Adjusting tune for new injectors
Based on the math I see in the attachments, I get...
Inj. Voltage Offset (volts vs pw adder)
6 3.42
7 2.75
8 2.16
9 1.85
10 1.57
11 1.39
12 1.24
13 1.1
14 0.975
15 0.875
Inj. Flow Rate
This is a little tricky. I'd increase factory 99 injectors by ~240% based on this info. It's saying they flow ~89.8 lbs/hr @ 58psi. But, that slope changes as fuel consumption changes. Therefore, the tricky part is the slope because GM uses the IFR table along with the small pulse adjust table. Using the 240% will bring the 0kPa cell in line....but the rest might be a little steeper. You might find that the higher kPa's are causing a rich condition at light throttle. So, the 98.45 lbs/hr in the 80 kPa cell would need to be increased accordingly and then "fill" the cells inbetween 0 and 80 kPa. Ultimately, it might be some trial and error until you find the right slope in combination with that small pulse adjust table. So, it'd be good to have your tune dialed in as best you can prior to the switch, which will allow you to spend less time on the trial and error.
Min. PW is clearly 0.6 ms. However, it's noteworthy to say that once the total injector pulsewidth falls below 1.7 ms, fueling can become inconsistent. The way our OS works is, it takes that min. pw into consideration once the commanded pw. has been determined. From there, the voltage offset is added. So, if you're at 13 volts, 1.7 ms would be as small as you could go on the final pulse width because the calculated pw of .6 + the voltage offset of 1.1 = 1.7 (if I recall correctly - this is how it works). This also means that it's possible you'll idle pretty rich (assuming a 1.7ms pw at idle is too much) AND if you're in close loop, your fuel trims will drop to their lowest values without affecting your pulsewidth because it's bottomed out.
Inj. Voltage Offset (volts vs pw adder)
6 3.42
7 2.75
8 2.16
9 1.85
10 1.57
11 1.39
12 1.24
13 1.1
14 0.975
15 0.875
Inj. Flow Rate
This is a little tricky. I'd increase factory 99 injectors by ~240% based on this info. It's saying they flow ~89.8 lbs/hr @ 58psi. But, that slope changes as fuel consumption changes. Therefore, the tricky part is the slope because GM uses the IFR table along with the small pulse adjust table. Using the 240% will bring the 0kPa cell in line....but the rest might be a little steeper. You might find that the higher kPa's are causing a rich condition at light throttle. So, the 98.45 lbs/hr in the 80 kPa cell would need to be increased accordingly and then "fill" the cells inbetween 0 and 80 kPa. Ultimately, it might be some trial and error until you find the right slope in combination with that small pulse adjust table. So, it'd be good to have your tune dialed in as best you can prior to the switch, which will allow you to spend less time on the trial and error.
Min. PW is clearly 0.6 ms. However, it's noteworthy to say that once the total injector pulsewidth falls below 1.7 ms, fueling can become inconsistent. The way our OS works is, it takes that min. pw into consideration once the commanded pw. has been determined. From there, the voltage offset is added. So, if you're at 13 volts, 1.7 ms would be as small as you could go on the final pulse width because the calculated pw of .6 + the voltage offset of 1.1 = 1.7 (if I recall correctly - this is how it works). This also means that it's possible you'll idle pretty rich (assuming a 1.7ms pw at idle is too much) AND if you're in close loop, your fuel trims will drop to their lowest values without affecting your pulsewidth because it's bottomed out.
Thread Starter
TECH Fanatic
Joined: Oct 2011
Posts: 1,356
Likes: 2
From: Felton Pa
WOW... I usually pride myself on being a fairly intelligent guy, I built a pretty complex turbo setup, but all this tuning stuff is throwing me for a loop. I am a master ASE certified tech and work on this crap all day long, but all the charts are making my head hurt, I think I will just pay the tuner.
is this for the forced induction car or the NA car? do you have a MAP referenced FPR on the boosted car if this is that application?
also, these are likely tested with n-heptane, and it actually says n-heptane, so:
Racetronix details: "Injector flow rates are based on testing with n-Heptane test solvent (0.6855 g/ml). U.S. EPA emission test gasoline 40CFR86.113 (0.735g/ml) flows in most common injector designs at about a 3 to 4% higher rate than n-Heptane. A ratio of 1.035:1 can be used when converting the flow specifications above."
damn thats hard to interpolate the data into all of our tables.... at least the IFR table should be:
they are 80LB/hr @ 3 bar (43.5psi) so they are 92.38LB/hr at 4 bar (58psi) and multiply those values by 1.035 .... so this value plus your negative vacuum will yield values + 92.38 at maximum, in other words your highest value will be above 92.38 at WOT as mentioned above (maximum vacuum, or 101.325kpa) if you are boosted and have a MAP referenced fuel pressure regulator then your entire IFR table should be 92.38 if you are running a MAP referenced FPR***
80LB/hr * 1.035 @ 43.5psi = 82.8
92.38lb/hr * 1.035 @ 58psi = 95.61
that can solve your IFR table... the pulsewidth as mentioned above makes complete sense, and I'm betting you will be around a 1.4~1.5msec pulsewidth (won't go less than 1.7 though) and at that point you may run slightly rich, but I don't think it will be that bad... have to calculate the fuel grams per injector pulse
also, these are likely tested with n-heptane, and it actually says n-heptane, so:
Racetronix details: "Injector flow rates are based on testing with n-Heptane test solvent (0.6855 g/ml). U.S. EPA emission test gasoline 40CFR86.113 (0.735g/ml) flows in most common injector designs at about a 3 to 4% higher rate than n-Heptane. A ratio of 1.035:1 can be used when converting the flow specifications above."
damn thats hard to interpolate the data into all of our tables.... at least the IFR table should be:
they are 80LB/hr @ 3 bar (43.5psi) so they are 92.38LB/hr at 4 bar (58psi) and multiply those values by 1.035 .... so this value plus your negative vacuum will yield values + 92.38 at maximum, in other words your highest value will be above 92.38 at WOT as mentioned above (maximum vacuum, or 101.325kpa) if you are boosted and have a MAP referenced fuel pressure regulator then your entire IFR table should be 92.38 if you are running a MAP referenced FPR***
80LB/hr * 1.035 @ 43.5psi = 82.8
92.38lb/hr * 1.035 @ 58psi = 95.61
that can solve your IFR table... the pulsewidth as mentioned above makes complete sense, and I'm betting you will be around a 1.4~1.5msec pulsewidth (won't go less than 1.7 though) and at that point you may run slightly rich, but I don't think it will be that bad... have to calculate the fuel grams per injector pulse
Thread Starter
TECH Fanatic
Joined: Oct 2011
Posts: 1,356
Likes: 2
From: Felton Pa
Yes, this is for the turbo Chevelle. I am using a Vaccuum referenced Regulator. A1000 fuel system. So I set the Injector Flow Rate vs KPA VAC table to 92.4, I didn't see anything about injector pulse width. I bought this software because I read it was the most user friendly. Not so much.
what are all the tables that require modifying? I thought injector offset v.s. volts v.s. kpa would have been another big one to adjust but you guys didnt mention it. pw makes sense, which pw table do you adjust pw adder or minimum injector pulse or maybe even a diff one?
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Yes, this is for the turbo Chevelle. I am using a Vaccuum referenced Regulator. A1000 fuel system. So I set the Injector Flow Rate vs KPA VAC table to 92.4, I didn't see anything about injector pulse width. I bought this software because I read it was the most user friendly. Not so much.
It's not as complicated as it first seemed. Probably a little more difficult than I made it sound, though. Is this a speed density car?
Also, don't forget to adjust your displacement / cylinder volume in the tune if you haven't already since it's a 4.8L setup...
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