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You might be surprised to learn all the benefit of full sequential is at low load like putting around, but the difference isn't worth the fuss and hardware cost if you don't already have the hardware for it.
You might be surprised to learn all the benefit of full sequential is at low load like putting around, but the difference isn't worth the fuss and hardware cost if you don't already have the hardware for it.
Good luck!
I know a harness for all injectors, what else? Crank trigger I’m guessing.
I know a harness for all injectors, what else? Crank trigger I’m guessing.
Per-injector output drivers to go with the harness, and a version of megasquirt hardware that has enough I/O for all of them. Yes a crank trigger and you also need a cam trigger.
Per-injector output drivers to go with the harness, and a version of megasquirt hardware that has enough I/O for all of them. Yes a crank trigger and you also need a cam trigger.
Can you not use the Hall effect in the distro for the cam signal?
If you haven't found it yet, try 99Hz on the PWM valve setting. I haven't changed that from my base tune setting for my 351W, and it has worked fine. The sequential injection for the PiMPx required opening the harness and cutting and splicing the injector wires. It wasn't as bad as I figured it would be, considering I hate electrical work, but it probably isn't worth it if you aren't after the extra fuel economy. Batch fire and sequential will end up making about the same amount of power.
Numbers under squirts are AFR. I didn’t scale ve table between changes in dead times in case that matters. Reading those, if I understood you correctly, my dead time with be .8? It’s not a typo about the dip at 4 squirts.
@rwfid that’s what I’ve been running the past few days actually. Same stupid problem!
In case this helps anyone, I changed idle back to open loop because why not.. no more oscillation at all. I know it’s not the fix. Rpm’s drop about 75 with ac on, but I can just bump up target rpm to adjust if needed.. again, thank you all who have helped!!
I may download the base tune in a separate project and compare settings to see if something got real screwy when first seeing it up. My buddy was retrying to help me get the ac idle up to even work when I first set it up. Fatal flaw on my part was I had to redo idle stop screw and didn’t recalculate the tps.. once I did that, it magically started working haha! I’d always had the oscillation though. Between lawns or back home is less than 5 minutes so ac rarely got used. Now, my two oldest kids are within 4.5 hr drives compared to 7 hr flights. I know most of the driving out won’t matter, but once I get closer and in towns, I don’t want the damn thing bouncing 400-500 rpm. I had it working within 100 rpm bounce, but alas, that left.
They are attached, I could see how they would be helpful!
Truck is bone stock bottom 302. E7s milled to 57cc and home ported, 31-255-5 cam with 1.72 scorpion rollers. I also have an msd 6a box, 19 lb 4 hole Bosch injectors.
Last edited by 90project5.0; Apr 25, 2026 at 02:20 PM.
Numbers under squirts are AFR. I didn’t scale ve table between changes in dead times in case that matters. Reading those, if I understood you correctly, my dead time with be .8? It’s not a typo about the dip at 4 squirts.
@rwfid that’s what I’ve been running the past few days actually. Same stupid problem!
In case this helps anyone, I changed idle back to open loop because why not.. no more oscillation at all. I know it’s not the fix. Rpm’s drop about 75 with ac on, but I can just bump up target rpm to adjust if needed.. again, thank you all who have helped!!
I may download the base tune in a separate project and compare settings to see if something got real screwy when first seeing it up. My buddy was retrying to help me get the ac idle up to even work when I first set it up. Fatal flaw on my part was I had to redo idle stop screw and didn’t recalculate the tps.. once I did that, it magically started working haha! I’d always had the oscillation though. Between lawns or back home is less than 5 minutes so ac rarely got used. Now, my two oldest kids are within 4.5 hr drives compared to 7 hr flights. I know most of the driving out won’t matter, but once I get closer and in towns, I don’t want the damn thing bouncing 400-500 rpm. I had it working within 100 rpm bounce, but alas, that left.
Based on that yes 1ms is clearly too much. .8 and .9 both have outliers but since 1ms is obviously too much I think .8 is closer to right than .9. If you want to complete the analysis you keep going down to .7 and .6 etc and you should see the leaning effect opposite the rich effect that you see here. Then imagine plotting that rich effect and then the leaning effect on a curve and you'll have something that looks like a y=x cubed plot except instead of being flat at 0 it will be flat at whatever your proper dead time is. So, you have the going rich side of this as x (deadtime) increases y (AFR) goes richer. You can do the lean side too, but, .8 is probably fine.
However, it looks like you're probably already too lean to really go leaner so you'd need to fatten up the VE table first.
Based on that yes 1ms is clearly too much. .8 and .9 both have outliers but since 1ms is obviously too much I think .8 is closer to right than .9. If you want to complete the analysis you keep going down to .7 and .6 etc and you should see the leaning effect opposite the rich effect that you see here. Then imagine plotting that rich effect and then the leaning effect on a curve and you'll have something that looks like a y=x cubed plot except instead of being flat at 0 it will be flat at whatever your proper dead time is. So, you have the going rich side of this as x (deadtime) increases y (AFR) goes richer. You can do the lean side too, but, .8 is probably fine.
However, it looks like you're probably already too lean to really go leaner so you'd need to fatten up the VE table first.
.8 is the spot. .7 just kept leaning out like you said. I did boost the ve table first. Thank you for that lesson! Soon, I’ll be putting bigger injectors so this valuable lesson will be put to work! I did a quick scale to get throttle snaps (while parked) within range to be able to drive and tune later! Thank you!!
Just one quick suggestion and I have to run for a bit. Try targeting mid 13s on your idle. Batch fire doesn't like running lean at idle.
I don’t call things successful until I’ve driven multiple days to account for any variations. Fattening up the idle area might be a good part of the ticket as well. I put it about 13.1-13.3, I don’t get the drop in rpm’s, it didn’t go out of closed loop nor did it oscillate at all. Now, what she loves to do is make me think she’s better and then throw a fit, we shall see!
Throttle snapped a few times and didn’t get the big dip either. Turned truck off and back on a few times, still the same, so thank you for that!! I knew batch prefers richer just from tuning and feeling how the truck drives.
I am always happy to get knowledge from others!
Last edited by 90project5.0; Apr 25, 2026 at 04:27 PM.
Glad to see that helped. My truck still does strange things on occasions, but I have a bad habit of not leaving well enough alone (probably because I know that I still have a lot to learn).
It looks like you may have run autotune on your fuel table. Don't let it tune your idle area, because it doesn't tend to do a very good job. I used to calculate changes to my table with a spreadsheet, but I have figured out how to make custom fields in MegaLogViewer to do it instead. Try smoothing out the peaks and valleys after you run autotune. If you select an area of your 2D table or the whole table, you can right click and select "Smooth Cells" or simply type "s" on your keyboard.
MASSIVE THANK YOU TO ALL THAT HELPED!!! A quick question being focused on one thing taught valuable lessons in other areas as well!
@seijirou you’re detailed instructions got me set up at .8 dead time with 4 squirts. I will revisit this when I put larger injectors soon with a head swap.
@wwhite and @rwfid your instructions on the IAC setup as well as working on the VE table dialed that sweet spot in perfectly. I had a full days worth work in stop and go driving with ZERO oscillation (ac on). I would even turn the AC off and back on at stop signs, nothing! Not even the initial hit on rpm’s.
All of this tuning and she runs harder and stronger than ever before!! First time a rolling launch broke loose on dry pavement. I know she was capable haha!
I used that smoothing option on the ve table, that worked well keeping the AFR pretty steady throughout the rpm range (how I set my AFR table anyways). Nifty tool!!
Anyone that by chance ever deals with megasquirt/tunerstudio in the future and not using pimpx, 92hz is a good spot like @rwfid stated.
Any of you find yourself near Athens GA, let me know!
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