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I am a little late to this party
![]() I had Al Reed polish mine. Now it is that cool bronze color. Many VARA racers are using it now. ![]() ![]()
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Chad Plavan 911ST Race Car/2.5L SS Race Motor #02 1972 911T- Numbers matching- Restoring to stock 2011 Porsche Spyder Wht/Blk/Carbon Fiber Buckets/6-Speed (Sold) 2016 Elan NP01 Prototype racecar- Chassis #20, #02 |
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Crotchety Old Bastard
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I didn't think a cross-over was needed in any horizontally opposed or "boxer" engines.
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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 |
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I gotta ask
Chad P what ever happened with Frank Becks exhaust system? I heard that it was about to be the best out there for 2.0 cars. Shawn.
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'99 M96 2.5 Liter |
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Posts: 595
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Quote:
The later, use of identical heat exchangers merging into the Cat was because it's easier, cheaper, and lighter to use only one catalytic converter.
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'84 911, some sort of red color '05 Subaru WRX wagon |
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Franks is a very nice exhaust, however I do not feel it is worth the $2.5K. My cousin and uncle have it. There are other options out there without breaking the bank. Mark Scott and I race against other cars with Becks exhaust and they do not pull away from us at all. I guess if you have the cash go for it.
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Chad Plavan 911ST Race Car/2.5L SS Race Motor #02 1972 911T- Numbers matching- Restoring to stock 2011 Porsche Spyder Wht/Blk/Carbon Fiber Buckets/6-Speed (Sold) 2016 Elan NP01 Prototype racecar- Chassis #20, #02 |
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hmmm
I was not aware of the high price on that item. Thanks greatly for the info.
Best of Luck to you out there. I enjoy watching your track vids. Alot. Shawn. ![]()
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'99 M96 2.5 Liter Last edited by 901/05; 04-24-2008 at 01:35 AM.. Reason: more info |
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Check this link out :
http://uk.youtube.com/watch?v=8GaD1RKd_Tw&feature=channel Looks to be a sort of stinger, I just love the sound. If anyone knowns what it is and wher to get one let me know ;-) |
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Join Date: Aug 2004
Location: Mulholland Dr. SoCal
Posts: 591
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We just put our system on an early 2.2 POC racer for last months Cal Speedway event. Awesome sounds, and the driver reported improved lap times from changing out the 2 megs. These are completely smooth mandrel bent, and not made from u-bends, 16 ga. c/r U.S. steel, and nickle plated . These will be available in January, for less than $200.00. Pelican will also be distributing these .
Marty ![]()
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Porsche builds the 21st century 9146 so easy...even a Cayman can do it ! |
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Location: Sacramento
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I am no expert on exhaust but have some thoughts to put out there.
Scavenging and Back Pressure (BP) are the two major factors that effect how well our exhaust system works. Scavenging can add a “super charge” effect at a given point and increased efficiencies or performance above the norm. The benefit of Scavenging can be greater on a motor with high overlap cams. Back pressure will slow down the rate of exhaust flow. Slowing down the flow should hurt efficiency at higher rpm. However, at low rpm this might actually help on some motors as it helps keep the exhaust events timed at a more orderly rate for better efficiency. It sounds like the first use of a cross over it to allow the exhaust events to make room for each other like on an odd fire. Thus, allowing the exhaust to cross over to the other bank would reduce BP on the crowded side. Could it be that a cross over on an even fire might work to create turbulence at a lower rpm point and thus slow down the flow rate for better efficiency down low. Then still allow for lower back pressure at a higher rpm. |
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
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Kevin L '86 Carrera "Larry" |
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Location: Michigan
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I've been wanting to run my exhaust like this for years now. I could never find a system for my SC. I love how it looks. Are they generally an efficient system? Does anybody know?
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Join Date: Apr 2001
Location: Linn County, Oregon
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Harry, on your car, a stock exhaust has a "crossover"...the muffler! 911st here pretty much nailed my understanding of the benefits of a crossover pipe. Hot rod exhausts have been adding crossover pipes, or joing the two sides together with an X pipe for quite some time...
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
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Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,490
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Quote:
(edit) BEWARE of smog laws in your area...backdated exhaust is often frowned upon by bureaucrats.
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) Last edited by pwd72s; 01-05-2009 at 11:59 AM.. |
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Join Date: Oct 2004
Location: Naples, Florida
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Here we go. This was how all of this got started. It was all about Dr. Gas and Sterling Marlin. This article explains the basic concept.
Richard |
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I ROC!
Join Date: Feb 2004
Location: Long Island, NY
Posts: 390
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Why did the factory use megaphones on certain race cars w/o crossovers if there are large benefits to be had in additional torque & smooth AFR's? There are many but just for example, the 3.0 RS & RSR. Was this info found out after about 1974 when the factory didn't use motors with megaphones any more?
Also, the weber/phase 9 exhaust seems to be very highly regarded but it doesn't use any crossovers. Last edited by mpeastend; 01-05-2009 at 01:10 PM.. Reason: addnl info |
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Read the artical.
What stuck is it lowers back presure after the cross over (at least on an odd fire). |
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Quote:
The megaphones tailor the reflected sound waves to the rest of the characteristics of the exhaust to maximise low pressure at the open exhaust ports at peak hp.
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Bill Verburg '76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone) | Pelican Home |Rennlist Wheels |Rennlist Brakes | |
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Yes, you need to keep clear about the fact that a US 90* crank, 90* V, V8 is an odd fire engine
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Bill Verburg '76 Carrera 3.6RS(nee C3/hotrod), '95 993RS/CS(clone) | Pelican Home |Rennlist Wheels |Rennlist Brakes | |
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I was going to mention that it is still a matter of debate if a crossover works on a flat 6 or not, and if so under what conditions.
This dyno (stolen from dfink, posted here last week) was interesting: ![]() "Red is with the dynomax exhaust the blue is re-tuned with the straight pipes." I was surprised that the muffler (with gases mixing/ crossing over) beat the straight pipes, but then the old questions (conditions, correction) muddy the waters. It's still an interesting result... I hope to dyno my setup in the next couple months with and without a crossover- it will be on a wheels dyno, but at least we'll get another data point. |
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petepv: I think something is up with that info. He noted needing more fuel to correct the AF's with the change to straight pipes but that the muffler made more HP. More air flow plus more fuel with the straight pipes should equal more HP but that was not the case. Also his muffler is an unusual "cross flow" that has exhaust gasses flowing head on to each other as they cross in the muffler. Just not a clean data point I would suspect.
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