matt_gsxr
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| posted on 9/2/12 at 06:55 PM |
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I read that the "recirculate air button" results in the inside warming quicker and so will your engine.
Maybe worth an experiment.
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coyoteboy
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| posted on 9/2/12 at 11:01 PM |
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quote:
Just a thought, would an engine be using more fuel than normal if it's moving? I know it revs a little higher at idle but when driving does that
actually make a difference these days?
I think all port injected engines require more fuel at startup to increase the fuel in the puddle at the back of the valves. Normally there's a
fixed quantity of wet walls with a steady rate of evapouration off the intake walls, when it's cold that fuel/air mix evapourates less freely,
meaning more needs to be thrown in to keep the engine running OK (amongst other effects). I THINK (though I'll have to consult my books) even
direct injection engines will require more fuel as the cold block/cyl walls will affect combustion quality in the cyls.
Recirc will indeed help as you are heating warmer and warmer air up to your target temp, instead of heating outside air from -10 to +25 constantly.
It has the minor issue that it tends to make you steam up a bit but it's good initially.
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nick205
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| posted on 9/2/12 at 11:40 PM |
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Someone above made the point that car makers have teams of trained, experienced engineers who develop these things under big budgets. This is true
and in reality I guess the diesel heater solution will be the best compromise (all design is after all a compromise) taking account of all aspects;
economy, reliability, cost etc.
On the other hand someone (Steve M?) also recalled the old method of drawing intake air over the exhaust manifold to prevent carb icing etc. (I
vaguely remember a childhood family car having this feature). Someone also mentioned the "recirculate" feature which helps warm the cabin
quicker and allows the engine to warm quicker.
Could the same principles not be applied by directing the coolant flow through the exhaust manifold to capture the heat and recirculate it back into
the block...?
(Of course this may already be widely done for all I know!)
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austin man
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| posted on 9/2/12 at 11:50 PM |
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water will always flow through the stat as a safety measure hence the small hole in them so water will get to the rad. There is also no doubt that the
extenal temperature will continue to cool the engine as it enters the engine bay and also flows arount the sump etc . Olser cars where supplied with a
grill muff for really cold winters which cut down air flow by 50 to 60 %. Ah the good old days when you could fix something without having to renew it
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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PSpirine
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| posted on 9/2/12 at 11:58 PM |
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One (of many) reasons why a water cooled exhaust doesn't work is that this issue mainly crops up on diesel engines which have a turbo. The
efficiency loss by cooling down the exhaust manifold (before the turbo) will be so great to make any temperature related fuel increase negligible.
Modern engines still have a warm-up rich map right up to running temp. Even at 70 degrees the car will use more fuel (we're talking a couple of
percent only but it still translates to real mpg loss) than if it's at running temperature.
Some other methods for getting more heat into the engine quickly are:
1) Block heaters - available from most manufacturers for cars sold in cold climates
2) Recirculate coolant in engine block only. This is slightly different to the "Recirculate air" suggestion above which has only a limited
benefit as there's still coolant going through the heater. If recirculating engine block coolant, then an electric heater element is required in
the heater unit to generate the heat for cabin. This consumes ridiculous amounts of electricity but works well for the few minutes it takes to warm up
the engine. It also means you can clear your windscreen instantly whilst the engine is warming up.
3) Heated catalysts. This doesn't heat up the engine any quicker, but heats up the component that most requires it at start-up. The majority of
emissions problems relate to start-up and warm-up. Again, these solutions tend to use ridiculous amounts of power (1-2kW).
A fuel burning heater, if fitted, is done so for a very good reason. They're not simple or cheap bits of kit even for the OEMs so it's
only done when required.
Also remember that depending on the homologation/economy cycles performed by OEMs, the fuel burning heater may not actually cause a drop in mpg as it
doesn't kick in on a combined cycle run, but only on start-up and in very cold climates. The start-up homologation requirement may well be NOx
related or a separate test.
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coyoteboy
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| posted on 10/2/12 at 12:03 AM |
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quote:
water will always flow through the stat as a safety measure hence the small hole in them so water will get to the rad.
The hole in the stat is generally about 1-2mm diameter and it's designed to ensure there's no air locks so that the stat always sees
block-temp water. That's why it's imperetive you install it with the hole to the 12 oclock position. You're likely to see flow rates
through that hole of about 0.5 litres a min, hardly additional cooling. It's _not_ there for safety to ensure the engine stays cool even if the
stat fails.
[Edited on 10/2/12 by coyoteboy]
[Edited on 10/2/12 by coyoteboy]
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