SLP Lid install
08-06-2011, 01:32 PM
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SLP Lid install Had a friend install my SLP lid yesterday. Looks like the hose that attaches to the airbox had a big hole in the bottom. So when we took it off, the screen was full of dirt, dust, and other crap. Didn't know it was so filthy. Wish I could have gotten a picture to show, but it looked bad. We disconnected the battery for the installation too.
Right after the install I went to start the car up, it started...but then it started idling really low, around 200-400RPM, like it was trying to die. This made me really nervous, so I gave it some gas, revved it up to 2,000-3,000 RPM and let it settle down again, it tried to die again! So I revved it up a tad higher this time and put it in gear. Once in gear it seemed fine, took it for a test drive. Don't feel too much of a difference with the Lid installed and a cleaned screen.
I do feel like it pulls slightly harder in the higher RPM bands, around 4,000-5,000 it feels a little stronger, I think.
Any ideas on why the car was trying to die right after the install and cleaned screen? The car is running fine now, no problems. I'm hoping to get a little better fuel economy with a clean screen and bigger air box.
Right after the install I went to start the car up, it started...but then it started idling really low, around 200-400RPM, like it was trying to die. This made me really nervous, so I gave it some gas, revved it up to 2,000-3,000 RPM and let it settle down again, it tried to die again! So I revved it up a tad higher this time and put it in gear. Once in gear it seemed fine, took it for a test drive. Don't feel too much of a difference with the Lid installed and a cleaned screen.
I do feel like it pulls slightly harder in the higher RPM bands, around 4,000-5,000 it feels a little stronger, I think.
Any ideas on why the car was trying to die right after the install and cleaned screen? The car is running fine now, no problems. I'm hoping to get a little better fuel economy with a clean screen and bigger air box.
08-06-2011, 03:55 PM
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Descreening the MAF will bork readings. It depends on the car, how much it screws up - some cars run fine that way, some run shitty. There's a thread on here about alternative MAF screen replacement, if you want to remove the stock screen but still get good readings from the MAF.
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08-06-2011, 08:14 PM
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During the installation we took the screen out, found lots of dirt in there, so we cleaned it out and put it back in. I'm keeping the screen in. Somehow I developed a hole in the hose leading to the screen, so all that dirt and dust got past the air filter, and the screen was the only thing that stopped it.
Granted, if you have a good hose with no leaks, you will probably have no problems. But seeing how important that screen can be, I am keeping it.
I only disconnected the battery because the instructions said to. I wanted to go exactly as they had worded it, not exactly sure why they said you have to, but I did anyways. Still, the idle right afterwards made me very nervous. Like I said, after a couple of minutes of running and revving it up it came back to normal.
Granted, if you have a good hose with no leaks, you will probably have no problems. But seeing how important that screen can be, I am keeping it.
I only disconnected the battery because the instructions said to. I wanted to go exactly as they had worded it, not exactly sure why they said you have to, but I did anyways. Still, the idle right afterwards made me very nervous. Like I said, after a couple of minutes of running and revving it up it came back to normal.
08-06-2011, 08:24 PM
#12
I only disconnected the battery because the instructions said to. I wanted to go exactly as they had worded it, not exactly sure why they said you have to, but I did anyways. Still, the idle right afterwards made me very nervous. Like I said, after a couple of minutes of running and revving it up it came back to normal.
08-06-2011, 08:28 PM
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The screen isn't there to stop debris (although that can be a handy side effect).
It evens out the velocity across the entire intake by creating a little bit of a drag effect... as many have figured out through the tidbits of information about MPG, air drag is increased exponentially as velocity increases... as such, if you put a screen there, it will add a LOT of drag to high-velocity areas, and significantly less drag to the lower-velocity areas, smoothing out any large velocity gradients (It also transitions every bit of air to a turbulent flow pattern if it isn't already there, but it also creates a more consistent amount of turbulence throughout the airmass). Now, since the MAF measures mass flow by how much voltage it takes to maintain a certain temperature, that velocity is exceedingly important... but it doesn't measure across the entire cross-section of the MAF housing, but only through the part the wire is in. So it should be somewhat obvious to know that for it to have an accurate reading, the velocity profile should be as consistent as possible throughout the cross-section.
Now, some intakes happen to be very consistent across the section, or just so happen to have nearly an average mass-measurement based on the section the wire is in... others don't. Might have something to do with the variance of some people's cars freaking out, and others' having no problems whatsoever.
Like has been said... probably won't see an appreciable increase in fuel economy, and your idle was probably rough for that little bit of time while your car re-learned how to idle properly.
It evens out the velocity across the entire intake by creating a little bit of a drag effect... as many have figured out through the tidbits of information about MPG, air drag is increased exponentially as velocity increases... as such, if you put a screen there, it will add a LOT of drag to high-velocity areas, and significantly less drag to the lower-velocity areas, smoothing out any large velocity gradients (It also transitions every bit of air to a turbulent flow pattern if it isn't already there, but it also creates a more consistent amount of turbulence throughout the airmass). Now, since the MAF measures mass flow by how much voltage it takes to maintain a certain temperature, that velocity is exceedingly important... but it doesn't measure across the entire cross-section of the MAF housing, but only through the part the wire is in. So it should be somewhat obvious to know that for it to have an accurate reading, the velocity profile should be as consistent as possible throughout the cross-section.
Now, some intakes happen to be very consistent across the section, or just so happen to have nearly an average mass-measurement based on the section the wire is in... others don't. Might have something to do with the variance of some people's cars freaking out, and others' having no problems whatsoever.
Like has been said... probably won't see an appreciable increase in fuel economy, and your idle was probably rough for that little bit of time while your car re-learned how to idle properly.
08-06-2011, 08:32 PM
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Just filled up with a full tank of gas tonight, will be driving the car easy for a little while, trying to see if I get an MPG inscrease. I normally average 20-21MPG, with 40% citiy driving and 60% highway.
08-06-2011, 08:47 PM
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I disconnected the battery when I installed my SLP cags eliminator. Just being overkill cautious. When I reconnected the battery it ran like crap and the voltage was reading very low. After driving about 2 miles everything seemed normal again. I haven't had any further issues.
I figured it was just the computer relearning something.
I figured it was just the computer relearning something.
Last edited by stingrayj; 08-07-2011 at 07:28 AM.
08-06-2011, 08:48 PM
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Sounds exactly like my experience. I gotta say, the car didn't run that strong right after the install. But after a few miles of driving it, everything returned to normal.
08-30-2011, 10:14 PM
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I had the same problem after some A/C work where they unhooked the battery. It actually ran worse the second day. After the CPU reset the idle a couple days later it was fine. I have seen this in several newer cars as well.
