R-12 substitution in MSnS-E input modificaton
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0). For tuning/troubleshooting questions, please attached a datalog and your MSQ file to your post.
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
R-12 substitution in MSnS-E input modificaton
I have a MSII with 2.88 code and GM 7 pin spark module fed VR input by a GM style small cap HEI distributor reluctor/coil. I had RPM noise showing up on the Tuner Studio realtime RPM display and also as fluctuations on the Tuner Studio gauge display, as much as +/- 100 at 2-3000 rpm. My timing light showed that when MS was controling spark advance, the timing also jumped about +/-3-5 degrees at idle, but less at higher RPMs. No such problems on the stim, of course. I installed MSnS-E modification and also shielded the VR wires from the distributor to remote mounted 7-pin HEI module with no apparent improvement. I replaced R-12 as suggested in the MSnS-E modification instructions back to the original 330 ohm value, and now the car runs better at high RPM and there is little dithering of the RPM display on the Tuner Studio gauge and the realtime display of RPM appears rock solid. I still show some jump around the commanded timing advance with the timing light at idle RPMs with the MS controling spark advance. My questions are why does this resistor substition seem to help and can this lower R 12 value hurt the HEI 7 pin module or U3 since more current will go thru them with this lower resistor? I would like to know before I modify my spare MSII to this configuration or to the transistor modification which also uses a small value (390 ohms) for R 12.
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Matt Cramer
- Super Squirter
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Re: R-12 substitution in MSnS-E input modificaton
More current can mean a stronger triggering signal.MrBill wrote:My questions are why does this resistor substition seem to help
It definitely won't hurt U3 and I have not seen changing the value hurt an HEI Module.and can this lower R 12 value hurt the HEI 7 pin module or U3 since more current will go thru them with this lower resistor? I would like to know before I modify my spare MSII to this configuration or to the transistor modification which also uses a small value (390 ohms) for R 12.
Re: R-12 substitution in MSnS-E input modificaton
Matt,
Thanks for the reply. The car is running great now with this MSnS-E tach modification configuration right up to the red line I have programmed. Found that using a spark retard vs a hard fuel cut at redline is much easier on the drivetrain (and also my ears, as it would occasionally backfire really loud upon decel resumption of fuel). I learned a lot about shielding the VR signal wires to the remote-mounted HEI module as well, eventually trying successfully the aluminum tape as an outer jacket shield for the wires...which seems to work best when only grounded at the distributor-end of the VR signal wires and not tied to the car body ground. I am now searching the web for an oscilloscope so I can more intellegently assess and address EMI noise spikes and etc. Lots of internet choices for such and a recommendation of the minimum specifications needed to address automotive issues would be greatly appreciated...I dont want to buy more capability than I would ever use to work with things like MS..
Mr. Bill
Thanks for the reply. The car is running great now with this MSnS-E tach modification configuration right up to the red line I have programmed. Found that using a spark retard vs a hard fuel cut at redline is much easier on the drivetrain (and also my ears, as it would occasionally backfire really loud upon decel resumption of fuel). I learned a lot about shielding the VR signal wires to the remote-mounted HEI module as well, eventually trying successfully the aluminum tape as an outer jacket shield for the wires...which seems to work best when only grounded at the distributor-end of the VR signal wires and not tied to the car body ground. I am now searching the web for an oscilloscope so I can more intellegently assess and address EMI noise spikes and etc. Lots of internet choices for such and a recommendation of the minimum specifications needed to address automotive issues would be greatly appreciated...I dont want to buy more capability than I would ever use to work with things like MS..
Mr. Bill