Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
Water/air intercooling
We will be covering in a later issue of AutoSpeed what I am about to write about – so this is just a quick heads-up.
If you are developing a custom water/air intercooling system, here are some critical questions for you.
1. How can you bleed all air out of the system? Nearly all commercially available aftermarket water/air heat exchangers don’t have bleed fittings. If you are mounting these heat exchangers conventionally, eg horizontally, about one-third of the internal volume will stay full of air – not water!
2. How are you measuring pump flow? If your answer is to pull off a hose and direct it into a bucket, then almost certainly the amount you measure will not be correct. Why? Because pumps will often work differently when they are part of a closed system versus an open system.
3. Finally, is the pump flowing effectively – or is it cavitating? Of the three pumps I tried in my system, only one was effective in circulating water without any apparent cavitation.
Looking around the web at pics of custom water/air intercooling systems, I’d guess that many (most?) of these systems are operating below par because of these issues.
on July 1st, 2014 at 8:18 am
How did you know/test for the pump cavitating?
on July 1st, 2014 at 10:39 am
You could hear it making that characteristic noise – sort of, bobble, bobble. Reducing pump voltage (to slow it) made noise go away.
And also: pumping through just one heat exchanger (rather than both) also made it go away.
(I should add that this was all done without the engine running – you need to be able to clearly hear the pump.)
on July 13th, 2014 at 9:11 pm
Cavitation is bad news indeed.
I recently saw a genuine water pump from a Fendt tractor (German).
Cavitation had eaten a hole out the side of the aluminium body, and undermined the impeller.
The customer wanted us to weld the hole, till we explained how bad his housing was.