K-Series Engine Headers FAQ

[Gro Harlem]

Decided to finish writing this FAQ i started writing awhile ago. Mainly b/c I'm sick of people asking about headers constantly.

And for the record, the dyno gains that I posted are based on 2.5 liter dynos. Obviously depending on what other mods you have installed, you will see higher or lower gains. Some of the people had KL-ZE's although I must say most of the ones I sampled didn't.

And also for the record....YES these FIT the K8 AS WELL!! The fact is, the K8's stock exhaust manifolds are stampled "KL01". My KL-ZE even had "KL-01" stamped on them. The only fitment issue on the MX-3 is the catalytic converter. It needs to be pushed back about 2" since the Probe / MX-6 has a completely different chassis w/longer exhaust sytem.

K-Series Engine Header FAQ:

Here is a list of the headers available and what I've found (from researching ProbeTalk):

Brospeed / Bosal Headers:
Price: $350-450
Description: Stainless steel construction. Short equal-length primaries. Equal-legnth Y-pipe that secures with a balljoint
Primary Size: 1.625" (outer)
Outlet Size: 2.5" at collector, then tapers down to 2.125" (inner) 2.25" (outer) to fit the stock cat size (for probes at least)
Power Gains: Dyno results varied from 4-11whp over stock. Torque gains were from 5-8 ft lbs. Gains were particularly good from 3500 and up. Peak power gains surpass hotshots but don't quite reach pacesetters results.
Sound: Described as raspy by some ProbeTalkers. Sometimes Rattles from 2000-2500rpm's due to balljoint design (lack of flexpipe)
Fitment Issues: fitment is good according to people on probetalk with these headers


Pacesetter:
Price: $180-240
Description: Mild Steel Construction. long unequal-lengthprimaries. Unequal-legnth Y-pipe that secures with a balljoint
Primary Size: 1.5" (outer)
Outlet Size:
Power Gains: I've seen varying results. As much as 17whp to as low as 7whp gains. Torque gains were anywhere from 5-10 ft lbs.
Sound: Very Raspy.
Fitment Issues: Pacesetter updated their design in 2004 for better fitment. Apparently there is still problems with the Y pipe bolting up to the primaries. The O2 sensor bung placement issues have been fixed however.

Hotshot:
Price: $410-500
Description: Stainless Steel Construction. Short equal-length primaries. Equal-legnth Y-pipe that contains a flex-pipe.
Primary Size: 1.625" (1 5/8")
Outlet Size: 2.5"
Power Gains: Varying results from 4whp to as high as 13 whp. Torque gains seen have been consistent from 5 to 8 ft lbs.
Sound: Keeps the tuned sound of the K-series engine. Best choice for those who want the best sound
Fitment Issues: Fitment is great!

SSAutochrome:
Price: $175-200 on ebay
Same as pacesetter generation 1 headers but made with stainless steel which is less likely to rust. ALso the primaries are 1.625" (1 5/8") instead of 1.5". The fitment is the same however. O2 sensor bung placement issues & difficulty with the primary-y-pipe flange were voiced by people who bought these headers.

OBX:
Price: $300 on ebay
Same as Hotshot headers. Stainless steel construction, decent welds, flexpipe, nearly identical to the hotshots. Fitment is also good.

Also note that SSautochrome sells these exact headers and uses their brandname on them. The ones I received from ebay came in a ssautochrome box with stickers. SSautochrome posted messages on ProbeTalk about redesigning their header design and I guess they decided to just knock off the hotshots


I have the OBX headers on my car and they fit fine with no issues. O2 sensors clear everything. My EGR bung is plugged so I don't know if that fits properly, but other than that, I'm satisfied. I've had them installed for 9+ months and they show no signs of rust, however the typical purple/orange/blue/green discoloration has occured on the primaries. I live in an area where it snows & they salt the roads and I'm particularly surprised that they show zero signs of corrosion so far.


Other things related to headers:

Balljoint VS Flexpipes:
Since the engine moves independently from the body when it accelerates & decelerates it generates movement. Since the exhaust is attached to the body there needs to be a little bit of give in the exhaust system. This is typically done by a flexpipe on most cars. However with the Bosal, Pacesetter & SSautochrome headers, a Balljoint. These are cheaper to manufacture but are more prone to leaking. You may have to re-tighten the bolts securing the balljoint periodically to keep it from leaking. Flexpipes with a flange are virtually leak-proof assuming you use a new gasket & tighten the bolts to spec.

Primary length:
Longer primaries always spell higher RPM power for any engine, but they can also reduce the gains and possibly remove power from the lower-midrange RPM's. Shorter primaries are good for low-midrange power especially, but can't produce outrageous high-RPM gains. This is why the pacesetter headers make the most power of all of the 3 designs.

Construction:
The type of alloy that is used plays a role in how long the headers will last before they corrode. Mild-steel is very prone to corrosion and WILL rust almost immediately upon exposure to the air. Pacesetter coats their headers with black paint but the paint quickly burns off and rust begins within 2 weeks. Stainless steel is less likely to rust but will begin to in the winter months when salt is thrown on the roads. Unless you live in colder climates, there shoudlnt' be any concern buying mild-steel headers or exhaust peices. Also, exhaust manifolds can heat up to well over 500 degrees. Polished Stainless steel has a tendency to discolor in these kinds of temperatures and will appear a swirly purplish blue color relatively soon after installation.

[lakersfan1]

You should also mention in this and the PT thread that smaller primaries help the Pacesetters also. Too big is bad, as you're trying to get suction going to actually suck the air out of the cylinder. It's like drinking a soda through a normal straw and trying one of those giant a-- novelty straws that really don't work very well.

[ScooterBovine]

So... other than the ball joint "flaw", Pacesetter is the way to go for overall power, unless you are worried about the sound?

[MarkMoore]

correct me if i'm wrong, but i think he also said the pacesetter gets better low-mid range RPM power, and less high RPM power because of the shorter primaries... that's also something to consider i guess...

so for the pacesetter headers, the ones that'd fit would be the g7161 ones listed under the mx-6?
http://www.pacesetterexhaust.com/headers_detail.htm

[Yoda]

I see several misconception that should be cleared up. All the headers mentioned above have there good points and bad points unfortunately the bad seems to cancel out most of the good. Although not mentioned in the original message one thing you see mentioned on a lot of mailing list and BBS is that a header (the whole exhaust system in general) relieves backpressure, but a certain amount of backpressure is still needed for optimum performance. Just the opposite is true. A good header (exhaust system) not only relieves the backpressure, but goes one step further and creates a vacuum in the system. When the next cylinder's exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what is termed "Scavenging" which is that key to a well designed header or exhaust system.

First the explanation of the primary tube length is a little off the mark. When designing a header the first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired redline RPM should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low RPM's. If too small a diameter is used the engine will pull hard at low RPM's but at some point in the higher RPM's the tube will not be able to flow as much air as the engine is pumping out, and the engine will not reaching its potential peak RPM. This situation would require going one size larger in tube diameter. The next consideration is the proper tube length. The length directly controls the power band in the RPM range. Longer tube lengths pull the torque down to a lower RPM. range. Shorter tubes move the power band up into a higher RPM range. Engines that redlines at 10,000 RPM would need short tube lengths about 13" long. Engines that are torquers and redline at say 5,600 RPM's like the KL-DE would need a tube length of 26" for example. This is what is called "Tuned Length". The tube length is tuned to make the engine operate at a desired RPM range. The last consideration is the collector outlet diameter and extension length. The of the secondary pipe will move the engines torque up or down in the RPM range. Longer extension length will pull the torque down into the midrange and decrease peak HP. This is why the Pacesetter headers seem to make more power because of the longer smaller diameter tubes which spikes up the low mid torque.

For reference there is a major differences occur between four cylinder engines and V-6 engines. The four cylinder does have an advantage because of it's firing cycle. Every 180 degree of crankshaft rotation there is one exhaust pulse entering the collector. Where the V-6 it is every 120 degrees. The results on a header on a 4 cylinder is greater because, as one pulse exits the collector, the next exhaust valve is opening and the vacuum created in the system pulls the exhaust from the cylinder. In this ideal 180 degree cycling the collector outlet diameter only needs to be 20% larger than the primary tube diameter. (Example: 1 3/4" primary tubes need a 2" collector outlet diameter.) This keeps the velocity fast to increase scavenging, especially at lower RPM's. Going to a larger outlet diameter will hurt the midrange and low RPM torque.

In the case of V-6 firing order, the pulses fire alternately back and forth from left to right collector. The problem here is the V-6 fires 2 pulses into the left collector, then 1 in succession into the right collector then 2 pulses into the right collector, then 1 in succession into the left collector. If the proper collector outlet diameter is being used like as on header designed for a 4 cylinder engine the two pulses load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine not reaching its potential peek R.P.M. The firing order on a V-6 engine results in the need to use large diameter collectors so the engine will perform well at high RPM's. This is why it is important that the collector Y pipes be equal length otherwise at certain RPMs you could have 3 pulses meet at the Y at the same time resulting in reversion of exhaust gases to the cylinders at certain RPM's Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire RPM range. This is one of the disadvantages of the Pacesetter.

The one problem not addressed is turbulence in the collector. When three or more round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the tubes. The standard method in manufacturing headers is to cap this hole off with a flat plate. This plate in the center of the tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by merging the pipes into a velocity cone inside the collector. This is formed by cutting the pipes at an angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity and directs air flow out the collector. The Bosal and the old D&S Engineering headers are built this way.

In actual fact that cost difference between a Ball joint and a flexible flex-joint is minimal. Most of the European manufactures and Honda have used this type of joint for many years and Mazda has as of the '95 model years use the ball and socket joint as OEM equipment. Generally speaking I have never had any problems with the Ball and socket design. Especially with the once with either a machined bronze or the wire mesh gasket as long as the springs are set to the correct tension. On the other hand the flexible joints have two problems. The ones used in mass production tend to have an accordion pleated center core which loose diameter as they stretch and the folds in the pipe create a lot of turbulence. This is the biggest problem with the OE flex-pipe after about a years they can be as much as 1/8" smaller in I.D. I have recently found a Canadian brand of flexible joint with a flat spiral core but even at wholesale the prices is over CN$50 for a 2" but they flow as well as the ball and socket design.

It is true that mild steel will rust immediately when expose to air. However this is a general statement There are grades of mild steel know as weathering steel that will rust to form a protective layer of corrosion slowing down the rusting process significantly. Stainless steel when used in areas where road salt is used can become pickled where a solution of road salt gets wash over the stl. steel then heated. This causes the Stainless steel to become brittle and loose it's corrosion resistance. The pickling process can also happen to Mild steel but in this case it makes the steel harder and somewhat more corrosion resistant.

[ScooterBovine]

Wow... Can we make this thread into a "Headers FAQ"?

[Gro Harlem]

I see several misconception that should be cleared up. All the headers mentioned above have there good points and bad points unfortunately the bad seems to cancel out most of the good. Although not mentioned in the original message one thing you see mentioned on a lot of mailing list and BBS is that a header (the whole exhaust system in general) relieves backpressure, but a certain amount of backpressure is still needed for optimum performance. Just the opposite is true. A good header (exhaust system) not only relieves the backpressure, but goes one step further and creates a vacuum in the system. When the next cylinder's exhaust valve opens, the vacuum in the system pulls the exhaust out of the cylinder. This is what is termed "Scavenging" which is that key to a well designed header or exhaust system.

First the explanation of the primary tube length is a little off the mark. When designing a header the first consideration is the proper tube diameter. Many people think "Bigger is Better", but this is not the case. The smallest diameter that will flow enough air to handle the engine's c.c. at your desired redline RPM should be used. This small diameter will generate the velocity (air speed) needed to "Scavenge" at low RPM's. If too small a diameter is used the engine will pull hard at low RPM's but at some point in the higher RPM's the tube will not be able to flow as much air as the engine is pumping out, and the engine will not reaching its potential peak RPM. This situation would require going one size larger in tube diameter. The next consideration is the proper tube length. The length directly controls the power band in the RPM range. Longer tube lengths pull the torque down to a lower RPM. range. Shorter tubes move the power band up into a higher RPM range. Engines that redlines at 10,000 RPM would need short tube lengths about 13" long. Engines that are torquers and redline at say 5,600 RPM's like the KL-DE would need a tube length of 26" for example. This is what is called "Tuned Length". The tube length is tuned to make the engine operate at a desired RPM range. The last consideration is the collector outlet diameter and extension length. The of the secondary pipe will move the engines torque up or down in the RPM range. Longer extension length will pull the torque down into the midrange and decrease peak HP. This is why the Pacesetter headers seem to make more power because of the longer smaller diameter tubes which spikes up the low mid torque.

For reference there is a major differences occur between four cylinder engines and V-6 engines. The four cylinder does have an advantage because of it's firing cycle. Every 180 degree of crankshaft rotation there is one exhaust pulse entering the collector. Where the V-6 it is every 120 degrees. The results on a header on a 4 cylinder is greater because, as one pulse exits the collector, the next exhaust valve is opening and the vacuum created in the system pulls the exhaust from the cylinder. In this ideal 180 degree cycling the collector outlet diameter only needs to be 20% larger than the primary tube diameter. (Example: 1 3/4" primary tubes need a 2" collector outlet diameter.) This keeps the velocity fast to increase scavenging, especially at lower RPM's. Going to a larger outlet diameter will hurt the midrange and low RPM torque.

In the case of V-6 firing order, the pulses fire alternately back and forth from left to right collector. The problem here is the V-6 fires 2 pulses into the left collector, then 1 in succession into the right collector then 2 pulses into the right collector, then 1 in succession into the left collector. If the proper collector outlet diameter is being used like as on header designed for a 4 cylinder engine the two pulses load up the collector with more air than it can flow. This results in a very strong midrange torque, but causes the engine not reaching its potential peek R.P.M. The firing order on a V-6 engine results in the need to use large diameter collectors so the engine will perform well at high RPM's. This is why it is important that the collector Y pipes be equal length otherwise at certain RPMs you could have 3 pulses meet at the Y at the same time resulting in reversion of exhaust gases to the cylinders at certain RPM's Unfortunately the large diameter collectors cause a tremendous drop in air velocity, resulting in less scavenging through the entire RPM range. This is one of the disadvantages of the Pacesetter.

The one problem not addressed is turbulence in the collector. When three or more round tubes are grouped together in a square pattern, so a collector can be attached, you notice a gapping hole in the center of the tubes. The standard method in manufacturing headers is to cap this hole off with a flat plate. This plate in the center of the tubes creates dead air space, or turbulence, disrupting the high velocity in the collector. This problem is solved by merging the pipes into a velocity cone inside the collector. This is formed by cutting the pipes at an angle on two sides. When the tubes are all fitted together they form a collector with a "Pyramid" in the center. This has eliminated the need for the square plate and has taken up some of the volume inside the collector, speeding up the air velocity and directs air flow out the collector. The Bosal and the old D&S Engineering headers are built this way.

In actual fact that cost difference between a Ball joint and a flexible flex-joint is minimal. Most of the European manufactures and Honda have used this type of joint for many years and Mazda has as of the '95 model years use the ball and socket joint as OEM equipment. Generally speaking I have never had any problems with the Ball and socket design. Especially with the once with either a machined bronze or the wire mesh gasket as long as the springs are set to the correct tension. On the other hand the flexible joints have two problems. The ones used in mass production tend to have an accordion pleated center core which loose diameter as they stretch and the folds in the pipe create a lot of turbulence. This is the biggest problem with the OE flex-pipe after about a years they can be as much as 1/8" smaller in I.D. I have recently found a Canadian brand of flexible joint with a flat spiral core but even at wholesale the prices is over CN$50 for a 2" but they flow as well as the ball and socket design.

It is true that mild steel will rust immediately when expose to air. However this is a general statement There are grades of mild steel know as weathering steel that will rust to form a protective layer of corrosion slowing down the rusting process significantly. Stainless steel when used in areas where road salt is used can become pickled where a solution of road salt gets wash over the stl. steel then heated. This causes the Stainless steel to become brittle and loose it's corrosion resistance. The pickling process can also happen to Mild steel but in this case it makes the steel harder and somewhat more corrosion resistant.

permission to add this info the to FAQ?

i also still have to edit a few things that some probetalk members clarified, but it mostly had to do with the headers available and their specs.

[Custommx3]

Just let me know when , and I'll pop it in the FAQ.

[390ish]

I bought the second generation ssauto chrome headers with the flex pipe. Stainless. They are great, but set up for an mx-6, so get ready to cut some pipe and rework the egr bung tube. Think it had a negative effect on my low range power. However, the difference really comes into focus at approx. 4.1k rpms. Like my car acquires two additional cylinders. I have a 1.8 litre gs. Really like the headers. Also running an act clutch and an unorothodox racing aluminum/kevlar flywheel. Think the latter were a waste of money.