5 Sep 2008

Our company began a 9/80 work schedule; 9-hr days with every other Friday off and today is our first Friday off – cool!

After some research I’ve backed away from using an air-to-water heat-exchanger in the engine compartment (for the turbo) with its associated pump and lines to the front where another radiator rejects the heat. These setups work great for drag-racing but for road racing they heatsoak and the overall efficiency takes a dump. Between that and the weight, expense and complexity, a straight air-to-air intercooler will be used, getting air from one of the side ducts. What’s unknown is how much airflow there’ll be.

It seems like it should be decent since there’ll be a belly pan under the engine and the windscreen and curved engine cover should create low pressure behind it. Also, with the side vents being immediately ahead of the rear fenders, there should be high pressure piling up ahead of them. “Should be” means I really don’t know for sure; if airflow is insufficient, there’s always the McLaren F1 solution. It has a horizontally-positioned engine compartment fan that sucks air from below the car into the engine compartment, blowing it out the back. Doing it that way, the fan could push/pull air through the intercooler at the same time. This means a constantly running heavy fan, something I rather avoid, so we’ll have to wait and see. One perk of the McLaren setup is that the fan generates significant downforce!

Yes, an F1/Atom type center-mounted engine air duct has been considered but doesn’t seem appropriate. Since the car will have a windscreen it may prevent the duct from working at all, then there’s my real reason: the bane of composite construction and having the rear view mirror completely blocked by the duct. I would find it very annoying. On the other hand, my brother says he uses only his side mirrors in his Stalker. Eh.

What the intercooler really does is break the mental block I’ve been wrestling with, how to handle the rear suspension. I had all but decided to use trailing + lateral links but it means there’s zero room for the intercooler (and air intake, and maybe an oil cooler.) This is pushing the design back towards having true A-arms located entirely behind the engine. Now if I could just get rid of the darn rocker-arms!

I’ve received a few notes that hint at, “What’s taking so long, when are you going to start cutting metal?!” As I’ve said, it’s much creating blueprints for a big building. Rushing at this points sets the stage for disaster when I get to the third floor and discover some dire mistake made in the foundation. It has to be right, carefully thought through now so I don’t screw myself later on. Doing this paid off big time with the Mini so I’m not rushing this.