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Ironhead
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Discussion Starter · #1 ·
these just might do it. direct bolt on with pre-cat. wonder what the CEL will think about this? smog legal? they have to be the best bet so far.










dont make me click this for you
 

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Yeah like I said in the previous post I wonder if these will throw the CEL light

they look really nice though and so far those are the only ones that I have seen that look half way decent

I submitted them a message saying: "Hey on your Scion TC header, I wanted to know if you have experienced any problems or complaints on how people are getting their Check Engine Light to come on after installation. Thanks."
 

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Former '05er
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I'd also like to know how they got the engine to rev to 6600 rpm. Mine won't do that, I've tried.
 

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I've been following information on these headers for a couple weeks. It seems that there have been isolated incidents of them throwing a CEL.

Apparently they have a fix and they're not supposed to throw a CEL. There is quite a bit of info at SL. Er.. There are some long threads with limited information posted at SL.

6600 RPM? The dyno pics are from tctunerz. Interpret that however you wish.

The main info thread is here:
http://www.scionlife.com/forums/viewtopic....0&postorder=asc
 

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Well after reading that SL thread it appears that the Megan header absolutely throws a CEL. Strange that they would claim it didnd't throw a CEL on any car they tested, but EVERY person on SL who has bought one has a CEL....

Another question - assuming this didn't throw a CEL, and it has the precat built in, but it doesn't have a CARB #, would this actually be legal in CA?
 

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OK here is the final answer from Megan Racing....

Hi,
Thank you for your email. The headers are the first generation we made
for the TC, we are trying to make something for the TC community. As you
know, the new TC factory header got a built-in catalytic converter, which
made all aftermarket header manufactures real real hard to produce an
aftermarket header for the TC. It is because most headers that you can find
on the market, they do not have cat converter inside the headers. We did
make a similar cat inside the header to reduce the chance to have the CEL to
come on, thats so far the best we could do. None of the other header makers
now is able to make a header like ours, the other companies that making the
TC headers now do not include any cat or anything to reduce the chance to
avoid the CEL comes on. So I hope you to understand that we are trying to
do something for the TCs and we will improve whichever products that are not
doing right. This is for the first generation, so for sure 2nd generation
will release anytime in the future. We are trying to control the CEL to
stay off all the time. We already have couple plans now, and we are working
on it, and we might even give away free 2nd generation headers for those of
you need to replace it. So please don't get upset and hand on there.

Solutions:

1. Look for different materials to replace the current ceramic cats we made
inside the header, a long lasting one and is able to keep the CEL off.
2. 2. Work on the S pipe after the header, that’s what other people suggest.

3. Discontinue this product just because there is no way to make a good
header and keep the CEL off.
 

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Former '05er
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It would be a lot more valuable if they told us what code was getting set with the CEL.
 

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looking at the dyno, is it normal for a car to run that LOP between 2500 and 3000 rpms? or does that have to do with coming off idle or something? also, seems that our cars or this one runs kinda ROP from that point on... would maintaining a 14:1 ratio do much for us? im guessing this is where you get the SFAC II or something right?
 

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Former '05er
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A/F will depend on detonation resistance and throttle position. Dynos are done at WOT, so A/F is set to provide best power. I have never seen an engine make best power at 14:1 or leaner. Typical NA engines in very good tune will be around 13.2:1 (I have seen as lean as 13.4), boosted engines tend to be somewhere in the 12's depending on how cautious the tuner is and what kind of fuel you are using.

The biggest problem with piggyback fuel devices is they alter the airflow signal to convince the ECM the engine is doing something different than what it expects to add or subtract fuel. VVTi also looks at the airflow signal to determine best cam timing. If you intentionally corrupt the data to get more fuel, what happens to the VVTi? I have a lot more questions than I have answers for the OEM ECM and how it does what it does. Any embedded system programmers on the board to help solve the mystery?
 

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sorry, come from an airplane background, and we run a little leaner i guess, but we also run 100 octane with a bit of lead... it just supprised me when i looked at the dyno, i was wrong about the rpms... looks like up till 3.5k, the engine is almost running 15.2:1... in the plane, running that lean would cause backfiring, detonation and the works... i'd be worried about leaving the ehaust manifold on the runway.

never wanted a piggyback ecu though... just questioning why so lean in the early rpms
 

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Toyota TCCS uses feedback from the O2 sensor to create long term and short term correction values to fuel trim. Those fuel trim values are carried from closed loop operation into open loop operation.

This means, if the O2 sensor has to add 5% more fuel at part throttle in closed loop operation (where the O2 sensor actively determines "correct" a/f ratio), then when you go to WOT and the ECM is running open loop (no feedback from the O2 sensor) it is adding 5% under the assumption that the engine needs an extra 5%. So if someone had done something to the fuel maps that hadn't yet generated the long term and short term fuel trim values, you could see anomalous a/f ratios above 14.7:1.
 

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I have a question. Assuming you could get wires long enough without throwing off resistance readings. Could you not buy the header and place a high flow cat down the line a ways. I know this would still flow alot less than a non cat system but thats what high flow cats are for. This would resove the problem of a restrictive cat and header. It would just cost alittle more to have the custome system built.
 

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At the hp we're making, the cat is not a restriction. Cat's aren't a restriction until you exceed 400 hp. We're not even close.

Removing the cat to change an EPA approved configuration is illegal, so finding someone reputable to do this might be a little tough.

Don't know what wires you are talking about unless you mean the wires to the O2 sensor.
 

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Yeah the ones on the O2 sensor. I was once told that the computer measures resistance on the newer 2 and 3 wire O2 sensors and that you could not cut and splice in new wire without throwing a code. Im not sure if this is true because I never have tested the theroy in real life. The only time I cut the wires is when I was removing or altering the cat. So it could have been either. Its a funny thing those cats. I removed the one on my dakota after it clogged at about 110000 miles. The shop that I will remain nameless hooked the O2 sensor into the straight pipe and I never got a code. Go figure. I guess Toyota's computer does a good job monitoring things.
 

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Former '05er
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There are no 2 or 3 wire O2 sensors anymore. Haven't been on Toyotas for 17 years. They're all 4, 5, or 6 wires. Measuring resistance for anything other than the heater is pointless, they don't work by resistance.

There are two O2 sensors on all OBDII (all cars since '96) cars, one is used to set a/f ratio, the other monitors the catalytic converter. There is no issue with putting an O2 sensor in the pipe without a cat unless there are two sensors, then you'll set a code and illuminate a CEL.

Removing a cat at 110,000 miles is allowed without any real questions because at that mileage it could very well be clogged. It shouldn't be, but it isn't impossible either. If it fails at less than 80,000 miles, it is under warranty and should be replaced at no charge.
 
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