PO172

by **Akfahad** » Tue Oct 10, 2006 11:37 am

Just wondering if you guys had any ideas. PO172: System Too Rich...I was already going to go back to the dyno once I put on the Y-pipe and new MAF, but was wondering if you guys knew why it would through this code? Haven't done anything to make it rich, besides changing an 02 sensor and TPS.

by **DaveMush** » Tue Oct 10, 2006 3:24 pm

new MAF? meaning the toyota part it came w? or something different?

if you used a diff MAF all together.... and it is telling the ECU that it is getting more air than it really is, the ECU wil compensate by dumping more fuel to even the air/fuel mixture...

THEN the O2 sensor finds out that it is way too ritch after the mixture has been through the combustion cylinder...
Bet you are fouling plugs too. Might lead to misfires in the future.

by **Astro** » Tue Oct 10, 2006 4:02 pm

That's the supra MAF, correct?

I recently changed my back to stock. I want to put it back on, but I think it was part of my erratic idle issue. I don't know if it was, but my idle is smoother.

Dave, does this mean we shouldn't use it? I think Gabe was saying it works well with the supra injectors upgrade, bigger fuel pump, and better fuel lines to the rails. I don't know though, I was thinking about running on a dyno with and without it. But, I don't want to have any issues.

by **Sleeper** » Tue Oct 10, 2006 9:29 pm

I have the same code but i thought it was because i am using the SAFC2 which is supposed to give a richer ratio isnt it?

by **Akfahad** » Tue Oct 10, 2006 9:30 pm

Astro wrote:That's the supra MAF, correct?

I recently changed my back to stock. I want to put it back on, but I think it was part of my erratic idle issue. I don't know if it was, but my idle is smoother.

Dave, does this mean we shouldn't use it? I think Gabe was saying it works well with the supra injectors upgrade, bigger fuel pump, and better fuel lines to the rails. I don't know though, I was thinking about running on a dyno with and without it. But, I don't want to have any issues.

Yeah it's the Supra MAF. Next chance I get to go to the dyno, I'll have to put it on since the injectors/pump/etc. are all upgraded, but let me know if you do do the before and after tests Astro. I'd like to know.

by **CASTRO** » Tue Oct 10, 2006 10:17 pm

oooo, are you by chance tuned with the supra MAF? I wanted to get it to run a little bit rich w/o any tuning just for track days. I just dont want to run it if its so rich to the point that it sends off a CEL.

by **Akfahad** » Wed Oct 11, 2006 7:37 am

^^^That's a negative Castro, but will be soon...hopefully.

by **DaveMush** » Wed Oct 11, 2006 8:50 am

guys, keep this in mind when you start changing components...

The ECU is looking for a certain range of input voltages from the MAF. Each fraction of that voltage (each voltage incriment) represents a given amount of air passing the MAF.
If you take an ECU that is looking for 1 to 5 volts, and lets say that the MAF is only rated to see an air mass up to 40 units (I'm using this for sake of arguement) at the max voltage...
That would mean that for 40 units of air at 5 volts, each 1/10th of a volt equals 1 unit of air (since you are looking for a range from 1 to 5... 5-1 equals 4 volt range)

Now use a maf that can measure more air... boost the max # of units to say 60 (150% of the origonal) but it still has an output range of 1 to 5 volts (4 volt range)...
That means that each 1/10th of a volt now represents 1.5 units of air passing the MAF...

basically, with out some sort of compesation, or recalibrating the ECU map, the computer still thinks you are getting 1 unit of air in the engine so it matches that w/ correct fuel... BUT YOU ARE REALLY GETTING 1.5 UNITS OF AIR and only 1 unit of fuel.
hence the need for bigger injectors.

If you do one part, w/o the other... you are running the engine LEAN.

by **CASTRO** » Wed Oct 11, 2006 12:45 pm

^
but i though that the supra MAF would make you run rich if its not tuned. I remember a long time ago that Gabe and JoeB had a discussion where the Supra MAF is more sensitive/accurate but w/o tuning using a A/F such as a Super AFC, it would lead to richness.

by **DaveMush** » Thu Oct 12, 2006 9:07 am

thats where you need to know the range of voltages that the ECU can use (based on its a/f maps), and the range that each MAF is designed to put out...

You have to compare the 3 and make a judgement. I was useing the other values as an example.

Other thing is that the nice aluminum intake tues that everyone keeps using, dont allow the stock MAF to read all the air passing by it. Its been shown to effect long term fuel trims because the diameter of the pipe is too large for the MAF (making the centerline of the MAF not line up w/ the center of the pipe.)

by **StockSolara** » Thu Oct 12, 2006 3:32 pm

CASTRO wrote:^
but i though that the supra MAF would make you run rich if its not tuned. I remember a long time ago that Gabe and JoeB had a discussion where the Supra MAF is more sensitive/accurate but w/o tuning using a A/F such as a Super AFC, it would lead to richness.

Actually the MAF will make you run lean. . . hence the need for the bigger injectors

by **DaveMush** » Tue Oct 17, 2006 9:53 am

DaveMush wrote:If you do one part, w/o the other... you are running the engine LEAN.

I think I said that already...

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