Exhaust header design question

[bnam]

I thought the AlpinA was paired differently -- cylinders 4&1 and 2&3 together. While this one is 4&2 and 1&3.

B

[TobyB]

I would be surprised if this thing actually performs well...

That said, it won't SUCK, it just won't ROCK!

hee

t

[roadhog0]

Schrick did it 1.3 and 2.4

http://www.alpinabmw2002.com/2010/03/schrick-bmw-m10-headers.html

Alpina looks like 1.4 and 2.3 if this is an Alpina

http://www.e30tech.com/forum/showthread.php?t=110367

Super Spring does the same as Alpina

http://www.bmw2002faq.com/component/option,com_forum/Itemid,0/page,viewtopic/t,299428/view,next/sid,83338926aa3fa5222b04f04bcb758421/

[flyingjolly]

Pme is the mean pressure during combustion

here's what i wrote in my blog:

There are always discussions about what header is best for a "sporty" engine. Most people propagate header © as the ultimate one for horsepower, while according to the diagram from "Rennwagentechnik" by Michael Trzesnioswki, the standard header (a) of the M10 engine is the perfect header for it.

As the M10 has the standard firing order for a 4cylinder engine with 1-3-4-2, the exhausts of 1 and 4 as well as 2 and 3 have to be paired together for best performance. Trzesniowski says: "With the usual firing order for a 4yclinder engine with an even crankshaft, the shockwave of the prior firing cylinder is reflected as a negative pressurewave, which improves gasflow."

Whereas racing headers like © need to have the same tubelenghts before the are joined up in one tube.

While a header like ( or © still might be the best for very high revving racing engines concerning gas flow, (a) is the best overall header for street use, as it allows the highest pme curve over rpm.

http://touringmm.blogspot.com/2012/02/die-ewige-krummerfrage.html

[bnam]

Joe,

Thanks for the info. One question -- both (a) and ( have the same pairing and are 4-2-1, with the only difference being that ( has equal length headers while (a) does not -- soI was surprised to see that (a) has a better curve than (. Is it because it has the more direct path for the gases, while ( is more curved?

Byas

[flyingjolly]

that was my first guess too, it's just a good guess, i don't know it for sure.

You have to bear in mind, that Pme is not horsepower, it's the mean pressure during combustion, more like torque - this can mean however, that you have greater horsepower with ( but less torque. My opinion in this case was, that for a street car that might even be used as a daily driver it's better to have more torque over the rev-range than peak horsepower. This doesn't mean other headers are bad, just too "racey" than really needed. Like 102 Octane fuel - great for a racecar but not neccessary for a roadcar.

My opinion though

[bnam]

No, ( will not create more HP. At every RPM PME is higher on (a). Since Torque is proportional to PME, this would mean that (a) has higher torque at every comparable RPM than (

HP = 2*pi*RPM*Torque/4500 (metric) --> so if at every RPM torque is higher in (a), so will HP.

That's why it's puzzling to see that (a) flows better or equal to ( at every point in the RPM.

Byas

that was my first guess too, it's just a good guess, i don't know it for sure.

You have to bear in mind, that Pme is not horsepower, it's the mean pressure during combustion, more like torque - this can mean however, that you have greater horsepower with ( but less torque. My opinion in this case was, that for a street car that might even be used as a daily driver it's better to have more torque over the rev-range than peak horsepower. This doesn't mean other headers are bad, just too "racey" than really needed. Like 102 Octane fuel - great for a racecar but not neccessary for a roadcar.

My opinion though

[flyingjolly]

it suprised me too so i made myself a reasonable explanation for it up, but you're right with what you said.

Either this diagram is wrong (don't think that), or there's another reason for racing engines to have the b or c headers

[TobyB]

You'd be hard pressed to find a race engine out there with anything

other than the 'd' option...

t