Holley Sniper EFI. Who’s running one, any opinions, tuning?
- Thread starter 1983calais
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I think Zach thought pontiacgp was me asking the question. I’m running the stock fuel line from the front to rear with 3/8 fuel injection hose with -6 an fittings. I am going to play with the timing some. Since I reset the EFI and adjusted my timing it runs much better. I plan on driving it some this weekend and see what happens.
I can't remember if your timing is computer controlled or whether you have an old school HEI, but it doesn't matter so I'm feeling too lazy to go back and read (alot of late nights here as well, and happy about them🙂 ).
When you want to get your timing under control there is an easy way to do it. If you're using an HEI, 1st, unhook and plug the vacuum advance line, 2nd, set the base to 15-18 and the mechanical advance + base, often called 'all in' to 34 degrees at 3000 rpm's. Make sure that 'all in' doesn't get any higher by revving to 4000-4500 rpm's to confirm that it stays at 34. Then go drive it like you stole it and tune your fuel from there. DO NOT tune for highway cruising speeds - YET. Once you get the stumbles, backfires, lean spots, rich spots tuned out of it, then tune the timing for WOT pulls for maximum performance. It might take another 2-5 degrees of 'all in' depending on your cam, compression, car weight, converter slipperyness, etc. Once this is done, now tune the timing for idle, cold and hot startup and highway driving with the vacuum advance.
If your timing is controlled with a computer 2 dimensional table, then do the same across the bottom at every cell below idle Map across the entire rpm range (15ish degrees), and then everything above 3000 rpms to 34 degrees and autoscale down to 1000 rpms or idle speed. In a nutshell, have the timing only change with RPM starting at 15 at idle and ending at 34 at 3000 rpms and above.
If you are unclear, then let me know and I'll attach a pic of a timing table setup like this. Doing this WILL NOT hurt your motor in any way shape or form. It will not get best fuel economy and might not idle at the coolest possible intake and coolant temps, but it will work and will allow you to straighten out your fuel/AFR.
If you can appreciate, the Megasquirt manuals recommend doing this with all auto/self tuning functions turned off so that you can get a base fuel and timing table that doesn't require crazy amounts of correction. The Holley has one thing that makes the selftuning function work better than an MS. I can explain if you'd like, but it might muddy up the waters for what you have going on.
Lastly, and I should have said this earlier, you need to confirm that your TDC mark for #1 is inside of a degree or two of precise. This has to be done on every motor, whether old school carb and points, or an LS7 or modern computer controlled Hemi.
Have you checked the o2 system that tell the computer how much fuel to add sound like it lean
I believe that you said that your O2 sensor was installed in the header collector, Holley recommends that the O2 sensor be installed after the header collector.
Great info 64! This is my next step to experiment with the timing. I believe it is close as it is running better but I will adjust it like you said and report back.
I’m pretty sure that the instructions said in the header collector but I will go back through the book and check.
from the instructions....
"If you have long tube headers, mount the sensor approximately 6-10” after the collector."
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