Megasquirt PNP2 initial setup issues

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Hey guys,

looking for some help to iron out a few issues with Megasquirt.

Im setting it up on the stock motor which I will be rebuilding and doing a turbo setup over the winter. The plan is to get it running well with Megasquirt now so I can learn the ropes before I do anything serious.

Current setup:
Megasquirt DIY PNP2
M20B25 with M50 injectors

So far I have:
-Swapped out the AFM for a GM IAT
-Swapped out the stock TPS for a M50 TPS
-Added an AEM X-series wideband
-I'll be adding wasted spark once the issues are ironed out

The car starts up and idles. AFR's look ok while idling (I used the autotune feature while idling after it was warmed up and it helped a lot)

The main issues:
-When I turn the car on, it idles normal for a second then shoots up to around 2500rpm. It slowly goes down as it warms up and settles into a normal idle.
-The TPS doesn't seem to read on the lower end, but it shoots up if I rev it hard. It seems to sort of break up while revving. I did calibrate the TPS. It starts at 0 and WOT shows 433 (is this normal?)
-The car sputters after I turn it off. It sort of bucks and almost sounds like its going to turn back on.
-Sometimes it takes a couple cranks to get it started back up, almost like its flooded.

Thanks in advance for any help!

I've attached my current tune if that helps:

https://drive.google.com/file/d/1sic4WVSG_bPp2HL93VAL2g03vsaShCTa/view?usp=sharing

[e30davie]

Did you change the required fuel to match your injector CC? (sounds like your flooding issue) the "required fuel" must be set perfect or youll have no hope of getting it right. your injector dead times must be pretty close to.

Your TPS issues are not "normal" i recall the wiring needs to be changed for the m50 tps. need to figure out what the 3 pins are and make sure they match the inputs to the ecu. there is 5V, ground, sensor (basically your 0-5 signal).

All those issues sound like you just need to tune it. Have you read the mega squirt manual 500 times? its the onyl way I managed to get mine done to a good standard. Pick and issue and try and understand it fully and use the logging function to try and understand what the ecu is doing.

there is also a really good "getting started

does your IAT and water temp show the correct numbers?

Have you confirmed your timing offset with a timing light? the quoted number is 87, but seems to vary between cars a bit. mine was closer to 84.

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Thanks for your response man. I was able to sort a lot of it out.

The specs on the M50 injectors say that they are 176cc. What I didn't realize is that is for 3.5bar and the M20 is 3 bar. I found out that they are actually 166cc. I can't find any info on dead times. Thats grey area to me that I need to dig into.

I checked the timing with an adjustable light and turns out my timing offset was 94 so I changed that. Ive seen people with results from 84-97.

The TPS was wired correctly. Basically the adaptor Im using to mount it to the throttle body doesn't place it properly for full engagement. I had to modify the mount to turn it a little bit so it reads as soon as the throttle is cracked. I'm going to either buy a different brand mount or make one myself. Its working perfect now that I made the adjustment. Seems like it may be an issue with the SSSquid mount, this person has the same issue: https://www.msextra.com/forums/viewt...?f=101&t=73339

Its not sputtering anymore after I turn it off (I guess its referred to as dieseling?). It was probably related to the timing and injector adjustments.

Lastly the issue with the idle where it shoots up shortly after I turn the car on is fixed as well. By Default Megasquirt had the Air Conditioning Idleup feature turned on (at least it was on mine). Turned it off and its all good now.

The car now starts up and idles perfectly. I was able to take it out for a short drive today to do some logging. Used the auto tune feature and it smoothed out my AFR's a lot.

I know Im far from perfect but Im in a good place. I'm going to dig into the manual so I can really learn this on a more granular level.

[e30davie]

Sounds like you very much have it under control.

One good trick with the auto tune is that you can lock out cells that you dont want it to change. good practise to lock out the idle cells once they are sorted as i found that it always tried to change them slightly.

TPS based Acceleration enrichment made the most difference on my car. took a while to dial it in, but once you do it makes a good difference to how it drives.

[Northern]

Thanks for your response man. I was able to sort a lot of it out.

What I didn't realize is that is for 3.5bar and the M20 is 3 bar.

Any quoted injector flow rate should be at 3 bar. Should be a few pages out there that you can take the PN off the injector and get flow rate at 3 or 3.5 bar

Is that TPS issue fixed?