kPa to PSI quick reference list

When converting on a boosted application using the M.A.P. sensor reading's the first 100 kPa will be subtracted. In other words if your highest reading is 107 kPa, when doing the equation / conversion you would actually have a reading of 7 kPa which would equate to 1lb of boost pressure when converted to PSI. I know this is a pretty simple equation that most of you have in your heads and or use one of many conversion calculators that are available on the Internet but I figured I'd post this as a quick reference. Anyway, here's the quick reference chart.

kPa PSI
107 1.01
114 2.03
121 3.04
128 4.06
135 5.07
142 6.09
149 7.10
156 8.12
163 9.13
169 10.00
176 11.02
183 12.03
190 13.05
197 14.06
204 15.08
211 16.09
218 17.11
225 18.2
232 19.14
238 20.01
245 21.03
252 22.04
259 23.06
266 24.07
273 25.09
280 26.10
287 27.12
294 28.13
300 29.00
306 30.02

Here's calculated boost levels using the X axis (engine speed RPM)
And Y Axis Manifold Absolute Pressure (kPa) as seen in an HP Tuners Histogram.

I'll start at 105 kPa since 100 and lower numbers on the histogram are not relevant as it pertains to boost pressure.

kPa PSI

105 .725
110 1.45
115 2.17
120 2.90
125 3.62
130 4.35
135 5.07
140 5.80
145 6.52
150 7.25
155 7.97
160 8.70
165 9.42
170 10.15
175 10.87
180 11.60
185 12.32
190 13.05
195 13.77
200 14.50
205 15.22
210 15.95
215 16.67
220 17.40
225 18.12
230 18.85
235 19.58
240 20.30
245 21.03
250 21.75
255 22.48
260 23.20
265 23.93
270 24.65
275 25.38
280 26.10
285 26.83
290 27.55
295 28.28
300 29.00
305 29.73
310 30.45

 

I just wanted to take a second to update this thread and add some Air/Fuel (EQ) Equivalence Ratios. These "Equivalence Ratios" are used in HP Tuners in various tables such as Power Enrich EQ Ratio vs. RPM (which is the primary table used for WOT fueling calculations) These same EQ Ratios are used in the Boost Enrichment vs. MAP table as well. The PCM will use which ever table is richer between this one and the Power Enrich table for WOT fueling. Boost Enrichment vs. MAP table is useful when determining fueling calculations in situations where boost does not always correlate to engine RPM.

To calculate the commanded AFR based on the Equivalence Ratio you simply take the Stoichiometric Air to Fuel Ratio of 14.7 : 1 and you divide it by the Equivalence Ratio and that will yield the commanded Air fuel ratio for the given cell in HP Tuners. Most of you who tune already know this the idea here isn't to teach something but rather just give a quick reference. The larger the EQ Ratio the Richer the Air/Fuel Ratio will be.

For the purpose of this post, I will give AFR and the appropriate EQ ratios for AFR's ranging from 14.7 : 1 to 9.0 : 1 heading in the rich direction in 1/2 point increments starting from stoich. I will error toward the rich side of the number for each calculation.

For those who don't know, these EQ Ratios are also what's called units of Lambda. I personally think this is why you will see some tuners who prefer to tune using wide-bands that measure in units of lambda because, its easier and you know that lambda 1 is stoich and you don't have to really do as much math. Not that there's a lot to do either way.

I want to post up some cool videos with some good tuning tips and tricks. however, I'm trying to get permission from the owner before I do that. I'm still waiting on that.

AFR EQ RATIO
14.7 : 1 1.000

14.5 : 1 1.014

14.0 : 1 1.048

13.5 : 1 1.089

13.0 : 1 1.130

12.5 : 1 1.176

12.0 : 1 1.225

11.5 : 1 1.278

11.0 : 1 1.336

10.5 : 1 1.400

10.0 : 1 1.470

9.5 : 1 1.547

9.0 : 1 1.633

 

Looks like some great info here buddy. Robert

 

Ok, so I made this and wanted to share. I intended on posting it in this thread initially so here it is.

EQ Ratio, Lambda and AFR Calculators.xlsx

 

I'm glad this thread is back!

Thanks!