Post #67
quote:What is a desireable inlet charge temp? obviously as low as possible im assuming, but is there a temp thats generally regarded as being too high where you would have to be intercooled.
Just thinking about the intercooler situation for the low boost boys, just how beneficial / essential it would be.
Ta!
The most desirable inlet temp is as low as possible..
Doing some quick calculations, as per my car, the air inlet temp right at the top end (peak boost) would be
114 deg. c
This assumes:
- Running at peak boost of 1.3 BAR
- Ambient air temp of 25 deg. c.
- Assuming the compressor achieves 75% adiabatic efficiency
An intercooler is clearly vital. Assuming my intercooler is 75% efficient (its fairly large, so a reasonable assumption), it would bring my peak charge temp down to
47 deg. c.
Now, for the low boost guys, all details as above, albeit peak boost will be 0.5 BAR, the peak charge temp would be
56 deg. c.
This is a lot lower than a high boost setup, and only a small amount over the charge air temp of an intercooled high boost setup.
An intercooler is not vital hear.
However... A gain is still to be had by fitting one.
Assuming you also achieve 75% on your intercooler, peak charge temp would be reduced to
37 deg. c.
So what does this mean? For this we need to look at the resulting air density ratios.
I won't go into all the formulae, but the density ratio for the non intercooler set up (were still talking low boost here) is
0.86. If you add an intercooler, of 75% efficiency, which is quite achievable, density ratio increases to
0.96. This equates to a gain in density of
0.1, or 10%. This means 10% more air molecules will get into your engine.
You would expect to see a similar gain in power, so
10% (in reality you lose 1-2% caused by the restriction of forcing the charge through an intercooler), which could mean 25BHP. So on my conversion, with a target power of 250BHP, you may only get 225BHP without an intercooler.
So I would recommend one... even if its only a small one.
If your tight for space, Pace Products do a charge-cooler kit for the 306 HDi. Im sure this could be used, and I think it fits in with the air-con rad and everything...
________________________________________
Contact Details:
rich@lynxpowerengineering.co.uk
07732 822546
rich_w
Posted 16th Aug 2007 at 17:41
This is turning out to be a fairly cost effective upgrade for you SC guys, good work Rich 
