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alanganes
11-27-2010, 06:32 PM
I know we have some top notch auto repair folks here, so maybe a bit of advice, please:

The patient is my son's 1998 Chevy Cavalier, 2.2L 4 cyl, single cam. Fuel efficiency has dropped quite a bit, and we got a check engine light. Read the code, and it gave "P0420 Catalytic System Efficiency Below Threshold (Bank 1)".
A bit of research gives me generic advice that at idle, I should see a fluctuating signal on the upstream O2 sensor (sensor 1) and a pretty stable signal of about .5 or .6 V on the downstream O2 sensor (sensor 2).

My OBD reader can graph sensor outputs, so I set it up to look at those. The upstream sensor does indeed show a fairly regular signal, fluctuating between about .4 and .8 volts. The downstream sensor is pretty steady but may be a bit high at about .75 volts.

The major culprit would seem to point to a clogged or failed cat converter. I also know that blindly following OBD codes can occasionally send one barking up the wrong tree. Hence my inquiry here.

Anything else I ought to check or do before I go and change out the converter? The cat does not look too difficult to change in this car, but I'd hate to do it and not fix the problem.

Thanks for any advice.
-Al

Guido
11-27-2010, 07:48 PM
He must be out for the evening, but will be checking in at any minute.

--G

CCWKen
11-28-2010, 12:49 AM
You can swap the two O2 sensors and run the test again. They should be the same sensor. If you get the same results, then the sensors are probably good and it points to the cat. But first check for leaks in the exhaust from the head (manifold) to the cat. A leak or crack in the exhaust manifold can cause a 420 but it will also (sometimes) throw a lean code or at least show erratic (elevated) short-term fuel trim as the PCM tries to richen the mixture. (Air gets drawn into the exhaust from a leak) Also check the plugs and wires. A misfire can also cause your problem.

And, of course, the normal checks for chaffed wires causing intermittent shorts on the O2 circuit. Especially on the drop leads.

PeteF
11-28-2010, 02:15 AM
An actual faulty lambda sensor should give you a code for it, but if it wasn't for that I'd be going for the sensor rather than the converter. Many people don't seem to appreciate that the lambda sensors wear out, and I wouldn't be at all surprised to find one faulty in a car of that age. It's possible that at least one sensor is not actually worn enough to throw a code in itself, but generate another fault code for a related area. I'd consider the sensor that isn't changing voltage to be highly suspect IMHO.

Pete

Edit: I was hunting for some additional information on Lambda Sensor Life Expectancy and came across this site, I think it gives an excellent overview of the sensors http://www.picoauto.com/applications/lambda-sensor.html

alanganes
11-28-2010, 08:10 AM
Thanks guys. Good ideas and thanks for the link, Pete, good info there.
I did check for leaks and found nothing obvious. I'll do a more careful check when we get back at it this week. Swapping the sensors is a great idea, I'll give that a try too if they are indeed the same sensor. Plugs and wires are fairly recent, but I'll give them the once-over as well.

Thanks again for taking the time to reply.
-Al

vpt
11-28-2010, 08:16 AM
What does the exhaust smell like? Does the car have full power like it always has when you floor the gas peddle?

There are some possibilities. A plugged cat, bad injector (sticking open), bad plugs or wires or coils. A plugged cat should make the car sluggish and have limited power and the exhaust should smell very bad. A sticky injector will make the exhaust smell as well but the car will not have limited power. Plugs, wires, or coils the engine should have a miss or run bad.

Highpower
11-28-2010, 08:31 AM
I would check for continuity on the post catalyst O2 sensor heater first, as well as making sure it's getting voltage to it.

Next stop for me would be to check the coolant temp sensor output to the ECU. (False "cold" input into the computer screws up the internal test parameters.)

9 times out of 10 a P0420 code alone points to a bad cat vs. O2 sensor problems, but there is always the odd exception...

A.K. Boomer
11-28-2010, 09:54 AM
Cats can plug for all kinds of reasons but they can go the other way too, If a cylinder misfire (you stated poor economy) goes undetected its basically pumping in raw fuel (and air) directly into the cat- the cats job is to consume anything in its path but its capabilities are limited in what it can handle, a little four banger that's intermittently dedicating 25% of its power producing capabilities directly to heat ( i.e. the cat) can push a converter over the edge -- the results are a total meltdown and it starts directly in the center of the honey comb/ceramics and blows a path right through,
One quick check method is to go back to the muffler or even resonator and pound with your fist directly against gravity and then listen -- if it sounds like a bunch of little rocks shaking around inside then you just might have a cat that's had a meltdown...

saltmine
11-28-2010, 10:29 AM
First, don't bother switching the oxygen sensors. They each have a specific task, and are not intended to be switchable.

The front sensor (Bank 1) is what the engine calibrates from, for fine fuel mixture tuning...While the rear sensor (Bank2) only monitors the efficency of the catalytic converter by comparing it's reading with sensor 1. If both sensors read close to one another, the computer sees this as a loss of efficency. (the converter isn't doing it's job)

Loss of efficency doesn't usually impact fuel economy or performance. Aftermarket catalyic converters used to be "low restriction" and would set this code almost instantly. Besides, the sensor 2 oxygen sensor is a slow acting, "lazy" sensor meant only to monitor, not trace the variations of engine load and speed.

With an upstream sensor reading between .4 to .8 volts, the downstream sensor would, most likely, read .75 volts. That's telling me there's nothing going on in the converter.

Usually one of two things happen in the converter to cause this condition.
The matrix which carries the catalyst has fractured, and broken up, ending up in the car's muffler, or the catalyst has become coated and become ineffective. Now...should the substrate clog up the muffler, your performance will drop along with your fuel economy, because of the exhaust restriction.
Coated catalyst will simply cause the code to be displayed, unless it's coated so badly it restricts the exhaust.

Without any more information, I'd say to take the car to a reputable muffler shop, and have them do a pressure test (or take a backpressure reading).
This will determine if there's a restriction.

My younger brother has a '97 Cavalier with the same engine, and it just turned 400,000 miles a few weeks ago. Of course, his timing chain wore out around 200,000 miles and he had to replace the catalytic converter twice already...Other than that, he just puts gas in it, and changes the oil once in a while. And yes, he bought it new. He used to be a happy Honda owner but soon realized that Americans can build reliable cars too.

A little more information would prove helpful. Like how the car is driven...short trips, parked a lot, long expressway drives, etc. Has the car been serviced and maintained? What is the mileage on it?
Oil consumption? Hard starting? Information, information. After all you don't call your doctor and schedule an operation because you have a belly-ache, do you?

alanganes
11-28-2010, 02:00 PM
A little more information would prove helpful. Like how the car is driven...short trips, parked a lot, long expressway drives, etc. Has the car been serviced and maintained? What is the mileage on it?
Oil consumption? Hard starting? Information, information. After all you don't call your doctor and schedule an operation because you have a belly-ache, do you?


OK, guilty as charged! :o A bit more info:

Car is driven daily, but almost all short trips now, under 20 miles/day, most days around 10. All around town, mostly work-and-back type driving. No hard starting or significant oil consumption. He has only owned it for about a year, I would say it has had OK but not meticulous service in it's previous life. Got new plugs in the last year, gets oil changes and has had the basics like air filter, etc. changed. Over 100K miles but not by a lot, the exact number is escaping me. Have not noticed any obvious rough running or misfiring, but have seen a significant drop in fuel mileage.

All in all this has been a pretty good, cheap set of wheels.

Again, thanks for any guidance.

PeteF
11-28-2010, 05:24 PM
First, don't bother switching the oxygen sensors. They each have a specific task, and are not intended to be switchable.

With an upstream sensor reading between .4 to .8 volts, the downstream sensor would, most likely, read .75 volts. That's telling me there's nothing going on in the converter.

Yes I was thinking the same regarding swapping the front and rear sensors, however not being familiar with that specific model didn't want to comment.

Typically when people work on their cars they're not at operating temperature and this will cause unusual outputs on the sensors that may indicate a problem that isn't actually there. Just confirm the voltages you were providing were from a hot engine at normal operating temperature?

If it were me, I'd firstly look at the sensor outputs with a dead cold engine, they should follow each other a lot more closely as the converter hasn't lit up. If the rear sensor is flat-lining as you suggested, there's your problem as the converter isn't doing anything at this stage. Then try it again with a hot engine, in this case the rear sensor should be relatively stable but the front sensor will still be varying quite a lot. Assuming that checks out the next thing I'd do is take it to a garage and simply ask them to do an exhaust gas analysis. It should be quite an inexpensive step. If it's ok then chances are your converter is ok. If the exhaust gas isn't coming out clean then do a back-pressure check on the converter.

Assuming the converter was faulty, the question is why? They don't just fail for a laugh and a giggle because they're having a bad day. The reason I suggested to look firstly at the lambda (O2) sensor is because they most definitely do have a limited life span. Indeed 100k would be pretty much right on the money. On the other hand if the converter is blocked then something has caused that and you'd need to look at what/why before simply throwing in a new one. You should get more than 100k out of a converter before it throws up a fault unless there's something that's caused it to fail.

Hope that helps.

Pete

PS Do NOT start checking continuity of the sensors. If not done correctly you can damage them. A failed heater will definitely throw up a lamda sensor code so it's pointless to risk doing this anyway.

winchman
11-29-2010, 01:54 AM
"...and has had the basics like air filter..."

Changing the air filter on a modern (i.e. fuel-injected with computer control) car is a waste of money unless:

a) you drive the car at WOT, and want max power.
b) the filter is so dirty that the pressure drop is almost enough to collapse the filter.
c) you just want a new filter.

See: http://www.fueleconomy.gov/feg/pdfs/Air_Filter_Effects_02_26_2009.pdf

Arcane
11-29-2010, 04:31 AM
Not that this has anything to do with the OP`s original thread but...speaking of air filters...awhile back a friend had a customer come to his garage business complaining her car was running very poorly. What he found was that she had been going to one of those quickie-lube paces for a very long time, and they dutifully checked the air cleaner filter every time. Only trouble was, when they popped the filter housing apart, they didn`t bother to notice that the side they were looking at was the engine side. That side was very clean of course, but the other side...well, it couldn`t hold any more dirt. It was packed! I`ve seen a couple of other filters that he has replaced that were that bad, one had even been sucked off the sealing surface.

Black_Moons
11-29-2010, 04:36 AM
I got that same error code on my 1994 GMC serria, Reset it, came back a little while later...

My first reaction apon seeing the code was "Oh good, Its just the catalyitic converter, And here I thought it might be something to worry about.. Yaknow, Something my car actualy needs"

aboard_epsilon
11-29-2010, 08:15 AM
If you are getting bad fuel economy then the first thing i would look at is the COOLANT temperature sensor ..

if this goes up the spout ..it will :-

Make the engine run rich all the time ..you will probably notice that the tick over is high

This in turn will coat the cat with soot ..
coat the lambda probes with soot.

Hence other problems / fault codes arise from a minor one .

Note there are two temperature probes ..single wire for the car temperature gauge ..and two wire one is the one that is linked to the ecu.

also worth checking the thermostat.........

do a run in the car from cold ..dont have your heater on ...turn it off ..completly ..not blowing and on the cold setting .

note that the gauge should move progressively up ..for the first mile or so ...then move up above half way mark ..then drop down to about a 1/3 of the gauge...........this "above half way" .."then the drop to 1/3", is an indication that the thermostat doing its job.

well thats how its worked in every car Ive owned .

all the best.markj

vpt
11-29-2010, 08:52 AM
If there is a check engine light the ecu should be in open loop and going off of a base map for fuel and timing. Open loop operation will use a little more gas but not a significant amount. I am thinking it is not a sensor causing this issue, I am thinking still that is mechanical. I am still on injectors, plugged cat, bad coil. Since the OP said he changed plugs and wires recently that shouldn't be the problem.

Does the exhaust smell like raw fuel? Does it blow black smoke, even a little bit? Does the car have full power or does it feel restricted when at WOT? Does the exhaust sound restricted at WOT? Should be hissing or sound like a blow gun on a air compressor hose.

With the new and government improved ethenol gas I have been seeing lots of fuel related problems in vehicles like injectors, O-rings, fuel pumps, cats getting plugged up, etc.

alanganes
03-26-2011, 03:05 PM
OK, very long delayed update on this.

First, thanks to all who sent along replies they were all informative and helpful.

So after messing around some, winter came in here with a vengeance. Lots of snow this year and quite cold for around here. As most of my on-the-car work has to happen in the driveway, we delayed working on this until a few weekends ago when the snow had melted. We tried lots of small things none of which helped. The front and rear sensor readings were pretty much tracking each other, the front oscillating up and down and the rear following, with the expected delayed response. So I came to the conclusion that we would have to at least have a look at the cat to see if it was clogged or something.

So we open the flange just aft of the cat (it had been removed in the recent past by someone, the bolts and rear part of the exhaust system were obviously newer). I put my flashlight up and take a look down the pipe, and find that the catalytic converter is.....empty. No honeycomb, no baffles, no nuttin. Hollow. Apparently punched out by some previous repair guy. Well, that would explain the why the converter efficiency seems to be low.

The direct replacement unit is a $300+ assembly that starts at the manifold and goes the midsection of the car. I found I could get the one-size-fits-many generic cat for $115. Has the stuff inside of it and everything. So today after a bit of cutting and welding (I love my MIG machine today) we have what appears to be a working vehicle. Once it hits closed loop, the sensor readings make sense, the front bobbing up and down, and the rear near flat line. The rear reads a bit lower than typical (~0.2V), but seems to respond through the whole range when you rev up, and settles back down nicely when the revs steady out.

So sometimes the simplest and most obvious answer is even the correct one. Go figure.

airsmith282
03-26-2011, 04:24 PM
try putting in a new set of plugs, i was getting all kinds of fule promlems with my dads saturn aka GM car as well all know they are, anyhow new plugs got some E3 plugs and got not only al lmy power back but also iam back to pretty much normal fule usage as well and i also clenaed out the air filter to which was a bit clogged up,, lose or old plugs can also cause alot fo false readings to. they say to raplce the plugs every 168,000 bu thats total BS, 2 of the plugs where burnt right out and the computer had to comensate for this, any how just an idea for ya, if neew plugs are done and airfilter is cleaned or replaced and you still have the same sort of thing at lease you elimate one part for sure..

firbikrhd1
03-26-2011, 05:43 PM
This suggestion may be way off and not help at all, but it's cheap so worth doing. In computerized vehicles electric connections can give a great deal of trouble. I read once in a factory service manual that connections are the single most cause of trouble. Salted roads and high humidity serve to cause connections to corrode at the various plug type connectors, particularly on high mileage older vehicles. If it were me I would trace the wires and take each connection apart to insure they are clean and corrosion free. As I said, it's cheap insurance and may ultimately save you from doing a lot of parts changing in an attempt to track the trouble down.

PeteF
03-26-2011, 07:38 PM
Alan, thanks for following this up, sadly very few people take the time to do so and it's nice to hear the answer to a problem in which one has tried to provide some input. Sounds like it wasn't all that expensive ... and you got to justify the MIG. Hope you kept announcing in front of the family "Wow! I sure am glad I have this MIG!!!" :D

Pete

vpt
03-26-2011, 07:55 PM
Yes! Always great to hear the outcome. I wouldn't have guessed a gutted cat. With an aft o2 sensor most of the time people put a fouler on the rear o2 to fool it. Is there a 1"ish fitting between the o2 and the o2 bung?

saltmine
03-26-2011, 09:00 PM
Provided the sensors were working, I'd suspect a gutted catalytic converter around my neighborhood more often than not. Local "mechanics" usually remove or destroy anything they don't understand..(and they don't understand a lot). A good example would be an ex-neighbor I had a few years ago. He had a port injected, computer controlled 5.0L Mercury sedan.
One fine day, it quit on him. After about a week of homegrown diagnosis, he came to the conclusion that the "Dura-spark" ignition amplifier had taken a "dirt nap" and would no longer trigger the coil to make spark.

A visit to our local "Vato-Zone" put him in a state of shock when they told him a new "Dura-Spark" box would cost him about $200...and yes, they had one in stock. He didn't want to put a $200 module in a $150 car, so, he questioned a local axe murderer masquerading as an "automotive technician" at the Ford dealer about it. The "technician" told him to go to the junkyard, and get a "points distributor" off of an older 5.0L Ford, and graft it in. Well, that's what he did...Last time I saw him, he was tooling around with a high tech fuel injected engine sparked by a 35 year-old points ignition, and a "check engine" light glowing merrily on his dash.

Funny you should have a P0420 DTC. According to my latest issue of Motor magazine (March 2011) The P0420 code is one of the most common trouble codes they found while doing a survey. BUT, they also said that a P0420 can be set by totally unrelated events. A failing temperature sesor, vacuum leaks, fuel in the oil, injectors needing service, misfires, and even missing heat shields. If you want to read about this go to <www.motormagazine.com> and look up Karl Seyfert's column this month.

vpt
03-26-2011, 09:07 PM
I picked up MPG's when I installed a test pipe in place of my cat in my 96 F250. But that is a vehicle with NO downstream o2 of the cat.

alanganes
03-27-2011, 08:49 AM
Around here they check for a cat as part of your vehicle inspection, so I guess a test pipe is too obvious. Still, if you don't pass the emissions test, no sticker.

Nope, no plug forward of the sensor. :)

Thanks saltmine, for the link to that article, interesting read. The diagnostics stuff that came with my OBD reader speaks to some of that. All of these systems are so interdependent it can be pretty tricky to diagnose root cause sometimes. I'll have to revisit this, as my wife's Subaru seems to have developed the same code and the sensor outputs look similar. I know that one is not punched out, as it worked properly before. Most timely info for me. Oh well, another project.



I generally view working on cars as just an onerous chore these days, but got some satisfaction form this one. It felt good to spend some time outdoors, my older sons spent the day hanging around working on the cars, and I actually accomplished something useful for a workable amount of money. A nice day, actually.

As for the MIG welder, it is an older Lincoln 200A machine. It is sort of large for my shop, and I often think I should sell it and get a more modern & compact TIG or something. Then every time I use it, I decide that it is just too darn nice to sell...

saltmine
03-27-2011, 12:18 PM
Easily predictable, VPT. Just about anything you do to a Ford exhaust system improves it. Back in the '60's and '70's, Ford's exhaust manifolds were so restrictive that even poorly designed headers made massive improvements in power and economy. Many header manufacturers, at the time, jumped on this opportunity and declared "all stock exhaust manifolds were restrictive", even though tube headers seldom made much of a difference on anything but Fords.

A.K. Boomer
03-27-2011, 02:12 PM
no reason for a thanks - just pass it along to someone in need of your area of expertise,

there's a reason for my original diagnostic post being about a meltdown gutted cat instead of a "manually" gutted one though, and that's the fact that your O.P. stated that the car dropped off in mpg's and THEN a check engine light came on, If the cat was already gutted and has a sensor before and aft then the check engine light would have been on all the time... just saying somethings still not totally up to snuff unless you have some more info?

vpt
03-27-2011, 03:04 PM
Easily predictable, VPT. Just about anything you do to a Ford exhaust system improves it. Back in the '60's and '70's, Ford's exhaust manifolds were so restrictive that even poorly designed headers made massive improvements in power and economy. Many header manufacturers, at the time, jumped on this opportunity and declared "all stock exhaust manifolds were restrictive", even though tube headers seldom made much of a difference on anything but Fords.



The worst I have seen is on our 94.5 7.3 IDI turbo diesel. In a hurry to keep up with market ford slapped a undeveloped ATS turbo system on their 7.3's and pushed them out the door. Well while out at work one day my mother went out and decided to get one for the business and bring it home to surprise us!

The exhaust system on that thing is horrendous! Most restrictive poorly designed stuff I have even seen from manis to tail pipe. Then no intercooler attempt at all, just turbo outlet plugged right into intake manifold. I was disgusted to say the least.

alanganes
03-27-2011, 04:35 PM
no reason for a thanks - just pass it along to someone in need of your area of expertise,

there's a reason for my original diagnostic post being about a meltdown gutted cat instead of a "manually" gutted one though, and that's the fact that your O.P. stated that the car dropped off in mpg's and THEN a check engine light came on, If the cat was already gutted and has a sensor before and aft then the check engine light would have been on all the time... just saying somethings still not totally up to snuff unless you have some more info?


Good call, you did mention an empty/damaged/blown out cat, didn't you. I did try the "knock on the muffler" check you mentioned, but heard nothing. The previous owner lived across the border in NH, so the inspection requirements are different. I know the light was not on when he got the car, and he only owned it for a while before all this started. It sure looks to have been "manually" gutted, there is not a single speck of the original guts in there, it's clean out to the walls. I'm not 100% sure on the mileage dropping before the light came on, but in any event the car seems to be running great as of right now. We'll see what happens in the next few weeks, I guess.

The car was a freebie, given to my son by a friend of mine. If he had punched out the cat, he'd have told me. He did have the car worked on by someone, but I forget for what. Perhaps that's what they did. If he can get another year or so out of it, when he finishes grad school, it will have been well worth what's been put into it to this point.

In any event, thanks for the input, good call and very much appreciated, A.K. I can always count on this crowd for good advice on stuff like this.

spope14
03-27-2011, 08:30 PM
Glad it all worked out for you. I get the manifold on down thing, my Cat showed bad, but unfortunately turned out to be a cracked manifold.

saltmine
03-27-2011, 11:58 PM
390 Ford V-8's had probably the worst exhaust manifolds ever made. I recall one customer who came in with a manifold cracked in half, wondering if I could quiet it down but leave the back-pressure alone.(he claimed it really ran better with the manifold hanging in two pieces)

Ah yes...The old "anti-fouler screwed into the oxygen sensor bung" Surprise! The anti-fouler will indeed screw into the sensor bung....BUT the oxygen sensor won't screw into the anti-fouler. The body of the anti-fouler is too small to pass the sensor element down inside it....BUT, if you chuck the anti-fouler up in a lathe (machining content) you can enlarge the through hole enough to take the sensor easily (don't ask how I know this).

And, yes, many people have paid to have their catalytic converter replaced only to find their car's performance still lacking...because the muffler is full of broken catalyst matrix...that the installer SHOULD have checked ...

vpt
03-28-2011, 08:11 AM
The threw hole on the fouler is jetted to be small to fool the o2 sensor. Did you open up that hole or just the pocket the o2 sits in? Either way it is a bandaid fix just like the inline resistor some companies sell.

All the honeycomb from the cat in the muffler is a funny one and I have seen what you mentioned before. One guy said "I had my cat replaced and now something is rattling, I think the guy messed up a hanger or something". Another great one that is happening now is the high quality ebay exhausts. Nearly half of my exhaust fixes lately have been poor fitting aftermarket ebay exhausts. The customer will call me and ask for say a cat back exhaust quote. I tell them what it would be for me to build it and they say thats way more then I can buy it for off ebay. (normally 2-3 times as much for me to build it over ebay) I try to explain ebay exhaust quality but they can't get past the price so they buy it anyhow. They go to install it and what do you know, it doesn't fit and if it does fit it is hitting and rubbing on everything under the car. Then that same guy calls me and asks "how much to fix my ebay exhaust?" lol By the time it is all over the guy ends up spending about $100 less then if I would have built the exhaust from scratch and he is still stuck with cheap thin wall 409 stainless ebay exhaust.

But its business and the way I look at it is if it weren't for ebay the guy probably would have never been able to afford the exhaust in the first place so I wouldn't have had any business from him. At least this way ebay gave me business.

saltmine
03-28-2011, 11:25 AM
Long story. A friend was beating his brains out trying to fool the computer in his car (for some reason). He tried resistors here and there, blocking this & that off, and adding gallons of unmentionable "snake oil" to his fuel...all in the pursuit of better performance & gas mileage. The list goes on. Just about any "crackpot" scheme to improve performance was tried. Sometimes he would bring me a gadget, and I would look at it and laugh. The theories these guys worked off of were obscure and mostly amusing.

He had heard somewhere that if you moved the oxygen sensor out of the exhaust stream, it would report a leaner mixture. That won't work, I told him...a leaner exhaust means the computer will richen up the fuel mixture to compensate. No, he had other ideas...
I ended up boring out the anti-fouler he brought me, so the sensor would fit inside it. It fit well into the pipe, and the sensor fit into it...only when he drove it, black smoke issued out the back, and the computer set a code for a faulty oxygen sensor to boot.... AND HE REPLACED THE SENSOR!!

I worked in a muffler shop for years, way back when... Fortunately, there wasn't an eBay to peddle cheapass exhaust systems to my customers. Once in a while, I would get somebody with a box full of polished stainless steel pipe, wanting an exhaust sysem assembled from it. Fun.. I usually ended up cutting up $1000 worth of stainless tubing to build a custom exhaust system.
We didn't use MIG welders, back then, so, I had to build the whole thing with a TIG. Hang the parts, tack 'em, and then remove them and weld them on the bench...Funny, I could have bent up a set of regular steel pipes, gas welded them together and hung the system in a matter of hours, instead of sawing and cutting dozens of tiny pieces of stainless, then welding them together over a period of sometimes days. I guess the owner didn't want to be embarassed by a set of ugly bent pipes when he flipped his car on it's lid.
I'll never know. Today, everything is DOM, mandrel bent with paper-thin outer walls and polished like chrome...Looks nice....nice & expensive...

vpt
03-28-2011, 07:50 PM
Those little chunks of stainless pipe is the most comon thing I have to fab on cars. In fact it is what I was doing today.

http://img59.imageshack.us/img59/5421/porsche013.jpg

http://img834.imageshack.us/img834/4608/porsche023.jpg