True. We should compare the same engines of the era. I've updated my reply two pages back.

Sorry Mr Maddox, but does that mean that you'll take the members advice and make exhaust flames blue?
As there is no evidence at all for yellow flames?
Thanks.

How did you get that?

The reply you quoted was related to a question about modeling individual cylinders in an engine to get authentic simulation of misfires etc .

There is evidence of yellow flames on startup and also if the mixture is incorrect...

Yellow flames on startup..agreed.

Yellow flames from running engine...please point me to this evidence, I must have missed it.

Thanks

We also have no evidence one way or the other for a running engine with longer exhaust stacks installed, as the Spitfire Mk. I has. All of those videos depict engines with very short exhaust stacks; Like so:
http://www.williammaloney.com/Aviati...austStacks.jpg
Instead of like so:
http://www.hyperscale.com/2007/featu...ges/Spit_6.JPG

exhaust flames
 

I've been working with planes and, at least in the case of radial engines, I still remember how amazed I was the first time I watched a ground test at night : the flames at full power are definitively white with a blueish end ( with the carburator and ignition tuned properly ) and they extended more than half the fuselage!!! ( the plane was a biplane used for cropdusting, with radial engine and one exhaust stub by the right side ) to give you and idea try to find pictures of Hurricanes used as night fighters... they had to add an anti-glare panel just ahead of the cockpit, and the streaking extends beyond the cockpit ...

Again, very interesting flame patterns / colours on rpms on this meteor ...

http://www.youtube.com/watch?v=D7WS5...eature=related


Also interesting LACK of flame on this merlin, packard I presume, fuel types on both vids...who knows.
http://www.youtube.com/watch?v=-mQRJA5W8CI

Wow, this thread is hilarious! The whole thing has been explained several times and still people argue about nothing. It makes me glad that I've decided to spend much less time here. See you on Friday, Oleg.

this is no CSI, no evidences available, only the laws of physics ;)

Once again, we need to make a distinction between startup backfire and exhaust flames:

1) on a cold engine, backfire happens for overpriming/bad magnetoes not delivering regular sparks at low revs; on a hot engine, it happens for the same conditions of a cold engine plus the hot exhausts/outlet valves/combustion chamber/carbon residues, who can ignite the non burnt mixture. In both cases the result will be a "cold flame"(as in relatively low temp flame) which will roar out of the exhaust (and warm up the combustion chamber a bit!) in a spectacular fashion. Backfire is more dangerous on radial engines because the flames can linger in the exhaust ring outlet and pre-ignite the mixture in the combustion chambers (blowing up cylinders/valves/spark plugs).

2) exhaust flames are the result of a correct combustion in the chamber, and because of the temperatures and pressures involved, they come out as hot flames normally (blue flames).

If you have the movie Tora Tora Tora have a look at the carrier takeoff sequence to see a good examples of blue flames in action.