AIT/MAT lower during boost!

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11-07-2007, 09:13 PM

brgracer

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AIT/MAT lower during boost!

I can't find my old logs with the GReddy turbo which showed the same thing, but yet again with my new GT25R setup, my GM open element AIT sensor placed in the middle of my intake manifold (drilled and tapped for sensor) on MS logs shows a dropping manifold air temp in boost. I am assuming that this is due to the increased airflow thru my 18x12x3 IC with the additional speed.

For reference, my AIT sensor correlates with ambient temp on cold startup and then rises to engine bay temp as the car warms up so I know that the sensor is in the relative ballpark of true temps.

On the datalogs, red line is boost and blue line is manifold air temp in celsius. Time and time again, it is reproducible, even after romping on the car around the area for ~20 minutes with lots of boosted runs. Runs were anywhere from 10-15psi of boost on a GT25R which I am sure is putting out a lot of heat at higher psi which makes it ever more impressive. Granted these are relatively short runs around on local roads where there is not much room to stay in boost for long periods of time, so I'm sure heak soak would come into play on the track and on more open roads, but neat nonetheless. Let's see WI do that magna! Ha! :gay:

11-08-2007, 02:12 AM

Savington

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Photos of air filter location?

11-08-2007, 09:15 AM

Braineack

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are your easy therm values you flashed correct?

does it ever get below ambient? your IC should be about 90% efficient, so i can see them dropping if your sensors is heat soaking while cruising....but if they drop below ambient then somethings wrong.

11-08-2007, 11:47 AM

brgracer

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Quote:

Originally Posted by Braineack

No easytherm values as this is for the Air Intake Sensor in the intake manifold not the coolant sensor. I use the open element GM one that DIY autotune sells not the stock air temp sensor.

Also, I never said that they drop below ambient, they just drop in boost rather than staying steady or rising. I've gotten anywhere from a 5-18 degree F drop in AIT while in boost. Like I said, I know my AIT is working fine b/c the startup AIT temp matches ambient within a few degrees and idle AIT roughly matches engine bay temps.

Keep in mind, I was not on the highway so cruising on local roads was ~30-40 mph with boosted runs taking me up upwards of 70-80.

As an example, yesterday was around 55F ambient and my AIT temps after sitting a few minutes at idle were ~105F, then in low speed cruise they were ~95F, and in boost (10-15psi) they would sometimes drop as low as ~80F from the increase in airflow thru the IC at a much higher speed. It doesn't tell you the efficiency of the IC as I don't have a temp sensor pre-IC, but I'm sure the pre-IC temp is much higher than ambient @15psi of boost.

Considering that the AITs in boost are lower than cruise, makes me want to jack up the timing in boost, but I guess I save that for tuning time on the loading dyno to be safe, but I'll definitely consider adding a few degrees extra at dyno day.

Savington, the new air filter (smaller) will be put right behind that NACA duct in the pic, not in the sub-optimal location pictured. Just got the car up and running again so didn't have time to get to that yet.

11-08-2007, 01:20 PM

Braineack

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does your matfactor.ini look like this:

HTML Code:

; gentherm2 v.2.2
;
; GM 121 463 12 sensor data.
; For use with 2490 ohm bias resistor installed at R4.
;
; Known Steinhart-Hart coefficients: A=0.00149032  B=0.00022746  C=1.1639e-07
			; ADC - Temp (dF)
	DB	210T	;   0 - sensor failure.
	DB	475T	;   1 -  435.4
	DB	409T	;   2 -  369.4
	DB	375T	;   3 -  334.8
	DB	351T	;   4 -  311.7
	DB	335T	;   5 -  294.7
	DB	321T	;   6 -  281.2
	DB	310T	;   7 -  270.1
	DB	301T	;   8 -  260.7
	DB	293T	;   9 -  252.6
	DB	285T	;  10 -  245.4
	DB	279T	;  11 -  239.0
	DB	273T	;  12 -  233.2
	DB	268T	;  13 -  228.0
	DB	263T	;  14 -  223.2
	DB	259T	;  15 -  218.7
	DB	254T	;  16 -  214.6
	DB	250T	;  17 -  210.7
	DB	247T	;  18 -  207.1
	DB	243T	;  19 -  203.7
	DB	240T	;  20 -  200.5
	DB	237T	;  21 -  197.5
	DB	234T	;  22 -  194.6
	DB	231T	;  23 -  191.8
	DB	229T	;  24 -  189.2
	DB	226T	;  25 -  186.7
	DB	224T	;  26 -  184.3
	DB	222T	;  27 -  182.0
	DB	219T	;  28 -  179.8
	DB	217T	;  29 -  177.6
	DB	215T	;  30 -  175.6
	DB	213T	;  31 -  173.6
	DB	211T	;  32 -  171.7
	DB	209T	;  33 -  169.8
	DB	207T	;  34 -  168.0
	DB	206T	;  35 -  166.2
	DB	204T	;  36 -  164.5
	DB	202T	;  37 -  162.9
	DB	201T	;  38 -  161.3
	DB	199T	;  39 -  159.7
	DB	198T	;  40 -  158.2
	DB	196T	;  41 -  156.7
	DB	195T	;  42 -  155.2
	DB	193T	;  43 -  153.8
	DB	192T	;  44 -  152.4
	DB	191T	;  45 -  151.0
	DB	189T	;  46 -  149.7
	DB	188T	;  47 -  148.4
	DB	187T	;  48 -  147.1
	DB	185T	;  49 -  145.8
	DB	184T	;  50 -  144.6
	DB	183T	;  51 -  143.4
	DB	182T	;  52 -  142.2
	DB	181T	;  53 -  141.0
	DB	179T	;  54 -  139.9
	DB	178T	;  55 -  138.8
	DB	177T	;  56 -  137.7
	DB	176T	;  57 -  136.6
	DB	175T	;  58 -  135.5
	DB	174T	;  59 -  134.4
	DB	173T	;  60 -  133.4
	DB	172T	;  61 -  132.4
	DB	171T	;  62 -  131.4
	DB	170T	;  63 -  130.4
	DB	169T	;  64 -  129.4
	DB	168T	;  65 -  128.4
	DB	167T	;  66 -  127.4
	DB	166T	;  67 -  126.5
	DB	165T	;  68 -  125.6
	DB	164T	;  69 -  124.6
	DB	163T	;  70 -  123.7
	DB	162T	;  71 -  122.8
	DB	161T	;  72 -  121.9
	DB	161T	;  73 -  121.0
	DB	160T	;  74 -  120.2
	DB	159T	;  75 -  119.3
	DB	158T	;  76 -  118.5
	DB	157T	;  77 -  117.6
	DB	156T	;  78 -  116.8
	DB	155T	;  79 -  115.9
	DB	155T	;  80 -  115.1
	DB	154T	;  81 -  114.3
	DB	153T	;  82 -  113.5
	DB	152T	;  83 -  112.7
	DB	151T	;  84 -  111.9
	DB	151T	;  85 -  111.1
	DB	150T	;  86 -  110.3
	DB	149T	;  87 -  109.6
	DB	148T	;  88 -  108.8
	DB	148T	;  89 -  108.0
	DB	147T	;  90 -  107.3
	DB	146T	;  91 -  106.5
	DB	145T	;  92 -  105.8
	DB	145T	;  93 -  105.0
	DB	144T	;  94 -  104.3
	DB	143T	;  95 -  103.6
	DB	142T	;  96 -  102.9
	DB	142T	;  97 -  102.1
	DB	141T	;  98 -  101.4
	DB	140T	;  99 -  100.7
	DB	139T	; 100 -  100.0
	DB	139T	; 101 -  99.3
	DB	138T	; 102 -  98.6
	DB	137T	; 103 -  97.9
	DB	137T	; 104 -  97.2
	DB	136T	; 105 -  96.5
	DB	135T	; 106 -  95.8
	DB	135T	; 107 -  95.2
	DB	134T	; 108 -  94.5
	DB	133T	; 109 -  93.8
	DB	133T	; 110 -  93.1
	DB	132T	; 111 -  92.5
	DB	131T	; 112 -  91.8
	DB	131T	; 113 -  91.1
	DB	130T	; 114 -  90.5
	DB	129T	; 115 -  89.8
	DB	129T	; 116 -  89.1
	DB	128T	; 117 -  88.5
	DB	127T	; 118 -  87.8
	DB	127T	; 119 -  87.2
	DB	126T	; 120 -  86.5
	DB	125T	; 121 -  85.9
	DB	125T	; 122 -  85.2
	DB	124T	; 123 -  84.6
	DB	123T	; 124 -  84.0
	DB	123T	; 125 -  83.3
	DB	122T	; 126 -  82.7
	DB	122T	; 127 -  82.0
	DB	121T	; 128 -  81.4
	DB	120T	; 129 -  80.8
	DB	120T	; 130 -  80.1
	DB	119T	; 131 -  79.5
	DB	118T	; 132 -  78.9
	DB	118T	; 133 -  78.3
	DB	117T	; 134 -  77.6
	DB	116T	; 135 -  77.0
	DB	116T	; 136 -  76.4
	DB	115T	; 137 -  75.7
	DB	115T	; 138 -  75.1
	DB	114T	; 139 -  74.5
	DB	113T	; 140 -  73.9
	DB	113T	; 141 -  73.2
	DB	112T	; 142 -  72.6
	DB	111T	; 143 -  72.0
	DB	111T	; 144 -  71.4
	DB	110T	; 145 -  70.7
	DB	110T	; 146 -  70.1
	DB	109T	; 147 -  69.5
	DB	108T	; 148 -  68.9
	DB	108T	; 149 -  68.2
	DB	107T	; 150 -  67.6
	DB	106T	; 151 -  67.0
	DB	106T	; 152 -  66.3
	DB	105T	; 153 -  65.7
	DB	105T	; 154 -  65.1
	DB	104T	; 155 -  64.5
	DB	103T	; 156 -  63.8
	DB	103T	; 157 -  63.2
	DB	102T	; 158 -  62.6
	DB	101T	; 159 -  61.9
	DB	101T	; 160 -  61.3
	DB	100T	; 161 -  60.6
	DB	100T	; 162 -  60.0
	DB	 99T	; 163 -  59.4
	DB	 98T	; 164 -  58.7
	DB	 98T	; 165 -  58.1
	DB	 97T	; 166 -  57.4
	DB	 96T	; 167 -  56.8
	DB	 96T	; 168 -  56.1
	DB	 95T	; 169 -  55.5
	DB	 94T	; 170 -  54.8
	DB	 94T	; 171 -  54.2
	DB	 93T	; 172 -  53.5
	DB	 92T	; 173 -  52.9
	DB	 92T	; 174 -  52.2
	DB	 91T	; 175 -  51.5
	DB	 90T	; 176 -  50.8
	DB	 90T	; 177 -  50.2
	DB	 89T	; 178 -  49.5
	DB	 88T	; 179 -  48.8
	DB	 88T	; 180 -  48.1
	DB	 87T	; 181 -  47.4
	DB	 86T	; 182 -  46.7
	DB	 86T	; 183 -  46.0
	DB	 85T	; 184 -  45.3
	DB	 84T	; 185 -  44.6
	DB	 83T	; 186 -  43.9
	DB	 83T	; 187 -  43.2
	DB	 82T	; 188 -  42.5
	DB	 81T	; 189 -  41.8
	DB	 81T	; 190 -  41.0
	DB	 80T	; 191 -  40.3
	DB	 79T	; 192 -  39.6
	DB	 78T	; 193 -  38.8
	DB	 78T	; 194 -  38.1
	DB	 77T	; 195 -  37.3
	DB	 76T	; 196 -  36.5
	DB	 75T	; 197 -  35.8
	DB	 74T	; 198 -  35.0
	DB	 74T	; 199 -  34.2
	DB	 73T	; 200 -  33.4
	DB	 72T	; 201 -  32.6
	DB	 71T	; 202 -  31.8
	DB	 70T	; 203 -  30.9
	DB	 70T	; 204 -  30.1
	DB	 69T	; 205 -  29.3
	DB	 68T	; 206 -  28.4
	DB	 67T	; 207 -  27.5
	DB	 66T	; 208 -  26.7
	DB	 65T	; 209 -  25.8
	DB	 64T	; 210 -  24.9
	DB	 63T	; 211 -  23.9
	DB	 63T	; 212 -  23.0
	DB	 62T	; 213 -  22.1
	DB	 61T	; 214 -  21.1
	DB	 60T	; 215 -  20.1
	DB	 59T	; 216 -  19.2
	DB	 58T	; 217 -  18.1
	DB	 57T	; 218 -  17.1
	DB	 56T	; 219 -  16.1
	DB	 55T	; 220 -  15.0
	DB	 53T	; 221 -  13.9
	DB	 52T	; 222 -  12.8
	DB	 51T	; 223 -  11.7
	DB	 50T	; 224 -  10.5
	DB	 49T	; 225 -   9.3
	DB	 48T	; 226 -   8.1
	DB	 46T	; 227 -   6.8
	DB	 45T	; 228 -   5.6
	DB	 44T	; 229 -   4.2
	DB	 42T	; 230 -   2.9
	DB	 41T	; 231 -   1.5
	DB	 40T	; 232 -   0.0
	DB	 38T	; 233 -  -1.5
	DB	 36T	; 234 -  -3.1
	DB	 35T	; 235 -  -4.7
	DB	 33T	; 236 -  -6.4
	DB	 31T	; 237 -  -8.1
	DB	 30T	; 238 - -10.0
	DB	 28T	; 239 - -11.9
	DB	 26T	; 240 - -13.9
	DB	 23T	; 241 - -16.1
	DB	 21T	; 242 - -18.3
	DB	 19T	; 243 - -20.8
	DB	 16T	; 244 - -23.4
	DB	 13T	; 245 - -26.2
	DB	 10T	; 246 - -29.2
	DB	  7T	; 247 - -32.6
	DB	  3T	; 248 - -36.4
	DB	  0T	; 249 - -40.6
	DB	  0T	; 250 - -45.6
	DB	  0T	; 251 - -51.5
	DB	  0T	; 252 - -58.9
	DB	  0T	; 253 - -68.9
	DB	  0T	; 254 - -85.1
	DB	210T	; 255 - sensor failure.

im really curious. easytherm does both the CLT and MAT resistance values....

11-08-2007, 01:29 PM

cjernigan

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I have a feeling that his intake mani is heat soaking his sensor. I see a temp increase with my GM IAT after my IC. It might stay the same under boost sometimes but it never goes down.

11-08-2007, 01:47 PM

brgracer

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Quote:

Originally Posted by Braineack

does your matfactor.ini look like this:

im really curious. easytherm does both the CLT and MAT resistance values....

Yes, it looks like that, why?

11-08-2007, 01:49 PM

Braineack

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i dunno. its just interesting, trying to see if it's an error or not. but i can see the sensor heatsoaking during cruise and the blast of boost throwing it back inline.

11-08-2007, 01:57 PM

brgracer

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Quote:

Originally Posted by Braineack

i dunno. its just interesting, trying to see if it's an error or not. but i can see the sensor heatsoaking during cruise and the blast of boost throwing it back inline.

Really? Considering that the open air element sensor is into the airstream, I don't understand why placement in the IM vs. an IC pipe would make any difference with constant airflow past the sensor in cruise vs. boost. Granted idle (with the throttle plate closed) vs. cruise might make some sense. I've also heard of people who run WI get a sudden error when a water droplet sticks to the sensor briefly, but again no WI here.

If I had the time, it'd be interesting to get pre-IC and post-Ic temps to measure agains the GM AIT. Hmm.....

11-08-2007, 02:05 PM

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brgracer

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Forget it, I'm a fool. Took a look at some longer logs that I didn't have time to get thru and if you look closer, the AITs either stay flat or rise 2-3 degrees on longer boosted runs. My runs are just too short to show the effect, but between shifts and as the car picks up speed, the AITs drop a bit making it look like they drop in boost. My bad....