gemellocattivo.com

Starting a new thread from the discussion: http://gemellocattivo.com/forum/viewtopic.php?f=2&t=8&start=720#p2164

From that thread:




Thoughts:
-Best method to connect engine to ECU (vast majority of wires on engine go directly to ECU)
-Fusing, fuse boxes, and relays
-Wire harness mounting and protection/braiding/shielding
-Stub harnesses and disconnectable harness segments
-Where to get connectors and wire

Mark also suggested https://www.prowireusa.com/default.aspx - They have Deutsch DTM/DT/DTP connectors and a variety of Autosport and 38999's.

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"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

One of the more insidious issues with Ferraris is their crap wiring. We're talking 60's and 70's wiring techniques and weather sealing that were carried over into 21st century cars.

Their "fuseboxes" have motherboards with multilayer printed circuit traces for the main runs, and they're undersized for the current load, and get so hot that the boards delaminate and the traces separate. Ferrari even power the twin electrofans and fuel pumps from these motherboards, and the fans together typically pull around 40-50 amps, and 5x to 6x that when starting. Even Detroit learned you can't run all the car power through one main fuseboard, and especially not the electrofans and fuel pumps, however it wasn't until the 599 model that Ferrari began distributing the loads and the wiring around the car.

Besides the above issues with power wiring, the low current and signaling harnesses have connectors that aren't well sealed, and use female terminals that lose their spring tension with age & use, causing poor connections. This, along with corrosion issues results in many of the spooky Ferrari gremlins that are so endearing to us.........

Everyone wonders why, with the same Bosch components as the German cars, the Ferraris have so many electrical gremlins and the German cars don't? For me, it's clear; it's the harnesses, and the fuseboxes/motherboards!!!!

We have people in the aftermarket making gold connector kits, rebuilding fuseboards, building new injector harnesses, etc. to work around the poorly engineered, and even more poorly manufactured, Ferrari content.

OK, rant over, but I'm considering building new engine harnesses for my 550 c/w CPC's or circular milspec connectors for the bulkhead pass-throughs, and doing the very best I can to eliminate poor connections, poor sealing, and those poorly engineered and built fuseboards. Or at least getting the high current loads off them.

For our (FSAE) very small racing cars, a single fuse box is way more than we need. If we had maybe 3 fused circuits built into the ECU it would be perfect. For racing cars with more cylinders, in general most of the luxuries which require electrical power are nonexistant so a smaller and simpler fuse box is acceptable. For production cars, there are quite a lot of loads and such and it's a lot more to manage.

In general, fuse boxes double as relay boxes and probably include radiator fan relays. Better PCB design can do wonders for high-current distribution, there's no reason it can't distribute a few hundred amps from a 6 awg+ cable reliably. I do think a PCB is the right way to go for all but the absolute largest connections (like alternator and starter), and you can include smarts in it if you want (like fuse monitoring and current measurement to better detect issues). Some OEMs have combined the underhood fuse box with body control functions (distributing 'ignition on' and 'ignition aux', body lights and signals, and wakeup of other modules). Others have a totally dumb fuse box and separate BCM.

For circular connectors with a lot of pins, 38999 really is the way to go. Most of the ones you'll find are series 3, which have a threaded locking mechanism (which is more vibration resistant than the series 2 bayonet locking mechanism). This might help:http://www.ttieurope.com/docs/CP/6223/Mil-DTL-38999_Series_III_Part_Number_Build.pdf - Look at the D38999 part numbers on the right. A shell style '24' (jam nut receptacle) is good to use for bulkheads and is more common than the dedicated bulkhead receptacles. The contact arrangements can be found here http://www.amphenol-aerospace.com/pdf/catalogs/D38999_III.pdf starting on page 6. These are very much overbuilt for cars, but they are also extremely good connectors.


Theoretically the AS type connectors should be extremely similar to these, I don't know too much about those. The prices are about the same though.

Overall I'd recommend using 38999's only at panels/bulkheads and using Deutsch DT, DTP, DTM everywhere else. DT and related are commonly used for heavy-duty trucks, including military ground vehicles, are sealed well, and much cheaper than 38999. A round Deutsch is standardized as the diagnostic connector for J1939 (heavy-duty truck CAN), but the round ones are larger.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

Can't say that I agree with you on the PC boards. I'm a fan of Japanese automotive wiring, particularly Toyota, and they use solid copper bussing in their main fuse/relay panels. They'll run either 2 or 3 main +12 busses for +12 Battery, +12 Ignition, and sometimes +12 Master Relay. In Ferrari's case, the PC fuse boards are well known to be a classic point of failure for the last 20 to 30 years of their cars.

Regarding signal wiring, most of Ferrari's sensors are Bosch and use AMP junior timer type 2/3/4 way connectors. Do Deutsch make connectors to fit Bosch sensors?

No, you would have to use a Bosch connector on that. One thing you can do if the sealing isn't good enough is use the stock connector, pot it with epoxy, and heat shrink around it, then put a Deutsch connector inline a few inches down. We have done this with soldered leads if we couldn't find the correct mating connector.

For powertrain, usually there's a main engine relay which is switched by the ECU from direct battery, so the ECU can hold power on after ignition is switched off. 'Ignition' relay and 'Aux' relay doesn't actually supply a lot of current, it mostly serves to wake up modules. For automatic transmissions, there's usually a trans relay also. For body lighting, the BCM (which could be integrated with the fuse box) contains a high-side MOSFET for each light and is fed by a fuse for all lighting loads (except headlights and high beams which are usually relay-driven since they draw a lot of current). Most interior loads are fed by direct battery and expected to shutoff based on either the ignition sense or CAN command, this allows them to gracefully shut down and lets the car keep the interior comfortable for 30s or so after the engine shuts off.

I think a properly designed PCB could handle well over 100a of total current, so it really depends on how many loads and how big they are. For a lot of small loads, a PCB with PCB-soldered multipin connectors would be the way to go, but for a few 40-80a fuses a bus bar would be better. I've also seen busbars with fusing mounted directly on the battery, with outputs for the main fuse box and a few extremely big loads. These are 80a+ fuses normally.

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke

Here's a link to pretty good instruction for building a wiring harness:

https://www.rbracing-rsr.com/wiring_ecu.html

Have heard of people doing this but never knew how well it worked out for them. Obviously there will be different levels of skill depending on who does it, but I can't help but wonder about the long term reliability of a pigtail type connection vs an OEM connector, molded onto the sensor. I would think the potting would certainly improve the reliability of the connection, however.

It's a pity someone like Deutsch or even the Japanese (Sumitomo, Hitachi, etc.) doesn't make a new, improved connector for Bosch sensors which would offer better sealing, and better pin connections than the AMP.

Funny, was just reading that!

I've read that one as well

_________________
"Sometimes, the elegant implementation is a function. Not a method. Not a class. Not a framework. Just a function." ~ John Carmack

"Any sufficiently advanced technology is indistinguishable from magic" ~Arthur C. Clarke