As the owner / driver of a sponsored drag car , running a twin turbo small block chev  on methanol fuel , i want to share some data , and get some ideas please.

Initialy we spent 3-4 days on a engine dyno , to develop a fuel curve, and this is where some of the data has come from.

The sbc , 358 cubes , with a tunnel ram style intake manifold, and mechanical fuel injection ( constant flow) that has 2 nozzels per runner , enderle style nozzels, quiet a large plenum ontop of the tunnel ram, with twin 3 inch throttle bodies at the front.
twin 66mm turbonetics turbochargers feeding this engine.

Now,
from the data logging on the dyno, we found the temperature at the compressure housings outlet was around 148 deg C.
The temperature after the 2 fuel nozzels , at the intersection where the intake manifold bolts onto the cylinder head, was around 50 deg C.
The methanol fuel obvously does a really good job of cooling the intake air charge.

The boost pressure  at the compressor outlet, and the intake plenum was the same , 29 psi recorded.
The boost pressure at the intersection of the tunnel ram and cylinder head was approx 9 psi lower......

Does the "ideal gas laws" , apply to dynamic air flow ??
If the intake air charge , is cooled does  it directly affects the intake air charge pressure ??

I realize that the pulses in the intake runner change, but the equipment used , only records the max reading.
The intake runner of the manifold, is same size as the runner in the cylinder head.

Ideas  for the reason for drop in boost pressure ???

The ideal gas laws are going to still be valid at those pressures. With the quoted temperatures you should expect a little over 20% pressure drop (420K to 330K - ignoring that you've added moles of gas, which will add some error here). I'm not sure if you really mean boost pressure (i.e. 44 psi absolute, 29 psi boost) or absolute pressure of 29 psi. Assuming we're talking about a drop from 44 to 35 psi, that would match the expected temperature effect closely.

If we're really talking about 29 psi to 20 psi, then that's a little high (30%) and there is probably a measurement issue. However, I think when you said boost you meant boost so everything looks good.

Just to be clear, I have crewed with Ash and suggested he post here as I considered his operation as a professional operation and Ash has a good understanding of the science behind this, which I believe gives him the same rights of passage as both myself and Rod when we started here.

I am kind of hoping that as well as Jsteve, Rod, Greg, Isaac and Matty might contribute some thoughts.

In discussions one thought is where do you inject the methanol to optimise VE for the same energy input to the turbo but still get good ignition and burn rate to give optimum thermal efficiency.

The thought process got to how much of the fuel do you want o evaporate in the manifold, how much in the chamber while the valve is still open and how much on the compression stroke.

If you have very little fuel evaporate before the valve(gate valve), how much extra fuel do you add to compensate for some fuel not evaporating and burning during the compression stroke and power stroke.

There is a point where if extra fuel is added to compensate for insufficient evaporation, the mixture is so wet that the ignition will not light it. This is partly set by the plug gap, volts, amps and duration of the spark and this is limited by the ignition system.


Are you measuring maximum or an averaged pressure. A restriction in the tube between the gauge and the point being measured would slow down response rate and average out the pressure or at least smooth out the pulses.

I expect he pulses in the runner may go slightly over plenum pressure and significantly below it during one full engine cycle.

The thing that I don't know is does the volume of fuel vapour fully offset the cooling effect due to the latent heat of vaporisation.

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