Intake compensation solenoid valve and mid throttle...

Hey a theoretical one again.

Our Motronic 2.5/7 acrs had 2 ecu's as there weren't that many ECU's that could map beyond 6 cylinders. The 5.2 system could handle an 8 cyl, and the 355 moved to a single ECU system where air and fueling was calculated for the whole engine (not bank per bank).

So the 2.5/7's needed to separate the physics of the engines and run them like two virtual 4 cylinder units where the banks are timed almost in parallel. I think the throttle valve between the banks in the 348 acts to even out the air supply pressure within the banks when the engine is at its peak torque range and pulling hard with wide open throttles (open loop ignoring MAF/O2).

A while back I "shorted" the vacuum hoses between banks and found a vibration at around 2000 rpm's disappeared - at 2000 RPM's the idle bypass screw still has enough effect on the very small opening of the throttles. That made me invest in vacuum gauges, and then after balancing the intakes, throttle opening timing etc., I remained vibration free when I disconnected the vacuum short.

Doing some research, I concluded the cross connection is not a hemholtz resonator as this needs to project into the space in order to abate the sound pressure waves, I am certain it is a simple mechanism to deliver torque "increase" by AVOIDING the reduction in power from having one bank produce less power asynchrononously - so to say putting both banks "on the same page" as they breathe the same air mass, burn the same amount of fuel being on WOT tables. High torque = high workload, which is when the engine is most sensitive to bank imbalances (damage and performance). Above that inertia takes over, below that - who cares and emission control is king.

I connected the vacuum hose from the throttle actuator directly to one of the vacuum nipples on the manifolds, so the thing is always open. What's the result? the engine is markedly smoother (all harmonious vibrations have gone throughout the RPM range), the intake noise is a bit louder (growl) and the engine is markedly more responsive.

Clearly, there must be some potential for negative effect otherwise Ferrari would have built the things with a common inlet manifold and a single throttle valve. Would this be when the parameters between ECU's differ so much a CEL would have come on? or was it the theory that if the system was set up as two separate systems, then it should remain so except for a very narrow range of operation? I guess in the 355, being able to set individual throttles completely removed the need for bank balancing...

I have a Motronic 2.5, which has no CELs. In fact, the only time you know something is wrong is when fire or parts drop off the back end, I'm going to have fun with this... I'll leave it open for a few months and see if there is any adverse effect.

Let me know your thoughts!!!

Marco

P.S. I bought a whole inlet manifold unit, which I may merge into one unit with a wider throttle opening. Using Scottchky diodes, it is possible to wire up a single MAF unit for both ECU's (I did it inelegantly on one of my other threads when one of my MAFs fried and I had to live for a while on a single one) and I have already managed to transplant the sensor unit from the 2.5/7 MAF into a wider tube - providing the hot wire is within the main airflow core it reads just as well.

 

Replace the fibrous hoses going from the side intakes to the filter housing (I used aluminium ducting for an AC and painted it black using black vinyl paint so it doesn't chip), and connect your output from the ICSV to a vacuum nipple. Take it for a spin with the windows down and just hear that wonderful music - Tubi for the inlets.

The old fiber hosing used to shed particles (looks like glass fiber when shaken in direct light), and partially collapsed.

Marco

 

I would argue that Langarian methodology is more appropriate in this context than Hamiltonian given that the limited universe dictated by the inlet manifold's volume is quite finite and can easily be expressed as a coordinate space as opposed to a theoretical phase space (it is solid and in all operating parameters quite constant - so no need for the more comprehensive description of the universe as a phase space). The interactions within the inlet manifold are non chemical, thus the context of Pauli's description of sub-atomic particle waveform asymmetry in particular descriptions of fermions may over complicate the model. We can however consider these as a pretext for the description of the chemical phase (exothermic oxidation with electric discharge as a catalyst) where the exchange of electrons is the foundation of the reaction, both in the break-up of the various hydrocarbon chains/rings and the oxidation of the simpler intermediaries.

I suspect that within normal operating ranges, the state of the higher energy orbitals of the active constituents (only the Oxygen and other combustible compounds in intake air) in the flow is the same than that in still air..

You have helped a lot. In making me think of these issues, I suspect that using a tiny magnatron in line with the spark plug, would use the microwave energy to make the electrons in the highest energy orbitals jump to even higher ones, stimulating spontaneous break up of complex hydrocarbons in the fuel into simpler units that are closer to self combustion in the presence of oxygen. It being in-line with the plug, should prevent this from causing any mechanical problems due to ignition timing changes.

I may be wrong, as I graduated away from theory over 20 yeas ago...

 

I have removed the throttle in between the two plenums and inserted a diaphragm with a tiny switch that is activated if it is moved from side-to-side. I wired it into a 9V circuit with a 3V LED (fast activation at the smallest hint of current) as I don't have an oscilloscope. The switch requires a deflection of more than 10deg. at the tip, so "should" rule out harmonious oscillations.

It is quite interesting to see that it pulses at a frequency linear to engine RPM, so air does move between the banks. I noticed some blinks are brighter than others (at a frequency too) so more air flows between SOME cylinders. If I had a directional switch (3 pin) and an oscilloscope tuned to a given cylinder then I could see which one(s) breathe more.

I would guess the frequency of the brighter flashes is 1/2 of the overall, suggesting that a symmetrical set of cylinders either breathe better, or cause a bigger shock wave (caused by air accelerated during the intake suddenly hits the closing valve at the end of the intake stroke and "bounces" back out of the long inlet pipe - Incidentally, the length of the inlet pipes is tuned to dissipate most of the energy in this shock wave at 6500 RPM and above). Irrespectively, there is air movement across the orifice so who knows, I may have had fun with nothing. found a way to enjoy intake noise, or the whole thing breathes better - regardless, I got to spend another weekend tinketing around and learned about the intake this time - did the electronics, the gearbox, the exhaust etc.

M