So I’m completely new to this and was looking for a few pointers on this thing, I have another forum for this that I’m gonna link just bc it’s pretty detailed but feel free to respond to this one and I’ll keep an eye on both of em and keep ‘em updated 😁 link to my thread: https://www.gmt400.com/threads/snipe...n.63698/page-3
Welcome to the forum!
I do not have experience with the Sniper. I do have experience with the same engine you're using. I spent a bunch of time trying to set up a TBI engine using the original 7747 ecm. Ultimately the customer wanted a better performance than I could give with the 7747 so I installed a marine PFI intake and a 7730 ecm.
I read through the GMT400 thread. The two timing tables posted are very rough. The first table has extremely dramatic changes. The second table calls for crazy amounts of spark advance.
With the original ecm, spark advance is kind of complex. There's at least one base table, and then there are special cases like cold engine and wide open throttle (WOT). I can see the base table you've posted for the Sniper on GMT400. Are there any special case spark tables in the Sniper?
Here is a main spark advance taqble I used with a 350/350 TPI engine.
Code:20 30 40 50 60 70 75 80 85 90 95 100 RPM 400 20.39 22.85 23.91 26.02 23.91 20.04 17.93 14.06 10.9 7.03 4.92 3.16 600 22.15 23.91 29.88 25.31 24.96 21.45 17.93 16.17 13.01 9.84 8.09 5.98 800 24.96 30.94 33.05 28.83 26.02 22.15 18.98 16.17 14.06 10.9 9.14 8.79 1000 29.18 37.97 35.86 33.05 28.83 22.85 20.04 16.17 14.06 10.9 10.9 10.9 1200 32.7 40.08 37.27 34.1 31.64 23.91 20.74 16.88 15.12 13.36 13.36 13.36 1400 34.45 40.08 38.67 34.45 32.34 26.37 24.26 21.8 19.69 16.17 15.82 15.82 1600 35.16 40.43 38.67 36.56 32.7 28.48 24.61 21.8 19.69 17.23 17.23 17.23 1800 35.16 39.02 40.08 37.27 34.1 30.94 26.72 23.91 22.15 20.39 21.09 21.09 2000 35.16 39.02 39.38 37.62 35.86 32.34 28.83 24.61 22.5 21.8 22.5 22.15 2200 35.16 39.02 39.38 37.62 36.21 34.1 30.94 26.72 26.02 25.31 26.02 26.37 2400 35.16 39.02 40.08 39.38 36.56 34.45 32.34 31.29 30.23 29.53 30.23 30.59 2800 35.16 39.02 40.08 39.38 36.56 34.45 33.75 33.05 34.45 33.75 32.7 32.34 3200 33.75 39.73 40.78 39.38 38.67 35.16 35.16 35.16 34.8 34.45 33.4 32.34 3600 31.64 40.08 43.24 41.84 41.13 37.97 36.91 36.91 36.91 35.16 35.16 33.05 4000 31.64 41.13 43.24 41.84 41.13 39.02 37.97 37.97 36.91 35.16 35.16 33.05 4400 31.64 41.13 43.24 41.84 41.13 39.02 37.97 37.97 36.91 35.16 35.16 33.05 4800 31.64 41.13 43.95 41.84 41.13 39.02 37.97 37.97 36.91 35.16 35.16 33.05 MAP
There’s no preset tables in the sniper besides what it creates with the timing numbers that you input, the first table is what the sniper created with my given numbers, I couldn’t see any table if you posted one. I have been doing more digging and came across this thread http://www.gearhead-efi.com/Fuel-Inj...ming-questions and def picked up some stuff to do with just the base sniper inputs, my WOT timing is a bit high is what I’m gathering. I was even wondering how the table in post #7 looks. And I’m also gonna study the link in post #8 of that same thread to try and make some more sense of the whole thing, this is some tricky stuff for me especially being my first ever😂
It definitely can be tough. I don't believe the sniper does a great job creating timing tables. What you want is more advance with less load and more advance with a colder engine.Originally Posted by Sauce
I edited the post above so the table should show now.
Yup that edit fixed the table, I did put down the one table from the #7 post I mentioned into the sniper software cause I had someone say that should be a good starting point, my header gasket gave out so I ordered new gaskets and also the 8.5mm plug wires the sniper recommends for the hyperspark system so when those come in I’ll try out this out, I’ll also try getting ur table put in a different file, is that all the timing cells you had with cpu, the sniper tables have twice as much rows and columns leading to a much larger tablegearheadEFI random 350 vortec thread timing graph.jpg gearheadEFI random 350 vortec thread timing table.jpg
Last edited by Sauce; 10-17-2023 at 10:48 AM.
after i put in the table from the one thread thats not mine, i went ahead and hit smooth all, then saved it as a separate file so i didnt lose the original, this is after hitting smooth i would imagine the graph should be smooth but i got no clueafter smooth table.jpgafter smooth.jpg
Last edited by Sauce; 10-17-2023 at 11:34 AM.
That table looks like a good start for Vortec heads. It is much smoother than the ones you had posted before. It will probably work well.
So I ran that tune to the shop to put new gaskets and wires on otw back I did a baby ripper buuuuttt I think I lost 3rd gear, so ima check the cable to see if it’s loose or what, if my transmission is screwed then it’s still under warranty hopefully the shop will go thru with it, I haven’t checked the datalogs bc I’m really scared ab the trans, I’ll look tho and report my findings
i did indeed lose 3rd gear due to my bracket flexing and heres an update i posted on another thread: ok yall believe it or not im still on this lol. my tranny shop has had the truck since late November doing a throttle bracket for it... the builder wanted to check over the truck to make sure the tranny didn't get smoked again and he found out that my bracket that holds the tv cable was flexing when i hit the gas causing the tranny to get smoked, the only good things that has come from this ordeal is i got a faster laptop, a job towing and my new boss has tons of connections, he knows a few sniper guys that ill be working with. that is whenever i get the truck back, got stuck with a beater this winter and a work van for the last bit of it
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