coolant bypass mod
Apr 27, 2007, 08:31 AM
#1
Evolved Member
Thread Starter
iTrader: (9)
Join Date: Jun 2006
Location: NH
Posts: 1,240
Likes: 0
Received 0 Likes
on
0 Posts
coolant bypass mod
i did some research here on evom and on google about this mod... it seems like it's really a free mod that you can benefit from. i ran into dyno sheets where this mod actually made a proven difference. we probably will not get the same kind of gains as say, a LS1 would... but i'm confident that we will get something on our cars.
here's some background:
sorry for making that so long... i just wanted to compile all the information i found about this mod here in one place. the way i performed the bypass was by removing both the stock hoses going from the head to the TB and from the other coolant line to the TB.
with both hoses removed i connected the two points to each other by using a length of 5/16" hose with clamps on either end. to plug up the connections on the TB itself i used 1/4" vacuum caps.
every little bit helps!
sorry for the low quality of the pictures... i used my cell phone--but you get the idea.
here's some background:
The DSM and EVO throttle bodies have two mechanical and one electric control of idle speed.
The electric control is the stepper motor controled by the ECU that opens up a bit to raise idle, and closes to lower idle.
The first mechanical idle control is the Base Idle Set Screw (BISS) The BISS is a screw that blocks off a passage that allows airflow to bypass the throttle plate. You turn the screw out and more air bypasses the throttle plate raising your idle, turn the screw in and less air is bypassing the throttle plate and your idle goes down.
The second mechanical idle control is the Fast Idle Air Valve (FIAV) The FIAV is a plastic/wax plug that blocks off a passage that allows airflow to bypass the throttle plate. when this plug is cold is shrinks and blocks less of the air passage and more air bypasses the throttle plate raising your idle, as the coolant heats up, the plug gets warm and grows blocking more of the air passage so less air is bypassing the throttle plate and your idle goes down.
If you get ride of the coolant lines to the throttle body, the car will remain in "high idle mode" for a lot longer because the entire engine bay has to warm up before the FIAV will expand. The electric control can somewhat compensate for this, but if you live in a cold climate the compensation required will be out of it's range of adjustment and you will need to adjust the BISS on a seasonal basis to compensate.
Keith
The electric control is the stepper motor controled by the ECU that opens up a bit to raise idle, and closes to lower idle.
The first mechanical idle control is the Base Idle Set Screw (BISS) The BISS is a screw that blocks off a passage that allows airflow to bypass the throttle plate. You turn the screw out and more air bypasses the throttle plate raising your idle, turn the screw in and less air is bypassing the throttle plate and your idle goes down.
The second mechanical idle control is the Fast Idle Air Valve (FIAV) The FIAV is a plastic/wax plug that blocks off a passage that allows airflow to bypass the throttle plate. when this plug is cold is shrinks and blocks less of the air passage and more air bypasses the throttle plate raising your idle, as the coolant heats up, the plug gets warm and grows blocking more of the air passage so less air is bypassing the throttle plate and your idle goes down.
If you get ride of the coolant lines to the throttle body, the car will remain in "high idle mode" for a lot longer because the entire engine bay has to warm up before the FIAV will expand. The electric control can somewhat compensate for this, but if you live in a cold climate the compensation required will be out of it's range of adjustment and you will need to adjust the BISS on a seasonal basis to compensate.
Keith
This modification disables the FIAV (Fast Idle Air Valve) present in the throttle body. When the throttle body is cold a "plug" shrinks down opening up extra air passages in the throttle body alowing more air into the intake manifold for a fast idle on cold start up. As the coolant warms up the "plug" expands due to the heat blocking off the extra air passages so that your idle drops back down to normal.
The regular idle air valve can compensate some if you bypass the coolant lines, but you may need to make "seasonal" changes in your BISS (Bass Idle Set Screw) rather than having cold weather automaticly compensated for by the FIAV.
Keith
The regular idle air valve can compensate some if you bypass the coolant lines, but you may need to make "seasonal" changes in your BISS (Bass Idle Set Screw) rather than having cold weather automaticly compensated for by the FIAV.
Keith
In order to actually cause the throttle plate to stick, you would have to maintain a constant throttle position for a long time. If you are constantly increasing and decreasing the throttle position, you are causing the plate to move. This does not give the plate a chance to stick. On an aircraft, the throttle is put in one position and may stay there for hours. This can cause the plate to stick. I think in an automotive application we are mostly OK removing the throttlebody coolant supply...
So I just bought a new 06' lancer ES and I've been looking for ways to increase HP without ripping a whole in my pocketbook. I decided to run a little experiment in regards to temperature difference. This is a before and after of temp difference on the throttlebody when doing the coolant bypass mod.
ALL TEMPERATURE READINGS ARE TAKEN AT THE TOP SURFACE OF THE TB.
Test conditions:
Temps taken using a Kessler ST652 INFRARED THERMOMETER
Outside temp is 70 deg
Temp at TB is 84.5 deg
Car has not been running but has been sitting in the sun for a few hours. So the temp degree difference is expected.
Control conditions:
Car is started and A/C is on high.
Hood is open.
Waited until temp guage on dash got to normal operating range.
Took temp reading with car running at normal operating temp.
Again car is restarted and A/C on high and hood is open.
Waited again until temp guage on dash got to normal operating range.
Temp after DIY coolant bypass test:
As you can see there is a difference of 23 deg. before and after the mod. So does it work? I'd say so. The temperature stayed fairly consistant with the temp of the TB that I took while the car was not running.
Some may debunk these crude test results as a true air temp reading was not taken and the fact that the car was not driven. However, as a simple FREE mod.
This mod does reduce the temp of the incoming air. Since heat is the enemy when it comes to making power I think I'll stick with it.
Jeff.
My DIY CAI.
ALL TEMPERATURE READINGS ARE TAKEN AT THE TOP SURFACE OF THE TB.
Test conditions:
Temps taken using a Kessler ST652 INFRARED THERMOMETER
Outside temp is 70 deg
Temp at TB is 84.5 deg
Car has not been running but has been sitting in the sun for a few hours. So the temp degree difference is expected.
Control conditions:
Car is started and A/C is on high.
Hood is open.
Waited until temp guage on dash got to normal operating range.
Took temp reading with car running at normal operating temp.
Again car is restarted and A/C on high and hood is open.
Waited again until temp guage on dash got to normal operating range.
Temp after DIY coolant bypass test:
As you can see there is a difference of 23 deg. before and after the mod. So does it work? I'd say so. The temperature stayed fairly consistant with the temp of the TB that I took while the car was not running.
Some may debunk these crude test results as a true air temp reading was not taken and the fact that the car was not driven. However, as a simple FREE mod.
This mod does reduce the temp of the incoming air. Since heat is the enemy when it comes to making power I think I'll stick with it.
Jeff.
My DIY CAI.
with both hoses removed i connected the two points to each other by using a length of 5/16" hose with clamps on either end. to plug up the connections on the TB itself i used 1/4" vacuum caps.
every little bit helps!
sorry for the low quality of the pictures... i used my cell phone--but you get the idea.
Apr 27, 2007, 08:46 AM
#3
Evolved Member
Thread Starter
iTrader: (9)
Join Date: Jun 2006
Location: NH
Posts: 1,240
Likes: 0
Received 0 Likes
on
0 Posts
pinned FTW. i think this is just one of those little mods that anyone and everyone could benefit from. i never drive my car cold in the winter... i let it warm up all the time. mostly so i can get into a nice warm car, haha.
May 3, 2007, 01:09 PM
#6
Evolved Member
Thread Starter
iTrader: (9)
Join Date: Jun 2006
Location: NH
Posts: 1,240
Likes: 0
Received 0 Likes
on
0 Posts
score. pinned.
i just put everything together in one place and snapped some pics... if it wasn't for fourdoor explaining everything i probably wouldn't have felt too comfortable about doing it since i didn't know exactly how it worked.
i just put everything together in one place and snapped some pics... if it wasn't for fourdoor explaining everything i probably wouldn't have felt too comfortable about doing it since i didn't know exactly how it worked.
May 3, 2007, 01:13 PM
#7
Evolving Member
iTrader: (6)
Join Date: Apr 2006
Location: Orlando, Florida
Posts: 259
Likes: 0
Received 0 Likes
on
0 Posts
I did this and I actually used one of the stock hoses to cover up the metal hoses in the TB ( I just looped it from one to the other and used the factory clamps) and used the other hose (the longer of the 2) to connect the 2 points on the coolant lines without cutting anything.
Trending Topics
May 10, 2007, 12:02 PM
#9
Evolving Member
iTrader: (10)
Join Date: Feb 2007
Location: Torrance, CA
Posts: 151
Likes: 0
Received 0 Likes
on
0 Posts
Really the pics are just a reference. If you pop your hood and take a look, it's common sense. I couldn't really see where the pics were taken, but when I looked by the throttle body, i saw two hoses, one leading from the head to the throttle body, and the other from the throttle body to a metal tube back to the head. All you need to do is route the line from the head to the throttle body right into the metal line back into the head. Watch out for coolant spillage XD
May 23, 2007, 11:43 PM
#15
Evolving Member
Join Date: Feb 2007
Location: Lake Charles, LA
Posts: 207
Likes: 0
Received 0 Likes
on
0 Posts