Injection timing help w/ cam

[itsdaveonline]

So long story short, i've been learning tuning because my first "tuner" was incomptent. I brought my car to a 2nd tuner and my tune is much better but still not perfect. Both MAF tables are ironed out, and the timing table has been massaged very well. SD / VE stuff was not tuned, so ill just configure to use MAF only for now.

I noticed neither tuner changed my injection timing. It's still at stock values. Is there a spreadsheet somewhere to help me dial in the proper values for my injector boundary table? I'll post up my entire cam card if someone can give me some calculation tools or support on ballpark figures.

I have some idle / low RPM surging, but i'm guessing I should tune the injector timing prior before chasing the issue w/ throttle follower edits? Will the MAF curve have to be re-adjusted again after the Injector changes?

2006 ctsv, e67, longtubes + cam. Stock ls2.

[MikeOD]

If you zero out the RPM rise table, and then adjust the ECT table...set it to something like 195-200 at operating temp...I don't see it on the cam card, but if you had advertised duration instead of just at 0.050 I could calculate it better. I've been using a formula that was posted on the EFILive forum, and it works great...just that HPTuners references the table differently, so you have to divide his final number by 2 to get the same results.

https://forum.efilive.com/showthread...l=1#post211411

[itsdaveonline]

I'm not seeing any comments on that link saying "Here's the formula you need"... I've read through thousands of other threads on here and im still left baffled on how to calculate the correct injector timing for my new cam. Most everything I've read is gen3 related?!

[MikeOD]

The very first post in my link (my link jumps to post 260), divide advertised duration by 2, subtract that from the intake centerline, swap the negative sign add 360 to get to TDC, then add another 10 to put the fuel on the back of the valve...then like I said, divide that by 2 for HPTuners...leave it alone for EFILive...then if you scroll down on the same thread to post 269 (my post) you'll see I laid out the math for my cam. B1206 in the EFILive system is the RPM table in HPTuners to zero out, and B1205 is the ECT table where you enter the math into the normal operating temp...anything lower than that math, just set it to the same value, anything higher, I leave alone.

I don't know the advertised duration on your cam, but your intake centerline is within 1 degree of mine, and your intake duration at 0.050 is also within 1 degree...my cam is 226 on the intake with a 110 (109.6) ICL...yours is 227 on a 109...so the math will be basically the same.

So that said, I think you should zero out the RPM rise table, then go into the ECT table, under Engine - Fuel - Injector Control - Injection Timing - Normal ECT, and make it look like the attached picture. Leave the boundary table at 520.

EOIT.jpg

[MikeOD]

After you do that, you'll need to touch up the VE and MAF, especially at low RPM near idle...it'll change.

[itsdaveonline]

Ok im at work. But i found some funky calculator spreadsheet. After running through it appears i can just add approx 7.7 degrees to the boundary values. Does that sound about right?

[MikeOD]

I've never had good results touching the boundary table...but that's a minor adjustment to keep it relative to what GM did with it stock...I've found that putting it on the back of the intake valve works the best. It's amazing how much it helps smooth the engine out and clear up the smell at idle.

[itsdaveonline]

Thanks mike. I didn't see your posts earlier. So i called tick performance, and got the advertised duration of my cam @ .006. I was told 279 / 286.... So let me break down my figures per your formula

(advertised duration /2)
279 / 2 = 139.5

(subtract 139.5 from intake center line)
109-139.5 = -30.5

(swap negative sign)
30.5

(add 360 to get TDC)
30.5 + 360 = 390.5

(add 10 to put fuel on the back of the valve)
390.5+10 = 400.5

(divide by 2 for HP tuners)
400.5/2 = ~200

----------
EOIT calculations

target operating temp @ idle (stock)
520-110 = 410

target operating temp @ idle (aftermarket cam adj)
520-200. = 320

So my injectors are done shooting @ 320 degrees? That means they are finishing quicker right? So i advanced the injector timing? I thought we wanted to retard so that all the extra atomized fuel doesn't escape during overlap? I read this article explaining why i should retard timing: http://www.hptuners.com/forum/showth...njector-Timing

Feel free to correct me if i goofed up.

[itsdaveonline]

So I found more spreadsheets in this forum, one for GenIV cars. I filled it out and retarded the EOIT in my tune by 25 degrees more than stock. That puts my EOIT within 20 degrees of EVC ATDC. My first impression, is WOW. My surging has almost disappeared so far, and the car seems alot more responsive down low. I can really put around at low RPM without bucking.

Still up for recommendations / thoughts / discussion.

STOCK


MY ADJUSTMENTS

[pganci]

Excuse my ignorance of not understanding, based on your cam calculations you came up with ~200, shouldn't you have put 200 in the Normal EOI Target adder. Where did the 135 come from?

[dcpatters]

Excuse my ignorance of not understanding, based on your cam calculations you came up with ~200, shouldn't you have put 200 in the Normal EOI Target adder. Where did the 135 come from?

200 is the calculation used to subtract from the Injection Timing boundry table, 520-200 = EOIT target (320)?

[pganci]

200 is the calculation used to subtract from the Injection Timing boundry table, 520-200 = EOIT target (320)?

Sorry but I still don't see the where the 135 comes from in the math to put in the EOI Target Adder. Below is the math on my cam, should I use the same settings, I want to understand the calc.

Advertised duration at .006 = 281, centerline = 111

281 / 2 = 140.5
111 - 140.5 = 29.5
29.5 + 360 = 389.5
389.5 + 10 = 399.5
399.5 / 2 = 199.75 ~200

[itsdaveonline]

So my understanding of EOIT = boundary - normal - ect. According to my spreadsheet I posted earlier my exhaust valve close event happens at ~362 degrees ATDC.

What I read is that i want EOIT to be close to the EVC event. Ideally id want my final EOIT calc to equal 362 if i was understanding that right. I think setting the ECT table to 200 with no RPM modifiers would retard my injection timing by 90 degrees which seems a bit much. My other table i think was wrong too, and gave me the placebo effect.

I came up with this new table which retards inj timing by 23 degrees around idle and retards less through the RPM band. Hopefully im closer to the ball park and understanding this correctly. These values should retard the timing to get me CLOSER to EVC. There are also makeup tables, which i don't really understand.

[itsdaveonline]

man my head is spinning. So now im reading that the lower the number on the newer ECM's the more retarded the timing is and the higher the number on the older ones the more retarded it is?

[dcpatters]

I've got mine at ~90 in the higher temps.

[02statesman]

man my head is spinning. So now im reading that the lower the number on the newer ECM's the more retarded the timing is and the higher the number on the older ones the more retarded it is?

Yeah, the Gen3's use reference pulses and work forward from the boundary. The Gen4's use degrees and work backwards from the boundary.

[SultanHassanMasTuning]

I've got mine at ~90 in the higher temps.

cam specs? you needed to advance 20?

[07GTS]

for eoit just work out the deg of EVC and then u would have to add the injection pulse duration to that so it is after the valve is closed, if u just set it to eoit at 362 your injection will finish as the valve closes not after the valve closes so u are still spraying on an open exhaust valve, so it will depend on your pulse duration as to how much fuel u can get in after the EVC and also still with enough time to get into the cylinder, here is a calculator from DSteck that shows u what is going on and what numbers u need to put in it is post #108
http://www.hptuners.com/forum/showth...lculated/page6

[itsdaveonline]

So just an example... but if my injection boundary is 520 and my ECT values are 110. That would mean injection is finished @ 410 degrees right?*

If I modify the ECT values to 200 then i would finish at 320 degrees - meaning the inj timing of 320 degrees is advanced compared to the 410 figure?

[dcpatters]

cam specs? you needed to advance 20?

Duration @ .006 283 301

.050 INT: 8 BTDC 44 ABDC EXH: 62 BBDC 6 ATDC

Duration @ .050 233 248

Lobe Separation 113