Idling for 5 mins or so to run down the turbo speed was the go.
That’s a persistent furphy. The end of the landing roll is the point at which an engine (and its turbo, if fitted) will usually be coolest. The taxi afterwards and any stationary idling just warms things up.
On a ferry of a Bch. A36 WA to Qld I went in to Coober Pedy for fuel. It was 40 degrees OAT. I faced the '36 into what wind there was and did the refuel and had my lunch. On shut down I opened both cowl halves so that the hot air around the engine could dissipate.
It worked. Half an hour later I buttoned up the cowl halves and the donk started at first try. No boiled fuel in the fuel injection lines.
A good one for young pups to remember and use.
That worked because the heat-soaked engine driven fuel pump (EDP) was cooled, not because the injector lines were cooled.
The primary cause of hot start problems on normally aspirated CMI 520s/550s is the vaporisation of fuel in the heat-soaked EDP (bolted to the back of the crankcase). That’s why on some aircraft with those engines the most effective hot start procedure involves running the electric fuel pump for a minute with the mixture set to ICO. A bunch of lovely cool fuel is pushed through the EDP then turned around by the FCU back to a fuel tank.
I say on ‘some’ aircraft because the electric fuel pump is an airframe component, not an engine component and not all electric fuel pump systems are the same. For example, different model Bonanzas have different fuel pump systems. Mine had a switch that had only two positions: ON and OFF. The pressure out of that pump was so high that it ‘overcame’ the FCU in ICO. Running that pump for 60 seconds was a ‘bad’ idea. Other models have three positions: OFF, LO and HI. The ‘LO’ position is ideal for use to cool the EDP before a hot start. And then there can be differing EDPs between the ‘same’ kind of engine…
All of which is to highlight, once again, the fundamental importance of knowing the specific systems fitted to the specific aircraft you are flying.
(I always opened the cowls on my Bonanza after flight, for the earlier stated reason: To reduce the baking of the in-cowl components. And to have a nosy around - I stopped being surprised at the number of tools, cable tie tag ends, washers, nuts and bolts I’d find. It freaks me out that I can’t do that kind of inspection easily after each flight on the aircraft I’m currently flying.)
For those who think manufacturer’s manuals don’t contain any bollocks, think again.
Anyone who has a real interest in the safe and efficient operation of aero piston engines would be well-advised to do the APS course. (Disclaimer: I have no direct or indirect pecuniary interest in APS courses.)