Recent Topics
Switching from Synthetic to Dino
by beadvised
4 minutes 31 seconds ago
Replacement exhaust manifold bolts
by barkingspider
22 minutes 9 seconds ago
Anode Rod - the CONCLUSION
by larryinnewyork
42 minutes 51 seconds ago
DIY pickup bed liner
by old1
Today at 04:49 PM
Hard on a cold engine
by Nissan101
Today at 04:43 PM
Oversizing oil filter.. Acura MDX
by 2K2AcuraTL
Today at 04:19 PM
Burned 3 quarts at a 5104 OCI!
by alaskanseminole
Today at 03:23 PM
Daytona 500..
by Warstud
Today at 01:26 PM
2014 Taurus
by crookedaxle
Today at 12:43 PM
93 GMC 454 TBI w/Castrol Edge Extended Performance
by crookedaxle
Today at 12:38 PM
Brand New 2016 F350 6.7
by RickV
Today at 12:27 PM
HDEO trends
by 4WD
Today at 11:59 AM
Cashiers asking you to donate for ___ charity...
by Mr Nice
Today at 11:54 AM
Oldsmobile 350 Rocket Motor
by Letsrunum
Today at 10:54 AM
Semi-auto AR-style shotguns?
by OVERKILL
Today at 10:49 AM
Dexos license # question.
by pbm
Today at 09:23 AM
Help! P225-use P235?
by Toto
Today at 08:51 AM
Pennzoil "GOLD" synblend 0w20
by car51
Today at 08:22 AM
S10 Lean
by dlundblad
Today at 07:52 AM
OAT anti-freeze?
by otis24
Today at 07:43 AM
Newest Members
banjobilly, droptail, Jaseb3, timberwolf531, dehudso
60657 Registered Users
Who's Online
100 registered (2K2AcuraTL, A1O, 2010Civic, 69GTX, 4WD, 10 invisible), 2222 Guests and 11 Spiders online.
Key: Admin, Global Mod, Mod
Forum Stats
60657 Members
66 Forums
261601 Topics
4316110 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: 18105
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 Offline


Registered: 01/02/04
Posts: 2369
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: 503
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: 4318
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: 915
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: 8384
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: 915
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: 8384
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: 15387
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: 10507
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#4 24210mi-Castrol Magnetec 5W30+ Fram Toughguard Filter 7317
2015 Forester 6MT 5Door, OC#7 50318mi-PEAK 0W20+Subaru Filter

Top
Page 2 of 2 < 1 2