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I'd rather do it myself
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Discussion Starter #23 (Edited)
Here's a break down of the temp readings and the actual ohm readings. I'm going to mount the sensor and connect it to an ohm meter and drive around a while comparing the readings to the OEM temp sensor before splicing it into the MAP wiring.

Here's the Hyundai specs for the IATS.

°C___°F___kΩ

-40(-40) 40.93 ~ 48.35

-20(-4) 13.89 ~ 16.03

0(32) 5.38 ~ 6.09

10(50) 3.48 ~ 3.90

20(68) 2.31 ~ 2.57

40(104) 1.08 ~ 1.21

50(122) 1.56 ~ 1.74

60(140) 0.54 ~ 0.62

80(176) 0.29 ~ 0.34


2.2K Thermistor Output Table

°F___°C___Ohms
-7 -21.67 24063
-5 -20.56 22552
-3 -19.44 21134
-1 -18.33 19826
1 -17.22 18607
3 -16.11 17471
5 -15.00 16412
7 -13.89 15424
9 -12.78 14502
11 -11.67 13641
13 -10.56 12837
15 -9.44 12079
17 -8.33 11376
19 -7.22 10719
21 -6.11 10104
23 -5.00 9529
25 -3.89 8989
27 -2.78 8484
29 -1.67 8011
31 -0.56 7566
33 0.56 7146
35 1.67 6755
37 2.78 6388
39 3.89 6043
41 5.00 5719
43 6.11 5414
45 7.22 5128
47 8.33 4858
49 9.44 4605
51 10.56 4364
53 11.67 4139
55 12.78 3927
57 13.89 3727
59 15.00 3539
61 16.11 3361
63 17.22 3194
65 18.33 3035
67 19.44 2886
69 20.56 2743
71 21.67 2610
73 22.78 2484
75 23.89 2365
77 25.00 2252
79 26.11 2145
81 27.22 2044
83 28.33 1949
85 29.44 1858
87 30.56 1771
89 31.67 1690
91 32.78 1613
93 33.89 1540
95 35.00 1471
97 36.11 1405
99 37.22 1342
101 38.33 1283
103 39.44 1226
105 40.56 1172
107 41.67 1122
109 42.78 1073
111 43.89 1027
113 45.00 983
115 46.11 942
117 47.22 902
119 48.33 864
121 49.44 828
123 50.56 794
125 51.67 761
127 52.78 730
129 53.89 700
131 55.00 672
133 56.11 645
135 57.22 619
137 58.33 595
139 59.44 571
141 60.56 549
143 61.67 528
145 62.78 507
147 63.89 488
149 65.00 469
151 66.11 451
153 67.22 434
155 68.33 418
157 69.44 402
159 70.56 387
161 71.67 373
163 72.78 359
165 73.89 346
167 75.00 333
169 76.11 321
171 77.22 310
173 78.33 299
175 79.44 288
177 80.56 278
179 81.67 268
181 82.78 259
183 83.89 250
185 85.00 241
187 86.11 233
 

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Jedi Master
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Soi was thinking... anyone think that maybe the slow acting IAT is a double bladed sword? Ok it doesn't tell our ECU that the air is cool fast enough to advance timing BUT! it also doesn't tell our ECU the air got warmer say during idle after a hard pull
 

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I'd rather do it myself
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18,614 Posts
Discussion Starter #25 (Edited)
I don't think it makes any difference unless you are opening the throttle. IMHO it's the tip in and the WOT areas that this makes a difference. The tip in will happen way before the OEM IAT sees any temp change and there for bases timing on the slow IAT reading. This will cut it more than it should for peak power.

At WOT I think it is more important as this will be for a 5-10 second period. I want to see what the timing drops to when I mash the gas at about 2500 rpm and 4th gear.

Here's a graph of a Mazda OEM IAT compared to the Triumph 955 one.

 

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I'd rather do it myself
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Discussion Starter #26
It's installed

So I put it in. Realtively easy to do as far as mounting. It is not yet connected to the ECU. I'm waiting to get some test done on the road first.

First I took off the TB so I could get in there to clean it up and to see where the senor ended up when installed.

Using a paper towel I laid that in there to catch any chips from the m10-1.25 tap.





As stated earlier what is stock is a British Standard Taper Pipe thread of 1/8"-28, very similar to the NPT of 1/8"-27. It is the same size drilled hole as the m10 1.25 tap when drilling a new hole. Being that it is a tapered thread then at the bottom of the tap there would be some new metal to cut threads into.

Then put a bit of thread sealant on the sensor.



Here's a shot of the MAP and the new IAT with my test probe from inside the manifold.



Then I connected an ohm meter to the new IAT, got my OBDII reader and the temp test probe reader all together so I could monitor them as I started it up and let the engine heat up. I let it run for 30 minutes to get everything as hot as it normally would be under idle conditions.

What I saw was the OEM IAT and the new one were very close as best I could tell with the OEM IAT having such a broad rage before changing to the next temperature reading. The new IAT changed rapidly and smoothly, I assume the OEM one is too, what the ECU does internally IDK. The test probe was always off and when guesstimating the temp reading from the ohm treading the new one read a couple degrees hotter, as did the OEM IAT.

Here it is from the top installed. It takes a pigtail just like the stock BOV solenoid uses.

 

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Jedi Master
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6,461 Posts
dude thats nuts....
 

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I'd rather do it myself
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Discussion Starter #28
As expected the new IAT when going WOT the resistance drops quickly 200-300 ohms, within 2 seconds. In ~10 seconds the temps starts to rise again. None of this is show by the OEM IAT.

So the next thing to do, and actually what I should have done first, is see how fast the OEM IAT reacts at the sensor. I have a feeling the ECU is only pulling data from the IAT ever 30 seconds or so which may be the cause of the data lag. If the OEM IAT at the connector reacts as fast as the 955 one then that is the case.
 

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Good work bud! Very interested to see how quickly the OEM IAT sensor reacts before the ECU gets its hands on the data.
 

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I'd rather do it myself
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Discussion Starter #30
Yes I just need to figure out how to do that. I'm thinking of connecting both up to the ECU input wire with a double throw switch so I can switch them on the fly to see if there is any difference.

It's really hard to declare any accuracy as to the actual temperature numbers at this time. There may be corrections added to the OEM signal in the ECU logic.
 

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Yes I just need to figure out how to do that. I'm thinking of connecting both up to the ECU input wire with a double throw switch so I can switch them on the fly to see if there is any difference.

It's really hard to declare any accuracy as to the actual temperature numbers at this time. There may be corrections added to the OEM signal in the ECU logic.
I think at the very least if a particular temperature equates to an equivalent voltage figure for both sensors you've got a pretty good start. If the ECU isn't contributing to any meaningful delay and the response issue is tied to the sensor this research can help quite a bit. If the delay is a result of ECU programming then we're a bit screwed.
 

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Jedi Master
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6,461 Posts
Question, this wasn't asked yet, but does anyone know if the ECU can even read the signal, plug it into w/e map or formula it has to determine timing with all the other factors it considers for determining timing, and then send out the signal to adjust timing THEN for the cams to actually change, in time before the charged air is already burnt and coming out the exhaust side?

Has anyone considered the reason hyundai did this, and most other companys, is because the temp gauge isn't limiting the ecu timing control but that the ECU is it's own limit and the temp gauge is built to at the level of the ecu vs being over kill? I'm sure Haltech might be different but we are talking just stock ECU.
 

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I'd rather do it myself
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18,614 Posts
Discussion Starter #34
Soi was thinking... anyone think that maybe the slow acting IAT is a double bladed sword? Ok it doesn't tell our ECU that the air is cool fast enough to advance timing BUT! it also doesn't tell our ECU the air got warmer say during idle after a hard pull
If I go WOT the air coming in is near ambient so it is denser than what the IAT is saying. More air needs more fuel which can take more timing.

If the IAT is saying the air is hotter than ambient and you are not using a lot of throttle there really is little change in the temp but once again the air coming is is denser than what the IAT is saying.

It's really a short window that this would benefit, say 10 seconds total. I don't think it would help with part throttle tip in as there just is not that much air that comes in. But at WOT and 15 lbs of boost there is alot of air coming in.
 

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Jedi Master
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SO i'm ganna add another curve ball. For people running super big IC's, garret turboxs, isn't it possible that the ECU can learn and expect cold air vs stock IC hot air? So really a accruate thermostat might help the ECU learn better?
 

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Yes I just need to figure out how to do that. I'm thinking of connecting both up to the ECU input wire with a double throw switch so I can switch them on the fly to see if there is any difference.

It's really hard to declare any accuracy as to the actual temperature numbers at this time. There may be corrections added to the OEM signal in the ECU logic.
There is corrections in the ecu logic much the same as the ambient sensor, in its raw state the iat is pretty fast acting but heat soak is an issue. At first I considered just welding on a map flange pre throttle body but noticed that once you started getting pass the 350?? mark ,the throttlebody started to become a restriction causing inaccurate pressure readings.
At the end of the day the DIY that is floating around for the IAT relocation is the best option for most, as it reads correct intake temp without the heatsoak.
The biggest benefit you would get from this is when your Drag racing and you only have seconds for it to adjust, it would also help with hot start issues as the actual IAT temp would be within the tables parameters when shut off.
 

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I'd rather do it myself
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18,614 Posts
Discussion Starter #37
SO i'm ganna add another curve ball. For people running super big IC's, garret turboxs, isn't it possible that the ECU can learn and expect cold air vs stock IC hot air? So really a accruate thermostat might help the ECU learn better?
I don't think the ECU learns to expect cold air, it just acts on the actual value reported.
 

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I'd rather do it myself
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18,614 Posts
Discussion Starter #38
There is corrections in the ecu logic much the same as the ambient sensor, in its raw state the iat is pretty fast acting but heat soak is an issue. At first I considered just welding on a map flange pre throttle body but noticed that once you started getting pass the 350?? mark ,the throttlebody started to become a restriction causing inaccurate pressure readings.
At the end of the day the DIY that is floating around for the IAT relocation is the best option for most, as it reads correct intake temp without the heatsoak.
The biggest benefit you would get from this is when your Drag racing and you only have seconds for it to adjust, it would also help with hot start issues as the actual IAT temp would be within the tables parameters when shut off.
I suppose that is a good work around though it leads to unduly rich conditions when the intake is hot. And it would not be accurate when in closed loop as the intake air is what the IAT is saying at that time.

First and foremost before anyone does that or this mod is to endure you have already done as much as possible to prevent he heat soak.

It's like running the AC at the drag strip otherwise
 

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Jedi Master
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I don't think the ECU learns to expect cold air, it just acts on the actual value reported.
i'm sure your right about the timing part, but it has been established that it does modify it's long term fuel trim based on it's experience. Wouldn't it learn to add more fuel at high RPM if EVERY TIME it goes WOT it gets hit with close to ambient air?
 

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weird that the oem one in encased in plastic
on my srt-4 the one for ambiant air was but the IAT one the sensor was not encased...so you you could fast temperature change
 
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