Quick question re vacuum lines.
12-08-2010, 08:12 PM
#1
Track Day
Thread Starter
Quick question re vacuum lines.
Hi folks,
I have my intake manifold off at the moment and I think I may have found a wrongly connected vac line.
On my car, (89, RHD, UK, non cat, auto, S4) the small black vac line from the air diverter valve is connected to the 7 way rubber vac manifold.
The clear vac line from the very bottom of the throttle body is not connected anywhere, it is just capped off up at the bulkhead.
Is this correct?
I've spent hours trawling the relevant sites (I'm now seeing vac lines in my sleep) and most seem to suggest that the vac line at the air diverter line should be connected to the bottom of the throttle body, although on at least one site, I have seen the vac line from the bottom of the throttle body, described as the vac test line, which would suggest that it could just be capped off.
Dazed and confused,
Mark.
I have my intake manifold off at the moment and I think I may have found a wrongly connected vac line.
On my car, (89, RHD, UK, non cat, auto, S4) the small black vac line from the air diverter valve is connected to the 7 way rubber vac manifold.
The clear vac line from the very bottom of the throttle body is not connected anywhere, it is just capped off up at the bulkhead.
Is this correct?
I've spent hours trawling the relevant sites (I'm now seeing vac lines in my sleep) and most seem to suggest that the vac line at the air diverter line should be connected to the bottom of the throttle body, although on at least one site, I have seen the vac line from the bottom of the throttle body, described as the vac test line, which would suggest that it could just be capped off.
Dazed and confused,
Mark.
12-08-2010, 08:23 PM
#2
Rennlist Member
The air diverter is indeeed fed directly from under the the throttle body.
The throttle body has 3 vacuum ports (4 in some early S4 models years in California). The 2 upper ports face opposite direction..........the one to the MAF feeds the vacuum system for the splitter and the fuel dampners, regulator and auto transmission. The forward facing upper port is directly to the carbon cannister system and the lower port is for the air diverter.
These ports are controlled by the opening of the throttle plate.
The throttle body has 3 vacuum ports (4 in some early S4 models years in California). The 2 upper ports face opposite direction..........the one to the MAF feeds the vacuum system for the splitter and the fuel dampners, regulator and auto transmission. The forward facing upper port is directly to the carbon cannister system and the lower port is for the air diverter.
These ports are controlled by the opening of the throttle plate.
Last edited by the flyin' scotsman; 12-08-2010 at 08:31 PM. Reason: more info
12-08-2010, 08:32 PM
#3
Team Owner
you will find more info here look for the intake refresh lots of detailed pictures, Thanks Dwayne!
http://www.dwaynesgarage.norcal928.org/
http://www.dwaynesgarage.norcal928.org/
12-08-2010, 08:54 PM
#5
Rennlist Member
The air pump in a non-cat car feeds the exhaust valves in the cylinder heads.
Last edited by the flyin' scotsman; 12-08-2010 at 08:56 PM. Reason: adding pic
12-08-2010, 10:40 PM
#7
Team Owner
Thanks Malcolm for that bit of wisdom,
I have never seen that before
I have never seen that before
Trending Topics
12-08-2010, 10:47 PM
#8
Rennlist Member
No worries Stefan........glad to help, its a long winter.
For those who are curious and want to read more the picture is from the '87 MY Service Information Technik WKD 493 421 available on Jims CDs. The '87 was the first year for the 5.0l engine that was the std engine config for all 928s until it was 'tweeked' for the GT and GTS models.
Great reading to somewhat understand the evolution of the 928.
Stan, I remembered reading it when researching for the high idle issue epic for Steve in Wales and wanted to have clear understanding of the throttle body, its operation and how it changed through the years..........now if i can just recall where I put that million dollars
For those who are curious and want to read more the picture is from the '87 MY Service Information Technik WKD 493 421 available on Jims CDs. The '87 was the first year for the 5.0l engine that was the std engine config for all 928s until it was 'tweeked' for the GT and GTS models.
Great reading to somewhat understand the evolution of the 928.
Stan, I remembered reading it when researching for the high idle issue epic for Steve in Wales and wanted to have clear understanding of the throttle body, its operation and how it changed through the years..........now if i can just recall where I put that million dollars
12-09-2010, 12:05 AM
#9
Nordschleife Master
Hi Mark,
Yes, its just capped off. See this thread for more info
https://rennlist.com/forums/928-foru...ttle-body.html
Hilton.
Yes, its just capped off. See this thread for more info
https://rennlist.com/forums/928-foru...ttle-body.html
Hilton.
Hi folks,
I have my intake manifold off at the moment and I think I may have found a wrongly connected vac line.
On my car, (89, RHD, UK, non cat, auto, S4) the small black vac line from the air diverter valve is connected to the 7 way rubber vac manifold.
The clear vac line from the very bottom of the throttle body is not connected anywhere, it is just capped off up at the bulkhead.
Is this correct?
I've spent hours trawling the relevant sites (I'm now seeing vac lines in my sleep) and most seem to suggest that the vac line at the air diverter line should be connected to the bottom of the throttle body, although on at least one site, I have seen the vac line from the bottom of the throttle body, described as the vac test line, which would suggest that it could just be capped off.
Dazed and confused,
Mark.
I have my intake manifold off at the moment and I think I may have found a wrongly connected vac line.
On my car, (89, RHD, UK, non cat, auto, S4) the small black vac line from the air diverter valve is connected to the 7 way rubber vac manifold.
The clear vac line from the very bottom of the throttle body is not connected anywhere, it is just capped off up at the bulkhead.
Is this correct?
I've spent hours trawling the relevant sites (I'm now seeing vac lines in my sleep) and most seem to suggest that the vac line at the air diverter line should be connected to the bottom of the throttle body, although on at least one site, I have seen the vac line from the bottom of the throttle body, described as the vac test line, which would suggest that it could just be capped off.
Dazed and confused,
Mark.
12-09-2010, 12:42 AM
#10
Rennlist Member
Hilton..........if that is factory how does it work?
The vacuum port on the throttle body that faces toward the MAF and is the vacuum source for the, splitter, fuel dampners and regulator is supplying vacuum on all engine running conditions due to the position of the throttle plate. The other upper and lower ports are sealed from vacuum at idle but as soon as the throttle plate is off idle vacuum is then generated in all throttle body ports and lines.
When the lower port is connected directly to the air diverter theres no vacuum at idle and all air from the air pump is directed to the cats or the cylinder heads in a non-cat car. Once off idle the vacuum then switches the diverter and the air is sent to the air filter box.
If the air diverter is connected to the splitter which is a constant vacuum source I dont see how it operates unless the configuration is country specific?
The vacuum port on the throttle body that faces toward the MAF and is the vacuum source for the, splitter, fuel dampners and regulator is supplying vacuum on all engine running conditions due to the position of the throttle plate. The other upper and lower ports are sealed from vacuum at idle but as soon as the throttle plate is off idle vacuum is then generated in all throttle body ports and lines.
When the lower port is connected directly to the air diverter theres no vacuum at idle and all air from the air pump is directed to the cats or the cylinder heads in a non-cat car. Once off idle the vacuum then switches the diverter and the air is sent to the air filter box.
If the air diverter is connected to the splitter which is a constant vacuum source I dont see how it operates unless the configuration is country specific?
12-09-2010, 04:27 AM
#11
Nordschleife Master
Malcolm - no idea on typical operation for countries with emissions equipment.
However on a sample of 4 manual non-cat S4's (all RHD from the UK, from '87-89) the arrangement is as follows (three of them with undisturbed intakes since factory):
On top of throttle body pointing aft - 5 way splitter connecting: fuel pressure regulator, 2 fuel pressure dampners, air pump diverter valve
On top of throttle body pointing forwards - single line to charcoal canister valve (vacuum off-idle only)
Underside of throttle body - vacuum test line capped with red rubber cap, which comes up the right-rear of the engine by cylinder 4.
I suspect that since the airpump does nothing other than dilute emissions, the factory didn't care whether it was in operation at all times or not?
I'm still at odds to understand why they even bothered fitting the air pump to non-cat cars at all. I've removed the complete airpump assembly on two of my S4's, including the manifold that links all the ports on the heads to the pump (major PITA job to remove the pipe that joins the banks over the top of the bellhousing requires small hands and a small pipe cutter several times).
However on a sample of 4 manual non-cat S4's (all RHD from the UK, from '87-89) the arrangement is as follows (three of them with undisturbed intakes since factory):
On top of throttle body pointing aft - 5 way splitter connecting: fuel pressure regulator, 2 fuel pressure dampners, air pump diverter valve
On top of throttle body pointing forwards - single line to charcoal canister valve (vacuum off-idle only)
Underside of throttle body - vacuum test line capped with red rubber cap, which comes up the right-rear of the engine by cylinder 4.
I suspect that since the airpump does nothing other than dilute emissions, the factory didn't care whether it was in operation at all times or not?
I'm still at odds to understand why they even bothered fitting the air pump to non-cat cars at all. I've removed the complete airpump assembly on two of my S4's, including the manifold that links all the ports on the heads to the pump (major PITA job to remove the pipe that joins the banks over the top of the bellhousing requires small hands and a small pipe cutter several times).
Hilton..........if that is factory how does it work?
The vacuum port on the throttle body that faces toward the MAF and is the vacuum source for the, splitter, fuel dampners and regulator is supplying vacuum on all engine running conditions due to the position of the throttle plate. The other upper and lower ports are sealed from vacuum at idle but as soon as the throttle plate is off idle vacuum is then generated in all throttle body ports and lines.
When the lower port is connected directly to the air diverter theres no vacuum at idle and all air from the air pump is directed to the cats or the cylinder heads in a non-cat car. Once off idle the vacuum then switches the diverter and the air is sent to the air filter box.
If the air diverter is connected to the splitter which is a constant vacuum source I dont see how it operates unless the configuration is country specific?
The vacuum port on the throttle body that faces toward the MAF and is the vacuum source for the, splitter, fuel dampners and regulator is supplying vacuum on all engine running conditions due to the position of the throttle plate. The other upper and lower ports are sealed from vacuum at idle but as soon as the throttle plate is off idle vacuum is then generated in all throttle body ports and lines.
When the lower port is connected directly to the air diverter theres no vacuum at idle and all air from the air pump is directed to the cats or the cylinder heads in a non-cat car. Once off idle the vacuum then switches the diverter and the air is sent to the air filter box.
If the air diverter is connected to the splitter which is a constant vacuum source I dont see how it operates unless the configuration is country specific?
12-09-2010, 10:09 AM
#12
Rennlist Member
Then theres the UK auto cars that are configed same as North American cars.
I also have removed the air pump and all associated plumbing and yes its a pain.
