Megasquirt Deadtime Calculator
 Share
The version of the browser you are using is no longer supported. Please upgrade to a supported browser.Dismiss

View only
 
 
ABCDEFGHIJKLMNOPQRSTUVWXYZ
1
Source Injector Data:http://siemensdeka.com/specsheets/FI114992cs.jpgAKA: Ford M-9593-LU80seijirou : msextra.com & corral.net forums.
2
Small Pulsewidth Curve (SPC) approach: Megasquirt calculates the linear High Slope (HS) based on injector flow automatically. Megasquirt always assumes the HS is true at any Pulsewidth (PW). The SPCurve provides a corrected PW to use when desired PW is small. Data sheets provide the Low Slope (LS) which is a 2nd linear flow rate between the Break Point and Min PW. The Break Point is reached on the LS flow rate, so a different point must be selected to handoff from the LS to the HS. This is selected as the Break Point + .01, and named High Slope Handoff. All points below the High Slope Handoff map a calculated PW on the HS to the correct replacement PW on the LS based on the fuel mass that the HS would provide, if it were accurate.
Below the Min PW injector characteristics are non-linear. 2 points are used to characterize this, Low Curve Factor 1 (LCF1) and Low Curve Factor 2 (LCF2). These are simply a reduction of the MinPW and should be adjusted to approximate the non-linear injector flow below the MinPW.
3
Go to File -> Make a copy to make changes for yourself! ** Small Pulsewidth Curve is BETA and is probably total garbage! **

This is my attempt to automate dead time settings for Megasquirt 2 and Megasquirt 3 systems using manufacturer's injector data. This was based on Siemens Deka data sheets which are very similar to if not exactly the same as Ford data sheets. This uses the Forecast function to linearize various fuel pressure compensation curves to get a "good" value for a user defined fuel pressure. This is not perfect! This is useable as-is for "good" values. If you are comfortable with spreadsheets you can tweak it for "gooder" values by updating the 4 forecast functions to only linearize across 2 points surrounding your defined fuel pressure. For "best" values use one of the fuel pressures provided on the sheet, and enter the appropriate multipliers directly, replacing the forecast function. This is done for the 4 compensation multipliers in bold below. To understand how far off the forecast function wanders away from best, enter a fuel pressure with a known multiplier and check.
4
5
6
7
8
9
10
Update the values belowCalculated Values *** Expert Modification Only!! ***MS3 Output *** Do Not Modify!! ***
11
12
User SettingsFuel Rate @ Fuel Pressure**BETA** Small Pulsewidth Curve
13
Fuel Pressure39.15lb/hr73.52386733
Low Slope - "New"
High Slope - "Original"
14
cc/min772.0006070 point00
15
Injector CharacteristicsLow curve factor 10.0670880.08577923129
16
Low Slope (lb/s)0.028183
Voltage Offset Multiplier
0.9255743903Low curve factor 20.197670.2527423779
17
High Slope (steady state) (lb/s)
0.020877Compensated Voltage OffsetsMin PW0.5990.7658859937
18
Break Point (lb)0.0000242162.601789611Break Point0.90442897871.156409828
19
Min Pulsewidth (ms)0.59981.644745692High Slope Handoff1.1664098281.166409828
20
101.192139815
21
Voltage Offset111.057005954Dead Time0.7413850866
22
62.811120.9413091549
23
81.777130.8357936744Dead Time Voltage Curve
24
101.288140.74138508668221.85%
25
111.142150.667339135411142.57%
26
121.01712126.97%
27
130.903Low Slope Multiplier0.926565074913112.73%
28
140.801
Compensated Low Slope (lb/ms)
0.0000261133835114100.00%
29
150.7211590.01%
30
High Slope Multiplier0.9782677818
31
Fuel Pressure Low Slope Compensation
Compensated High Slope (lb/ms)
0.00002042329648
32
20.010.7149MS2 Output *** Do Not Modify!! ***
33
30.020.6446Break Point Multiplier0.9755349349
34
39.151
Compensated Break Point (lb)
0.00002361770077Keep the lowest PW that MS will use above this Target Min PW. You'll need to use data logging at low load/low RPM to see the lowest PW used. If it drops below the given value, decrease the number of squirts used.
35
50.031.0402
36
54.961.2271Calculations
37
60.031.2215
PW to Compensated Break Point
0.9044289787
38
Min PW to Comp. Break Point Δ
0.3054289787
39
Fuel Pressure High Slope CompensationTarget Min PW (ms)0.9044289787
40
20.010.717Compensated Fuel Mass @ Low SlopeDead Time
Battery Correction
41
30.020.8722Low curve factor 10.1120.81950356520.09996203415
42
39.151Low curve factor 20.33
43
50.031.1334
44
54.961.18830 point0
45
60.031.1984Low curve low0.000001751894673
46
Low curve high0.000005161832517
47
Fuel Pressure Break Point CompensationMin PW0.00001564191672
48
20.010.7149Break Point0.00002361770077
49
30.020.8756High Slope Handoff0.00003045890717
50
39.151
51
50.031.0843
52
54.961.121
53
60.031.309
54
55
Fuel Pressure Voltage Offset Compensation
56
20.010.7149
57
30.020.6306
58
39.151
59
44.951.0908
60
50.030.9903
61
54.961.1848
62
60.031.2383
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Loading...