Dougs951S

This may be the wrong place to post this...I feel like Rennlist should have a separate forum for troubleshooting megasquirt and other standalone EMS.

I got my megasquirted car running the other night. it idles better than stock, revs, and is driveable but there are a few issues.

1. It wont rev past 3500 rpm, it feels like I'm hitting a rev limiter. I suspect this is because I have not set the trigger angle with a timing light yet, and as RPM rises the timing error becomes larger until it acts like a spark retard rev limiter.

2. Both my IAT sensors are reading 0F even though they test perfectly when I bench tested them with a hairdryer, The wiring back to megasquirt checks out at ~2k ohms, I don't know if this is normal. I checked the wiring visually and it all looks good, today i'm going to wire a known good sensor directly to the board in cabin to eliminate wiring as a variable.

3. I'm also having issues with my MAP sensor, which is partly because I'm not certain which sensor I was sent. It is supposed to be a 3 bar, but its not a GM factory sensor so I'm having a hard time finding info on it. It reads high, 50-55 kpa at idle, which does not correlate to the 20" HG my boost/vac gauge shows. With the car off and key on its showing ~150 kpa which is obviously wrong since ambient pressure at my altitude is 99 kpa. It also reads incorrectly when I rev it, but it idles well. This is when I am using the GM 3 bar presets in megasquirt. If I change the presets to a GM 2 bar, it reads correctly with the car off and key on, right around 104 kpa on a nice cold night, but the car doesnt run! it stalls as soon as I try to start it unless I give it gas, and it runs really rough and I dont know why...If I change it to a 1 bar, the sensor never reads correctly and the car does not run. This is driving me crazy.

If I can get these issues sorted, I'll be finished and ready to take the car for some real tuning runs. As of now, I've only driven it down the street.

theedge

1) I would look at your trigger setup (the physical part of it). Look for runout on the wheel and make sure it is centered. Check the gap as well it could be too large. If thats all good, get the trigger angle sorted and see what happens. MegaSquirt has so many trigger options that it can be fiddly.

2) Might be obvious, but are the sensors grounded? One pin has to go to sensor ground the other to the IAT input on the MS.

3) Is it powered by the MS 5 volt output and grounded to the MS sensor grounds? I would suggest getting something you can reference it against, I use one of the handheld vacuum/pressure pumps with a gauge. Compare to that and see whats going on.

Dougs951S

I think physically the trigger wheel is ok... I spent LOTS of time getting it right, and the gap is exactly the same for every tooth with respect to the sensor. I used a timing light today and set the trigger angle at 345.5* BTDC, but it still doesnt want to rev past 3500ish. I'm thinking it may be because my map and iat sensors are not working correctly, so surely the mixture cant be right. I just hooked up my wideband so I'm going to see if its a fueling issue. The IAT sensor is grounded to the sensor ground, as is the MAP.

It starts up and idles GREAT, just wont rev...I'm sure its something simple and though I could be wrong, I think its unrelated to my physical trigger setup. Would it help if I posted my .msq or a datalog?

Dougs951S

All of the above has been done, something else is going on. I'm wondering if perhaps I was sent a damaged microsquirt. It simply will not pick up my air temp sensor or my air/fuel ratio 0-5v input. I wish I could send my unit to somebody to test for me in their car. I'm completely stumped at this point as far as the sensors. I went ahead and ordered a new trigger wheel.

86 951 Driver

Not much to add, but it seems to me like Robstah would like to see a 951 run on Microsquirt. Interesting.

86 951 Driver

Don't take my comment as me hating on you. I just thought it was interesting that you were trying to help someone with megasquirt, when you obviously have moved away from the 951 engine.

I agree with you I think there is some merit to getting the car on Megasquirt. Most notably an newer processor and hardware. A good upgrade would be to have C-O-P. Not sure if megasquirt can handle that or not.

Chris White

The MAP sensor is easy to test - key on but not running should read approx. 100kpa at sea level if you have selected the right sensor. Response is linear so if it says 33kps you have a 1 bar sensor on a 3 bar sensor calibration, 50kps you have a 2 bar sensor.

hp18racer

I am at the same point with my 928 megasquirt project. I used a 'mighty vac' hand pump to verify the MAP sensor was working. I had a problem with too much filtering of the MAP signal. I just hooked up a wide band. I am thinking if you are in the range 15:1 to 12:1 then fuel isn't what's keeping it from revving. Next I am going to make sure the throttle actually opens when the pedal is pressed and then get a timing light and look at spark timing.

Dougs951S

Guys, I went ahead and purchased a new trigger wheel because i am certain at this point that it is the source of my revving issue. Even though megasquirt isnt reading my wideband output signal, the gauge still works so I confirmed it isnt a fueling issue. My foot is in my mouth it seems because lots of guys here who are smarter than me tried to tell me this would happen...I went with the trigger wheel from goingsuperfast which is designed to be a bolt on to the stock 944 turbo crank pulley. I'll just need to figure out a bracket for the sensor now.

Chris, thank you so much for letting me know that those map sensors were linear! That makes finding the correct calibration much easier! If, on the 3 bar calibraton it is reading 150 kpa and 105 kpa on the 2 bar calibration when ambient is 100kpa, am I to understand I actually have a 2 bar sensor?

I'm still having issues with the IAT sensor, I wired a known working one directly to the board in car to eliminate the wiring as a potential issue and checked everything with a meter and it stills reads 0F. Its the same story with my wideband, I grounded the wideband output signal to the megasquirt sensor ground loop and gave it the 0-5 volt input but it is not reading anything. These two issues are the most befuddling to me, If I could figure out those two issues i think I'd be golden. Are there any settings in tunerstudioMS that could make my board not read either my wideband or my iat sensors? Does this sound to you guys like my microsquirt is damaged? I would think if that were the case, it would manifest its self in other ways and the car would not run. Thanks for everyone's input so far! This has been a great learning experience in EFI.

Edit: I am running MSII extra serial 3.2.1

Eric_Oz_S2

if it helps, the 2 bar delphi/gm calibration is:

V=0.0255xP-0.2040 eg 100kpa = 2.346V

minho78

Doug it's a possibility that you may enable or learn an input value the MS GUI. I don't know nothing about the megasquirt and this is only food for thought.

First check the values for the sensors if they are within range.
If that checks move the GUI and look for fields that may enable/disable those features.
If not then look at the HW since there could be some damage to these inputs. The MS could still be running fine but only the components for these inputs could be damaged. If there's schematics check all the different components in the ambiguity group.

I did a quick search and found this:

MAP Type values for this may be selected from the option menu, and are either 115 kPa or 250 kPa. All Version 2 MegaSquirt partial kits have the 250 kPa MAP sensor (this is all MegaSquirt sold in the last few years). The MAP sensor type should be auto-detected from MegaSquirt, but if it is not, select the right one and hit "Send to ECU".
You should check that TunerStudio reads approximately the correct barometric pressure when no vacuum is applied (i.e. the engine isn't running). Below is a chart of the 'normal' barometric pressures for various geographic elevations. MS2-Extra should generally be within 2 or 3 kPa of the value below for your elevation. Because of the increased accuracy of the 10-bit ADC on MS2-Extra, versus the 8-bit ADC of MegaSquirt, the MAP reading will likely be 1 or 2 kPa higher with MS2-Extra. If it is significantly different, check under 'Tools/Sensor Calibration' and verify that you have values of 9.3 (@ volts) and 260.9 (@ 5 volts) for the MAP sensor.

Good luck

Dougs951S

Manny, Thanks for the tips. The issue ended up being corrupted firmware. I was running MS2X 2.3.1. I flashed the unit to MS2X 3.3.1 and everything works perfectly now, all my sensors are dead accurate. Big thanks to Rob for suggesting the reflash to me, I would still be fiddling around with the hardware and cussing if not for the tip. The only thing I have not tested is to start it and see if the firmware update also fixed my revving issue. I suspect that it has not because I suspect that is an issue related to the wheel. I will know tomorrow.

minho78

Glad you found the problem.

But at this point I would try that wheel again since the FW might had been the problem. Good luck

Dougs951S

Still having issues. When the MAP sensor is calibrated to GM 2 bar specs, it reads dead nuts on but the car won't run, it stalls after a second and it will stall instantly if I try and give it throttle. If I set it to GM 3 bar calibration, the sensor reads ~50% high but the car runs.. This makes no sense to me and its basically the last issue I'm trying to solve. The car still wont rev past 3k, but I'm pretty positive now thats because I need to redo my trigger wheel. I'm going to install a 10k resistor inline on the VR+ and see if it helps.


Oh, one other caveat. The datalogs in MS show my Air/fuel being slightly leaner than what my gauge is showing. Its not a huge amount off, but roughly .5. The gauge is showing dead on 14.7:1 at idle but MS is reading 15.2:1. I used the calibration provided by my wideband manufacturer.. Should I just play with it till it matches my gauge?


Thanks everyone for taking an interest in this. I'd really like to see more megasquirted cars here pretty soon, I think I'm very close to a successful install.

hp18racer

If you set the MAP to be correct (GM 2 bar) I am guessing it doesn't run because it leans out? You can fix the resulting lean condition by changing what you tell the software your injectors flow. I think there would generally be less funny business/confusion by approaching the problem that way in the long run.