Advanced IAC question
07-11-2009, 09:54 AM
#1
6th Gear Member
Thread Starter
Join Date: Feb 2006
Location: Virginia
Posts: 11,786
Advanced IAC question
Has anyone ever converted their IAC from the independent air source model to one that doesn't require the fresh air tube that looks like crap across the engine bay?? I know that the explorers use an IAC that doesn't use external air, could that be modified on the plenum? The tube is a sore thumb in my bay.
07-11-2009, 08:15 PM
#5
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
The IAC bypasses air that has been metered by the MAF, around the throttle body. The PCM controls the amount of air being bypassed to control the idle.
On some engines there's a port upstream of the throttle plate, and another downstream, built in to the TB. The TB in our cars is not designed in that manner however perhaps one so designed could be fitted.
In your setup it looks as though steps were taken to prevent boost from acting upon the IAC. This is likely a wise move as neither the IAC plumbing nor the valve itself were designed to deal with pressurized input air--the opposite actually, on a n/a setup the IAC only "sees" vacuum.
On my JRSC'd '90 Miata there was a similar hose--leading from just after the AFM and before the blower, around to the IAC (under a dummy TB)-- in which a low force check valve was placed to block a back flow of boost. You can see the 3/4" hose sweeping across the front, the check valve is the silver thingy near the radiator cap.
Other than trying to make it look as good as possible I don't know what to tell you--maybe get rid of the Helmholtz resonator (it's just noise suppression thing) and see if you can find a molded hose with a 90° bend, and couple it to a longer hose that can be routed more discretely.
On some engines there's a port upstream of the throttle plate, and another downstream, built in to the TB. The TB in our cars is not designed in that manner however perhaps one so designed could be fitted.
In your setup it looks as though steps were taken to prevent boost from acting upon the IAC. This is likely a wise move as neither the IAC plumbing nor the valve itself were designed to deal with pressurized input air--the opposite actually, on a n/a setup the IAC only "sees" vacuum.
On my JRSC'd '90 Miata there was a similar hose--leading from just after the AFM and before the blower, around to the IAC (under a dummy TB)-- in which a low force check valve was placed to block a back flow of boost. You can see the 3/4" hose sweeping across the front, the check valve is the silver thingy near the radiator cap.
Other than trying to make it look as good as possible I don't know what to tell you--maybe get rid of the Helmholtz resonator (it's just noise suppression thing) and see if you can find a molded hose with a 90° bend, and couple it to a longer hose that can be routed more discretely.
07-11-2009, 10:49 PM
#6
1st Gear Member
Join Date: Feb 2009
Location: Texas
Posts: 138
Has anyone ever converted their IAC from the independent air source model to one that doesn't require the fresh air tube that looks like crap across the engine bay?? I know that the explorers use an IAC that doesn't use external air, could that be modified on the plenum? The tube is a sore thumb in my bay.
But yes...it does stick out...Maybe you could fabricate some nice chrome/alum piping for the long distances...similar to the replacement chrome radiator upper hose.
07-12-2009, 09:13 AM
#7
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Join Date: Dec 2006
Location: Saint Augustine, FL
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Good suggestion, very often if something cannot be succesfully hidden highlighting it is the best alternative.
07-12-2009, 09:15 AM
#8
3rd Gear Member
Join Date: Apr 2007
Location: Georgia
Posts: 931
http://sn95forums.com/index.php/topic,37375.0.html
Only one I've seen do this. I haven't tried it yet, but I'd like to.
Only one I've seen do this. I haven't tried it yet, but I'd like to.
07-12-2009, 07:02 PM
#9
6th Gear Member
Thread Starter
Join Date: Feb 2006
Location: Virginia
Posts: 11,786
http://sn95forums.com/index.php/topic,37375.0.html
Only one I've seen do this. I haven't tried it yet, but I'd like to.
Only one I've seen do this. I haven't tried it yet, but I'd like to.
Cliff, what do you think about that ^?
The IAC bypasses air that has been metered by the MAF, around the throttle body. The PCM controls the amount of air being bypassed to control the idle.
On some engines there's a port upstream of the throttle plate, and another downstream, built in to the TB. The TB in our cars is not designed in that manner however perhaps one so designed could be fitted.
In your setup it looks as though steps were taken to prevent boost from acting upon the IAC. This is likely a wise move as neither the IAC plumbing nor the valve itself were designed to deal with pressurized input air--the opposite actually, on a n/a setup the IAC only "sees" vacuum.
Other than trying to make it look as good as possible I don't know what to tell you--maybe get rid of the Helmholtz resonator (it's just noise suppression thing) and see if you can find a molded hose with a 90° bend, and couple it to a longer hose that can be routed more discretely.
On some engines there's a port upstream of the throttle plate, and another downstream, built in to the TB. The TB in our cars is not designed in that manner however perhaps one so designed could be fitted.
In your setup it looks as though steps were taken to prevent boost from acting upon the IAC. This is likely a wise move as neither the IAC plumbing nor the valve itself were designed to deal with pressurized input air--the opposite actually, on a n/a setup the IAC only "sees" vacuum.
Other than trying to make it look as good as possible I don't know what to tell you--maybe get rid of the Helmholtz resonator (it's just noise suppression thing) and see if you can find a molded hose with a 90° bend, and couple it to a longer hose that can be routed more discretely.
Last edited by Sxynerd; 07-12-2009 at 07:12 PM.
07-13-2009, 05:33 PM
#10
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
The IAC has to have metered air as it's input, that is air in addition to the air bleed around the throttle plate. I have seen many plenums and TB's that accomplish this by having passage ways that feed air around the throttle plate--if you look at the IAC on our cars you can see that the casting is set up to allow for "in" and "out" ports.
The IAC air needs to be metered so that the PCM can see the air passed by the IAC and add fuel as needed--otherwise all that would happen would be a leaner mix.
Although I know of dozens of people running the IAC from the pressurized inlet after the S/C before the TB I have always been skeptical of it not affecting the system. I guess, their logic is that at idle is when the IAC is active it doesn't affect it during boost when the IAC isn't active.