The truth about headers.

[AMS Performance]

All Excellent points Mike. Also, The angle pitch of the merge collector itself also effects flow as well, a shallower merge is much more preferable to a steep short merge collector. Furthermore, You are correct with regards to our header not having this as an issue as it is a log style vs. merge collector. The main reason we chose shorty log tube style headers is TORQUE plain & simple. It is very difficult to get the level of low end torque (1500-3000rpm) that our design does vs. a long tube which concentrates more on top end. However, the inverse is true in that shorties do sacrifice some top end (which is fine). AMS concentrates on usable power in the low end - mid range for the street vs. top end HP for the track. Both produce power, its just a question of where the power is and what the customer's preference is for his or her specific application. Ultimately, the top end will always be limited by the torquey cams we have in our 55 AMGs so you will always get some power drop off close to redline, however this doesn't mean that you can't minimize it as much as possible through various means.

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[AMS Performance]

Originally Posted by Vadim @ FD

The problem with AMS, is that they are an exact copy of a stock manifold, down to the primary pipe and exhaust flange diameter. Except stock manifold is T409 and will last longer.

Vadim, Please do not make things up, this generalization is untrue. The only thing our design shares with the stock one is its general Log design, everything else has been changed.

Stock log manifolds:
- 1.4" primary diameter @ ports
- 1.6" Exit flange
- individual thin primary flanges
- 90 degree perpendicular merge with downtube (creates a lot of turbulence)

AMS Headers:
- 1.675" ID (1.75" OD) primary diameter @ ports
- 1.75" exit flange
- single piece thick head flange
- smooth curved merge with downtube, not 90 degree right angle.
- Port & polished primaries

Also, Stainless headers do not rust which cannot be said for coated mild steel shorties currently on the market (after all where do you think most of AMS header customers come from, they switched over to stainless due to rusted/cracked mild coated headers). (Not going to name any names in order to keep things polite & respectful)

Furthermore, nobody has seemed to mention an important fact. The stock exhaust ports on the 5.5L AMG (at least on the 5.5L NA engines) are between 37-38mm (~1.5"). The stock exhaust manifolds primary is 1.4" so that in itself is the largest restriction on our motors. The stock manifolds literally chock off the engines ability to breath because they are smaller than the exhaust ports themselves.

Also going to a 1.75" ID on an NA engine is too much and will hurt torque as well. The majority of the gains made from headers are from increasing the diameter of the primaries. A large portion of the gains are also from the removal or upgrading of either the primary or secondary cats. SO the end result is there isn't that drastic of a difference between short tube & long tube headers when you truly isolate down all the other variable factors. Its just a matter of where the power is. Shorties have better low end and mid range response for the street, long tubes have better top end response for the track but overall the meat under the curve is almost the same. At the end it really comes down to the customer's price & ease of installation preference.

Furthermore, the stock mid pipe entry on the NA 55s is only 1.8". So for those header designs expanding out to 2.0" on the downtube only to shrink back down to 1.8" (creating high levels of turbulence & poor scavenging effects) actually rob torque at lower rpms due to loss of necessary backpressure and poor flow qualities (which is why you never see dynos of them below 3500rpm, conveniently so). I would know since our very first prototype (of 4) was that specific design and it was immediately dropped once the serious torque loss was proven.

Having been through 4 different prototype designs in the 2 years of development, there is literally no way to make more power (without sacrifices) out of a short log tube design than our final design, you just cannot squeeze anymore power out of a shorty bolt-on design period. Long tubes you can obviously make more power but then things start to get complicated, expensive & labor intensive. Its all up to the customer to decide what's best for them at the end of the day.

I'm sure whatever you come up with Hooley it will be great! keep up the great work

[AMS Performance]

any update on the headers? Its definitely interesting to watch them unfold, keep up the great work.

[Russell Stevens]

Nice info! When I was playing with the Porsche 928's other members where going through the same debates and trying all sorts of designs. The design that ended up giving the best results was a set of headers with a X pipe installed after the headers. It's been a while since I read all the info on it but the dyno results where much better then all the straight header designs. Good luck with the project!

[jturkel]

Originally Posted by AMS Performance

any update on the headers? Its definitely interesting to watch them unfold, keep up the great work.

they look sick! i saw them in person and they are unreal looking. wow, is all i can say. perfect welds and overall workmanship