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Crank trigger miscount on rb30

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Hi all

I have a very interesting little (causing me major grief) problem! i have a rb30 turbo all the good stuff in it running a Haltech plantinum sport 2000, LS1 coils, crank and cam trigger setup (12 teeth on crank) using Hall GT101 sensors.

Here is the problem and how it started, once we got past the running in stage of the new motor we started to turn up the boost and started to find a miscount, it was very small to start with but as the dyno runs got more frequent they got worse. (as the car temp got hotter)

Now my tuner who is not a fan of Haltech in any form started to look at the ECU as the issue but we tried the latest motech with a few mods plugged it into the loom and same issue! so not the ecu!

we then thought maybe electrical interferance so ran two new 3 core cables to both of the sensors and avoided other wires by running them outside the car in thru the window and into the ecu, still same issue!

so onto changing the sensors both brand new in tight checked all the mechanicals (brackets, air gap etc) and nothing!

we have now run out of options, i am thinking of the crank floating under load and causing the miscount on the trigger disc on the crank??

any ideas would be greatly appreciated

lindsay

Get an oscilloscope on it or if the Motec is still fitted use its built-in ref/sync capture. It could be something like the cam tooth edge crossing over or clashing with a crank tooth.

Hi Adam

Thanks for your input, I'm pretty certain my tuner had gone over this and all checked out. I'm thinking the 12teeth on the disc is not enough? And not giving the ecu an accurate reading?

Mechanically everything seems very good, I'm leaning back towards electrical and in particular the power supply to the ecu and sensors or the earth grounding. Not sure if this would be it but willing to try anything

Lindsay

No 12 evenly spaced teeth with a GT101 should be perfectly fine assuming the teeth are a reasonable size (they need to be bigger than about 5 x 5 x 5mm). An oscilloscope capture is the first thing you should do as it will rule out most of the possibilities right away.

I agree 12 teeth is not necessarily a problem, assuming the sensor is measuring the teeth correctly. I would argue 12 teeth is enough information to run an engine pretty well, there are plenty of big-power 2JZ cars using their OEM 12-tooth crank trigger wheel. Oscilloscope data should help, be prepared to spend some time researching and learning how to use the tool correctly if you're not experienced with them. Also note that it's pretty common for oscilloscope probes to act like antennae and pick up spark noise when the engine is running... that's not a guarantee the spark noise is on the signal itself.

If either of your ECUs can give you clues to which errors are happening (extra edges or missing edges) and which signal is affected (crank or cam) that would help point you in the correct direction. Missing edges are often due to sensor air gap problems or misalignment between the sensor and the trigger wheel teeth. If you haven't already tried adjusting the air gaps, that's usually an easy thing to adjust with aftermarket threaded sensors and I've heard of it solving problems. Extra edges are often due to picking up noise from spark plugs. In general, it might help to improve the grounding for the ignition coils, cylinder head (where the spark plugs are installed), and the battery in order to give the spark energy a good path to travel. If you are able to move the sensors physically far away from the coils and spark plugs that may also help.

If your cam signal is mounted similar to the OEM sensor on the RB engines, you might have accidentally have aligned it too close to the nearest crank signal edge. If the cam signal is too close to the crank signal, a few degrees of belt movement will cause the cam signal to cross from happening 'before' the nearest crank signal to 'after' it (or vice versa). Our ECU would consider that a cam/crank pattern problem, it's not expected for the cam to move during operation for an evenly-spaced crank wheel. If your ECU software shows you the timing between the crank signal and cam signal, I'd look for the cam to be a least 5-10 degrees away from the nearest crank edge on a 12-tooth pattern (30 degrees per crank edge). If your cam sensor is on slotted mounts, try shifting it by a 5-10 degrees in either direction.

Thanks for the advice scott i will have try of what you suggested when i get the car from the shop.

lindsay

Another vote here for timing belt whip/movement being the problem. RB30's seem to be prone to this partially because of the increased block height. Have you got a twin cam head on the engine?

Hi Lindsay, i've had two mates have miscount issues with the Haltech that they chashed for quiet a while.

One of them after we fitted a new trigger setup to the engine with the long cherry type sensors was picking up miscounts at high rpm an backfiring badly through the exhaust after trying a few things it was recomended to get rid of the long style cherry sensors an get the short cherry style instead because for some reason the long ones have occasionally played up even when new.

Swapped them out an it was perfect 1100rwhp @45psi.

The other one they literally tried everything to fix the issue over the course of about 12 months with no luck, it was then suggested to check the head wasnt lifting causing the miscount. Off came the head new gasket an studs an bingo no more miscounts.

1st One was a 26/30 an the 2nd one was a single cam RB30

Hi Shaun

I'm shocked that the gasket change did the job definately something I'll consider.

A quick update for others in the post on my findings at the moment, I went over my ecu loom again and found on two things that stood out, my battery ground wire was slightly loose and I felt too many power wires were coming off the same point so I ran a separate power supply wire to my ecu. Was thinking maybe I'm getting some noise in the power supply.

Also my air gap was 2mm I have now brought it down to 1mm, the trigger disc was about 4mm off the center of the hall sensor so I have now fixed that up soon I hope to finish off a few little things and get back on the dyno.

Lindsay

In my experience this is very likely to be the alignment between the crank teeth and sync tooth coupled with cambelt whip. Often you set these up with the sync position bang in the middle of two crank teeth at idle abut at high rpm a combination of cambelt stretch and whip has the sync tooth swap to the other side of a crank tooth. Again a scope capture will show what's truly happening.

In my experience the RB30/26 combo is one of the worst for cambelt whip which makes this worse for trigger issues. Have you relocated the idler pulley for the cambelt to above the water pump? This tends to be a big help but not a fix. Due to the inherent problems with a 12 tooth crank/single sync on these motors I'd personally be more inclined to run a missing tooth crank with a single sync on the cam. This tends to be more forgiving to the sync location.

With regard to a head gasket swap fixing a trigger issue I'd say that's a little misleading. Yes, a lifting head gasket may lead to a misfire although in my experience that's actually not too likely under boost. You're more likely to just push water out into the header. At a guess it's more likely that the cambelt was tensioned more when the head gasket was swapped, hence offering what appears to be a fix.

Hi Andre

My engine is the single cam head. I had strong belief that possibly the teeth were clashing as other have mentioned, so now looks like i best get my hands on an oscilloscope and have a look at this.

Your take on the head gasket issue kind of makes sense now with the timing belt being re tensioned, even tho my engine is a fresh full rebuild i will also check this.

thank you all for the ideas and input i will keep all posted

lindsay