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AEM EPM on honda B18C


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Hi guys

friend have ITR with B18C turbo with AEM EPM

RPM graph on log looks bad, its not smooth, like map for example


is there a way to fix that?

we changed 2 EPM same thing

EPM is hall/optical sensor http://www.aemelectronics.com/products/ignition-components/engine-position-module-epm



is there anyone with tuned B18C?



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no trigger errors at all

car runs fine and smooth

but logs look horrible, oh yes, and rpm gauge is jumpy


i did try with filtering from 1 lowest to 4 highest, same thing :(


this is log from today with level 4 filter



wiring on car is completely new, because we had same problem with honda pnp and stock ecu wiring.

This is wire in ecu not pnp, and new install, so i guess it is not hardware related.











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You could try spinning the EPM in a lathe or drill and see if you get a clean RPM.

If you do then it can be an indicator that the drive of it is actually speeding up and slowing down. Such as you might get with a slack cam belt or play in the drive.

Next step will be checking the signals out of the EPM with a scope.


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  • 2 months later...
  • 2 months later...

Unfortunately not yet,

owner change engine to B18c with dartons (2.1 liter), turbo, head retainers etc etc (and that took 4 months :) )

but problem remains, and he is driving car like that now.


he had no time to test AEM with drill but we will test it, i will let you guys know when we do it.

For now we are suspecting on AEM EPM, and thinking to setup external trigger wheel on crank.





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You got "slop" in the system between the crank itself (what we want to meassure the position of) and the actual trigger system (that tells the ecu where it THINKS the crank is at). This slop is what the ragged rpm graph tells a story about.. Its good enough to use as cam signal as long as you can make sure it fires between two crank teeth but not good for CRANK measuring.

Edited by Steve
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