Can anyone help me construct a "relay board"?

[benjy_b]

Hi there,

I'm wishing to construct a simple "relay board" or "power distribution board" so I can run my engine outside of the car. I noticed there are many cars on this forum running a self-contained centre console, with all the control wiring, fuses and relays build into it. I'm thinking something along those lines, but on a smaller scale (no lights, indicators, hazards, etc).

The engine is a F20C from a 2001 Honda S2000.

I have:
Engine
Engine Loom
ECU
Dash Gauges
Dash Loom

I'm more than confident to wire something up myself, however, I feel I may be over-thinking it a little.

Here's what I'm thinking I need:

Battery
Battery Isolation Switch
Ignition Switch
Starter Switch
Fuel Pump Switch (although may not be required as it is switched form the ECU)
Main Relay - takes the load off the ignition switch and distributes a "switched live" to the remaining relays
Ignition Relay - powers the coils
Starter Relay - powers the starter solenoid
ECU Relay - powers the ECU & Injectors
Fuel Pump Relay - powers the Fuel Pump
Fuses - appropriate fuses for all the above

Now, here's where my "over-thinking" starts...

Do I fit the fuses before or after the relays?

Will all the relays have a constant live through the 30/87 side or shall I wire some to have a switched live?

How do I distribute the power neatly to each relay?
- bus bar
- large ring terminal spliced with numerous wires to each relay
- piggy-backing each relay

Do I switch/trigger the relays on the positive side or negative side?

Rather conveniently, there is a thread by para144 (http://www.turbosport.co.uk/showthread.php?t=252983) detailing a very nice centre console build but there are no diagrams. I can see how he's wired up a few items, but the rest just blurs into a copious amount of wires.

Thank you for taking the time to read my post.

If anyone requires any further details, please feel free to contribute.

Ben

[Graham]

thats a lot of questions it may help if you say what your actually trying to do here, i know run an engine outside of a car, but is this just to test run it or some kind of rig for demonstration purposes

[Graham]

to answer a few of your questions,

you dont need a fuel pump switch , the pump relay is switched by the ecu.

you can fuse either side of the 30/87 terminal if the fuse is overloaded the current flow would stop either way.

relays are almost invariably switch on the negative side because thats how ecu's are wired, negative switch whether its injectors relays or anything else.
the ecu its self only need a small current 1-2A only, so are often are not wired with a relay, if they are it would be best done seperatly from ignition coils or injectors, infact its not unusual for injectors and coils to be on the same relay

[alladdin]

Have a look at my Westfield project (search hole in head ) I did a relay board similar. Relays are v easy, IRS the ecu and sensors that are more complex to wire, if you do an engine loom.on plug you can reuse it if later fitted in car

[benjy_b]

Hi,

Thank you for your prompt responses.

The engine is currently fitted in a vehicle but it hasn't ran for four years. In the short term I am wanting to rig up a simple power distribution circuit to power the engine sensors & ancillaries, ecu and gauges. Firstly, to confirm no problems have developed over the four years and secondly to start ironing out all the codes the ECU will generate with the air pump and emissions gubbins removed.

Over the long term my intentions are to re-wire the whole car using a Racepak Smartwire PDM. Therefore, I didn't want to start a complex centre console.

I understand vehicle electrics to a competent standard, however it's all self taught. I've never had anyone direct me with my work. With this specific situation, I can see a number of solutions but am finding it hard to determine which one would be best. I really want it to be neat and tidy but I'm lacking the initial confidence to go in one direction.

[alladdin]

I am a little confused , if it's in the car then it should run as is ?

[Graham]

me, to now, if its in a car then surely best thing to do is getting it running as it stands

[benjy_b]

Sorry for the confusion.

The F20 engine is fitted into a 1983 Toyota Corolla AE86. When I purchased the car five years ago it was running on an aftermarket VEMS ECU with a crude map and rather scary wiring. At the time the car had an intermittent misfire, which was diagnosed to be a faulty coil connection at the ECU.

As with a lot of projects, I set out with good intentions. I removed all the VEMS wiring and had the great idea to wire the car up with the factory ECU (as this would be more reliable and would work just how Honda intended).

Then life got in the way...

Fast forward to the present and I've recently had a burst of enthusiasm for the car. Resulting in my enquiry.

I'll add some pictures to save us from all the text.

Engine in question, sans wiring loom:


Start of the engine loom:


Getting there:


Gauge sub-harness:

[Graham]

i see, but using the factory ecu etc, just puts a whole load of complication for no real gain, wiring an aftermarket ecu is much simpler, plus you dont have to try and "get round" immobilizers, missing air pumps etc, plus you gain the ability to fiddle with the mapping to your hearts content.

if i were you i would start with a factory honda engine loom and modify it to fit an emerald ecu

[benjy_b]

I understand that aftermarket ECU's are favourable in the motorsport industry. In most cases they work brilliantly.

In my case, I see an aftermarket ECU being more hassle than wiring in the standard unit. I won't bore you with all my reasons to justify this but the main one being cost. I would have to initially buy an aftermarket ECU, then I would have to get the car mapped on a rolling road, add to the hassle cold starts, hot starts and all the variable geometries of fuelling and ignition = mucho £££.

With the standard ECU, Honda spent thousands in R&D to extract a reliable amount of power from the F20. Furthermore, there are inexpensive aftermarket workarounds for the small hurdles I face with the immobiliser, air pump and EVAP.

Talking about the additional complications around using the standard ECU...

The O.E.M engine and dash wiring looms are modular and each self contained. There is a plug called the C101 (chassis plug) which requires 1 constant live and 4 ignition lives to fire the engine up (excluding the fuel pump and the gauges).


My initial post was merely to ask for help with the distribution and protection of the power supplying said looms.

[Graham]

In my case, I see an aftermarket ECU being more hassle than wiring in the standard unit

that is rather at odds with what your asking, if wiring the oe ecu is easy why the questions?

and unless the installation is exactly as per honda, including full exhaust system airbox etc etc then the honda oem map wont be 100% correct anyway

[benjy_b]

I understand we are divided in our opinions of which engine management to use, but we are digressing from my original post.

I agree with the standard map not being 100% for my application (The exhaust manifold is extended 1" to clear the steering column and I have an aftermarket exhaust silencer). However, many an S2000 owner has fitted an induction kit, cat back exhaust or rear silencer without the requirement of an aftermarket ECU. The standard ECU will happily work within the parameters you give it in those instances. Now, throttle bodies, cams, stroke kits or forced induction is a different matter.



Anyway, whether I use an aftermarket ECU or standard ECU I still require the use of a relay panel or power distribution circuit, that's what I'm after advice on.

[Erikmex]

If your using a std ECU etc why not just follow an s2000 wiring diagram for you supplies

[benjy_b]

If your using a std ECU etc why not just follow an s2000 wiring diagram for you supplies

That's basically what I'm wanting to do.

I'm just after advice on making it simpler.

[alladdin]

i think your misguided in your views regarding the std ecu versus aftermarket tbh but its your choice so best of luck
have a look here, post 56 i think http://www.turbosport.co.uk/showthre...ight=hole+head
i split in two , those with a constant live (main beam etc), and those fed from ign relay. cable size is important.
fuses are in the load side ie between supply and relay, then its all protected, switched sides dont need fuse but it doesnt hurt either.
switching relays will be both polarities depending on use ie fuel pump is sometimes earth switched by ecu.
thats a start.

[benjy_b]

Thank you for the link

I'm confused now

Am I misguided in my opinion that wiring up the standard ECU is just as easy as an aftermarket ECU?

or,

Am I misguided in thinking that the standard ECU would better suit my application than an aftermarket ECU?




I have taken the opportunity to draw the standard wiring diagram for the Honda S2000 (the items I'm trying to wire):




Can anyone shed some light on what may be a more straight forward way of wiring this?