I've repeated your rear-window tuff testing with my 2003 (NHW11) Prius:
I'm seeing similar flow separation at the rear window. I'm looking forward to trying some 'home made' vortex generators.
This is a great website for the auto gearheads (me). I really enjoy reading your articles. I sense that you like the the Hondas, Toyotas etc. more than the VWs, Audis. I hope you will include more VWs, Audis, and other European cars in the very near future.
Btw VW was the 1st in the world to introduce 3L car, the Lupo. Not the Insight as you've claimed. Besides, the Lupo engine runs constantly to get that 3L/100 km. While the Insight's engine has to be helped with an electric motor to achieve the same fuel consumption.
The article on chasing down overheating issues (see Chasing Overheating) is a very interesting and insightful piece offering some clever ways to combat temperature rise when idling and moving slowly in city traffic. It was especially intriguing to me, as my car, a '91 230E Mercedes- Benz, has the same tendency in traffic. Although thermostat opens fully at 87C, the fan cuts in at 100C, and it is usually a matter of 10 minutes or less in a standstill to reach the 100 mark and stay there.
I think however ingenius the approaches described to combat rise in temperature are, they do not address the reason for this temperature rise. Making a 380 "stroker" out of the 308 V8, effectively raises static compression from 9.7:1 for the original to somewhere around 12:1, unless the combustion chamber was also modified to keep this 9.7:1 ratio. When compresison is raised, the igntion process should be more thermally efficient, according to commonsense, however ignition advance should be revised, and higher octane requirements should be considered. Or am I wrong? In effect the temperature should have gone down with revised timing and higher octane fuel, but instead it went up. As I am using an alternative LPG fuel system,I have noticed that on my car, setting the mixture differently also plays a role on coolant temperature - with leaner LPG mixtures giving lower coolant temperatures, and richer giving a faster temp rise when idling.
It would be interesting for me and for other readers as well I believe if you could elaborate on this "hot" topic. :)
Graham Pring replies: The compression ratio of the two motors was almost the same as low compression pistons were used in the stroker motor. I run premium unleaded petrol and 98 octane if available. The mixtures run stoichiometric at idle. The ignition timing was set to give minimum exhaust gas emissions and left there. An Idle Air Control motor keeps a constant idle speed.
chasing overheating - chasing overheating
hi mate, great article. only things i like to add is you missed some issues with the thermo fan.
a) it didnt have its own shroud (so the article shows). so a percentage of air in the engine bay would be circuilated by it, instead of all its CFM force being pulled through the radiator. So efficiency will be down there as well.
b) use a radiator shroud to "box" the entire radiator core to the thermo. this again improves efficency of the thermo as air is being pulled through 100% of the radiator core as apposed to the round dot the thermo fan foot print would have against the radiator core.
Graham Pring replies: All versions of the fans have been sealed against the radiator and had shrouds on. Photos taken may not have the shrouds in place to show the fan more clearly.
I have just read the article on the DS Citroen The Amazing Citroen DS. I wish to point out that the 1968 DS21 of Lucien Bianchi and Jean Claude Ogier was not forced out of the London -Sydney Marathon by mechanical problems as was stated in this article. It was in fact deliberately rammed by a Morris Mini Minor that had no business being on the closed road. Bianchi and Ogier in fact were so far ahead of the field that no one could have caught them, and at Nowra where the "accident" occured had a little over 100 Kilometres left to the finish line.