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[Stu.C]

Did aircon and non-aircon cars have different coolant temp sensors, or do you think I've run into an oddity in the Haynes diagrams? 

I'm deleting the aircon from a '98 X30XE and my current wiring harness tallies with the left side of the below with pin 3 of the sensor being the trigger and pin 1 the ground. But on the right side (for a non-aircon car) it's telling me that the trigger would be pin 1 and pin 3 the ground, which would mean a different sensor...?

[Doctor Gollum]

Ignore them.

Those are the thermo switches on the radiator, not the ecu or gauge sensors.

Just remove the plumbing and condenser and compressor and tape/tie the compressor wiring back up under the battery tray and find something more important to worry about

[Stu.C]

 

The engine's destined for some future (non-Omega) project, so I'm trimming back the harness to suit and chopping out what's now a bunch of useless relays. I'll re-plumb it to run the radiator fan in the simplified layout and the existing trigger pins.

Mostly it was curious that it looked like a different thermo switch was used for non-aircon cars. If it were indeed the case, perhaps they had different switching thresholds due to the lack of a condenser in the way of the airflow...   

[Doctor Gollum]

The stock aircon fan set up works well as a stand alone cooling system. 

Or to put it another way... It is what RobseyMV6 is using in his Supercharged V8. And it can keep that cool, it should be fine in most anything else

[Stu.C]

  I hear what you're saying DG, but for what will remain a stock engine with no aircon and possibly limited installation space, the extra complexity, wiring, relays, sensors & fans are going into the spare parts cupboard...

Finally found the right search terms combination that satisfied me other folk have been down that path before... 

[Doctor Gollum]

No problem

Point being that it is quite clever in that it runs the fans independent of both aircon and engine ecu input.

There's been a couple of Scimitar builds, and Nick W recently documented an MGB  conversion which should provide some helpful info

[Nick W]

I hear what you're saying DG, but for what will remain a stock engine with no aircon and possibly limited installation space, the extra complexity, wiring, relays, sensors & fans are going into the spare parts cupboard...

Finally found the right search terms combination that satisfied me other folk have been down that path before... 

The radiator transfers heat in the coolant to the air passing through the core. The best way to ensure that happens efficiently is to use the 200hp source fitted behind it to force the air through.


The fans are only for when the car isn't moving, so you want the biggest that will fit, wired through a thermo switch to turn it on early. To get the maximum benefit, the radiator and fan(s) need to be shrouded so the fan pulls air through the entire core. The stock Omega setup already does all of that reliably, and comes free with the car, so why mess with it?


As for removing the AC, the heating and ventilation is much better when it's working. Which is hardly a surprise, as it's designed as a system.


With the MGB we used the biggest stock radiator, one that will cool a V8 that takes up all the space under the bonnet. It's still smaller than the massive Omega part. It has a boss soldered to the top tank to take a stock Omega fan switch. The fan isn't the biggest we found that would fit, simply because they were out of stock.


We were prepared to take extra measures to reduce under bonnet temperature, like wrapping or coating the manifolds, heat shields, or vents or standing off the back edge of the bonnet. We've used all those before in cars that did have cooling issues - our Sunbeams gained extra power and better low speed drivability with louvres over the back carburettor. None of those are necessary  with the MGB; the engine runs at normal temperature when the car is moving, and the fan cuts in and out in traffic.

[Stu.C]

Indeed - those well-known Scimitar projects and latterly the MGB have been on my radar for years, back since mid-2015 and onwards I've got probably hundreds of screengrabs, photos and scribbled notes from other folks' highs & lows tucked away in Evernote 

For the sake of brevity, I'd not mentioned that the aircon was dead on my donor car when I got it in 2016, and when I did once got a fella to hook it up to his tester-ma-jig, it had more holes in it than a pack of Polos.  For a car that cost me next to nothing, it just wasn't worth the expense & effort to go buying condensors & such and chasing leaks around the system.

Fast forward to now, and rest assured Nick that whatever it does end up in eventually, I'll be heeding your sage advice on shrouding and flow.

[Nick W]

We'd have fitted AC to the MGB if there had been room for the compressor.....

[countrywoman]

Looks like your going down the same route I am with my Austin hot rod, there is a lot that can be trimmed from the loom. Have just gone to one fan relay but looks like due to room it will have to have a super slender fan and a custom rad.

[Nick W]

I should point out that the only Omega wiring in the MGB is the engine loom, everything else is MGB. Which is how we did other EFI swaps.


The cooling fan uses the thermo switch in the radiator, a relay and the battery connection.


There's no way I would attempt to make an Omega loom work in an old, simple car. It's far too much work for no gain.

[Stu.C]

Great minds think alike 

My goal is to strip the Omega loom back to engine & associated sensors/fan/pumps, only the relays needed to drive them and then the feeds out to the dash display & MID. The other quarter tonne of wiring harness goes into the spare parts pile That means I can play about with the engine to my heart's content whilst it's sat on a standalone trolley, and still see the tach, CEL, paper clip tester and such like.

If it turns out that I then use the Omega instrument panel in the eventual target car, I could just branch off a connector and have that car's indicators, headlights and so forth feed into the Omega panel. If it goes the other way and I want to make the Omega's output drive the target car's dash, then I've got a fully functional basis from which to develop any signal adaptors - it's the harder path, but if original looks are important then that could be the decider. Trying to adapt a whole Omega loom to something completely different is definitely not something I'd want to take on though - life's too short!

Either way, I'm in no rush and it's a fascinating learning exercise on a pocket money budget... 

[Nick W]

Great minds think alike 

My goal is to strip the Omega loom back to engine & associated sensors/fan/pumps, only the relays needed to drive them and then the feeds out to the dash display & MID. The other quarter tonne of wiring harness goes into the spare parts pile That means I can play about with the engine to my heart's content whilst it's sat on a standalone trolley, and still see the tach, CEL, paper clip tester and such like.

You're making this much more complicated than it is.


There's no need to strip anything, just unplug the round engine-loom plug.  Read THIS


You can get the engine running on the floor with 3 or 4 connections, and have it in a fully working car with another three or four.

Trying to use the Omega cluster is more work, and is unlikely to be a pleasing fit in an old dash. More modern rev counters can be driven directly off the ECU, and adjusting a temp gauge to read right isn't hard. Use the car's fuel gauge and sender. Oil pressure gauge are a waste of space, and tend to be mechanical in older cars, so are easy to adapt. Aftermarket electronic speedos are cheap and easy to use. The MID offers nothing of any use to make it worth bothering with.

There is some extra stuff to remove from the engine; binning the EGR and SAI removes a lot of clutter, and losing the vacuum operated HBV for whatever the car uses does a similar job at the back. Removed from its bracket, the DIS pack can be moved to wherever there is space. A new water rail isn't hard to fabricate if there's no room for the  original.

[Stu.C]

Aha - that's an awesome set of resources, thanks Nick. Ian's really been to town documenting stuff since the last time I saw it. I'll sit down with a cuppa at the weekend - pass on the appreciation when next you see him...

It's so long since I drove the Omega that I can't really remember what level of info the MID gave - mostly I recall it whinged at me to check the brakelights The HBV has gone already, replaced by a loopback whilst it's running on the stand. SAI hardware has similarly gone, and I'll replace the solenoid's relay with a resistor. EGR is mentally on the 50/50 list at the moment - it may get left if I ended up staying on stock headers, it may go if I don't or I want the space back; call me ambivalent on it at this stage


But like I think I said elsewhere before, this is way beyond the level of what I've done on cars before, so it's all good learning for me. Even just stripping the donor shell gave me a way better understanding of how "modern" stuff hangs together compared to the simplicity of the Capri.

[Nick W]

Capris, I've had a few....
This was the last one, £75 worth of drivable Scorpio turned it into the car the 2.8i always pretended to be:





Started at 17:00 Friday with a driving car, and had it running with all the conversion work done less than 24 hours later. 3 hours of that was converting to manual steering. I had another evening making and fitting the box for the air filters.