Quote:
Originally Posted by euromodder
A diffusor would help with a sedan or a sloping liftback design, but it increases drag on a station wagon / break / estate kind of car !
I'd keep the belly pan more or less horizontal right up to the rear bumper.
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Ah, good to know, thanks
So I will bolt it to level of tow hook as that is lowest spot and it should be enough low to let everything living above it, then need to check front airdam that it is about to same level with splitter, when I get that far and it should be nice and straight route air to pass.
Sideskirts are perhaps then more important in STW design to keep air properly underside.
One thing I have still not quite decided is cooling of engine, I have now upper grille blocked, there is hole size of quarter for intercooler, lower grille has two holes, lower I have blocked, upper is open, cooling is enough now, but will not be when summer comes.
I plan not to increase holes at front, but I plan to change way air exits, I could make it exit upwards, or downwards, if I make it down, then airdam could be lower and belly pan under the engine bay would need to have holes where air could leave, it would be needed to have bit of bump front of holes at bottom side so that air could leave freely without air coming from front being disturbing, also such creates small vacuum that would help air to exit, same is with hood vent.
Natural direction of warm air to exit is upwards, proper location for exit vent is at front half of hood, at least that is what I have read, but that means more noise escaping from engine bay to pass trough windshield and less noise is one reason I'm modding.
Currently there is nothing under engine bay, so it might be little less cooling when I cover bottom of it, but maybe holes with bumps at front of them will be enough to restore cooling.
If not, then I just need to open up lower part of bottom grille, only hills are causing that heat to build up a bit, not very much, but a bit of increase over normal temp and it is now fridge temps outside.
Cooling is actually now bit too much and bit too little, it would be enough and too much if I would keep throttle at same position on uphills, but it would mean getting speeds so low that I would need to gear down and that kills fuel economy. Maybe need to have adjustable grille block too.
I should also monitor bit of intercooler temps to find out how much opening that needs as it does affect to engine temps too.
Oh yes, as this is diesel turbo will be on boost at certain rpm even without a throttle, diesel is squirted by amount of idle all the time, so as long as engine runs there will be some fuel burnt and together with rpm that seem to cause boost. That is at least what boost gauge shows.
Tuning is interesting part, getting all working right and together, like getting good cooling with minimal amount of added drag