RPM reading wrong

jacmifish · Post by **jacmifish** » Mon May 13, 2013 12:25 am

Hi,

I'm running the megajolt lite jr. and had started to tune the system when I noticed the RPM readout on the gauge cluster tach and the megajolt digital readout were different, e.g. the computer would say 2500rpm and the tach on the gauge cluster would say 1700rpm. I know the gauge cluster readout was defiantly more correct.

Since the rpm reading on the megajolt system would read a much higher rpm it would engage the wrong columns on the ignition map.

What I find strange is that I'm sending the output tach signal from the megajolt to the tachometer and my Powerjection III system, so why would that be correct and not the other?

By the way I do have it set to read out the correct number of cylinders. =P

Car is a Plymouth Duster with a Slant six

Any help would be awesome thanks! =)

jacmifish · Post by **jacmifish** » Wed May 15, 2013 6:23 pm

Anybody?

Post by **brentp** » Sat May 18, 2013 6:56 am

Hello,

You will need to double check the number of cylinders set in Megajolt. Note, this is a separate process from reading the ignition map.

1. connect megajolt to the computer
2. read the engine configuration
3. make sure 6 cylinders is selected
4. write it back to the unit
5. power cycle the megajolt and read it back again to make sure it says 6 cylinders.

jacmifish · Post by **jacmifish** » Sat May 18, 2013 2:13 pm

I have previously followed those steps and it confirmed that it was configured with 6 cylinders. I have made it "re read" the controller after flashing the config and it is still the same.

Post by **brentp** » Tue May 21, 2013 1:19 am

Out of curiosity, what kind of RPM readings do you see in the megajolt software if you change the engine cylinder count to 4, 6 or 8 cylinders?

jacmifish · Post by **jacmifish** » Thu May 23, 2013 12:23 am

Hey Brent. I will give that a shot near this weekend, thanks.

jacmifish · Post by **jacmifish** » Sat May 25, 2013 7:47 pm

Hello again.
Before changing around the cylinder settings I decided to test a few things in the system. One things I thought about first was maybe that I wired up the tach output incorrectly on the megajolt because I have it running to my fuel ecu and my tachometer. I removed the tachometer feed and the RPM seems to be normal now will cranking (I think). Something I'm not sure about is that when I cranking the motor and watching the megajolt rpm readout it dosen't register until the motor fires, is that normal?
Testing resistance for the coil pack on the connector getting .9ohms on each coil, then between the coil towers on the same coil the resistance were as follows: coilA 13.88Kohm, coilB 13.69Kohm, coilC 13.83Kohm. I'm not to familiar with that but it seems normal from what I have read. A couple of the plug wires seem to have pretty high resistance with the highest being 6Kohm/ft. I plan to buy some wires soon and see for a difference.

jacmifish · Post by **jacmifish** » Mon May 27, 2013 3:46 pm

Okay so I resolved the issue. The problem was I was following an incorrect diagram of the coil block order

so two of the pairs were switched

Everything seems to function now and the only odd things is when it is at idle the rpms seem to flutter a bit but they die away.

Also I checked with using my tachometer and ecu unit at the same time from the megajolt and its seems to work fine =)

Here is my video of it on start up
http://www.youtube.com/watch?v=mHFyjEBI ... e=youtu.be

Post by **brentp** » Tue May 28, 2013 5:35 pm

Hi! glad you got things sorted out!