Re: TD5 TDI intercoolers
On 2005-03-12, Austin Shackles <austinNOSPAM@ddol-las.net> wrote:
> AIUI, the point about increasing the intercooler size is that it
> allows you to increase the boost pressure, which in turn may require
> pump (or ECU, as may be) tweaks.
There's a little more to it than that, the cooler the air the better
the mix burns and the more power you get as a result, plus of course
you can get more air in there at the same pressure than you can if the
air's warmer. As the air expands when it's hot a pipe at 1 bar
pressure will hold less hot air than it would hold cold air, so
without altering the boost pressure you get more air into the
cylinders. Slightly unintuitive perhaps... On my plastic rocket a
popular-ish modification is to increase the size of the chargecooler,
this gives about 0.5-1BHP extra per 1 degree C that you reduce the
post-turbo air by according to temperature probes and dyno runs.
Increasing the size of the intercooler on a landy has the same effect
but I don't know what kind of gains you get on a 300TDi.
Of course if you cram more air into the engine then you'll need more
fuel to make good use of that.
> The converse point is that there's little gain from upping the boost
> without increasing the intercooling.
IIRC there is a point in doing it, but it does start to become
self-defeating as the extra boost gets cancelled to a degree by the
increase in air volume due to the extra heat. You can also start
getting early detonation, certainly in petrol engines, I'm not sure
how that translates to diesels.
I'm afraid most of my understanding of turbocharging and intercooling
comes from Lotus turbocharged petrol engines with water-to-air
chargecoolers, not sure how well it translates to Landrover air-to-air
For every expert, there is an equal but opposite expert