why so juicy - technial bods

[pigeon]

How i see it is rotarys flow a lot of air for their engine capacity. The more air you flow the more fuel you need to achieve a set A/F ratio. Or am i looking at this to simply.

[Prof]

All engines are essentially air pumps, and the more power they make the more air they pump.
 
I think the point of the thread is are rotaries more gas guzzling than pistons for an equivalent amount of power produced.

[dan4]

How i see it is rotarys flow a lot of air for their engine capacity. The more air you flow the more fuel you need to achieve a set A/F ratio. Or am i looking at this to simply.

this is exactly my point, if they flow the equivalent of say a 2.6 then fuel use should be same as 2.6 piston engine

I think the point of the thread is are rotaries more gas guzzling than pistons for an equivalent amount of power produced

i dont agree with that, its not viable when considering air flow and fuelling

perhaps not as bad as has been painted

EXACTLY my point, im attempting to defend the rotaries by thinking tecnically about it

I suppose at the end of the day many more factors i.e. weight, tyres, drag etc.. come into play i was just looking at the basic physics of any engine being an air pump as you said Prof

[dan4]

Have a good read of the Wiki article - will probably help explain a few things:
 
http://en.wikipedia.org/wiki/....el_engine

that didnt work what were you trying to link to?

[Prof]

that didnt work what were you trying to link to?

Wiki article to ....el engine - stupid linky thing not working

[pigeon]

does anyone know what the CFM is of a stock 13b engine?

[Prof]

You could try :
 
L x RPM x ve x Pr
----------------
    5660
 
Assuming L=2.6 (2 fires per revolution), ve=90, Pr=1.9 (0.9 Bar boost)
 
Gives you: 628 CFM @ 8000 RPM

[Prof]

that didnt work what were you trying to link to?

Just figured out why the link broke - it appears W a n k e l contains a *rude* word - hence the link broke !
 
Tried posting the link in here again - but the rude police keeps screwing up the link.
 
For a laugh try driving your ....el engined car from S....horpe to Ligh....er - it has a field day !

[stacy]

this is exactly my point, if they flow the equivalent of say a 2.6 then fuel use should be same as 2.6 piston engine



i dont agree with that, its not viable when considering air flow and fuelling



EXACTLY my point, im attempting to defend the rotaries by thinking tecnically about it

I suppose at the end of the day many more factors i.e. weight, tyres, drag etc.. come into play i was just looking at the basic physics of any engine being an air pump as you said Prof

Hi,

As I understand it all piston engines are surprisingly inefficient. An F1 engine, for a given cycle, will produce 1/3rd sound energy, 1/3rd heat energy and 1/3rd which will provide forward motion..

I\'m hazy on sources, but think I read this in Racecar Technology a few months back too.

As mentioned earlier one of the main issues with the rotary is controlling the flame front, although with modern engine management this can be mitigated somewhat. They are hot, and they are loud, and the ratios will move slightly.

So yes, a given rotary is probably more inefficient than an "equivalent" piston engine. Later cars less so for reasons described. They also have less torque by and large, and indeed less engine braking putting more load on the brakes.

However.

The power delivery in a non-turbo model is usually relatively seamless even in highly modified motors. This makes driving in the wet much easier than a cammy piston engine, in fact it\'s just easier to get the power down.

Two of us could pick up a rotary engine and carry it about.

What little weight they have seems to sit very nicely between or even rearward of the front turrets (FB) so it\'s effectively a mid engined car with the engine at the front.

Noise can be dealt with, as can heat.

So my amateurish conclusion is that the pros outweigh the cons!

Stacy.

[od404]

I may just be repeating points that have already been made, but here is my understanding of the reason the rotary efficiency is "not so good".

I generally put it down the surface area/volume ratio of the combustion chamber.  For rotaries this is significantly larger than a piston engine due to the elongated nature of the rotary\'s chamber.  This (as already pointed out) is why we have two plugs per chamber but possibly more significantly it means that the thermal efficiency of the rotary is reduced with more heat escaping through the chamber walls.  This means that for a given working volume at a set AFR (irrespective of whether you are running stoich or not) a rotary will yield less useful work.  This also explains (in my mind at least) why at low rpm the rotary does not give out much torque.

I wrote this briefly at work, but will endeavour to put some maths behind what I\'ve wrote to help prove the theory (or disprove it :flamed).

Good debate though :cool