Supercircuit Header - works great but MIL on, how to fix?

[dickulus]

hello friends.

I recently added at supercircuit header to the 2015 mirage. works great, except i cant seem to debug the MIL / check engine light. Has anyone here been able to solve this issue?

What ive tried:

The defouler trick, one straight and one 90deg version. The straight seems to do just as well as not using a defouler (P0421 error for both) but the 90 degree defouler throws a new code: P0137

Ive also tried the resister + capacitor combo to flatten the curve. With 1M ohm and various capacitors (tried 1uF, 4.7uF, and 10uF) i have the P0140 error. suspect the 1Mohm is too big, seemed like the voltage was too low, but i am not super familiar with what the stock voltages should read.

Annoyingly, the cycle to test the 2nd bank is 6 min of driving 35 mph then 10 seconds at stop, then turn the car on and off again, then repeat. sot it typically takes me about 20 min per variation to experiment.

Would like to get the engine out of closed-loop, as it seems to run a tad rich when MIL is illuminated...

PS for those wondering, it did seem to add power. not a fast car by any means, but makes it much more comfortable to get up to highway speed!

Thanks!

[inuvik]

hello friends.

I recently added at supercircuit header to the 2015 mirage. works great, except i cant seem to debug the MIL / check engine light. Has anyone here been able to solve this issue?

What ive tried:

The defouler trick, one straight and one 90deg version. The straight seems to do just as well as not using a defouler (P0421 error for both) but the 90 degree defouler throws a new code: P0137

Ive also tried the resister + capacitor combo to flatten the curve. With 1M ohm and various capacitors (tried 1uF, 4.7uF, and 10uF) i have the P0140 error. suspect the 1Mohm is too big, seemed like the voltage was too low, but i am not super familiar with what the stock voltages should read.

Annoyingly, the cycle to test the 2nd bank is 6 min of driving 35 mph then 10 seconds at stop, then turn the car on and off again, then repeat. sot it typically takes me about 20 min per variation to experiment.

Would like to get the engine out of closed-loop, as it seems to run a tad rich when MIL is illuminated...

PS for those wondering, it did seem to add power. not a fast car by any means, but makes it much more comfortable to get up to highway speed!

Thanks!

Doesn't the Supercircuit Header have the sensor installed on the 1 exhaust pipe before it goes 3 into 1? OEM header sensor placement measures all 3. Could that be part of the problem? I have no idea, just a thought.

[dickulus]

Sort of.. bank 1 is in the manifold area, really close to cyl 1; the header is just cyl 1 but it's reading okay on my scanner.

It's the downstream sensor that's throwing codes. I'm not actually sure how it senses oxygen but somehow it needs a cat before it..

[7milesout]

I'm not actually sure how it senses oxygen but somehow it needs a cat before it..

I'm not sure what you mean by this, but I'll state what I understand. Granted, I may be wrong.

The downstream sensor expects a "rich" condition. To be more accurate, the oxygen sensor expects no oxygen. What comes out of good running catalyst on a properly running modern engine is carbon dioxide and water vapor. Which means, no oxygen. And the oxygen sensor is looking for oxygen. A rich running engine will wind up using all the oxygen available and having some amount of gas left over. Key here is, no oxygen is left in the exhaust of a rich condition. For a stock engine, there's no oxygen remaining in the exhaust after a proper burn and a catalyst reaction. So, it is as-if the exhaust is "rich" due to lack of oxygen.

If you remove 1 of the 2 catalysts (which I'm assuming is the case here with the header, but I could be wrong), I suppose it could lead to either the engine running more lean (due to throwing the system off not having the cat there) or probably more likely, it could wind up with oxygen in the exhaust due to not having the cat there. In any event, if that downstream sensor detects oxygen, the ECU assumes the cat is ineffective and thus signals the code.

Maybe you know all this already. Maybe I'm way off. But that's my understanding of what's likely going on.

[7milesout]

dickulus - I'm hoping you're still around. I'd like to know if you resolved this, and by what means.

I just somewhat recently had to remove the catalyst from my son's Mazda RX8. The cat went bad, and was replaced with a dual resonator mid-pipe. That mid pipe had a bung to install the 2nd O2 sensor. I ran a Big Daddies minicat along with the 2nd O2 sensor. I got the Check Engine light with 2nd catalyst code with that setup. Tried to get feedback from Big Daddies. They sucked.

I bought a different minicat through Walmart for 1/5th the price of the Big Daddies. So cheap, worth the experiment. Cleared the codes, and ran it. It's been on there likely 1,000 miles or so now. The codes and Check Engine light has not come back on.

The marketing of the mini-cat states that there's a small amount of catalyst material in the minicat. Said minicat is attached between the O2 sensor and the exhaust flow. So any exhaust that makes it to the O2 sensor goes through the minicat's catalyst material, and therefore the O2 sensor likes it ... a lot, and they become friends, and then the ECU doesn't get mad at the union and subsequently does NOT activate a code or Check Engine light. I have dain brammage, from watching too many cartoons.

[dickulus]

dickulus - I'm hoping you're still around. I'd like to know if you resolved this, and by what means.

I have not solved it. Ive tried everything - a minicat, mutliple spacer / washer combinations, a 555 timer, a RLC circuit, etc.

Honestly i just ignore the light now.

[Basic]

I have not solved it. Ive tried everything - a minicat, mutliple spacer / washer combinations, a 555 timer, a RLC circuit, etc.

Honestly i just ignore the light now.

I do too, and it sucks... it definitely makes the car run richer than it should.

[7milesout]

The reason I ask is because I'd be kind of curious to help with a resolution ... because I'm interested in, at least, having a trouble-free catless option. It would be nice if there was a way to run without restriction, and be able to pass emissions testing.

However, my car still has drivetrain warranty, which I would rather keep. So, I probably wouldn't do this on the Blueberry, just yet. But ya never know. I like solutions ... I don't love the effort to find them. But it would be nice for those that would take the chance to do this, or have a header, possibly to cat (like dikulus and Basic) to have a solution.

[foama]

The OEM sensor is of a special kind, because it responds practically instantaneously. On the OEM header it distiguishes the exhaust-puffs of each cylinder and individually corrects the air/fuel ratio for each cylinder. This is because the fumes of each cylinder pass over it, and it gives an instant result concerning air/fuel ratio.

If your aftermarket header is made such, that the sensor only sniff the fumes of one single cylinder, it obviously can not function properly and would be an absolutely stupid and flawed design. No wonder the air/fuel ratio is wrong. I would demand my money back!

[7milesout]

foama - I do not believe that is correct. Not at all. And, you're making BIG assumptions. And I don't believe your assumptions are correct. And besides, I don't think the 1st O2 sensor is the issue with the Check Engine light that dikulus is getting. I don't remember if it was this forum that mentions this. But (as I understand, granted I might be wrong), the 1st sensor is reporting AFR (oxygen) data to the ECU. The 2nd sensor is reporting probably oxygen data to the ECU ... but that signal is used in order to confirm catalyst performance. Therefore it should be the 2nd sensor that is the issue at hand. I'm probably making assumptions too. For one thing, I'm only referring to Mirages that run 2 O2 sensors. dikulus and Basics are those.

Don't misunderstand me. I don't think you're dumb. Quite the opposite. I just don't believe you're correct in this case. There are a lot of reasons why I don't think your assumption is correct. I actually run an AFR gauge. It is probably as high tech, possibly more so, as what is used by OEMs. It is attached to one collector on my V8 engine. Both sides have a bung and I can switch sides. It is MORE THAN capable on just the one side.

However, why I think your assumption is wrong is because, outside of actual design work, the 2nd leading amount of time spent as a design engineer is VA/VE or cost out. Every OEM will push their engineers to make everything on the car as inexpensive as possible. In turn, design teams will push tier 1's (suppliers, like NGK, Denso, etc) to do the same thing. Tier 1's will have maybe as much as quarterly, but at minimal once a year reviews with OEM engineers to review every possible idea and variation of the products they supply to said OEM, to reduce cost. These reviews are detailed down to dissecting a gnat's anus. I disliked these efforts. Too time consuming, for small reductions. But across thousands of parts, the reductions can be quite substantial. So it is always a big effort. The point being, if slowing down the sampling rate in some way reduces cost but continues to provide enough sampling to run well, the sampling rate will be slowed to minimal. I'm not saying that's the case, I don't actually know, it's an example.

I'm not saying an OEM O2 sensor cannot "sniff" every puff, it could likely take multiple samples per exhaust stroke. And heckfire, if you place it in a manifold where all cylinders' exhaust accumulate, how would it then distinguish between the 3 individual "puffs?" They blend. What I am saying is that it is not necessary to do so in order to gain the data needed in order to run properly. Perhaps it's sampling more than every individual exhaust stroke, perhaps it's sampling less. Its sampling at whatever rate the sensor is rated to sample, based on meeting lifecycle (warranty) requirements and cost standards. Automotive engineering is VERY complex. Decisions about how to design and solve problems are sometimes based on the most UNobvious reasons. Been through MANY decision meetings at Toyota and those meetings were a REAL eye opener. Much respect to the Toyota process of making design decisions. Hyundai simply makes decisions on how much things are like Toyota and, hey it's 1 cent cheaper, do it.

Basic - I sent dikulus a PM asking exactly what error codes he sees. I didn't send you one because, I guess I've missed where you mentioned your set up. As I recall you purchased ... drawing a blank, major contributor here / previous autocrosser, his blue Mirage. Now your blue Mirage (3 pedals, no cruise control).

However, if you don't mind telling me your setup, and what codes you see (dikulus too), we can go from there and see what we can learn. There is a solution. Will we find it? Dunno. It may be too complex and/or too expensive.