Intercoolers

Chrispy · Post by **Chrispy** » 20 May 2005, 16:08

Which is the most effective one? The ones on the 405's (top of engine) of the ones on the Xantia's (near the rad)? Also, why the difference in design?
I've had both cars (late 1.9 TurboD 405 and currently a Xantia Mk2 TurboD) and I'd have thought, theoretically, that the Xantia's would be more efficient due to it's location. I've noticed both are heavily affected by warm weather and some people have said that the 405's unit is a more efficient one, if a little badly placed.
Comments on a postcard. [8D]

AndersDK · Post by **AndersDK** » 20 May 2005, 16:22

If you want to seriously dig into this, then try autospeed books : http://www.autospeed.com
Not free - but note that prices are in AUS$

Post by **CitroJim** » 20 May 2005, 17:49

Having had both, I think neither are well placed. The 405 one has a restricted airflow to it via the duct in the bonnet sound deadeding which goes flat and also suffers badly from heat-soak when the engine is hot and the vehicle is not moving. This, IMO, is very noticeable, especially when towing on a hot summers day in a traffic jam.
The Xant looks to be better placed in front of the water rad and it gets a full cold blast of cold air but it's very close proximity to the rad also causes plenty of heat-soak and unlike perhaps the 405, this heat-soak is ongoing due to hot water flowing all the time. Also, and this is just surmise as I've not owned my Xant long but when stopped the water temperature goes up more quickly on the Xant and takes longer to go down when you get moving. This may be caused by the fact that my rad matrix is a bit full of debris (this weekends job).
One thing that I do notice though is that the Xant has a far more sharply defined and noticable power band than the 405 which I find surprising considering my last 405 TD and my Xant have identical engines and injector pumps. So just maybe the Xant intercooler is a little less inefficient. The wording was deliberate as I think neither are well placed. It would be an interesting exercise to see if there were any difference in power, power band definition and lag if the intercooler was placed well away from all sources of heat. But where?

Post by **CitroJim** » 20 May 2005, 17:55

Just thought about this a bit more. The Chavs, as their latest fashion accessory, are spraying CO2 (dry ice) directly on their intercoolers for a claimed huge increse in power. It's called cryo2 IIRC. That would surely cure XUD heat-soak problems!!!!

ActivaV6uk · Post by **ActivaV6uk** » 20 May 2005, 18:07

The best system is at the front of the car, i.e Xantia this is because you get the maximum amount of cold air onto the intercooler directly and I seem to remember that all the radiator can transfer to the Intercooler is +10% of its temperature. if you look at all the sports car manufacturers they all place there intercoolers ware it is on the Xantia to help performance. the other thing is size, the intercooler on a BX/405/306 is very small compared to the one in front of a Xantia’s rad.
Jim get that rad checked, our 4 Xantia’s drop heat so fast you can see the needle on the dash drop like a stone until it hits 70-80 degrees when your doing anything like 30mph.
Andy

fastandfurryous · Post by **fastandfurryous** » 20 May 2005, 18:08

The location of the 405 intercooler is indeed fairly bad. A few years ago I modded a 405 1.9TD with higher boost, higher fuelling, and most importantly, a larger intercooler, mounted at the front, directly in the cold airflow. I also made a little mod to start the cooling fans in low speed whenever the car speed dropped below 5ish mph, so that the intercooler never got heat soak. The result was dramatic. although it was never dyno tested, I would have said it was pushing 120-125 BHP. Certainly it would leave a standard model for dust, and would even give the boy racers a run for their money off the lights. Timed at 9 sec for the 0-60 dash.
What was even more amusing was that it was an estate, and a tatty one at that! [:D]
Sold it ages ago though.

Chrispy · Post by **Chrispy** » 20 May 2005, 18:30

Hmm... Well, I found that my 405 suffered more on a hot day than the Citroen does, but only by a smidgen. The 405 loved cold days, and as soon as the air temp went above about 12 degrees the performance was badly degraded. The Citroen however doesan't get badly affected until above about 18 degrees in my opinion.
From what I've read, the 405 one does appear to be of better design, but they scuppered all that by putting it directly above the engine with no direct feed of fresh air (note Evo's etc with the intercooler fully exposed at the front). Why Citroen chose to fit a lower quality design in a better location is beyond me considering the engines are supposed to be identical. Perhaps body design restrictions are to blame?
With my Xantia having air con, there are effectively 3 'radiators' up front, for coolant, intercooling and condenser. In which case, having the intercooler up fron may be a worse idea as it may be exposed to even more heat?

jeremy · Post by **jeremy** » 20 May 2005, 18:35

Have a look at the Allard site loads of interesting information.
http://www.allardturbosport.co.uk/
jeremy

Kowalski · Post by **Kowalski** » 20 May 2005, 19:05

I'd agree with what has been said above about the Xantia placing being more efficient. When you are moving, the Xantia intercooler gets cold air, it only gets heatsoak when you are stationary, and when you're stationary you're not using boost are you? The top mounted intercooler is smaller than the front mounted one and it is in the warm air that comes out of the radiator. Everything in the engine bay gets heat soaked all of the time and when you stop moving the air stops moving through the engine bay and the heat soak gets even worse.
I've got two Xantias both with Bosch pumps, one has the electronic control the other does not. They have slightly different boost curves because one has a KKK turbo where as the other has a Garrett. Both Xantias can be affected by hot weather, BUT when they're down on power in hot weather it is a sign that the air filter needs to be replaced with a clean one because they get quite black and restrictive. Replacing the air filter completely transforms the car, they gain bottom end torque as well as top end power.

oilyspanner · Post by **oilyspanner** » 20 May 2005, 20:36

My top mounted intercooler certainly seems to benefit from having an air scoop mounted on the bonnet, the way that the forced air system via the bonnet liner works but is not very big in cross section, I am unsure whether to pick up a Xant one and fit it in front of the rad, i know Vanny has done this but I think quite a lot of hardware needs to be sacrificed for this.
Stewart

Kowalski · Post by **Kowalski** » 20 May 2005, 21:16

I'd read somewhere where one car uses the actual bonnet as the intercooler. The bonnet on that particular car is double skinned with insulation between the inner skin and the actual engine bay to stop heat soaking. It might have been a tuned "high performance" version of the Mazda 6 that had it done.

Chrispy · Post by **Chrispy** » 20 May 2005, 21:53

Does the Xantia intercooler go the full width of the front like the coolant one? I know on my g/f's old Astra TD, that one was a diddy one bolted onto the side of the rad. More of a token suggestion that a proper working item. Her car was terrible in warm weather apparently, even though we had changed the air filter.

Kowalski · Post by **Kowalski** » 20 May 2005, 23:54

The Xantia intercooler is full width, I think it may in fact be slightly wider than the radiator. In front of the intercooler is the evapourator for the air con (if fitted) and this isn't full width.
My Dad's Lancia had a part width intercooler which was side by side with the radiator and roughly a third to a half of its width, it had no problems with performance in hot or cold weather.

ActivaV6uk · Post by **ActivaV6uk** » 21 May 2005, 00:17

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Kowalski</i>

evapourator for the air con (if fitted) and this isn't full width.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
The condenser is full width on the xantia and 406, its very narrow though.
Andy

mrbump · Post by **mrbump** » 22 May 2005, 07:02

One thing to consider is the pressure differentials accross each 'cooler. The xantia one has basically the same high pressure infront of it and behind. The 405 one has the benefit of having a better presure differential when moving. The actual volume of the xantia one is also surprisingly low given its size. Its also a rare design that I assume to be the best for dissapating heat in little airflow. I don't like the xantia ic!
The 405 ic is actually a good design and flows well due to larger internal diameters. I have mounted a standard 405 ic on my zx at the front of the rad, as far away from it as possible. I have directed most of the bumper openings through it and then out through a slit cut in the flat undertray part of the bumper. I used foam wadding to block the path I wanted (its actually quite a tidy job). I used a bigger rad to compensate and also directed the rest of the bumper to it.
The autospeed site is a very good read for this stuff, If anyone wants an old article (up to about issue 300 i think) email me and I can send it to you as I bought am membership about 5 years ago.