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Quote:
Originally Posted by JFairman View Post
"the 935 header design is potentially more of a street header and Brian's design is potentially a better race header"

Just curious, what makes you state this as if it is fact? did you race 935's or work on any?

Have you or anyone dyno tested any of these headers back to back without any heat soaked intercoolers ahead of the test runs?

. . . didn't think so.
Jim,

Wow.

My first note on my post was: "JMO"!

That means Just My Opinion. In no way did I intend it to be stated as a fact and it was in response to several other posts that stated the opposite which I took as opinions open for discussion.

Further, I did not make that as a unilateral statement or declaration. It was made with examples to other system's for reference.

If you disagree a counter opinion instead of a poke might be more civil and useful.

The best.

Old 07-08-2010, 05:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #81 (permalink)
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This is arguable the last and best racing exhaust Porsche built for its 993 GT2 EVO.

Equal length, secondary tubes, rotory colectors.



Here is Brian's:

Equal length, secondary tubes, rotory colectors



As I noted, except for the less than desirable integrated wast gates they seem to have a lot of the basics in common.



Here is the gorgeous reproduction 935 headers:

Un equal length primary's, short direct runs, flat collectors.




Here is a popular shorty system:

Un equal primary tubes, flat colectors, minimal volume, direct. .





Now, decide for your self, which is more like a race system and which is more like a street system.
Old 07-08-2010, 08:49 PM
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Good site for other exhaust system examples:

ENGINE
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Old 07-09-2010, 01:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #83 (permalink)
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Nice picts! Saw something new. On the Renault V6 twin turbo the throttle plates were at the inlets of the turbo compressors. Interesting.

All race motors had equal length headers.

Something else that stood out is how well designed the connections to the wast gates were. Looked like the best of the best collectors and set up to flow as cleanly as possible.

Same as on the 993TT EVO motor.
Old 07-09-2010, 02:16 PM
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What was also interesting, is the Zakspeed 1.5L produced 1000 BHP, 4.5 bar, 11,500 RPM, but used a cam mounted distributor like a typical 4 cyl engine.
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Old 07-09-2010, 02:25 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #85 (permalink)
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Did you guys see the twin turbo headers on Pat Williams GT1 car in the September edition of Excellence?

He bridges both headers into a single wastegate, so much for keeping the pulses separated.
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Old 07-10-2010, 08:13 AM
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The red rocket Bob Norwood built a few years back has the same single waste gate setup on a twin turbo platform. That doesn't mean it is the best system or the worst, it simply is a design that works withing the given constraints.
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Old 07-10-2010, 11:01 AM
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Quote:
Originally Posted by WinRice View Post
Did you guys see the twin turbo headers on Pat Williams GT1 car in the September edition of Excellence?

He bridges both headers into a single wastegate, so much for keeping the pulses separated.
Can you post a picture of that? I would love to see it! Thx.


I agree with Brian. One example dose not prove it is best.


I suspect if there is sufficient length in the primary and secondary tube, and the if the WG connection configuration is of design to inhibit reversion or cross over, a single WG might not kill potential. One might still get the increase in efficiency and VE that keeping the exhaust cycles from fighting with each other might deliver.

BMW seems to think there is a benefit as they have gone to split scroll turbos on there new 6 (changing from a twin turbo configuration) and twin turbo 8.

To be fair, I do not know how much improvement we are talking about. Is it more or less than the 2-3% improvement in TQ we get from twin plugs that allow less timing advance for less pumping losses? I do not know.

I suspect a design like Brian's equal length single turbo headers can be tweaked to get most of the benefit of a split twin turbo system with a less complexity, weight, expense. Even with a single WG if done right.

With the right modifications this might even apply to a shorty style to but it would not have the scavaging potential of the equal length system.

Not an expert, just what I suspect to date.

Last edited by 911st; 07-10-2010 at 04:52 PM..
Old 07-10-2010, 04:35 PM
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The picture bellow I believe came from the race motor Porsche / Andial supplied to slip into the 89 C4 chassis for hill climb win's.

Note the WG circuit. This might not be perfect but if one extended the two WG tubes off the secondary tubes a bit more it might make it a little less easy at speed for exhaust pressure to change direction and cross over.

Not sure, just open to the thought.

Probably an improvement over most single WG take offs. The ideal would be to keep the two sides separate with divorced WG's.



PS: Note the turbo dose not dran into a catch tank. It dose use a savaging pump. However, it returns the oil to the bottom of the case, not to the tank.

This should allow for the turbo's oil to be filtered before returning it to the oil tank which I do not believe is the case with a 930.
Old 07-10-2010, 04:51 PM
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Quote:
Originally Posted by RarlyL8 View Post
The red rocket Bob Norwood built a few years back has the same single waste gate setup on a twin turbo platform. That doesn't mean it is the best system or the worst, it simply is a design that works withing the given constraints.
Yep, I agree. I was just pointing out a different design that works. Some think you need separate exhaust pulses to each turbo, which may work well for the street, but doesn't look like it's necessary for a high output race engine that spends most of it's time in the upper RPM ranges.

I saw an F40 Ferrari track car with the same common wastegate setup.
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Old 07-10-2010, 09:10 PM
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I have a small fear about ballancing seperate WG's.
Old 07-13-2010, 08:17 AM
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Quote:
Originally Posted by 911st View Post
I have a small fear about ballancing seperate WG's.
Maybe Dr. Phil could help you out on that.
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Old 07-14-2010, 06:34 AM
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Quote:
Originally Posted by 911st View Post
I have a small fear about ballancing seperate WG's.
Been running dual w/g's for over a year now. No issues....
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Old 07-14-2010, 11:28 AM
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Quote:
Originally Posted by 911st View Post
I have a small fear about ballancing seperate WG's.
If you were relying on the wastegate springs as your only source of boost control, that may be an issue where you have to match the springs and test the wastegates so they release the same.

If you setup the the wastegates with 0.6 bar springs and a common solinoid with an EBC, it shouldn't be an issue.
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Old 07-14-2010, 12:33 PM
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