The Twin Screw Thread
12-15-2005, 05:03 AM
#181
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Thanks Louie, i had read that also, just wanted to get those that are really familiar with it to perhaps shead some light as well.
Its a whole lot of pressure.......extra pulse duration is the way to go
I am curious what makes the VORTECH FMU differnt from the BEGI unit however?
Brian...If the assembly is already together, dont take it apart. I didnt on Darriens, but i did see some areas that didnt give me the warm fuzzy. So instead of just tossing it on and perhaps chasing a PITA vac leak for a few days, i decided to check everythign over again myself and resealed the perimeter. You dont have to take it apart. I have found that the rightstuff tends to litterally squeeze out of the two halves...inconjuction with boost...vac...boost...vac...heat....etc..id expect it to eventually fail.
The sealing of the perimeter on the outside is just another line of defense agains leaks IMHO....the less leaks the better.
Ounce of prevention is worth.....
Its a whole lot of pressure.......extra pulse duration is the way to go
I am curious what makes the VORTECH FMU differnt from the BEGI unit however?
Brian...If the assembly is already together, dont take it apart. I didnt on Darriens, but i did see some areas that didnt give me the warm fuzzy. So instead of just tossing it on and perhaps chasing a PITA vac leak for a few days, i decided to check everythign over again myself and resealed the perimeter. You dont have to take it apart. I have found that the rightstuff tends to litterally squeeze out of the two halves...inconjuction with boost...vac...boost...vac...heat....etc..id expect it to eventually fail.
The sealing of the perimeter on the outside is just another line of defense agains leaks IMHO....the less leaks the better.
Ounce of prevention is worth.....
12-15-2005, 05:07 AM
#182
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Originally Posted by Bill Ball
Wow. With all the resealing Tony did, if he has it, then there is something systemic. ..................................................As I said, the car runs so well under any kind of power, only stumbling at idle, that I have not pursued it vigorously, especially since it's such a stumper with no clear cause.
IMHO...DEFINITELY IS Bill .
where im not sure.
Like you, its minor and im just driving the **** out of it
The tires dont care for it but the engine/SC sure loves boost on these cool 40'f mornings!
F'N screams! ..really does
12-15-2005, 05:58 AM
#183
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Hi,
I've been away for a few days R&R, so have a couple of comments...re idle quality.
For people like Daryl who are running the 30# units with an 85/86 FPR (30psi at idle) , the sums look like this -
As Louie says, the relationship between fuel flow from an injector for a change of pressure is a square law one. Double the pressure and the fuel flow increases by sq root 2 = 1.4times flow.
This is why the fuel boost WOT fuel pressures have to go so very high to get the flow required.
If you apply this to running a 30# injector (which is rated at that flow at 43.5psi) at 30psi,then the actual flow calculates as 24.9#. This is as stated by Andy.
This means that at idle, instead of running a standard S4/GT/GTS 19# injector, you are running the equivalent of 25#. This may seem "near enough" but in fact the fuel flow is more than 30% higher than it should be. This means you are running at or beyond the adjustment range of the O2 loop, depending on other variables in a particular car.
This may explain some of the hot idle problems people observe.
It would be simple to readjust the idle fuelling with the SharkTuner. A better approach might be to revert back to a standard S4 fuel pressure at idle (47psi) and then optimise idle and cruise fuelling with the Sharktuner. This wouild then mean the 30# injectors are running at their design pressure, and therefore the flow patterns would not suffer as they may be when running at only 30psi
Regards
I've been away for a few days R&R, so have a couple of comments...re idle quality.
For people like Daryl who are running the 30# units with an 85/86 FPR (30psi at idle) , the sums look like this -
As Louie says, the relationship between fuel flow from an injector for a change of pressure is a square law one. Double the pressure and the fuel flow increases by sq root 2 = 1.4times flow.
This is why the fuel boost WOT fuel pressures have to go so very high to get the flow required.
If you apply this to running a 30# injector (which is rated at that flow at 43.5psi) at 30psi,then the actual flow calculates as 24.9#. This is as stated by Andy.
This means that at idle, instead of running a standard S4/GT/GTS 19# injector, you are running the equivalent of 25#. This may seem "near enough" but in fact the fuel flow is more than 30% higher than it should be. This means you are running at or beyond the adjustment range of the O2 loop, depending on other variables in a particular car.
This may explain some of the hot idle problems people observe.
It would be simple to readjust the idle fuelling with the SharkTuner. A better approach might be to revert back to a standard S4 fuel pressure at idle (47psi) and then optimise idle and cruise fuelling with the Sharktuner. This wouild then mean the 30# injectors are running at their design pressure, and therefore the flow patterns would not suffer as they may be when running at only 30psi
Regards
12-15-2005, 10:57 AM
#184
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Originally Posted by Bill Ball
Wow. With all the resealing Tony did, if he has it, then there is something systemic. Mine is very clearly a cylinder 7 miss. When the miss starts, it is a stumble at idle in gear at stoplights. It is worse in park or neutral - a virtual complete drop of cylinder 7. You can hear it in the tail pipe and the car shakes mildly. If I pull the spark boot and/or the injector lead to 7, there is no change at all, whereas all the other cylinders show a response to a pulled lead. Swapped injectors, new plugs, wires, etc. It's always cylinder 7. Hit the gas - no problem. I keep thinking something is leaning out #7 at idle when warm - perhaps related to the bypass passage which is nearest 7. I have not gotten any further with this. As I said, the car runs so well under any kind of power, only stumbling at idle, that I have not pursued it vigorously, especially since it's such a stumper with no clear cause.
12-15-2005, 01:10 PM
#185
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Originally Posted by Gretch
Bill, I am sure you will find it when you go looking for it. May I recommend you check your injector wiring harness? when I did my SC install I found one of my pigtails pinched between the head and the cam cover. I had to repair the insulation on one of the wires in the pigtail. the eratic idle symptom went away when I did that......just a shot in the dark.
When i chased a gremlin down, i replaced all of mine Gretch..i still get it.
no biggy at all, just not perfect.
John, thanks for that info...good stuff.
I would actually like to place the stock 19lb injectors back in to see if that changes the situation...granted i wouldnt be running around with my foot in it all the time, but im curious to see if they would make a difference and return the idle back to "normal" atleast.
12-15-2005, 01:14 PM
#186
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Hello John,
Thank you for responding. I hope you had a great holiday. Your explanations make perfect sense to me now and easy to understand.
When using the Sharktuner do I need to log the engine performance with another device first? When changing to the stock 47 psi fuel pump do you see any reason to use the BEGI? Or for that matter do you see any reason to use the BEGI at all? Do we need any other fuel controls other than the stock fuel pump and the two dampers? When will the Sharktuner with timing control be available? I don’t have a serial port on my lap top only USB ports.
Do you have any thoughts on this issue of a dropped cylinder that Bill is alluding to? The test is shorting out each cylinder one at a time and seeing what the engine RPM does. In Bills case number 7 makes no difference to the idle speed. In my case number 6 makes very little difference to the idle speed but does change a little. We have checked compression, the spark plug looks normal and there is no question that we are getting all 8 cylinders under all other operating parameters. In my case I still need to have the injector checked out but I believe Bill has done that with no change.
I am very interested in tuning with both fuel pumps to see the difference but also tuning different combinations in open loop as well.
Thank you for responding. I hope you had a great holiday. Your explanations make perfect sense to me now and easy to understand.
When using the Sharktuner do I need to log the engine performance with another device first? When changing to the stock 47 psi fuel pump do you see any reason to use the BEGI? Or for that matter do you see any reason to use the BEGI at all? Do we need any other fuel controls other than the stock fuel pump and the two dampers? When will the Sharktuner with timing control be available? I don’t have a serial port on my lap top only USB ports.
Do you have any thoughts on this issue of a dropped cylinder that Bill is alluding to? The test is shorting out each cylinder one at a time and seeing what the engine RPM does. In Bills case number 7 makes no difference to the idle speed. In my case number 6 makes very little difference to the idle speed but does change a little. We have checked compression, the spark plug looks normal and there is no question that we are getting all 8 cylinders under all other operating parameters. In my case I still need to have the injector checked out but I believe Bill has done that with no change.
I am very interested in tuning with both fuel pumps to see the difference but also tuning different combinations in open loop as well.
12-15-2005, 01:25 PM
#187
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Bill,
Now you know why I am trying to find a 928 event somewhere south in January or February. Ok, March, April, or May as well. Actually we can get some nice weather in April and May.
She must a have been a knock out to drive that far and endure such cold weather. Hope she kept you warm while you were here!
Who said global warming is a bad Thing?
Now you know why I am trying to find a 928 event somewhere south in January or February. Ok, March, April, or May as well. Actually we can get some nice weather in April and May.
She must a have been a knock out to drive that far and endure such cold weather. Hope she kept you warm while you were here!
Who said global warming is a bad Thing?
12-15-2005, 01:33 PM
#188
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Daryl & John:
Yes, I tested compression and swapped injectors and leads to rule out anything inherent in cylinder 7.
So, John, are you saying we are running too RICH at idle. The plugs sure don't show that at all. If anything they look lean, although I'm not holding that out as diagnostic. I got a little confused reading your explanation. We are running 30 lb pressure with 30 lb injectors, and that results in too much flow at idle. So, at 30 lbs, below the injectors rated pressure, they are erratic and they would be better at 47 lbs with a lower duty cycle enabled by the Sharktuner, something the LH cannot do on its own? I can buy that explanation as it would explain why there are no drivability issues at all once the throttle is down, the pressure comes up and the injectors are happier.
Yes, I tested compression and swapped injectors and leads to rule out anything inherent in cylinder 7.
So, John, are you saying we are running too RICH at idle. The plugs sure don't show that at all. If anything they look lean, although I'm not holding that out as diagnostic. I got a little confused reading your explanation. We are running 30 lb pressure with 30 lb injectors, and that results in too much flow at idle. So, at 30 lbs, below the injectors rated pressure, they are erratic and they would be better at 47 lbs with a lower duty cycle enabled by the Sharktuner, something the LH cannot do on its own? I can buy that explanation as it would explain why there are no drivability issues at all once the throttle is down, the pressure comes up and the injectors are happier.
12-15-2005, 02:35 PM
#190
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John, I too thought that running an S4 at about 2/3 of stock fuel pressure with 30% greater injector flow would put is back to near-normal fuel delivery into the cylinder.
12-15-2005, 02:42 PM
#192
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Bill said,
"So, John, are you saying we are running too RICH at idle. The plugs sure don't show that at all. If anything they look lean,"
On my car it runs great cold and gets worse as it warms up. Which seem to me it wants a richer mixture when warm.
"So, John, are you saying we are running too RICH at idle. The plugs sure don't show that at all. If anything they look lean,"
On my car it runs great cold and gets worse as it warms up. Which seem to me it wants a richer mixture when warm.
12-15-2005, 03:03 PM
#194
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With 30 pound injectors my 85 idled at 14.5 as indicated on wideband, rich at 3000 and lean at 5000-6000. I don't remember the idle fuel pressure. I'm delayed going to the dyno to tune with the SMT-6. It was checked repeatedly for vacuum leaks using propane. A slight stumble at 2000 was eliminated after the SC install, I think it was from a small vacuum leak. AfterI've been to the dyno I'll post my fuel pressure and SMT-6 settings for reference.
12-15-2005, 04:28 PM
#195
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Hi Rick,
I tried propane and starter fluid but I found the most effective way to find air leaks is with a smoke machine or a smaller diameter tire tube cut open then stretched over the intake inlet and clamped tight then roll up the other end and clamp tight so it doesn't leak. Put a few pounds pressure in. A hose or piece of vac line held to your ear to listen through works great.
I tried propane and starter fluid but I found the most effective way to find air leaks is with a smoke machine or a smaller diameter tire tube cut open then stretched over the intake inlet and clamped tight then roll up the other end and clamp tight so it doesn't leak. Put a few pounds pressure in. A hose or piece of vac line held to your ear to listen through works great.
