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Rpm signal loss


seattlejester

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Messed around with it a little more today.

 

Definitely ignition based. Sitting on the limit floored it sounded like the antilag/launch control.

 

I played around with distance and I only got running to not running sensitivity did not seem to be phased much. And playing with the pots did not seem to do anything, went from 0-5 turns in half turn increments.

 

I did floor it to see if it was TPS based, after hitting 4k and limiting for a while it bumped to 5k intermittently and then dropped  but never went higher which makes me think it is something to do with the trigger wheel/sensor.

 

Next plan is to order the tabbed sensor and get some thick steel and some time in a friends garage to try and make a workable bracket. Thanks for the brainstorm guys.

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  • 3 weeks later...

Tabbed sensor ordered and installed. Setting adjusted in megasquirt to adjust for new mount location (distance to missing tooth).

No dice, seeing more above 5k, but reliably only up to about 4.7k rpm.

 

I took it for a drive, the car pulls, and pulls hard right up to the 4.7-5k mark and then just kind of stops accelerating. Using analyze live, I can see the ECU thinks that the car goes from 4.5k down to 700 which really indicates that the sensor is loosing the teeth, but this sensor has been proven to go up to 19,000 RPM.

 

 

As suggested, I essentially sat on the throttle, and turned the center pot about 5 turns after zeroing it out to no avail.

 

Will edit with the tooth and composite logs.

 

Thoughts:

 

Not getting enough fuel.

I do have a bit of wonky settings by having a resistor box in line to low impedence injectors. If this was the case, I should see the AFR lean out as I approach the problem area, AFR actually goes towards rich, and then when the limiter is hit, goes pig rich.

 

Spark problems.

Couple things come to mind here. I think we have hammered out the wiring now, so just a matter of some small things.

Spark plugs could be fouled, just a possibility that occurred to me, could this cause a hard RPM cut? I don't think so, but then again I don't have much experience.

The coil packs are not getting enough time to recharge. Just some simple math. Miata guys use these pretty regularly up to 7000rpm. I am running a wasted spark setup so essentially they have to fire twice per 4 stroke cycle, thus in essence they are firing at a higher rate, could I just be hitting the limit of the coil packs? If it is a charging issue, maybe a capacitor as suggested may help with the recharge rate, does this line of reasoning have any merit?

Can the wrong timing value also cause this issue?

 

Mechanical problems.

I have heard of instances where engines refuse to make power/refuse to rev past a certain point due to an actual mechanical problem, in such cases can it be a hard cut? As in at exactly xxxx rpm the bearings start spinning and thus engine refuses to rev?

 

 

I am still really leaning towards some kind of setting problem with how the megasquirt determines engine speed. Just feeling frustrated, I mean if it was a diesel that would be great, but the fun part is in the higher rpm range, so this just really bums me out.

 

Appreciate the help as always.

Edited by seattlejester
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Maybe it's the other end of the circuit, not the sensor end.  A bad component that fails at high frequency.  

 

Have you tried the JimStim?  Apparently, it replicates a clean signal from a variety of wheels.  Looks like it was thought up and designed for exactly your problem.  Not too spendy, especially considering the time, money, and effort you've already spent.  

 

http://jbperf.com/JimStim/

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I really should have gotten the jim stim board, I really should have gotten it a while back, would have really helped figure things out. 

 

I have this hope:

http://forums.hybridz.org/topic/104879-car-wont-rev-past-3000rpm/

 

I threw my cheap timing light away that made me think all the coils were going off at the same time, and just received a nicer one in the mail today. If the problem is as the individual above found, then the timing light will tell. Symptoms are very similar, feels like a hard rev limit, everything else feels fine.

 

If that does not work, or even if it does work, I think it is time that I invest in one of those for any future trouble shooting.

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This is my 4th time trying to post, I think my wifi is kind of iffy at the moment, so cliff notes.

 

So I had hopes that I never changed the fixed value so the spark advance was constant, no such luck. Correct box was selected.

 

Added a 10000uf capacitor, didn't seem like it changed anything

 

Used new timing gun with a spark plug wire in the COP to the spark plug and reading off of that wire. Got a good signal with the expected double advance and double rpm readings.

 

Adjusted the btdc value for the trigger wheel to bring it in line with what the timing gun was reading. Only a tooth or so off, still no change.

 

I have noticed an occasional miss every few seconds during idle. Either a dwell setting, or even at the low RPM's the ECU is having some small type of trouble.

 

Another thing to note is that 4500 is half of the max rpm I have set. I will adjust it lower tomorrow and see if that somehow plays a factor.

 

Kind of at my wits end, not sure what is going on. Pretty sure it is ignition related, if it was fuel I would expect going lean, not rich. 

 

Thoughts:

Check jumper JP1 at 1-2

Check jumper J1 at 3-4

Turn pot R56 all the way counter clock wise, then turn 2 turns clockwise

Turn pot R52 all the way counter clock wise then slowly start turning clockwise

Check dwell setting

Check max rpm capability of toyota cop

Test max rpm by lowering it to a lower level to see if it has effect

Try swapping out cop with other set of cop

Rising edge vs falling edge?

 

Any suggestions would be great, really scratching my head here.

mark 9.zip

Edited by seattlejester
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Jumpers in correct position

Upped dwell to a suggested 3ms, no difference, even went as high as 3.5 no difference

The miata guys are running toyota cop to redline in wasted spark, so do not think that is the problem

Lowered max RPM to 7000 to see if cutoff shifted to 3500, no change.

 

Only 3 things left to try:

Swap coil packs

Add resistor to R57?

Confirm polarity

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I would have to purchase one unfortunately.

 

If I were to get one, I would be testing the hall effect sensor to see that that is reading correctly yes?

 

If the sensor was missing the teeth, then it would be limited to either the sensor itself, the sensor proximity, or the crank trigger wheel.

 

If the oscilloscope showed a consistent signal, then the problem would be more directed towards wiring and the megasquirt?

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Some multimeters will measure voltage frequency (Fluke 115, for example).  Might be worth a shot on the sensor.  If it shows up dirty at the same RPM range, you'll know it's the sensor or noise on the signal.  If it doesn't anything, the meter might just have better noise filtering, or it may not be the sensor at all.  Might not be conclusive but it might tell you something..

 

You'll have to know RPM at the same time or do some math on the meter number, since you'll be getting 35x  RPM. 

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  • 3 weeks later...

I gave in the towel and called someone in for help, as I definitely believed it was a problem that someone with experience could visually spot.

 

Problem is officially solved, the problem was definitely related to the sensor mount.

 

I made the mount by making a rough measurement, tacking it in place, adjusting and then finishing off the welds. So the sensor was in an acceptable proximity to the edge of the tooth, and in the same plane, but was at a non perpendicular angle, effectively increasing the distance. I imagine the extra length made it more difficult for the sensor to register at higher rpm's when the wheel was moving faster.

 

The guy twisted the mount and I drilled one hole larger to increase the angle adjustment and the engine revved without problems.

 

Big shoutout to Mario from the Dubshop.

 

I'm sure we could have figured it out if I had taken a few more pictures, as this is definitely a case of picture's worth a thousand words, thank you for everyone's input!

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  • 3 weeks later...

Fixed the oil leak and finally got shadow dash working and took it for a little spin to the muffler shop, car really hauls butt! Right now at waste gate pressure of 7lbs and it's a real hoot.

 

New cables seem to make shadow dash act a little friendlier with the bluetooth sender. Still would like to get msdroid working so I have an alternative option. 

 

Just thought I would close with a little tidbit from the tuner. He said while the tabbed hall effect sensor is advertised as being able to read from a distance of up to 5mm, he said in practice he found the limit to be closer to 3mm or so. So don't be like me and assume you have a huge amount of room to play with, take your time and make sure the mount is in close proximity at a perpendicular angle to the trigger wheel. While it is a good idea to not have slots so the mount if ever removed can be put back correctly. Make sure that the sensor mounts exactly where it needs to be before pursuing that avenue. 

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