Author Topic: Warm air feed...?  (Read 1820 times)

Offline Winso

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Warm air feed...?
« on: 27 January 2007, 15:13 »
Car is a 1.8GL (SPI). I'm looking into to sorting out a cold air feed to the airbox but I'm not sure about the warm air feed. Some people say its essential some say its only needed in very cold conditions. I've read that without it carb icing is a real problem as the warm air valve/flange/door/whatever thing in the airbox is actually open 99% of the time. Ive also read people saying that they butcher it and turn the warm air feed into another cold air one without any problems at all. Could someone who ACTUALLY REALLY knows what they are talking about fill me in please?!
Anyway my plan is to cut a hole in the airbox for a cold air feed hose to somewhere near the front fogs. This means when the warm air feed is open the normal cool intake wont be closed as usual, so the warm air wont be AS warm as its meant to be. Anyone think I'll suffer from icing or any other probs?
 

Offline robster23

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Re: Warm air feed...?
« Reply #1 on: 27 January 2007, 19:45 »

Well all those people with induction kits don't have a "warm air feed" and they don't seem to have any problems. We live in the UK not in greenland!  :wink:  I suspect that you will find that it will all be ok.

Whether you have a cold feed or not, the other engine components will get warm due to their direct connection to the engine. I say A OK!

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Offline Hypermonkey

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Re: Warm air feed...?
« Reply #2 on: 27 January 2007, 23:48 »
Warm air feed is non essential. I run K&N 57i on mine and the warm air feed is just sitting on the side of the engine bay. It just pre-heats the air in cold starts with an airbox. Mine hasn't missed a beat without it on :smiley:

Offline EvilScotsman

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Re: Warm air feed...?
« Reply #3 on: 28 January 2007, 02:16 »
The Golf, like other big brand names is a "world car" - i.e. it's designed for a wide range of conditions, and is driven everywhere from Australia's baking heat to the blistering cold of Russia.

Lets be honest, in the UK we don't get extremes of temperature normally so this is just silly. How many flippin cars have you seen in golf+, max power, street machine, fast car etc wi cold air induction kits? If the warm feed was required then none of these cars would run right.

If you want a cold air feed then put one in and stop worrying about stuff like carb icing. You have, after all, SPI - Single Point Injection, no carb!

Ice only forms at very low temperatures. We might see those temperatures once a year for about two weeks.
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Offline Bazzer

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Re: Warm air feed...?
« Reply #4 on: 28 January 2007, 09:11 »
Temperature of the intake at high rpm will be a few degrees cooler than the surrounding air (wind chill factor) - that's how carb icing works.... And it still applies on any butterfly / choke valve, not just on 'carbs'.... I'd be careful chopping it right out cos it can happen.....

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Offline rubjonny

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Re: Warm air feed...?
« Reply #5 on: 28 January 2007, 14:30 »
Carb icing is only really a factor in carb or SPI engines, because fuel is mixed with air.  The vapourisation of the fuel combined with the narrowing of the venturi in the carb/spi makes the air temp drop drasticly and any vapour in the air can freeze.
With fuel injection engines the fuel is sprayed directly into the head so this isn't such a large problem.

The bottom line is, theres no real point messing about with cold air feeds on a 1.8spi, you wont see any performance increase.  Even fuel injection engines dont see much if any improvement, its only when you make pretty extreme modifications that you see a real benefit from induction kits and the like :)
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Offline AudiA8Quattro

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Re: Warm air feed...?
« Reply #6 on: 28 January 2007, 20:13 »
Basically as Jon says, just to add carb/spi have problems with freezing because the fuel injection takes place right at the top of the system,this is then subject to the venturi effect as stated above. If you watch an spi engine, you can actually see the fuel dripping onto the throttle body butterfly.
MPI systems inject the fuel straight into the inlet valve, or in new engines directly into the cylinder.
The reason MPI systems have a hot air feed is to stop the throttle body freezing, this is only likely to happen in extreme conditions, and the fuel won't freeze as its injected much further down the system.
Engines that don't have a hot air feed can also be fitted with a coolant heated throttle body.
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Offline rubjonny

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Re: Warm air feed...?
« Reply #7 on: 28 January 2007, 23:38 »
on a side note, after running my gfs 1.3 spi polo at idle for a short time with the airbox off, i could actually see ice building up on the throttle body butterfly :)
« Last Edit: 28 January 2007, 23:40 by rubjonny »
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