[Gmecm] TBI and EFE

[Programmer]

For icing--all you need is the correct pressure drop across the throttle 
plates and humidity levels that contribute.
I've seen idling TBI trucks with frost on the blades at 48F.

Lyndon. (Canuckian)...

----- Original Message ----- 
From: "Jared Ryan" <jryan at caminofx.org>
To: <gmecm at diy-efi.org>
Sent: Friday, December 01, 2006 12:06 PM
Subject: Re: [Gmecm] TBI and EFE


> I've never actually seen a carburetor ice, but I don't doubt that it can 
> happen.  It just doesn't freeze that often here - but it would only take 
> once to cause a problem for me.
>
> This is going to be my project this weekend.  The temperature is flirting 
> dangerously with freezing in the early mornings.  Thankfully, the 
> relatively humidity is low for once.
>
> On Fri, 1 Dec 2006, Rick McLeod wrote:
>
>> J, even on my TPI's that are a 'dry' manifold, there is a TB pre-heat w/ 
>> a water passage bypass from the cooling system, I disconnect it in 
>> summer, but it makes a big difference in city drivability if not 
>> connected in winter!
>
> I'd recommend having it, maybe you remember the old VW's w/ the carb 
> preheat tubes from the past, they had a weighted flap that could be 
> 'locked' open in summer, but the owners manual recommended not doing that 
> 9 months out of the year, yes the cold/cool ones, I've seen ICE form on 
> the carby in them!
>
> Humid cool cliamate, like Houston when temp dips, I'll bet you're icing up 
> a little, doesn't take much!
>
>
> ----- Original Message ----
> From: Jared Ryan <jryan at caminofx.org>
> To: gmecm at diy-efi.org
> Sent: Friday, December 1, 2006 12:28:24 PM
> Subject: [Gmecm] TBI and EFE
>
>
> Do TBI engines typically need the EFE ThermAC setup to run smoothly in 
> cold weather?
>
> I have an El Camino that has a heat stove on the passenger side, but I 
> recently changed to a Camaro air cleaner that puts the snorkel on the 
> driver side (this fits MUCH better with my Camaro serpentine belt setup). 
> I will need to put a heat stove on the left-side exhaust manifold in order 
> to use the ThermAC.
>
> I assume it wouldn't be there (on '88-'92 TBI F-bodies) if it didn't help. 
> It made a BIG difference in cold-weather running when I had the QuadraJet 
> carburetor, and TBI is also a wet-manifold system.
>
> The reason I ask is that the temperature has dropped into the 30s F, which 
> is cold for Houston, TX, and the idle is a little rough.  However, the 
> cold weather moved in on the same day I removed and cleaned the IAC valve. 
> It is entirely possible I just need to reset the minimum-air setting and 
> the idle will smooth out.
>
> Off-idle performance has been perfect, just a little bit of a rough idle 
> since it turned cold.  I will do the IAC reset this afternoon, but I still 
> wonder if making the ThermAC operational will help a lot.
>
> I notice that the TBI intake manifolds no longer have the exhaust 
> crossover under the carburetor/throttle body mounting pad.
>
> I hear a lot about ThermAC, like "It only closes in *really* cold weather. 
> When I had it set up properly with the QuadraJet, it would close at least 
> a little bit on sunny warm spring days!  It would open quickly, but it 
> didn't only work on very cold days, for sure.  On very cold days, like 
> what we have here, it often wouldn't ever open completely.
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