Hi chaps, I just wanted to say that I’ve not abandoned this thread, I’m watching it evolve quite nicely. I think we should carry on this sort of combined effort to modify our cars together so that none of us feel like were on our own…
Anyway, yeah intercooling - its a blinking nightmare. I do a lot of development on cooling and intercooling for several major OEMs and I’d love to say that there were some really easy ways of sorting it but I haven’t found them yet…
Fans are often used behind intercoolers on cars with difficult packaging constraints although they can be self defeating too. Although they keep the air moving through the core at low vehicle speeds they will soon become a restriction as speed increases so you’ve got to be very careful about how and where you use them, they are really a last resort.
For our cars we wont be worried about slow hillclimbs with trailers etc so fans aren’t going to help, even the largest SPAL jobbies will struggle to get anything half decent at speed.
The airflow really has to be ducted onto the core very efficiently from an area which has a very large coefficient of pressure (ram air effect for want of a better word). The best CP on a cars is almost always the front number plate where it approaches 1, as you move to the upper grill on a saloon car it will drop to 0.6 and then outwards to the fog lights down to 0.4?
On the roof of the car the air pressure will probably be below atmospeheric, poss just turbulent eddies as the main flow will separate as it shears off the top of the windscreen. This is why the GT3 cars forward scoop makes such a difference.
I’ve not got much experience with the side scoops but from Bernards postings re audi in S2 it would appear that this is a good route. So my first gut instinct would be to add a large piece of brake cooling duct from the RH scoop into the chargecooler inlet duct and then to temporarily fix a GT3 replica scoop onto the roof.
The best way to test these ideas would be to take a car to a trackday at Snetterton/Donnington and stick a thermocouple in the chargecooler exit pipe to the plenum and note the readings at the end of the back straight?
The next step is to ensure that you are using the cooling are flow in the most effective manner. Intercooler cores are extremely complex beasties, there are several parameters which can be tuned to optimise the heat rejection. These include the height, width and depth obviously but also the inner tube dimensions are extremely critical. Quite often the cheapo off the shelf jobbies (Lotus one included) only have open oval tubes, these are not the most efficient but have low pressure drop and are easy to make. More expensive coolers are built up of stacks of plates and fins so the inner charge side is also finned. If you look at the chargecooler on a BMW diesel you will see such a construction. The pitch of these fins is highly influential to the performance.
There are companies out there who would love to make an optimised intercooler for us but I’d estimate that they would cost �750 each without end tanks… There are other companies who will do a fin/plate cooler with std fin pitches much cheaper but they may not be quite so effective… I’ll have to have a think about it but without any test data it will be difficult to make a decision.
The other method is air-water-air as per the Bemani. All the same optimisation can be done to optimise the fins of both the chargecooler but also the low temp rad in the nose and then the flowrate you need from the coolant circ pump… The beauty of such a system on an Exige is that you have a great source of high speed/pressure cold air…
Anyway, I’ve got work to do