I love the work everyone has done with the tC -- but I am curious if there are any plans for someone to come out with a new 4-2-1 header that has the primary O2 situated in the "1" section of it. Ideally, this new header would not throw a CEL and not produce rasp...

And I really don't want to have to go and get a degree in fluid dynamics, a copy of Mathematica and AutoCAD, and design the b!tch!n thing myself -- that would take too long :D

Thanks guys,
Ryan

 

^im with u, lol im really want someone that'll make a header that wont sound like a civic, thats why i dont have one now.

 

There isn't plans to make a 4-2-1 header like you're asking because it just isn't possible. If you increase flow dynamics for performance you increase noise (read: rasp). primary CEL problems are caused by the second bank sensor throwing a code because of the increased flow from the missing cat. You can either put a cat between the engine and the second sensor to slow down the flow to stock levels which will negate performance, or relocate the second sensor out of the main flow stream so it reads the same volume as stock with increased flow and one deleted cat. Monster Motorworks is working on a solution to move the second sensor.

Keep in mind unless there is a flaw in design, every modification you do is just a compromise. For a header for example, you are deleting a working catalytic converter from the car (a federal offense mind you, no matter how small) increasing flow which will increase performance at the cost of emissions, and also generate more heat from velocity, and reduce reliability in the header from the increased heat and multiply the cost compared to the stock part. Ideally, there is a balance between flow, noise and performance. If you want to reduce rasp from the header, you can put a resonator in the exhaust midpipe which will dampen (read: slow down) the exhaust flow at the cost of decreased performance.

Oh, and FWIK, header's don't cause rasp or increased unwanted noise, but they do cause that side effect from doing their job and flowing better which would need to be dealt with if that is not what you're after.

 

Very well put man .

 

Increased flow?? Since when is a 02 sensor a flow sensor? Reason why you get a CEL is cause there is no CAT doing its job reducing CO and NOx emissions. While it is true that a CAT does effect flow, it is not the flow change that trips out the ECU, its the 02 content in that flow, thus the name "02" sensor.

 

OK, now this brings to mind even more questions. I now understand that the rasp is actually flow noise, and that the antifouler "mod" simply makes the 2nd O2 sensor read a value comparable to that of a system with an intact pre-cat. Now, here's what I'm thinking:

1st O2 sensor is what the ECU tunes off of. I would really like to see a header that positions this sensor to read the combined exhaust stream, not just from one cylinder.

As far as the cat goes, to hell with it. I don't live somewhere with sniffer or visual inspections.

2nd O2 sensor - a sim would take care of this, I think, since FWIK it only gives something to monitor the status of the pre-cat.

Thus, the request becomes such:

A 4-2-1 header with the O2 sensor in the "1" section...
-and-
A sweet S-pipe :D O2 sensor location not important since a sim could be used...
-and-
A cat-back exhaust system incorporating a hi-flow resonator (this would reduce rasp and replace/delete the second ULEV cat) and a nicely tuned muffler.

I know that there is nothing that can make a four-banger, no matter how efficient or tuned, sound like a crazy eight with twin quad-barrel carbs, but I am trying to plan a hi-flow exhaust that doesn't make the car sound like a weed trimmer with NOS...

Any thoughts, gripes, rotten tomatoes?

 

Thats the "Air/Fuel" sensor, it actually is a different type then the second sensor in the system, your typical 02 sensor.

Okee, but that there is a federal offense!

Very true... From the techinfo.toyota.com technical details of the system, looks like the voltage the ECU is expecting from the 02 sensor is between .1 and 1 volt. with the mid point being the ideal A/F ratio. The voltage the ECU is expecting from the first sensor, the A/F sensor, is between 2.2 and 4.2 volts, with the midpoint between those two voltages again being the ideal A/F ratio of 14.7. I am interpreting this information from the chart on page EG-41.

I like your ideas, especially the one about putting the first A/F sensor in a location where it will be able to read from ALL the cylinders instead of just one. Thats my major gripe about all the headers on the market now.

My idea about the CEL issue would be to do one of a couple of different things. If you are keeping the stock exhaust, from the S-Pipe back, you still have the ULEV mandated second cat there, maybe move that second 02 sensor to a location after that cat and see if you have CEL issues. Or, if you are going with a full exhaust, go with a high flow cat and again place the second sensor, the O2 one, after the high flow. That way that sensor is still behind a cat, and the ECU should be happy.

And since you are still retaining some sort of cat, maybe a resonator wouldn't be needed as much? Are people having issues with rasp with a header w/stock or axle back? Meaning you still have the stock 2nd cat?

So ideally, this is what I would like to see.

1) First sensor bung welded in a location where it will read exhaust from ALL CYLINDERS.
2) High flow cat located after s-pipe, with sensor bung welded after it, for the O2 sensor.

Should still see performance gains compared to stock cause you are getting rid of 1 cat(still a federal offense? hehe), and replacing the second with a high flow. Also, should take care of the CEL issues.

 

Jowie, I'm with you on this... theoretically, you get the benefit of sampling all four exhaust charges, no CEL since the 2nd O2 is still behind a cat (prolly would need an extension for the wiring harness though), and the benefit of one less cat in the system. For those of us that are adamant about the performance loss, perhaps the system could come either with a cat or a simple resonator? Now, I think, it is in the hands of the gurus at AlphaWerks, DC Sports, MonsterMotorWorks, and the others that have the much-needed access to a mandrel bender...

[shameless plug]
And if any of you guys does develop such a beast conforming to the above specs, I would be happy to lend you my vehicle for install and testing... provided I get to keep the setup after the dyno pulls :D
[/shameless plug]

Regards,
Ryan

 

^i'll lend my car too

 

TTT ~ Is there any fabricators that have seen this thread?

 

this is something im planning for this winter im just waiting to get my tig becouse the mig cant weld the in the tight spots i will need to get in (1 more week) then im doing the intake manifold and porting the t/b and after all that its going to be a header but im baseing it off a compresion check and then doing the volum of each primary an equal volume but based off the compresion check i think it should give good gains but should also be a pain in the a$$ lol. i have done alot of metal work and fabracation stuff before but this will be on a mutch smaller scale then the intakes, exhausts,gokarts, and the caterpillar excavators i used to build back when i worked there.

i will keep every one updated on this like i did with my intake but i need my tig to stop getting delayed or i might have to start with the mig. and way off topic but the dyno for my intake will finaly get done it was supposed to happen 2 weeks ago but this damn 900hp mustang hoged the dyno all day so i had to reschedual



check out http://headerdesign.com and also honda-tech.com has some good stuff in the fab section