Throttle Body Coolant Bypass
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
I have tried to find out the conditions, where it even could occur (in real life). During wintertime here in Finland, temperature varies from 40 F usually down close to -30 F (not this winter, at least not yet), sometimes even a bit colder. That should be severe enough to cover a pretty wice variety of weather...
Intermediate
Joined: Jan 2009
Posts: 34
Likes: 0
From: Las Vegas Nevada
Okay the Throttle bodys are different mine only has the two outlets on the passenger side, the one for the vavle cover and another one below it which is going to the heater core,so I can just run that hose to the front of the intake and the other to the water pump for the bypass.
Instructor
Joined: Mar 2007
Posts: 173
Likes: 18
From: Edinburgh Midlothian
no icing of the throttle body in scotland, but i did regularly get icing of the carburetor on my 1970 454 vette, in the winter, but only from cold start, once the engine is warm icing doesn't cause major issues, but when it did happen it caused the throttle to stick open.
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
no icing of the throttle body in scotland, but i did regularly get icing of the carburetor on my 1970 454 vette, in the winter, but only from cold start, once the engine is warm icing doesn't cause major issues, but when it did happen it caused the throttle to stick open.
But with L98's throttle body, the gasoline is sprayed very much further, so gas vapourising isn't an issue.
Team Owner
Joined: Dec 2000
Posts: 21,094
Likes: 282
From: Phila., PA burbs
Pro
Joined: Jan 2009
Posts: 686
Likes: 4
From: Austin Texas
I know it goes against conventional wisdom of what I've seen written in lots of places, but I don't see the heated TB as being much of an issue, since even at low speeds flowing air at 50 cfm, the air doesn't have much time to heat up - the surface area of those walls that are heated is dwarfed in comparison to the temperatures and surface area inside the remainder of the intake passages - I'd focus more on lowering the temperature, and more particularly flow path, of incoming air by other means. At higher engines speeds it becomes even less of an issue. Same train of thought applies to re-location of intake air temperature sensor. Ideally, it should be located inside the manifold, if the intent is to measure the temperature of the air charge. If the intent is to measure ambient temperature, which is what in effect a relocation of that sensor to the air cleaner box accomplishes, to fool the ECM into providing a richer charge, then why not just relocate it so it senses ambient air by locating it in another location, such as the fenderwell ? I've left mine stock in both these regards.
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
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Instructor
Joined: Jul 2007
Posts: 132
Likes: 0
From: Austin Texas
"Throttle icing can be divided into two categories. The
first category is the adhesion of ice to the stationary
throttle bore wall and valve area after the vehicle has
been shut down after an extended drive. This icing is
typically called “soak icing”. This throttle icing condition
can cause the electronically actuated throttle to close
improperly thereby not controlling the air into the engine.
This lack of control in airflow can cause engine stalls and
idle instability issues. The ice formation in the throttle
can also occur during the operation of the vehicle with
the throttle at various positions due to a high incoming
moisture concentration. This type of icing is typically
called “run icing”. “Run icing” can cause the throttle plate
to stick in the open position, also resulting in the inability
to control air flow."
Complete paper:
http://delphi.com/pdf/techpapers/2008-01-0439.pdf
Burning Brakes
Joined: Feb 2008
Posts: 988
Likes: 7
From: Sarasota Fl
All right already, we know why GM ran coolant through the throttle body. Has anyone actually had the icing occur on their car (carburated apps. withheld)? If not, then we can say, from the extremely technical corvette forum survey, that icing is not going to be an issue for the OP as it hasn't been for anyone else in this thread.
The reason I did mine was so i could remove the TB without having to worry about coolant spilling all over the place. If it has the added effect of even a marginal increase in power or cooler running, then so be it.
Sorry for the rant,
Jonathan
The reason I did mine was so i could remove the TB without having to worry about coolant spilling all over the place. If it has the added effect of even a marginal increase in power or cooler running, then so be it.
Sorry for the rant,
Jonathan
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
Originally Posted by joecarter85
You should have worked for GM, you could have saved them a lot of $$ with your scientific research/results !!
All right already, we know why GM ran coolant through the throttle body. Has anyone actually had the icing occur on their car (carburated apps. withheld)? If not, then we can say, from the extremely technical corvette forum survey, that icing is not going to be an issue for the OP as it hasn't been for anyone else in this thread.
The reason I did mine was so i could remove the TB without having to worry about coolant spilling all over the place. If it has the added effect of even a marginal increase in power or cooler running, then so be it.
Sorry for the rant,
Jonathan
The reason I did mine was so i could remove the TB without having to worry about coolant spilling all over the place. If it has the added effect of even a marginal increase in power or cooler running, then so be it.
Sorry for the rant,
Jonathan
Instructor
Joined: Jul 2007
Posts: 132
Likes: 0
From: Austin Texas
Now, if I missed your point, tell me again ?
Advanced
Joined: Jun 2008
Posts: 63
Likes: 1
From: Pittsburgh PA
All I am trying to say is that the small sample sizes that we see here are not conclusive. Caution would be advised if you are driving your corvette in cold climates. IMO, there is no way that I would bypass the throttle body if I drove in the winter.
Clearly, the Delphi paper previously posted shows that freezing can happen.
I worked for Delphi for 10 years (and bailed before the bankruptcy). If a design works 99 out of 100 times, that's not good enough. A failure that could result in a safety issue is minimized to the greatest extent possible.
Until we get 1000 posts stating that they did the mod, and drove it in freezing temperatures for months on end, I'll remain an skeptic. Of course, the dead ones won't be able to report back....
Dale
Clearly, the Delphi paper previously posted shows that freezing can happen.
I worked for Delphi for 10 years (and bailed before the bankruptcy). If a design works 99 out of 100 times, that's not good enough. A failure that could result in a safety issue is minimized to the greatest extent possible.
Until we get 1000 posts stating that they did the mod, and drove it in freezing temperatures for months on end, I'll remain an skeptic. Of course, the dead ones won't be able to report back....
Dale
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
Don't confuse the issue, as your English is fine. It is your conclusions based off of 1 car in 1 country that is flawed. And from your "test findings", you are summizing that no conditions exist that warrants the need for the TB coolant passage because your car never exhibited iceing.
And was that throttle body structure from a L98 engine?
Last edited by Yorcci; Jan 19, 2009 at 04:34 PM.
Team Owner
Joined: Dec 2000
Posts: 21,094
Likes: 282
From: Phila., PA burbs
I might also add that both of my other vehicles (non-corvettes) have TBs that do not have coolant lines routed through them. I've never experienced icing in those either.
Pro
Joined: Jan 2009
Posts: 686
Likes: 4
From: Austin Texas
I wouldn't expect that un-doing the bypass to cause any problem, in most instances.
Understand, GM put the LT-1 in Firebirds, Camaros, Impalas, Corvette and the decision at some point was between having no throttle body heating and facing a possible vehicle recall (all LT-1's, even if only some experienced icing), or putting a couple extra hoses on and routing the coolant through the TB.
The issue wasn't the low probability of a given vehicle experiencing icing, rather, the costs for recalling more vehicles that ice'd, plus the negative publicity damage it would cause. For GM, the cost of a couple hoses was less and the decision was made, and no LT-1 vehicles have ever been recalled for TB icing.
Understand, GM put the LT-1 in Firebirds, Camaros, Impalas, Corvette and the decision at some point was between having no throttle body heating and facing a possible vehicle recall (all LT-1's, even if only some experienced icing), or putting a couple extra hoses on and routing the coolant through the TB.
The issue wasn't the low probability of a given vehicle experiencing icing, rather, the costs for recalling more vehicles that ice'd, plus the negative publicity damage it would cause. For GM, the cost of a couple hoses was less and the decision was made, and no LT-1 vehicles have ever been recalled for TB icing.
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
I wouldn't expect that un-doing the bypass to cause any problem, in most instances.
Understand, GM put the LT-1 in Firebirds, Camaros, Impalas, Corvette and the decision at some point was between having no throttle body heating and facing a possible vehicle recall (all LT-1's, even if only some experienced icing), or putting a couple extra hoses on and routing the coolant through the TB.
The issue wasn't the low probability of a given vehicle experiencing icing, rather, the costs for recalling more vehicles that ice'd, plus the negative publicity damage it would cause. For GM, the cost of a couple hoses was less and the decision was made, and no LT-1 vehicles have ever been recalled for TB icing.
Understand, GM put the LT-1 in Firebirds, Camaros, Impalas, Corvette and the decision at some point was between having no throttle body heating and facing a possible vehicle recall (all LT-1's, even if only some experienced icing), or putting a couple extra hoses on and routing the coolant through the TB.
The issue wasn't the low probability of a given vehicle experiencing icing, rather, the costs for recalling more vehicles that ice'd, plus the negative publicity damage it would cause. For GM, the cost of a couple hoses was less and the decision was made, and no LT-1 vehicles have ever been recalled for TB icing.
GM, like any large American corporation, has to deal with the legal guys and the bean counter guys! 
If you want to modify your car then do it. On the other hand, if you live close to the artic circle you may want to leave it as GM engineers designed it. 
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
So what if they did ice up? Just pop the hood and move them manually. I agree that it is very unlikely to happen but I wouldnt say its impossible. I havent bypassed mine because my hoses are still in good shape and I see no reason to mess with it until I need to.
Intermediate
Joined: Sep 2008
Posts: 40
Likes: 0
Don't bother with this "free" mod
So little hot coolant goes through the TB, there's more heat hitting the plenum from just under the hood. I did it and felt foolish after I saw the whole thing
This is an urban legend, IMHO
So little hot coolant goes through the TB, there's more heat hitting the plenum from just under the hood. I did it and felt foolish after I saw the whole thing
This is an urban legend, IMHO
