The Broken Fiat Club

While preparing Project Pasbarth's shell for its rollcage install I've come to the resolution that I'd like to re-wire the car with a race-spec harness right off the bat. (I'd originally considered running the car's early testing phase with OEM electricals and tune and evolving toward a purpose-built wiring harness and ECU, but I've since started to think that skipping right to the full-race harness might cut the eventual head-scratching in half.)

I've wired a half-dozen Honda-based racecars from the battery on up with standalone ECUs, so the wiring part itself is not the challenge as far as I'm concerned. MultiAir, on the other hand, brings its own ECU-related questions:

1. While a few standalone ECUs claim to support VVT solenoid actuation, are any of them specifically capable of controlling four high-speed MultiAir solenoids?

2. Supposing I found a MultiAir capable ECU, would I want to put my tuner through the process of mapping multiple MultiAir modes, particularly while I've got
people shopping around Europe for a conventional 16V twincam head? (https://brokenfiat.club/forum/viewtopic ... t=10#p2525)

3. To make the tuner's job easier - and also because racecar - what's the most robust and dummyproof method for a 'VTEC-killer'-style mod that leaves the intake valves on their full-actuation profile all the time, lumpy sick-puppy idle be damned?

I see two ways of achieving this 'full profile' mode: first is to have the solenoid supplied with a constant 10A with ignition (per Fig. 10 here: https://www.schaeffler.com/remotemedien ... _18_en.pdf), which for me would introduce the constant and distracting suspicion of impending solenoid failure at any given moment; or secondly, replacing the solenoids with machined slugs that make the 'full cam profile' a static, passive given. This "MonoAir slugs" mod is currently my strong preference.

From what I've read, the solenoids are difficult to remove from the brick, and I haven't seen anyone find drawings (much less supplier spec) for the solenoids themselves. Between the road car, race car, and spare motor I've got three such bricks in the fold at the moment, but I'd rather source a pre-failed brick than to mess one up searching for answers. Has anyone got any insight on how the solenoids are fitted? Interference fit, maybe?

Beyond that, I'm wondering about recommendations for standalone ECUs and/or base maps for this purpose. (My ECU experience is so far limited to a bunch of easy Honda plug+play options, some sealed race-series ECUs, and one E+C reflash.) Should I poll EC/Tork/Speedmotive etc. for standalone recommendations in hopes that any of them might be able to supply a base map that's something like E+C's nonturbo tune? Or should I look to Europe for a 169 A3.000 (Panda 101HP etc.) twincam tune?

FWIW, for those who haven't already seen it, I found the OEM cam profile on slide 70 here: https://docplayer.net/41583865-Fiat-mul ... rvice.html

Thoughts?

This is exciting, but largely uncharted territory that you are in.

I hope you keep us updated as you find information. Part of my fear with this platform (or any modern platform) is that the electronics are going to become unserviceable at some point and then a lot of us are then going to be looking at options like this.

The problem with controlling the multi air with aftermarket ECUs, is the requirement to operate 4 VVT sensors, that option is usually reserved for top end ECUs I.e haltec elite 2000.

It would be awesome to do this, though, would mean you’re not at the mercy of one tuner or another.

If your intention is to lockout multiair anyways, then why not convert to a non multiair head (not sure if it’s still t-jet for NA) with no VVT to deal with. Should be much easier to tune with cheaper standalone ECUs

Don't get me wrong, I'll eventually end up running a conventional twincam head. In the meantime I'm looking at a passive solution to enable the standard MultiAir head to run in single-cam 16V configuration, using the same standalone ECU that I'd keep using once the twincam head and cams arrive. I just wanna do some track testing before I have all the components to build the motor in its ultimate spec.

Put simply, I figure that the only thing keeping anyone from running one of these motors on a standalone ECU is the cost of having some passive 'dummy' MA solenoids machined up.

Followup: it occurred to me last night that disabling the 'bypass' capability of the solenoids might itself cause some problems. In the best-case scenario, it would turn the MA brick into a 'cul de sac' in the oiling circuit, possibly increasing odds of localized viscosity breakdown, varnish, whatever. In the worst-case scenario, it could cause havoc with excessive oil pressures and all the nightmare scenarios that can follow: leaks, oilpump failure, and/or who knows what else.

This being the case, machined 'dummy' solenoids won't do. One would basically have to retain or match the standard algorithm that enables the solenoids to bleed off some oil back toward the oilpan at whatever point it's designed to during full-power driving, whether that's off-throttle, or at a certain point during each rotation of the crankshaft. This calls for an ECU with the sophisticated VVT control that Romanoaf mentioned above, as well as a patient and well-paid tuner.

For my part, I think this means I'll be skipping right to the conventional head swap.

So I'm seeing 'variable cam control' in the feature lists of the standalone ECUs I've been checking out. Haltech Elite 1500, for example, cites...

Variable cam control - Independently control up to 4 camshafts - Requires a minimum of 1 user defined input & output per variable cam

If we treat each MultiAir solenoid as a cam control solenoid, will these cam control channels pulse quickly enough to pulse each solenoid once per revolution (given max lift/duration with periodic pressure bleedoff to maintain oil circulation)? We're talking 133.33Hz at 8000RPM.

Or... I could just pull that T-Jet cam carrier off the shelf.

The t-jet is definitely easier; and has been done before. Robert Zecca's imported car has some form of independent ECU.

Ah, I assumed "Mefistofele" was merely running a Seletron Chipbox. I plan to give Zecca a call in the next couple of weeks and see what he suggests. Will report back, of course.

It’s sometimes hard to follow, but my understanding is that car is custom. His other track Abarths run the Seletron.

So I have a theory.

On the latest Mighty Car Mods, they did a turbo Yaris which had a VVTi motor. They left the stock PCM in place to handle the normal engine operation including the VVTi system.

They installed the Haltech in a "piggyback" mode where it would override the fueling and timing from the stock PCM.

I was thinking last night about a flex fuel setup for the Multiair and that popped into my head.

Could the Haltech, in Piggyback mode, basically work like the old Unichip did? Except much more advanced? Allowing the stock PCM do so the grunt work, while the Haltech would monitor ethanol content, boost, etc and adjust timing and fuel as necessary to maximize performance?

Not as elegant as a full standalone, but would retain full PCM integration with the BCM, so you still have a fully functioning car in every other way, while having the ability to alter various parameters on the fly. Main challenge would be to keep the factory torque limiters happy while the Haltech does its work. That would if course require a tuner who knows what he's doing...