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Old 09-14-2014, 09:48 PM   #1
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Default Need MS3 Tuning Help; Backfiring

I've had my MS3-powered Seven going for a while now; it's my DD unless it's raining or snowing. However, I can never really put it to the limit, because sometimes, when I go to WOT, it'll pop, like a backfire, and lose power for a beat, then go on as if nothing happened. I'm thinking it's running lean when it does that, but no matter what it is, I know it isn't good for it. So I typically keep everything at about 50%, and it's fine, but it'd be nice to really be able to beat on it.

I know I need two things; I need a wideband controller, and a good dyno tune. Sadly, both things require money, and I have none of that either. I have the wideband sensor, but no controller yet. It's high on my list. I've heard of a dyno shop in the area, but I don't know if they have ever dealt with Megasquirts before. What I really need is someone that knows the MS3 really well.

I'm using a 1994 harness, fuel rail, and ECU. The engine is a 96. I have no accessories, only the alternator. I have 550cc injectors, a Walbro 255lph fuel pump, a Super16G turbo, Nissan (I'm guessing) SR20DET intercooler and BOV, and I've converted from MAF to MAP. I'm maxing out at 10psi, for safety's sake.

Here's my data. I couldn't upload anything other than the MSQ. All the datalogs are in this drive due to size.

I've had it misfire/backfire, whatever that is, in several of the logs. My fuel map seems a little lacking towards the end. Am I missing something? I've used VE live numerous times, and this is what it always gives me. Perhaps a similar Miata tune would help, maybe one using a Disco Potato?
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File Type: msq CurrentTune.msq (138.7 KB, 23 views)
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Old 09-14-2014, 10:53 PM   #2
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Park the car until you get a wideband setup

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Old 09-14-2014, 11:31 PM   #3
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You're about, oh, five years too late. It's been running for quite a while now. I mean, it has a narrowband, and it is reading stoic, and while I realize this isn't the best way of doing it, I do know it's not an issue typically.

Any experience with the ASPX D1 controller? That's a little closer to my budget, especially since I'm not using conventional gauges.

Last edited by SteyrTMP; 09-14-2014 at 11:45 PM.
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Old 09-15-2014, 12:23 AM   #4
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running stoic at full boost is not wise. tuning with a narrowband is even more unwise

you need a wideband to tune to your boost areas of the map

for the most part, when I've experienced pops, it's been because of being super rich, but in this case scenario, your next pop or bang could be a piston/rod through your block?
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Old 09-15-2014, 01:10 PM   #5
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Can you point us to a data log that specifically captures the issue?
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