| Author | Message | ||
     Sanders |
After a recent conversion from FI to a carburetor I blew through two speed sensors. I checked my wiring and it was good to go and there were no obvious shorts. At 47 dollars a sensor it didn’t take long before I looked for a solution. Thanks to Reepicheep Badweb member who had post on wiring a car cell phone charger in between the sensor and the input power. I used a Nintendo DS charger which puts out a regulated 5.2VDC and my Auto Meter speedo calibrates itself to work of the lower voltage. The only downside so far is below 20mph it doesn’t appear to be accurate, and on occasion it takes a minute to ramp up. Above twenty its spot on and the needle doesn’t jump. I still don’t know why the conversion caused this problem. I may be wrong but removing the injectors and other sensors may have caused some spikes in the system. Also it is good insurance; I would rather have a five dollar car charger burn out instead of a sensor. | ||
| Blks1l |
Did you get rid of the stock ECM when you did the conversion? I did it on my S3 several years ago but left the RACE ECM in for the ignition and have not had any issues. | ||
| Sanders |
No I still have the ECM but I could probably get rid of it. I used a Daytona Twin Tech ignition and wired it into the stock wire harness, which wasn't much fun. I don't know if it was on this forum or on another but I read that switching over to the carb wouldn't increase your horsepower. I went from 71rwhp to 85rwhp, thing runs like a raped ape with the mikuni. | ||
| Dynosaur |
Could you not have wired the speed sensor power input to the 5V sensor output (Gray pin 1) on the ECM? | ||
| Sanders |
Maybe, I didn't know that was 5VDC. That may be and option in the future. The voltage going into the speed sensor was about 8.2VDC. The service manual says that this is fine. The voltage regulator is easy to wire in the biggest hassle is getting liquid electric tape all over the place. | ||
| Reepicheep |
Cool! Should work fine all the time though, even at 5 volts. Not sure why it is taking a bit to warm up... hopefully you didn't half bake your current sensor before putting on the filter. Using the ECM power would probably work fine as well, that was the factory fix on the early firebolts. I don't have a storage scope, so I just used the most conservative approach, and filtered the voltage at the point where it was about to hit the ECM. | ||
| Kalali |
"..I went from 71rwhp to 85rwhp..." You are now where you should have been if your FI system was working properly. I can see why you switched over... | ||
| Sanders |
I may have spoke too soon. Once again my speedo doesn't work. Pin 1 on my ECM is 10.3VDC so that isn't an option. The big difference now is the needle will go up to 20 then drop to zero, then maybe back to 15 then stay at zero. I'm starting to wonder if I might have a bad ground. Does the speed sensor read as an open across the circuit or is going to read as a short? | ||
| Dynosaur |
Hmm, pin 1 on the gray connector (red/white wire) should be 5V output. Pin 1 on the black should be 12V input. | ||
| Reepicheep |
It probably actually is an option. I forgot where I dug up all the info, but I think the hall effect sensor in there is likely rated for 15 volts. That's why they can run unregulated on many bikes forever with no problem. The problem is that if something else in your charging system is spitting out transient spikes of some kind... those go WAY above 15V and nuke the sensitive CMOS junctions in the sensor. So if the ECM 10v is regulated, then that should be absolutely fine. You can test the sensor by waving something magnetic across it. When the magnetic thing is there, I think it goes low, and when it's not it goes high (though I may have that backwards). | ||
| Sanders |
Well, I have to give the nod to Dynosaur. You were correct pin 1 does have 5vdc. I was testing the wrong plug. Anyway, I got it fixed. I think since the gray wire going to the sensor is the same gray wire that runs the coil. I might have been getting some feedback. I looked at pin 1 and that wire went to the cam position sensor. Since I'm not using the that anymore I just swapped the hot wires. Now the speed sensor runs off the TPS and CPS circuit all alone and hopefully free of EMI. On the test ride it worked perfectly. Hopefully this is the last time I have to by a speed sensor | ||
| Dynosaur |
Thumbs up dude... | ||
| Snowbees |
splice the speed sensor supply into the cps supply as its regulated voltage. Its a recomended modification on the uk buell enthusiasts site www.ukbeg.com |
