> Running the 9.7 - 1 rotors in a normally aspirated engine, I can't

get

the

 > engine to detonate at any combination of  throttle setting and

mixture.

 > Other significant conditions which might affect the results are

ignition

 > timing of 20 - 23 BTDC (both plugs, I simply disagree with those

who say

 > that a 15 degree retard on the trailing plug is better), 87 octane
unleaded
 > fuel, and a worst case air temperature of 37 F. (colder is worse

for

 > detonation, at least thats the way it works in my car).
 >
 >

Of course you are right tracy, the detonation I was talking about was in

an

engine bosted up to over 500 hp.  I may also have been mistaken and it

may

have been pre-ignition that distroyed the engine.  The guy seemed pretty

sure

it was ultimately due to his injectors not keeping up with his turbo...

As different of a case that may have been, detonation is still a concern

for

those of us who are turbocharging because it is untested.  BTW, how do

you

know you cant get it to detonate?  Do you have some sort of knock sensor
built into the EC2?  That would be great.

Cold air being worse for detonation seems a little backward to me.  Are

you

talking about your RX-7?  Corky Bell talks about the need for a good
intercooler largely to prevent detonation.  Perhaps in the car the

colder air

allows for a denser air charge.  If so, even a little boost will put us

into

the realm of possible detonation.

Dave Leonard

Tracy Crook wrote:

The cold air temp being worst case applies to normally aspirated engines
because of the factor you cited - denser air charge.  And I do agree that
turbo or supercharging changes the whole picture. Detonation is a much
bigger danger there.

The evidence of no detonation is not 100% but I'm fairly sure it is not
happening.  The only knock sensor I am using are the ones on the side of my
head but a better indication (I think) is the lack of any abrupt change in
other parameters. In other engines (piston type, the only ones I have been
able to study detonation in) the onset of detonation was always accompanied
by a sudden change in EGT and (in the case air cooled engines)  CHT.  The
other indication was a sudden hole in the piston although in this case it
was likely due to pre-ignition instead of detonation which are not the same.

On the rotary, I have done extended runs (about 1 hour) at most every
mixture setting while at full throttle while trying to determine best BSFC.
At the extream lean end of the range the engine was on the verge of quiting
which is way beyond the range of useful mixture adjustments.   Never saw any
indication of detonation but if it was, the engine didn't seem to suffer.

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org