BAE Turbo Install, Part 1 - Page 3

Tim Hancock · 06-14-2006, 06:47 AM

I think the stock BAE setup did not include a BOV, just a wastegate.

Like Goran said, a BOV relieves the accumulated intake air boost pressure between the turbo and the throttle plate after an abrupt throttle closing. Without one in the system, the sudden disruption to the flow of air tends to slow the turbo down (the air it is trying to pump has no where to go) so that when the throttle re-opens, the turbo takes a brief time to re-spool up (hence turbo lag).

In a low boost system installed in an originally non turbo car with relatively high compression ratios, this is probably deemed acceptable.

iamchappy · iamchappy's Garage

Goran there are still a few that are still using the BAE kit in it's original form with the BAE pop valve controlling boost at 5 to 6lbs,
If you are a BAE purest this is the way to go. Now with some of us who tested the waters with the BAE kit and have gone on to build our own systems many$$$$$$$$$$$$$$$$$$$$$ down the road all of the modern day turbo accessories and engine enhancements
are mandatory.

beepbeep · 06-14-2006, 06:56 AM

There are few cars without BOV. Only one I know are early Audi 2.3 turbos with CIS. They boosted only around 0.3 bar so BOV wasn't really needed. But it's intercooler often cracked from pressure spike when people started raising boost to make car go faster.

Tim Hancock · 06-14-2006, 07:22 AM

So the original stock BAE system did include a BOV? If so, sorry for the confusing post above.

patkeefe · 06-14-2006, 07:49 AM

My semi-original BAE kit has a wastegate and a BOV. The BOV is the open type, and it takes a bit of thumb pressure to open it. Until I can put a pressure test on that section of manifold, I can't tell exactly at what pressure it will open.
Pat

tsuter · 06-14-2006, 08:12 AM

Semantics schemantics!!!

Wastegate = Pressure release valve located in the Exhaust collector just before the turbocharger. This is a boost control device. Factory 930 uses a wastegate

BOV - Blow off valve - located in the turbo outlet pipe before the throttle body - opens on Vacuum or differential pressure across the throttle plate - used to vent pressure to atmosphere when shifting/lifting off throttle. BOV is not a boost control device and it vents metered air which can be a critique vs a DV. It is not used by factory 930s.

DV - Diverter Valve - Same as BOV but closed loop in that the vented air goes back to the turbo inlet side. DV is not a boost control device. DVs not BOVs are used in the factory 930.

POP Valve - for a normally aspirated Porsche this is a backfire safety valve located in the airbox. It CANNOT be used on a turbocharger or it must be sealed shut/springloaded at some rate greater than the boost control pressure value. It is for NA cars only.

BAE POP Valve - This is a spring loaded WASTEGATE valve located in the turbo outlet pipe instead of the exhaust collector. This is a boost control valve. It vents metered air so that is the main critique. You would use this or a wastegate. Not both. You can use this and a BOV or DV or neither as they perform a different function.

Tim Hancock · 06-14-2006, 08:18 AM

So the STOCK BAE system came only with a post turbo wastegate and no BOV or DV. Is that correct tsuter?

sammyg2 · 06-14-2006, 08:58 AM

I believe that the BAE kits had either or both. Mine had a wastegate but no BOV.

tsuter · 06-14-2006, 09:07 AM

BAEs had a Wastegate (Exhaust side) or a BAE POP Valve (Turbo outlet side) to control boost. None had BOVs or DVs.
This was 25 years ago. What later owners fabbed on before they were sold...who knows....

patkeefe · 06-14-2006, 10:55 AM

BAE POP Valve - This is a spring loaded WASTEGATE valve located in the turbo outlet pipe instead of the exhaust collector. This is a boost control valve. It vents metered air so that is the main critique. You would use this or a wastegate. Not both. You can use this and a BOV or DV or neither as they perform a different function.

Evidently, this is what I have in addition to the wastegate (the common type found at the turbine inlet piping). My wastegate has connections for control tubing, which I have assumed would come from a boost controller, which I do not have. I thought it odd that I have this type of spring only popoff valve, and a wastegate. Thanks to tsuter for the explanation of this device.

Pat

tsuter · 06-14-2006, 11:22 AM

The only possible reason for you to have both is someone was too lazy to block off the BAE POP Valve when they added a conventional wastegate as they cannot both function together.

It may be that the BAE POP Valve has been welded, or shimmed or a heavy spring added so that it never opens (effectively disabled) thus allowing the conventional wastegate to do the job of boost control.

If the BAE POP valve which came with a 5psi spring has not been modified to disable it, then the wastegate is likely doing nothing.

quattrorunner · quattrorunner's Garage

I was watching Dukes of Hazard with my wife once when a race team was testing their secret race car. They had to stop testing when they broke the "popit valve". I turned to my wife and told her they were idiots and that there was no such thing. Don't tell my wife

patkeefe · 06-14-2006, 12:53 PM

The BAE POP valve will be disappearing soon. Since I don't have a simple spring pressure controlled wastegate, I'll get a good DV and adjustable boost controller to control the wastegate opening, which I believe is how the setup should be ideally.

air-cool-me · 09:48 PM

Quote:

Originally posted by tsuter
The only possible reason for you to have both is someone was too lazy to block off the BAE POP Valve when they added a conventional wastegate as they cannot both function together.

It may be that the BAE POP Valve has been welded, or shimmed or a heavy spring added so that it never opens (effectively disabled) thus allowing the conventional wastegate to do the job of boost control.

If the BAE POP valve which came with a 5psi spring has not been modified to disable it, then the wastegate is likely doing nothing.

It was my kit a while ago... the pop valve should be shimmed shut. Maybe poor mans overboost control, should the wastegate fail. I guess i was too lazy?

"Since I don't have a simple spring pressure controlled wastegate"

the wastegate has a pressure line going to it from off the intake. this pressure pushes on a 4lb spring in the wastegate.. when the pressure overcomes the spring, the wastegate opens.

It has been a long time... but there should be two lines (or fittings) off the wastegate. One goes to the back of the CIS. When the pressure in this line reaches 4lbs(if thats the spring you still have in it) the Wastegate will open.

the other line should not be connected to anything.

If you want more PSI then you would connect a boost controller to the open line and to the pressure line... the controller will leak a few pounds into the other side of the diaphragm of the wastegate... delaying it opening till the difference in pressure is 4lbs again.

so if you leak two pounds into the other side of the wastegate, you would have to make 6psi to have your difference of 4.

if you hook it up as i sent it.... and connect the correct side of the Wastegate to the pressure side of the system you will make 4psi.

good luck!

-nick

patkeefe · 07-24-2006, 07:15 PM

Update of the week...
Finally got almost all of the parts and machine work done. Bottom end is done, cylinders are on. Hopefully I can get this engine together for the weekend, and try to get it put back in. Waiting ona bunch of essential goodies for the turbo...A/F meter, intake temp gauge, cylinder head temp gauge and water injection system.

The original internal thermostat didn't open when I tested it a week or so ago. Hmmm, maybe that's why the thing ran such high oil temps at the track.

Better half helping out. If you want to drive it on the track, you gotta turn the wrenches!

That's a wrap for tonight.

jdm61 · 07-24-2006, 07:21 PM

Quote:

Originally posted by quattrorunner
I was watching Dukes of Hazard with my wife once when a race team was testing their secret race car. They had to stop testing when they broke the "popit valve". I turned to my wife and told her they were idiots and that there was no such thing. Don't tell my wife

No.......they was IDJITS!!!!! lol. Ok guys....newbie here....what is a BAE turbo system and what do it do?

patkeefe · 07-24-2006, 07:44 PM

Briefly, a BAE system is an old style Rajay T04B turbo, which was made as a kit in the early 80's. The goal was to supplement the public demand for turbo 911's, as the rumor was the factory was to quit producing 930's.
The authority on these, both from a historical and operational perspective, is tsuter. Do a search on BAE and tsuer, and you will find lots of info. Most of the posters in this thread have a pretty fair knowledge of the system (excluding myself)
Pat

patkeefe · 08-03-2006, 01:38 PM

Update of the week:
Gotta go finish timing the cams. Waiting for the RSR rocker shaft seals to show up. Laid out the water injection system today; have to plumb it, and finish the install of the brass Carrera oil cooler. I'm going to use the existing flange from the BAE pop valve for the water injector. Need to find a spot to tap the chain cover for the oil drain. Gotta modify the spare airbox cover to snorkle some air from the decklid grille rather than the engine compartment. Need to wire in the A/F meter and make a mount for the gauge. Crap, I have lots to do yet...

sammyg2 · 08-03-2006, 02:01 PM

JDM61, The search button is your friend

just kidding.

Here's the "ultimate" thread on bae turbos. 911SC Turbo

It goes back a couple of years and it is fun to watch the projects go from an idea to finished product.
That is, if you have the patience to read the entire thread. It's long but entertaining if you like that sort of thing.

patkeefe · 08-03-2006, 06:09 PM

Where did you turbo guys route the oil return? I have Carrera tensioners, so I can't use the cover I got with my BAE stuff. I suppose the way to go is to weld a stub on the left chain cover, such that I can drill and tap it. How did the 930's return oil to the sump?