Lean condition after driving for about an hour
03-27-2016, 10:06 AM
#1
Lean condition after driving for about an hour Been having this issue where it runs fine and idles fine until about after an hour of driving then my idle and cruise afrs go from 13 to 14 up to mid 15s to 16s and if you try and get into boost it leans out off of the scale. It is really weird because it runs perfectly fine and only does this after it gets hot and is driven for a while. Anyone have any ideas on what might be the culprit?
Car is a 408 BW S476 car. It has 80lb injectors and dual in tank 340s.
Car is a 408 BW S476 car. It has 80lb injectors and dual in tank 340s.
03-27-2016, 05:54 PM
#2
9 Second Club
Driving for an hour is vague....
like sitting at 60 for an hour, sitting stuck in traffic for an hour etc etc ?
And are mixtures going lean because the ecu is making them lean ( very easy to see as injector pulse widths would get lower )...or some other reason ?
And hot is vague...what is hot ? are temperatures nor normal when this happens ?
Presumably closed loop control is not working ?
like sitting at 60 for an hour, sitting stuck in traffic for an hour etc etc ?
And are mixtures going lean because the ecu is making them lean ( very easy to see as injector pulse widths would get lower )...or some other reason ?
And hot is vague...what is hot ? are temperatures nor normal when this happens ?
Presumably closed loop control is not working ?
03-27-2016, 06:39 PM
#3
Sorry I was vague. Driving for an hour meaning just cruising around the city enjoying the weather and the car.
Temp is normal when it happens, around 175.
I'm not sure about the other as I'm not a tuner. I did however go out today to recreate the problem which it did and I shut it off for an hour and tried to recreate it again which I couldn't but I was going to check my fuel pressure if it did. Only difference was I filled it up with gas before I went cruising around.
Temp is normal when it happens, around 175.
I'm not sure about the other as I'm not a tuner. I did however go out today to recreate the problem which it did and I shut it off for an hour and tried to recreate it again which I couldn't but I was going to check my fuel pressure if it did. Only difference was I filled it up with gas before I went cruising around.
03-28-2016, 06:38 AM
#4
9 Second Club
Really information is everything, the more you have, the more you can pinpoint any cause.
But again...why is closed loop not correcting this, or is it trying and unable to ? Or is it not active at all ?
It's unlikely air temp, unlikely engine coolant temp, as everything you say seems to suggest these are fairly constant ( again, need info )
You could check fuel pressure, but first and foremost see what closed loop is doing, and also what injector pulse widths are when it's good and when it's bad....those will help tell you if it's a control issue or external problem
But again...why is closed loop not correcting this, or is it trying and unable to ? Or is it not active at all ?
It's unlikely air temp, unlikely engine coolant temp, as everything you say seems to suggest these are fairly constant ( again, need info )
You could check fuel pressure, but first and foremost see what closed loop is doing, and also what injector pulse widths are when it's good and when it's bad....those will help tell you if it's a control issue or external problem
03-28-2016, 07:30 AM
#5
Lean condition after driving for about an hour Ok thanks for the info. I'll try and get some more information but it sounds like you are leaning towards something tune related and that's what I was thinking as well. I just wanted to run it by someone with more knowledge than me. I'm going to call the place that tuned it and see what they say.
03-28-2016, 07:35 AM
#6
9 Second Club
Really logging info when it's good...and bad and comparing results will yield the best info, as well as finding out why closed loop isnt doing it's job, and if it is and is not capable of correcting...why not and why is it so far out.
03-31-2016, 08:55 AM
#7
Haven't been able to log anything but I was told that it could be vapor lock. I have only seen it happen if the tank is half or below and last time it did it filling the tank made it not happen again. He said that with the tank at half or below the low amount of fuel moving all of the time with both pumps could be getting hot and turning to vapor causing the lean condition.
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03-31-2016, 03:48 PM
#10
The pumps are transferring the same rate of thermal energy to the fuel it is submerged in at all times. If they transfer this heat to 16.8 gallons of fuel, the average temperature in the fuel can be expected to be marginally affected. However, if the same rate of heat energy is applied to 8 or 6 gallons of fuel, it's reasonable to expect that the average temperature of the fuel will rise more.
Since fuel is volatile, higher temps mean a substantial increase in vapor pressure. At some point, hot fuel will vaporize. That point of vaporization depends on fuel temp and pressure. So, maybe the pumps don't pump "vapor", but they could be pumping fuel close to vaporization. Does that affect the fuel at the rail? How much?
03-31-2016, 03:57 PM
#11
9 Second Club
I've been spying on these responses because I suffered this when I drove to Houston... seemed like when the tank went below around half full it would start creeping up in AFR.
The pumps are transferring the same rate of thermal energy to the fuel it is submerged in at all times. If they transfer this heat to 16.8 gallons of fuel, the average temperature in the fuel can be expected to be marginally affected. However, if the same rate of heat energy is applied to 8 or 6 gallons of fuel, it's reasonable to expect that the average temperature of the fuel will rise more.
Since fuel is volatile, higher temps mean a substantial increase in vapor pressure. At some point, hot fuel will vaporize. That point of vaporization depends on fuel temp and pressure. So, maybe the pumps don't pump "vapor", but they could be pumping fuel close to vaporization. Does that affect the fuel at the rail? How much?
The pumps are transferring the same rate of thermal energy to the fuel it is submerged in at all times. If they transfer this heat to 16.8 gallons of fuel, the average temperature in the fuel can be expected to be marginally affected. However, if the same rate of heat energy is applied to 8 or 6 gallons of fuel, it's reasonable to expect that the average temperature of the fuel will rise more.
Since fuel is volatile, higher temps mean a substantial increase in vapor pressure. At some point, hot fuel will vaporize. That point of vaporization depends on fuel temp and pressure. So, maybe the pumps don't pump "vapor", but they could be pumping fuel close to vaporization. Does that affect the fuel at the rail? How much?
And far more heat comes from hot rails ( in a return style system ) than comes from the pumps.
If you believe and can prove hot fuel is an issue, then just fit a fuel cooler ( again much easier on a return style system )
I've tested my own 044's running alone to see if they heat the fuel...and whilst they do, for the time period I tested I'd consider the temperature rise of no concern at all.
I've logged fuel temp on my own car for years and again never seen anything that's given me concern. That said, I dont see the ambient temps some places in the US would see.
Weather here is usually ****. But I can easily drive for 4 hours with no issues from a full tank to empty tank.
But again, if you think the problem is related to fuel temp...simply log it or just fit a cooler.
03-31-2016, 04:17 PM
#12
I've been spying on these responses because I suffered this when I drove to Houston... seemed like when the tank went below around half full it would start creeping up in AFR.
The pumps are transferring the same rate of thermal energy to the fuel it is submerged in at all times. If they transfer this heat to 16.8 gallons of fuel, the average temperature in the fuel can be expected to be marginally affected. However, if the same rate of heat energy is applied to 8 or 6 gallons of fuel, it's reasonable to expect that the average temperature of the fuel will rise more.
Since fuel is volatile, higher temps mean a substantial increase in vapor pressure. At some point, hot fuel will vaporize. That point of vaporization depends on fuel temp and pressure. So, maybe the pumps don't pump "vapor", but they could be pumping fuel close to vaporization. Does that affect the fuel at the rail? How much?
The pumps are transferring the same rate of thermal energy to the fuel it is submerged in at all times. If they transfer this heat to 16.8 gallons of fuel, the average temperature in the fuel can be expected to be marginally affected. However, if the same rate of heat energy is applied to 8 or 6 gallons of fuel, it's reasonable to expect that the average temperature of the fuel will rise more.
Since fuel is volatile, higher temps mean a substantial increase in vapor pressure. At some point, hot fuel will vaporize. That point of vaporization depends on fuel temp and pressure. So, maybe the pumps don't pump "vapor", but they could be pumping fuel close to vaporization. Does that affect the fuel at the rail? How much?
04-04-2016, 08:47 AM
#17
9 Second Club