Recent Topics
How does this sound ?
by Ammofirst
09/22/17 07:10 PM
2014 Taurus low coolant
by cadfaeltex
09/22/17 07:08 PM
VOA for Pennzoil 5w-30?
by MikeB4rsk
09/22/17 07:06 PM
warning! 2006 mitsubishi outlander fuel pump repla
by kc8adu
09/22/17 07:04 PM
Mobil 1 AP 5w20 - 9,822mi 2014 Jeep GC HEMI
by mike718
09/22/17 06:57 PM
Puerto Rico aftermath
by madRiver
09/22/17 05:39 PM
Tires wear out faster when new?
by 2010Civic
09/22/17 05:05 PM
Fram Ultra now rated up to 20K miles?
by Matagonka
09/22/17 04:55 PM
Service Department Just Lied to My Face
by fenixguy
09/22/17 03:43 PM
a $79 appliance bulb
by chiefsfan1
09/22/17 03:20 PM
Castrol Edge Bio-Synthetic on Sale
by bigj_16
09/22/17 03:04 PM
Using up boat fuel
by otis24
09/22/17 02:51 PM
Recently retired after almost 26 years on the job.
by wtd
09/22/17 02:06 PM
One size fits all
by zipster
09/22/17 02:04 PM
Do you flush your power steering system?
by Diesel16
09/22/17 12:59 PM
Diesel P/U's Coal Smoking It from Stop Lights
by LoneRanger
09/22/17 12:51 PM
GM Oil Life Monitor - OCI With Synthetic
by ChrisD46
09/22/17 12:18 PM
adjust briggs clutch spring
by edwardh1
09/22/17 11:29 AM
6000 SYNSHIELD MAX MPG SAE 10W - 30 API FA - 4
by bigj_16
09/22/17 10:44 AM
Front differential fluid capacity for 2004 A4
by dlundblad
09/22/17 07:56 AM
Newest Members
shuvo, angelcar, ickkyi, JoV, fiat124
62906 Registered Users
Who's Online
102 registered (alphadog, 5AcresAndAFool, 01rangerxl, aba4430, Aichiguy, AandPDan, 12 invisible), 2036 Guests and 15 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
62906 Members
66 Forums
271235 Topics
4498481 Posts

Max Online: 3590 @ 01/24/17 08:07 PM
Donate to BITOG
Page 2 of 2 < 1 2
Topic Options
#4331916 - 02/17/17 11:23 AM Re: Why are IAC Valves Heated? [Re: SHOZ]
SteveSRT8 Offline


Registered: 10/10/08
Posts: 18530
Loc: Sunny Florida
Originally Posted By: SHOZ
Almost all throttle bodies are heated by the coolant. First mod I do is to bypass the coolant hoses.


Some things never change. In my old cars we often blocked the crossover in the intake that was filled with coolant to cool the intake charge a bit.

I had a drag car (400 Firebird) that would actually get the intake pretty cold under certain conditions, cold enough to help power a bit...
_________________________
"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix

Top
#4331920 - 02/17/17 11:29 AM Re: Why are IAC Valves Heated? [Re: artbuc]
nthach Online   content


Registered: 01/02/04
Posts: 2875
Loc: California
Old Mercedes or VWs with Bosch K/KE-Jetronic didn't have heated IAC valves nor heated throttle bodies(at least on VWs, the Mercedes K-Jet setups had the throttle body downstream from the fuel distributor/air flow measuring mechanism).

Top
#4332071 - 02/17/17 01:58 PM Re: Why are IAC Valves Heated? [Re: artbuc]
Kawiguy454 Offline


Registered: 06/01/15
Posts: 532
Loc: Arizona
Originally Posted By: artbuc
Originally Posted By: Tegger
Originally Posted By: Linctex
during the course of extreme temperature testing, someone felt it helped drivability in some way

It's meant to counter the icing that results from the venturi effect, something that can manifest at ambient temperatures well above freezing.


This is what I believe.


+1 icing ...My honda foreman 400 had an electric plug in the carb to combat icing and the wife's carburated Yamaha had the coolant plumbing. Remember Gasahol can absorb/carry water...

Top
#4332076 - 02/17/17 02:04 PM Re: Why are IAC Valves Heated? [Re: artbuc]
SHOZ Online   shocked


Registered: 06/28/03
Posts: 4911
Loc: Illinois
The only time I have personally experienced this is back in the early 80's I had a Triumph TR7 with 2 Stromberg side drafts. No coolant hoses but did have the exhaust manifold heater tube and regulator on it for the air cleaner. Which I had disconnected.

So driving down the highway once cold foggy morning the car kept going slower and slower. I finally stopped and figured it out. Just sitting with the engine off heated the sliders up enough to break the frost.

I also put a temp probe just in front of the throttle body on my Gen Coupe once and saw temps below freezing at about 40F, this was when the throttle was closed at high rpm.
_________________________
2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual

Top
#4332097 - 02/17/17 02:30 PM Re: Why are IAC Valves Heated? [Re: SHOZ]
artbuc Offline


Registered: 12/02/05
Posts: 1004
Loc: West Chester, PA
Originally Posted By: SHOZ
The only time I have personally experienced this is back in the early 80's I had a Triumph TR7 with 2 Stromberg side drafts. No coolant hoses but did have the exhaust manifold heater tube and regulator on it for the air cleaner. Which I had disconnected.

So driving down the highway once cold foggy morning the car kept going slower and slower. I finally stopped and figured it out. Just sitting with the engine off heated the sliders up enough to break the frost.

I also put a temp probe just in front of the throttle body on my Gen Coupe once and saw temps below freezing at about 40F, this was when the throttle was closed at high rpm.


Bought a brand spankin' new TR6 in 1974. Loved that car but it was an electrical/mechanical cluster [censored]! White with blue interior. Nice memory.


Edited by Bill in Utah (02/18/17 02:12 AM)
Edit Reason: Bypassing the censor

Top
#4332141 - 02/17/17 03:14 PM Re: Why are IAC Valves Heated? [Re: artbuc]
artificialist Offline


Registered: 09/23/07
Posts: 8440
Loc: Florida
My understanding was that by preheating the throttle body, it would heat the air/fuel mixture enough to help it vaporize in cold weather. That would reduce smog during cold weather. This is one of the reasons that many carb and TBI V8 engines had a coolant passage inside the intake manifold underneath the carb or TBI unit. Also, I think heating the throttle body was also an alternative to using air cleaners which had snorkels routed over the exhaust manifolds.

This was less of a problem with inline engines which had the intake and exhaust manifold on the same side of the engine. Radiant heat rising from the exhaust manifold was often enough to aid in preheating the cold air/fuel mixture.
_________________________
2010 Lancer Ralliart Sportback

Top
#4332214 - 02/17/17 04:49 PM Re: Why are IAC Valves Heated? [Re: artificialist]
artbuc Offline


Registered: 12/02/05
Posts: 1004
Loc: West Chester, PA
Originally Posted By: artificialist
My understanding was that by preheating the throttle body, it would heat the air/fuel mixture enough to help it vaporize in cold weather. That would reduce smog during cold weather. This is one of the reasons that many carb and TBI V8 engines had a coolant passage inside the intake manifold underneath the carb or TBI unit. Also, I think heating the throttle body was also an alternative to using air cleaners which had snorkels routed over the exhaust manifolds.

This was less of a problem with inline engines which had the intake and exhaust manifold on the same side of the engine. Radiant heat rising from the exhaust manifold was often enough to aid in preheating the cold air/fuel mixture.


What about the IAC valve?

Top
#4332380 - 02/17/17 07:51 PM Re: Why are IAC Valves Heated? [Re: artbuc]
artificialist Offline


Registered: 09/23/07
Posts: 8440
Loc: Florida
Originally Posted By: artbuc
Originally Posted By: artificialist
My understanding was that by preheating the throttle body, it would heat the air/fuel mixture enough to help it vaporize in cold weather. That would reduce smog during cold weather. This is one of the reasons that many carb and TBI V8 engines had a coolant passage inside the intake manifold underneath the carb or TBI unit. Also, I think heating the throttle body was also an alternative to using air cleaners which had snorkels routed over the exhaust manifolds.

This was less of a problem with inline engines which had the intake and exhaust manifold on the same side of the engine. Radiant heat rising from the exhaust manifold was often enough to aid in preheating the cold air/fuel mixture.


What about the IAC valve?


Heating the IAC valve would still heat the air fuel mixture at idle to reduce smog at low temperatures.
_________________________
2010 Lancer Ralliart Sportback

Top
#4332589 - 02/18/17 05:53 AM Re: Why are IAC Valves Heated? [Re: KrisZ]
Merkava_4 Offline


Registered: 01/30/07
Posts: 16264
Loc: Clovis, CA
Originally Posted By: KrisZ
Most of the time, this emotionally driven behavior causes more harm than good.


LOL

Top
#4335691 - 02/21/17 11:33 AM Re: Why are IAC Valves Heated? [Re: artbuc]
ARCOgraphite Offline


Registered: 05/17/09
Posts: 11183
Loc: N.H, U.S.A.
My 8HP Tecumseh Snow king engine has a heated carb I think.
On most engine, There is not enough surface area in the TB to provide significant heating of the air column. I would most assuredly say it is to prevent icing at the tb at idle and light throttle where there is a lot of gas cooling due to a "refrigeration cycle" occurring around the throttle. The IAC is usually nearby, and the IAC is a throttle bypass subject to freezing as is the main throttle.
_________________________
2014 Nissan Rogue S CVT, OC#7 29472mi-QSUD 10W30 + M1 110A Filter; 2017 Subaru Crosstrek CVT 4762mi-SOA 0w20 + SOA Filter

Top
Page 2 of 2 < 1 2