Hello:
Hoping someone can advise. I have just installed MegaJolt JR Lite on my 1995 range rover with a 4.2V8. The car is running but when I put a timing light on it I noticed that instead of a smooth run up of advance I am getting 'jumps'.
For example, my timing map is currently set to run at 9 degrees advance at 700 rpm and then around 22 degrees advance at 1000 rpm (varies by a few degrees depending on the load). The timing is rock steady at 9 degrees at idle (about 725 rpm) but if the rpms are increased by as little as 50rpm the timing jumps to the 22 degrees as measured by my timing light - am i doing something wrong, or is this the way it is supposed to be?
Thanks for any and all help
Rob
no interpolation between RPM bins
Moderators: JeffC, rdoherty, stieg, brentp
Hi Rob,
The Megajolt does indeed interpolate between Bins-only very old firmware from V2 controllers did we not have that feature.
In your case, with only 300 RPM spread between 700 and 1000 RPM and a 13 degree change between that, the firmware can quickly jump up the advance, especially under variable conditions like on a running engine. Also worth noting the Megajolt measures engine speed in 100 RPM increments.
Another thing is to make sure the adjacent load bins aren't affecting ignition advance as vacuum changes.
With our test-bench engine simulator we can precisely control RPM; Here's what we observe replicating your scenario:
700-799 RPM: 9 degrees
800-899 RPM: 13 degrees
900-999 RPM: 17 degrees
1000 RPM: 22 degrees
this was with the load bin locked in exactly at 102KPa
Hope this helps,
The Megajolt does indeed interpolate between Bins-only very old firmware from V2 controllers did we not have that feature.
In your case, with only 300 RPM spread between 700 and 1000 RPM and a 13 degree change between that, the firmware can quickly jump up the advance, especially under variable conditions like on a running engine. Also worth noting the Megajolt measures engine speed in 100 RPM increments.
Another thing is to make sure the adjacent load bins aren't affecting ignition advance as vacuum changes.
With our test-bench engine simulator we can precisely control RPM; Here's what we observe replicating your scenario:
700-799 RPM: 9 degrees
800-899 RPM: 13 degrees
900-999 RPM: 17 degrees
1000 RPM: 22 degrees
this was with the load bin locked in exactly at 102KPa
Hope this helps,
Hello:
Thanks very much for the reply, and you were absolutely right - the Megajolt is interpolating between bins -I was just having a bit of a stupid moment! Have since modified my map to make the change a little less steep. Unfortunately I have to get the truck through a smog test. They don't look under the hood so I'm okay with the change, but I gotta get the stuff coming out of the tailpipe on target. The first time I took it through it failed due to the NOx levels being too high - I think I was overly aggressive with the advance - have since scaled it back quite a bit to try and mimic the original distributor as best I can. I don't have many/any details on the original distributor curve so it's a bit of a guessing game!
Must say though that I am very happy with the Megajolt so far! The truck is running better than it has in a long time.
Rob
Thanks very much for the reply, and you were absolutely right - the Megajolt is interpolating between bins -I was just having a bit of a stupid moment! Have since modified my map to make the change a little less steep. Unfortunately I have to get the truck through a smog test. They don't look under the hood so I'm okay with the change, but I gotta get the stuff coming out of the tailpipe on target. The first time I took it through it failed due to the NOx levels being too high - I think I was overly aggressive with the advance - have since scaled it back quite a bit to try and mimic the original distributor as best I can. I don't have many/any details on the original distributor curve so it's a bit of a guessing game!
Must say though that I am very happy with the Megajolt so far! The truck is running better than it has in a long time.
Rob