"Bolt on and go" EFI

[Wheelz]

Probably the easiest route to fuel injection on a Stag is to fit one of the new generation of EFI products which consist of a throttle body with a built in controller or ECU.
Holley sells the Sniper, which in 2 barrel form is the 2300, whereas Fitech sell a similar 2BBL one called the 39001.

These feature self tuning as you drive based on the signal form a Wideband Lambda sensor so there is no need for a rolling road session.

I have the Sniper 2300 fitted to my engine and have been running it for about a year now. I designed and 3D printed the adapter that it needs to bolt on to the Stag manifold.

IMG_20210514_171508.jpg

[mike@thenook]

What are your findings Chris, any useful power or flexibility increases and how about economy (not that is ever in my mind driving mine of course!)

Cheers

[MikeParker]

+1 to that. It would be great to get some real info. Have you done any rolling road tests on the Sniper Chris? Do you get improvements in MPG or drive-ability?
Mike

[Wheelz]

I did this as a project for someone, with the aim to just see if there were any difficulties, and identify the process of fitting it. Now that it's finished I wasn't intending to keep it fitted as I have other things I want to experiment with, but I must admit I am really impressed with it, apart from one thing, which is idling. Occasionally when coming to a halt the engine cuts, and I haven't been able to solve it completely yet (too many other things to attend too!). There was no need for a rolling road test as the Sniper has got the mixture spot on, which I can see from the display that comes with it. I think I set the aiming points to 14.7:1 at cruising, and 12:1 at full tilt, but will have to check those. Throttle response is perfect, and it feels very powerful, although that is subjective. I will try to do some fuel consumption tests if I get the opportunity, but with the mixture being ideal I expect it to be good.

For anyone who likes tinkering though, there are endless menus where you can set things like warm-up enrichment, using a graphical displays etc. All good fun.

[MikeParker]

Chris,
I was mainly interested to know how much extra power/torque you get by removing the constriction of the Stromberg carbs. I much prefer your idea of putting injectors on the Strombergs. That still seems to me the best of all worlds. I.e. something that looks as standard as possible, no flow limitations from the piston/damper arrangements, plus proper mixture control and no evaporation/float chamber issues. What's not to like!

I am now at the position that I have got the standard Stromberg carb setup going as well as it can. I have rebuilt the carbs, and have set up my electronic engine management over the last 4 years to give the best performance an economy. I am building an accurate MPG meter just so I can get some comparative figures over short scenarios (i.e. short a>b routes, hill climbs etc). On long journeys I am getting around 34 MPG. I really need a rolling road just to check where I am in terms of torque and power. Subjectively the car seems better than it ever has been. As you say, all good fun!
Mike

[Wheelz]

Chris,
I am now at the position that I have got the standard Stromberg carb setup going as well as it can. I have rebuilt the carbs, and have set up my electronic engine management over the last 4 years to give the best performance an economy.
Mike

Engine management Mike? Do you mean your electronic spark control?

[Wheelz]

Chris,
I was mainly interested to know how much extra power/torque you get by removing the constriction of the Stromberg carbs. I much prefer your idea of putting injectors on the Strombergs. That still seems to me the best of all worlds. I.e. something that looks as standard as possible, no flow limitations from the piston/damper arrangements, plus proper mixture control and no evaporation/float chamber issues. What's not to like!
Mike

It is quite a few years now since I ran my car with the Stromberg based throttle bodies, and I seem to remember being very impressed with that too. I would like to refit that and do some more development on it; it was just the idle air valve that I needed to sort out, but as we now approach summer again, I am loathe to do anything that might risk taking my car off the road as I am looking forward to joining in with all the run outs, and meetings that are coming up. Summer is so short we have to make the most of it.

PS: I am going to Prescott again this year, so if anyone wants a ride up the hill...........

[MikeParker]

Engine management Mike? Do you mean your electronic spark control?

Yes, Engine Management might be slightly over-egging it! Specifically it is electronic control of rpm-related and vaccuum spark advance using a trigger signal from a standard distributor with locked off speed advance weights and disconnected vacuum advance. Not only does it allow better control of spark advance against revs, but also vacuum advance that can vary with revs.

[mole42]

Yes, Engine Management might be slightly over-egging it! Specifically it is electronic control of rpm-related and vaccuum spark advance using a trigger signal from a standard distributor with locked off speed advance weights and disconnected vacuum advance. Not only does it allow better control of spark advance against revs, but also vacuum advance that can vary with revs.

That sounds like one I have from an Australian company - mine has a similarly locked distributor and a small micro-processor to control the advance curve, well actually two curves because you can switch between them at will. There's a switch on the vacuum port to provide vacuum advance, but only at one setting. I haven't installed it yet, I made a hall-effect sensor which needs finishing, and then other projects got a bit further up the ladder.

[MikeParker]

That sounds like one I have from an Australian company - mine has a similarly locked distributor and a small micro-processor to control the advance curve, well actually two curves because you can switch between them at will. There's a switch on the vacuum port to provide vacuum advance, but only at one setting. I haven't installed it yet, I made a hall-effect sensor which needs finishing, and then other projects got a bit further up the ladder.

Richard,
I bought the Aldon Amethyst as my first try, but it never seemed to work properly. Always mis-fires and never quite got the timing I was expecting from the tables. I then decided to knock up my own controller using a micro-controller I had used for work projects. I have a standard hall effect unit in the distributor so that if my unit breaks I can do a quick swap over. I have now done over 10K on my own controller and all has worked really well. We go to southern France in the Stag most years and it gives me hours of fun tweaking the code by the pool!

[Wheelz]

Richard,
I bought the Aldon Amethyst as my first try, but it never seemed to work properly. Always mis-fires and never quite got the timing I was expecting from the tables. I then decided to knock up my own controller using a micro-controller I had used for work projects. I have a standard hall effect unit in the distributor so that if my unit breaks I can do a quick swap over. I have now done over 10K on my own controller and all has worked really well. We go to southern France in the Stag most years and it gives me hours of fun tweaking the code by the pool!

The Aldon Amethyst looks great on paper, and I nearly bought one some years ago. But their sales guy did warn me that they had some concern about a misfire on 8 cylinder apps. something to do with cross talk between adjacent HT ignition leads. You would think they would have solved it by now wouldn't you.

Whilst on the subject of ignition, engine management etc, I think spark ignition timing is a commonly neglected area when considering what is to be done, when restoring or repairing a Stag engine. My impression is that there are many Stags on the road which have had lots of money and time lavished on them, but are still running on an old distributor. Fitting a good electronic ignition is a step in the right direction, but what kind of advance curve are we getting from our 50 year old dizzys? Is the timing stable or does it jitter of flap around? Is the curve lacking advance or over advancing, causing loss of power and bad economy?

I have a tester on which I can run up a dizzy, set the speed, and observe the resulting spark. I can also measure the coil current, and using a strobe gun check what is happening with the spark advance as the speed increases. I can do this either with standard points, or any electronic ignition system. In many cases the ignition advance is of very poor quality due to problems with the old mechanical advance mechanism. You might not believe how bad some of them can be, but I have had plenty of examples of this. Sometimes the spark seems to be weak and lack energy too due to inadequate dwell or other problems. On top of this, the cap and rotor arm can cause problems with tracking etc.

Please be warned that even having the distributor reconditioned may not resolve some of the problems, as I have found from experience. New ones are now becoming available, and perhaps this may be a better way, but I have not yet evaluated any of these. On a couple of dizzies I had professionally reconditioned, the timing was so bad I had to send them to the Distributor Doctor to have them tested, which confirmed that they were bad, and they had to be rebuilt at considerable extra cost.

All this leads me to wanting to aim at eliminating the distributor in favour of a more modern ignition system, perhaps using wasted spark coils, crank trigger wheel etc.

[MikeParker]

Yes, I found spark timing jitter is a real problem. All those chains and gears. So much so that I replaced the jackshaft, sprockets, timing chains and tensioners in case that was the problem. It made very little difference. In the end I have used a digital filter so that several spark events are used to calculate the current spark timing.It means that you can advance timing further before the onset of pinking. Also the car feels a lot more solid under load. The graphs below is what I have settled on. Note with vacuum advance (Advance vertical, mm Hg horiz) you have the freedom to vary the advance (in degrees) with RPM. Ultimately, it is not degrees that counts but time. The variable vacuum advance is trying to keep the milli-seconds advance constant over the rev range in the same way as the speed advance:

Speedadvance.jpg
vacuum.jpg
Note: Static timing is 16 Degrees BTDC. So add 16 to figures above. Total advance limited to 44 degrees.

[mole42]

I'm interested in several parts of this idea. My replacement distributor doesn't have any dynamic timing adjustment, the cam and the rotor arm are fixed solidly to the shaft. All the ignition alteration is done in the microprocessor - just now it has a look-up table to enable alterations to be made to the advance curve map but I hope to modify the program later, if necessary, to allow more subtle alterations to the map. The vacuum advance is determined by a single point switch. I'm quite interested in removing the distributor in favour of coil packs and a timing wheel somewhere more solidly related to crank position but I think I'll get this system working first!

Although I've tested the distributor and plotted the curves on a test rig, I don't know yet how it will perform in the car. One thing I have done is to make a special rotor arm with a wider tip because the rotor may not be exactly adjacent to the plug terminal when the ignition is far advanced.

One point about the Jaycar system that I have is that the ignition is controlled by a regular MC3334P ignition controller chip which apparently can deal with spurious noise on the trigger line. That chip can take the input directly from a hall-effect sensor or points but in my case the firing point signal is handled by a PIC16F84A.

[Wheelz]

I'm quite interested in removing the distributor in favour of coil packs and a timing wheel somewhere more solidly related to crank position but I think I'll get this system working first!......

When you are ready I am happy to share info I have so far eg with bespoke trigger wheel and coil packs with mounting bracket. My trigger wheel mounts on the crank pulley to save removing the pulley.

[KOY 23]

When you are ready I am happy to share info I have so far eg with trigger wheel I have designed, and coil packs with mounting bracket. Trigger wheel mounts on the crank pulley.

To save reinventing the wheel, try www.trigger-wheels.com, who specialise in trigger wheels, strangely enough, as well as brackets and other useful parts. No connection just a satisfied customer.