efi Finally Completed Efi Conversion

[jmp]

I'm liking all the electronic puns, keep em coming!

[mikebontoft]

I feel my resistance to this thread weakening as my temperature rises.

[robsanab]

jmp... thanks for your write up... I look forward to updates, although I hope to tackle my EFI project within the next couple months. Question though, you say:

The Hamlin hall sensor I was running was super temperature sensitive (only rated up to 85C!!).

 

I assume this is the Hamlin 55075? ... are you sure it was the sensor that went belly up? Or, as you found out with the VR sensor, maybe it wasn't set up correctly? I ask because this is what I purchased and plan to install based on folks here using it as well as research on other forums. The Hamlin data sheet does indeed say 85C, but their technical paper says 100C (which would be 212F). I wouldn't think underhood temps would get up even to 185F (85C) since it is mounted low and downstream of the fan (as well as mounted to an aluminum heat sink, since I'm using the '02 Again sensor bracket). I don't know, I am just questioning using the Hamlin now after your report, yet I hate to just trash it if your issue could have been something else. Any thoughts?

 

Rob   

[jmp]

Hi Rob,

 

Yes, it was the 55075 and that was almost certainly the culprit.

 

The first one I had worked great when I got it, super clean signal, nice clean square wave unlike the VR sensor, easy to debug. I got sync losses every now and then but I chocked it up to noise in the system, or some loose connection somewhere or bad solder joint or something. I had no reason to suspect the Hamlin.

 

Over time the sync losses got more frequent and more annoying. I still thought it was a weird connection. I was using the relay board, and that seemed like a black hole of debugging issues so I meticulously redid the entire wire harness to eliminate unnecessary connections. That was actually worth while because it made the whole setup look way cleaner but unfortunately the sync losses didn't go away. They were totally unchanged and still getting worse over time.

 

One day I was running an errand, and the car kept stumbling until eventually it just died in the middle of the road and wouldn't read any signal from the crank sensor at all. I messed with the tune and nothing seemed to do the job. I eventually walked home with my groceries and left the car parked over by the store.

 

The next day I walked back down to it with my oscilloscope to check some of the connections but before I opened the hood, I tried the key and it somehow magically started. I brought it back to my driveway and let it warm up all the way and found that it would run fine until the engine temp got to the high 70s (celsius) and it would start stumbling and when it hit 80, (the temp I have the engine fan turn on) it would just die and not restart until I let it cool back down.

 

My first hypothesis was that it had to do with the power draw from the engine fan, but after changing the cutoff temp for the fan, and unplugging the fan I saw the same behavior. Also, it would start stumbling well before the fan came on. That kept me stumped for a while, I couldn't figure out any significant state that changes at around 80 degrees celsius. I just left the car for several weeks and almost forgot about it when I thought to check the datasheet for the Hall sensor. When I saw that it had such a low threshold I thought switching it out sounded promising but I was skeptical. Replacing it with another Hall sensor was easy, and made for a nice control case so I tried that first.

 

I bought a new 55075 and it seemed to do the trick. The car ran much better... for a while. It went bad even faster than the old one did. Within a few weeks it was getting almost as bad as the first one had gotten in over a year.

 

Switching back to the VR sensor meant messing with the bracket again, and redoing the wiring, and all kinds of things that I really didn't feel like doing, but once I finally got around to it I was glad I did. The number of sync losses went way down, and there was no longer a temperature dependence to them. The sync losses didn't completely go away until I replaced the whole length of the crank sensor wiring with (high temp) shielded wire.

 

I discussed the issue on the MSExtra forum ( http://www.msextra.com/forums/viewtopic.php?f=132&t=51442 ) and got the following response from James Cortina (one of the maintainers of the MSExtra firmware):

 

    85C parts have no place on or near an engine. 125C is as low as I'd go. 150C better.

 

Someone did mention the Cherry GS1001 Hall sensor, which has the same formfactor as the Hamlin 55075, but with a 125C limit. That might be worth looking in to.

 

In any case, I'm very happy with my decision to go back to the VR sensor. It's cheap, basically indestructable and it seems to give me a reliable signal. The 02again bracket is already set up for the VR sensor by the way. I'm using that, too, and I needed to fabricate a small secondary bracket to mount the Hamlin to it in the first place.

 

Sorry for the long winded response, but that was one of the most annoying parts of the whole build so hopefully you can avoid that particular pitfall.

[robsanab]

Thanks very much for the thorough explanation.

 

With all that in mind I am leaning towards getting the Hamlin 55505 (at 125*C and mentioned in the msextra link)... the Cherry seems to require an external pull up resistor (as does the Honeywell GT1) and it's like $45. Maybe that pull up resistor isn't a big deal but it just adds another engineering element that I know little about.

 

I will have to see if I can modify the mounting to fit that larger barrel, not to mention that flange being in the way... Tom (O2 again) customized my mount to fit the Hamlin 55075 (M12 barrel diameter) since all my research up to that point recommended this sensor. All I know is that with this information I don't want to chance it... I want to get it right the first time.

 

thanks for the lesson... I could see how that would have been a frustrating problem.

 

For reference, what VR sensor are you using? In case I go that route.

 

Rob

[jmp]

I'm using the Airtex/Wells 5S1739 VR sensor (very generic model, comes under like half a dozen different part names / manufacturers) and the corresponding wire pigtail (Airtex/Wells 1P1258, which is inexplicably more expensive than the sensor its self):

 

 http://www.rockauto.com/catalog/moreinfo.php?pk=941155

 http://www.rockauto.com/catalog/moreinfo.php?pk=2064352

 

It could probably be found used in a junk yard or on ebay pretty easily, and with really high probability of still being functional. As I understand it, it would be pretty hard to break these things and they don't have any parts that would tend to wear out.

 

Good luck finishing up your build!

 

Cheers,

Jonathan

[zinertia]

Jonathan,

 

Any further changes/insight into the conversion that you can pass on?

Thanks

Dennis