Are Headers Do-Able For Street This Way?

[Homeboy981]

I'm trying to get more performance out of intake and exhaust systems. To that end I have been shopping Exhaust Headers for some time. However, IF you want to pass inspection, you cannot remove the PRIMARY CATS. I have looked into re-programming, mini-cats (about an inch or two long), spark plug de-foulers (moving out of exhaust stream)….ALL do NOT seem possible.

Then I hit on this….buy Performance Headers and have a muffler shop weld in the old cats from previous system. Is there any reason that should not work? The tube diameters are similar, they can weld in the bung holes for O2 sensors…and we're good, right?

If not, please explain….gently!

[Johnny Danger]

The boxster, as you probably know, was 2 sets of cats. Technically you could resort to a single header design and reroute the O2 sensors to the secondary cats. Keep in mind, the secondary cats are just as restrictive (and maybe more if they' share the same part as a 996) as the primary cats. With that said, there's really nothing to be gained as far as performance is concerned. As I've said numerous times in the past, there's no short cut or inexpensive way to improve upon the oem exhaust system .

[Homeboy981]

Hey @JD,

This IS DEFINITELY not a "short cut", more like several difficult cuts, followed by welds and such.

I already have Cat Deletes, so my secondary cats are gone!

But having a better "outflow" design, in other words, longer tubes for EACH of the cylinders helps, doesn't it?

Don't longer tubes ALWAYS solve most problems, particularly from the exhaust? Kidding about that but VERY SERIOUS about trying this. If it is worthy. Know anyone who has done it?

Thanks!
Mark

Originally Posted by Johnny Danger

The boxster, as you probably know, was 2 sets of cats. Technically you could resort to a single header design and reroute the O2 sensors to the secondary cats. Keep in mind, the secondary cats are just as restrictive (and maybe more if they' share the same part as a 996) as the primary cats. With that said, there's really nothing to be gained as far as performance is concerned. As I've said numerous times in the past, there's no short cut or inexpensive way to improve upon the oem exhaust system .

[The Radium King]

if you want longer tubes for each cylinder, they why not put the cats on your mid-pipes instead of your headers? if you buy that logic, then you can re-install your old mid-pipes (they might be of a restictive diameter, however) add cats to your current aftermarket midpipes, or buy a set of midpipes with sportcats from one of many vendors. either way, you would probably need to add a bung after the cat and extend your sensors.

another option is to wait for che. from all reports a 987/cayman exhaust will fit on a 986. che will be selling catless headers for the 987 shortly (for some odd reason there are currently no cheap chinese headers for the 987 like on the 986). then you can just find an oem take-off for the mid-pipes and muffler - better sound, bigger diameter, cats located well downstream at the muffler.

[Johnny Danger]

Originally Posted by Homeboy981

Hey @JD,

This IS DEFINITELY not a "short cut", more like several difficult cuts, followed by welds and such.

I already have Cat Deletes, so my secondary cats are gone!

But having a better "outflow" design, in other words, longer tubes for EACH of the cylinders helps, doesn't it?

Don't longer tubes ALWAYS solve most problems, particularly from the exhaust? Kidding about that but VERY SERIOUS about trying this. If it is worthy. Know anyone who has done it?

Thanks!
Mark

Yes, on the longer, equal length primaries on the headers. However, it has been my experience that going completely catless reduces low end to mid range torque. There needs to be some back pressure.

[Mrmaddbrad]

I feel as though you're focusing on the wrong places for horsepower. If you haven't already, you should look into the intake and ecu remapping that Pedro's Garage offers. I believe they have labeled this as the "TechnoKit". For less than $1500, they claim almost 40hp.

You'll be looking at spending close to that on the exhaust upgrade you are describing. And yes, you would be able to pass a smog inspection, but I feel you're not really thinking about this in a proper sense. As Mr. Danger has states numerous times, there is no cheap exhaust upgrade. Although I cannot see pouring as much money into my exhaust system, as he has into his, i must say his is done right. And as far as tastefully modified boxsters goes, his is the bench mark.

To be completely frank, welding your old cats onto new headers, is going to not only look tacky, but will drop your performance gain of those headers significantly. If they claim 15hp, that is of course with the cat delete. Putting them back on could significantly reduce that performance gain.

In my mind, as johnny has already stated, there is no cheap way, or short cut to a proper exhaust modification on 986 exhaust systems. And although it may be hard to face, what you are describing is a short-cut. Although not cheap or fast, you are only attempting it to avoid the extremely expensive and long process of doing it "right".

Hope this is helpful,
Brad

[Homeboy981]

Hi @Brad,

Not what I wanted to hear, but maybe I needed to hear it.

You may be right. However, I am ONLY looking at $150 for headers and can easily take the the pieces down to my local muffler shop and have him do the "Cat swap" for less than $100. I already have cat deletes and have a Top Speed Pro-1 Cat Back Exhaust in my sites. I DO understand the exhaust WILL NOT flow as well as FULL Headers and likely there will be some lost HP, as a result of keeping the cats in there, I cannot afford to do without them totally…yet.

The reason all this is becoming necessary is because I have the intake portion just about dialed in. While the Pedro mod may be better for a stock intake, there is nothing stock - or EVEN AVAILABLE, that is LIKE my intake. I have my Stage 2 Intake completed (HUGE Air Filter, 4" silicone tubing to 3.25" with the MAF housing RIGHT BY the Throttle Body). It is flowing a TON of air! ECU mapping is next.

It may seem like a 'short cut' or "tacky" to some but compared to the cost of hi-performance cats, more than a grand more….this is much MORE do-able ON A BUDGET.

I DO however value your opinion and will take it under advisement. I may be saying, "Curses I really wanted to get Headers" but, it may be an exhaustive pipe dream, that is the reason I asked the ????.

I was told the Air Intake system would LOSE power too….but it doesn't and I am a happy camper for only spending a couple hundred and some time in R & D (therapy for me).

So, if anyone has a way it CAN BE DONE, or you have been able to make the Headers work, without breaking a fragile piggy bank, given the set up I have…please enlighten me. Or, maybe it will be an 'exhaust pipe dream'. Thanks!

[BYprodriver]

The reason the converters are positioned as close as possible to the exhaust ports is to minimize the time it takes them to heat up to operating temp. Extending warm up time for converters will lite the CEL. To give you an idea how critical this is, Mercedes doesn't use 4-valve per cylinder heads on most of their engines because using only 1 exhaust valve per cylinder allows more heat retention for quicker warmup.

[BYprodriver]

Opened up my oem manifolds a little by grinding down the welds at the entrance & exit point. Effectively increased minimum diameter over 3/8". Every little bit helps, especially with 3.6L

[Johnny Danger]

Originally Posted by Homeboy981

Hi @Brad,

Not what I wanted to hear, but maybe I needed to hear it.

You may be right. However, I am ONLY looking at $150 for headers and can easily take the the pieces down to my local muffler shop and have him do the "Cat swap" for less than $100. I already have cat deletes and have a Top Speed Pro-1 Cat Back Exhaust in my sites. I DO understand the exhaust WILL NOT flow as well as FULL Headers and likely there will be some lost HP, as a result of keeping the cats in there, I cannot afford to do without them totally…yet.

The reason all this is becoming necessary is because I have the intake portion just about dialed in. While the Pedro mod may be better for a stock intake, there is nothing stock - or EVEN AVAILABLE, that is LIKE my intake. I have my Stage 2 Intake completed (HUGE Air Filter, 4" silicone tubing to 3.25" with the MAF housing RIGHT BY the Throttle Body). It is flowing a TON of air! ECU mapping is next.

It may seem like a 'short cut' or "tacky" to some but compared to the cost of hi-performance cats, more than a grand more….this is much MORE do-able ON A BUDGET.

I DO however value your opinion and will take it under advisement. I may be saying, "Curses I really wanted to get Headers" but, it may be an exhaustive pipe dream, that is the reason I asked the ????.

I was told the Air Intake system would LOSE power too….but it doesn't and I am a happy camper for only spending a couple hundred and some time in R & D (therapy for me).

So, if anyone has a way it CAN BE DONE, or you have been able to make the Headers work, without breaking a fragile piggy bank, given the set up I have…please enlighten me. Or, maybe it will be an 'exhaust pipe dream'. Thanks!

Even if you were able to accomplish this (and I don't think that you can for the reasons that BYprodriver gives), you're still stuck with very restrictive 400 cel cats .

[Bfan]

Hi guys and greetings from Reykjavik.
I think this is an very interesting subject. Am I right in thinking that if Homeboy981 goes through with his plan and has the secondary sensors deleted when he gets the remap and simply removes them, he:

-will not get the dreaded CEL,
-he will pass smog test,
-he is likely to loose some mid range torque
-it will take the cats longer to warm up, but there are no secondary sensors anymore to trigger CEL,
-he will not get a warning if the cats fail in the future without secondary sensor (not suchs a big deal!)?

JD or BPD, please enlighten me if I am misunderstanding something

[Homeboy981]

Thanks to @The Radium King for this comment, which should shed some light on an exhaustive problem:

"each bank of 3 cyls has: headers - o2 #1 - precat - 02 #2 - mid pipe - secondary cat - muffler.

purposes are:

o2#1 - ecu uses to set fuel trims.

precat - only found on north american cars with tougher emmission standards. required only for start-up emissions (like the secondary air injection pump) the precat is designed to warm up quickly before the main cats get working.

02 #2 - used by ecu to check to see that the precat is working. again, only found on north american cars. can be fooled with minicats or spark plug anti-foulers. some guys get a 'rest of world' (row) base flash that doesn't look for the o2 #2 (also allows you to delete the secondary air injection pump and start the car without the clutch in, but will not pass obd emissions testing). others get a tune of their north american base flash that tweaks the o2 levels being sensed by o2#2 so that it passes emmissions without cats.

secondary cat - this is the main cat for the car.

exhaust, like intakes, wants to move as much air as possible at high rpm, but benefits from the back pressure caused by decreasing diameter piping, cats and muffler at lower rpm - your decision based on how you drive. raby says that one of the best mods for the $ is a cheap set of headers. this makes sense to me, as i'd rather have my restrictions further downstream (ie the mid pipes instead of the headers) to allow flow to establish itself.

fortunately no emissions testing where i am from. if you just have to pass obd, then going catless with the spark plug anti-foulers should work. if you have to pass visual, there are techniques to gut your cats that might work."

TRK not only does math well, also explanations….so I thought I would share.

Please feel free to elaborate on ANY ideas at this point. Headers were SUPPOSED to be my Christmas present - would HATE to get a TV or something….

Thanks for EVERYONE's opinion!!!

[tony_fury]

Originally Posted by Homeboy981

Please feel free to elaborate on ANY ideas at this point. Headers were SUPPOSED to be my Christmas present - would HATE to get a TV or something….

Thanks for EVERYONE's opinion!!!

Do you have the Durumetric software and cable?
That could be your Xmas replacement..
T

[Homeboy981]

Originally Posted by tony_fury

Do you have the Durumetric software and cable?
That could be your Xmas replacement..
T

Hey T,

Yes. That is next! We are planning a 'group buy' for the software and Durametric software that allows changes. For now I have borrowed, thanks to @Kenny Boxster, the 'read only' version of software to check my numbers on the intake.

The FULL writeable software is close to a grand (more than my Christmas budget for a tree and all)…..unless SOMEONE else has a source for it?

[Topless]

Definitely not "Smog legal" in Calif. It might pass an inspection by someone who doesn't look at em but the CHP won't let it fly. No knowledge of TX smog rules for street legal cars.

From CARB:

"A. Catalytic converter falls under California anti-tampering law. The law is designed to prevent tampering with pollution control devices on California vehicles. The anti-tampering law is Vehicle Code Section 27156 and covers all pollution related systems and devices on a motor vehicle. A violation of this law may also include a parallel violation of California Business and Professions Code Sections 17200 and 17500. Judges usually impose penalty based on the severity of the offence and whether a repeat offender is involved, and a fine of up to $2,500 for each violation may be assessed, as well as some jail time."

[BYprodriver]

Originally Posted by Bfan

Hi guys and greetings from Reykjavik.
I think this is an very interesting subject. Am I right in thinking that if Homeboy981 goes through with his plan and has the secondary sensors deleted when he gets the remap and simply removes them, he:

-will not get the dreaded CEL,
-he will pass smog test,
-he is likely to loose some mid range torque
-it will take the cats longer to warm up, but there are no secondary sensors anymore to trigger CEL,
-he will not get a warning if the cats fail in the future without secondary sensor (not suchs a big deal!)?

JD or BPD, please enlighten me if I am misunderstanding something

Hi Bfan, this is generally true except, engine efficiency+ quality & surface area of cat cells determines emissions reduction to pass emissions test. He will lose low rpm power transitioning to gains somewhere in mid range & up.