Exotic-metal55

I have seen a lot of claims on "true firing order headers" on several forums recently .. Mostly euro forums for some reason.. This term is not used anymore on modern American muscle forums, as it referred to 180 deg headers.. Have you ever seen 180 deg headers? They are giant array of bird`s nest pipes that are actually firing order headers.. See pic below.

Here is a link to our firing order and cylinder number order..http://autorepair.about.com/library/...bl-fo-0409.htm

The goal of true firing order headers, means it must follow the firing pattern and locate primary tubes next to each firing cylinder (in order).. This can help scavenging in some collector designs (not all).. As you can see below ,, adds a huge amount of pipes that cross from side to side of the motor to follow the firing order..

As you can see from the benz firing order, this is not possible to have with two seperate sets of headers.. Besides, modern merge collectors , tube lenght and other factors are way more important than having a giant birds nest under the car or buying into the gimmick of individual headers being in firing order,to help with scavenging..

lowprofile

Once you bolt on an exhaust system does it even matter? Old school, there were all sorts of designs including tri-y, equal length, stepped, inversion cone and so forth. The consensus was that once you add even a small amount of back pressure, the scavenging effects were greatly reduced if not completely null.

Exotic-metal55

Exactly, firing order design is defined by the snakes nest pictures.. None of us want or can drive daily with all that.. So, anything else is just a Gimmick IMO.. No way to get firing order gatlin gun style results, with out crossing pipes from bank to bank.. Nasty!

bassn_07

Are there any benefits to having each bank fire in order?

c32AMG-DTM

IIRC, it would cause the engine to be unbalanced. You need a firing order that follows a logical pattern for remaining consistently balanced over each revolution.

c32AMG-DTM

To the OP: I've only heard one header manufacturer tout this characteristic... and they're products appear to be very well engineered and constructed. Not stirring the pot, but I'm interested to hear their take on your opinion.

Exotic-metal55

Just to keep this thread on tract. This is not about saying anyones headers are not designed well. I have seen this firing order add on import and other euro forums recently. Has nothing to do with wether the header is not a performer or not.. This is about defining what true firing order headers are ..


Supercharged headers do not need as much attention to scavenging detail as N/A headers. We need free flow and most headers on this forum have that and their results back it up.. Those gains come from primary, collector design and what mid pipe design you go with.. Those gains stand on thier own and not from firing order siamese connections..

hooleyboy

I have spent countless hours in working on this topic. I have so much scrapped 304 stainless pipe sitting around from revisions of my E55/CLS55 headers. SO this is my take on it.

1). The birds nest style header wont work on our cars. 1 due to room and 2 due to o2 sensors. The o2 sensors will never know what bank (If any) are lean or rich. Thats if the o2 bung is mounted in the merge collector. It would mess the the ECU's ability to add or pull fuel correctly. That because you have bank 1's o2 sensor monitoring bank 2's runner.

2) I have found that the use of a merge collector pyramid (as seen in pic below) to yield better results on the dyno, than independently ran merge collectors that fire in a circular or Gatling gun pattern. Like this pic



Merge collector pyramid pic (taken from goolge)



After moving some pipe around to clear the steering shaft and pull one runner away from the firewall it wold have made it very difficult to make both sides have that "firing order" merge collector.

This is where we got thrown a curve ball. After only changing one sides of the headers to run out of firing order. We thought that might yield something we could see by monitoring the fuel trims on each bank (long term and short term).

My guess was that bank 1 (drivers side) being out of sync and bank 2's still maintaining the firing order in the collector. I would see the fuel trims change slightly. Due to What I thought would be difference in velocity. From only messing with the design of the firing order on only the drivers side. That did not happen. So.... It never resulted in the one bank seeing more flow than another.

To me it lead me to believe that it now just does not matter what the firing order is. However it left me with another question. What if the headers were made out of mild steel and uncoated? Could that change my findings.

The only reason I think of this is due to Stainless Steel being a poor conductor of heat (so it keeps the heat inside the header) Where are Mild Steel will spill the heat out of the header and actually slow down the exhaust. Not to mention heat soak every thing around it, if its uncoated.

I never really got around to monitoring EGT's... But, I wondered if a true firing order on separate merge collectors (when Mild Steel is used) would yield different results. Maybe by helping keep velocity up.

Our C55 header maintains the "Firing order" design, but is now fitted with the merge collector pyramid. Its kinda like "If it isnt broke than dont fix it" sort of things.

The E55/CLS55 header is total different beast. One side is not following the firing order and the other side is. After we switched a runner around to clear the steering shaft and added the collector pyramid we got about 4whp more. Not only that, the power from run to run on the dyno was also very consistent. This was tested on Dyno-Comp's 578whp E55. This consistency also passed on to my brothers CLS55.

Any event its a very interesting topic and something I've been working on for a few months now.