installing c2 i/c on 930 q's

[mdurbahn]

So the 964 i/c slides directly on the throttle body using the same o rings as the ol stock intercooler? Doesn't seem like as tight of a fit as I thought it should be..

[sand_man]

Originally Posted by mdurbahn

So the 964 i/c slides directly on the throttle body using the same o rings as the ol stock intercooler? Doesn't seem like as tight of a fit as I thought it should be..

Yes. I'd advise getting a new o-ring for the throttle body. As you work on your fitment, try to keep an eye on how the intercooler fits over the throttle body. There is lots of room for movement in this area and it's very easy to miss a snug fit.

[sand_man]

One other piece of advice I can offer: I used a some folded up pieces of card board (probably the box from a beer 12 pack) over the top of the fan shrouding to help support the intercooler while I measured for my brackets and made adjustments. This also provided some protection for the cooling fins of the intercooler.

[mdurbahn]

Thanks, I will put up some pictures of my progress when I find the camera...I made a sweet i/c hose lastnight

[sand_man]

Originally Posted by mdurbahn

Thanks, I will put up some pictures of my progress when I find the camera...I made a sweet i/c hose lastnight

KILLER! Can't wait to see it!

[mdurbahn]

Pic Update

Here is the tube from the turbo to intercooler, I made it using carbon fiber and foam backer rod for a mold. I still need to trim to end so it fits right and looks smooth.


Here is the naked engine...



And here is the prize awaiting installation.


Still need to purchase a c2 bpv and make the tube that fills the void of the old bypass valve.

[beepbeep]

Originally Posted by sand_man

BTW Goran, it's hard to tell from this whole internet thing, but I didn't mean my tone to have a defensive flair. I realize you know these fuel systems VERY well...in addition to turbo charging as a whole, and I respect your knowledge. And I do understand what you are describing. I'm merely pointing out what one of the more experienced shops in my neck of the woods explained when I was describing my plans to change intercoolers and run a different by-pass valve. Your explanation could very well be right one...

Cheers!

Hello!

Didn't follow the thread for a while. I did a mental misstake when I wrote the explanation. I'll try to explain what happends when fitting open BOV more correctly further on. First, a naming convention check.


BOV- Blow Off Valve (in my textbook). A thing that releases the air trapped between turbo and throttle that was slapped shut after boost run. There are two main designs.
1. Recirculating one: It re-routes air back inte system. Between CIS/AMM/whatever and turbo. Fitted to ALL OEM cars by factory (930 included).
2. Open one: same as above but it doesn't return the air into system but just releases it, making a whistling sound. Used by youngsters in belief it will make their cars go faster. NEVER used on OEM cars, sometimes used on racing cars.

So, what happends when you run you car to full boost and then instantly step off the accellerator?

1. Turbo is spinning upwards 150000 RPM and boosting. It's shaft has certain inertia.

2. You step off the throttle, shutting air access to engine. Turbo still spins at 150000 RPM.

3. Shaft inertia keeps turbo pumping the air against closed throttle. If nothing happends, impeller cavitation (=stall) occures and turbo eventually slows down. Sometimes a lot. It's blade tips are made of aluminium and cavitation might damage them. Thus we have BOV that opens up this tract and lets air escape.

Now to the interestion point. Let's check OEM recirculating BOV:

Air is drawn trough CIS flapper into turbo. The more air is drawn, the more fuel is injected. You step off the throttle, air gets re-routed into turbo intake. BUT, this is after CIS flapper. So net result is that flapper doesn't draw any more air. Existing air is only whirled around downstream from flapper...everything is nice and easy.

Now you want to be a ricer and install fancy green-eloxated open BOV with Japanese letters on it to make funny sounds while shifting. What happends? Well, it will release the air packed by turbo slowing down into athmosphere. Unfortunately, turbo will draw all that "funny sounds"-air trough the flapper. Flapper believes all that air is being drawn into engine instead of being used for noise. So CIS injects corresponding amount of fuel into non-assuming engine which has it's throttle closed and draws almost no air at all. So engine suddenly has almost no air and heaps of fuel injected into it and goes overrich, burping, farting and burning out the things. It might also produce flames....which some people fancy (funny noises + flames = COOL!).

In reality, there are no gains with open BOV except for noise. In worst case, it will use more fuel, burn out things and make turbo slow down more.

It WILL work without going rich on cars using speed/density systems though as they don't have any AMM or flapper between turbo and filter assembly. So it's possible (but quite cheesy, IMHO) to use open BOV on EFI cars fed by MAP-sensor. Not so on CIS.

Check out which BOV Audi used on their IMSA-cars:

http://forums.pelicanparts.com/uploads8/1989+audi+200+quattro+eng31159472874.jpg

[sand_man]

Looks fantastic, mdurbahn! I loves me a "naked engine"!!! Your boost pipe is certainly high-tech! You are well on your way!

Thanks for explanation, Goran!

[jay71]

Nice job on that tube, Matt! I'd like to see the car when you get everything back together.

[mdurbahn]

thanks jay, I want to check out yours too. I am making the other reducer tube right now..had to make that one out of carbon fiber too because I dont have a welder

It's not dry in the pics so it doesn't look as good as the first pipe yet.

[mdurbahn]

Test fitting reducer tube:



Have a couple more questions now.

1. do you need to take the a/c condensor out of the tail?
2. what's the easy way to take the rear wiper assembly out?

I don't want to try to close the lid until I know I won't have any clearence issues..

thanks!