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Old 11-11-2008, 01:10 AM   #1
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Default TPS and Coolant Set Up

Building on my recent success, I put some more time into getting my car to run on Megasquirt in a parallel configuration. I can’t get the car to hold an idle and it is far from drivable on MS, but I am chipping away at it.

Tonight I set the static timing on the stock ECU to 10°. I know I need to set the trigger angle for the Megasquirt, but I can’t get the car to run steady enough yet. It looks like I have to tackle other issues first.

TPS question.
I calibrated my TPS per the instructions on DIY’s site for the MSPNP. The Calibrate TPS menu in Megatune doesn’t have the ‘Burn to ECU’ button. Once the values are captured, are they automatically written?

Coolant Temperature Guage
Megatune does not show the correct coolant temperature. The gauge holds at 170°. I am running a parallel installation, so I followed Braineack’s build instructions and did not install R7.

I double-checked the harness. Pin 3G on the multilock connecter passes through to the stock ECU and is shared on pin 21 of the DB37 connector. I loaded Easytherm values per
Saml01’s post. Before I removed R7 I was able to play with coolant temperature on the stim. Since I removed it, it hasn't budged from 170° in Megatune. I thought that would be resolved when I had to share the sensor with the stock ECU. Did I miss anything obvious?

I also ran across a post warning new users (me) to check that constant baro correction is turned off. The MSPNP base .msq had it set to 'Extra MAP fitted to X7'. I have just the single sensor, so that is one more adjustment I had to make. I'm inching along, but it looks like I'll be driving on the stock ECU again tomorrow.
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Old 11-11-2008, 01:45 AM   #2
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TPS values are saved in the megatune folder as a setting when you hit save. You should reopen the MSQ and reburn after doing that just to make sure its done correctly.

Not sure why your coolant temp isnt reading right.

Add more fuel, its probably running lean and jumping all over so add more fuel in the idle cells to richen it up and hopefully smooth it out so you can set the trigger angle and then proceed with fuel map tuning via MLV.
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Old 11-11-2008, 06:34 AM   #3
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Did you use easytherm to set the correct setting (Celsius or Fahrenheit)? If you save a log file it will show your TPS in a graph which will tell you if it works or not.
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Old 11-11-2008, 09:42 AM   #4
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Quote:
Originally Posted by Cosmic_Eraser View Post
I double-checked the harness. Pin 3G on the multilock connecter passes through to the stock ECU and is shared on pin 21 of the DB37 connector. I loaded Easytherm values per
Saml01’s post. Before I removed R7 I was able to play with coolant temperature on the stim. Since I removed it, it hasn't budged from 170° in Megatune. I thought that would be resolved when I had to share the sensor with the stock ECU. Did I miss anything obvious?

gotta be something bad in the wiring. When it fails to 170*, it's because there's no sensor attached (see your thermfactor.inc).
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Old 11-11-2008, 11:28 AM   #5
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Braineack speaks the truth.

The way this works is that the CPU does an 8 bit A/D conversion on the incoming signal, scaled as 0-5v, and returns a number from 0 to 255. It then refers to a table of conversion values that was generated during the EasyTherming process to correlate this to a temp value. This same table is also written out to thermfactor.inc (for MegaTune to use) and so you can see what's going on. Here's an excerpt:
Code:
ADC  Temp, degF
0    Sensor Failure - use 170 degF as default
1    674.64
2    533.77
3    466.67
(...)	
252   -44.51
253   -50.43
254   -58.22
255   Sensor Failure - use 170 degF as default
As you can see, when the returned value is either fully high or fully low, the MS assumes that the sensor has failed either open or short, and thus plugs in 170° as an error indicator, and to provide a value to the code that'll at least keep things running in a semi-normal state (eg: not in warmup, not in overheat). Thus, you are correct as to why it no longer worked when you removed R7 and tested on the stim, as there was no longer a pullup. Now, however, it should be working. But the MS is seeing either +5v or 0v on its CLT sensor input, and thus throwing this fault.

For starters, turn everything on and use a voltmeter to measure the junction of R8-C6, relative to ground. (R8 is right below R7). Depending upon the temperature of the engine, you should see something in the 2-3 volt range.

If you see this, then you'll need to dig further into the MS itself.

If you see 0, then try unplugging the MS and making the same measurement directly at pin 21 of the DB37. Fixed? You've got a short in the MS. Still nothing? You've got a bad sensor, bad wiring, etc.

If you saw +5v (or very close to it) at any of these places, then your CLT sensor is either disconnected or failed open. On your '97, the CLT sensor line passes through Common Connector X14 (under the hood) which if I recall correctly is the disconnect point for the injector harness.
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Old 11-12-2008, 02:12 PM   #6
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You guys were dead on. It took a while, but I finally found that a pin in my multilock connector still had the insulation on the wire. I have no idea how I got so sloppy. I would have never found that with out Braineack's note and Joe's troubleshooting steps. Thanks again guys!

Cjernigan and jobambo, I ran a new log and I see what you guys are talking about with the TPS. Until I get this thing tuned, I don't plan on stomping on the accelerator. However, my log does have a min=0.0 and a max=49.0. That sounds about right for what I was running.
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