Ketchmi

We certainly hope so. Not too many people can do a group buy for just themselves though like someone we know.

BC

I bought a Dr. Gas X-over 2 years ago that seems to be able to be sized to fit the MSDS spacing on the 2V engines. They actually spaced it to my specs as I recall. EXPENSIVE. At least I'll get to use it again on the 78.

Mongo

I wonder if anyone has a used/bad catalytic converter and downpipe for a 928 S4 they wish to get rid of for my own creation that I've designed

rob rossitto

devek's L2 stuff will work w/their xpipe/cat stuff... that's one reason I picked them... couldn't find a bolt on for the msds stuff...

sportscarclassics

I hope this information is useful.

I would like to elaborate on Tom's comments regarding flow characteristic of the exhaust gases. I am an aerospace systems engineer specialized in heating and AC for aircraft and military vehicles, (tanks, missiles…). Energy can not be created nor destroyed but transferred from one state to another. So when the exhaust gases flowing down the pipes it is losing energy by heating the pipes and the longer the pipes the cooler the gas gets. If the pipes are straight them the gas flow is considered laminar flow however the closer you get to the walls of the pipe the slower the velocity. The walls of the pipe have a coefficient friction and the gases rubbing against the wall will stop on a micro level. The next layer of gas will now rub against the stagnant gas and slow it down too. This delta in pressure from the high flow in the center and the slow on the outside causes the transition (middle) layer to go turbulent (spinning around in circles). On one side of the layer it is fast and on the other side it is slow, two energy levels and the gas spins and wastes energy, while causing some heat loss to the center layer. The fast layer gives up energy because the middle layer is braking it.

Now when you hit a corner that say goes to the right, the gases on the left side up against the pipe rubs the pipe real hard and looses energy by heating the pipe because it now has to turn. The gas flows down to mostly zero but a lot thicker and it affect the next layer causing waves of energy. We are no longer flowing smoothly because the middle layer is now colliding into the wall, causing turbulence where most of the gas is going backwards but the fast inner layer is also turbulent because it is being bumped in all directions however the gas keeps pushing and the turbulence spins down stream to recover from the corner. We all know that we have to have smooth bends and transitions. When the gas flows from a 2” to a 3” the outer layer suddenly encounters a vacuum on one side and it will pull it to the 3” dia walls. However it is not flowing straight down the pipe anymore but straight into the 3” wall. It bounces to the low pressure side and cause a spin or Eddie like a rock in a stream. A large portion of the flow at the transition is not flowing and just spinning around to interfere with the fast inner flow. If you put a pressure sensor at the header and another at the tail pipe you will measure a dealt pressure and the more bends or transitions the higher the dealt pressure or pressure drop. This pressure loss is energy given up in heat to the pipes and that is why turbos like hot air because it has more energy…Enthalpy.

In the corners the gases pile up to increase pressure, reduce flow to a point then the gases collapse to cause a pulse and the next wave of gases pushes through. These pulses are high pressure, low pressure, high, low in a cycle and the frequency depends on the geometry of the pipes, (layout) and RPM. If you have pulses it messes with the harmonics of the scaveging or the ability of the engine to blow out the gases. Every time you have a pulse, the gases will backup momentarily and then flow again…not good.

I hope this help.

Ketchmi

Now Heinrich, play nice with the other kids! (discount applied!)

heinrich

Dave hey, if someone doesn't like the colour of my money, what can I do?

928ntslow

cpires...that is quite interesting and leads me to believe that I am leaving some power on the table of my 82. I have MSDS headers that affix to a custom made "Y" pipe. The collectors of the headers are 3" and then the 2 inlets of the "Y" are 3" and then bend to meet a 2.5" outlet that connect to my Borla 2.5" system. Based on what you say and the configuration of my "Y" pipe, the gases are meeting at more than a 45 degree angle and then are supposed to exit through a lesser diameter pipe. Seems to me that I need to replace the "Y" with something more like a "V" being 2.5" diameter overall on the merger.

Hmmmm...very interesting.

blau928

Sounds like someone has just explained laminar flow, boundry layer effects, and heat as related to gas velocity in an exhaust..

Thank you....

Tom Cloutier

Heinrich,
What the hell are you talking about? Never, I repeat NEVER, did I claim DR had stolen anything from me. At least make sure your story has some basis in fact before you post this kind of fictitious crap on a public forum.

Just in case you, Heinrich, are still confused: The X-pipe I make is a direct copy of Louie's X with some modifications to allow simple incorporation of cats. My decision to make the X was arrived at in a phone discussion last Fall with Louie and has his full support. We've discussed the mods I have added and they meet his approval. He has seen my latest version of his X and was much impressed.

The X-crossover is certainly not my idea, nor was it Louie's. He designed, tested, developed, and implemented that idea on the 928. He and I discussed the various designs from the very beginning and I helped by doing some CFD analysis for him.

Enough said about where the X idea came from. I doubt that anyone knows who first thought of it.

As for your request for a dyno, that's a moot point now since you will be buying from Dave. As I stated in a previous post, my X is so nearly identical to Louie's that I don't feel any further testing is necessary. If I start modifying the throat diameter or other critical aspects of the design, then of course dyno testing will be essential.

Please, if anyone wants to purchase an X from me, contact me off line at tomasc@thePowerBroker.net or 510-849-9778. I don't feel right about doing business on the Rennlist (other than what has been referred to as "pimping on line").

Tom Cloutier

hinchcliffe

Heinrich? What have you done..................

jorj7

Heinrich,

Tom might not have answered you because he doesn't currently have any dyno
comparison between an original Ott-X and his version. It's probably a good thing
to do, but it also take time and resources. I know when we did my install and dyno,
it took 5 hours to get the baseline, install the X-pipe, do another set of dyno runs, install
the Random Tech Cats, and do another dyno run. That's a lot of work, and I appreciate
that he was willing to do this for me. It was of benefit to both of us, though it didn't answer
all the questions regarding hp gains. I don't know if Tom wants to go through it again,
especially since it takes time away from his production and other research projects.
This is just my option, since I haven't talked to Tom to confirm this, but I'd be inclined to
give him the benefit of the doubt.

Tom Cloutier

Hi Cpires,
Sorry, I don't know your first name, but I'm glad to make your acquaintance. It's great to find another guy who loves fluid dynamics and knows something about it too! I hope you are open to questions and discussions.

Do you know of any really good engine intake and exhaust flow analysis and simulation software? I have Engine Analyzed Pro, but it is really pretty crude and inadequate as a design tool. I'd like to see a program that was flexible enough to graphically display the flow along with sonic and pressure waves, their reflections and interactions to maybe the third harmonic for engines from 1 cyl to maybe 12. One would want to be able to vary the pipe configuration, rpm, animate, and do slow motion as well. I don't know of any such tool. It might be a fun 5-year project to write one! If only I was 25 again!

I look forward to talking more with you.

Tom Cloutier

heinrich

OK. I didn't know what to think since I had asked repeatedly over time with no response, and Tom I'm sorry. I'll erase that post. I am still interested in a dyno, and I'm still wanting to buy an X, or a couple of them.

heinrich

Erased.