Adding a Leo unit

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Adding a Leo unit

#1 Post by DodgeRover » Mon May 30, 2016 9:47 pm

Hi all.
Adding Lambda control to my carb'd pinto to see how it works with the Blos, am having problems with it going rich under heavy load.
Well the air/ fuel ratio gauge is telling me it is going rich anyway, I can't really tell anything from the drivers seat. Emisions both at idle and 3000 rpm when not under load are fine according to the MOT and my gunsons gas tune set..
Couple of quick questions, is there any issue with installing the leo unit inside the vehicle rather than under the bonnet and is there a recomended Lambda sensor to use? My existing narrowband bosch one shows it running pretty much stoichiometric on petrol but i'm not sure how its is reacting when running on gas (i.e if its accurate - or anything like).

The pinto is dragging a LWB transit round so it does spend most of its life under reasonable heavy load :)

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Re: Adding a Leo unit

#2 Post by LairdScooby » Tue May 31, 2016 12:22 am

As long as the Leo unit is away from heat and moisture, i see no reason why installing it inside should be a problem. As for the Lambda sensor, how close to the actual exhaust manifold are you able to mount the sensor? If you can get the sensor more or less in the manifold, you could go for a simple, single wire, £10 universal jobby such as this one : ... EBIDX%3AIT

I buy them in pairs for my Rover 827s as they are the correct sensors believe it or not and there is one per bank on mine and had no problems so far.
However, if you are planning on putting the sensor a bit further downstream in the front pipe or even further back then you'll need a heated universal sensor and will need to sort a power feed for the heater in it.
The big drawback about fitting the sensor further back is that the mixture control will take longer to update to any changes so the closer you can get it to the front and/or the exhaust manifold, the better.

If you have an existing Lambda sensor, just tap into the wiring for that. Top tip given to me by another member on here (Gilbertd) is to just use the purple wire from the Leo, cut the wire to the Lambda and solder the purple wire into it making sure you rejoin the original wire. If you can scrape enough insulation off the original Lambda wire to make a loop you can connect the purple wire to then solder it, even better as it saves cutting it and remaking it. Don't forget to heatshrink it afterwards as well! Also tape or heatshrink the end of the grey wire from the Leo so that it can't short out anywhere.

I don't know much about the Blos things, aren't they a bit like a sidedraught SU/Stromberg carb but for LPG? All the Pinto engines i've ever known have had downdraught carbs so if the Blos is a sidedraught animal it may be tricky to fit and/or get working right. Maybe someone else can give better information on the Blos as that's about all i know about them i'm afraid.

Somewhere in Suffolk with a Jeep, 2 Rovers and a V6 Volvo


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Re: Adding a Leo unit

#3 Post by Gilbertd » Tue May 31, 2016 8:27 pm

Don't use a 1 wire lambda sensor, use a 3 or preferably 4 wire. The Leonardo isn't intended to use a wideband sensor, it works best with a cheap n cheerful 0-1V Zirconia sensor although I steer clear of those from the Chinese Universal Lambda Sensor Company as my experience is that you're doing well if they last a year.

As the lambda sensor is going to be stand alone, then all it needs is a 12V heater supply, ground and signal straight to the Leo. Make sure you have a decent ground as even the tiniest resistance can have a big affect. When you are looking at a signal between 0.1 and 0.9 Volts, any volt drop will throw the readings out completely. The Leo will assume that a signal centred on 0.5V will be correct and will tune to achieve that. If the lambda is swinging between 0 and 0.8V due to volt drop, tuning for 0.5V will result in a rich mixture as it should be aiming for 0.4V, the mid point.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

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