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Old 09-29-2014, 02:56 AM   #1
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Alright folks, it's been awhile since I've posted and I've got a good one.

A little background, I bought my 1996 miata last winter and have been cleaning it up, making it reliable, giving it a comfortable garage and love ever since. The only thing that was gleamingly strange with the car when I bought it, was... It had an AutoMeter boost gauge installed in the A pillar in a single pod. It was clearly not turbocharged when I bought it, and at some point somebody sunk a decent amount of money into the RB headers and exhaust. Now because of this, I was obviously skeptical that it was boosted at one point in it's life. Cautiously optimistic that it was just being prepped for a turbo build, but still skeptical. It wasn't until a few months back when I installed the FM frame rails when I peeled back the carpet, and saw what was going on with the ECU...



I thought that was the final straw. I'm still new to miatas, and even newer to the idea of boost, and so I figured asking the experts would be the best way to go about this.

So, in a roundup what I know..

-The car has a boost gauge that has a power wire that runs over to the ECU area, and a vacuum line that runs through the firewall but not all the way into the engine bay.
-The ECU AFR wire has been tampered with.

What I ask of you guys here, is if you can help me investigate to find out what this car may have been up to in the past?
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Old 09-29-2014, 04:37 AM   #2
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I am going to say that the previous owner was putting gauges in the car to make it look cool but not actually do anything. If he spliced into the oxygen sensor wiring he was splicing into a narrow band sensor signal and so you wouldn't really get any useful information.

Maybe the previous owner had visions of greatness but it's likely he/she didn't know what the heck they were doing. It appears at least that they called it off and sold it before they did any serious damage to the car so that's a good thing. Where do those wires go to as of right now?
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Old 09-29-2014, 12:24 PM   #3
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I'm also wanting to lean on that side of the fence too. I just don't exactly know how boost bandaids work, and I thought maybe the signal was intercepted somehow to make the car dump more fuel or something to that effect. The wire that was in question runs straight into the ECU, as it should. But I will say that the boost guage had a red wire leading into the ECU area and it looked really similar to the red wiring you see frankensteined into the O2 sensor wire above.

This is the vacuum line that's running through a drilled hole into the inbetweeny area of the firewall and engine bay.

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Old 09-29-2014, 02:28 PM   #4
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The easiest way to check if the car was ever boosted is to look on the oil pain for a drain flange. I bought my car with a small hole in the A Pillar where a single pod once hung. I didn't think much of it until I took off the under tray and found it had already been tapped and a plug installed.
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Old 09-29-2014, 04:14 PM   #5
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Props. I just crawled underneath the car under the comfort of my jackstands and found that there is no sort of flange in the oil pan that could have been from a previous build.

However... I did find that the oil pan itself had a bit of blue gasket maker which I had seen before, but I never bothered to check on the side of the pan itself to see if the VIN numbers matched up with that of my car. Sure as ****, the vin is different. So, at some point the car has had a different oil pan put on. Correct me if I'm wrong, don't you need to pull the engine to put a new oil pan on?
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Old 09-29-2014, 04:33 PM   #6
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As far as I understand it the engine has to come out to swap the pan, but maybe that's just the "easier" option compared to dropping the front sub frame?
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Old 09-29-2014, 04:44 PM   #7
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Perhaps the car was lowered and cracked the oil pan on road debris?
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Old 09-29-2014, 05:01 PM   #8
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I've cracked an oilpan before and swapped it from another car. Even if it is a different motor, it's not the end of the world on an almost 20 year old car. Check the vin on the oilpan and see what year it came from: http://neomiata.com/garage/Miata%20VIN%20Decoder.pdf
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Old 09-29-2014, 05:01 PM   #9
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Another possibility is that the car used to have a JR M45 supercharger. They run on bandaid fuel management and do not require a drain line into the oil pan. This also makes sense with using a good header and exhaust. Since with the old non-adjustable bandaids you can't make adjustments anyway I can see someone tapping into the stock O2 line for a narrow band O2 gauge, and the boost gauge.

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Old 09-29-2014, 11:51 PM   #10
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I think that may have hit the nail on the head. I still need to go out and look for evidence that might help show any signs that a supercharger may have been bolted up, but that's the most sensible thing that would have been done. The car has a DDMWorks intake on it, maybe that was added on after the fact. The bottom of the car is immaculate and nowhere on the subframe are any scratches, bangs, or anything that would show it was cracked due to the car being slammed. It's got a lowering suspension on it but no kind of low that would turn the heads of the hondaboiz or even require fender rolling.

Thanks for your guys help, I really appreciate it!
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Old 09-30-2014, 12:31 AM   #11
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I don't think that header fits with that supercharger.
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