4 into 2 header arrangement?

[steve_pugh]

I'm looking for an alternate arrangement to the centre exit and stinger.
Would it be detrimental to flow if a merged header was to be modified so that it exited in two locations (I.e. the stock tailpipe exits ) instead of dead centre? 

I'm thinking that they could merge 4into2 rather than 4 into 1?

I'm not thinking that two separate headers would be the solution tho as you still need the length which is why I assume the merged header exits the rear of the engine and crossed over to the other side before merging into the centre. 

So perhaps the left j-tube from the front of engine and the right tube from the rear of the engine could merge and exit out the left stock valance hole and vice versa. 

If all the pipes are equal then should the power be affected overly? 

[spanners]

What happens after the collector don't matter, apart from the o/a system length, packaging will be hard to achieve just to obtain a "look".
a proper 421 system works well on race tracks were mid range is king, most single sweaters, inc, f3 et al, and most hypo saloons etc run 421 primary's, full on VW drag cars still have a power band and need 4-1 primary's for maximum extractor effect through the power band up to the top end, Unless you can run constant RPM with an auto box right at your maximum power RPM, that's how the big guns run just headers, they are always in the power band.
The pairing for a 421 VW system would be 1&3, 2&4, it would work well on a heavy street driven VW drag car, giving it good low and mid range power, anything else is just plain wrong, including the way the factory did the Kubels war time dual silencer system, it worked for good ground clearance only, not a power enhancer!

[Taylor]

I don't see where he wanted a 4 2 1 header.  Just 4 into 2

[spanners]

Neither can I,, I just spread the info, the real problem is the firing order we can't change with the 4 lobe opposed cam, 1342 would be easyer to package exhaust wise. Incidentally, 4 to 2 don't exist, no such thing, the nearest is a 4 to 1 with a bifurcated exit, the way Steve described it, to me is a paired system, works on big motors but needs pairing as I alluded to above.

[steve_pugh]

Yeah this guy clearly went one step further...


What I figured is pairing them as normal.  
So 1&3 2&4.  
Sort of like this but proper equal length:

Would this work?
(Without the stupid zoom tubes.    )
I know no such exhaust exists. I'm wondering whether it would work it'd one was made.  


How does it work with a Type 4 as they are pairs as 1&2 3&4..?

[spanners]

Steve, the top one is a disaster, it's paired wrong and not worth any comment other than a stock VW pea shooter exhaust would out perform it hugely,,, the 4 pipe megaphones are early inch pincher, another disaster, the lower one is T4 and becomes conventional 4to1 once a silencer is bolted on, they are not paired, (merged), if you must try a paired exhaust, do it 13 and 24 , it will be hard to package and will behind a fully merged system at some point in the rev range,  Ive looked at and used nearly all primary pipe variations for differing VW agendas for rally or Rallycross, and circuit racing, it's not easy, I've just done my high mount to allow clearance under the motor for a diffusor and it's still not good enough, needs another 2" raise, I must say a turbo or two makes the job almost easy, the turbo guys have it cushy.

[spanners]

this may give you some ideas, it's A 421 header system I made for a wee 1641, it shows the 13 / 42  pairing.

[Jonny Grigg]

Steve,

A 4 into 2 header system is a bad idea in your application. I am pretty sure that is the message in the replies here already....

If you want stock looks with two pipes coming out the stock locations, you should try something like this:

http://www.ahnendorp.com/Beetle-typ-1-engineparts-and-machining/Exhaust/Streetsport-Exhaust-VW-Beetle-Steel.html

Whilst it won't work like a true fully merged collector, it will be a whole heap better than a 4-2 idea your have proposed here. And you get mufflers, which are pretty essential to run the car on the street 

Cheers,

Jonny.

[steve_pugh]

Steve,

A 4 into 2 header system is a bad idea in your application. I am pretty sure that is the message in the replies here already....

If you want stock looks with two pipes coming out the stock locations, you should try something like this:

http://www.ahnendorp.com/Beetle-typ-1-engineparts-and-machining/Exhaust/Streetsport-Exhaust-VW-Beetle-Steel.html

Whilst it won't work like a true fully merged collector, it will be a whole heap better than a 4-2 idea your have proposed here. And you get mufflers, which are pretty essential to run the car on the street 

Cheers,

Jonny.

It's cool.  All the replies have taught me the reasons there is a 421 setup.   It's just me thinking out loud. 

I'm not fussed about a muffler on the street.  But I do like the stock look with large exits. 
That exhaust you posted looks like a stock style aftermarket header which is restrictive but have been looking at the A1 merged hideaway system.  They have one that curves back to stock exits. 
http://vwparts.aircooled.net/A-1-Sidewinder-Muffler-Beetle-with-Drum-Brakes-p/a1-sw-dual.htm

[JS]

I don´t know about the 4-2 arrangement specifically, but when we tried to change the firing order on a 4-1 header from 1-4-3-2 to 1-3-4-2 we lost 5hp across the 3-8000rpm range on the dyno.
So a complete firing order seems to help hp.