Thoughts on this header design?
 

Don't need heat. Looking for a set of headers to spin up a 7006. I'm unfamiliar with the dual wastegate setup... what is the purpose of this?

Any thoughts on the overall design of these headers?

http://i.imgur.com/Ht24R4Eh.jpg

http://i.imgur.com/t7G4ypeh.jpg

http://i.imgur.com/616lRqSh.jpg

http://i.imgur.com/UnGRrDSh.jpg

Any info greatly appreciated.

These headers are will make some good upper power. My guess is they were for a larger HP EFI motor. The dual wastegates are to regulate boost creep on bigger turbos. The traditional design has some issues with boost overhoot. The dual setup helps eliminate that.

Looks like it has a burns collector. I am sure they would be fine but will not be the best for power under the curve. The runners are longer than I like for a traditional 7006. It isn't going to move the curve down. You may want to pass on these and look for something with a shorter primary if spool up is the overall objective.

Unequal length primaries......meh..... :)

^^^ always heard that... you want equal length primaries to get more bang from your bucks.

Yep, you don't want exhaust pulses colliding negating effectiveness.

The pulses can arrive at the secondaries at roughly the same time with unequal headers.

I see a bishoff 993 he in the background. That is what I will be running. Chris at tk speaks highly of them. Get Ben at M&K get a y pipe with twin wg's set up for you.

This is really a roll of the dice...properly designed exhausts have to provide good to excellent flow through out the entire rpm bandwidth, and that is not easy by any means. Is this a track car which will see high-rpms all the time, or a daily driver?


About 15 years ago, I read an article where something like 9 different aftermarket exhausts were tested on a 911, and although the writer wrote a few of them sounded fantastic, every one of them was inferior to the stock Porsche exhaust. In other words, in dyno testing, there were some flat-spots/loss of power etc.

Good luck!

Oh, I am ohso deffffffffffffinitely bolting my OEM muffler, cat, and heat exchangers back on then.

Phew, thanks for setting me straight!!!!!

Yes, I'm sure this was true for the NA cars, but certainly not for the 930s

962 header design
 

It's amazing the thing even ran with all those exhaust pulses running into each other...

http://forums.pelicanparts.com/uploa...1395335135.jpg

Link:

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/802014-962-factory-imsa-spec-engine-sale.html

You never know...might have to smog the car someday, or sell it.

Life is stranger than fiction.;)

BTDT on both accounts actually - soooooooo...

30 year old technology.....

This does seem to be conventional wisdom. I'm reading a lot more now (on actual technical forums) that a lot more attention seems to be focused on the merge itself. That the merge may have more impact on performance than the relative length of the tubes.

Exhaust pulse collision is reduced by the twin scroll exhaust plenum effectively halving the chances of exhaust pulse overlap (each side of the motor is now isolated). This should help mitigate the effect of the unequal primary tube length. To take advantage of this, a twin scroll turbo should be used. Shorter and straighter primaries and secondaries in unequal length headers also reduce the volume of gas that needs to pressurize (and the resultant thermal energy loss) which reduces turbo lag.

Equal length headers are great for NA motors but cause more of a packaging compromise for turbo motors. By definition all primary tubes are constrained to the length of the longest primary tube (cylinder furthest from the collector) which increases the contained exhaust volume and likelihood of boost lag.

The final thing to consider is that primary tube length is just one parameter. The velocity of the exhaust pulse is a function of the pressure drop along the primary and secondary tubes which is directly proportional to the resistance encountered. The curvature and diameter of the tube play a direct role in the backpressure/resistance encountered by the pulse. Equal length headers require more curves to equalize the length which can result in more resistance to flow.

Therefore header design is a compromise between primary length/straightness, exhaust pulse overlap, pressurized volume, and thermal energy loss. It would be overly simplistic to just zero in on one parameter (like primary length) and declare the value of the entire design. It would be like using the size of the valve covers as the sole measure of a motor's worth. Ultimately, it's up to the dyno to speak the truth.

To the OP: The dual wastegates are required to preserve separation between the left and right exhaust banks. Note the divider in the T4 header flange that keeps both sides separate. If there were only one wastegate for both banks, that would allow an exhaust pulse to cross over from one side to another increasing the likelihood of increased exhaust back pressure, and creating more turbo lag.

I am speaking of per bank. If you have one really long primary and one really short, there will be the possibility of the pulse energy arriving at the merge at roughly the same time. Then, you'd have wasted energy and backpressure.

I believe what people get confused about, is how log manifolds that are WAY unequal length spool way sooner than equal length headers. They miss the fact log manifolds are cast iron and VERY thick trapping a lot of heat which is energy hitting the turbine wheel more efficiently than a thin-wall header can do due to lots of heat loss.

Dividing scrolls reduces reversion as you stated, but that was not my first post was speaking of.

From my personal observation, every single dyno comparison going from unequal to equal length primaries/secondaries on both NA and turbo cars always picks up power.

Never seen one lose power. Not saying it's not possible, just never read about this happening.

Brian????????????

I don't wish to muddy the waters as header theory can take up a lot of bandwidth. So here's a picture.

321 stainless, equal medium length primaries and secondaries, merge collectors, twin waste gates, divided plenum. 1.63" pimaries with 2" secondaries to preserve velocity. T4 turbo flange for a big twin scroll turbo. O2 bung for each bank. This is NOT for a stock engine. Stock engine would use 1.5" primaries and a T3 flange.




http://forums.pelicanparts.com/uploa...1395376802.jpg

I read corkys bell book he states that Fat/thick isnt neccesarily better,
while back pressure is not good flow is and velocity better,

Are there any comparisons done on 2 types of headers of Exactly the same design etc on same engine
but the only difference is the diameter of the tubing used ?

Because there's so many opinions, which is what they are.

Some fact sheets if they have been done?
Im in the belief that the pipe should be the same size diameter as the actual outlet just makes sense to me,
otherwise its just wasted space isnt it? Or is there more to it, i mean its like blowing through a drinking straw , its thin and speed is maintained but if it trumpets out and gets wider then the air goes thinner and it slows and spreads out.

I've tried different ID primaries/secondaries on the same engine as well as short tube vs long tube, just about every type on the market, and this is where it settled out.
Yes the primary ID follows port size on a street engine. Going larger adds lag but also may facilitate a bigger top end if the cams and turbo are sized for it. There are a LOT of variables in an engine build and the headers must be designed to accommodate the package.

Addressing the original post, those headers look to best work on a modified engine with ported heads. Tubing lengths are short so something else in the build will be needed to raise the mid-range torque if that is desired.