Ok, I checked with MSD.

Here is what I got. The digital boxes that use an external Map Sensor work as we have described. You need to get the reference by doing key on, engine off figure out what your amotspheric pressure is for your temp and location, for me it is 14.5. Boost is above that. I tired to keep it as simple as possible.

Example:

My boost referance with key on and motor NOT running is 14.50

10 lbs of boost will in reality read 24.50PSI inside the MSD Box.

And I would start to retard timing @ 14.50 psi (O boost/vac). If you want to start pulling at 5 lbs of boost then you would start a curve at 19.50 on the MSD Box.

 

Thanks for all the advice Tim...

 

The internal ambient sensor is completely separate from the MAP system. The only thing it does is measure ambient. Without calling tech support you would not know it is there. The MAP circuit is used to measure engine boost.

I guess testing it is the only way I will know for sure. I atually believe it will be like Tim and Blown have said. I have a small pump that is for blowing up ballons that will put about 10 Lbs in the line. I use it to set the activation point of my water methanol. I'll build a test curve that pulls out about 10 degrees at 2 PSI on the graph and see if it moves at all.

Thanks for all the help and teh patience with the noob! 8)

 

So, is it safe to say that the 6530 is NOT a digital box so it DOES work like they told me it would?

Blown385 has a digital 7 so that would make sense that it works that way for him too.

I'll test mine tonight and let everyone know how it works on the 6AL-2 (6530)

 

I find it interesting that they mentioned temp , because mine reads 14.5 now , and it read 14.25 all last summer .

I always thought it was just lower atmospheric pressure and humidity we see during the summer here in Florida .

 

2psia is about 22" of vacuum .

If you set it to pull 10º at 2psia it should pull the timing as soon as the motor starts without adding air to the MAP since it will already be over 2psia . Unless you have some serious vac at idle !

Set it to pull 10º at 24.5psia . ( to test )

 

Remember , this is why they say you can build in a " vacuum advance " with these boxes .

Your not advancing the timing , your pulling it from a higher starting point . Anywhere you want under 14.5psia or ..........vacuum .

 

Well, I am in the garage right now and the 6530 works just like Tim and Blown explained. I called a third tech at MSD and asked "is zero on the X axis zero PSI" and he said yes too! I pressed him and technically hi answer was right, but wouldn't common sense say that he should add that it is vacuum? and that I need to do the key on, engine off to get my reference point??? None of the three ever mentioned that and there is no documentation.

Anyway, my absolute pressure is only 7.5!? I am at 900 ft. actual elevation and it is a nice cool day but that seems low to me.

Also, I guess you have to re-do your curves based on changing weather? That seems a bit crazy.

Anyway, thank guys for helping me get to the correct answer. Looking forward to trying this thing out at the track.

 

Are you using a 3bar sensor ?

If so , you might have to go in the menu and change to 3bar from 2bar which is the default setting .

Not sure if thats it , just all I can think of off hand .

 

If will not vary enough to make a difference .

 

MAP stands for Manifold Absolute Pressure. It reads PSIA or absolute pressure vs a gauge tha reads PSIG or gauge pressure. It is hard for me sometimes since my vac/boost gauge reads inches of mercury below 0 gauge pressure. Comparing retard chart vs what I see on the gauge can get confusing. 0 on the chart is actually -29.92" of vacuum on a gauge. The 9.5psia on blown385's chart is about 10" of vacuum. 1psi = about 2" of mercury. 9.5psia x 2 = 19" To convert it to gauge pressure you add that to 0 absolute or 29.92. -29.92 + 19 = -10.92. Your local pressure will change it slightly which for blown385 is 14.25psia, last summer. If his local pressure was 14.25 it would move that -10.92 down to -9.92. You get good at it after a while.

To get vacuum advance effect you add timing at the distributer, 42* in my case, and when vacuum is higher than 9" it has no retard on the boost chart. At 9" it starts pulling timing to get it to 35* by 0psig.

I hope it helps Greg O.

 

Greg it sounds like you have a 2bar sensor and the box thinks it is a 1 bar, which is default.

 

thats as easy as it gets to explane..

 

I thought the same thing , but I was thinking digi7 which is 2bar default .

But I just checked mine . Even with my 3bar , I can change the setting to 1bar or 2bar with the same sensor and it will still read 14.5 as zero . It just moves the numbers farther out on the graph from 15pisi on the 1bar to 30psia on the 2bar to 45psia on the 3bar .

 

Did you save it to PC? It won't change the chart until you save.

 

yea when I save it to PC it just puts the higher total like 45psia for the 3bar and 30psia for the 2bar .

It doesnt change 14.5 being zero .


Will yours change zero to 7.5 like Gregs did ?

 

Mine does not show up unless I am connected and key on. It acts exactly like Gregs when set at 1b with a 2b map. It reads 2.5v which is half the scale. On a 2b sensor that equals 14.75. On a 1b it is half the scale at 7.5.

 

Thanks everyone for all the help!! I guess I just got off track on this thing because it did not come with any printed instruction. I actually do read instructions for anything I get!

Anyway, I did change the default to 2 bar and my red line DID reset to 14. I never tried going back the other way to see if it went back to 7.5.

 

Cool , I thought that might be his problem .



On a side note . I switched to a street tune when leaving the track the other day and it must have been an old file , when I was using the 2bar . I pulled out on the street and got on it . I immediately noticed I had no " crutch light " indicating the PVs weren't open . Since I use the built in boost switch on the Digi7 to control the crutch , it was not reading the 15.5psia setting when using the 3bar sensor on the 2bar setting .

Crutch light saved the day ! Not because it was lean , but it told me there was SOMETHING wrong . Made me look into why it didnt come one and found it was the sensor setting , meaning it wasnt going to pull the timing . ON PUMP GAS !

If I didnt have the light , it would have went lean and full timing .

 

Great news !

If you haven't got the instructions yet :

http://www.msdignition.com/instructions/Products/Ignitions/6530_instructions.pdf?terms=6530