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That's too bad about the Spec flywheel, but good that NCLA951 caught the issue before you wasted time attempting to set sensor gaps, etc . . . . I wonder what the issue is. Does the Spec flywheel not have a provision for the reference mark sensor stud or is it in the wrong place? I feel that if the starter ring gear were not located correctly you would have starter engagement issues . . . .
Anyway, for posterity's sake I took some screenshots of VEMS trigger logs of my 951 (with stock flywheel and speed/reference sensors) cranking and at cold idle, pictured below (might not have caught the slower starting cranking speed before the engine fired, they look very similar). Maybe they will help someone else with the same setup who is chasing a starting issue.
Here is a couple of seconds of cranking, then turning the key off before the engine fired. The entire cranking period looked like the first half of the graph, nice and evenly spaced and sized. nick.cfrancis's trigger log shots show erratically sized and spaced trigger events while cranking.
That's too bad about the Spec flywheel, but good that NCLA951 caught the issue before you wasted time attempting to set sensor gaps, etc . . . . I wonder what the issue is. Does the Spec flywheel not have a provision for the reference mark sensor stud or is it in the wrong place? I feel that if the starter ring gear were not located correctly you would have starter engagement issues . . . .
In my educated opinion, the issue is that the 3 scalloped lobes on the spec flywheel will trip the sensor under certain conditions.
Droops83: Thank you for posting screenshots of your trigger logs. I can definitely see my issue when comparing to your clean trigger log.
I reached out to David Ewell via email and received confirmation today that he was able to resolve the startup issue with the LR Spec scalloped flywheel on a 951 using the 36-1 Clewett Trigger wheel. https://rennlist.com/forums/944-turb...startup-3.html
Peep also confirmed that this idea would work.
David did mention a potential issue regarding the wiring of the Clewett trigger sensor requiring modifications to the VEMS board. I am hoping to avoid this issue by utilizing the stock reference sensor in the Clewett bracket described here: https://rennlist.com/forums/944-turb...r-wheel-3.html
I also reached out to Lindsey Racing regarding regarding my issue. Dave explained that in the past they had issues with the spec scalloped flywheel causing false triggers. https://www.lindseyracing.com/LR/Parts/SP44S-FIX.html
This issue was remedied in May 2017 with a smaller diameter flywheel from Spec. Dave proposed the idea of raising the studs on the flywheel and backing the sensor out to compensate in an effort to avoid detecting the scallops on the flywheel. Given that the flywheel is already installed, there would be great difficulty in setting the studs to an equal height and backing the reference sensor out to correspond to the change. I am going to go with the Clewett 36-1 trigger wheel at this point. Unfortunately, even though Clewett is based only a few miles away from my location, they are out of the office for the Thanksgiving holiday, so I will be on hold until they return on Monday, 26 November.
In my educated opinion, the issue is that the 3 scalloped lobes on the spec flywheel will trip the sensor under certain conditions.
Is this just with VEMS, or have people had issues with the factory DME/Spec flywheel as well? My (somewhat) educated opinion is that the whatever the VEMS uses to interpret the AC waveform generated by the factory VR sensors simply isn't as resilient as that in the factory DME chipset, and it is therefore more prone to interference. Though it would take someone much more versed in electronics than I to explain exactly why!
Almost done with installing the Clewett trigger wheel and mount but I am somewhat lost on the wiring. Given the reference sensor harness below, which pin is the sensor, ground, and shield?
Hmm. Back to the drawing board. Do you know if you have FAE or OEM Bosch speed reference sensors? And if you have the updated bracket with sleeve?
Thanks but I found out that one of my injectors were bad and swapped in a spare set. I also didn't know the set I had in was 72#s, I thought they were 55#s. And the set I put in I thought were 52# are actually less, 52#s at 3.8bar. I'll just retune it for now while I save for a set of deka high Z 80#s. Regarding the pwm channels, do you need to change it when switching from high Z to low?
That's exactly what I'm running in my SC set-up blue 80# dekas.....exactly what Peep said for settings
Also, where would you recommend I place the missing tooth with the motor at TDC? The Clewett instructions only contain setup instructions for the 60-2 wheel.
Here is my current configuration. With the motor at TDC the sensor is reading tooth 7-8 after the missing tooth.
I don't know much about trigger wheels set ups, but if you research it say with MegaSquirt or other 36-1 set-ups. The missing tooth is typically placed so many teeth past the sensor at TDC and 8 is typical given the amount of rotation. Looks like you are limited to the choices given the set fasteners and pulley positions. That looks right to me to try as long as the config matches.
This weekend I installed the Clewett trigger wheel and Clewett magnetic sensor adapted to the factory harness using the following pinout:
I'm not sure how to adjust the trigger settings in VEMS so I emailed Peep on Saturday to ask for help with changing the config but have not recieved a reply. Does anybody know if he is on vacation or out of the office?
Edit: Just got a reply from Peep. I'll be trying to configure it this evening after picking up a timing light.
Last edited by nick.cfrancis; 12-04-2018 at 04:12 PM.
Happy New Years to all. Gonna start work on the 951 again. Gonna try and solve this issue once and for all. Gonna start by checking all grounds, check grounds and power at vems ecu, and swap out hi Torque starter for stock unit.. The move on to sensors, gap and updated bracket with sleeve. Did the 60-1 clewet setup solve the problem??
Happy New Years to all. Gonna start work on the 951 again. Gonna try and solve this issue once and for all. Gonna start by checking all grounds, check grounds and power at vems ecu, and swap out hi Torque starter for stock unit.. The move on to sensors, gap and updated bracket with sleeve. Did the 60-1 clewet setup solve the problem??
The 60-1 clewett setup did solve the scalloped flywheel problem.
One side effect I am experiencing is that if the vehicle is turned off, the cooling fans turn on, and then the key is turned back on, vems will read the cooling fan as the trigger wheel and believe the motor is running at around 600rpm and start firing the injectors. The only workaround I have found is to wait for the fans to turn off before turn the key back on. The risk with this workaround is that when my wife was driving, she stalled the car in stop and go traffic, didn't hear the fans running, and tried to restart it. This flooded the motor and took about 5 minutes to get started again. I was just thankful it didn't happen in the middle of the freeway.
11-19-2018, 10:49 PM
