MSD programmable thread

[cole930]

Ok !!!! I want to start with a disclaimer here. The attached pic. happens to be a GM distributor and is being used for reference purposes only.

As you can see the centrifugal advance plate, weights, and springs sit at the top of the distributor and are connected, by the springs, to a shaft that runs through the center of the distributor to the drive gear. Below the centrifugal advance you can see the reluctor wheel which is fixed to the distributor shaft.





Below the reluctor wheel you can see the silver advance plate that rotates independent of the distributor shaft. The vacuum canister arm is attached to the advance plate with a pin and the centrifugal weights are also attached to the advance plate by way of pins the fit into curved slots in the advance plate. The timing is advanced by the centrifugal force caused by higher rpm overcoming the spring force on the weights which move the advance plate by way of the
pins of the weights moving in the curved slots of the advance plate. As RPM is reduced the weight springs retract the weights and the advance plate retards. The advance plate can also be advances or retarded via the vacuum advance canister as vacuum acts upon the diaphragm in the canister. Boost retard is achieved by the absence of vacuum on the vacuum canister.

This is a rough explanation but you get the idea.

Cole

[cole930]

Keith,

You could remove teeth but only if the number of teeth on the wheel allowed the correct 120* spacing.

MSD makes magnetic wheels but all are for V8's. They make one universal wheel thet does 4-6-8-10-12 cyl. by placing magnets in the correct places but the
wheel is 7 3/4 dia. and would not fit.

Cole

[911st]

I understand about the vac advance. Again, if it is not receiving any manifold vac/boost, it dose not function but the mechanical advance dose and we program around it making it part of the total advance.

Or we can just lock down both the vac and mechanical advance.



How about contacting the company that makes the pulley's and have them make a custom one to spec?

[cole930]

Keith,

With the 6AL-2 we can actually use it 1 of 4 ways. You can set the timing map function and boost map function to a "0" or default condition and then the unit functions just like a regular MSD 6AL. You can set the retard map function to "0" or default , lock the distributor at a set total timing and just program the timing map. You can set the timing map to "0" or default and run just the boost retard map. You can lock the distributor at a set total timing and then map both the timing and boost retard maps.

You can not program a functioning timing map unless the distributor is locked down at a set total timing setting. To lock out the distributor you must disable or remove the vacuum advance canister and plug the manifold port. Then you need to remove the centrifigual advance weights and springs. You then rotate the advance plate to the advance limit and lock it to the base plate. You can pin it, drill and screw it, wedge it, or tywrap it. It would be a good practice to set and mark your total advance before removing and locking out the distributor. This way once you have completed the lock out procedure you can reinstall the distribtor and drop in back in at the previously marked total advance position.

Cole

[911st]

Cole,

I 100% understand what you are saying.

However, think of it as having the machanical and MSD advance working in parrelel and with this using the MSD boost retard.

With the MSD base map you can increase, decrease, extend, reduce, or shape the mechanical advance curve.

Kind of the same idea as the Unichip or other piggy back computors that modify the stock ECU out put instead of replacing it except we can only delay the timing event with MSD.


As we learned from the Vac-Retard function, if you can delay timing, you can creat advance by taking the delay or retard away.

Thus, if mechanical advance runs 0 to 15 deg over 2000rpm we could set the MSD base map to go from 0 to -15 on top of that and we could if we wanted, end up canceling out the mechanical advance.

Or we can go the other way. We could stack them so on top of the 0 to 15 mechanical advance we could with the MSD base map by taking retard away go from -25 to 0. That would give us a combined advance of 15 + 25 or 40 deg of advance.

Your postition is just like the one I took about adding Boost Retard on top of the stock pot boost retard system. I thought we needed to disable the factory boost retard at the pot and just use the MSD Boost retard box. However, several just added the MSD retard on top of the factory retard when they wanted to advance the timing at the distribuitor for better low end.

Same principle but we would be running the MSD Base map over the mechanical advance instead of the MSD boost retard over the retard at the pot.

=====

Another possability might be to kill the factory boost retard, lock down the mechanical advance and just keep the pot's Vac-Retard function in place.

This would let us set idle at -5, have vac retard go away with acceleration for instant -15 off idle, use the MSD base map to re-build our advance curve, and lastly use the MSD boost retard to finish things off.

If we get 9 deg from vac retard plus 25 from the MSD plus static timing of say -5 deg -- we could go up to about -42 deg advance at speed and light load.

With out the vac-advance, if we start static timming at -5 deg the most timing at cruse will be -30. Liviable but not an improvement at cruse. Remember the C2 Turbo runs about -40 deg at cruse. That is the main improvement I was shooting for by using the systems on top of each other.

My appoligies if I can not present it clearly or belabor the point. I just think there are possabilities here.

The best.

[911st]

Cole,

In the picture above of the dist, the vac pot looks like it might be a dummy-pot that effetively locks down the vac advance function.

Or, the advance rod is hidden under the advance plate. Still this presents us with a way to lock down the vac advance. Just put a screw through the arm at the plate where we atach the pot to the dist.

To kill the mechanical advance we could make a hard link to replace the spring but I think I like your idea of putting a screw throught one weight into the plate.

[cole930]

keith,

I think the distributor in the picture is a MSD distributor for a Chevy. It is already locked out and that is why the VA is disabled.

MSD says you cannot piggy back the centrifugal and/ or VA with the 6AL-2.
You have to disable the VA and lock out the centrifigual. You can set the total timing at 40* if you want but you have to remember you have 25* of retard to work with so at 40* total that would set your initial timing at 15*.

You can call MSD support and talk to the techs. they really know their stuff and are always willing to help. 915-855-7123



Cole

[911st]

Cole,

How much inital advance do you think a 930 can live with at idle?

I do prefer using the MSD's programing but hate to go to all that work and leave the ideal cruse timing on the table.

If we can run -10 at idle, that could get us to -35 on cruse. Much better than -26.

[cole930]

Keith,

I'm quite sure you could use 10* and I'd like to see 12*- 14*. I've got some 930 dyno timing test charts coming and they should give us some real life information.

Cole

[9dreizig]

Hey Keith, you keep mentioning the advantages of cruise advance.. Let's assume a perfectly tuned stock 930 gets 20 mpg. what kind of mileage do you think we can get cranking up the advance to the 35 range ?? Since I love to cruise long distances in mine this is of interest to me.

[cole930]

Guys,

While we're kicking things around here we need to know some of the facts that effect the engine while fooling with timing. And first it should be noted we need to tell anyone interested in max performance timing on a 930 there are several musts when doing this.

Must:

The static compression ratio should not exceed 8:1 without substantial
engine component modifications to Handel the increased pressure under
boost.

A larger inter cooler is a must in order to lower inlet temp.

The exhaust system should be as free flow as possible to get rid of excessive
heat as efficiently as possible.

Only premium fuel should be used.

One heat range cooler that factory recommended plugs should be installed.

The fuel system must be able to maintain 12.3 - 11.7 afr's under full boost at
red line.


Some timing facts:

Excessive initial timing will cause low end detonation if anything less than
premium fuel is used

At 4000 rpm and higher advance above 26* will help cool exhaust temps.

At 4000 rpm excessive retard below 26* will cause increased head temps.


Interesting note:

Chris (356 - 930 ) Ran a stock 3.3 930 with no inter cooler but water alcohol
spray. His initial advance was 22* and his total advance
was 40* and had no detonation or mechanical issues.

Cole

[911st]

I might add I do not think his on boost was -40. He pulled it back with his MSD Boost Retard system.

Ideal timing as to power is probably going to be found on a dyno and will vary depending on fuel, temp, AFR's and depending on one's build. We should at least find out how much timing we can take at TQ peak on a dyno which is where we are most sensitive to timing. A mistake at WOT on boost has the bigest potental for dammage.

At low load a motor can use more timing than under load. A motor might run at idle at a very advanced timing but under load might have and issue. I think -17 by 1500 at WOT is ok. On cruse I have heard into the 40's if you have a system that senses load well and can pull back timing. Early 911's ran WOT in the 36 deg range so I think that is a good target for our MSD base curve with boost pulling back from there. We have info from at leaset one pro tuner that he starts at about -20 at .8 bar and -19 at 1 bar WOT and tunes from there.

On top of that, a lean AFR burns slower and a rich burns faster. A rich also burns cooler. Thus, getting one's AFR diled in first is a good idea.

How much better fuel economy, I do not know. If going from -26 to -40 can get 5-10% more power out of the same fuel, that could make for 5-10% better economy.

Proper AFR and timing over fat AFR & -26 timing is going to be a big differance.



I am wondering if Exhaust Gas Temp can be used to dial in cruse timing and even WOT timing. I am not sure but as noted, late timing increaes how much fuel is still burning in the exhaust, as was get closer to an ideal, temps will get cooler. Not sure if it peaks again with detonation.





With higher temp's potental for detonation increases. As such EFI ignitions like on the 91 turbo and all the EIF motors pull timing back with heat. The 91-94 CIS Turbo with motronic igntition can adjust timing + to - 3 deg.

[9dreizig]

Hey guys here's an update. I've got the unit running with boost and rpm feedback. Going to try to program it this weekend. I'll keep you informed
T

[cole930]

Todder,

I thought you were dead or something. Glad to see your still kicking. Cool news on the 6AL-2 can't wait to hear what you have to say.

Just finished sticking # 4 piston and cylinder back in that's the last one. All the new studs are in and I'm lubing the o rings on the new return tubes now. After I got the last broken stud out I decided to pull all the pistons and cylinders to make sure everything was fine, as long as I had it down that far. Everything looks real good. Hope to start putting heads back on this weekend.

Good luck with the programming.

Cole

[9dreizig]

Sorry with the move last weekend and unpacking this weekend, it's been tough. I have been working on getting the A/C installed as well. Ripped out all those old temp controls and switches so now have two.. one for the compressor and one for the fan. So it's either on full blast or off. Also started replacing the old fuse panel with a modern one. Got 4 positions done. Will finish the rest after the long road trip..
Oh and replaced the torn boot on one CV joint ( a lovely job)
T

[j911brick]

Did you guys ever get this issue sorted out? BTW: it doesn't matter where you lock the centrifugal advance plate.

Does anybody know if I can use a crank trigger from a 3.2?

TIA
james

[cole930]

James,

You have to remember I'm old and the chemo has destroyed many of the inadequate number of brain cells I had to begin with. It's been 6 months since I posted and I presently have my old head around WMI and suspension development issues.

I want to tell you no but it is going to be dependent on what the output signal and resolution of the 3.2 crank trigger is. If you called the MSD Tech line and ask for Vic he can give you all the correct info. Many crank trigger wheels are a 32 count and the MSD wants to see only 6 like the old flywheel magentic pick up ignitions.
Cole

[j911brick]

I called MSD more than once and they didn't know. Since I want t use the stock hall sensor I think I have to add two more screws to the flywheel.


james