Measuring injector latency...
May 14, 2008, 02:46 PM
#16
You are accounting for all the correct elements, but maybe not that much detail is needed for a reasonable estimate. I think the simplification is that the we can assume that the length of time needed to open or close (2 or 4) is relatively small compared to the length of time needed of the injector to respond to the command (1 or 3). If you have a look at my trace in the first post, or look at the video I linked, the kink in the curve is the point where the injector is at full open or full close. The sort of flat spot in front of the kink represents the time spent for the injector to actually open or close. So I think we can say that once the injector begins to open, its very quick and 100% flow is reached virtually instantly once the injector begins to open.
Then can just say that 1+2 = A, and 3+4 = B. A delay in opening (A) requires that we add that much time to our IPW value, but a delay in closing (B) requires that we subtract that much time from our IPW value. The net latency is then A - B, or:
IPW* = IPW + A - B
Then can just say that 1+2 = A, and 3+4 = B. A delay in opening (A) requires that we add that much time to our IPW value, but a delay in closing (B) requires that we subtract that much time from our IPW value. The net latency is then A - B, or:
IPW* = IPW + A - B
May 14, 2008, 03:11 PM
#17
Good info mrfred! I am glad I chose the FIC 1050's as well man, I'm extra excited to get them now!
The only scaling/latency values that I have seen for them are the ones you posted in the other thread...where have you seen others?
The info in this thread is extremely valuable, especially if you start to test other injectors and compare them to 'tested' working setups that people have posted. Simply amazing!
The only scaling/latency values that I have seen for them are the ones you posted in the other thread...where have you seen others?
The info in this thread is extremely valuable, especially if you start to test other injectors and compare them to 'tested' working setups that people have posted. Simply amazing!
May 20, 2008, 08:52 PM
#18
I did some more injector open/close time measurements but this time with the injectors operating under pressure. I was able to put together a closed loop water circulation system with a pressure regulator and pump. (I'll post a pic of the setup tomorrow.) I set it to 43.5 psi, and ran the injectors at 40 Hz. I can say for sure that measuring the latency with the injector under pressure definitely matters. I only had time to measure a stock injector today. Results are below. With the injector under pressure, the open/close times are much different than with no pressure, and the net latency values with the injector under pressure are very close to the stock values. Results are below. Tomorrow I'll measure one of my FIC 1050s, and we'll have some concrete latency values for these beasties.
Code:
stock injectors with stock 6 ohm resistor in series, operating at 40 Hz
unpressurized
circuit voltage time to open (A) time to close (B) meas. latency (A-B) | ECU values
V (ms) (ms) (ms) | (ms)
4.7 2.63 0.80 1.83 | 3.312
7.0 1.62 0.85 0.77 | 1.680
9.4 1.28 0.85 0.43 | 1.032
11.7 1.07 0.85 -0.07 | 0.672
14.1 0.90 0.91 -0.01 | 0.432
16.4 0.83 0.93 -0.10 | 0.264
18.7 0.76 0.93 -0.17 | 0.144
pressurized to 43.5 psi with DI water
circuit voltage time to open (A) time to close (B) meas. latency (A-B) | ECU values
V (ms) (ms) (ms) | (ms)
4.7 4.84 0.73 4.11 | 3.312
7.0 2.42 0.77 1.65 | 1.680
9.4 1.70 0.80 0.90 | 1.032
11.7 1.38 0.83 0.55 | 0.672
14.1 1.19 0.83 0.36 | 0.432
16.4 1.04 0.83 0.21 | 0.264
18.7 0.94 0.85 0.09 | 0.144
Last edited by mrfred; May 20, 2008 at 09:03 PM.
May 21, 2008, 12:09 AM
#20
Mr. Fred this is good stuff!!!
Why did you choose 40hz? Would changing the frequncy change the latency values?
The values you got were pretty close to the ECU listed values. I am curious to see how the 1050's measure out relative to what people are running.
Great work as always
Why did you choose 40hz? Would changing the frequncy change the latency values?
The values you got were pretty close to the ECU listed values. I am curious to see how the 1050's measure out relative to what people are running.
Great work as always
May 21, 2008, 07:29 AM
#21
Gasoline has a density of ~0.74 gr/cm3
E85 has a density of about 0.77 gr/cm3
Water is of course 1 gr/cm3
If anything, using water would slow the injectors more than gasoline making the measured latency values even longer. They are still measuring out faster than the value in the ECU though.
May 21, 2008, 11:06 AM
#24
Here are the measured latency values from my test setup for FIC 1050s:
For comparison, below are some values that I got from people who dialed them in by watching fuel trims. tkklemann's values are pretty close to what I measured. They are consistently about 0.2 ms longer in the voltage range that really matters. I'm going to start with my measured values, but wouldn't be surprised if I have to bump up the latency values a bit. I also plan on changing the 4.7 V scaling to 5.5 V as the FIC 1050s won't even operate at 4.7 V. I may also do what Pd1 did and add rescale to add a value between 11.7 and 14.1 V.
---
someone running FIC 1050s at 56 psi
4.69 4.371ms
7.03 2.427ms
9.38 1.467ms
11.72 1.155ms
14.06 0.963ms
16.40 0.867ms
18.68 0.771ms
---
---
tkklemann running FIC 1050s at 43.5 psi
4.69 3.912ms
7.03 2.304ms
9.38 1.512ms
11.72 1.152ms
14.06 0.816ms
16.40 0.600ms
18.68 0.456ms
---
---
Pd1 running FIC 1050s at 43.5 psi
7.03 1.680
11.72 1.200
12.89 1.152
13.70 0.960
14.06 0.964
16.41 0.504
18.68 0.240
---
---
Code:
FIC 1050 injectors with stock 6 ohm resistor in series, operating at 40 Hz
pressurized to 43.5 psi with DI water
circuit voltage time to open (A) time to close (B) meas. latency (A-B)
V (ms) (ms) (ms)
4.7 no open no open no open
5.5 6.74 0.74 6.00
7.0 4.14 0.78 3.36
9.4 2.38 0.80 1.58
11.7 1.81 0.84 0.97
14.1 1.48 0.85 0.63
16.4 1.29 0.86 0.43
18.7 1.14 0.87 0.27
---
someone running FIC 1050s at 56 psi
4.69 4.371ms
7.03 2.427ms
9.38 1.467ms
11.72 1.155ms
14.06 0.963ms
16.40 0.867ms
18.68 0.771ms
---
---
tkklemann running FIC 1050s at 43.5 psi
4.69 3.912ms
7.03 2.304ms
9.38 1.512ms
11.72 1.152ms
14.06 0.816ms
16.40 0.600ms
18.68 0.456ms
---
---
Pd1 running FIC 1050s at 43.5 psi
7.03 1.680
11.72 1.200
12.89 1.152
13.70 0.960
14.06 0.964
16.41 0.504
18.68 0.240
---
---
May 21, 2008, 01:37 PM
#25
Thanks for the reply from the earlier post.
It would be interesting to know whether or not the 1000,850 and 950's have similar or even same latency values. According to FIC they are all the same core injector modifed and when flow measured labeled accordingly. Well the 850 might be the stock one and the others the modified versions including the 1050's.
Electrically they should be the same os the latencies should be the same but scaling different?
I suppose I could try the values and see if only scaling is different from what others are running with their 1050's
It would be interesting to know whether or not the 1000,850 and 950's have similar or even same latency values. According to FIC they are all the same core injector modifed and when flow measured labeled accordingly. Well the 850 might be the stock one and the others the modified versions including the 1050's.
Electrically they should be the same os the latencies should be the same but scaling different?
I suppose I could try the values and see if only scaling is different from what others are running with their 1050's
May 21, 2008, 05:40 PM
#26
Sorry for my ignorance, but do scaling values have any effect on the latency values? I'm sure the above individuals are all not using the same injector scaling, so if they vary a little, I wonder if they make any difference towards their usable or tuned latency values.
Again mrfred, this is great info.
Again mrfred, this is great info.
May 21, 2008, 05:58 PM
#27
Injector scaling does not affect latency, IPW is affected by both injector scaling and latency. You are correct in that they must be adjusted together. The trick is picking the right combination of latency and injector scaling. Using fuel trims is one way to do it, but as can be seen, there is some variety in the final values, and its pretty difficult to deduce latency values for voltages above 14.1 V and below 11.7 V by driving around watching fuel trims. Its more of a guessing game.
Aug 16, 2010, 06:48 AM
#28
thread resurrection.
In the X code I can see that MUT29/2A is the derived IPW + latency.
Now what I dont understand is why doesn't the ECU just time the opening of the injector AHEAD of when the injector needs to be open, rather than adding the latency?
I guess its the same result anyways..
However what is the flow while the injector is closing? like when the injector is commanded to close (or rather stop being commanded to open) does the injector still flow while its closing?
In the X code I can see that MUT29/2A is the derived IPW + latency.
Now what I dont understand is why doesn't the ECU just time the opening of the injector AHEAD of when the injector needs to be open, rather than adding the latency?
I guess its the same result anyways..
However what is the flow while the injector is closing? like when the injector is commanded to close (or rather stop being commanded to open) does the injector still flow while its closing?
Aug 16, 2010, 07:19 AM
#29
Injectors will flow any time they are open by any amount (flow will be lower during opening/closing), but injectors close much more quickly than they open, and latency is meant to include closing time.
Last edited by mrfred; Aug 16, 2010 at 08:06 AM.