‘74 DS Resto

faulksy

Active member
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You can just about see how far up the manifolds I went. The wrap stops just after the bend on both of the manifolds.

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Getting a decent photo of the two allen head bolts was a challenge. I only swapped those two as that part of the flange is flat and getting to the nuts on those studs is the hardest. The other two aren't to bad to do up with a short 1/4' ratchet.
 

Ramaling

Member
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51221822123_fc12071978_b.jpg


51222375629_6b1db3d0c4_b.jpg


You can just about see how far up the manifolds I went. The wrap stops just after the bend on both of the manifolds.

51222684665_0e9b8b0c89_b.jpg


Getting a decent photo of the two allen head bolts was a challenge. I only swapped those two as that part of the flange is flat and getting to the nuts on those studs is the hardest. The other two aren't to bad to do up with a short 1/4' ratchet.
Energy i.e. heat cannot be destroyed. It must go somewhere and so insulating these pipes will convey that energy back to the head and down to the down pipes. Going towards the head would worry me. These cars already have poor heat flow options.
 

faulksy

Active member
Couldn't agree more Ramaling, getting rid of the heat isn't an option so it's a case of managing it. That's why the dowpipes are only wrapped where they pass very close to the frame, steering column and starter motor wiring. The idea was not to eliminate the radiant heat but to move it away from a few key items. The majority of the manifolds is left exposed to dissipate heat without pumping it back into the head.
 

Buttercup

Well-known member
To a large extent this was done by the heat shields.
Aluminium shields lined with asbestos were widely used in the original DS19.
Later steel versions were not as effective, and often left off after maintenance.
As most of you know, I advocate the enhancement of under bonnet air flow, and the transfer of heat into that flow for removal.
I do not favour exhaust wraps nor ceramic coatings, as they reduce the transfer of the heat to the air flow.
I do not favour thick insulation on the engine side of the firewall as it restricts the air flow. A thinly insulated shield is ok.
 

Glenn Drake

Member
I been thinking about redirecting the fresh air tubes (that go to the heater box LHS and fresh air fan box RHS) to push fresh air into the engine bay.
I NEVER use the heater (quite warm enough 😊) and the fresh air fan has really limited functionality as if it’s really hot then it effectively just blows warm air!).
I also feel that the seal rubber between the bonnet and windscreen just traps hot air rather than allowing it to naturally flow out at this highest point of the engine bay.
I plan to play around redirecting the air into the engine compartment using the two fresh air tubes.
Anybody else played around with this?
 

forumnoreason

1000+ Posts
nup, but I've got the DS in Asia title (book) and lots of cars on subcontinent, India, Thailand etc people have chopped out sections of undertray and plate holder to let more air in! Even the bonnet.
 

DoubleChevron

Real cars have hydraulics
nup, but I've got the DS in Asia title (book) and lots of cars on subcontinent, India, Thailand etc people have chopped out sections of undertray and plate holder to let more air in! Even the bonnet.
I don't think touching the bonnet will work. Most of that is a high pressure zone, so you will exacerbate cooling issues (the vents will pressurise the engine bay, so will stop air flow through the radiator). At standstill in traffic they would help.
 

Ramaling

Member
I don't think touching the bonnet will work. Most of that is a high pressure zone, so you will exacerbate cooling issues (the vents will pressurise the engine bay, so will stop air flow through the radiator). At standstill in traffic they would help.
Interesting comment however I was thinking a bit differently. The front 50% or so of the bonnet is curving upwards which causes an airflow divergence from the underside of the car. I would have thought this causes a low pressure zone over the curved section. The windscreen being very steep would act as an air dam possibly with a "roller" forming down around the windscreen wipers with the possibility of high pressure in this region.

So I would have thought, from a purely technical point of view, rear facing louvre vents on the front half of the bonnet would suck a lot of air out especially if a modest air dam was added underneath. Now all of this from an aesthetical point of view would look awful so I'm not about to commit to the idea.

Also, from the same aerofoil analogy, the front underside where the air intake is placed is in a high pressure zone.
 

DoubleChevron

Real cars have hydraulics
Interesting comment however I was thinking a bit differently. The front 50% or so of the bonnet is curving upwards which causes an airflow divergence from the underside of the car. I would have thought this causes a low pressure zone over the curved section. The windscreen being very steep would act as an air dam possibly with a "roller" forming down around the windscreen wipers with the possibility of high pressure in this region.

So I would have thought, from a purely technical point of view, rear facing louvre vents on the front half of the bonnet would suck a lot of air out especially if a modest air dam was added underneath. Now all of this from an aesthetical point of view would look awful so I'm not about to commit to the idea.

Also, from the same aerofoil analogy, the front underside where the air intake is placed is in a high pressure zone.

you would need to run over it with a manometer no doubt... if its anything other than a negative pressure, you're going to hinder not help :)
 

faulksy

Active member
You'd have to cut the louvres into the back half of a DS bonnet as the front half is ahead of the radiator. Another option I've heard of is cutting the bottom out of the front wings between the wheel arch and back edge. It would also make getting tools back a lot easier as there is no way of getting into that area without taking the wing off.
 

KAndy

Member
Mine has similar vents (see attached), apparently a Queensland thing done to aircon models.
No idea if it makes and difference...
 

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fritzelhund

Well-known member
In period a study was undertaken by the local QLD agent. The airflow inside the DS engine space does not flow out the rear. Incoming air enters then changes direction and goes forward again. It was common practice to add vents rearward the front wheels but they also need some way to pass air from inside the engine space, so it is likely the inner walls of the wings are also modified with holes at about the level of the mounting points. My DS23 B/W injection was supplied by Citco in Sydney and was modified with a hand sized hole cut in the inner wings....but no outside vent.. It was common practice to remove the rubber sealing strips that go between the wings and the front bumper under the headlights in order to add more potential throughput of air in the style of first nose cars. Depending on the fitment the cars came with slotted front bumpers and louvres on the vertical trailing surfaces for the two aircon condensers which themselves had electric fans. None of which helped much when heaps of hot air would enter the cabin via the steering column tube hole and the dreadful disintegrating foam lined cardboard tubes from the front bumpers to the dash vents were either crushed or badly fitting. The first nose cars ( while only having half the power .. read heat ... from the engines ) were far cooler because of greater airflow and far less heat sink. It should be remembered that the radiator duct sources its air from just above the road surface which is subject to solar heating in the tropics too. Even the clutch pedal/ parking brake pedal and cable were responsible for heat transfer into the cabin.
 

Buttercup

Well-known member
The 1961 cendrier (? Spelling) vents in the top of the front wings were possibly a good idea.
Remembering that the 1st front cars did not have a closed duct in front of the radiator, and the front wings were used to carry cabin air from the bumper to the firewall, without cardboard tubes, the cendrier vents had a channel below them to take engine bay air.
Although they did not fix the particular problem that they were intended to, they were probably of benefit to engine bay temps overall.
I think that louvre vents at the rear corners of the bonnet would work well.

More research is required.

I have a couple of damaged bonnets that I could do some experiments with.
 

fritzelhund

Well-known member
Back in the day someone experimented with removal of the rubber flap seal around the rear edge of the bonnet .. logical enough but it was unsuccessful as heat and hot oily/petrol smells were then able to enter the cabin when the front windows were down. Bob, IIRC the cendrier vent were an attempt to reduce underbonnet hydraulic fluid heat. There was a DS 19 wandering around Brisbane in the mid 60s that had an extra cooler ( a small aftermarket radiator like is added to modern auto transmissions ) mounted under the spare wheel tie bar. Seemed an elegant and sensible solution to a problem that probably became redundant with the adoption of LHM
 

Greenpeace

Active member
She’s a 5 Speed manual, Weber Carby and all plumbed for aircon but missing the compressor - something I’ll have to hunt down...
I’m going to have to read up on posting better images...
Hi KAndy,
I found the easiest way with photos is to simply send them to yourself via text, (they are automatically resized when you text them). Then just save the received images to your device ready for attaching to your posts. I do everything on my phone so everything is handy (original photos/resized photos etc).
Rob.
 

Buttercup

Well-known member
Back in the day someone experimented with removal of the rubber flap seal around the rear edge of the bonnet .. logical enough but it was unsuccessful as heat and hot oily/petrol smells were then able to enter the cabin when the front windows were down. Bob, IIRC the cendrier vent were an attempt to reduce underbonnet hydraulic fluid heat. There was a DS 19 wandering around Brisbane in the mid 60s that had an extra cooler ( a small aftermarket radiator like is added to modern auto transmissions ) mounted under the spare wheel tie bar. Seemed an elegant and sensible solution to a problem that probably became redundant with the adoption of LHM
Yes, the cendrier was an attempt to reduce hydraulic fluid temp....... by improving general air flow.
However, they then made two discoveries.
The radiator air was recirculating when the car was standing still, so cooling was greatly impaired.
And a large part of the hydraulic fluid heating was coming from the combined engine coolant pump/ hydraulic low pressure pump (used to regulate the gearshift speed)
The heat was transmitted from the coolant to the hydraulic fluid via the aluminum body housing the 2 pumps.

So...... with the second front cars, the radiator got an inlet duct to stop air recirculation.
And the speed regulation of the BVH was replaced by the centrifugal regulator system.

So the experiment of the cendrier was only used for one year of production.
I suggest it was probably a very good way to improve the general air circulation.

From many years of building and flying model aircraft, I learned that engine cowls need to be designed carefully so engine cooling was not reduced.
The rule of thumb, was that air exit area needed to be 2 x times the inlet area.
As the cool incoming air is heated it expands, and the exit space needs to be more. Also a continuously reducing pressure gradient is needed to maintain flow through. The exit must not restrict the flow.
In a Dee I believe there is plenty of inlet area, it's the exit that is lacking.
While it may have been found that a significant amount of the air moves forward again to exit, I'm sure this is not how it should be. The best flow through would be achieved with BIG vents in the rear parts of either the bonnet or wings.

Cendriers are the only genuine original factory accessory to achieve it.
 

Greenpeace

Active member
How about a pair of bilge blowers connected to either vents or some sort of apertures leading out of the engine bay? 4" ones are rated at 200 cfm + which is around 6 cubic meters of air a minute (each). You can pick them up for $35 or so on EBay so it would be cheap experimentation. One would think it would have to have some sort of cooling benefit, particularly when stationary? Maybe plumb them into those rubber flaps that lead into the wheel arches so you're not chopping holes (in case it doesn't work😁). I believe the inside of wheel arches are negative pressure areas at speed? The blowers also come in 3" but obviously these flow less air than the 4" ones.
If one was to louvre the bonnet like in one of the images in an earlier post, wouldn't mounting thermo fan/s on the underside (space permitting) be of extra assistance to heat removal, particularly at standstill or low speed?
Rob.
 

Buttercup

Well-known member
How about a pair of bilge blowers connected to either vents or some sort of apertures leading out of the engine bay? 4" ones are rated at 200 cfm + which is around 6 cubic meters of air a minute (each). You can pick them up for $35 or so on EBay so it would be cheap experimentation. One would think it would have to have some sort of cooling benefit, particularly when stationary? Maybe plumb them into those rubber flaps that lead into the wheel arches so you're not chopping holes (in case it doesn't work😁). I believe the inside of wheel arches are negative pressure areas at speed? The blowers also come in 3" but obviously these flow less air than the 4" ones.
If one was to louvre the bonnet like in one of the images in an earlier post, wouldn't mounting thermo fan/s on the underside (space permitting) be of extra assistance to heat removal, particularly at standstill or low speed?
Rob.
If you had significant louvres, at standstill normal convective flow would be adequate.
I don't think there is any need to add fans, which add energy into the air, just let the hot air that is there, out.
 
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