LOST JEEPS :: View topic - Magnaflow Installed 2 1/2" Cat back now

The catalyst will tend to get particle build-up in the cells during 100's of miles light load driving...not trailer towing. Over time this will add restriction in the exhaust system. These types of cats also accumulate sulfur. A few wide open throttle accels will help keep the cat clean, but the best way to fully clean an oxidation catalyst is sustained high load, high rpm driving. This would entail pulling a trailer up a grade for about 10 minutes. This situation will keep the exhaust temps above 550-600 C for some time to help purge any sulfur and anything else for that matter. With the relatively new 15 ppm sulfur fuel it will take many 1000's of miles for much sulfur accumulation on the cat.

A clean catalyst should only have 80-100 mbar of backpressure at WOT and 20-40 mbar in normal driving. This is hardly measureable when compared to the muffler and other piping restictions (bends, bottlenecks, flex coupling, etc.) The KJ exhaust system backpressure is about 400 mbar as measured six inches downstream of the turbo at WOT.

The environmental benefits of the cat far outweigh the potential performance gains. The catalyst cleaning routine is also a good excuse to get throttle happy!!

Author:	warp2diesel [ Tue Aug 11, 2009 8:51 pm ]
Post subject:	Magnaflow Installed 2 1/2" Cat back now
After I got some other work done today, I got out my Magnaflow and did the installation. Some tools and supplies rounded up. The first thing I noticed after unbolting the Stock Muffler was the 2 3/16" choke down restriction on the Cat flange. First thing was to cut off the Cat Flange. Then I cut a short piece of stainless steel 2 1/2" 303 pipe and got it into position to weld. I used the Stock Muffler to hold the flange in place to tack weld in place. The other restriction is at the rear of the Stock Muffler. I cut the pipe just beyond the restriction. Muffler flange welded to Magnaflow. Burrs removed Pipe was tack welded to 2 1/2" SS Pipe and welded tight. I used a small floor jack to position the pipe on the Magnaflow and Tail Pipe. Installed on CRD. I had one leak on top of the Cat flange where I missed welding a 1/2" section. I got out the mirror and blind welded the 1/2" section I missed. Where the Cat flange mated up to the short section of pipe I had to weld on the inside and clean out the excess weld with a die grinder. I noticed the boost gauge climbed higher and faster going around the block. Tomorrow I will check back pressure readings between the Turbo and System, Cat was not gutted.

Author:	Joe Romas [ Wed Aug 12, 2009 7:52 am ]
Post subject:
If you/we were able to find both parts of the flange that would make the job a lot simplier I think I'll explore that approach. Are both flange pieces the same or is it a male/female type thing? Get after the rust on that Type Two

Author:	linewarbr [ Wed Aug 12, 2009 11:04 am ]
Post subject:
Good write-up. I recently ordered a full Magnaflow Catback (got it from Wide Open Speed's Ebay store for $350) and put it on. There is a noticeable difference - the engine feels like it breathes easier, and the power delivery is more linear. The flanges are male/ female. The muffler has the bolt-ends built into the flange, which go through holes on the cat-side flange and are then tightened by nuts. Ya, I noticed the rust, too, but didn't say anything as I don't live in the rust belt. Is that what I have to look forward to if I move to the frozen north?

Author:	warp2diesel [ Wed Aug 12, 2009 5:52 pm ]
Post subject:	Back Pressure readings and more.
linewarbr wrote: Good write-up. I recently ordered a full Magnaflow Catback (got it from Wide Open Speed's Ebay store for $350) and put it on. There is a noticeable difference - the engine feels like it breathes easier, and the power delivery is more linear. The flanges are male/ female. The muffler has the bolt-ends built into the flange, which go through holes on the cat-side flange and are then tightened by nuts. Ya, I noticed the rust, too, but didn't say anything as I don't live in the rust belt. Is that what I have to look forward to if I move to the frozen north? The Type II VW with a Turbocharged Intercooled 1.6L Diesel I retrofitted is a 1971. The flange on the back of the Cat is necked down to 2 3/16" ID and needs to be opened up to 2 1/2". Lots of ways to do it right, I picked an option that worked with what I had on hand. On the level full acceleration with no trailer the gauge piped in between the Turbo and the Cat stays at 0 PSI. When I climbed a 5% grade entrance ramp I got the back pressure to climb to 1 PSI. With the stock muffler it would have climbed to 4.5 PSI under the same load going up the 5% grade. The boost gauge jumps up to 15 PSI to 18 PSI on flat land acceleration.

Author:	warp2diesel [ Thu Aug 13, 2009 7:18 pm ]
Post subject:	Update Magnaflow Installed 2 1/2" Cat back now
I must have blown out all the soot sitting in the Cat. I no longer get any back pressure reading on the gauge between the turbo and the Cat even when I accelerate up a 5% grade at 4,000 RPM with the EGT at a hair over 1200f. I suspect that around town driving coats the plates in the Cat and reduces the flow through it creating back pressure. By installing a 2 1/5" Cat back exhaust system upgrade the heat in the exhaust brought the Cat up to temp, burned up, and cleaned off the soot and other hydrocarbon solids. Thanks to this exhaust system upgrade the engine runs more like the way it was designed by VM I will leave the system back pressure gauge hooked up until I can do some trailer towing and see how it performs under a greater load.

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Author:	GreenDieselEngineering [ Thu Aug 13, 2009 11:50 pm ]
Post subject:	catalyst purge
The catalyst will tend to get particle build-up in the cells during 100's of miles light load driving...not trailer towing. Over time this will add restriction in the exhaust system. These types of cats also accumulate sulfur. A few wide open throttle accels will help keep the cat clean, but the best way to fully clean an oxidation catalyst is sustained high load, high rpm driving. This would entail pulling a trailer up a grade for about 10 minutes. This situation will keep the exhaust temps above 550-600 C for some time to help purge any sulfur and anything else for that matter. With the relatively new 15 ppm sulfur fuel it will take many 1000's of miles for much sulfur accumulation on the cat. A clean catalyst should only have 80-100 mbar of backpressure at WOT and 20-40 mbar in normal driving. This is hardly measureable when compared to the muffler and other piping restictions (bends, bottlenecks, flex coupling, etc.) The KJ exhaust system backpressure is about 400 mbar as measured six inches downstream of the turbo at WOT. The environmental benefits of the cat far outweigh the potential performance gains. The catalyst cleaning routine is also a good excuse to get throttle happy!!

Author:	warp2diesel [ Fri Aug 14, 2009 9:11 am ]
Post subject:	Re: catalyst purge
GreenDieselEngineering wrote: The catalyst will tend to get particle build-up in the cells during 100's of miles light load driving...not trailer towing. Over time this will add restriction in the exhaust system. These types of cats also accumulate sulfur. A few wide open throttle accels will help keep the cat clean, but the best way to fully clean an oxidation catalyst is sustained high load, high rpm driving. This would entail pulling a trailer up a grade for about 10 minutes. This situation will keep the exhaust temps above 550-600 C for some time to help purge any sulfur and anything else for that matter. With the relatively new 15 ppm sulfur fuel it will take many 1000's of miles for much sulfur accumulation on the cat. A clean catalyst should only have 80-100 mbar of backpressure at WOT and 20-40 mbar in normal driving. This is hardly measureable when compared to the muffler and other piping restictions (bends, bottlenecks, flex coupling, etc.) The KJ exhaust system backpressure is about 400 mbar as measured six inches downstream of the turbo at WOT. The environmental benefits of the cat far outweigh the potential performance gains. The catalyst cleaning routine is also a good excuse to get throttle happy!! GDE's backpressure data is consistent with my readings, therefore I must agree. One of the biggest restrictions in the Cat after it is purged out is the bottle neck at the flange where the muffler attaches. Replacing the flange or cutting out the bottle neck and replacing it with larger pipe as I did, removes the Cat's biggest restriction. Bolting on a 2 1/2" Cat back with out getting rid of the Cat flange bottle neck will not produce optimum results. 20mbar = 0.294 PSI 40mbar = 0.588 PSI 80mbar = 1.176 PSI 100mbar = 1.47 PSI 400mbar + 5.88 PSI

Author:	ebbnflow [ Sun Jan 30, 2011 10:52 pm ]
Post subject:	Re: Magnaflow Installed 2 1/2" Cat back now
Warp, Do you still have the pics from your install? I want to replicate your setup and would like to have photos for reference. Thanks!

Author:	warp2diesel [ Wed Feb 02, 2011 12:01 am ]
Post subject:	Re: Magnaflow Installed 2 1/2" Cat back now
Photos relinked!!

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