Best Headers for Power 1st, Sound 2nd
10-06-18, 05:39 PM
#17
Driver
Thread Starter
The point of equal lengths is to ensure all cylinders are making power in the same rpm range. The length of the header primary impacts where the cylinder makes power - low, mid, high rpm. Unequal means they made the tubes to fit in the space available, but it's a compromise design because not all cylinders will behave the same. Yes, equal length means exactly that - the distance the gas travels from the exhaust port to the collector is the same for all cylinders. And no one knows what "long tube" means. It's a marketing term that has little or nothing to do with header design. There is an optimum tube length for the powerband you seek. Shorter tubes favor high rpm torque. Longer tubes favor low rpm torque. Smaller diameter tubes favor low rpm torque. Larger diameter tubes favor high rpm torque. So you play with these parameters until the engine produces power where you want it. So, unequal length headers will make power differently than equal length headers. "Better" is a relative term and has to be decided by the end user. Making more torque at high rpm is usually better for racing and not so great for street driving unless you're happy with winding up the rpm every time you accelerate and you're happy with a shorter service life because the piston rings are going to wear faster at high rpm. Most street applications favor low end torque for driveability, with some notable exceptions like exotic cars.
OK then... let me put you on the spot if I may sir... If it was you, and your wife told you that you must install headers on her GSF because she was going to the track whether you liked or not (this is a respectful joke of course) ...And her GSF already had a very good aftermarket exhaust set up; which header will you (personally) go for?
My inclination right now is a PPE equal length header, ceramic coted with their tune (if they ever break into the 18' engine ECM).
Thoughts?
10-06-18, 06:39 PM
#18
Tech Info Resource
iTrader: (2)
Your route is the same one I would take. The only thing I might do different is buy them uncoated and get a Cerakote shop to coat them with their stuff. I don't think there is anything else out there as durable. I would also run GESI cats because I hate the bad smell, and I think it's irresponsible not to keep your exhaust clean when you can and it's not a power robber the way it used to be.
10-09-18, 12:15 PM
#20
Tech Info Resource
iTrader: (2)
GESI cats were developed for racing, so they don't shell out like everybody else's stuff does. A couple of IS F track guys spit out the guts of their Magnaflow aftermarket cats. No one has had any problems with GESI, but you definitely pay for it.
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texaslexii (10-09-18)
10-09-18, 01:47 PM
#21
Driver
Thread Starter
Your route is the same one I would take. The only thing I might do different is buy them uncoated and get a Cerakote shop to coat them with their stuff. I don't think there is anything else out there as durable. I would also run GESI cats because I hate the bad smell, and I think it's irresponsible not to keep your exhaust clean when you can and it's not a power robber the way it used to be.
https://www.youtube.com/watch?v=SzpS-5OfyUU
https://www.youtube.com/watch?v=SzpS-5OfyUU
Sold! What an excellent suggestion and reply Lance! I have been researching this material "Cerakote" since I read your reply a few days back and it is as impressive as they get. Was not aware of this option for coating materials, thank you for sharing it with us.
Interesting that you mentioned GESi cats as I always had them in mind to incorporate them in my Frankenstein of an exhaust. But back then I had not finalized my decision on which headers (if any) and mid pipes to use and I was worried on them (GESi) acting as a quasi resonator and quieting too much the exhaust. Now I know that I need them, not only because of the smell issue that you talked about, but also because my exhaust is already borderline too loud and adding headers will not make anything more quite... So I also hope that these high performance cats, besides doing their primary function, could hopefully quite down things, even if just a little bit.
Your explanation on equal length header design in function of power was also on point and excellent, thanks for that as well. So if in one hand I had a Novel EL header with its integrated cat at the collector but upstream of the O2 sensors, and on the other hand I had a PPE EL header with a Cerakote coat no integrated cats but with separate GESi cats downstream from the O2 sensors... I will choose the latter. That is why the only issue left with this set up would be to deal with the computer not liking it... For that, I had planned on using the RR tune to simplify the "fix" and in the process get those "6 HP" they talk about. However (bear with me!) if I do the RR tune, I don't think I will be able to recalibrate the engine ECM using Techstream without reverting the tune; in the event that a new version of the 2UR-GSE software comes out.
If my last sentence was true (and it could be wrong), what method or technique would you recommend to "trick" the correspondent ECM into believing that the O2 sensors are reading the right thing? I know there are some methods out there, I'm just interested in your view as the best way to fix this if in one hand you had the RR tune option, and in the other hand you could have any other option.
Thanks!!
10-09-18, 02:16 PM
#22
Tech Info Resource
iTrader: (2)
If you have a cat in place, you won't need to trick anything. The OEM config has wideband sensors before the primary cats and a conventional O2 sensor behind the primary cat, but before the secondary. The only issue is getting the O2 sensor (not the wideband) plugged in because usually you'll run out of wire. If you get the system configured in a way where the O2 sensor is behind the cat and plugs into the wiring harness, you're golden. No need for any trickery.
10-09-18, 06:14 PM
#23
Driver
Thread Starter
If you have a cat in place, you won't need to trick anything. The OEM config has wideband sensors before the primary cats and a conventional O2 sensor behind the primary cat, but before the secondary. The only issue is getting the O2 sensor (not the wideband) plugged in because usually you'll run out of wire. If you get the system configured in a way where the O2 sensor is behind the cat and plugs into the wiring harness, you're golden. No need for any trickery.
Clearly the computer is measuring O2 before the primary cat, and right after. It could care less about a secondary cat which has no influence on the function of the first.
10-10-18, 06:31 PM
#25
Tech Info Resource
iTrader: (2)
Your analysis is exactly correct. You'd need to extend the wires for the secondary O2 sensors to reach behind the GESi cats in the same place as the OEM secondary cats. We learned early on you could delete the secondary cats without the ECM being upset. The tricky part of all of this is the ECM does some testing while the engine is running and compares the results with expected values in a table which is why building a CEL-free O2 sim isn't easy for this platform.
10-12-18, 04:31 AM
#26
Driver
Thread Starter
Your analysis is exactly correct. You'd need to extend the wires for the secondary O2 sensors to reach behind the GESi cats in the same place as the OEM secondary cats. We learned early on you could delete the secondary cats without the ECM being upset. The tricky part of all of this is the ECM does some testing while the engine is running and compares the results with expected values in a table which is why building a CEL-free O2 sim isn't easy for this platform.
10-12-18, 09:42 AM
#27
Tech Info Resource
iTrader: (2)
All good, but you really want the wideband sensors (primary) as close as possible to the collector. They don't tolerate wire extensions well, the signals they generate are in the 10's of microamps range, so wire length is a big deal for them.
10-13-18, 06:28 AM
#28
Driver
Thread Starter
I understand and see your point on modifying the length of the cables for those primary sensors, therefore I will not consider it as an option. I'm finally starting to see some actual mechanical benefits to the Novel headers, they do have that integrated cat at the right place for those cables and they will solve this general problem that we are talking about here. I'm just not convinced that they are "powerful" enough to justify the cost. Lance, do you know if these PPE headers have a "port" or a place to connect these primary sensors too? I think you can see where I'm going here. That is to say that if one wants to build a set up where you have an EL header with no integrated cats at the collector (like Novel does), and you want to avoid a "CEL-Free O2 Sim" or an RR tune as a way to keep the computer happy, you will obviously have to add a cat (GESi) somewhere in the system. Then, you will need to move the secondary sensors to read downstream from those GESi cats, and have the primary sensors just read upstream from them at the collector since one should not attempt to move their OEM location. This means that if the PPE headers did not have a "port", or place, or way, to attach those primary sensors to them, this idea will not work as depicted here. At that point, you can still make it work, but you will need to use the RR tune or some sim. Can you think about this and tell if I'm wrong here? And also, if you know what people do to their primary sensors when they replace OEM headers for aftermarket ones. I don't know if you did this to your ISF.
10-13-18, 08:44 PM
#29
example on the extensions: 22 gauge multi conductor wire has about a .01614 ohms per foot. Multiply that by 100 micro amps and you get a voltage difference of 0.000001614 Volts. A very small and trivial amount for these applications.
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TARS (10-23-18)
10-13-18, 09:03 PM
#30
I understand and see your point on modifying the length of the cables for those primary sensors, therefore I will not consider it as an option. I'm finally starting to see some actual mechanical benefits to the Novel headers, they do have that integrated cat at the right place for those cables and they will solve this general problem that we are talking about here. I'm just not convinced that they are "powerful" enough to justify the cost. Lance, do you know if these PPE headers have a "port" or a place to connect these primary sensors too? I think you can see where I'm going here. That is to say that if one wants to build a set up where you have an EL header with no integrated cats at the collector (like Novel does), and you want to avoid a "CEL-Free O2 Sim" or an RR tune as a way to keep the computer happy, you will obviously have to add a cat (GESi) somewhere in the system. Then, you will need to move the secondary sensors to read downstream from those GESi cats, and have the primary sensors just read upstream from them at the collector since one should not attempt to move their OEM location. This means that if the PPE headers did not have a "port", or place, or way, to attach those primary sensors to them, this idea will not work as depicted here. At that point, you can still make it work, but you will need to use the RR tune or some sim. Can you think about this and tell if I'm wrong here? And also, if you know what people do to their primary sensors when they replace OEM headers for aftermarket ones. I don't know if you did this to your ISF.
A catalytic converter's efficiency is a function of heat. The hotter the exhaust gases the more efficiently the catalyst will catalyze the exhaust. The hottest point is at the collector so the most efficient a cat will get is right after the collector. This is why the monitored cats are right at the collector on factory manifolds. After the collector the temperature drops quickly, so the further you move the cat, the less effective it will be. Because of this, simply moving the downstream sensors after your cats that are 3-4 feet from the collector will not keep the CEL off. You will still need a simulator, conditioner or to extend the sensor out further to trick the ECU. (or RR tune with monitors shut off)
Having a cat in the header like Novel will keep the CEL off because it is in the hottest spot and very efficient, but at the cost of making more power. Using a cat-less header like ours will give a larger power gain, but will require tricking the ECU.
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