Another Permanent SAI Fix
#31
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The primary purpose of the SAI is to put extra oxygen into the exhaust stream to burn the richer cold start fuel mixture and to jump start the cats. This fix still accomplishes the mission and is not likely to ever fail. Good Job!
#32
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Location: Scottsdale, AZ
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If I had a 77k car I would probably have it fixed and have the valve guides replaced at the same time. As I said, if the money is an issue the kluge works. I personally would have the car fixed right, but the money is not an issue and yes I would spend the 4 grand. If I were the potential buyer, I would wonder if there were other non factory mods. I once saw caulk used to replace the door seals on a 911 and a wooden block used to secure the battery in place. (it was supposed to have dual batteries).
#33
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Personal opinion on resale impact:
Working modification of a stupid SAI system: +$1000
If the modification is nicely done and reversable: +$1000
Non-stock mechanical modification in general: - $2000
Net impact= $0
Buying a car from a paying and participating Rennlist member,
priceless . . .
Well maybe not priceless, but it sure would give me A LOT of peace of mind
Working modification of a stupid SAI system: +$1000
If the modification is nicely done and reversable: +$1000
Non-stock mechanical modification in general: - $2000
Net impact= $0
Buying a car from a paying and participating Rennlist member,
priceless . . .
Well maybe not priceless, but it sure would give me A LOT of peace of mind
#35
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LOL.... I saw that car in excellence magazine..no? Isn't that some female rock star's car? My first impression was of course why?? Then when I read who the owner was It explained everything. Too funny...
#36
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Very kewl mod. I was wondering why Porsche routed the freekin' SAI system through the cam towers and heads instead of running some cheap tubing along the outside. But my understanding is the SAI air had to mix with the exhaust gases fresh out of the cylinder in order to work correctly.
Oh well, if this mod works, great!!! Give the stupid O2 sensors what they want, O2. If and when those tubes get plugged up, they should be a lot cheaper to replace than a top-end overhaul.
Oh well, if this mod works, great!!! Give the stupid O2 sensors what they want, O2. If and when those tubes get plugged up, they should be a lot cheaper to replace than a top-end overhaul.
#37
Race Car
#38
Rennlist Member
OK, here's the deal on air injection. Look at any 2.7 or early 3.0 car, plus 930's and compare that half-*** external manifold, big *** HP robbing air pump, and nozzles sticking into the exhaust port robbing even more power. Hans und Franz didn't show up hung over one morning and try to slap something together to meet a deadline. I think it's pretty well established we don't drive the cars quite as hard here? Probably works quite well as intended.
Now onto valve guides. I've taken apart 911 engines with as little as 15K factory miles. Remember, before Carrera tensioners A LOT of practically new engines failed. And we, as a matter of course, replaced the guides. I've probably only used 4 head guys in my life (Pete Zimmerman being one, I don't think he posts here.....just on the 911 board), and I've never NOT had it come back that they're out of tolerance. On the flip side, I've pulled apart 200K+ engines that were marching along not burning much oil at all.
Probably the worst oil burners of the bunch came of age when I was pretty much getting out of hard mechanical work--the 3.2's. 60-80K, and some of them were going through a quart every 4-500 miles.
Now onto valve guides. I've taken apart 911 engines with as little as 15K factory miles. Remember, before Carrera tensioners A LOT of practically new engines failed. And we, as a matter of course, replaced the guides. I've probably only used 4 head guys in my life (Pete Zimmerman being one, I don't think he posts here.....just on the 911 board), and I've never NOT had it come back that they're out of tolerance. On the flip side, I've pulled apart 200K+ engines that were marching along not burning much oil at all.
Probably the worst oil burners of the bunch came of age when I was pretty much getting out of hard mechanical work--the 3.2's. 60-80K, and some of them were going through a quart every 4-500 miles.
#39
Three Wheelin'
carcommander- I think it's safe to say we all dislike kluges, but this is kind of an exception. Porsche designed the system very very poorly. To rebuild the engine ($4000) for no other reason than to fix a minor emissions issue due to a poorly designed system is kind of silly.
#40
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Personally I think that mod is way too obvious. Considering it is illegal and carries severe fines, I would not do that mod or buy a car that had it. But then, I'm the type that won't remove my cats for the same reason. To each his own.
#41
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Regarding the workaround, if you subscribe to the theory that worn exhaust valve guides are a contributing factor to the SAI system clogging in the first place, and that replacing the guides with the harder phosphorous bronze aftermarket ones is the solution, then it makes sense to do the rebuild as your guides are probably worn anyway. At 58k miles, my exhaust guides were badly worn.
Also, FWIW, having looked into this solution before opting to have my guides replaced, 10 hours of labor seems a bit much to install a couple of bungs into the exhaust and run two air lines from the check valve to there. Maybe the first time it's done, but the shop I discussed it with up here (not the rebuild shop) put it at about half that.
I don't know about liabilities; the law in Massachusetts specifically allows "temporary" repair measures that are true to the overall design of the system, i.e., if the system still functions correctly, it's okay to modify it -- and in this case, since it's supposed to feed extra air to the cats on a cold start to get them hotter quicker, it would still be doing that as long as the air lines are placed before the cats.
YMMV ... I'm glad I had my guides done and don't expect further issues with them, but time will tell.
#42
Rennlist Member
A couple guys have noted that this is somehow true to the original system. But I think Porsche's goal was to have HOT air (not cold air) injected into the cats. This workaround doesn't do that. So AFAIK, this mod does not help emissions and thus runs counter to the intent of the system.
That said, I still like it.
That said, I still like it.
#44
RL Community Team
Rennlist Member
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I always wondered why my car's exhaust system had extra oxygen sensor bunges along its pipes with plugs screwed into them. Now it all makes sense, kind'a like someone at Porsche foresaw problems with the air injector system and pre-installed attachment points for a fix that preserves the integrity and function of the secondary air injection system. Gosh, who would think!