Gawd I Hate Points, Won't keep a tune |
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Gawd I Hate Points, Won't keep a tune |
bbrock |
Sep 4 2021, 08:09 PM
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#1
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
Quick background. Engine is a rebuilt 2L with Elgin cam and Weber 40IDFs. I bought a Pertronix Ignitor 3 to avoid having to mess with points but I could only get it to work well with a NOS Bosch 050 distributor. It runs rough with a brand new Bosch clone SVDA and the OE dizzy. However, the engine runs best with the OE DVDA distributor so I'm running that with points.
The problem is that I've had to adjust dwell and timing 3 times in only 1,000 miles of driving. Each time the dwell creeps up until the engine starts spitting and farting and is a bit hard to start when warm. Readjusting the dwell and timing gets it running like a top again. So (IMG:style_emoticons/default/WTF.gif) Only thing I can think is that the phenolic block on the points is wearing crazy fast. I lubed the cam and block with high temp slicone grease and I can feel it is still on there. Did I just get a shitty set of points? |
jd74914 |
Sep 7 2021, 08:24 PM
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#2
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Its alive Group: Members Posts: 4,780 Joined: 16-February 04 From: CT Member No.: 1,659 Region Association: North East States |
Totally agree-certainly worth the try for a few thousand miles. Parts are cheap anyways.
I have a feeling your issue may be exacerbated by being a bit closer to the edge than I usually ran. Given the fact that I was doing stuff on the side of the road or in my dorm parking lot a lot, usually at night, I was never breaking out a timing light or really anything but a feeler gauge. What sounded good to my ears was probably not as fine tuned as the factory specs. I do think your ultimate goal of going to MS with COP or CNP is far better. With a good crank position signal and accurate timing it’s amazing how crisp you can get even an old motor to run (only caveat here that MS crank position calculation is kinda slow with junky hardware filters so you don’t see ultimate benefits as compared to some FPGA-based crank positioning calculations, but it’s still 1000x times better than a distributor). |
bbrock |
Sep 7 2021, 10:30 PM
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#3
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914 Guru Group: Members Posts: 5,269 Joined: 17-February 17 From: Montana Member No.: 20,845 Region Association: Rocky Mountains |
Totally agree-certainly worth the try for a few thousand miles. Parts are cheap anyways. I have a feeling your issue may be exacerbated by being a bit closer to the edge than I usually ran. Given the fact that I was doing stuff on the side of the road or in my dorm parking lot a lot, usually at night, I was never breaking out a timing light or really anything but a feeler gauge. What sounded good to my ears was probably not as fine tuned as the factory specs. I do think your ultimate goal of going to MS with COP or CNP is far better. With a good crank position signal and accurate timing it’s amazing how crisp you can get even an old motor to run (only caveat here that MS crank position calculation is kinda slow with junky hardware filters so you don’t see ultimate benefits as compared to some FPGA-based crank positioning calculations, but it’s still 1000x times better than a distributor). Do you have any experience running a cam position sensor with MS? Looks like Mario is working on a new version of his. I'm still learning but intrigued by the ability to run sequential spark and injection. I don't know anything about calculation speeds or if the combo of cam and crank position sensors would affect that. As Phil mentioned, something important for me is having %barametric sensing because I could easily drive through a pretty massive range of elevation in a day's drive here. If I understand correctly, this involves adding a second MAP that is open to atmosphere to get an ambient pressure reference. Not sure if I have that right though. |
jd74914 |
Sep 7 2021, 11:49 PM
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#4
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Its alive Group: Members Posts: 4,780 Joined: 16-February 04 From: CT Member No.: 1,659 Region Association: North East States |
Do you have any experience running a cam position sensor with MS? Looks like Mario is working on a new version of his. I'm still learning but intrigued by the ability to run sequential spark and injection. I don't know anything about calculation speeds or if the combo of cam and crank position sensors would affect that. As Phil mentioned, something important for me is having %barametric sensing because I could easily drive through a pretty massive range of elevation in a day's drive here. If I understand correctly, this involves adding a second MAP that is open to atmosphere to get an ambient pressure reference. Not sure if I have that right though. No, I haven't run a cam trigger. I'm not sure there is much benefit to running sequential to be honest [particularly on a T4], unless you are really trying to push to slightly higher efficiencies. In higher speed applications (think sport bike), you gain some charge time for the coils which can be critical, not an issue here. I do have a cam trigger setup (not from Mario-it's a custom jobber using an OEM distributor base with tooth wheel/hall effect sensor) which I might try one day. You definitely want a dedicated barometric pressure sensor for your use rather than depend on a key-on correction. If running Alpha-N (TPS vs. engine speed), the barometric correction is quite important given ideal gas law. Speed density (MAP based), I'd still run one personally, but theoretically shouldn't be necessary. Frequently people run blended Alpha-N which basically mean Alpha-N at idle/low engine speeds and speed density at higher speeds, again, an important case for a barometric pressure sensor. Are you planning on using Mario's crank sync? I've got it and think the packaging is very slick, plus he includes a hall sensor which is perfect for the MS application. As MS has poor noise filtering, and does not allow setting engine speed dependent trigger voltages, so really 'need' a hall effect sensor rather than VR since processing the square wave is easy. Typically, I'd recommend using a VR sensor as a) the edge triggering is slightly more accurate in time domain, and b) ICs in hall effect sensors sometimes switch output polarity resulting in a speed-skipping, but neither matter much if the trigger doesn't work from the start. |
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