Another dropped cranking RPM

[grippo]

I will have to go through the code carefully and see what could possibly be making it lose synch. At least we know it wasn't the cam signal.

[grippo]

OK I found a few other places where the resynch could have occurred so I have one more code version attached to test. Just download and repeat the last run and datalog.

[geoffct]

It started right up..... I need to determine a number of things but it worked, it worked!!!!

Thanks and I will update you more later today.....

Geoff

[geoffct]

Sorry about the lack of updates.

My timetable got crunched due to the approaching competition and finals. We're a really small team here...

Anyway I was running fine, but I had to finish my restricted intake manifold and once I hooked everything back up I now can't get past 3000rpms. It is late, but I scoped things out and I don't see the error now. I can attach more logs, and as always any help is appreciated. Competition is in 9 days and the engine is not my only concern.

I get a the tach count resets and I get a trigger+/- of 999 and if it dies it than jumps to 888, if that helps.

Thanks
Geoff

[grippo]

The tach count variable is supposed to count tach pulses - it is not counting resets which are indicated by rpm going to 9. This output will not help us in this case. The =/- going to 999 indicates that now we are losing cam sync. The 888 at the end is to be expected and just mean the engine wound down to < 50 rpm at which point it automatically loses synch. So let's summarize what is going on now:

1. The engine runs ok up to 3000 rpm. Is this true and is it consistent ? If you fire it up, run it below 3000 for a minute, cut it off and repeat about 5 or 10 times, will it respond the same way each time with no loss of any synch and the +/- counter stays 0 ?

2. When you go past 3000, the +/- counter goes to 999, and at the same time you get rpm=0 and a reset ? Again is this consistent ?

If what I said is true, then I would put the cam signal on a scope along with the wheel signal and see what may be different when you go past 3000 rpm. Cam synch is lost because the cam signal must arrive in between the same 2 teeth every time every 2 revs, and not arrive on the in between revs.

[geoffct]

I found the problem I had a resistor added into the VR circuit but it shorted out. The resultant signal was not usable past 3krpm

Thanks for the help.

Geoff

[geoffct]

Bruce....Earlier in the year you said a few things and I just wanted a check before I make these changes. Currently we have a 10k resistor inline with the VR+ lead.

If I am reading the schematic correctly there is already a 1k (R26) resistor on the VR+ input. The resistor inline is a 10k resistor. Could I replace this (R26) with an 11k and have the same effect so I do not have to have my resistor inline in the wiring? I have a picture attached of this. This should be perfect as I see it in the schematic.

Also I notice there is a 1meg (R51) resistor on the VR2+ Cam Lead. We are currently using an external resistor to draw that line up (10k) because our cam square wave has a very substantial charge time constant using just the VR2+ input. This resistor is wired between VCC and VR2+. Could I replace this 1meg resistor with say a 50k (?) resistor and have the same effective output? I am not entirely sure about this one, this is why I would like your input.

The ideas above are proposed to replace what I currently have which can be seen in the attached pictures.

Competition is in 2 days and we are scrambling with many projects and I just wanted to see if this is possible. Thanks for the quick response! If you want to give me a call feel free. If this is not easy to solve, I am just going to keep my resistors in my current harness. Thanks!!!

Geoff
248.390.8541

[Bruce Bowling]

If I am reading the schematic correctly there is already a 1k (R26) resistor on the VR+ input. The resistor inline is a 10k resistor. Could I replace this (R26) with an 11k and have the same effect so I do not have to have my resistor inline in the wiring? I have a picture attached of this. This should be perfect as I see it in the schematic.

Also I notice there is a 1meg (R51) resistor on the VR2+ Cam Lead. We are currently using an external resistor to draw that line up (10k) because our cam square wave has a very substantial charge time constant using just the VR2+ input. This resistor is wired between VCC and VR2+. Could I replace this 1meg resistor with say a 50k (?) resistor and have the same effective output? I am not entirely sure about this one, this is why I would like your input.

Yes, you can replace both resistors like you indicate, you will have the exact same thing!

Also, it looks like I will be at the FSAE event on Thursday afternoon and Friday so if you need anything from me (spares, etc) email me at bbowling@earthlink.net and I will be sure to bring them along...

- Bruce

[geoffct]

Oh that sounds great. I think we are all set as far as spares. I have 3 new ampseals, ~60 pins, two microsquirts, 2-3 of most every sensor and actuator. The only thing we don't have spare is hands for wrenching.

If you were to stop by our paddock however, we would like to thank you for all your assistance. Plus we're one of only a few microsquirts at competition that I have counted, so you might want to see what we've done. =-) Also I wouldn't mind chatting a bit on a couple summer projects I have planned.

Thanks
Geoff