# Air Shrouded Injectors?



## Jimmie J. (Nov 20, 2001)

I'm using an '86 GTI longblock in an '82 Cabriolet. I'm not converting to CIS-E (still using the '82 CIS). 
I have a question about the vaccum connection on the back of the head for "air shrouded injectors." May I just block this off, or should I connect it somehow to my intake? I'm using all the injectors, cups, & brass inserts from the 1.7L that was in the car, and so far as I can tell, that head didn't have anything like that. 
I'm kind of hoping I can just block it off, but I need to know if thats the right thing, this needs to be a reliable car all winter long. 
Thanks!








Jim


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## 85vdub (Apr 9, 2003)

i'd just block it off wita small soft plug. It isn't needed and truthfully i'm not real sure it does a whole lot anyways.


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## saporter (Sep 10, 2003)

*Re: (85vdub)*

A friend of mine did some dyno testing to see the difference between using air shrouding or not. The results...none.
Sean


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## Jimmie J. (Nov 20, 2001)

*Re: (saporter)*

Awesome, that means I'll be blocking off that hole tonight, and prolly trying to start the beast.. 
Thanks!
Know what the purpose of air shrouding even is? Is it supposed to help the spray pattern or something?


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## sdezego (Apr 23, 2004)

*Re: (Jimmie J.)*

It was suppose to help atomize the fuel better for combustion efficiency. If it did, there were no results on the dyno or fuel efficiency that I know of...
S


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## Jimmie J. (Nov 20, 2001)

*Re: (sdezego)*

I had a sneaking suspicion thats waht it was all about... It doesn't really do much in the manual in the way of explaining about that.


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## saporter (Sep 10, 2003)

*Re: Air Shrouded Injectors? (Jimmie J.)*

I'm running the Bosch brass injectors from a Mercedes. I don't even use the little stainless caps that come with our VW injectors. These are supposed to be part of the "air shrouding" thing. I can't tell the difference.
Sean


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## Jimmie J. (Nov 20, 2001)

*Re: Air Shrouded Injectors? (saporter)*

oh wow... haven't heard of doing this before. Is there any advantage, or is it just something you had around and used? I'm not sure what the stock ones are made out of, but I'm sure its just as soft as brass. 
Might be pretty interresting cause its the first time I've heard of these injectors. 
I blocked off the port in the back of the head last night... even cut my own little gasket for it. 
Tonight I'll be hooking up the fuel, and setting it up. 
Let's hear if there's an advantage to those injectors. 
Thanks, 
Jim
PS-I prolly should have wired up the knock sensor ign. from the '86... oh well


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## ABA Scirocco (May 30, 2001)

*Re: Air Shrouded Injectors? (Jimmie J.)*

Here's my experience with the Benz injectors. http://forums.vwvortex.com/zerothread?id=469568


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## ragnar's vw (Oct 3, 2004)

*Re: Air Shrouded Injectors? (Jimmie J.)*

the "air shrouding" had nothing to do with atomization. it had to do with keeping the injectors cool especially after shutdown. otherwise the fuel would cook in the injectors and carbon them up. another thing to help that from happening was the temp switch near the intake manifold that turned the radiator fan on if the air around the head/intake got to hot. as for unhooking it, here's a reason they made it that way plu stock is cool http://****************.com/smile/emthup.gif


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## 85vdub (Apr 9, 2003)

OK your logic gave me a nice chuckle... the air shrouded injectors aren't going to do a damn thing if air is not flowing. When your car is shut off is there air flowing through the intake and the air shrouded injectors to keep them cool? I didn't think so. It might help keep them a bit cooler when running but i bet within a min of turning the thing off they are close to the same temp as the head and intake manifold given their location. the air shrouding was designed to help atomize the air and increase fuel economy do a bit of research cause i've read it more than once.


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## ABA Scirocco (May 30, 2001)

*Re: Air Shrouded Injectors? (ragnar's vw)*


_Quote, originally posted by *ragnar’s vw* »_the "air shrouding" had nothing to do with atomization. it had to do with keeping the injectors cool especially after shutdown. otherwise the fuel would cook in the injectors and carbon them up. 

HUH, where are you getting that?? That can't possibly be right, after all VW ran not shrouded injectors from 76 or 77 up to 84, so that's millions of cars and I've never seen or heard of anyone "cooking" injectors. And the only temperature switch controlling the fan is mounted to the radiator, there's nothing of that sort near the intake manifold.


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## Jimmie J. (Nov 20, 2001)

*Re: Air Shrouded Injectors? (ABA Scirocco)*

Wow... it appears I've opened a can of worms unknowingly.








I can see how it might help fuel atomization by way of releasing excess pressure after the injector, allowing the spray to spread throughout a little bit better. The excess would be recirculated, and burned again, just like about 99% of all the other stuff VW did that for.
I can also see how it might have a cooling effect, however, if your fuel injectors are good, they shouldn't be leaking anything at all. Which to me says that there shouldn't be anything to build up. Not to mention, no matter how hot your motor gets, its still not hot enough to burn fuel & air, even if your block has hot spots which causes the engine to stutter on shut-off. If your referring to inside the fuel injector, its impossible, as the fuel system (when it has fuel in it all the time) is airtight. If you run out of gas, the incoming fuel pushes the air out of system, or it vents back into the tank, and then the atmosphere. 
What I DO think maybe that VW had in mind was to keep carbon deposits that work they're way up from the combustion chamber into the intake ports from getting on the nozzle, which I believe might be the biggest cause for leaky fuel injectors, besides wear on the nozzle. Which I haven't really ever heard of. That little air shroud might just be enough to keep carbon away. 
Who knows what the deal is with it. It sounds like something you should run if you don't tear your motor apart every so often, and something you don't need to worry about if you do. If you ask me, from what I've heard, and examined, its nothing to worry about in the first place. Just like older VW AC... it didn't really work that well from the factory, so just get rid of it. 
Jim


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## ABA Scirocco (May 30, 2001)

*Re: Air Shrouded Injectors? (Jimmie J.)*

I'm not sure why VW did it, by all reports the difference in fuel economy seems to be marginal at best. But, if you ask me to guess, I'm going to say they did it for emissions. Better atomization means less fuel drop out and more complete combustion, this would reduce emissions especially at idle during warm-up.


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## sdezego (Apr 23, 2004)

*Re: Air Shrouded Injectors? (Jimmie J.)*

"*GTI Head with Air Shroud Injectors*
This head is similar to the GTI head, with the addition of a passage that feeds air in around the injectors for better atomization...."
Source: Volkswagen Water-Cooled, Front Drive Performance Handbook.
Published: 1987 ISBN# 0-87938-268-6 by Greg Raven
Owned this since it hit the shelf and it is still one of the best VW books ever published! Got to see the first insides of G-Lader (G40) back in '87. Most of the guys in there are from the definitive VW era (Drake Performance, Eurorace, oettenger and "Early old school" - TT, Neuspeed and GMP)
Take it FWIW...
Shawn


_Modified by sdezego at 4:31 PM 11-4-2004_


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## ABA Scirocco (May 30, 2001)

*Re: Air Shrouded Injectors? (sdezego)*


_Quote, originally posted by *sdezego* »_"*GTI Head with Air Shroud Injectors*
This head is similar to the GTI head, with the addition of a passage that feeds air in around the injectors for better atomization...."
Source: Volkswagen Water-Cooled, Front Drive Performance Handbook.
Published: 1987 ISBN# 0-87938-268-6 by Greg Raven


I think that's a well established fact so the question now becomes, what do that do for the engine that made it worthwhile for VW to do?


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## sdezego (Apr 23, 2004)

*Re: Air Shrouded Injectors? (ABA Scirocco)*

exactly! For some reason they did crazy stuff around that time for short periods. Like cutting back on the heel of the camshafts, etc.
Then mysteriously they went back to normal a year or two later.
Maybe some R&D engineer needed to justify his research








S


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## druids_laughter (Mar 16, 2004)

*Re: Air Shrouded Injectors? (sdezego)*

Here is what I foound. Make sense...?
This is what VW says:
SOURCE:
05 December 2003
HISTORICAL - 1984 VOLKSWAGEN GTI STARTS SECOND YEAR ON MARKET
ORIGINAL DATE OF THE RELEASE - SEPTEMBER 28, 1983
http://media.vw.com/article_di...=9291
“In addition, for 1984 the GTI engine has air shrouded injector nozzles for improved idling and warm starting.”


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