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Hi, i'm new to the forum. Just bought an 05 997 c2s mt. I'm wondering if x51 headers and air box are worth to buy? If not, what brands are you guys suggesting. Hope people here can share the experiences.
air box alone will not give you much. I do not think it is worth to touch intake at all unless you want to replace upper deck to make dual air inlets and also replace throttle body to let more air in. it is expensive and will not give much.
x51 headers are good modification for track cars, again, if you mostly will run car on the street it is questionable to what degree you want to spend money to improve performance of the hi rev section from 5k to 7k RPM.
If you are building a track car then typical approach would be to put in x51 headers and fabspeed or AWE 200 cell cats. mufflers do not do anything, so if you go with 200 cell cats - keep stock mufflers on. if all you need is more aggressive sound for the street - do not touch headers and cats, just get any aftermarket mufflers, borla, awe, fabspeed.
Now i have the fabspeed muffler, i plan to get the headers and softronic flash, so after i add 200 cell cats with K&N or BMC filter will be a good set up?
I had k&N filter and on a track got a MAF related CEL on a hot day, I think when filter is new on a hot day even a small amount of oil it has on it sometimes enough to put residue on the MAF sensor and cause issue. I would recommend to leave airbox alone, just make sure you have brand new clean stock filter in it.
aftermarket mufflers and any 200 cell cats will sound very loud. you may want to use stock mufflers with 200 cell cats. I run fabspeed x-pipe and so far everything was fine, with exception that I need to flash stock ECU code before going into state inspection station as they now have digital 'passport' for how ECU systems should look like on a stock car and if it does not 'match' they fail you automatically but if may be MA only thing.
put on x51 headers at same time when you put 200 cell cats and after that flash the car. during cats mount disconnect battery to reset ECU, as sometimes car feels very sluggish after cats replacement if it did not have time to relearn. preferably flash it with softronic right after you connect power back after cats install.
it is important to connect battery to decent charger during softronic flash as sometimes it may switch from normal 'fast' method to 'slow' and then it may take up to 1 hr, you do not want to car battery die during ECU flash, it will kill ECU. but do not worry, I flashed my car back and forth a lot of times and so far it was OK every time.
I can provide some good feedback on what I have tested with 997's. The X51 headers, with all else being stock, will add horsepower and torque across the entire rev range. You will not lose anything over the factory 997 S headers, which are garbage.
Fabspeed's long tube headers provide the same gains up top that the X51 provide, but give more mid range torque. It is unbelievable what our headers do on a bone stock 997 S - even with the stock cats. See dyno chart below.
Regarding the intake, I would say that unless you have the GT3 style decklid, save your money for the upcoming Fabspeed Dual intake. Attached are some pictures.
For the headers, is the equal length better or regular one better?
People will tell you otherwise but after experiencing both I feel the difference is marginal.
I have done ECU tune, full exhaust and intake tube -- my car sounds great now but performance-wise the changes were minimal. I am extremely skeptical to the massive gains I see on these charts for our NA cars.
graph above is quite good as it shows the problem any stock car has - that drop of torque from 5K to 5.5K RPM. it feels on track and is very annoying.
that is what you need to fix with softronic tune.
headers help but 200 cell cats are the key as all in all it is all about amount of air your motor pushing via exhaust at hi rev section and about ability for the ECU to accommodate that available air.
here is link to my pre and post tune dyno. note how blue line went up and how curve changed. note how pink/purple (timing) lines changed as well. it makes a ton of difference.
power increase does not matter as much as this curve line form. all you need for track is an as linear torque line as possible.
for street only driving there are downsides, you get less backpressure in low rev section, softronic tune does not use after-cats O2 sensors and resulting motor feel is not so 'silky-smooth' as with stock tune, so it you have to drive car a lot on street at crawling speeds in traffic you may not like it at all. I now have a tendency to flash it just for DE events into softronic and then is I have no events coming for a month or so I flash it back. not sure how many flash cycles can ECU tolerate but it is way easier to drive on the street with stock flash. it does not have this raw power when you step on gas all the way but it is way smoother and maintains RPMs way better when you downshift from 3rd into 2nd.
it's just i found an used x51 headers with half price of the new one, so i'm deciding if i should get it first. sounds like 200 cell cats is a better mod for hp and torque, then i might be considering getting it first. do u guys recommend any brand for the 200 cell cats?
100 cell cats will most definitely give you CEL code with stock ECU tune. You do not want that to happen.
just from labor perspective it is simpler to unbolt both headers and cats one time if you decide to replace both. just be extremely careful with header bolts into block if car is old and it was never touched before.
also, not because I am paranoid, I am not a fan of used headers. this part usually never gets unbolted if it had no issues. double check if mating surface to the block is not warped. you will need new gaskets and, again, be extremely careful to those bolts.
when I had to remove my cats I ended up twisting off and braking off heads from 4 bolts out of 6 in there but it was between headers and cats so no big deal, I just replaced them all.
you do not want to brake off a head from a header bolt leaving its body the block. I did that once on my old bmw and it was a major, major PITA to extract it out.
also, I would recommend to get extender tubes for after-cat o2 sensors. it is typically not needed for 200 cell cats but will not hurt as it costs peanuts and adds on insurance that your stock ECU tune will not give you error codes when it will be inspection time. you need only 2 for after-cat sensors only.
it looks like this, imho they all are same, just make sure it is of same thread as O2 sensor for our 997 p-cars. http://www.uspmotorsports.com/Torque...-Extender.html
graph above is quite good as it shows the problem any stock car has - that drop of torque from 5K to 5.5K RPM. it feels on track and is very annoying.
that is what you need to fix with softronic tune.
headers help but 200 cell cats are the key as all in all it is all about amount of air your motor pushing via exhaust at hi rev section and about ability for the ECU to accommodate that available air.
here is link to my pre and post tune dyno. note how blue line went up and how curve changed. note how pink/purple (timing) lines changed as well. it makes a ton of difference.
power increase does not matter as much as this curve line form. all you need for track is an as linear torque line as possible.
for street only driving there are downsides, you get less backpressure in low rev section, softronic tune does not use after-cats O2 sensors and resulting motor feel is not so 'silky-smooth' as with stock tune, so it you have to drive car a lot on street at crawling speeds in traffic you may not like it at all. I now have a tendency to flash it just for DE events into softronic and then is I have no events coming for a month or so I flash it back. not sure how many flash cycles can ECU tolerate but it is way easier to drive on the street with stock flash. it does not have this raw power when you step on gas all the way but it is way smoother and maintains RPMs way better when you downshift from 3rd into 2nd.
The only reason tuners must disable the rear O2 sensors is because the cats being used are not up to the task of cleaning the exhaust with half as many cells as factory (or even less - or none!).
This will cause issues for those that have to go throught emissions testing, as the rear O2 monitors will not be in "readiness" mode, and the car will fail.
This is one of the primary reasons we use HJS catalytic converters - no check engine lights as the cats are able to clean the exhaust well enough.
BTW: 100 cell cats are almost useless. On most cars, there is no performance benefit over a 200 cell cat, and, a 100 cell cat is more prone to fail as it is not as strong internally.
>This will cause issues for those that have to go throught emissions testing
I think going forward in most states it will be a big problem. not only they 'test' for presence of this system, what I personally had to go over this season was the 'fail' status with no explanation why at test station with redirect to proceed to state owned 'special' inspection station they sent all 'flashed' cars over as from state perception it is illegal to operate a vehicle with 'flashed' ECU. I do not want to escalate discussion regarding legality of this state legislation and their methods but it is what it is.
If car`s digital 'signature' of available systems does not 'match' profile or gets changed from last time you went over state inspection this new system in MA automatically fails you and forces to go to this 'inspection' facility so they could sniff whole car over back and forth.
09-16-2013, 07:47 AM
Are x51 headers and air box worth to get?
