930 Intake Hose Routing Comparisons

[donbecker1234]

I'm starting to complete my refurbishment of the intake, mass air flow meter and BPV assemblies and want to pin down just how to route the hoses. I'm also planning to cut new hoses out of silicone instead of reusing the old hoses.





I have great reference pictures of everything before I started taking things apart and although the car seemed to run fine, I'm new to these cars and have my doubts everything is routed the best way.

The car is an 87 M491, with 78 930 (930/63 / Cali) motor in it. My EGR, air pump and blow-off switching valve are long gone.

Below we have hose routing diagrams for the 1978 930, along with comparisons of differences between them:

We'll use the Europe diagram as a base:


Looking at the USA/Japan diagram I see the following differences:
- EGR valve (red): Missing on Europe
- Aux Air valve (orange): Missing on Europe, Aux Air Regulator goes straight to intake, second port on intercooler is blocked off
- Front Thermo Valve (purple): Missing on Europe, line from intake valve runs straight to distributor vac advance
- Check Valve (brown): Missing on USA/Japan, line from BPV runs directly to blow off switching valve


Looking at the Cali diagram, I see the following differences from USA/Japan:
- Cut-Off valve (teal): Added to Cali, T'ing off the WUR, front thermo valve and blow off switching valve lines. There is also a line from Cut-Off valve to second port on distributor advance
- Rear Thermo Valve (green): Added to Cali, T'ing off Vac limiter and connecting to a third port on the Aux Air Valve



Here are the questions I am trying to find answers to. I'd like to simplify if possible as these parts are likely original. I will need to pass a tailpipe smog test but I do not plan to need to pass a visual inspection, so as long as changes don't impact tailpipe readings or driveability/functionality I'd like to make them.

1. Rear Thermo-valve (green): when I pulled my engine, the vac hoses on my engine were connected but the electrical plug was disconnected. Could I just remove the rear thermo-valve and plug the ports the hoses go to?

2. Aux Air Valve (orange): this doesn't exist on the Europe diagram. Could I remove this and match Europe by plugging the second intercooler port and routing the Aux Air Reg directly to the Intake?

3. Front Thermo-valve (purple): this doesn't exist on the Europe diagram. Could I remove this?

4. Cut-off valve (teal): this doesn't exist on the USA/Japan diagram. Could I remove this? Will there be any issue just plugging the second port on the distributor vac?

[donbecker1234]

Cross posted here

If anyone has any details on this it'd be great as I'm getting close to a decision point to get this back together and back on the road.

[1979-930]

Are you going to upgrade the inter-cooler? If you get a long neck version from Turbo Kraft it's a bolt on with the new by-pass valve. With that you get rid of everything, but the overboost switch, in pic #2 and the secondary air by-pass in pic 3 can go with either set up. It was for raising idle when using the old York AC compressors. Not needed with or without AC if using a modern compressor.

If not you can set it up like the Europe configuration without the Smog pump and associated vacuum lines. A oil pan drain plug fits the thread in the back of the intake to remove the vacuum line connection.

The other air by-pass shuttle valve, in Pic 2, is for decel air enrichment. If you loose that you get the pops and gurgles when shifting and on decel. You can keep it or not. Personal choice there.

[donbecker1234]

Originally Posted by 1979-930

Are you going to upgrade the inter-cooler? If you get a long neck version from Turbo Kraft it's a bolt on with the new by-pass valve. With that you get rid of everything, but the overboost switch, in pic #2 and the secondary air by-pass in pic 3 can go with either set up. It was for raising idle when using the old York AC compressors. Not needed with or without AC if using a modern compressor.

If not you can set it up like the Europe configuration without the Smog pump and associated vacuum lines. A oil pan drain plug fits the thread in the back of the intake to remove the vacuum line connection.

The other air by-pass shuttle valve, in Pic 2, is for decel air enrichment. If you loose that you get the pops and gurgles when shifting and on decel. You can keep it or not. Personal choice there.

I'm not in a position to purchase the long neck yet unfortunately.

"If not you can set it up like the Europe configuration"

Can you be more specific, or do you mean to just match the Europe diagram?

Can you explain why the "Control Valve" is in the Europe (#13) and Cali (#9) but not in the US diagram?

Can you help me understand why the Aux air valve and rear thermovalve is missing from the Europe diagram? Is that just related to the ignition timing differences?

[1979-930]

Originally Posted by donbecker1234

I'm not in a position to purchase the long neck yet unfortunately.

"If not you can set it up like the Europe configuration"

Can you be more specific, or do you mean to just match the Europe diagram? Yes, Match the diagram. You dont have or need components #11,12,13,14. #7 is optional.

Can you explain why the "Control Valve" is in the Europe (#13) and Cali (#9) but not in the US diagram? They look the same but function differently for emissions requirements. You don't have a smog pump, so it's not needed.

Can you help me understand why the Aux air valve and rear thermovalve is missing from the Europe diagram? Is that just related to the ignition timing differences? Not timing but additional air for emissions. They needed to keep the intake lean so the thermal reactors stayed hot.

The cars run just fine on a Euro set up. All the other systems lean out the engine and add air for emissions

[donbecker1234]

Originally Posted by 1979-930

The cars run just fine on a Euro set up. All the other systems lean out the engine and add air for emissions

Thanks so much for the detailed response, much clearer!

[donbecker1234]

Would it be correct to route the second port on the distributor vac canister to the BPV (green line)?

I suspect I have the Cali 79 930 dizzy:

"Cars in California version are equipped with a distributor having a double action pressure box.

At idle speed the intake vacuum produces ignition control toward retard, which is eliminated again when the throttle is open just slightly.

The charge air pressure is used for full throttle retard ignition control, to avoid coming into the range of excessive advance ignition at full throttle with the ignition timing which is 5 degrees earlier than the USA version"

Thanks!

[1979-930]

Originally Posted by donbecker1234

Would it be correct to route the second port on the distributor vac canister to the BPV (green line)?

I suspect I have the Cali 79 930 dizzy:

"Cars in California version are equipped with a distributor having a double action pressure box.

At idle speed the intake vacuum produces ignition control toward retard, which is eliminated again when the throttle is open just slightly.

The charge air pressure is used for full throttle retard ignition control, to avoid coming into the range of excessive advance ignition at full throttle with the ignition timing which is 5 degrees earlier than the USA version"

Thanks!

I forgot about that.
I'm not 100% on that routing working. This thread is about distributor options. It may have an updated vacuum routing info. https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/500986-ultimate-930-distributor-advance-retard-timing-turbo-lag-msd-mod-thread.html
I don't remember my car using the cut off valve. But it may be necessary with the dual vacuum distributor

I ditched the whole thing, locked the distributor and install a programmable MSD with boost retard. You need to understand timing and boost enough to program your own timing curve. It's really not that difficult.
The plus is you can have 32* or more advance at cruise and the MAP sensor will pull it all out on boost onset at a programmed rate. The car runs so nice with good ignition timing.

[donbecker1234]

Originally Posted by 1979-930

I forgot about that.
I'm not 100% on that routing working. This thread is about distributor options. It may have an updated vacuum routing info. https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/500986-ultimate-930-distributor-advance-retard-timing-turbo-lag-msd-mod-thread.html
I don't remember my car using the cut off valve. But it may be necessary with the dual vacuum distributor

I ditched the whole thing, locked the distributor and install a programmable MSD with boost retard. You need to understand timing and boost enough to program your own timing curve. It's really not that difficult.
The plus is you can have 32* or more advance at cruise and the MAP sensor will pull it all out on boost onset at a programmed rate. The car runs so nice with good ignition timing.

Here is the text relating to the "5 degrees earlier":

Ignition angle must be 31 degrees +/- 4 degrees BTDC at engine
speed of 4000 rpm (vacuum hose disconnected, high pressure hose can remain connected as long as the test is made without engine load)

Compare to the US timing:

Ignition angle must be 26 degrees +/- 4 degrees BTDC at engine speed of 4000 rpm (vacuum hose disconnected)

Let me know if my conclusion here doesn't make sense, but I think I can just set timing to match US (non-Cali) specs and just cap the second port on the dizzy.

[donbecker1234]

Originally Posted by 1979-930

I forgot about that.
I'm not 100% on that routing working. This thread is about distributor options. It may have an updated vacuum routing info. https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/500986-ultimate-930-distributor-advance-retard-timing-turbo-lag-msd-mod-thread.html
I don't remember my car using the cut off valve. But it may be necessary with the dual vacuum distributor

I ditched the whole thing, locked the distributor and install a programmable MSD with boost retard. You need to understand timing and boost enough to program your own timing curve. It's really not that difficult.
The plus is you can have 32* or more advance at cruise and the MAP sensor will pull it all out on boost onset at a programmed rate. The car runs so nice with good ignition timing.

Thanks for the link to the 930 distributor thread.

Regarding the thermovalve in the red box in the diagram above, looks like I can eliminate that as well:

"The USA model 1987 911 turbo has a small mechanical thermal valve in the vacuum advance hose. It's an emission device.
It blocks the vacuum advance line from reaching the distributer's vacuum advance pot until engine heat soaks into it and opens it allowing vacuum advance to work.

Exhaust temperature is hotter when ignition timing is retarded because the very last of the gas mixture in the combustion chambers is still burning or just finished burning when the exhaust valve opens.

This thermovalve's purpose is to keep ignition timing in the USA cars slightly retarded after a cold start so the catalytic converter heats up faster.
Getting the CAT up to operating temp faster lowered exhaust emissions so they could sell these cars in the USA again starting in 1986."

[levdeb]

Originally Posted by 1979-930

The other air by-pass shuttle valve, in Pic 2, is for decel air enrichment. If you loose that you get the pops and gurgles when shifting and on decel. You can keep it or not. Personal choice there.

Hey Derrick! I sent you a PM a couple weeks ago. Wondering which valve you are talking about (and which is Pic 2)? Just cleaned up my engine bay, and would love to get a few more pops out of her just to make the wife ask (every single time) "Is that normal??" and "Is that a good sound??"

Thanks for any insight!