CIS Cylinder head question

[Peter Jones]

We had some fun and games vacuum testing this head when I had it reco'd.

It took a little while to figure out that there is a gallery that runs across the back of the head that connects the injectors together. I think this is what is refered to as the "AIR SHROUDING" system.

I'm replacing the injectors, seals, insulators and their o rings.

The head had the fitting that connect to this gallery blocked off.

My question is How does this sysytem acually work and what is the gallery connected to? Vacuum?

In this photo you can just make out the gallery between the injector holders.



Here's a picture of the fitting (its the black plastic piece bolted to the head) I could do with a new one of these if anyone has one lying about.
I'm getting all the injector holder parts from germanautoparts.com



Any info would be much appreciated.

Pete

[VR6 STORM]

Hi,
You are right, that is an air shrouded injector head, with an air gallery that runs across the back of the injectors.

I rebuilt an early Mark 2 Golf engine to go in my MK1 GTI many years ago, and the MK2 engine had this drilling and the assocaited plastic part. My earlier DX code engine didnt have this drilling or air rail.

I still have the Golf and bought it with me when we emigrated last year.
This engine is an EV code i.e. solid lifter 1800 MK2 Golf.

I believe that the plastic stub was connected into the pipework upstream of the vaccum booster in the MK2.

I am not sure what VW were trying to do with this system as there is little data that I have found on it, but I think it was to aid in the fuel atomisation from the injector.
It only seems to be found on early CIS 1800cc motors with solid lifters. I dont think the hydraulic 8V CIS heads had them. Dont quote me on that though.

The early motors that dont have this drilling have different injectors. The later motors with this air shroud system have an injector with a little silver cap on the end and an oring.
You can fit early injectors in an air shrouded head, but if I remember correctly you cant fit later air shroud injectors in the earlier head unless you take off the silver cap (it does come off wit a bit of prying)

I ran mine with this plastic fitting both connected to the inlet system and disconnected and capped and never really noticed any difference.

On a lot of 8V heads you see in scrap yards, this feature on the casting isnt drilled out.

I have actually tapped mine out and fitted a blanking plug now as the car has a turbo techncis turbo kit fitted and G60 injectors with aftermarket EFI (an Emerald system). I had to mess about with machining brass injector inserts to get the G60 ones to fit.

I probably have not answered your question for you, but maybe some of this will help? I can scan some piccies of an air shroud injector etc from a UK manual if it helps?

Regards

VR6 Storm

[VR6 STORM]

Ha ha,
have just looked at you cylinder head picture and noticed that it is a hydraulic one! So ignore that comment about hydro heads not having this drilling... duuuh!!

[Peter Jones]

Thnks for that any info helps.

This motor is a GX prefix, the worst of the 1800s It's in my Mk1 hence the plumbing mystery.

K-Jet, Hyd, low compression etc etc. 85 Hp from memory.

When I pulled it down it had one unshrouded and three shrouded injectors like this.



I'm replacing all the seals so I may as well hook it up. I'll make up a new fitting to replace the plastic thingy and see how it goes.

Pete

[VR6 STORM]

Hi, am pretty sure that that air injector in the picture should have an o-ring on the sliver steel part at the bottom. Are you replacing those too?
I dont think you will go too far wrong fitting it up with the air pipe connected to the intake system. Its just not clear from the books wether it goes upstram or downstream of the throttle body.
Why was that GX motor so detuned? The euro motor was good for 112-115 HP in stock trim.

[Peter Jones]

I'm not sure why the GX is so low spec, it's CR is something like 8.5:1 and the cam is only 250 degrees duration.

Yep there should be o rings at both ends of the injector, I've got all of them new ready to go. There's another o ring in the head under each of the plastic insulators.

Pete

[Peter Jones]

That all worked fine.
I made the aluminium plat myself and the brass fitting was from Enzed.

The fitting screws into the plate, by the looks of it, it's 1/4" BSPT

I've got the taps to cut the thread of Enzed could tap a plate for you too.

Pete

[Alex1983]

Hey Pete... I'm not sure if this breaks a record for the longest-ever time to respond to a thread on this forum, but... I don't suppose that offer of a plate and fitting is still open? Obviously I'd be very happy to reimburse you handsomely for your services!