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Re: Leonardo induction system in a 50year old Jasguar

Posted: Thu Dec 29, 2011 6:31 pm
by Gilbertd
Mine does...... It tunes the default no matter what the revs are.

Re: Leonardo induction system in a 50year old Jasguar

Posted: Fri Dec 30, 2011 10:02 am
by rossko
SimonHobson wrote:Actually it doesn't tune itself at idle.
Not convinced about that, but this Leo doesn't know when its at idle ...

Re: Leonardo induction system in a 50year old Jasguar

Posted: Tue Sep 03, 2013 10:03 pm
by minimutly
Sounds an awful lot of faffing about to me. An engineer I was talking to recently told me how his fuelling is done by using the su itself to draw the gas in -by connecting the gas in at the bottom of the su where the jet holder used to be. Sounds like a grand idea.
Not sure what the lpga would say about it though "not an approved part sir" ....
Huw

Re: Leonardo induction system in a 50year old Jasguar

Posted: Tue Sep 03, 2013 11:08 pm
by Gilbertd
No, but that's almost exactly what a Blos gas carb is. Something very similar to an SU but with the gas feed going in the bottom.

Re: Leonardo induction system in a 50year old Jasguar

Posted: Wed Sep 04, 2013 8:12 am
by SimonHobson
In principal not hard to do at all.
Just remove the innards of the float chamber (and seal off the vents/overflow etc), make a larger jet and needle (you need a metering needle as it's a variable orifice), and connect the gas supply to the float chamber. And then tune it !
Should be able to do away with the in-line restrictor (power valve) as the needle & jet can take that role.

I guess for some people interested in trying to keep as much of the authentic look as possible it would be worth it. As Gilbertd says, you can buy "gas carbs" and it's probably easier to adapt an inlet manifold than the SU carb.

For other types of carb, people have done it with a spud pipe - literally just a piece of pipe sticking into the intake where pressure is depressed, ie into the venturi. For fixed orifice carbs, that's the simplest way to convert them.

The biggest downside of removing petrol components is that you have then completely lost the ability to switch to petrol. As someone with long term experience of having a gas-only vehicle, that can be a tad inconvenient if you travel around a bit.
Nothing quite beats the anxiety of finding one filling station out of gas, and doing an "economy drive" to the next one - knowing that according to your calculations you probably won't make it ... (I did, but with dry tanks :shock:)
Or you end up carting a big red cylinder and hand pump with you. Not too bad in something large like a 110 or Discovery - probably not very practical for most cars.

Re: Leonardo induction system in a 50year old Jasguar

Posted: Fri Sep 06, 2013 8:48 pm
by Martec
I've just seen this old post of mine resurrected for some reason!

To update you on the car, I built it with two fuel systems and two ignition systems for reliability and alternatives when touring, UK or Europe.

The car has been running very well after a few more changes, I fitted a set of iridium plugs to get more longevity from them, a very good Jaguar friend gave better ignition advance figures for LPG and petrol for the switchable ECU and I binned the new cheap Lambda probe and went to another friends scrap yard and took second hand probes from ford escorts to test plus the corresponding plug (so that a ring spanner would go over the plug to remove the probe from the exhaust).

Also plumbed the vacuum advance pipe directly into the manifold rather than the carburettor as per the distributor connection.

I tried about 3 Bosch and 3 NTK probes and found the Bosch leaned off the mixture but the NTK kept it in the right place. Still running on the old NTK probe with 2 spares in the boot.

The only real problem of late was coming back from Birmingham on the A/M42 and M1 and two petrol stations had broken LPG pumps so ran on petrol at 18mpg! and motorway prices.

Brian