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Message
I am totally new to all of this, but have to learn. I don't want much
boost (maybe 35" or so MAP) for takeoff, but want to turbo normalize to around
15k'. I know detonation is a problem with high boost and I will have
limited intercooler resources. With that in mind, how does this sound
....
Sounds like
we're after the same thing. BTW, I have no intercooler at all, which is
another reason that I'm afraid to run too much boost for too long at Summer sea
level temps in Florida. I can
definitely tell the difference in mixture between the A and B controllers on the
EC-2. The A controller uses the temp sensor, and the B controller does
not. The temp must be elevated quite a bit, but until I get the EM-2 to
read it, I won't know how much.
I would have a manual internal waste gate. The waste gate would be
normally open (dumping all exhaust past the turbo). On takeoff, I would
run WOT (say 29"), no boost. I could close the waste gate a little and get
33" for example for a hot day or short field. As I climb out at WOT, I
gradually close the waste gate to maintain 30" MAP. Since I'm running
essentially NA at low altitude (where the atmosphere is warmer) I don't need
much in the way of an intercooler. As I climb and progressively close the
waste gate to maintain 30", I need more intercooling, but this need is reduced
by the cooler atmospheric temps. At altitude, say 15k' - 17k', 30" has me
going like a bat out of hell, and the cooler air going into the system requires
less intercooling.
The only
problem I see with this plan is your assumption that opening the wastegate will
eliminate all the boost. In reality, stock wastegates aren't able to do
this for us. If you look at how an internal wastegate works, you'll
see that it isn't a valve that diverts exhaust from the turbine to the open
exhaust pipe. It's really just a door that opens to give the exhaust an
easier path to the tailpipe. This doesn't stop some of the exhaust from
turning the turbine and creating some boost.
In a car, where
you have catalytic converters, mufflers, and restrictive air filters, there's
enough restriction in the system to limit the amount of air that can move
through the engine. In the case of a stock engine with these restrictions,
the stock wastegate is as effective as it needs to be. When you
remove these restrictions, even in the car, boost can't be completely controlled
by the wastegate anymore. Some wastegates are more effective than
others. In RX-7's for example, the series 5, 89-91 turbo wastegate is
quite a bit bigger than the one on the series 4, 87-88
turbo. My series 5 wastegate has been wide open, and
the turbo still wants to make more than 3 psi of boost. Until I set
the pop-off valve for a higher number, and go to a safe altitude to test
it, I won't know how much it will really make. Ideally, I'd like to be
able to open up the flow of the wastegate until I could only produce 3 psi of
boost with the wastegate open. At that point, I would only have to
insure than the wastegate is open at low altitudes, then I couldn't overboost
the engine. I can't wait to get my temps in order, so I can see what the
turbo will really do.
Cheers,
Rusty
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