What happens at 200*c intake temps?

[BLSTIC]

It looks like the heaviest portion of gasoline finally boils off at around 200 degrees C (400f or so). So has anyone apart from Smokey Yunick got intake temps that high?

I think it would be especially feasible if you had a single side-draft carby, as you could run an exhaust heated grid/spacer just after the carb with an insulating spacer so the carb itself never sees heat...

What happens at that kind of intake temp? Does the complete vaporisation resist detonation? Does the burn speed raise so you need less advance?

Note that I'm not so interested in temps around the 100-125c mark, as the unvaporised fuel fraction is still fairly high and detonation would still be a concern. I guess I'm really after info on detonation vs vaporisation here...

[Daschicken]

I know smokey experimented with crazy high engine OPERATING temperatures, didn't know he experimented with high intake temps. One way to find out what happens.

Just make sure you don't have any heat sensitive parts anywhere near all that heat.

[BLSTIC]

Well he claims to have got something like 50mpg out of a Fiero, 1.8hp/ci @ 400*f intake temps, 15psi boost. Only internal mods was a camshaft change.

[oil pan 4]

I'm sure air that hot the air fuel mix is very pre-ignition prone.

[Jez77]

You would need a rather long intake tract to get the air up to that sort of temps.
All you need to do is look at the size of an intercooler you need to drop 20deg you would need something rather large and hot to slow the air down long enough to heat it up 170deg above ambient.

The risk with slowing down the air means the fuel will then drop out of suspension and likely pool somewhere creating the real risk of and explosion.

[BLSTIC]

Yes but an intercooler is trying to bring things close to ambient (the fluid around the intercooler). When the fluid around the intercooler is 500degrees c the core need not be large or efficient to transfer enough heat. Getting the heat isn't difficult.

The big claim is that Yunick says that it isn't prone to detonation. He thinks that the completely vaporised, homogenous fuel leads to a more even, faster burn

[Jez77]

Even if your core is at 500deg the air still needs time for the heat to affect it. Same principle as passing your hand through a flame, if you move it through quickly you don't get burnt.
It is also mostly the air in contact with the hot surface that will gain heat which is why intercoolers have multiple rows.
Your average intake tract is maybe 200mm long and even if it was red hot the air passes through it fast enough it would gain only a little heat.
You could take a hair dryer for example air passing past red hot elements and coming out at maybe 70deg while using 1500w of power and that's not enough air to run an engine.

[Jez77]

You also need to consider the ignition temp for petrol is between 250 and 280 deg so your heating surfaces won't want to be much hotter than maybe 220deg.

[oil pan 4]

Originally Posted by BLSTIC

Yes but an intercooler is trying to bring things close to ambient (the fluid around the intercooler). When the fluid around the intercooler is 500degrees c the core need not be large or efficient to transfer enough heat. Getting the heat isn't difficult.

The big claim is that Yunick says that it isn't prone to detonation. He thinks that the completely vaporised, homogenous fuel leads to a more even, faster burn

All this could be proven or disproven by studying propane or natural gas engines. Since there is no doubt the fuel is not only completely vaporized but also super heated.

[BLSTIC]

Super heated? I know it's entirely vaporised but I thought it was coolant temp gas at best mixed with ambient-ish air?

I think this needs an experiment. I need to figure a way to measure the burn speed of gasoline, gasoline at stupid temps, and lpg.

I have a constant velocity gas carb here I can use for optimum lpg mixing...