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EFI Tuning Fundamentals

Relevant Module: EFI Components > Trigger Inputs

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Discussion and questions related to the course EFI Tuning Fundamentals

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What trigger wheel is preferred for after market ecu's with a rev range higher than oem.

36-2 or 26-2?

Am i right in thinking the 26-2 is preferred as it has a lesser chance of missing a tooth at high engine speed.

36-2 would be more common. I've never seen a 26-2 wheel. Who would want to make teeth 12.85 degrees each, when you could use 10.00 degrees. I think several motorcycle engines (13000 rpm), use 24-1, where the teeth are 15 degrees apart.

I have access to a couple of hundred Trigger wheel patterns that are programmed into out current ECU ranges, and not a single one of them has a 26 tooth trigger wheel. There are a number of 24 tooth variant, either -1 or -2, as well as some +1 and +2 variants. The + variants use an extra tooth that is spaced outside of the equidistant spacing of the regular trigger teeth.

Unless you have a ECU that will allow for you to write a custom trigger mode, it may be difficult to find an ECU that will run using that pattern.

As the others said 24 and 36 are common tooth counts, 26 is not.

What ECU are you using, which engine, and what max RPM did you have in mind?

ok i understand, obviously the 26-2 is a typo.

What im asking is if there is any benefit to changing trigger wheels for what ever reason or is this a myth?

typically these engines are nothing unusual (2jz, RB, etc) im just trying to understand why someone would change a OEM trigger wheel to another?

More teeth equals, potentially, more accurate ignition and injector timing. On a stock engine this probably won't buy you anything. On a full race engine with a decent ECU you might get 0.5-1% extra. Up to you if you think it is worth the effort.

If you are concerned about missing a tooth at high engine speed, get a better trigger wheel design, higher frequency sensor and mount it better. After many issues with my 10,000 RPM 4AGE 36-1 trigger setup my VQ30 has the trigger machined in to the flywheel, the sensor mounted in the gearbox adapter plate (yes, IN...no wobbly bolt on mount directly exposed to the elements here) and plenty of frequency headroom on the sensor.

Having just chased an issue with a crank sensor mount that cost two engines (not mine) the mounting of the sensor is just as important as the sensor type and the pattern being read. What was happening on these engines was that there was a harmonic developing in a certain rev range that caused the bent sheet steel fabricated mount to vibrate, this was enough of a vibration that it was double counting tooth edges and changing the ignition timing.

My mounting bracket was a really nice machined aluminium bracket...fixed by two m4 bolts and almost not flat surface. Air gap was pretty random, especially if someone worked at the front of the engine. Usually didn't find out there was an issue until the second lap of the session and was missing a couple of thousand RPM. Not good when you only have a 2000 RPM power band!

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