CSR rad air outlet on nosecode........what's the point?

[Martin S.]

Does anyone know the design rationale behind this as I'm struggling to see the point

 

Class 4 Zetec

[Dickie Normuss]

My understanding was that all of the air that passed through the rad was directed out through this hole to keep the under bonnet temps down.

 

VX HPC - Loud and proud here

Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere

[k80rum]

I thought its primary function was to vent the heated air from the radiator out of the engine bay rather than exhaust it over the engine and through the tunnel.

 

Darren E

 

K80 RUM Website and Emerald maps library

 

Home of the long-term, supercharged Duratec project

[CSR Phill]

Rumour has it that ...."and a new larger nose-complete with floor mounted chin, underside air intake and top air outlet duct to improve airflow -combine to reduce front end lift by 50%, which increases high-speed understeer" from the Caterham sales blerb.

[Dickie Normuss]

Silly me, I thought it was to stop your feet from melting 😬

 

VX HPC - Loud and proud here

Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere

[Martin S.]

I would have thought the contribution to underbonnet temps from the radiator air would be small compared to the heat generated by the engine/exhaust etc....but I guess every little bit helps.

[Mickrick]

I undestood that ducting the air out of the top of the nosecone, increased underbonnet temperatures. hence the problems with hot footwells, as there's less air flowing through the engine bay.

 

[millsn]

My guess is that all the inboard suspension gubbins gets in the way of the usual airflow route and thus venting the top of the nosecone allows post radiator air -out.

[Irrelevant]

You're all wrong . . . primary function is to look cool. All the techno-babble is so pixie boot wearing bearded folk will have something to talk about over half a pint of real ale

[paul jacobs]

Well, I removed mine for a year and didn't notice any difference, good or bad, so put it back again and still didn't notice any difference. At least with it in, it stops the water coming in through the top vent, onto the suspension and damaging it

 

And BTW Adam, with my dainty size 8 feet, I don't need to wear those silly pixie boots, 😔 but I do have to own up to a beard though 😬

 

Paul J.

Waiting to get my CSR back with it's new and remapped Omex ECU

[Normans_Ghost]

For what it's worth it's my belief that on a standard (non CSR) vehicle the problem is that you have a huge duct which, at speeds over 40 mph, is drawing in huge volumes of air. So far so good. But where does all this air go. The only exit route is down the transmission tunnel. However this escapse cannot cope with the volume of air being pumped in. So the air pressure under the bonnet builds up to the extent that it becomes near equal to the pressure on the forward side of the radiator and air flow through the rad is now equal to the airflow down the tunnel. To aggrevate the situation this air will be hot, not cool.

 

The reusult of this is the engine heat rises, the gearbox gets hotter that in otherwise would and the footwells get so hot that feet in thin shoes can get burnt.

 

The answer to the problem is to create a larger exit for this volume of air to escape.

 

The solution I came up with (and there may/will be others) was to create a lip at the edge of the bonnet in front of the aeroscreen. I had done some tests prior to this modification. I needed to find the low pressure point of the bonnet. I stuck tufts of cotton wool to the bonnet and observed the behaviour of these tufts at 60 mph(100 kph). All the tufts over the front and centre of the bonnet were being pressed down by the air pressure. The tufts at the rear edge were waving freely in the wind, thereby indicating that this area was, indeed, in a low pressure area.

 

I then made to cuts in the rear edge of the bonnet, each 2" long where the curvature of the bonnet become straight. I then cut 3 "U" shaped sections of carbon and screwed these into the scuttle where the bonnet closes. Fitting the bonnet now creates a lip which ressembles a NACA duct.

 

Before carrying out this mod I could not get my engine temperature below 80-85c (I run a 74c thermostat), the gearlever would get so hot it couldn't be touched and the footwell was uncomfortably hot. Also the jet of hot air coming through the "mesh" gear lever gaiter was akin to a hot air dryer.

 

After the mod the engine temprature is 70 -75c, the gearlever is tepid, the hot air dryer has ceased and the foortwells are cool. If I'm in heavy traffic the engine tempratures rise, as would be expected. However, the temperature falls back to 70-75c in a minute or two when on an open road again.

 

The temperature gauge is a capillery type, the car is aeroscreened and the bonnet (as is the rest of the body) is carbon. I cannot say that this will work with a screened car but suspect the low pressure may be greater due to the extra swirl caused by the screen.

 

The CSR arrangement is akin to an Elise radiator arrangement. On an Elise it works very effectivly.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[john milner]

I think it is mainly to do with aerodynamics. The front is a brick shaped air intake. By having an easy exit the pressure on the front will be reduced.

A secondary benefit will be that more cool air can get through the radiator so the coolant will be cooler. The bay temperatures are probably higher due to the reduced airflow. Engine temperatures in theory should not be any higher as the thermostat will be open more and the fan will be on more.

[Normans_Ghost]

But 11884 (I am not a man, I'm a number) the CSR owners I've spoken too have all complained of excessive heat in the footwells. And the CSR's seem to have lots of insulation material on the engine side of the footwells.

 

Need a CSR owner prepared to experiment with their bonnets.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[john milner]

I didn't know what to type when I set the account up and can't be bothered to get it changed.

[Normans_Ghost]

Why not put some info in a a signature.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[CSR Phill]

Yes the underbonnet gets hot and that can relate to high footwell temps and the exposed chassis tubes could take your skin off. However lagging the primaries solves the problem to a great extent. The only problem I have is I suspect the cooked electronics under the bonnet can give some strange problems ie. my car won't restart when hot.

[Normans_Ghost]

It's not good practice to lag primaries. The heat is moved down the pipe (good) and up the pipe into the head (bad) Can lead to burnt exhaust valve seats.

 

Before you all shout at me that the racers do it, they rebuild every year.

 

The answer must be to stop the heat build up under the bonnet in the first place, not attempt to do something with it when it's there.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited

[Jason Plato]

valve regression is not an issue with lagging the primaries on modern aluminium heads such as K series and duratec. I've been lagging for 12 years and in that time I have measured and monitored 6 heads - none of which suffered valve regression due to heat. And my exhaust silencer doesnt burn out quickly either and my feet are cooler. How many examples of valve regression have you seen Norman ?

 

here is C7 TOP

Taffia joint AO with Al

 

[Normans_Ghost]

One or two, but on leaded heads. Definatly seen several with signs of excessive overheating. Had an MG Midget in the workshot some years ago where the head had gone blue.

 

Irrespective of the material it must get hotter than it was designed for.

 

^{Norman Verona, 1989 BDR 220bhp, Reg: B16BDR, Mem No 2166, the full story here}

You and your seven toThe French Blatting Company Limited