Sync loss with cheap Crank sensor

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93supercoupe
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Sync loss with cheap Crank sensor

Post by 93supercoupe »

Hello all

BMW with 60-2 wheel
stock VR sensor

I had issues with my OEM sensor where it ended up not starting. So i bought a cheap 20$ ebay unit. The car fires right up but losses sync at 2700RPM.

I took a tooth log of it, but my questions is should i even mess around with this cheap sensor, or should i just go get a stock sensor?

Playing with noise filtering, it only caused it to lose sync earlier.
BootlegTuned
Matt Cramer
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Re: Sync loss with cheap Crank sensor

Post by Matt Cramer »

Try a 10K to 20K resistor inline with the sensor.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

I am having the same issue with my DIYautotune hall sensor on the crank. always looses sync above 4000 rpm, usually 4200-4400. easy to see here in my composite and data logs.

don't mind the afr signal bouncing around. its not controlling anything and I get a much cleaner signal on the gauge. I thought I had a noise issue when I was looking at earlier logs but after changing/trying a few things today I'm pretty sure im loosing signal on both my crank and cam signal wires, always around that rpm. rev limiter is set at 5800soft and 6000hard
grom_e30
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Re: Sync loss with cheap Crank sensor

Post by grom_e30 »

post up a msq, have you also got a composite log of it losing sync, that one was all synced
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

sorry, posted the wrong log

the one I'm posting now seems to loose both signals entirely. not sure what is going on there. I spent some time yesterday trying to eliminate any unwanted noise by moving the coil well away from the wiring and I routed the coil wires in a different location also. this log was taken after doing so. using the DIY harness with shielded wires on the crank signal. cam sensor is un-shielded.
grom_e30
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Re: Sync loss with cheap Crank sensor

Post by grom_e30 »

was the engine def having sync loss there, reason i ask is the signals appear to go mia but there is no red marks at the bottom to indicate that sync was lost.
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

yeah that log was a little strange. here is one that shows sync loss indicators on page 81. I think I am going to try the 10k inline resistor today unless you guys thing I might have better luck adjusting the vr conditioner.
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

this one is much better. just took this composite log a couple minutes ago in the driveway. atleast its got something to look at.
grom_e30
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Re: Sync loss with cheap Crank sensor

Post by grom_e30 »

the resistor is for vr sensors, you do have a sync issue but in that log i cant tell if its a result of a extra tooth or if its missing a tooth.
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

I tried to do a tooth log but it will only save the first page. That second one I posted today is better but like you said it's hard to tell how many teeth before the loss. According to the data log it's "missing tooth at wrong time"

I'm kind of at a loss at this point. Might try to adjust the vr conditioner pots again but I'm not terribly optimistic that will work.
grom_e30
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Re: Sync loss with cheap Crank sensor

Post by grom_e30 »

sync reason 2 will happen, the ecu is expecting 58 teeth then the missing 2, but if it gets only 57 or if it gets 59 then the missing 2 it will have a fit and and declare sync loss, if you get extra teeth then its a noise issue.
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

zooming in on the log it looks like I am occasionally loosing a tooth at random but only above 4000rpm. . . still noise?? or is something else. not sure what else I could do with the crank trigger to prevent noise other than routing the shielded pair completely separate from everything else. I only have about 40-50mm of unshielded wire coming off the sensor before its spliced into the harness but maybe that's my problem. the only other thing I can think of at the moment is my main power from the battery comes thru the same hole in the firewall as the MS harness. those are the only potential noise sources I haven't addressed that come to mind.
grom_e30
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Re: Sync loss with cheap Crank sensor

Post by grom_e30 »

noise would normally manifest as an extra tooth that shouldn't be there, you have the opposite issue by the sounds of it, how big us th sensor air gap?
1990 bmw 320i daily driver with m20b25 ms3 sequential fuel, 380cc injectors, d585 coil near plug, home made cam sync, launch control, fan control, vss, homebrew egt logging what's next????
2802NR
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Re: Sync loss with cheap Crank sensor

Post by 2802NR »

the gap is well within what DIYAT calls for but after talking to a friend of mine last night we are thinking that is likely the issue. not that the gap is wrong but more likely that the bracket for the sensor may have a little spring to it when it vibrates just right. and that 5 cyl definitely has some harmonic to it right around 4000rpm. the thought had crossed my mind but the bracket I made seems pretty solid so I kept brushing off the idea. going to try adding some re-enforcement gussets to the bracket itself in the next couple days after work. hopefully that will stabilize the sensor and help solve my issue.
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