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Hi all,
Lately I've been looking at this system and various applications that its found its way onto - in particular the Triumph sixes. It seems a remarkably simple solution, yet mechanical injection never seems to have been as big a hit as carbs for whatever reason - despite it being on the face of it a better solution.
I was wondering if anybody has had experience with this system, could comment on it, or knows of any uses besides the Triumphs in road car usage.
Regards,
Rich
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"You're about as likely to come across a fully functioning old Jag, as you are a taxicab that smells agreeable." - James May
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I don't know about the Lucas system but my E reg Volvo 240GL had a 2.0 engine with CIS injection (Bosch Continuous Injection System) that was 100% mechanical. Worked fine.
Paul h
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Onne
Part of things
Posts: 822
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My Merc has mechanical injection of the continuous variety. Almost fully mechanical (KE-Jetronic)
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1990 Mercedes W126 300SE
1997 Mercedes W140 S320L
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In the Triumph it had a rep as being very unreliable and hard to keep in tune.
(but then its Lucas so what do you expect?)
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Last Edit: Jul 5, 2013 16:16:52 GMT by mdh
Koos
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andyborris
Posted a lot
Freedom is just another word for nothing left to lose.
Posts: 2,153
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I think there are 2 main problems with Lucas (Triumph) injection, one is that it's all to easy to mess up the settings. Too many mechanics who didn't understand the system, blamed it (Lucas injection) for faults that had a basis elsewhere, ignition problems for example.
Once it was "fiddled" with, it was very hard (or impossible!) for them to get it running right again.
Obviously, they're not to admit to messing up, instead they blamed Lucas "Prince of Darkness"! Human nature.
I also believe that the fuel pump wasn't as good as it needed to be, a popular modern modification is to fit a Bosch pump.
Lucas FI is very popular in the USA, but mostly using a mechanical pump and is (I think) still used on dirt track cars.
The knowledge is out there and some of my friends are able to get lots of horsepower and surprisingly good MPG from Lucas FI equipped Triumphs.
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When working properly and correctly set up it very effective and gives good power, reasonable economy and good reliability. It is a true, fully sequential, high pressure system.
It suffers from
Ignorance - very few people have ever properly understood it, though plenty have been prepared to tinker with the inevitable results. In fact it is quite simple once understood and DIY possible. There are some intelligent owners out there now armed with wideband O2 sensors and patience who are getting very good results.
The insistence by Triumph/Lucas back in the day, and specialists today, that the metering unit can only be set up correctly by special calibration rig and no matching to the car is necessary. Yeah, right - so all engines are identical?? The MU takes its load sensing from the manifold vacuum so all sorts of factors can upset the real world calibration even on a standard engine. Valve clearances, ignition timing, engine condition...... They tend to get set safely rich, and then go richer if vac levels drop for any reason, which fosters their rep for epic thirst.
Having 6 HUGE (46mm) throttles in 3 pairs linked by a very crappy, wear prone linkage. Good balance is essential to decent idle, smooth part-throttle running and economy. Good balance is hard to achieve with the linkage in as new condition, impossible with anything less. Some after market ones are a bit better. It is possible to run them with a single TB on the end of the plenum which sorts all balance issues.
The fuel pump. Though actually the pump itself is probably quite often the victim rather than the cause. Obstructed suction filters and poor power supply lead to overheating and cavitation. The aftermarket "cooling coils" you sometimes see wrapped around the motors may make matters worse by heating the fuel up and making it more prone to cavitation! People use Bosch pumps these days but that is not entirely issue free either.
No altitude correction whatsoever. Not a problem in UK but leads to very rich (impossibly so if they were on the rich side to begin with) running on the higher Alpine passes.
Crappy Lucas ignition systems. 80% of all injection problems are solved by mending the ignition.....
Nick
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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From memory the pumps used to wear, the fuelling go out and bore wash would result.
I cant see any reason to use an old mech system over a full efi....
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Koos
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From memory the pumps used to wear, the fuelling go out and bore wash would result. I cant see any reason to use an old mech system over a full efi.... Well, you can still buy (retro) cars that come with it already fitted. And converting to full EFI is alot of work (speaking from direct experience x 3). Mechanical systems (especially the HP sequential ones like Lucas & Kugelfischer) can do a very good job, probably better than early batch fire EFI systems for power. Lucas PI goes rich mainly due to vacuum problems - it relies on the manifold pressure to give it it's engine load "signal" so vac leaks make it "think" there's more air going through the engine than there actually is and it fuels accordingly. Nick |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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they were an aircraft system and not really suited to varying rpm as seen in motor vehicles.
Jaguar used it on the works D types and later the Lightweight E Type. it came with butterflys or slide-throttle. the slide-throttle system worked better as the injectors pointed outwards towards the throttle rather than down the inlet (this helped the fuel/air mix for a better burn) as well an no restriction in the inlet.
as said the light throttle vacuume system did not like air leaks and will not work with wild camshafts. there is a mechanical system for the load signal but they are quite rare.
power is not affected by having the injection out of phase with the inlet valves. a little bit of drivability is lost but that is about it. they need to run 105 psi fuel pressure to work properly and it's advisable to run a little bit of two stroke to lube the fuel distributor. they don't work very well in cold climates as the tolerances are quite tight so can jam solid if too cold.
at full throttle the amount of fuel injected per stroke is the same at 2000 as it is at 6000. pretty much stuck with a 2 dimentional system hence quite difficult to tune with limited variability.
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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Lucas PI (Petrol Injection)ChasR
@chasr
Club Retro Rides Member 170
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I'd agree with andyborris and VitesseEFI after mucking around and seeing a couple of these system. I have not heard of a Lucas fuel pump wearing out and overfuelling, quite the opposite (no fuel at all due to cavitation).
On song they are good bits of kit, now that there are good people out there to get them working right (Prestige do this very well). However, as with any trade there are a number of bodge monkeys out there who are all too happy to capitalise on their 'poor' reputation. A good friend of mine had his metering unit and pump refurbished by a known bloke in the circles. The metering unit upon fitting it did not really meter and leaked like a sieve (just what you want in a hot engine bay). The second bloke/company who took it apart said there was no way it had been refurbished, but cleaned from the outside (I believe the first bloke stopped trading or something to that effect). To this day that unit still works well. It was a similar story with the fuel pump. I did feel for the guy truth be told when the pump died (after all, if he was shafted on the MU, there was a very good chance he was on the pump too). I have seen quite a few Lucas pumps that seem to work well though.
You can go to the Bosch pump, but this can be a mixed blessing as well (the Lucas pump runs a very high pressure and a lowish flow rate, whereas the Bosch items are the opposite; Some people 'make' them work at a higher pressure and attempt to reduce the flow, whilst others work with how the pump is designed to run and adapt the PI system to suit.
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So to summarise all of that ^, its a flawed system for use on a modern automobile.
If you want to convert a carb car to injection, use a modern EFI system which gives better fuel control, better reliability and ignition control.
:-P
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Koos
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So to summarise all of that ^, its a flawed system for use on a modern automobile. If you want to convert a carb car to injection, use a modern EFI system which gives better fuel control, better reliability and ignition control. :-P Sure, no argument with that. But if you have a retro car which was born with it, don't dismiss it out of hand. Nick |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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I still have a soft-spot for the Bosch Jetronic... the purely mechanical version mind you, not the newer semi-electronic type  |
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You're like a crazy backyard genius! |
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that is a totally different system with one single butterfly and a airflow plate. all injectors squirt continuously. the Lucas system has individual throttles and sequential injection, basically an early ITB set up.  |
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Last Edit: Jul 9, 2013 19:44:13 GMT by Bozwell
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ps i'm looking after this car at the festival of speed if you want a closer look   |
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ps I'm looking after this car at the festival of speed if you want a closer look Ooooff! Jammy git!  |
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Koos
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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Lucas PI (Petrol Injection)ChasR
@chasr
Club Retro Rides Member 170
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So to summarise all of that ^, its a flawed system for use on a modern automobile. If you want to convert a carb car to injection, use a modern EFI system which gives better fuel control, better reliability and ignition control. :-P True, but in that case, half of our retros could probably not take the punishment that many a daily can take  . To put it into perspective, the V6 Mondeo in my signature was at one point doing almost 2,000 miles a week over a period of 7 months. I can't imagine any of my retros doing that (the Porsche is currently doing 2-300 a week and is fine, but the above is some severe punishment for any car). No denying the fact that modern EFI on a retro can improve matters. It is a thought that many have come across time and time again (myself included on some cars ) . |
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Last Edit: Jul 9, 2013 21:14:15 GMT by ChasR
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Why not?
Ive used retros almost my whole life and have clocked 1000 miles ++ a week regularly.
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Koos
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Jul 12, 2013 13:53:41 GMT
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that is a totally different system with one single butterfly and a airflow plate. all injectors squirt continuously. the Lucas system has individual throttles and sequential injection, basically an early ITB set up. Om-chuffing-NOM!!  I thought it was just the Lucas version of the Bosch setup, but that just looks lovely! Is there online links with more info on the setup? |
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You're like a crazy backyard genius!
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Jul 31, 2013 11:12:51 GMT
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My knowledge of the Lucas PI system is all 2nd hand from my old man, who used to rally these system sextensively, and also look after them for other people.
Essentially, my understanding is as posted above. It was a mis-understood system, which was immediately blamed for any source of bad running. Once captain bodgit had had a play with it, it never ran right.
The original Lucas pump was a source of problems, as it was not really fit for the task, being a modified windscreen wiper motor!
The Lucas PI system though, was fully sequential, with a very high pressure, very fine jet pattern.
It was utilised in a great number of competition cars in its day and should probably viewed as a competition setup which was adapted for road cars.
After struggling with a set of worn out SU's on a friends 2500 Triumph engine the other week. I'm not convinced carbs are necessarily as 'easy' as often made out either.
Both systems in good shape will work well, but a PI set up in good health will make more power than carbs.
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. To put it into perspective, the V6 Mondeo in my signature was at one point doing almost 2,000 miles a week over a period of 7 months. I can't imagine any of my retros doing that (the Porsche is currently doing 2-300 a week and is fine, but the above is some severe punishment for any car).
