Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > 1- Porsche Technical Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rating: Thread Rating: 3 votes, 2.67 average.
Author
Thread Post New Thread    Reply
Registered User
 
copbait73's Avatar
 
Join Date: Nov 2003
Location: Chesterfield IN
Posts: 1,314
Garage
Discussions of HP as measured on a dyno or boost response/RPM as measure in the car during an accel leave out one important factor toward good drivability and time to speed road performance. That unfortunate truth is all turbocharged engines must first perform N.A. before they can deliver boosted performance.

Some increase compression ratio. Why? Obviously to make the motor stronger N.A. so it can better pull itself up to that magic time when the boost needle responds. However, ultimately this motor will make less power on a dyno than one of 7.5:1 C.R.

No one wants be “off boost” but it is a fact to be dealt with. Most component evaluations on turbocharged engines require on road performance comparison and subject driver input of drivability. These considerations can make your Porsche motor respond like the performance engine it is, or frankly a bunged up high torque diesel wantabe.

Throw away the boost indicator and give it a try.

Last edited by copbait73; 01-13-2010 at 06:13 PM..
Old 01-13-2010, 12:56 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #81 (permalink)
Registered User
 
Join Date: Feb 2006
Posts: 510
One thing I should have said, is that I think RarlyL8 new offering is a very nice effort in combining the advantages of an equal lentgh system (nice off boost response) and short total length (higher efficientcy on a tubocharged engine). It should be close to a "best of both worlds" system IMO.
Old 01-13-2010, 02:08 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #82 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
1100Sport,

I think we are mostly on the same page.

I have wondered if the Carrera and 930 headers are differed in size. Thanks for that info.

So the 3.2 Carrera headers are larger ID than the 930's? The SSI has about the same tube ID as the SC and turbo's?

On an SC the SSI's will make more HP than the stock headers. Not so on a 3.2 except briefly at about 3000rpm.

An exhaust change has been reputed to be the biggest reason for the HP jump from the 3.6 964 to 993 (250 v 272). That SC/3.2/3.3/3.6 C2 cross over is very suspect. (I think AFM to MAF is part of it though one 3.6 expert says not so much.)

The arguments for equal length (SSI) seems to be they are going to help pre-boost power.

Pre-boost is before 2000rpm.

The 3.2 N/A data I have seen dose not seem to support that the SSI improves normally aspirated operation before 2000rpm. Thus, how can we expect it to help on a turbo.

As you noted NA 3.2's do however respond well to increasing tube ID over that of SSI's 1.5".

This is supported by the SW HP numbers where SSI's made 10hp less at 3500 and 9hp less at 6000rpm than 1 5/8's-1 3/4's. Lets call it 10 hp.

Unfortunately larger tube size lowers boost response on a turbo.

Also, on a turbo, SSI's are only equal length on the primary tube so it is no longer a fully equal length system unless a split turbine is used.

With a turbo we are nearly doubling air flow through the intake side when running 1 bar. I do not know if we can interpolate from this that if a 1.5" on a 3.2 costs 10 hp that on a 3.3 930 it might cost around 20 hp?

I think it gets back to low overlap cams are not as effected by back pressure at low rpm nor benefit as much from savaging.

I do accept that going to a K27-7006 with its larger hot side and slightly smaller and older compressor than a 7200 is good for about 20hp mostly do to less back pressure.


We are all just guessing at what the differences or advantages might be at this point but that is how we learn.


I am thinking it mostly comes back to a couple of things.

True equal length are better at getting the gasses out any motor, NA or turbo/ and should result in lower back pressure and thus more HP.

A smaller volume header (including WG circut) will pressurize quicker for faster boost response.

It will be difficult to match the factory's quality and heat exchanger system.

Larger tube ID's will better support higher levels of HP.

Smaller tube ID's will reduce header volume and aid boost onset.

Past that, it comes down to getting a good execution of these basic's as to a system design and hard dyno data that is repeatable as to which is best for the intended use.


In principle I currently believe:

That a properly sized true equal length 930 system (Brian's, Prototec, Mode, Vision, Marco's...) will make for solid HP gains at most operating points on boost and possibly transition.

Smaller volume shorty headers should result in earlier boost onset. M&K or Vision if they still do so converted 993's are my favorite.

I do not care for the WG circuit on the B&B style headers as I suspect it leads to over-boost potential on some cars nor the collector however, there smaller volume and elimination of the funky stock crossover are potential improvements.

Stock or converted 993's will probably be best choices for heat.
Old 01-13-2010, 02:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #83 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Quote:
Originally Posted by 1100sport View Post
One thing I should have said, is that I think RarlyL8 new offering is a very nice effort in combining the advantages of an equal lentgh system (nice off boost response) and short total length (higher efficientcy on a tubocharged engine). It should be close to a "best of both worlds" system IMO.
I am sure the vote of support is appreciated by Brian.


As to equal length increasing efficiency and power on boost I totally agree.

In my opinion, saying that Brian's or any equal length system will contribute to off boost response is a stretch without testing or some other technical cause in support of such a position like reduced volume via greatly reducing the WG circuit lengths and or smaller tube id's.

I might hope, and it may very well be, that we see an improvement over a stock late 930 header in all such areas as it dose have its weaknesses (cross over & long J pipe).

However, it would not think it should be expected to make improvement pre-boost over a well designed lower volume non equal length system.

If better pre-boost operation were an expectation of equal length 930 headers, the others that came before would have been screaming so from the highest roof tops. After all B&B proved 930 owners will spend a fortune in search of less lag.

It just seems to me concluding such would be more a leap of faith than logical conclusion.

Please do not get me wrong. I think Brian's system is potentially the best new product to some along for a 930 in some time and may buy one some day as it is targeted right inline with my goals.

Old 01-13-2010, 03:04 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #84 (permalink)
Forced Induction Junkie
 
WERK I's Avatar
 
Join Date: Jan 2003
Location: Wisconsin
Posts: 3,291
Garage
Quote:
Originally Posted by 911st View Post
I am sure the vote of support is appreciated by Brian.


As to equal length increasing efficiency and power on boost I totally agree.

In my opinion, saying that Brian's or any equal length system will contribute to off boost response is a stretch without testing or some other technical cause in support of such a position like reduced volume via greatly reducing the WG circuit lengths and or smaller tube id's.

I might hope, and it may very well be, that we see an improvement over a stock late 930 header in all such areas as it dose have its weaknesses (cross over & long J pipe).

However, it would not think it should be expected to make improvement pre-boost over a well designed lower volume non equal length system.

If better pre-boost operation were an expectation of equal length 930 headers, the others that came before would have been screaming so from the highest roof tops. After all B&B proved 930 owners will spend a fortune in search of less lag.

It just seems to me concluding such would be more a leap of faith than logical conclusion.

Please do not get me wrong. I think Brian's system is potentially the best new product to some along for a 930 in some time and may buy one some day as it is targeted right inline with my goals.

I just don't understand how you can think this can be a leap of faith instead of a logical (actually it's been proven) conclusion. We're not colliding neutron's here, this stuff has been around and proven for over half a century.

Equal length primary's have been proven since.......the 60's, maybe even before that.

Furthermore, B&B headers are not considered a fortune, actually they're considered more of a modest-priced solution. If you want to scream about headers, check out a set of Bob Holcomb's equal length turbo headers.

Please don't use volume when talking about intake or exhaust tracts. It implies that the closer one gets to a zero diameter pipe, the more power can be extracted by the turbocharger. Exhaust primary size is calculated by number of cylinders, displacement, port size and target operating rpm range.

It's really quite simple so let's not over think this.

1.) An ideal header for a turbocharger will have the shortest primaries possible.
A turbocharger is driven by the velocity and energy of the exhaust gas.
2.) It will incorporate equal length primaries to aid scavenging (correct spelling) and insure exhaust pressure pulses do not overlap, which build up back pressure on overlapped cylinders and create uneven exhaust pulses fed to the turbine.
The length of the primaries before the joint is determined by calculating the desired rpm operating range and pipe diameter. The traveling pressure wave out one primary pipe will create negative pressure in the adjacent cylinder which will aid the scavenging of exhaust when that cylinder's exhaust port opens.
3.) And there's the quandary; Doing both without compromise, is impossible.

Study the turbo'd CART and F1 engines. The engineers of these engines squeezed every possible HP out of the engine and........they had equal length primaries.
__________________
Dave
'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 01-13-2010, 04:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #85 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,424
Garage
I do appreciate the support. Building shorty headers would've been much easier and cheaper.
The equal length portion of my design was spawned from my experience with the SSI based 930 system and the high-end systems such as Mode. In a nut shell these are the points I considered:

> The torque gained by an equal length system on an otherwise a stock engine is small when compared to the baseline of all systems. Headers only add ~15WHP to a stock engine so any increase by definition will be small.
> Short tube headers will give you that 15HP bump using the cheapest least complex design. Great from a business standpoint.
> Old racecars use shorty headers. They do not operate off boost and will never see a daily work commute. Getting the exhaust to the turbo fast is their function.
> Headers on a turbo engine are enablers. They allow other modifications to work optimally. The better the header design the more potential for optimal performance.
> Optimal performance (to me) does not mean the most horsepower but rather the most broad torque band.
> Street cars spend 90%+ of the time off boost and need as much torque below threshold as possible to enhance driveability and driving pleasure.
> Driveability improvement comes from a complex combination of the right components working perfectly together in a high state of tune. Headers are but one piece of this formula. Anything less than the perfect compromise in a header design will take away from the desired result.

That last point was/is my main focus. All headers make more power than the stock system. Equal length headers have the potential to give back even more in torque which translates to driveability and more usable power. How much more depends on the engine build and tune.
__________________
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 01-13-2010, 05:13 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #86 (permalink)
Registered User
 
Join Date: Mar 2000
Location: Auburn,In. U.S.A.
Posts: 2,449
I've owned the "Old Sled" for 22 years and have learned much about modding a 930 in that time. But the one thing that you need to know before you start is how you are going to use the car. I learned it the hard way.

I, like many others have, been all over the map with what is cool at the time, what the big race tuners use, what you hear here, and what you see in the pictures in the books. Then I thought, I'm never going to run Daytona, go 200 MPH, drive DE's, or run the Miracle Mile. So after 3 exhaust systems, 2 cam changes, 4 turbos, 2 clutches, and 3 ignitions I realized, I'm just an old fart that likes to get to the store and from lite to lite quickly.

I did 2 mods that completely transformed the car. The first was an 8:37 ring and pinion, shortened 2nd & 3rd gear. The second was the icing on the cake, the right headers. This car has incredible low end response and nearly zero lag. It is truly the most fun you can have with your cloths on.





Cole
__________________
Cole - 80 930 "The Old Sled"
Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.

Last edited by cole930; 01-14-2010 at 03:35 AM..
Old 01-13-2010, 05:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #87 (permalink)
Registered User
 
Join Date: Feb 2008
Location: Marietta GA
Posts: 2,542
I have nothing technical to add so I'll just post some pics of interesting Japanese exhaust systems.




These guys have some interesting looking stuff.
ボルケーノVolcano オフィシャルウェ サイト ポルシェ マフラ-カスタ ビルダー PORSCHE MUFFLER CUSTOM BUILDER
__________________
1987 GP White 930
1977 Ford Bronco
Old 01-13-2010, 06:08 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #88 (permalink)
Registered User
 
Join Date: Aug 2007
Location: Stockholm, Sweden
Posts: 170
Quote:
Originally Posted by 930gt-40r View Post
Gab- Where does one acquire these pieces? Im not in the market yet, but likely next year I will want to switch it up a little bit. White would look nasty on these, kinda like the old ferrari f1 cars...
Those "935" headers are from Reid Washbon Racing. Probably not cheap but truly a work of art.. they use 321 and inconel 625! on there turbo exhausts.

Reid Washbon Racing Exhaust Systems & Components

"Exhaust components fabricated from alloy 625 can be made with wall as light as .020 without sacrificing strength & durability even at elevated temperatures"

Mamma mia..
Old 01-13-2010, 06:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #89 (permalink)
Rocket Scientist
 
Join Date: Jun 2008
Location: Detroit
Posts: 881
Quote:
Originally Posted by RarlyL8 View Post
There is no need to use merge collectors with unequal headers like that, they don't need collectors at all. Step-up log design will work just as well and eliminate collectors altogether. If all you want to do is get the gas to the turbo just use a straight pipe and connect the cylinders to it.
Do not make a header by welding cylinder runners to a straight pipe. Lots of flow separation from at the edges of the junction. SAE paper 2000-01-0290 has a great sequence of Schlieren photos illustrating this. (Have you seen those pictures of model aircraft in supersonic wind tunnels? The ones that show the shock wave? That's a Schlieren image). After 120 years of internal combustion, that's the level of analysis exhaust pipes are subjected to, and this paper is 10 years old. You can imagine what goes on now, especially with variable valve timing thrown in. Smashing gnats with sledgehammers.
Old 01-13-2010, 06:33 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #90 (permalink)
Crotchety Old Bastard
 
RarlyL8's Avatar
 
Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,424
Garage
That was my point. This old 934 design is no more than a glorified log exhaust. Yes it works but damned near anything will work on a turbo engine as we see with the OEM 930 systems. Corky Bell talks a lot about this type of exhaust system in his turbo books.
__________________
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 01-13-2010, 06:49 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #91 (permalink)
Rocket Scientist
 
Join Date: Jun 2008
Location: Detroit
Posts: 881
Quote:
Originally Posted by kenikh View Post
The Japanese marques and tuners take a different approach to welding in a divider. The best approach is to weld spearate tubes to the two inlets on the divided flange. Thus, the divided section won't degrade. This is the approach I am using for my twin scroll turbo. Again, a true equal length header with divided inlet tracts will typically spool to full boost 500 to 600 RPM sooner than a non twin scroll or twin scroll without optimized exhaust system. Well worth the effort.
That'll work! If there was a way to weld three 30mm tubes to each side of a standard mini-foot flange, I wish they would show it, as that would be the ultimate. Your concept is darn close.

There's too much talk about scavenging on this thread. Forgetaboutit. Pulse conversion is where it is at for big boost. Man, BMW re-did their V8 for turbocharging last year. Changed the heads, cams, cam drive, and manifolds just to get short turbo manifolds on the INSIDE of the V. Unbelievable.

Old 01-13-2010, 07:03 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #92 (permalink)
 
Registered User
 
copbait73's Avatar
 
Join Date: Nov 2003
Location: Chesterfield IN
Posts: 1,314
Garage
Quote:
Originally Posted by Speedy Squirrel View Post
That'll work! If there was a way to weld three 30mm tubes to each side of a standard mini-foot flange, I wish they would show it, as that would be the ultimate. Your concept is darn close.

There's too much talk about scavenging on this thread. Forgetaboutit. Pulse conversion is where it is at for big boost. Man, BMW re-did their V8 for turbocharging last year. Changed the heads, cams, cam drive, and manifolds just to get short turbo manifolds on the INSIDE of the V. Unbelievable.

I tried to swear off this thread, but this is just too much. A production motor with cast manifolds.

I'm sure there are still some Ferrari engine engineers around from the early 1980s F1 days who will tell you how they started with that belief but finally moved the turbos from within the Vee to outboard (like everyone else) just to keep up in the rapidly escalating turbo HP race. Once that BMW engine gets to the power levels of F1, 15HP/cubic inch for a transient, road course duty cycle, I'll listen.

I had that belief at one time, it all sounds logical and pulse recover has its applications. Then I had a discussion with Ed Pink, look him up. He explained his experience with these manifolds on high performance motors and why he would not allow one retro-fitted to one of his turbo Cosworth Indy engines.

It goes like this: You blue print the combustion cycle components to make all cylinders operate under the same conditions, at all times. This doesn’t just mean the block related components but the air system also. When you’ve made every effort to achieve this you can reliably pull high HP. As it relates to exhaust, his comparative testing (yes he tested log manifolds that were the previous standard on turbo Indy motors) showed anything less than equal primary pipes (whatever length) gives you misfires on random cylinders at random RPM and misfires become more critical and damaging as power density increases.

I’ve witnessed and done many things demanded of a turbocharger and engine that took away from ideal power production. This is more the norm than the exception. Only BMW engineering know the numerous reasons they moved the turbos here but my prediction is like Mr. T said: “Pain”.

Last edited by copbait73; 01-14-2010 at 08:16 AM..
Old 01-14-2010, 07:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #93 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Quote:
Originally Posted by copbait73 View Post

...It goes like this: You blue print the combustion cycle components to make all cylinders operate under the same conditions, at all times. This doesn’t just mean the block related components but the air system also. When you’ve made every effort to achieve this you can reliably pull high HP. As it relates to exhaust, his comparative testing (yes he tested log manifolds that were the previous standard on turbo Indy motors) showed anything less than equal primary pipes (whatever length) gives you misfires on random cylinders at random RPM and misfires become more critical and damaging as power density increases. ...

This is gold! Especially on full race motors with high overlap cams.

This hints at it but no one has said anything about how equal length system helps to equalize temperatures at the exhaust ports.

-----

As to keeping each bank split into a split scroll turbo. One resource noted that this works very well on a 4 cylinder motor and is a significant advantage that warrants the effort. It was noted that on 6 it may not be of significant value.

For us I would guess it is a solid way to mitigate running unequal length secondary tubes with equal primaries.

-----

Glad to hear someone else say 'scavenging' dose not so much apply to turbo exhaust.

I suspect equal length is more about orderly exit of the exhaust pulses which reduces back pressure, increases VE, and thus power.

An extra 15hp, if that is the case, for equal lengths and more ballanced air flows / temps at each cylinder to me is worth the effort.

It might even me more if used in combination with the right turbo hot side. I suspect most 930 owners are suffocating the hot side in the name of less lag.

I suspect there could possibly be 40 +/- hp that could be freed up on a 425whp motor that is running a 7200 hot side based turbo with a change to equal length system and a larger turbine.

-----

Yes, equal length is the ideal turbo exhaust for making power!

But, lower volume is strongly correlated with reduced spool time. (See graph at start of this thread.)

I still have not seen a credible source that says equal length reduces spool time over a well designed non-equal system.

This is why I would say making the assumption that any such system will do so is a 'leap of faith' until proven with repeatable tests that control for boost level and AFR.

It could very well be I just could not find any experts that confirm this and am mistaken.

What I have read is that unequal length has the potential to create higher pressure spikes at the turbine that can have the effect of accelerating a turbo quicker.

------

Comparing a K27-7006 turbo to a K27-7200 might not be that different than comparing a well designed small volume header to a well designed equal length 930 system.

One should spool faster, the other should makes for more hp.

------

For the track the 7006 & equal length's are going to be a better fit.

For commuting, the 7200 and a decent low volume header is probably a better fit.

One might mix the two for a better average.

-----

Either turbo or header is probably an improvement over the stock units for the track or commuting.


Again, I am a big fan of what Brian is doing and it is what I would choose given my goals.


Last edited by 911st; 01-15-2010 at 06:16 AM..
Old 01-14-2010, 03:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #94 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Here is one of the better turbo exhaust articles from a I have seen that is from a turbosystems engineer at Garret.

Turbo Exhaust Theory

It dose say:

Quote:
getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging
I belive this is in support of reducing exhaust volume.

Latter he notes:

Quote:
As for primary lengths on turbo headers, it is advantageous to use equal-length primaries to time the arrival of the pulses at the turbine equally and to keep cylinder reversion balanced across all cylinders. This will improve boost response and the engine's VE. Equal-length is often difficult to achieve due to tight packaging, fabrication difficulty, and the desire to have runners of the shortest possible length.
This supports that equal length can help 'boost response'.

Unfortunately he is not very direct in discussing the trade offs between lowest volume and a balanced system.

There is a bunch of other neat stuff in the article to.
Old 01-14-2010, 03:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #95 (permalink)
3 restos WIP = psycho
 
kenikh's Avatar
 
Join Date: Feb 2005
Location: North of Exit 17
Posts: 7,728
Quote:
Originally Posted by 911st View Post

Yes, equal length is the ideal turbo exhaust for making power!

But, lower volume is strongly correlated with reduced spool time. (See graph at start of this thread.)

I still have not seen a credible source that says equal length reduces spool time over a well designed non-equal system.

This is why I would say making the assumption that any such system will do so is a 'leap of faith' until proven with repeatable tests that control for boost level and AFR.

It could very well be I just could not find any experts that confirm this and am mistaken.

What I have read is that unequal length has the potential to create higher pressure spikes at the turbine that can have the effect of accelerating a turbo quicker.
Admittedly, my understanding regarding the benefits of twin scroll turbos is strictly in the 4 cylinder department; what you said does make sense regarding the impact of pulses on engines with fewer cylinders. The more degrees between each pulse does, at least mathematically, mean that the pulse wave of a given "bang" is less likely to get clipped by the wave of the next "bang", as well as having fewer degrees of overlap of the tails of the waves.

Regardless, all of the Japanese pocket rockets use divided twin scroll turbo with equal length headers and the dyno runs on NASIOC and EVOm all tell the truth in these applications that a pulse tuned turbos spool and transient response are MUCH quicker than the same turbo running merged shorties. That said, the length from head to turbo in these cars is so much shorter than our cars, that the exhasut volume between the two is negligibile, so you get the best of all worlds.

If anyone outh there is running a divided twin scroll turbo in a 930, it would be telling to see the difference in spool between a divided, equal length exhaust and a merged, equal length exhaust on the same turbo (apples to apples). For me, the debate is academic, as my motor is still a long way from built and I am already all-in on the turbo and exhaust selection.

Maybe 9 months from now I will be the one doing the comparison, but until then, I'll hold out hope someone else will.
__________________

- 1965 911
- 1969 911S
- 1980 911SC Targa
- 1979 930

Last edited by kenikh; 01-14-2010 at 03:46 PM..
Old 01-14-2010, 03:44 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #96 (permalink)
Forced Induction Junkie
 
WERK I's Avatar
 
Join Date: Jan 2003
Location: Wisconsin
Posts: 3,291
Garage
Copbait 73 quoting the infamous Ed Pink;
It goes like this: You blue print the combustion cycle components to make all cylinders operate under the same conditions, at all times. This doesn’t just mean the block related components but the air system also. When you’ve made every effort to achieve this you can reliably pull high HP. As it relates to exhaust, his comparative testing (yes he tested log manifolds that were the previous standard on turbo Indy motors) showed anything less than equal primary pipes (whatever length) gives you misfires on random cylinders at random RPM and misfires become more critical and damaging as power density increases. ...

Keith:
"This is gold! Especially on full race motors with high overlap cams."

He was talking about the turbocharged Cosworth Indy Engine. High overlap cams are not a good solution for any turbocharged engine.

Garrett Engineer:
"getting the boost up early is a much more effective way to torque than playing with tuned primary lengths and scavenging"

Keith:
"I belive this is in support of reducing exhaust volume."

This is a complete leap. How can you jump to that conclusion? There are so-o-o-o many factors that cause a rise in boost early.

Sorry guys. I'm outta' here. This debate about the benefits of equal length headers has just really gotten out of control. It's been proven for decades, and this debate thing just goes on, and on and on, and on....

I have complete faith in Brian's new product. I believe it would be d@mn near perfect if it had a centrally located turbo flange, but our crammed 930 rear-ends make it difficult and costly (cosmetically and financially) to do otherwise. I can't wait to see Brian's dyno results so we can put this trampled debate to rest.
__________________
Dave
'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P

Last edited by WERK I; 01-14-2010 at 04:25 PM..
Old 01-14-2010, 04:17 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #97 (permalink)
Forced Induction Junkie
 
WERK I's Avatar
 
Join Date: Jan 2003
Location: Wisconsin
Posts: 3,291
Garage
An engine designed from the ground up to be turbocharged, the Chevy-Ilmor Indy V-8. Now I'm outta here.
__________________
Dave
'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 01-14-2010, 04:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #98 (permalink)
Wo ist die Rennstrecke?
 
DonE's Avatar
 
Join Date: Mar 2004
Location: Brooks, GA
Posts: 1,211
+1
Old 01-14-2010, 05:04 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #99 (permalink)
Registered User
 
Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I am a student, not an expert, and on a journey where I learn more about my favorite subject, Porsche's, in part by the hearing of others ideas.

Sometimes personalities get in the way including mine. If this has happened I am sorry.

I only seek the truth.

If you go back and look carefully for it you will see I am a big believer in equal length headers and Brian's new system.

The best.
Old 01-14-2010, 05:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #100 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 07:03 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.