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I don't need to run cats to pass local yearly vehicle checks, but if i needed cats i would run the BBi. I like the expansion chamber straight out the turbine. I would suspect its way too small in relation to exhaust flow to really do anything but i like the exercise. But what i really like is the catalytic convertors moved down the exhaust stream.
From a pure flow perspective, if that first can is an expansion chamber and the second can is the cat, that is a good flow design for a cat in the system. A restriction in the flow path is always better for flow if it is located at the end of the path. A Flow Bench can not replicate actual exhaust flow due to the gas heat, pulses, etc. It is a great predictor of restriction. From a flow perspective, bolting a cat directly to a turbine is terrible. The flow energy is trying to move through and expand at the same time. Then it encounters the substrate.
This is a perfect example of thermal expansion on the HJS 100 cell Inconel cat. Blue metal at the hit, then it cools after it passes through the substrate and the pressure drops.
I would like to send you some of the very latest HJS German imported 200 cell tri-metallic catalytic converters to be flow bench tested. I used to know NASCAR cylinder head porters with flow benches- since you are set up I would be happy to send samples of the very latest HJS HD high flow cats with Emitec cores.
I can also share HJS flow bench exhaust gas data from Germany. Typically cylinder head flow bench testing is only a rule of thumb on automotive exhaust systems. HJS emissions has exhaust gas logging that measures heat and pressure across the substrate with the engine running at variuos loads. If you look closely on various OEM catalytic converters from time to time you see small threaded manommeter ports. These are for before and after pressure readings. Real time accurate sampling for determining catalytic converter efficiency would be to measure pressure Before & after the catalytic converter while the engine is operating and the exhaust is operating at normalized temperatures in a controlled environment. Before and after Dyno results also should show gains all things being standardized. Flow benching exhaust pipes or parts is not an accurate science.
A couple other datapoints. HJS Germany strongly advises against using 100 cell catalytic converters on Porsche, Ferrari, McLaren, Lamborghini and virtually other high performance street cars. How do I know and trust me I'm not making any of this up. This is what I have discovered in designing, engineering, dyno testing and observing and testing catalytic converters.
The 100 cell catalytic converters do not have enough surface area to sufficiently scrub the exhaust on OBD2 late model cars. In virtually all late model cars since 2005 you will get a P420/P430 code for catalyst efficiency below thresh-hold. A check engine light, CEL, as the catalytic converter in not functioning properly to clean the exhaust before measurement by the 2nd O2 sensor. . The only way to eliminate these CEL faults this is to install a "Software ECU tune" turn-off check engine lights or raise the thresholds for triggering P420/P430 faults.
Secondly, HJS German states that 200 cell catalytic converters are 300% stronger and more durable than 100 cell catalytic converrters. The 200 cell matrix is 3 times more durable than 100 cell as cell structure and matrix are much stronger and will not break down and unravel. I used to buy 100 cell catalytic converters in Quantity when the 996TT cars came out. There were 6 + cross drilled stiffenning rods welded through the 100 cell matrix to strengthen the metal core from falling apart. Often 100 cell cores have internal braces that GREATLY reduce exhaust flow. Look and check.I have archives on this.
Third, everyone talks about 100 cell being the best flowing versus 200 cell . Car guys and "bench racers" automatically think that 100 cell is the Holy Grail and that maximum power emissions legal and you are good to go. Its not that simple at all. You have to understand that there are alot more variables involved that impact flow, power output and ability to eliminate CEL lights. All catalytic converters come in various sizes. Catalytic converters have 4 essential design parameters of the matrix/ substrate: overall length, OD outside diameter, cell count, matrix material (ceramic or metallic), coating, and internal foil bypass design. Ive been to the trade shows and read and been shown the engineering data at the Frankfurt Autoshow. For all these criteria a catalytic converter must be directly sized to the engine's maximum power output to maximize both engine efficiency (power and mileage, and long term catalyst efficiency.
Fourth- internal foil design and bypass. Emitec has cross internal perforated foil designs to increase flow and increase catalytic action. HJS German has all these features on their very latest HD foil trimemallic catalytic converters. HJS German has data showing standardized flow of 100 cell, 200 cell and 300 cell catalytic converters. The 100 cells flow 96% of a straight pipe, 200 cells 93% of a straight pipe and 300 cell 88%. Given the 300% better durability and almost guaranteed no CEL Lights 200 cell HJS is the only want to go.
I have seen over the last 30 years all kinds and brands of catalytic converters. 100 cell, 200 cell, 300, cell catalytic converters placed on various cars from 180HP 911SC to 500HP GT3RS cars to 900- 1000 HP big block Camaros/ american muscle and GT2RS cars. I have seen and I have to say it.............Simpletons in both the American muscle car arena and high tech Porsche / Ferrari/ Mclaren tuners install 100 cell and 200 cell catalytic converters and tell customers that " you are good to go'. It was not done maliciously or to deceive but often its ignorance and simply not understanding engineering and math. You might be saying >>HOW? WHY? and give us an example?
I've seen many American tuners put a 4.0" long by 4.0" round 100 cell and or 200 cell catalytic converter on Dodge Hellcats 700HP and Mclaren 720 and GT3s Sometimes Ive seen even slightly bigger 4.25" by 4.25" bullet cats. These engines are choked and in many circumstances the cars are 100% going to make less power as the company or designer "assumes stock OEM has to be just terrible'. When asked I've pointed this out and said use the biggest substrate that will fit in the car or under the car and often I get the dumb look " gee its a 100 cell wadda you mean".
The solution is to use the largest outside diameter O.D. round catalytic converter that will fit the cars body cavity/ space. The size will be specific to each model for a Porsche, Ferrari, McLaren or Dodge Hellcat to a Bugatti Veyron. Its all a sliding scale. I hate to tell you that I have seen certain German tuners use small HJS catalytic converters on GT3RS cars that Fabspeed Motorsport only uses on regular 996/997 X pipes. The 500 HP cars deserve much larger catalytic converters with large surface areas to eliminate pressure drops. I've seen and had customers tell me that their HJS catalytic converters and other brands of catalytic converters are 100 cell and they got the Good Stuff ..............with a simple visual inspection they typically have 200 cell to 300 cpsi cats. Why does this occur its from 100 cell marketing, power/ hype and often cost. The BIG BIG catalytic converters cost alot more than small catalytic converters.
Fabspeed Motorsport USA was appointed HJS Germany's North American and South American . We directly import over $300,000+ of catalytic converters annually, From 4.25" round catalytic converters to massive 6" Round 200 cell cats that we use on 800HP Ferrari F12 Superfast cars and to the very latest GT2RS. FYI- the GT2RS really likes massive HJS German 200 cell cats with 76mm exhaust valves. Ill send pictures showing failed 100 cell cats and various stuff you guys should like. If you want catalytic converters for your builds , parts, endcones, exhaust valves or advice let us know.
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Thank you for this very informative and knowledgeable reply to this thread, Joe. With all that being said, if you live in a state without emissions testing and can tune out CEL's, are you using a catless exhaust or high flow HJS 200 cell cans?
FabSpeed, since I'm new to the community, I'll give you a quick background. I'm a Licensed Professional Engineer. Been modifying cars since the late 70's when we had to change Jets for fuel, Springs/weights for timing and pull spark plugs to read annealing marks on the ground strap and fuel rings on the ceramic (actually still do that to confirm widebands). Moved to Fuel Injection and turbochargers in 1999. Attached is a vid of my street toy that I built to run a street series of races.Basically have to run a 30 mile cruise, be 100% street legal and make 3 back to back to back passes at the 1/4 mile without touching the car on the out side. I totally stripped the car down to a metal shell and installed the engine, trans,suspension,brakes,electrical system, etc, etc . Went through 8 different turbochargers to get the necessary power. I've had three different ECM's in the car all laptop tuned by me. Even though it has some sophisticated ECM controlled systems like Traction Control, Wheelie Control, Boost Control it is much simpler to tune VE based as compared to the new OEM Torque Modeling / Airflow modeling ECM's that I will not touch :
So I get what your saying about the intricacies of Catalytic Converter Design based on substrate area vs cell count vs wash coating, etc. etc. It's also GREATLY influenced by the entry and exit size/configuration. From a "rough justice" point of view, I have never made more power installing something in a turbo exhaust system that flowed less air on a FlowBench. I use a digital manometer in "on the car" tests to gather pressure drop data to confirm the bench from time to time. You'll note from my previous posts that a FlowBench can not come close to replicating exhaust flow. It does a great job measuring flow....but exhaust pulses, heat, velocity, etc,etc is not replicated on a typical flow bench. Just the Thermodynamic expansion of energy released at the turbine exit is fascinating. Thanks for the post. More information for the community, always benefits the community.
3" or 63mm does it really matter because the exhaust cannisters are the real bottleneck. I had my 991 tt kline 2.5" muffler cannisters checked and the perforated pipes measured just 52 mm. I'm pretty sure that the small pipes limit the flow quite a bit.
3" or 63mm does it really matter because the exhaust cannisters are the real bottleneck. I had my 991 tt kline 2.5" muffler cannisters checked and the perforated pipes measured just 52 mm. I'm pretty sure that the small pipes limit the flow quite a bit.
I’ve never flow tested perforated pipe on my bench. You bring up a good question. Obviously, when the hot exhaust enters the perforated pipe it is not going to flow through it or be restricted by it like a solid pipe since it will be flowing in all directions. So a smaller size perforated pipe will flow equal to a 2.50” solid pipe. How much smaller , I don’t know. Interesting question.
Did another test tonight since the 76/63 Bypass pipe arrived today (Big Shout out to Sam and Felix with Kline. Outstanding customer service!) Did a pull through test in the direction of installed exhaust flow to keep it simple and consistent. 76/63 Bypass at 28" flowed 667cfm. 100cell HJS with a 4.6" diameter flowed 497cfm at 28".
The perforated tubes on my OEM system are OD 65mm but on my kline muffler they were just ID 52mm. That's roughly a 30% reduction! I was really dissapointed when I found that out. I can understand that bigger isn't always better but 30% smaller? Really? Low Flow instead of High Flow???
Check it yourself and do the math!
Please see the response below on behalf Joe Fabiani, Owner of Fabspeed.
Great to see and hear people posting and learning about Twin Turbo exhaust systems and sizing of exhaust components, sports car sound and power output!
Here are some other issues to think about. Porsche, Ferrari and most OEM manufacturers use small size tubing whenever possible to achieve there engineered power outputs that they planned long before the cars are released to the public. I have found over the last 30 years that Porsche , Ferrari and others use relatively small tubing to maximize flow velocity and scavenging effect on the engine. 993 Twin Turbos had 2.0" OD pipes going to the final exhaust tips. The 2011 GT2 RS had 60mm 2.375" OD pipework and the Ferrari 488 (700HP) had 60mm 2.375" tubing. At a recent car show I went under a 800HP Dodge Demon and saw (if memory serves me correctly) 2.5" or 2.75" tubing.
On the Turbocharged cars we are seeing the same relatively smaller size tubing since the engines get good sports car sound and achieve the power output that was set as a sales engineering goal. More specifically, Porsche Twin Turbo cars like the 996TT at Fabspeed Motorsport we have found that 2.5" 63.5mm tubing works great to maximize power and sports car sound with no drone. This car is harder to quiet since the Turbos are not VGT technology. I bought the 1st 997TT in the summer of 2006 and the VGT cars were very quiet.
In 2007 when I had my new 997TT (I miss my guards red 6 speed), we did a lot of Dyno development with 2.5" and then 3.0" tubing in multiple exhaust configurations. we had all the tooling and documented sound profiles and sympathetic drone and power gains. The cars worked fine with 2.5" 63.5mm tubing and we still offer multiple systems for these cars with these sizes and these work well with Tiptronic too and cabriolets.
The 3.0" 76mm system was too large under each and every single scenario we Dyno tested. We had the mandrel bending tooling and equipment in-house so we could have "biased the results or skewed the results to save money" but I, a GUNG-HO Porsche club member and racer, designed a systems with 2.75" 70mm tubing and resonators over 13 years ago. This was very expensive for Fabspeed Motorsport USA in terms of an additional $30,000 of mandrel bending tooling for an all-Electric Unison limited defense quality bender, and then dedicated resonators/mufflers with true 70mm 2.75" perforated cores to lost wax investment cast CAD designed 2.75" 70mm I.D. X pipes with a window.
Would be intresting to see you do a flow test of the GESI cat(300 cell) that Agency power sells and which they say outperforms the HJS HD 200 cell cat ....
01-16-2019, 05:58 PM
