Interesting Idle Vacuum Correlations PART 2
09-01-2008, 12:31 PM
#104
Well, one by one, I effectively removed any aftermarket loads and there was no difference.
Perhaps there is an area in the OE wiring harness that is chafed or a module that is failing. There is nothing apparent, though.
However, I think I may have one issue that might be contributing -
I went for a 200 mile or so drive yesterday up through Payson, through the Tonto National Forest, Pine and then over through Prescott and down the 89a.
This has significant altitude changes and, as usual, I went roaring through them all in boost. This means the motor was in 5 - 9 PSI continuously for several minutes at a time.
Its a beautiful thing.
However, I noticed that there was a faint smell of fuel coming in when the HVAC was set to "fresh" and I was in boost for any length of time, which got me thinking.
I've been checking for a vacuum leak the traditional way. But what if there is some sort of leak across the secondaries or tertiary ports? I know its all self contained, but I guess I should, at least, pull the UIM and fuel rails and figure out where the smell was coming from.
Perhaps there is an area in the OE wiring harness that is chafed or a module that is failing. There is nothing apparent, though.
However, I think I may have one issue that might be contributing -
I went for a 200 mile or so drive yesterday up through Payson, through the Tonto National Forest, Pine and then over through Prescott and down the 89a.
This has significant altitude changes and, as usual, I went roaring through them all in boost. This means the motor was in 5 - 9 PSI continuously for several minutes at a time.
Its a beautiful thing.
However, I noticed that there was a faint smell of fuel coming in when the HVAC was set to "fresh" and I was in boost for any length of time, which got me thinking.
I've been checking for a vacuum leak the traditional way. But what if there is some sort of leak across the secondaries or tertiary ports? I know its all self contained, but I guess I should, at least, pull the UIM and fuel rails and figure out where the smell was coming from.
09-01-2008, 12:49 PM
#105
Well, one by one, I effectively removed any aftermarket loads and there was no difference.
Perhaps there is an area in the OE wiring harness that is chafed or a module that is failing. There is nothing apparent, though.
However, I think I may have one issue that might be contributing -
I went for a 200 mile or so drive yesterday up through Payson, through the Tonto National Forest, Pine and then over through Prescott and down the 89a.
This has significant altitude changes and, as usual, I went roaring through them all in boost. This means the motor was in 5 - 9 PSI continuously for several minutes at a time.
Its a beautiful thing.
However, I noticed that there was a faint smell of fuel coming in when the HVAC was set to "fresh" and I was in boost for any length of time, which got me thinking.
I've been checking for a vacuum leak the traditional way. But what if there is some sort of leak across the secondaries or tertiary ports? I know its all self contained, but I guess I should, at least, pull the UIM and fuel rails and figure out where the smell was coming from.
Perhaps there is an area in the OE wiring harness that is chafed or a module that is failing. There is nothing apparent, though.
However, I think I may have one issue that might be contributing -
I went for a 200 mile or so drive yesterday up through Payson, through the Tonto National Forest, Pine and then over through Prescott and down the 89a.
This has significant altitude changes and, as usual, I went roaring through them all in boost. This means the motor was in 5 - 9 PSI continuously for several minutes at a time.
Its a beautiful thing.
However, I noticed that there was a faint smell of fuel coming in when the HVAC was set to "fresh" and I was in boost for any length of time, which got me thinking.
I've been checking for a vacuum leak the traditional way. But what if there is some sort of leak across the secondaries or tertiary ports? I know its all self contained, but I guess I should, at least, pull the UIM and fuel rails and figure out where the smell was coming from.
09-01-2008, 01:02 PM
#106
You haven't lived until you are gaining 1000 feet a minute at 90 miles an hour in continuous boost.
I wiped out my first motor that way (a combination of extreme overheating and then a massive ping), but these days there is seemingly no chance of that.
EGTs were stable, AFR was locked to 11.8:1 and engine temps stayed below 210°, despite the heat.
While every vehicle around me was struggling to get up the hill in a low gear, I just left it in 5th and pedaled it (WOT produced too much acceleration, so I was juggling it around 70% or so most of the way).
I wiped out my first motor that way (a combination of extreme overheating and then a massive ping), but these days there is seemingly no chance of that.
EGTs were stable, AFR was locked to 11.8:1 and engine temps stayed below 210°, despite the heat.
While every vehicle around me was struggling to get up the hill in a low gear, I just left it in 5th and pedaled it (WOT produced too much acceleration, so I was juggling it around 70% or so most of the way).
09-01-2008, 01:26 PM
#109
Administrator
iTrader: (7)
damn Jeff, lets just tear the whole car apart and start from scratch! I'll bring the Phillips head screwdriver. 
That drive sounds like a blast!
That drive sounds like a blast!
09-01-2008, 10:00 PM
#113
Jeff you still have the hood mod in place--right? Then you know where the smell is coming from--its contained engine bay smell, a little exhaust maybe, a little radiator coolant maybe, left over oil drops etc. i have it in mine when the air supply is on fresh.
that watermeth kit--errr sorry--that water injection system is helping with those runs probably?!
have you checked the electric power steering stuff --it is pretty demanding concerning power..
olddragger
that watermeth kit--errr sorry--that water injection system is helping with those runs probably?!
have you checked the electric power steering stuff --it is pretty demanding concerning power..
olddragger
09-02-2008, 12:58 AM
#114
Nah. This time the smell is raw fuel.
My car doesn't have oily/fume/coolant smells. That is part of the drivability thing for me.
Water/meth is definitely helping - that's why I installed it.
Power steering was the first culprit I checked. No dice.
My car doesn't have oily/fume/coolant smells. That is part of the drivability thing for me.
Water/meth is definitely helping - that's why I installed it.
Power steering was the first culprit I checked. No dice.
09-02-2008, 12:37 PM
#116
Lubricious
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Has this been the case for all engines where you observed the 15" idle vacuum?
Certainly not my area of expertise but I do remember some long treatises by RotaryGod concerning flow, exhaust pulses, etc.. What I took away from that was that back pressure is not necessarily good or bad, but just one factor working in concert with others. Perhaps the lack of a cat could actually account for that minor difference in vacuum at idle?
Certainly not my area of expertise but I do remember some long treatises by RotaryGod concerning flow, exhaust pulses, etc.. What I took away from that was that back pressure is not necessarily good or bad, but just one factor working in concert with others. Perhaps the lack of a cat could actually account for that minor difference in vacuum at idle?
09-02-2008, 12:44 PM
#117
I haven't had a CAT on the car since 2004.
Exhaust back-pressure was one of the first things I considered, but:
1) I'm pretty sure that this issue is something "evolutionary" in some other part of the setup because earlier versions of my turbo setup did not exhibit this behavior
2) Other cars with my exact turbo /manifold/midpipe setup do not exhibit this behavior
3) I attached a pipette to my EGT bung and took pressure readings, which indicate nearly no pressure at idle and the nominal 2:1 ratio at full boost.
Exhaust back-pressure was one of the first things I considered, but:
1) I'm pretty sure that this issue is something "evolutionary" in some other part of the setup because earlier versions of my turbo setup did not exhibit this behavior
2) Other cars with my exact turbo /manifold/midpipe setup do not exhibit this behavior
3) I attached a pipette to my EGT bung and took pressure readings, which indicate nearly no pressure at idle and the nominal 2:1 ratio at full boost.
09-02-2008, 01:36 PM
#120
around 15" at idle.
if I rev it a bit the vacuum goes to 21" range. Same on engine braking - 21 to 22" range.
my new engine has brake new seals, housings, etc. it should be perfect. vacuum readings are the same.
if I rev it a bit the vacuum goes to 21" range. Same on engine braking - 21 to 22" range.
my new engine has brake new seals, housings, etc. it should be perfect. vacuum readings are the same.
09-02-2008, 01:58 PM
#123
Well, he is at an even lower elevation, so the difference is even more puzzling.
I dunno. I'm kinda over it now, but I'd love to understand it and, apparently Fred is the only one to contribute to this thread that knows the answer.
But, in what is becoming an evermore characteristic act of spite, he isn't saying anything.
I dunno. I'm kinda over it now, but I'd love to understand it and, apparently Fred is the only one to contribute to this thread that knows the answer.
But, in what is becoming an evermore characteristic act of spite, he isn't saying anything.
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