newbie needs map help please

philbert · Post by **philbert** » Fri Jun 13, 2008 7:53 pm

Hi all at long last ive took the plunge and ordered my mega jolt light set up

now for the first of many questions!
the engine builder has supplied an advance curve which is correct for my engine spec.
im struggling to understand how to plot it as a 10 x 10 map.
can someone help please?

alfa boxer · Post by **alfa boxer** » Fri Jun 13, 2008 8:13 pm

Can you post the details of your ignition curve that you were given with the engine.that would help, are you going for map or tps?

philbert · Post by **philbert** » Fri Jun 13, 2008 9:04 pm

jeez that was quick!
ok i'm going map.
the list of figures i got are as follows

crank rpm - (advance) 400(4) 800(6) 1200(12) 1600(14) 2000(22) 2400(26) 2800 (29) 3200(31) 3600(34) 4000(38) above 4000(38)

static timing is 6deg BTDC

thanks
philbert

philbert · Post by **philbert** » Fri Jun 13, 2008 9:06 pm

for some unkown reason the last 2 advance figures have become smileys the figure should be 38

cng1 · Post by **cng1** » Sun Jun 15, 2008 9:25 am

One thing to note is that the advance figures for the bottom end of the scale are only appropriate to a dizzy on which you can't run as much advance as you need to at light throttle/low rpm as if you did you'd be running way too much at the other end of the scale.

At idle you may well only need 4-6 degrees at your target idle point but either side of that you will want quite a lot more.

philbert · Post by **philbert** » Wed Jun 18, 2008 7:19 pm

thanks for the help so far folks.
still dont understand how to build a map from my figures.
can someone point me in the right direction please.
is there anything i can read up on that might help me?

Post by **brentp** » Thu Jun 19, 2008 4:29 am

Philbert,

Your example figures do not include the vacuum advance from your original distributor setup. Do you have this information? The vacuum advance figures translate to manifold absolute pressure (MAP) in KiloPascals (KPa), along the load axis of the MJLJ configuration software.

If you imagine how the original distributor works, the vacuum advance mechanism further adjusts the advance on top of the RPM advance curve. This effect is emulated in the 2D ignition map of the MJLJ.

The RPM data you listed maps to the RPM axis in the configuration software, so it should be pretty easy to plug in this data along the RPM axis- spread the RPMs across the 10 RPM bins in the software.

But what to put in for the advance values? The figures you listed don't account for vacuum advance. Since it's a 2D table with RPM along one axis and load across the other, the values you enter represent the RPM advance + any adjustment based on load (i.e. the vacuum advance)

Once you find the vacuum advance figures for your engine you can plug those in along the load axis and calculate each ignition advance cell as RPM advance + load advance- mapping this into each cell of the 2d table.

Clear as mud?

philbert · Post by **philbert** » Thu Jun 19, 2008 8:35 am

brentp wrote: Clear as mud?

thanks Brent that helps me understand better what i need to do

philbert · Post by **philbert** » Thu Jun 19, 2008 11:00 am

cng1 wrote:One thing to note is that the advance figures for the bottom end of the scale are only appropriate to a dizzy on which you can't run as much advance as you need to at light throttle/low rpm as if you did you'd be running way too much at the other end of the scale.

At idle you may well only need 4-6 degrees at your target idle point but either side of that you will want quite a lot more.

cng1 thanks for that.
i dont know what the figures would be of idle.
i have all the figures for a basic map now so will work that out and try it.
once the motor is up and running well i'll try more advance of off idle.

cheers
philbert

Autosport Labs

newbie needs map help please

newbie needs map help please

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