Engine cutting out under load/boost
08-25-2011, 05:19 PM
#1
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Engine cutting out under load/boost
So finally got my car running on megasquirt after problem after problem etc.
So anyway after doing the basic settings ie spark and constants i went out for a spin. Figured with the base tune itd drive and at worst knock. So i went out and was able to accelerate just fine but when i went wot or boosted over 4 psi my engine cut out, tach died and ignition basically cut off for a second
So I checked overboost setting and set it for 255. Same thing happens
Changed the constants a lil more and once again same thing.
Went through all the other settings and none of the other hard cuts seemed like they should be happening
Im basically running a base tune for a 90 miata but it has 1.8 engine.
Doubt it makes a huge difference though.
Someone mentioned dwell when i was searching but it didnt seem to me that with a base tune my engine would cut out under boost. Maybe knock at most
And to me it still seems like im hitting the overboost protection even though its basically off at 255.
Idk
So anyway after doing the basic settings ie spark and constants i went out for a spin. Figured with the base tune itd drive and at worst knock. So i went out and was able to accelerate just fine but when i went wot or boosted over 4 psi my engine cut out, tach died and ignition basically cut off for a second
So I checked overboost setting and set it for 255. Same thing happens
Changed the constants a lil more and once again same thing.
Went through all the other settings and none of the other hard cuts seemed like they should be happening
Im basically running a base tune for a 90 miata but it has 1.8 engine.
Doubt it makes a huge difference though.
Someone mentioned dwell when i was searching but it didnt seem to me that with a base tune my engine would cut out under boost. Maybe knock at most
And to me it still seems like im hitting the overboost protection even though its basically off at 255.
Idk
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08-25-2011, 10:43 PM
#7
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So I went in for kicks and giggles and dropped the rev limit real low to mimic whats been going on then went in and lowered the over boost protection and determined it was boost related. Ended up disconnecting the map and car ran great. So I decided to raise the overboost to 20 psi this time in tunerstudio and car ran much better but still not perfect.
So my question is, why would a map sensor read 15psi high.
So my question is, why would a map sensor read 15psi high.
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08-26-2011, 01:11 AM
#9
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which grounds like the grounds for the motor. They always worked before
but yea megasquirt is definetly turning on and off when the car starts bucking
which grounds are in question
and if it was a ground how come when I disconnect the map sensor the car works flawlessly
and after reviewing my logs the map appears to be working flawlessly
wtf....idk
but yea megasquirt is definetly turning on and off when the car starts bucking
which grounds are in question
and if it was a ground how come when I disconnect the map sensor the car works flawlessly
and after reviewing my logs the map appears to be working flawlessly
wtf....idk
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08-26-2011, 01:27 AM
#10
which grounds like the grounds for the motor. They always worked before
but yea megasquirt is definetly turning on and off when the car starts bucking
which grounds are in question
and if it was a ground how come when I disconnect the map sensor the car works flawlessly
and after reviewing my logs the map appears to be working flawlessly
wtf....idk
but yea megasquirt is definetly turning on and off when the car starts bucking
which grounds are in question
and if it was a ground how come when I disconnect the map sensor the car works flawlessly
and after reviewing my logs the map appears to be working flawlessly
wtf....idk
But not saying that's for sure your problem, however its deff something to check anyway.
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08-26-2011, 01:07 PM
#12
Here's the bottom line. You've got electronic noise. It is sometimes causing resets. Sometimes, it doesn't go so far as a reset (you can see lots of spikes in MAP and CLT in your logs without the red lines).
When noise is present parameters go haywire.
You need to get rid of the noise.
Focus on three areas:
1. Grounds. Pull the grounds. Wire brush them. Re-install and torque. Pull the coil bracket. Wire brush that too. Re-install and torque. Make sure your ground for ECU power is relatively isolated from grounds of things that generate a lot of noise (like a radio). The closer to stock wiring, the better.
2. Power. As with grounds, make sure your ECU power is relatively isolated from noisemakers. Anything with a coil is a killer (relays, solenoids, ignition, electric motors). Headlights? Radio? Again, if you've preserved your stock harness, you're better off.
3. Electro-Magnetic Interference (EMI). Make sure your ECU is protected from EMI. Hopefully, you didn't hack the ECU harness much. An MSPNP is ideal from this standpoint. Make sure you have the metal cover on the ECU and that the metal cover is grounded to your frame (and NOT grounded to the ECU power ground).
The more you kept your OEM harness intact, the better. Beyond a general cleanup and inspection, the next step is to carefully examine your logs and try to correlate the reset events to something external.
In my case, I was able to correlate resets to reductions in the MAP signal through my WI setpoint. This then tied into when the WI relay would depower and generate a flyback voltage. By moving my flyback diode outside of my ECU, I eliminated the resets. This is the kind of detective work that might be needed.
When noise is present parameters go haywire.
You need to get rid of the noise.
Focus on three areas:
1. Grounds. Pull the grounds. Wire brush them. Re-install and torque. Pull the coil bracket. Wire brush that too. Re-install and torque. Make sure your ground for ECU power is relatively isolated from grounds of things that generate a lot of noise (like a radio). The closer to stock wiring, the better.
2. Power. As with grounds, make sure your ECU power is relatively isolated from noisemakers. Anything with a coil is a killer (relays, solenoids, ignition, electric motors). Headlights? Radio? Again, if you've preserved your stock harness, you're better off.
3. Electro-Magnetic Interference (EMI). Make sure your ECU is protected from EMI. Hopefully, you didn't hack the ECU harness much. An MSPNP is ideal from this standpoint. Make sure you have the metal cover on the ECU and that the metal cover is grounded to your frame (and NOT grounded to the ECU power ground).
The more you kept your OEM harness intact, the better. Beyond a general cleanup and inspection, the next step is to carefully examine your logs and try to correlate the reset events to something external.
In my case, I was able to correlate resets to reductions in the MAP signal through my WI setpoint. This then tied into when the WI relay would depower and generate a flyback voltage. By moving my flyback diode outside of my ECU, I eliminated the resets. This is the kind of detective work that might be needed.
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08-27-2011, 12:20 PM
#15
I was really curious about your setup . . . stock injectors + fuel pump + FPR + MS. Looks like your asking a lot of the stock injectors . . . although that's not the problem here.
What type of MS is this? MSPNP, DIYPNP, other?
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08-27-2011, 06:31 PM
#16
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seeing as the car is running so well under boost with the map disconnected and the seller of the mspnp telling me the ms works, i decide to out of curiousity input the values of boost in place of the atmospheric kPa basically replacing 90 with 120kPa and and 101 with 139 and so on. And car runs as flawlessly as it did with the map disconnected except now it can idle.
Basically it was my tune. I have a fpr on my return fuel lines so the ecu pressure meant diddly and this ^ was the only way to get it to run. But damn I feel stupid getting caught up in this being a grounding or noise issue i never even considered it being my tune. I just never realized ms would kill the ignition on a shitty tune. At least my cars well grounded now though.
Basically it was my tune. I have a fpr on my return fuel lines so the ecu pressure meant diddly and this ^ was the only way to get it to run. But damn I feel stupid getting caught up in this being a grounding or noise issue i never even considered it being my tune. I just never realized ms would kill the ignition on a shitty tune. At least my cars well grounded now though.
Last edited by braaat; 08-27-2011 at 09:45 PM.
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08-27-2011, 11:19 PM
#17
I'm surprised. I knew that the basemaps you were running would not work well with a FPR -- they were designed for a stock engine. But, I would not have expected that to result in dropped syncs and data spikes.
Hmmm . . . . Well, glad you're running better. Keep us advised on progress. Also, how about doing a build thread?
Hmmm . . . . Well, glad you're running better. Keep us advised on progress. Also, how about doing a build thread?
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08-30-2011, 11:55 PM
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Yea definitely should start a build thread especially with me having to pull the motor to replace some oil pan seals. Tried doing it with the motor in car and its still leaking only the back one now tho.
Anyway I disconnected the fpr and those base maps ran pretty smooth untill I started running straight downpipe and now I have some raw boost creep. Like 12lbs with the wastegate actuator bar completely disconnected. But the car pulls like a monster till it cuts out. I swear it'd stay with my 600 if it kept pulling lol. No need for fare warnings on blowing my **** up I know.. I just wish my **** wasnt leaking oil all over the place so I could focus on tuning.
Anyway I disconnected the fpr and those base maps ran pretty smooth untill I started running straight downpipe and now I have some raw boost creep. Like 12lbs with the wastegate actuator bar completely disconnected. But the car pulls like a monster till it cuts out. I swear it'd stay with my 600 if it kept pulling lol. No need for fare warnings on blowing my **** up I know.. I just wish my **** wasnt leaking oil all over the place so I could focus on tuning.
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