running lean of stoich - lean is not the enemy, stoich is!
02-10-2007, 05:49 PM
#91
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Originally Posted by mark kibort
i think the tank venting port is actually on the vacuum side of the manifold to have those vapors injected to the intake, using a little valve that is controlled by vacuum on the vacuum side of the throttle plate.
02-10-2007, 07:49 PM
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Originally Posted by worf928
Below is an annotated picture of an S4+ TB. The location of the tank vapor port is very close to the plate and seems to correspond with the description of the 'timed port' posted previously.
02-10-2007, 07:54 PM
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Originally Posted by mark kibort
you must have forgotten , PV/NRT.
also, the air mass moves to differential pressure. the pressure will never be the same all the way through the system it will be different levels of gradients based on location and speeds of the air based on diameters. its not as simple as you think. the throttle plate as it starts to open, has a very fast rate of flow, for which several dynamics are happening. the venturi effect. the port location is key the fact that on the 84s US, there is a port that drives the timing advance and a port or a few ports on the other side of the throttle plate that drives the fuel regs and other idle vacuum driven systems.
Mk
also, the air mass moves to differential pressure. the pressure will never be the same all the way through the system it will be different levels of gradients based on location and speeds of the air based on diameters. its not as simple as you think. the throttle plate as it starts to open, has a very fast rate of flow, for which several dynamics are happening. the venturi effect. the port location is key the fact that on the 84s US, there is a port that drives the timing advance and a port or a few ports on the other side of the throttle plate that drives the fuel regs and other idle vacuum driven systems.
Mk
You quote a basic physics formula as your reference and then go on to argue using a function that isn't even included in the formual.
Unless I've had a stroke and forgotten my basic undergrad physics PV=nRt does not even contemplate speed........ In fact, P= pressure, V=volume t=temperature, n = amount of the substance in mols, and R the gas constant in cubic meters.
The only difference in pressure (vacuum) that you will see along the intake tract is minor and is relate to the compressibility of the gas, because the motivating force is pulsatile. The pressure threshold toward which this constant-pressure-column of air is moving, is the intake valve.
You will be right when you understand that the fluid speed is inversely proportional the cross sectional area of the flow channel but the pressure remains constant. Pressure is only a function ofy the smallest cross sectional portion of the channel (throttle), from that point (the throttle) to the terminal threshold of the channel (intake valve). This is exclusive of minor mechanical losses, one of which I mentioned above.
Last edited by BrianG; 02-10-2007 at 08:10 PM.
02-10-2007, 11:09 PM
#94
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Originally Posted by BrianG
Dave, can you post an annotated picture of the '85-'86 throttle body vacuum ports?
02-11-2007, 01:17 AM
#95
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Im glad your entertained 
When you see that the differential pressure through out the system is not constant, you get the fact that especially at or near the throttle body, the pressure under part throttle condtions at or around the throttle plate is near ambient and will not drive any vacuum driven devices such as the vacuum on the RRFRs. even more so, is the very small vacuum ports drving the vacuum retard. those ports are even closer to the throttle plate, so when it opens the plate actually passes the ports.
There is realtively no difference in the throttles of the US, 85US and the S4. they all have this port, and you can see it in the first picture about 1/2 to 1" above (on the vacuum side of the throttle plate) the throttle plate.
when i get a pressure measurement on this port, and also one on the main intake manifold port that drives the vacuum booster, ill report back.
Mk
When you see that the differential pressure through out the system is not constant, you get the fact that especially at or near the throttle body, the pressure under part throttle condtions at or around the throttle plate is near ambient and will not drive any vacuum driven devices such as the vacuum on the RRFRs. even more so, is the very small vacuum ports drving the vacuum retard. those ports are even closer to the throttle plate, so when it opens the plate actually passes the ports.
There is realtively no difference in the throttles of the US, 85US and the S4. they all have this port, and you can see it in the first picture about 1/2 to 1" above (on the vacuum side of the throttle plate) the throttle plate.
when i get a pressure measurement on this port, and also one on the main intake manifold port that drives the vacuum booster, ill report back.
Mk
Originally Posted by BrianG
Well Mark... if nothing else your arguement style is entertaining!
02-11-2007, 01:28 AM
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you know, i dont know for sure either. but you could be right here. I did a test once without the microswitch, but it was also with the O2 sensor disconnected, but still powered and giving a signal to the ARM 1. that just showed that as you got to higher rpms, the mixture would go dangerously lean (near 14.7:1) and then beyond. I never did a test with just the microswitch disconnected.
I cant remember exactly, and i dont have any notes from that test.
mk
I cant remember exactly, and i dont have any notes from that test.
mk
Originally Posted by worf928
The 'hunting' behavior you describe is I thinkapplicable for idle and steady-throttle application only. I have hooked up an ARM 1 to the 02 sensor output and seen that the hunting only occurs at idle or steady-throttle. The hunting stops if the throttle is moving. I have not however observed the behavior carefully enough to be certain of this. Nor have I disabled my WOT switch to determine what it would look like at WOT with no WOT signal.
But, I am certain that the hunting behavior is periodic and increases in
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But, I am certain that the hunting behavior is periodic and increases in
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02-11-2007, 02:11 PM
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Below is a picture of the 85/86 32v throttle body. I've labeled the three vacuum ports. The largest is the port to the air pump. The smallest is the port for the tank venting valve. That port is in-line with the plane of the throttle plate when the plate is in the idle (closed) state. In this picture I held open the plate a tiny amount so that the pinhole-sized port is visible.
02-11-2007, 02:42 PM
#98
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same as the S4 and same as the early cars as i posted. the fuel reg vacuum port is in the same position.
so, now, lets see what the vacuum is on the port at idle vs off trottle compared to manifold vacuum.
again, the main controller of fuel pressure is the spring in the fuel regulator.
I think you can think of it like this;
if there is 55psi fuel pressure in the line, then there is 55psi acting on the fue reg's diaphram. that spring has to have 55psi of pressure acting against it. since the pump is putting near 100psi, the excess fuel is always running back to the fuel tank. if you have near .5 bar of vacuum 16 to 17psi of vacuum at idle, theoretically, that could pull back the pressure by that same amout. (ie near 40psi) But, after idle and at part throttle, this could reduce the pressure to 45psi. However, the pressrue im seeing on the gauge is 55psi, so that incorporates the 10psi part throttle. BUT, since when i remove the line entirely, and it doesnt change, this is the difference of using a vacuum port on the manifold vs near the throttle plate by 1" when its closed, you get vacuum, when it is cracked that vacuum is reduced substantially, and not equal to the rest of the intake manifold and thats the main point here.
when i put the sunx sensor on the engine today, ill show the values.
Mk
so, now, lets see what the vacuum is on the port at idle vs off trottle compared to manifold vacuum.
again, the main controller of fuel pressure is the spring in the fuel regulator.
I think you can think of it like this;
if there is 55psi fuel pressure in the line, then there is 55psi acting on the fue reg's diaphram. that spring has to have 55psi of pressure acting against it. since the pump is putting near 100psi, the excess fuel is always running back to the fuel tank. if you have near .5 bar of vacuum 16 to 17psi of vacuum at idle, theoretically, that could pull back the pressure by that same amout. (ie near 40psi) But, after idle and at part throttle, this could reduce the pressure to 45psi. However, the pressrue im seeing on the gauge is 55psi, so that incorporates the 10psi part throttle. BUT, since when i remove the line entirely, and it doesnt change, this is the difference of using a vacuum port on the manifold vs near the throttle plate by 1" when its closed, you get vacuum, when it is cracked that vacuum is reduced substantially, and not equal to the rest of the intake manifold and thats the main point here.
when i put the sunx sensor on the engine today, ill show the values.
Mk
Originally Posted by worf928
Below is a picture of the 85/86 32v throttle body. I've labeled the three vacuum ports. The largest is the port to the air pump. The smallest is the port for the tank venting valve. That port is in-line with the plane of the throttle plate when the plate is in the idle (closed) state. In this picture I held open the plate a tiny amount so that the pinhole-sized port is visible.
02-11-2007, 05:31 PM
#99
Here's just some of the information I had at hand at my desk.
From the Bosch Automotive Handbook:
http://img256.imageshack.us/img256/4...ulator1rp2.jpg
From the Bosch book "Emission Control for Spark-Ignition Engines-Technical Instruction":
http://img256.imageshack.us/img256/5...ulator2ya4.jpg
http://img256.imageshack.us/img256/4...ulator3ca7.jpg
From the Bosch book "Gasoline Fuel-Injection System L-Jetronic-Technical Instruction":
http://img256.imageshack.us/img256/3...ulator4py4.jpg
http://img256.imageshack.us/img256/7...ulator5kl2.jpg
From a Bosch technical instruction training manual on electronically controlled fuel injection:
http://img256.imageshack.us/img256/9...ulator6zv6.jpg
From the 928 section of Porsche's Electronic Ignition and Injection System manual:
http://img256.imageshack.us/img256/3...ulator7ni1.jpg
From Porsche's manual "928 Air Flow Controlled Fuel Injection-Service Information":
http://img256.imageshack.us/img256/8...ulator8je3.jpg
From Porsche's Service Training Manual "Fuel and Ignition System 928S4 and 928GT":
http://img256.imageshack.us/img256/3...ulator9wo8.jpg
From data logging of an S4. (Fuel pressure scale is inverted):
http://img256.imageshack.us/img256/9...lator10hc2.jpg
http://img256.imageshack.us/img256/3...lator11sv2.jpg
From Mark:
Kind of interesting how all of the above information regarding how the system works is in agreement... with one exception. 
From the Bosch Automotive Handbook:
http://img256.imageshack.us/img256/4...ulator1rp2.jpg
From the Bosch book "Emission Control for Spark-Ignition Engines-Technical Instruction":
http://img256.imageshack.us/img256/5...ulator2ya4.jpg
http://img256.imageshack.us/img256/4...ulator3ca7.jpg
From the Bosch book "Gasoline Fuel-Injection System L-Jetronic-Technical Instruction":
http://img256.imageshack.us/img256/3...ulator4py4.jpg
http://img256.imageshack.us/img256/7...ulator5kl2.jpg
From a Bosch technical instruction training manual on electronically controlled fuel injection:
http://img256.imageshack.us/img256/9...ulator6zv6.jpg
From the 928 section of Porsche's Electronic Ignition and Injection System manual:
http://img256.imageshack.us/img256/3...ulator7ni1.jpg
From Porsche's manual "928 Air Flow Controlled Fuel Injection-Service Information":
http://img256.imageshack.us/img256/8...ulator8je3.jpg
From Porsche's Service Training Manual "Fuel and Ignition System 928S4 and 928GT":
http://img256.imageshack.us/img256/3...ulator9wo8.jpg
From data logging of an S4. (Fuel pressure scale is inverted):
http://img256.imageshack.us/img256/9...lator10hc2.jpg
http://img256.imageshack.us/img256/3...lator11sv2.jpg
From Mark:
Originally Posted by mark kibort
that is not the purpose of the vacuum line. its binary. the diaphram holds a constant pressure, regardless of fuel flow to the engine. manifold inlet pressure has no bearing on fuel pressure in the rails, that is dictated by the fuel regulator based on fuel flow through the injectors.
02-11-2007, 06:08 PM
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Originally Posted by mark kibort
again, the main controller of fuel pressure is the spring in the fuel regulator.
I think you can think of it like this;
if there is 55psi fuel pressure in the line, then there is 55psi acting on the fue reg's diaphram....
I think you can think of it like this;
if there is 55psi fuel pressure in the line, then there is 55psi acting on the fue reg's diaphram....
02-11-2007, 10:56 PM
#101
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I was busy over the last 2 days and just did the vacuum measurements. The FPR and the fuel dampners all draw vacuum from the same source. I hooked into that and here is what I found.
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions although I didn't take it all the way to WOT in the garage. The pressure never dropped to zero unless I stabbed the throttle quickly, a condition wherein the throttle is open but the engine has not responded yet. Once it responds, it SUCKS! This was not under load. I'll check it on the way to work tomorrow.
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions although I didn't take it all the way to WOT in the garage. The pressure never dropped to zero unless I stabbed the throttle quickly, a condition wherein the throttle is open but the engine has not responded yet. Once it responds, it SUCKS! This was not under load. I'll check it on the way to work tomorrow.
Last edited by Bill Ball; 02-11-2007 at 11:12 PM.
02-11-2007, 11:29 PM
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Originally Posted by mark kibort
When you see that the differential pressure through out the system is not constant, you get the fact that especially at or near the throttle body, the pressure under part throttle condtions at or around the throttle plate is near ambient
Mk
Mk
Originally Posted by Bill Ball
.......... I hooked into that and here is what I found.
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions
OK..... something is amiss...........
02-11-2007, 11:34 PM
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Originally Posted by worf928
Below is a picture of the 85/86 32v throttle body. I've labeled the three vacuum ports. The largest is the port to the air pump. The smallest is the port for the tank venting valve. That port is in-line with the plane of the throttle plate when the plate is in the idle (closed) state. In this picture I held open the plate a tiny amount so that the pinhole-sized port is visible.
02-11-2007, 11:57 PM
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Originally Posted by BrianG
OK..... something is amiss...........
02-12-2007, 12:07 AM
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Thanks bill, got too busy today and used up all my car time with scot yesterday.
Anyone know why Bill saw 0 vacuum on the FPR with a quick stab?
if you connected to the vacuum booster line, you would see it drop to 5psi or so.
Now, anyone know why the vacuum actuallly went up with constant throttle positions, not in gear? (in idle) Ill give you a hint, it rhymes with Ventura.
the throttle in neutral is still pretty closed with no load on the engine to reach even 5000rpm!
under just a light loads, you will see very low vacuum at that port.
point is, it's a minor adjustment to the air fuel metering system. Most of it, as known now, is the spring pressure matched with fuel line pressure. This is why i dont run the fuel regulator vacuum line. Probaby higher emissions come check time, and higher fuel consumption, but im pretty happy with my 21mpg on the way to Thunderhill last month!
Bill, do post what you see on the road. Ill do a tap as well and see if my car is somehow different. fuel presure is the main thing we are talking about here. the fuel pressure i was noting had a pulled back pressure, but after some gas and some higher rpms, say 2500rpm , the pressure was at max and didnt change for most any load or rpm. This is the true effect and point here.
MK
Anyone know why Bill saw 0 vacuum on the FPR with a quick stab?
if you connected to the vacuum booster line, you would see it drop to 5psi or so.
Now, anyone know why the vacuum actuallly went up with constant throttle positions, not in gear? (in idle) Ill give you a hint, it rhymes with Ventura.
the throttle in neutral is still pretty closed with no load on the engine to reach even 5000rpm!
under just a light loads, you will see very low vacuum at that port.
point is, it's a minor adjustment to the air fuel metering system. Most of it, as known now, is the spring pressure matched with fuel line pressure. This is why i dont run the fuel regulator vacuum line. Probaby higher emissions come check time, and higher fuel consumption, but im pretty happy with my 21mpg on the way to Thunderhill last month!
Bill, do post what you see on the road. Ill do a tap as well and see if my car is somehow different. fuel presure is the main thing we are talking about here. the fuel pressure i was noting had a pulled back pressure, but after some gas and some higher rpms, say 2500rpm , the pressure was at max and didnt change for most any load or rpm. This is the true effect and point here.
MK
Originally Posted by Bill Ball
I was busy over the last 2 days and just did the vacuum measurements. The FPR and the fuel dampners all draw vacuum from the same source. I hooked into that and here is what I found.
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions although I didn't take it all the way to WOT in the garage. The pressure never dropped to zero unless I stabbed the throttle quickly, a condition wherein the throttle is open but the engine has not responded yet. Once it responds, it SUCKS! This was not under load. I'll check it on the way to work tomorrow.
Vacuum at idle: 18
Vacuum with RAPID stab of throttle: 0
Vacuum at ANY throttle position with anything less than a rapid stab: 20.
So, as I moved the throttle steadily away from idle, and not necessarily slowly, the vacuum increased from 18 to 20 as soon as I moved the throttle and stayed there at ALL throttle positions although I didn't take it all the way to WOT in the garage. The pressure never dropped to zero unless I stabbed the throttle quickly, a condition wherein the throttle is open but the engine has not responded yet. Once it responds, it SUCKS! This was not under load. I'll check it on the way to work tomorrow.