under low vacuum situations.

Here are the dials at idle completely warmed up.

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/0313161405_zps46kxfkxy.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/0313161405_zps46kxfkxy.jpg.html)

It idles around 5.25 PSI, will drop to 3.5 PSI under full engine compression like downshifting coming to a stop and the highest I've seen is about 13.75 PSI at WOT in 3 or 4th gear. I created this Boost Retard graph and drove it.

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/GraphView%20Auto_zpsdcwbrb58.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/GraphView%20Auto_zpsdcwbrb58.jpg.html)

It's basically pulling 10* of timing out (32-10=22*) when vacuum drops under WOT pulls and stopped the pinging. The thing is, at WOT the PSI gains to 13.75 and the box stay at 5* retard (27*)...never letting the timing get back up to the 32*s it needs.

I'm thinking about pulling the right dot that is right now at 14.5 to the left and putting it at about 13, that way at just less than WOT the box would put the full timing amount back in, only retarding the timing between 10-13 PSI.

Am I thinking correctly here? I can't seem to find a way to pull timing out at WOT (zero vacuum) at low RPMS, but not pull the same timing out at WOT at higher RPMs where the timing is needed. So my hard head is thinking to just tell the box to pull the timing at just about WOT...

[68Cuda]

I think you have the right idea, you are just at the point where you are going to have to try it and just see what it does.

[SSLance]

I went back to the MSD forums to read around a bit more to make sure I was on the right track and I think half of the time the techs there that answer are completely backward as well.

Trying to compare vacuum advance with vacuum in inches to Boost Retard with instead of vacuum in inches, manifold pressure...makes one's head spin.

What I need to do is decide if it's worth the effort to lock the distributor in at say 45* crank timing and plot both run retard and boost retard graphs to pull enough timing out with either or both to get the timing in perfect spot for all scenarios? I could probably end up with total timing in the 40+* range at idle and cruise RPMS and use the MAP sensor\boost retard to pull timing out under a load and WOT.

Really, for my use...it runs pretty dang good like it is as long as I don't dog it down in higher gears and apply massive amounts of throttle. Seems like it might be safer for me to stay the course instead of trying to reinvent the wheel...

[68Cuda]

Trying to compare vacuum advance with vacuum in inches to Boost Retard with instead of vacuum in inches, manifold pressure...makes one's head spin.

What I need to do is decide if it's worth the effort to lock the distributor in at say 45* crank timing and plot both run retard and boost retard graphs to pull enough timing out with either or both to get the timing in perfect spot for all scenarios? I could probably end up with total timing in the 40+* range at idle and cruise RPMS and use the MAP sensor\boost retard to pull timing out under a load and WOT.


Yeah - kind of confusing... theoretically atmosphere is 14.7", so anything under that is a vacuum. It is just whatever your reference is. You just have to unplug to figure out what your atmospheric pressure is. The crazy part is the fact that your scale is flipped. If 14.7 is atmosphere, that is what you think of as 0 vacuum. The numbers don't really matter in reality, it is all just a reference. Sounds like your "0" is WOT at 13.75, so be it.

OK... two different camps on this. Manifold vacuum and port. Based on the problem you are describing let's try port vacuum, this may give you the effect you want. With port vacuum you should only see vacuum at partial throttle. This will eliminate the extra advance at idle and at full throttle and stabilize the rpm at idle. The "port" you want to plug into should be above the throttle blades and should read 0 vacuum at idle when measured with a vacuum gauge.

I think you are still thinking of the vacuum curve backwards.

OK, two different curves! One for RPM (aka centrifugal advance) and one for the "boost" retard (aka vacuum advance). For the RPM curve let's say you want to go from 8 to 32, all in by 2800 rpm. And, for the "boost" you want 10 degrees advance max on the ported.

Your base timing with no curves would be 8+24+10= 42 degrees (pretty close to the 45 you stated). Remember that everything on the MSD is backwards, it is all retard. So, the RPM curve would start at 24 degrees retard. If your idle is 900, then maybe you start adding timing back in above 1200. Your "curve" would be 24 degrees retard from 0 rpm to 1200, then progress to 0 degrees retard at 2800. The effect is timing would be 8 degrees at idle and at 1200, it would then increase gradually to 32 degrees at 2800 rpm. This is my example... set it for power at what works best for you! I used "8" as my idle timing just as an example.

OK, for your boost curve (connected to port vacuum), if 13.75 is WOT, then you want 10 degrees retard at WOT to give you 32 total above 2800. So, left to right you put 0 retard to about 4 then increase your retard to the full 10 by about 12, leave it at 10 total all the way to the end of the graph on the right. At idle, or with the port vacuum line unplugged even, the 10 degrees retard will be pulled out and the timing should be whatever you want it to be, it should not jump around.

So add these together... say you are running 2800 rpm with the throttle barely cracked and a little downhill, you could then be running as much as 42 degrees advance. No problem under light / no load. As you tip into the throttle and start to load the engine the vacuum will drop and your timing will move to 32. Cruising speeds around 2000 (half way between 1200 and 2800) you would be running 18 advance due to RPM, and if there is no load, as much as an additional 10 which will help mileage.

Attached charts make sense? Boost:

[68Cuda]

RPM "advance":

[SSLance]

Thanks Michael, I really appreciate the time you have taken to help with this. You are one of the few I've found that gets how these boxes work and are willing to jump through the hoops to trick them into doing more.

I like your curves and understand what's going on much better...I think I'll try them to see how they work.

Today I pulled the boost retard back to below 13.75 psi and it worked as far as getting 32* at WOT again, and it helped with the ping...but I could still make it ping at cruise at highway speeds if I tried. I could live with it like this but I'm curious just how much having the extra timing in at cruise and at idle would help.

The using of a port vacuum is also an interesting thought. I actually talked about that being an option with my friend that built my carb last night.

I need to procure my friends timing light once again and charge my laptop up...then see how it works.

[SSLance]

Just to make sure I'm clear, one question. If I set the distributor at 42* with no curves, then put the two curves in you showed above...my timing at idle would be 18* correct? Run retard pulling 24* out at 900 (42-24=18).

If I wanted more timing at idle, I'd do your curves above except raise the run retard at idle to say 10* (42-10=32*). The question then would be what to do with the run retard curve from 1000-2500 RPM?

The Boost Retard curve you posted would pull 10* out when vacuum drops, how much more would we need the Run Retard to pull out at cruise to keep it from pinging is the million dollar question...

Cruise is generally between 1300-1800 RPM just FYI.

[SSLance]

I've been tinkering and picking brains a bit more and I think I've come up with a plan. Please take a look at this and make sure my thinking is straight before I implement.

Distributor is locked out at 45* advance,

Run Retard is set as below,
Idle timing 0-600 RPM -8* (37* actual)
1000-2000 RPM -18* (27* actual)
2800+ RPM -13* (32* actual)

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/MSD%20Run%20Retard%201_zpssm0zdqen.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/MSD%20Run%20Retard%201_zpssm0zdqen.jpg.html)


Boost Retard is set as below

Full vacuum
17"-12.4" at idle or cruise -0* (37* idle, 27* 1000-2000 RPM)
9 psi (12.2" vacuum) -1* (26* actual 1000-2000 RPM)
10 psi (10.1" vacuum) -3.2* (23.8* actual 1000-2000 RPM)
11 psi (8.1" vacuum) -5.7* (21.3* actual 1000-2000 RPM)
12 psi (6.1" vacuum) -8.4* (18.6* actual 1000-2000 RPM) (23.6* 2800+ RPM)
13 psi (4" vacuum) -10.9* (16.1* actual 1000-2000 RPM) (21.1* 2800+ RPM)
13.5 psi (3" vacuum, WOT) -12* (15* actual 1000-2000 RPM) (20* 2800+ RPM)

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/MSD%20Boost%20Retard%201_zpsenblntrp.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/MSD%20Boost%20Retard%201_zpsenblntrp.jpg.html)


On the idle side, the only thing I can think of is I might need to adjust the Run retard between 800 and 1000 so it remains at a steady state there as my idle fluctuates in that range and a moving timing mark will probably make it fluctuate more.

Maybe something more like this. Is that too sharp of a transition between 1000 and 1200 RPM?

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/Run%20Retard%202_zpsmaeazv0b.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/Run%20Retard%202_zpsmaeazv0b.jpg.html)

On the WOT side, it appears that I need to make the Run Retard more like this so I can see full 32* timing 2800+ RPM

http://img.photobucket.com/albums/v362/LSVLance/1985%20Monte%20Carlo%20SS/Run%20Retard%203.jpg_zpsx9u3pa12.jpg (http://smg.photobucket.com/user/LSVLance/media/1985%20Monte%20Carlo%20SS/Run%20Retard%203.jpg_zpsx9u3pa12.jpg.html)

12 psi (6.1" vacuum) -8.4* (18.6* actual 1000-2000 RPM) (33.6* 2800+ RPM)
13 psi (4" vacuum) -10.9* (16.1* actual 1000-2000 RPM) (31.1* 2800+ RPM)
13.5 psi (3" vacuum, WOT) -12* (15* actual 1000-2000 RPM) (30* 2800+ RPM)


I'm not sure how to get those last three lines closer to the desired 32* timing at WOT past 2800 RPM? The variable is vacuum inches, not RPM...so it's almost back to my other method of stopping the Boost Retard right before WOT.

[68Cuda]

Lance, I would leave the RPM based curve flat in the idle area and just do a straight ramp from 1500 to 3000. Why do you want so much timing at idle? It does not do much. Factory these cars usually ran 10 or less at idle with the vacuum advance unplugged.

As far as the pinging, I would tweak one curve or the other so it gives you a little bit less timing. Your boost curve might be a little too aggressive, try pulling it a little to the left. For example set it to the full 12 degrees from 10psi to 15psi and start the ramp down a little earlier, maybe 6psi instead of 8. In other words, at 6psi it would be 0 and then ramp down to 12 degrees by 10 psi. Try that first.

There are so many variables in the way the engine is built, load, the quench, the camshaft, air density (temperature, pressure, humidity) that no one answer will work you just have to tweak it until you are happy with it. On my 440 when I put the mechanical advance MSD distributor I set it by ear and drove it. Later in the week we put a light on it and it measured 35 total. I have been running big block Mopars since the 80s, I know what they are supposed to sound like...