Hotwire system tune resistor.

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jenand40
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Hotwire system tune resistor.

Post by jenand40 » Fri May 03, 2019 8:18 pm

I have a 4.2 Rover V8 hotwire EFI system (fitted with a Tornado chip) engine in my car which is not fitted with catalytic convertors. I had reason to remove the exhaust system and whilst it was out i took the opportunity to fit lambda bosses to the front downpipes, i already have the Lambda sensors. These are now fitted but i am unsure of the value of tune resistor i should fit, yellow (910 Ohm, non cat) or Blue (1800 Ohm, cat). Tried emailing Mark Adams but never got a reply. Can anyone advise please? Was there any value in doing this mod, understand that the Lambda sensors control the fuelling better. Any advice appreciated, thank you.



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richardpope50
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Re: Hotwire system tune resistor.

Post by richardpope50 » Tue May 07, 2019 4:47 pm

I can only say that when I initially ran with Hotwire I fitted the correct non-cat tune resistor and it all worked fine. Then I switched to Megasquirt and it was not needed.

Why not simply fit one? It simply plugs into the standard loom. I think I may still have mine somewhereif you want me to look for it. I still have the 14CUX ECU.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control, ABS and Quaife LSD

GDCobra
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Re: Hotwire system tune resistor.

Post by GDCobra » Tue May 07, 2019 7:39 pm

Why do you want to fit Lambda sensors when you don't have cat's? What are you hoping to achieve?

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Ian Anderson
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Re: Hotwire system tune resistor.

Post by Ian Anderson » Tue May 07, 2019 7:44 pm

So question here!

What happens if you get a variable resistor and put it in the circuit?

1 2 3 or 4 marks on the dial for the different set resistances and then try, drive, put on rollers and see how it goes?

Or is that just looking for trouble?

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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ChrisJC
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Re: Hotwire system tune resistor.

Post by ChrisJC » Tue May 07, 2019 8:19 pm

This is a total guess, but I wonder if having the lambda sensors and cats and appropriate tune resistor puts the ECU into a closed loop mode under certain engine conditions (probably cruise). So if you have fitted the sensors, you might as well fit the resistor and see how it goes.

Chris.
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jenand40
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Re: Hotwire system tune resistor.

Post by jenand40 » Wed May 08, 2019 7:53 am

Thank you for your replies.

Richard - I have a tune resistor fitted, i just wanted thoughts on which is the correct one. Thank you for your offer though.

GC Cobra - As the exhaust down pipes were off, and i had the lambda sensors, just took the opportunity to fit them. Was hoping someone on the Forum could tell me if i was wasting my time, or not.

As the car has not been used, on the road, since the sensors were fitted think i will remove them and use the correct yellow (910 Ohm, non-cat) tune resistor, this will give me a benchmark to work from until its on the road.
Again thank you for all your replies.

GDCobra
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Re: Hotwire system tune resistor.

Post by GDCobra » Wed May 08, 2019 5:32 pm

jenand40 wrote:
Wed May 08, 2019 7:53 am

GC Cobra - As the exhaust down pipes were off, and i had the lambda sensors, just took the opportunity to fit them. Was hoping someone on the Forum could tell me if i was wasting my time, or not.

As far as I've ever been able to tell there is no (performance) advantage to fitting the standard, narrow band Lambdas, they only work at times when the ECU is looking for a stoich mixture and are only used on production vehicles for emissions purposes.
Obviously if your motivation is emissions then fair enough.
You may arguably get better MPG too.

To make it work you need the correct tune resistor, can't remember which it is for a closed loop/Lambda map.
I believe some people have used either variable resistors or a switchbox with a number of fixed resistors to allow map switching, don't know how well that works but sounds like it should be no problem. Think the system only 'reads' the resistor at startup so won't switch in real time.

Have you looked at www.remap-14cux.uk?
Lots of useful info' and links.

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