installing c2 i/c on 930 q's
 

I have some questions on putting a c2 i/c on my 930. I am confused about the whole bov thing. Do I have to get the c2 style 90 elbow with bov? Can I use the stock elbow and put a bov in the aluminum tube after the 90? Unsure what is exactly needed to mount this..

Hi,
The BOV needs to be somewhere between the IC output and the Throttle body. The Vacuum/Boost control line for the BOV needs to come from just below the throttle plate. Here's where I put mine, it is in the front tank of the IC.


http://www.lesgarten.com/pix/porsche/AAA_1147.JPG
http://www.lesgarten.com/pix/porsche/AAA_1151.JPG

That's a VERY large TIAL 50mm. It makes a hell of WHOOSH when it blows.

Hope this helps.

Les

There is nothing set in stone...anything can be done. However, rather than re-invent the wheel as it were, I'd just spend the $45 for the C2 elbow and locate the compressor by-pass where the 965 had it. Keep in mind, there is already a port for the compressor by-pass valve on the front of the C2 intercooler (front as in reaching toward the front of the car), and this port makes for a very short run to the elbow. It makes for a clean install...

Also keep in mind that you should NOT vent to atmosphere with a CIS based engine.

EFI is a different animal...

Not that you need to spend anymore money on this addiction, but I'd think about going with one of the more stout, billet type compressor by-pass valves (CBV, diverter valve, dump valve, BOV, hooter valve, whatever you wish to call it). The 965 factory original plastic Bosch valve will work fine, but after some miles, is prone to wear and failure. I'm running a stealthy looking Hyperboost valve that looks just like the factory part, only it's anodized black billet aluminum. Forge makes a nice one too.

http://www.stratmosphere.com/hyperboost.htm
http://www.stratmosphere.com/forge_valves2.htm

sand_man, thanks for the info your other post made me drool enough to buy one of these guys. I just wasn't sure if I needed to use two divirter valve or one. It looks like one from the installs I have seen, but didn't the 964t use two stock?

les, that is sweet

964t used only one Bosch plastiv BOV of recirculating type. It works OK.

Open air BOV cannot be used on EFI either as long as EFI is using AMM.

Not that I'm aware. Keep in mind that your C2 intercooler is a long neck, so you'll be doing away with that large 930 diverter valve housing that fits between the throttle body and the stock intercooler. And instead replacing it with the small CBV that fits on the CIS elbow. I suppose it's possible that the other valve you might have seen in the 965 engine compartment was related to smog equipment.

Let me know if you need any pictures and I'll snap them.

And I agree, Les, that is SWEET!

Mine opens to atmosphere. What is AMM?

Les

Yea I was hoping to vent to atmosphere...I like the sound. Why can't you with these?

It causes the CIS flapper plate (in the metering housing) to behave erratically.

AMM = Air Mass Meter.

With CIS that flapper plate is basically a AMM :(

ok makes sense now. thanks for replies

Not quite, but it causes CIS to inject fuel that was previously metered up and then dumped overboard, causing an overrich condition.

And how does it do this? It's my understanding that it occurs via the flapper fluctuating. And FWIW, I've heard the inverse of what you just described...the flapper slamming shut and causing a lean condition. That's why I chose to say "erratic"...

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!

Go Ahead, I'm curious about this also. I have a 3.2 Manifold and have my BOV like I previously indicated in pictures in the above postings. Is there a problem with my BOV?
Les

does anyone know the part # for the elbow with bung for divirtor? I am trying to find it on ******** but not having any luck

I bought mine, here:
http://www.eagleday.com/rawagaexpi.html

thanks got it

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.

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.

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!

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.
http://img.photobucket.com/albums/v5...0/DSCF0857.jpg

Here is the naked engine...
http://img.photobucket.com/albums/v5...0/DSCF0860.jpg


And here is the prize awaiting installation.
http://img.photobucket.com/albums/v5...0/DSCF0861.jpg

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

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

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!

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

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.

http://img.photobucket.com/albums/v5...0/DSC02421.jpg

http://img.photobucket.com/albums/v5...0/DSC02420.jpg

Test fitting reducer tube:

http://img.photobucket.com/albums/v5...n/DSC02425.jpg

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!