Nick davies

[N. J, Davies]

Hi,

 

I've a query regarding electronic fuel injection. It seems that most if not all systems have the fuel rail mounted directly on to the injector itself. Is there any reason why the fuel could not be provided from a remote reservoir and transferred to the injectors via separate lines? The injectors would driven from an ECU.

I have a TR6 so I'm thinking that the metering unit could be replaced by the reservoir and the original nylon fuel lines used from there to the injectors. Does this make sense or are there any foreseeable problems.

Views would be most welcome.

 

Regards,

 

Nick.

[JohnD]

You mean like Lucas Pi?

[Nick Jones]

In theory it could work. In practice it will be much easier to do it with a fuel rail. Apart from a select few cars from the late 70s and early 80s, which have hose tails, electric injectors are designed to plug into a hole/socket in pipe/rail that goes across the top of the the whole row of them and also serves to clamp them down. 

The mechanical type used with the PI system are wholly unsuitable.

If you have a look through this

you’ll find some details of the PI -> EFI conversion I did on my saloon a few years back. If you have a rummage in the “members cars and projects” section using “EFI” as a search term you’ll find at least two more.

I helped a friend convert a TR6 a few years back using very similar methods and it worked very well.

Hope this helps!

 

 

[RichardB]

Others have explored this sort of route to varying degrees, though I've never seen a working implementation. For example could you make an electronically controlled metering unit and then leave the original injectors in as well. I think the barrier is more likely to be a combination of a high degree of complexity in fabricating something, and then when you've finished the thought that it still looks clearly quite modified. Modern EFI injectors will require custom bracketry and a different way of attaching the fuel pipes. You may also find there's challenges regarding consistency of fuel pressure and guiding the return fuel flow back to the tank, though I think the former is probably surmountable and the latter not strictly necessary.

I admit I do have a soft spot for the appearance of the fuel pipes draped over the rocker cover, it's an iconic design feature I think of with the TR6. If I was going to convert one to EFI though, I would be much more likely to use a fuel rail and throttle position sensor. You could still fabricate something that mostly looks like it was made in the 1960s.

Edited January 16 by RichardB

[N. J, Davies]

Thank you all for the response.

Using the Lucas metering unit and driving it electronically from an ECU would be difficult to achieve - me thinks and personally I've dismissed the idea.

Fabricating bracketry to retain the injectors would need some deep thought and as would how to attach the fuel lines fuel lines - not insurmountable.

EFI systems need a return to the tank that is larger than that required by the Lucas metering unit so that is necessary mod with any EFI system. 

Would there be an appreciable pressure drop between the 'reservoir' and the injectors. If so, it doesn't seem to be problem with the Lucas system.

The advantage of the 'reservoir' approach is that the only mod to the throttle bodies would be the fitting of a throttle position sensor to only 1 of the bodies - this has been achieved on other installations. All the other fittings/plumbing would remain as original.

Anyway, just my ramblings.

Thanks again.

Regards,

 

Nick.

 

[Escadrille Ecosse]

2 minutes ago, N. J, Davies said:

EFI systems need a return to the tank that is larger than that required by the Lucas metering unit so that is necessary mod with any EFI system.

Not strictly true. EFI systems need a steady pressure that isn't affected by load. The system needs a bleed from the PRV but that can be at the tank. Caveat being acceptable fuel temperature at the injectors.

6 minutes ago, N. J, Davies said:

Would there be an appreciable pressure drop between the 'reservoir' and the injectors.

Yes.

8 minutes ago, N. J, Davies said:

If so, it doesn't seem to be problem with the Lucas system.

Actually it is but is masked by the system relying on pressure to open the injectors and the generally being pretty crude.

There is a pressure drop and more importantly a pressure/flow lag which will vary significantly (relative to injector opening times) depending on both the speed and load of the engine. This will make tuning very difficult/near impossible using modern tuning systems, ECUs, TPS, MAP, etc.

Basically why 2.5s on ECU systems have better idle, mid-range torque/power and fuel economy compared to PI. Basically everthing is better except perhaps top end power.

[rogerguzzi]

5 hours ago, Escadrille Ecosse said:

Basically why 2.5s on ECU systems have better idle, mid-range torque/power and fuel economy compared to PI. Basically everthing is better except perhaps top end power.

Hello All

                Just wondering why it may be not be as good if not better?

Assuming the same size throttle bodies are used and injectors that can give enough fuel and is set up correctly (as you can mke it a rich as you want at max revs just like the Lucas system) and send a lot of it down the exhaust?

When I follow my mate in his TR6 and he is driving spiritedly I swear Spitty goes better as she is breathing petrol laden air!!!

I except it was the Best the Bean counters would let the Engineers fit at the time?

Roger

[Escadrille Ecosse]

10 minutes ago, rogerguzzi said:

Just wondering why it may be not be as good if not better?

Assuming the same size throttle bodies are used and injectors that can give enough fuel and is set up correctly (as you can mke it a rich as you want at max revs just like the Lucas system) and send a lot of it down the exhaust?

When I follow my mate in his TR6 and he is driving spiritedly I swear Spitty goes better as she is breathing petrol laden air!!!

Think you just answered yourself there Roger

[JohnD]

NJ,

Have a look on Facebook, the "Standard Triumph Experimental Department" page.  There's a pic of a 2.5 saloon with EFI.

John

[Escadrille Ecosse]

12 hours ago, JohnD said:

NJ,

Have a look on Facebook, the "Standard Triumph Experimental Department" page.  There's a pic of a 2.5 saloon with EFI.

John

And the 'ECU' to drive it

Imagine dropping one of those pins...

[JohnD]

I'm reading an account of the development of Concorde by Ted Thomas, BAC's Chief Aerodynamicist at the time.    A feature, that I knew not, was the variable nozzles to accommodate trans-sonic flight.   He mentions that the test equipment, carried on the prototype to monitor how they behaved, just the test kit, weighed a TON!

I think the test box you showed, Colin, demonstrates one of the early ways to programme a computer.  Although there were keyboards before computers, the early ones used paper tape or cards, or else a pin board rather like an old telephone exchange.  See: https://www.bricsys.com/blog/computer-programing-a-brief-history   

 

John

[JohnD]

Nick,

Not an answer to your original Q, but I see that Jenvey make a full throttle body kit with built in fuel rail.   If they use a fuel rail, when their avowed intent with this kit was to make it as original as possible..... https://www.jenvey.co.uk/triumph-tr6-dth-kit

But sit down before you read the price!

The fuel rail has surely the benefit of economy of design?  It avoids the use of long feed lines to the injectors from some distant distributor/metering unit.      A common rail provides all the injectors with the same pressure, when inevitably feed lines would have different lengths and so slightly variable pressure, which would require different programming for each injector so that they all squirted the same.   

John

[N. J, Davies]

Thanks for all replies. There definitely seem to be too many variables and unknowns for the reservoir approach to be viable. So back to the fuel rail - i.e. the tried and tested.

Somewhere I read that Bosch EV14 type electronic injectors fit straight into the throttle bodies without the need for any machining. Is this true of wishful thinking?

 

Nick.

[JohnD]

Old thread here, Nick: 

 

[Nick Jones]

The EV6s I used needed fairly minor machining - pics in the thread I referenced earlier.  I did mine in a mill with a special stepped drill that I was able to borrow (did a nice job on the fuel rail too), but know others have managed with ordinary drills.  The EV14s are bit shorter, but that might be a disadvantage as you'll maybe get problems with the electrical connection wanting to be in the manifold casting. I've not actually tried though.

[AndyM]

Presumably the idea is to maintain an original look with the 6 fuel lines supplying the individual injectors?

In theory you could take the gubbins out of the metering unit, seal it appropriately and use it as a pressurised vessel to feed the injectors via the fuel lines. (A bit like radial mains wiring than a ring main) You would still need to mate the distal ends to modern injectors, which would need wiring up as the amount of fuel is determined by the length of time the injectors are open. (Controlled by the ECU). 

As has been said earlier Jenvey make a manifold with throttles built to look very similar to a CR set up.

Again you can modify the originals to take modern efi injectors and throttle position sensors.

Will it look any more original than the above, possibly. However you could leave the metering unit and nylon fuel lines in place, with the fuel to it disconnected and the plastic drive dog removed.  You could possibly repurpose the redundant nylon fuel injector pipes and run the wires to the injectors inside them, hiding their existence to great extent?

[N. J, Davies]

Good idea Andy. Using the Metering Unit as the reservoir would be ideal and make it all look nearer to original, but how available are redundant MUs? Does anyone know what thread is used on the injectors themselves?

 

Regards,

 

Nick.