Fallstar01

Why would it help in a speed contest?

UhadMEatGT

Why copper??

jishead

because I can't shift worth a !@#$ when the RPM's are just hanging around doint whatever they feel like doing. If I take my foot of the gas, I really need the RPM's to drop proportionally. Probably folks who are slightly older like me are more sensitive to this (accustomed to carb engines?). Anyway, I can really stuff it in the next gear up or down when the RPM's drop faster IMHO.

jishead

Probably because end cap fittings are readily available in copper. Probably doesn't matter what they are made of since it is vaccuum only. On my Contour, I used a copper cap with a hole drilled. On my Mustang, we used like some thing sheet metal nearly like aluminum siding (more like a flat plate than a cap). Copper probably doesn't matter. Just restrict the volume of air that the computer can use to HANG your throttle when it should be falling if you like a sportier, crisper feel IMHO. I have suffer zero negative affects in either car that I have done this one. They are both mod'd commuter cars.

UhadMEatGT

I am intersted in trying this with my auto? DO you have any pics of where this is installed?

Stang4Point6GT98

I have a 1998 GT and my car does EXACTLY what you are talking about. I have an automatic and when you slide it into neutral or when it is in park and you rev it up it takes FOREVER for the RPMS to come back down. It sounds really unnatural and retarded. I have always wondered if it is just my car or if all 96-98 4.6L Mustangs do it. My buddy has a 2003 GT and we compared and his seems to rev pretty normal. If anyone knows what I'm talking about please let me know!

Aixtreme89

On my 03 GT 5 speed the revs hang there too. Its really annoying. Did anyone figure out a fix for it yet?? Post pictures or a description if anyone did. Thanks....

sickspeedgt

this probably isn't whats wrong with yours but, my RPMs where hanging after i switched my gauge faces, but mine was because i put the need on too tight............. but if you haven't taken your needles off then your problem probably lies somewhere else

sickspeedgt

i can't type, i meant to put my NEEDLE

jishead

Look at your throttle body. See where the black hose brings air from your intake into your throttle body? That's how the computer feeds air above and beyond what your butterfly opening is currently doing in order to keep transient RPM's from ruining emissions / mileage I think. Anyway, there is a plate with two bolts where the rubber hose goes into the throttle body. If you make a restrictor plate to fit in there you can restrict how much air is available to hang your RPM's. We made my plate out of thin siding like metal material. There is some debate on what size hole to drill. If you restrict too much air, your computer will have a hard time idling your car like when it's cold out (1000 rpm). If you restrict too little air, then you simply won't eliminate your throttle hang. Apparently we did a good job on mine cuz mine can still idle at 1000 rpm when it wants but the hang is very much reduced. Search for IAC plate. There is even a drawing out there. If I get time, I'll take mine out or take pics but it is a little pain and I'm a little lazy.