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All,
With the 40% bypass I believe I will only have a temp
rise of 30-40 degrees in take off conditions. So 140 degrees with 100 OAT.
At 8K altitude we typically see 68-70 degrees in the summer. So making 4
pounds of boost should net temps in the 150 - 160 degree range. This is based on
Eaton's M62 4th gen charts. This may be too close for comfort. I will be doing
extensive ground testing and measuring charge temps. I have to admit my initial
plan was to locate the injectors about 12-14" away from the rotors to take
advantage of fuel cooling. Marks S 's. at that location would frost
the tubes until he moved them closer. I have since switch to the stock lower
renesis manifold.
I am not committed to the current arrangement but
I do intent to test it on the ground. I already have a plan for an intercooler
and plumbing.
Bobby
Hi Bobby,
I won't add to the caution about detonation due to high
temps of intake charge, However, I will mention that Tracy Crook sells
apex seals that are highly resistant to detonation. In fact, I don't
believe even the drag racers with high boost levels have succeeded in breaking
one. Under detonation they at worst deform - but don't break.
Not to suggest that you can use those seals and have no
worry, there are other areas than apex seals that detonation can damage.
There is a school of thought that says using high
compression (pistons) with turbo/super charging gives you the best of both
worlds. You get the strong initial pick up due to the high compression
pistons without the (sometimes momentary delay) waiting for boost to come
up. The combustion chamber treats boost as basically increasing the
compression ratio. It entire thing is combustion chamber pressure
(however, it gets there). High compression/low boost or low boost/high
compression - it doesn't make a difference to the engine. The total
pressure is all the engine knows.
However, if you are using high compression rotor/pistons
then you do not have as much margin as low compression rotors would give
you.
Having a supercharger rather than a turbocharger also
helps as there is no migration of heat from the very hot turbine housing over to
the compressor housing. But, you still have the temp increase due to
compression.
I would certainly be cautious on the boost.
Those who are using turbochargers and have had long term success appear to
generally use less than 5" Hg of boost.
Good luck and we are all waiting to see your
success
Ed
----- Original Message -----
Sent: Monday, November 05, 2007 2:43
AM
Subject: [FlyRotary] Boost without
intercooler [was MAP port location]
Hi Bobby;
I have seen several turbo "detonation danger"
charts over the years. Heck if I can find any of them now.
Some
searching should turn one up.
Detonation also depends on engine load - ask
Lynn about NA detonation at idle speeds.
Here is a link to a
calculator:
http://www.turbofast.com.au/javacalc.html
How
to avoid detonation:
http://www.misterfixit.com/deton.htm
According
to most information, 3mm apex seals will not save you from detonation in a
wankel,
at best something else in the chain will break.
If you insist on
running without an intercooler you better have knock sensors with a fuel cut
defender or the like.
You might also look into methanol, ethanol, water
injection to cool the intake charge.
The wankel has a lot of positives,
survival with detonation is not one of them.
Good Luck
Cary
Bobby,
I know your planning only normalizing with the
Turbo, but my concern with the 10:1 high compression rotors is that you
might get into detonation - especially without an intercooler.
Then again I'm no expert, that why I would like
to know the safe boost level as well.
I recommended the 3mm apex seals because
of my concerns of detonation, not so much the loss of
hp.
George ( down under)
George,
Mazfix and Mazsport are both boosting to 280hp at the
wheels. http://mazfix.com.au/perfproducts/rx8_upgrades.html.
Pettit Racing is seeing 270+ with 5-8#'s http://www.pettitracing.com/rx8/index.htm My goal
has always been to match the IO540 at 8000ft and have a much lighter
plane with new engine. No doubt I will be giving up some HP without the
intercooler. One percent for every 10 degrees I think. If my
cooling ducts and exit area work as planned I may add an intercooler. The
goal now is to get the engine started and flying by summer.
Bobby
RV10
Bobby,
I would be interested to see what boost is safe
also. You might consider an intercooler!
I assume you are using it on a RX8 engine( i.e.
10:1 ), if so, you could always consider going to 3mm apex seals, if you
feel it would be safer.
George (down under)
Not much to tell Rob. It's an Eaton M62 4th gen. http://www.capa.com.au/eaton_mp62_4th.htm My notes
show the weight at 25 lbs but I am not sure if that included mounting
brackets. If everything goes as planned I should be able to fire it up
in January. The plan is to use it for normalization or 1-2 psi of boost if
the discharge temps are not to high. It has a 1" internal bypass that
provides a intake air path around the screws so it is yet to be seen what
effect this will have on temps.
Does anyone have any real data as to maximum safe
intake temps with 10:1 rotors and 2mm seals?
Bobby
Bobby
Tell us a little about your supercharger. What
brand? How much? How heavy? Have you run it yet?
Thanks.
Robert
20B in a BD4
Robert Bollinger FM1099 MUM Fairfield, IA 52557 rob@mum.edu Home
(641)472-7000ex2068 Cell (641)919-3213 ----- Original Message -----
Sent: Monday, October 29, 2007 5:09 PM
Subject: [FlyRotary] Re: MAP port location \
Looks like the
consensus is to place the MAP ports away from the runners. I will try the
discharge duct of the supercharger for both MAP and the Grand Rapids EIS
temperature probe. Looks like the EC2 temperature probe should not be place
after the blower since it leans fuel at higher air temps. It will go after
the air filter and before the throttle body.
Thanks,
Bobby
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