Catalytic on Fed Model

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webwalker
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Catalytic on Fed Model

Post by webwalker » Wed Oct 17, 2012 10:41 am

I tried this over at TS and got a blank look, so I'll try here.

FI buses got a catalytic converter. California models all had them, Federal only got them in 79. Other than the obvious matter of cost, why would VW leave the cat *off* of the Federal models?

But the primary interest is: Is there any reason for me not to take advantage of a cat to help with my emissions? Not as a crutch for an incorrectly tuned engine, but as as an assist for an engine design that was marginally compliant at the time, and doesn't have much tolerance for even minor out-of-tune issues.

M

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airkooledchris
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Re: Catalytic on Fed Model

Post by airkooledchris » Wed Oct 17, 2012 11:16 am

What year bus do you have currently? Do you have a working EGR valve/filter? Have you failed smog tests with this bus in the past?

Just a guess, but id say that they didn't use them because they were able to tune the motor well enough to pass smog without them.
Why pay all that money for them if they can get away without?
1979 California Transporter

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Amskeptic
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Re: Catalytic on Fed Model

Post by Amskeptic » Wed Oct 17, 2012 2:34 pm

webwalker wrote:Is there any reason for me not to take advantage of a cat to help with my emissions?
Catalytic converters have one enormous drawback with an air-cooled engine:
heat.

They require a lean mixture to stay chemically cool... this causes hot exhaust valves.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Catalytic on Fed Model

Post by webwalker » Wed Oct 17, 2012 7:40 pm

Right. And I noted that the ACVW runs happy richer than stoic, and that's shortly going to make the CAT sad.

So why did VW do this? Was it the only way to marginally pass the new regulation, even if the correct fuel/air ratio would eventually (shortly?) kill the CAT.

So is there any way to successfully use a CAT with an ACVW?

M

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Re: Catalytic on Fed Model

Post by webwalker » Thu Oct 18, 2012 8:02 am

airkooledchris wrote:What year bus do you have currently? Do you have a working EGR valve/filter? Have you failed smog tests with this bus in the past?

Just a guess, but id say that they didn't use them because they were able to tune the motor well enough to pass smog without them.
Why pay all that money for them if they can get away without?

If my purpose were to 'do without, because I can' then there are lots of things I'd do without. That's not my purpose.

My purpose is to allow the engine to function at the peak of its ability in terms of both longevity and inspect-ability. It marginally eases my conscience to make the vehicle run 'as clean as possible, given the design limitations.' It's just the kind of screwball thing you would expect from an engineer: find some adaptive way to make a object do something it might not have originally been designed to do, rather than just eat the dog food that it currently offered on the market.

As an addendum: If the CAT needs a leaner input to maintain its chemical efficacy than the ACVW engine can put out, how did VWdMx solve the problem with the 1600i engine in the last generation of Type1 which had Digifant Injection and a 3-way CAT?

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Re: Catalytic on Fed Model

Post by Amskeptic » Sun Oct 21, 2012 6:21 am

webwalker wrote:
airkooledchris wrote:What year bus do you have currently? Do you have a working EGR valve/filter? Have you failed smog tests with this bus in the past?

Just a guess, but id say that they didn't use them because they were able to tune the motor well enough to pass smog without them.
Why pay all that money for them if they can get away without?

If my purpose were to 'do without, because I can' then there are lots of things I'd do without. That's not my purpose.

My purpose is to allow the engine to function at the peak of its ability in terms of both longevity and inspect-ability. It marginally eases my conscience to make the vehicle run 'as clean as possible, given the design limitations.' It's just the kind of screwball thing you would expect from an engineer: find some adaptive way to make a object do something it might not have originally been designed to do, rather than just eat the dog food that it currently offered on the market.

As an addendum: If the CAT needs a leaner input to maintain its chemical efficacy than the ACVW engine can put out, how did VWdMx solve the problem with the 1600i engine in the last generation of Type1 which had Digifant Injection and a 3-way CAT?
The first-generation two way CAT equipped VWs barely scraped past the emissions requirements with some lean driveability issues well covered in new car reviews.
In 1979, VW went all ox sensor feedback Lamba loop for the sake of the catalytic converter, and they had to use a Hall Effect ignition system as well, to get rid of every stupid little misfire possible. VW switched to water-cooled in the Vanagon in 1983 because the work load was just too much for air-cooled engines trying to meet emissions. Porsche switched to water-cooled heads in their competition engines then water-cooled everything in 1998.

Digifant was a beautifully integrated system that was able to manipulate timing/mixture/idle speed and our overall technical understanding of how to make an engine survive allowed the Mexican air-cooled light little Beetles in urban Mexico City to squeak in a few years before it was conclusively proved that the heat problem was insurmountable.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Catalytic on Fed Model

Post by webwalker » Mon Oct 22, 2012 1:53 pm

Colin,

Thanks for the rap on these. It was still an awful long time with the Digifant engine (10 years, times how ever many units they sold as taxis...not a small number.) I know that the 3way CAT was added for this generation, that combo unit of CAT and Muffler welded together and costing almost as much as the engine. (Kidding...mostly.) It did make me wonder about all of the shooting over exhaust systems whether it would have been worth it to look at adapting that combo CAT/MUFFLER for the Type4. But if the answer is, "you can't make the design run happy AND not eat valves AND with conscionable emissions' then it seems I'm back where I started: make the type4 I have work as well as it possibly can within its design spec, with the parts I can get.

BTW, Is there a single place you've collected your experience having rebuilt your type4 engine 'several times' for the home mechanic looking to a rebuild for the first time?

M

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Re: Catalytic on Fed Model

Post by vwlover77 » Tue Oct 23, 2012 5:22 pm

FWIW, I'm running a 2-way cat on my '78 Bus, but I've got a '77 computer in it. The cat does give off a little of the "rotten egg" smell due to a slightly rich mixture, but it has not overheated or cloggged in the 12,000 miles it's been installed. Here's my original post on it....
viewtopic.php?f=46&t=7219

Also, the '79 Federal model Bus I used to own had a cat with no O2 sensor and no hall-effect igntion. Wasn't my setup standard for 79 Federal ?
Don

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71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Catalytic on Fed Model

Post by SlowLane » Tue Oct 23, 2012 6:11 pm

vwlover wrote:Also, the '79 Federal model Bus I used to own had a cat with no O2 sensor and no hall-effect igntion. Wasn't my setup standard for 79 Federal ?
Yep, it was. Colin was generalizing a bit. Only California got the 3-way cat, oxygen sensor and Hall-effect ignition from '79 to '83. Federal models got points and condenser and a 2-way cat. Canadian models got points and condenser and a straight pipe.

I'm currently in the sticky situation of having stupidly imported a Canadian '81 to California. Since it never had a cat to begin with, I was forced to install a CARB-approved 3-way cat ('cause them's the rules), which my non-O2 equipped L-Jet system is utterly unable to feed properly.

I just had it into the smog referee yesterday, and even though I had the AFR tuned to within a hair of stoichiometric, the darn thing failed with over 2% CO. I am baffled now.
'81 Canadian Westfalia (2.0L, manual), now Californiated

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Amskeptic
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Re: Catalytic on Fed Model

Post by Amskeptic » Thu Oct 25, 2012 8:30 am

SlowLane wrote:
vwlover wrote:Also, the '79 Federal model Bus I used to own had a cat with no O2 sensor and no hall-effect igntion. Wasn't my setup standard for 79 Federal ?
Yep, it was. Colin was generalizing a bit. Only California got the 3-way cat, oxygen sensor and Hall-effect ignition from '79 to '83. Federal models got points and condenser and a 2-way cat. Canadian models got points and condenser and a straight pipe.

I'm currently in the sticky situation of having stupidly imported a Canadian '81 to California. Since it never had a cat to begin with, I was forced to install a CARB-approved 3-way cat ('cause them's the rules), which my non-O2 equipped L-Jet system is utterly unable to feed properly.

I just had it into the smog referee yesterday, and even though I had the AFR tuned to within a hair of stoichiometric, the darn thing failed with over 2% CO. I am baffled now.
Yeah yeah yeah yeah yeah I was generalizing in a progressive direction from simpler to complicateder. California always served as a "beta roll-out".

Sorry about your fail. Carbon monoxide is partially burned. Carbon dioxide is fully burned. Hydrocarbons are unburned. Nitrous oxides are too-hot burn.
What you have is I think too cool combustion.
A) Did you change your oil? Did you have the engine *fully* warmed up? Clean air filter?
B) How were your NOX emissions? Can you afford to heat up the works by going leaner, or are your NOX emissions too close to the ceiling?
C) How were your HCs?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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SlowLane
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Re: Catalytic on Fed Model

Post by SlowLane » Thu Oct 25, 2012 9:53 pm

Sorry, don't mean to veer off-topic, but you did ask:
Colin wrote:A) Did you change your oil? Did you have the engine *fully* warmed up? Clean air filter?
Oil was changed recently, before I went to the referee the first time in August (he refused to do anything at that time because I didnt have a Letter of Conformity from VWoA. Now I gots the letter). Air filter was replaced at same time.
Engine was warm, though I wasn't able to take it for a good long high-speed burn, as I was taking time out of my work-day to visit the referee. What ticked me off was that he let it idle for 30-40 minutes while he pissed around and we argued about what emissions components the van was supposed to have before he put it on the dyno for the rolling test, so I don't know what effect that extended idling had on the test.
Colin wrote:B) How were your NOX emissions? Can you afford to heat up the works by going leaner, or are your NOX emissions too close to the ceiling?
C) How were your HCs?
NOx was lower than average, HC was slightly high (failed at 25 MPH), detected Oxygen was 0%. All consistent with a too-rich, too cool mixture. Which was most frustrating because I had meticulously tweaked the mixture control to give 14.5-14.7 AFR at idle, 15 MPH and 25 MPH. That should have set the CO to less than 0.7%. Of course I wasn't allowed to sit in the van and watch the AFR meter as they performed the test, so I don't know if the measured AFR matched the test results or not.

I had also installed points and condenser prior to bringing it in, because I didn't want the hassle of arguing with him that the XR-700 was an allowed replacement. Even though I set the timing to 7.5 BTDC by the plastic scale, their analyzer read it as 5 BTDC.

So over the last couple of days I've bumped the timing up by a couple of degrees (trusting that their equipment is better than mine), performed a free-air calibration of the LC-1, and turned out the mixture screw by 1/4 turn. The van fairly ROMPS now! It just blasted up a local hill at 4000RPM in third that it used to struggle to hold at 3500. Could be the colder weather, but I can't recall when it's felt this peppy.

After recalibration, the LC-1 does seem to read a bit richer than it did before, so that could have been a contributing factor in the test failure, but it's not a large enough difference to account for the readings they got.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
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Re: Catalytic on Fed Model

Post by Amskeptic » Sat Oct 27, 2012 9:02 am

SlowLane wrote:Sorry, don't mean to veer off-topic, but you did ask:
Colin wrote:A) Did you change your oil? Did you have the engine *fully* warmed up? Clean air filter?
Oil was changed recently, before I went to the referee the first time in August (he refused to do anything at that time because I didnt have a Letter of Conformity from VWoA. Now I gots the letter). Air filter was replaced at same time.
Engine was warm, though I wasn't able to take it for a good long high-speed burn, as I was taking time out of my work-day to visit the referee. What ticked me off was that he let it idle for 30-40 minutes while he pissed around and we argued about what emissions components the van was supposed to have before he put it on the dyno for the rolling test, so I don't know what effect that extended idling had on the test.
Colin wrote:B) How were your NOX emissions? Can you afford to heat up the works by going leaner, or are your NOX emissions too close to the ceiling?
C) How were your HCs?
NOx was lower than average, HC was slightly high (failed at 25 MPH), detected Oxygen was 0%. All consistent with a too-rich, too cool mixture. Which was most frustrating because I had meticulously tweaked the mixture control to give 14.5-14.7 AFR at idle, 15 MPH and 25 MPH. That should have set the CO to less than 0.7%. Of course I wasn't allowed to sit in the van and watch the AFR meter as they performed the test, so I don't know if the measured AFR matched the test results or not.

I had also installed points and condenser prior to bringing it in, because I didn't want the hassle of arguing with him that the XR-700 was an allowed replacement. Even though I set the timing to 7.5 BTDC by the plastic scale, their analyzer read it as 5 BTDC.

So over the last couple of days I've bumped the timing up by a couple of degrees (trusting that their equipment is better than mine), performed a free-air calibration of the LC-1, and turned out the mixture screw by 1/4 turn. The van fairly ROMPS now! It just blasted up a local hill at 4000RPM in third that it used to struggle to hold at 3500. Could be the colder weather, but I can't recall when it's felt this peppy.

After recalibration, the LC-1 does seem to read a bit richer than it did before, so that could have been a contributing factor in the test failure, but it's not a large enough difference to account for the readings they got.
Careful that you do not assume that high HCs are too rich. They can be from a lean misfire just as easily.
I was surprised to find that the BobD did better with fuel economy when I richened cruise, something about increased efficiency aloowing me to back off the accelerator. I think you pivoted at 14.7 because it sounded theoretically right, when in fact it was causing crazy lean misfires.
Remember that retarding the mixture helps heat the exhaust manifolds, a good thing.
Dealing with people who have to interact with rigid bureaucratic methodologies is an exercise in frustration no doubt. A little empathy with their plight goes a long way towards establishing a working relationship through the process.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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SlowLane
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Re: Catalytic on Fed Model

Post by SlowLane » Sat Oct 27, 2012 10:08 am

Colin wrote:Careful that you do not assume that high HCs are too rich. They can be from a lean misfire just as easily.
I wasn't focussing on the high HC count, but rather was taking the combination of low NO (206 ppm), high CO (2.43%), high HC (138 ppm) and non-existent free oxygen (0.0%) as cumulative evidence of a too-rich mixture. I would have thought that at least some O2 wuld have been measured if teh engine was running lean.

I'm also concerned that a the #4 spark plug is consistently showing sootier than the other three plugs. When you were here we noted that and theorized that the oil ring might have its gap at the bottom. I'll be pulling the plugs for another inspection today.
I was surprised to find that the BobD did better with fuel economy when I richened cruise, something about increased efficiency alowing me to back off the accelerator. I think you pivoted at 14.7 because it sounded theoretically right, when in fact it was causing crazy lean misfires.
I am concerned aout lean misfires, particularly with the stock points and coil. The engine does stumble at the crucial 2000 RPM speed when not fully warmed up, which I take to be a sign of misfiring. I will be looking at ignition upgrading options that I can definitivley defend to the referee with the Executive Order system.

I do have one of the California-emissions Hall-effect ignition systems that I was running on the van for awhile. It worked great, but it has the advance-retard vacuum can on it, which I'm sure he'd notice. The single-advance can doesn't bolt on to the Hall-effect dizzy, so I'd have to explain why I didn't have the retard side of the can hooked up.
Remember that retarding the mixture helps heat the exhaust manifolds, a good thing.
:scratch: Retarding the mixture?? Sorry, haven't had coffee yet. Retarding = leaning?
Dealing with people who have to interact with rigid bureaucratic methodologies is an exercise in frustration no doubt. A little empathy with their plight goes a long way towards establishing a working relationship through the process.
Actually he was pretty flexible, within the bounds he has to operate in. When his official information source said that my car wasn't supposed to have an EGR valve, but was supposed to have an oxygen sensor, he was willing to accept the contrary evidence I showed him in the owners manual. I tried to joke that I wouldn't have gone to the trouble of adding an EGR system if it wasn't there to begin with. He's not a jocular type. 100% business-like, which I suppose he has to be.

I don't know if this is typical, but the referee station is at a local college, where they train more referees and automotive techs. They use students as inexpensive labour for the referee program. It has the feel of a high-school auto shop. There was a 914 perched on a hoist in the corner of the parking lot which is apparently the project of one of the instructors. I guesss the referee guy has the additional stress of needing to maintain his authoritative standing to his students, so he's not about to take much crap from some guy with a beat-up old VW.

To webwalker: didn't mean to thread-jack here. For what it's worth, I've strapped a CARB-certified 3-way cat to my Federal-spec engine. So far it doesn't seem to have helped emissions. At the same time, it doesn't seem to have hurt either. I noticed no change in performance when I bolted on the cat.

If you are truly interested in improving the emissions on your vehicle, and if it's permitted in your jurisdiction, then maybe look into implementing a Megasquirt solution. That should appeal to your engineering mind-set. :geek:
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: Catalytic on Fed Model

Post by airkooledchris » Sat Oct 27, 2012 9:50 pm

SlowLane wrote:I do have one of the California-emissions Hall-effect ignition systems that I was running on the van for awhile. It worked great, but it has the advance-retard vacuum can on it, which I'm sure he'd notice. The single-advance can doesn't bolt on to the Hall-effect dizzy, so I'd have to explain why I didn't have the retard side of the can hooked up.

Image


no?
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Re: Catalytic on Fed Model

Post by SlowLane » Sun Oct 28, 2012 7:00 am

airkooledchris wrote:
SlowLane wrote:I do have one of the California-emissions Hall-effect ignition systems that I was running on the van for awhile. It worked great, but it has the advance-retard vacuum can on it, which I'm sure he'd notice. The single-advance can doesn't bolt on to the Hall-effect dizzy, so I'd have to explain why I didn't have the retard side of the can hooked up.
<Image proving me wrong>

no?
Hey, cool. I'll have to take another look at mine. I was pretty sure they didn't match up.
Thanks Chris.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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