GaryRudolph

This is to hopefully, get a single thread with a single sensor calibrations for AEM on the S2000. We know particularly that the IAT and ECT sensors are wrong. But the question was how wrong...

On the AEM forums here "westy" did an analysis for the IAT sensor. I believe most people are using this in their calibration. The following shows the discrepancy between the AEM values (FYI, only calibrated from 36F to 210F).



This also passes the common sense check as at 68F outside with a cold car AEM was reporting 20F... Now it reports something closer.

The values are:
Voltage....Temperature (F)
0.............261
0.16.........255
0.31.........241
0.47.........230
0.62.........219
0.78.........210
0.94.........199
1.09.........189
1.25.........180
1.4...........169
1.56.........158
1.72.........147
1.87.........142
2.03.........135
2.18.........127
2.34.........122
2.5...........117
2.65.........109
2.81.........104
2.96.........97
3.12.........90
3.28.........82
3.43.........77
3.59.........73
3.74.........66
3.9...........57
4.06.........50
4.21.........43
4.37.........36
4.52.........28
4.68.........21
4.84.........16
4.99.........10

So, in a similar manner I decided to do this with a newly bought ECT sensor. Thus, move over Lisa, time to do a little sensor cooking in the "lab". Ok, technically, it's just my kitchen, but it worked... FYI, for some reason my wife gave me a lot of crap over doing this... Of course, I guess it is the *only* time you'll catch me in the kitchen cooking



I measured the resistance, and extrapolated this to voltage using the AEM rules documented here . This lead to the following differences (FYI, only calibrated between 32F to 213F).



This also passes the "common sense" check, because I believe it's common knowledge that the AEM reads high by about 15 degrees. Although, it looks more like 20 degrees in the operating temperature range.

And here are the values:
Voltage....Temperature (F)
0.............261
0.16.........246
0.31.........214
0.47.........185
0.62.........165
0.78.........153
0.94.........140
1.09.........131
1.25.........122
1.4...........115
1.56.........108
1.72.........100
1.87.........93
2.03.........88
2.18.........82
2.34.........77
2.5...........72
2.65.........66
2.81.........61
2.96.........57
3.12.........52
3.28.........46
3.43.........41
3.59.........36
3.74.........30
3.9...........27
4.06.........23
4.21.........19
4.37.........16
4.52.........12
4.68..........9
4.84..........5
4.99..........3

Let me know how these work for you. It would be a whole lot easier if we could just compare the ECM settings to voltages across these ranges....

ultimate lurker

Great work Gary, your dedication is impressive.

One thing to note - AEM has said that the sensor cals must be done with appropriate resistance to simulate what the sensor sees from the ECU (I don't know what sort of sensor input the ECU uses). Now, we know the IAT is far enough off to be worth correcting, but given the measurement differences, I wonder if the coolant temp readout might be pretty close, even though it looks skewed based on the measurements in the "lab".

UL

vapors2k

[QUOTE]Originally posted by ultimate lurker
Great work Gary, your dedication is impressive.

One thing to note - AEM has said that the sensor cals must be done with appropriate resistance to simulate what the sensor sees from the ECU (I don't know what sort of sensor input the ECU uses).

GaryRudolph

So you're thinking right now that with the added resistance in the line that the AEM tables may be right? I was under the impression that we were sitting about 15 degrees high in the 175-200's.

But, this is missing the line resistance, as well as the voltage is approximated using AEM's EMS Volts = 5.00 * ( Resistance / ( Resistance + 2,200 ) ). So, it's most likely reading a little low.

AndyDoh

Sorry guys I'm just subscribing as I ordered my EMS yesterday and I'm gonna need all the help I can get, so the more info the better

great research Gary

ANdy

cbender

I've been puzzling over the issue of sensor calibrations for seven months now, and I'm still unsure what to conclude or what to do.

AIT Calibrations: I switched to Westy's AIT calibration table (thanks Westy) and came to the same conclusion as Gary -- after leaving the car sitting overnight, my EMS-reported air temperature (using Westy's calibration table) is more or less the same as that reported by my indoor/outdoor thermometer for the inside of my garage. Before, they were far lower, which obviously couldn't have been correct. Whether my EMS-reported operating AIT's are now correct seems a reasonable, but unsubstantiated, conclusion.

ECT Calibrations: For my ECT calibration table, I originally used a table that Giles put together based on empirical measurement until we realized that his measurements were done at a location too far from where the stock coolant sensor is mounted to be reliable. I then switched back to the AEM table for lack of anything better.

While at Laguna-Seca two weeks ago on a reasonably cool day (peak temps in the low 70's I'd guess) with my new C&R radiator, I was a bit surprised that my temperatures under track conditions reached 212 degrees F. Admittedly, my radiator now also cools my oil, but it's got a core that's three times thicker and a fan with three times the capacity of the stock fans combined. That's with water wetter and stock Honda coolant (pre-diluted to 50-50).

Based on the assumption that I've got more cooling capacity than I should need for a 25 minute track session on a cool day, I still think the ECT table is a bit high -- maybe by 10 degrees or so. (I'm running the Mugen thermostat and the fan is set in the EMS to turn on at 190 degrees and turn off at 180 degrees.) This new table from Gary seems to suggest that I was running something more along the lines of 191 degrees, which would be ideal. But given UL's comment about the need to do this experiment with the appropriate resistor, I'm still unsure what to conclude.

Oil Temperature Calibrations: I also tried hooking up an oil temperature sensor to the EMS, using one of my spare EGT inputs (I've got an EGT gauge rather than having individual EGT sensors wired into my EMS), but the results were bogus (even on the track, the temperatures never climbed higher than 158 degrees and after five hours of highway driving they never exceeded 115 degrees!). After returning from California, I called AEM and they claimed that my EMS wasn't set up with the correct resistors for the EGT inputs to work. I returned my EMS to them, and they've since modified my EMS to correct for this problem and have returned it to me, but I've yet to test the results.

If anyone's interested in the oil temperature sensor discussion (and my calibration information), it's contained in the following thread:

http://forums.s2ki.com/forums/showthread.p...threadid=174348

In any case, that's all I know at this point. If anyone's got any light to shed on this issue, I'd be grateful. It would be a relief to know that my new radiator setup is keeping my temperatures in the range I was aiming for, and I have the ability to adjust my fan threshholds to adjust the operating temperature somewhat.

Thanks,
CB

_________________
C. Bender
2001 Silver/Black
AEM EMS, Fuel Pressure Regulator, and Wideband O2 Sensor; RC Engineering 550 Injectors; Turbonetics TO4B 60:1 Ball Bearing Turbo; Tial 46mm Wastegate and 50mm Blowoff Valve; GReddy EGT and Boost Warning Gauges; Auto Meter Oil Temperature Sensor; Holly 250 Forced Induction Fuel Pump; CM 6" Remote Canister Oil Filter with Stainless Steel Lines; C&R Custom Radiator with Integrated Oil Cooler; Mugen Radiator Cap, Thermostat, and Fan Switch; Speedcraft Front Mounted Intercooler, Mandrel Bent Tubing, 3" Down Pipe, and 3" Stainless Exhaust; A'PEXi N1 Mufflers; Clutchmaster Stage 3 Clutch; Toda Lightweight Flywheel; Upgraded Oil Bolts; Elda Engineering Rollbar; Recaro SPG Competition Seat; Sparco 3" Six Point Harness; Spoon X-Brace; HeCash Brake Ducting; Competch Stainless Steel Brake Lines; WorkMeister S2R 18" Wheels; Lucid's Front and Rear Speakers; 2002 Stereo Head Unit; Rick's Front Badge; JDM Clear Side Markers and Shaved Badges; Muz Shift Knob; Uber Cool Nurburgring Decal

GaryRudolph

Once thing I haven't noted yet is what the ECT reads when the fan kicks on with the mechanical switch (and setting the ECU control high so that it doesn't kick it on). Then compare the read ECT. The stock switch turns on at 199. Right now when on the highway cruising in San Francisco at 80 at about 55-60F I'm running about 175F. Tonight as I do a little more tuning I'll see if I can note when the fan turns on.

Although, I doubt that will end the debate as it's in the radiator...

cbender

I came to same conclusion -- using the fan switch doesn't really tell you anything about the EMS ECT calibrations because not only is the fan switch in the radiator, it's in the RETURN line from the radiator (which makes sense, as it's primary function is to assure the supply of adequately cooled coolant -- if the coolant's too hot, it turns on the fans so that by the time the coolant goes through the radiator it's cooler and ready to be routed back into the block whenever the thermostat opens). So, the fan switch is measuring the coolant temperature at it's absolute lowest, whereas I'd imagine (but I've never verified this) that the ECT sensor is located toward the end of the coolant path through the engine so it's measuring near to where the coolant gets hottest.

CB

GaryRudolph

I was re-reading some of vapors2k's comments from the oil temp thread. Here's some thoughts.

1) With stock EMS he read 195F and secondary gauge read 176F.
2) The secondary gauge sensor is still located in the block, although I believe a little downstream from ECT. IMHO, it shouldn't differ by much. Maybe 1-2F at most as they are still both in the block.
3) When I ran before I would also see a 195F when things are warmed up and crusing at 80 on the stock EMS settings. Now, I see 175F with these settings which correlates to vapors2k gauge readings.

Now... as for using a resistor with the calibration. First, they are using a 2.2k resistor in series with the sensor. This isn't an issue with how I did the calculations. AEM has you calculate the voltage from the sensor resistance using EMS Volts = 5.00 * ( Resistance / ( Resistance + 2,200 ) ) which uses a simple voltage divider assuming a 5V supply. I assume the resistor is just to limit the current for when the sensor is at a low resistance or to drop the voltage to their A/D scaling levels. The point, is as I used this equation in the calculation it takes into account the resistor UL is talking about. Further, it correlates to what vapors2k read on his gauge from a block located sensor. As a result I'm currently feeling confident in this table.

But, to be really sure... vapors2k any chance you can compare this table in your car with your gauge stack readings?

Thanks, Gary

cbender

Gary, if you're right, this is Very Good News, as I was a bit discouraged by my EMS-reported operating temperatures at Laguna-Seca. While I discounted those reported temperatures somewhat by the impact of cooling my oil and by the possibility that the AEM-provided calibrations are too high, I'd feel a LOT better if we could say, for certain, that the AEM-provided calibrations are wrong and your calibrations are right.

Of course, then I might face the problem that my engine is running too cold, but I find that not terribly convincing given that it's the Mugen thermostat that controls how much coolant is permitted into the block and it works mechanically, rather than depending upon a sensor. So, unless the Mugen thermostat isn't able to respond quickly enough to close once my (now very cold) coolant enters the block, there's no way the car should ever run cooler than the temperature threshholds implicit in the springs of the thermostat, except of course on initial startup. Or so I'd guess.

Thoughts?
CB