SR20DET MAF adventure

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okayfine
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Re: SR20DET MAF adventure

Postby okayfine » 29 Mar 2015 08:03

akara wrote:I think it might be worth it for you to try another maf

It looks like no matter what nissan maf you have 1.7v is going to make the ECU calculate about 10 percent load so I think its worth checking out!
Grounding is important and many people recommend regrounding the MAF instead of relying on the poor quality factory nissan ground splices placed throughout the harness.
Do you have a vacuum/boost gauge? You should be seeing 20in of vacuum at idle, any less means you have a vac leak!


Concur. And doubly so on the grounds. You don't get an appreciation about how poor they are in a Nissan harness until you take one apart and see for yourself. Each splice is also full of tape goo, which isn't helping conductivity.

Known-good MAF will sort this in short order one way or another. 1.7v is out of spec.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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jovial_cynic
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Re: SR20DET MAF adventure

Postby jovial_cynic » 29 Mar 2015 12:25

I should have one on the way here soon.

I did verify the ground, though. Or more specifically, I ground the MAF directly to the block. Still no dice. The signal wire sends the 1.7v until I hook up the LED, and then it goes down to 0.2v or something... so there's some drastic voltage drop going on that's leaning out the engine, I guess. Sigh.

I'll let you all know as soon as the replacement MAF arrives.
71 510 2-door SR20DET (S13)
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http://www.myagentjosh.com
http://www.newprotest.org/510

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jovial_cynic
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Re: SR20DET MAF adventure

Postby jovial_cynic » 29 Mar 2015 19:31

Because I can't help experimenting, I'm going to put a small computer fan in the intake and use the voltage output as a signal to the ECU. Little fans can generate voltage as they spin if you tweak them a bit, and while the output won't follow the same curve as a proper MAF, it should be interesting to see what happens. I'll keep an eye on the O2 gauge to make sure I don't break anything...

Wish me luck!
71 510 2-door SR20DET (S13)
------------------
http://www.myagentjosh.com
http://www.newprotest.org/510

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jovial_cynic
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Re: SR20DET MAF adventure

Postby jovial_cynic » 02 Apr 2015 18:23

Sooooo.... turns out that the problem was the 12v supply going to the sensor. I was chasing the ground, but it was never the problem.

I received a replacement MAF and the problem persisted, so I compared voltage at the plug to the voltage at the battery, and the difference was enough to clue me in.

Vroom vroom, amd then I ran out of gas. Ha.
71 510 2-door SR20DET (S13)
------------------
http://www.myagentjosh.com
http://www.newprotest.org/510

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jovial_cynic
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Re: SR20DET MAF adventure

Postby jovial_cynic » 27 Mar 2016 19:24

I'm having some interesting new issues with my MAF.

I decided to build my own intake plumbing between the turbo inlet and the MAF, and in an attempt to quiet down my intake, I've begun building an intake box to quiet things down and to also direct some cooler air into the engine. However, I'm learning that the SR20DET MAF is very sensitive to changes in the air flow.

At the moment, I've got a cheap adaptor to fit a K&N style filter onto the MAF. Based on my wideband O2 sensor, the engine runs very lean, to the point of sputtering out and dying at idle. It's a bit like when you have a leak in the intake. However, when I take the filter off and provide a little bit of restriction to the air flow going into the MAF, the idle smooths out and richens up a little. This makes me think that without this restriction, the flow of air past the MAF's hot wire doesn't go fast enough for the computer to figure out that there's a bunch of air going in. With the restriction, air flow speeds up across that wire and voila, things work out.

I've fiddled around with some sheet metal restrictors - a sheet with a bunch of holes in it (no good), a sheet with one small hole in the middle, smaller than the MAF intake port, but ported like a venturi (no good), and also a sheet with just a flat hole (better than the other two, but not perfect). Oddly, the BEST is just putting my fingers over the MAF and varying the spacing between my fingers until I can hear the idle smooth out.

All this makes me wonder if the stock air box has some engineered plumbing to address this very thing. I'm a little baffled by the two different size holes on the MAF: one is outer hole that you'd connect either to a filter or air box; the other is inner hole that much smaller in diameter, and located adjacent to the tiny hot-wire hole.

Any advice on this?
71 510 2-door SR20DET (S13)
------------------
http://www.myagentjosh.com
http://www.newprotest.org/510

datzenmike
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Re: SR20DET MAF adventure

Postby datzenmike » 27 Mar 2016 20:24

Run a straight section of pipe between the air filter and the MAF. Longer and straighter the better. Move the filter away from the MAFf
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs


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