In a message dated 6/29/2006 6:32:46 P.M. Eastern Daylight Time,
lendich@optusnet.com.au writes:
It has been suggested
to me that 140 degree is the upper limit of inlet air temperature
before detonation occurs.I guess this is a
guide to a turbo inter cooler
application.
Again as you say,
compression varies this, I didn't think of advance and the accompanying
variable volumetric efficiency between idle and high rpm affecting
compression.
Why don't the big
boys run air conditioning units to cool the intake - does it suck-up too much
HP?
George
By the "Big boys you mean airplane engine? They all (all of the turbo
engines) do run inter coolers. In the hand book for those airplanes there would
be some of the data you seek.
The 93-95 Mazda had a large inter cooler, and the first big hop up item
added is a bigger inter cooler.
The engines tolerance to Detonation (charge temperature) is a
function of its construction, chamber shape and detailing. The rotary with
a large cool surfaces in the chamber is not prone to detonation.
Not until the coolant temps and oil temps become too high and the mixture
is just right, (just rich of peak EGT and the timing is just a bit too advanced.
Anyone who gives you a hard number for any of these values..............well,
don't buy anything off of him.
If one value is just a hair too low then another value will have to be way
over the line to get detonation. It cannot be one thing alone. Sort of a team
effort if you will. A combination of values that occurred on that occasion.
Suppose there was an instance of detonation that was detected by a Lambda
sensor. If we are recovering a number of values from the engine and can download
them to a screen, we can see the exact combination that produced that
event.
It could happen again tomorrow with a different set of values. This is done
in racing all of the time. Then lay these values from yesterday over today's and
see what changed.
If the temps are even marginally under control, it won't happen. So, one
day, 140 might be OK, and the next day something else changes and 140 is too
much.
The street racers add water to the intake at high boost numbers. They tune
very rich at high boost. The timing may be close or into minus numbers at high
boost. They spray water on the inter coolers, oil coolers and water
radiators at high boost.
Do we see a pattern forming here? They take away waste heat any way they
can with special attention to induction (charge temperature) tract temps.
Lynn E. Hanover
Lynn,