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#46 nurseholliday

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Posted 19 November 2007 - 08:12 PM

so you have tryed opening your bonnet at 50 mph to feel the rush of cold air coming in through the grill



Everyone who as ever driven around with their fresh air vent open or heater on would have some idea.

Similarly if you've ever been to a rolling road, or driven up a really steep hill, and noticed the how hot things get without the usual cooling effects of airflow when driving at road speed you'll have an appreciation of how effective a bit of a draft through the front grill is.




Bet we can keep this running for another week 'n still be no nearer a definitive answer.


Well my mini has the two fresh air vents hosed up differently. The drivers side is ducted via standard vent hosing from the grill whereas the passenger side isn't, it just draws air from the engine bay. The drivers side is understandably cold while the passenger side spits out warm/hot air depending on engine temperature.

Explain that one?

#47 nurseholliday

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Posted 19 November 2007 - 08:14 PM

Oh and I do appreciate the cooling capabilities of ambient air through the grill, my Mini readily heats up when standing still, however I still feel once the air has reached the carb it isn't as cold as it entered the grill.

Oh and all the RRs I've seen are done with the bonnet up to maximise effectiveness of the fan.

Edited by nurseholliday, 19 November 2007 - 08:15 PM.


#48 JetBLICK

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Posted 19 November 2007 - 09:12 PM

the passenger side isn't, it just draws air from the engine bay. The drivers side is understandably cold while the passenger side spits out warm/hot air depending on engine temperature.

Explain that one?
[/quote]


If you aint got the ducting on the passenger one then the reason its warm is because the heat is comming off the radiator under that arch :D

#49 paulrockliffe

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Posted 19 November 2007 - 09:27 PM

The cooling effect on the engine at speed is a result of air rushing over the fins on the gearbox, the box has fins on to increase surface area and, therefore, cooling of the engine oil. You can see the evidence fo this if you restrict the airflow over the gearbox by fitting a sumpguard. I'm not disputing that air rushing through the grill does have a cooling effect, but I'm not sure this is significant compared with the cooling of the gearbox, especially as the gearbox is a better structure for cooling the oil, which moves a lot of heat around the engine.

My understanding of most ducting systems outside of Max Power is that their effect is to reduce the turbulence of the air as it enters the carb, so that the carb can draw air more efficiently, which can then mix with fuel more efficiently and produce a more efficient/powerful engine. Any ducting that isn't sealed completely at the carb from will not produce a result because the pressure at either end of the tubing will pretty much be the same, so there won't be much airflow, even if there was, the air rushing through the grill and over the engine would cause too much turbulence for this air to get into the carb efficiently.

Worryingly there is a ducted car in one of the mags this month and the mag seem to be going along with the ram effect theory.

#50 nurseholliday

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Posted 19 November 2007 - 10:23 PM

the passenger side isn't, it just draws air from the engine bay. The drivers side is understandably cold while the passenger side spits out warm/hot air depending on engine temperature.

Explain that one?



If you aint got the ducting on the passenger one then the reason its warm is because the heat is comming off the radiator under that arch :D


So therefore that heated air is reaching the carb too no? Sorry to seem a little sarcastic earlier... I am open to other opinions.

I agree that a pressure ratio would make a cold air feed work a lot better than simple ducting. One of my friends used a small piece of hose to direct air from the driver's air vent ducting to the carb. That seems to be a better solution than the Frontflow product.

#51 JetBLICK

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Posted 19 November 2007 - 10:44 PM

Not really... mini's are kinda weird, compared to modern cars, in the respect that the fan is always on, and it kinda sucks hot air off the engine through the rad and out the passenger inner wing. Dunno if you've looked under you passenger wing before, but the hot air being blown through the rad is sectioned off from the rest of the engine bay by the inner wing (or flinch pannel i think they're called?) which then goes up into ur passenger air vent if you dont have the ducting on.

You should acctually have a cold air feed duct from that air vent to the front grill, it may have been taken off in your car.


As i said before tho... i'm all for the ducting to the carb if its a sealed system... just i dont believe simple ducting from the front of the car to the carb helps in any way. Its just my opinion tho, i'd, like i'm sure many people would, would love to see it tested on a rolling road and maybe i'll be proven wrong :D

#52 nurseholliday

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Posted 19 November 2007 - 10:51 PM

I'm intrigued to see if it's possible to make a sealed CAI for a carb then...

I do have the ducting going from grill to driver's vent but mine goes through the wing rather than through the engine bay like I've seen on a lot of Minis.

#53 chairchild

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Posted 21 November 2007 - 09:29 AM

it's possible, but again, all it would do is make fuelling more accurately possible - it WONT increase power, unless of course, your fuelling is set up so badly, that you're losing power as it is :)


So therefore that heated air is reaching the carb too no?


no - the air your carb gets, comes direct from the grille, it doesnt go through the grille, through the radiator, then back around the radiator, to finally get to the carb



Get your mini upto working temperature, then whilst getting a mate to rev the engine a little bit, put your hand in the drivers arch, and then the passenger arch.

Tell me, which one would be blowing out hot air :)




I'd disagree with the bunsen burner analogy because the engine is in an enclosed space. When you open your bonnet after your engine has been at operating temp does or does not hot air come out?

A correct analogy would be to put a bunsen burner in a small box (perhaps 15cm x 15cm x 15cm), allow it to heat up the air in the box, then pass your hand through.


Yes, that would be correct - if we were talking about airflow when at a standstill. When moving the air comes in through the grille, then it can escape either through the rad, or out at the bottom of the engine-bay






not trying to make an argument, just trying to give you a better understanding

#54 samwell

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Posted 21 November 2007 - 07:23 PM

has anyone considered how this magical air feed stays cold itself? Anyone who subscribes to the idea of lots of heat in a small engine bay makes air warm, what dyu think happens why you have the same temperature effecting less air.

At the end of the day, you unlikely to effect the pressure differential front to back and so the speed of the air will be roughly the same and probably alot more turbulent due the the fact that its just been through a corrugated tube. Edge effect anyone?

And who ever the guy who asked, going "why does it bother you blah blah" what the hell????? you asked a question in a technical section, you will get technical answers, and usual factually correct ones or at least answers based on sound theory.

If you want to know where to go shop, do it in the F'ing chat section.

#55 nurseholliday

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Posted 21 November 2007 - 07:41 PM

it's possible, but again, all it would do is make fuelling more accurately possible - it WONT increase power, unless of course, your fuelling is set up so badly, that you're losing power as it is :-


So therefore that heated air is reaching the carb too no?


no - the air your carb gets, comes direct from the grille, it doesnt go through the grille, through the radiator, then back around the radiator, to finally get to the carb



Get your mini upto working temperature, then whilst getting a mate to rev the engine a little bit, put your hand in the drivers arch, and then the passenger arch.

Tell me, which one would be blowing out hot air :P




I'd disagree with the bunsen burner analogy because the engine is in an enclosed space. When you open your bonnet after your engine has been at operating temp does or does not hot air come out?

A correct analogy would be to put a bunsen burner in a small box (perhaps 15cm x 15cm x 15cm), allow it to heat up the air in the box, then pass your hand through.


Yes, that would be correct - if we were talking about airflow when at a standstill. When moving the air comes in through the grille, then it can escape either through the rad, or out at the bottom of the engine-bay






not trying to make an argument, just trying to give you a better understanding


Points taken.




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