Date: Tue, 11 Aug 1998 01:42:40 -0400 (EDT)
From: Gary Henderson
Subject: Re: Inlet manifold temperatures
Hi Rienk
I have just remembered something about opening rear-lids for better cooling - VW Beetles were commonly seen like this in the early '70s, and a test reported in CCC mag proved that this was actually worse than leaving the lid closed. Adding struts to the hinges, to make the gap appear at the top of the engine-cover was a major improvement.
Certainly your test results show that a better radiator would not have helped Franka's car; it just needed a source of ambient air!
The Imp block, with its ribs etc is quite good at directly dissipating heat, which is unhelpful to warmup and also to the air going to radiator when working hard. The bloody great aluminium girder for the waterpump, poking out of the block into the fan airflow must also be significant.
Cheers
GaryH
Date: Tue, 11 Aug 1998 23:18:22 +0100 (WET DST)
From: rienk steenhuis
Subject: Re: Inlet manifold temperatures
hello gary
can't remember who told me but i think hearing somebody say to me that early imp sport engine lids had a much wider gap along the rear window than the later ones. i had hoped that the cold air coming over the top and along the sides would find its way in along the sides of the lid. it doesn't. i would like to know what happens with the air underneath the car since i that is the important bit. and would a front spoiler make a difference? i know lowering the imp seems to make it hotter. and no indeed, "an engine can't be coolled with hot air"
Date: Wed, 12 Aug 1998 02:05:59 +0100 (WET DST)
From: kenneth barlow
Subject: Re: Inlet manifold temperatures
Yes, lowering an Imp does make it hotter, and adding a front spoiler does too, but not as much as lowering it. I have put a spoiler on my car, and don't seem to have had any problems.
To see a pic of my car with spoiler go to http://homepages.ihug.co.nz/~kbarlow and follow the links to My Pride and Joy Kenneth
Date: Wed, 12 Aug 1998 07:09:35 +0100 (WET DST)
From: Gary Henderson
Subject: Re: Inlet manifold temperatures
Hi Rienk
I would expect an air-dam to help by lowering the pressure underneath, because the fan blows forward to discharge there, also it should mean only cool topside air reaching the rear intakes BUT it depends on where the fan sucks air from really!
Cheers
GaryH
Date: Wed, 12 Aug 1998 11:18:49 +0100 (WET DST)
From: Allan Duncan
Subject: Re: Inlet manifold temperatures
> can't remember who told me but i think hearing somebody say to me that early
> imp sport engine lids had a much wider gap along the rear window than the
> later ones. i had hoped that the cold air coming over the top and along the
> sides would find its way in along the sides of the lid. it doesn't. i would
It would make three fifths of bugger-all diference.
> like to know what happens with the air underneath the car since i that is
> the important bit. and would a front spoiler make a difference? i know
> lowering the imp seems to make it hotter.
A bit of Aerodynamics 101:
a) High speed air has a lower pressure than stationary air.
b) It is all relative - the car moving through stationary air (normal mode) or the air moving over the stationary car (wind tunnel).
From this, the air at the rear of the car is high pressure, the air under the car is low. Therefore the air flow over the engine comes from the back of the car, through the slots in the rear lid (the Sport has lots of extra ones, the standard car just the line below the number plate light), across the motor or through the fan and down past the drive shafts to mix with the lower pressure air flowing under the car and back out the rear, where some will go for another trip around the circuit.
Puncture an oil line under the engine, and the oil will end up on the rear window.
'Duck tails' on the rear lip of the boot lid are intended to break the regime into independant upper and lower portions, that have a side effect of keeping the rear window clearer of road grime.
I intend one day putting some panels on the rear suspension to improve the smoothness of the under-car flow, along with a U shape on its side on the radiator exit side the help the merging of the two flows.
Spoilers seriously disturb this rear-engine air-flow, and you will notice that the race-cars have air slots on the sides just forward of the rear wheels, and the hot air is then forced out the rear.