LPG for single point injection engines

[quat-fro]

Hi there,

I have a Citroen AX with single point fuel injection and I'd like to avoid using one of those highly abhorrent mixer rings.

What are my options?

Would I run four injectors sequentially from the single injector impulse?


Would anyone recommend a particular system to suit such a set up?

Thanks in advance for any help,

Tom.

[Tinleytech]

A slight plug, but we have a new injection system for carburettor, mechanical injection and singlepoint injection engines which we are in the process of launching.
This is the only way we have found of converting this type of engine sucessfully with a multipoint system (there used to be a few older type 'stand alone' injection systems but none are available anymore) and results seem excellent.
Dont like to advertise on a forum but thought this might be of interest to quite a few people running old mixer systems, details will be on our site as soon as it is ready.

Tinley Tech Ltd.

[Gilbertd]

What's the big objection to a mixer? With a lambda controller they work fine.

[rossko]

Many of the horrors associated with mixers stem from using them in conjunction with manifolds and plenums designed to accomodate only fresh air. That isn't the case with a mono-motronic.

I'd have doubts about using an ordinary slave LPG injection system - not at all convinced the PWM mono injector drive frequency is related to RPM and may confuse the heck out of it, for one gotcha.

[quat-fro]

My objection is based on brief experience, none of it terribly good.
Huge backfires and power sapping reduction in throttle body breathing area and seemingly not much option between poor running and terrible MPG.

Admittedly, this may all be down to the person who specced and set up these systems, but it's enough to put me off!

Plus, the "high precision" of the valve in the gas pipe supposedly able to control mixture? I feel I'd be better off sitting on a propane bottle, controlling the mixture by hand with the valve and a length of hose pipe.

Sounds good Tinley.

Rossko - What would you suggest I go for?

[classicswede]

I've converted a number of those mono point injection Citroen engines. They do work perfectly fine on a single point system even in open loop form.

I have also converted some mono and twin point injected engines with multipoint injection systems. The multi point systems take a lot longer to set up.

If you are thinking DIY then mixer is the only way to consider. Pro fit them the multi point is an option but you will pay more for it and only a small number of installers would be willing to do it.

[quat-fro]

This' ll be my third installation. Both previous jobs being fairly complex kits, so I'm not scared of a bit of work, just not fully up to speed on what kits are available for these slightly unusual engines.

[Gilbertd]

You've obviously had bad experience with poorly installed or set up systems. I've had three cars on lambda controlled single points and the difference in performance between petrol and LPG isn't noticeable (even when I've tried taking the mixer out completely). The Saab did over 100,000 miles in my ownership and never backfired once, the LSE did a mere 45,000 but never backfired once and the P38 (which is a bit too complex for a single point anyway so not ideal) has done 90,000 miles and only backfired twice but on both occasions was due to me fiddling rather than any installation or design failure. In comparison, the other P38 with a multipoint on it gives no better performance or economy but does cost more to run because it needs petrol to warm up on. My daughter used it for a month but as she only lives a mile from her office it was changing over to gas as she pulled into the car park so she used virtually no gas but gallons of petrol. In comparison, the single point P38 runs on gas from cold and hasn't had any petrol put it it since March.

If the vaporiser is adjusted correctly on a single point, the amount of adjustment needed from the stepper is tiny, it just fine tunes. If the adjustment on the vaporiser is out, or left as it came out of the box, the stepper will be trying to adjust over it's full range all the time so will run like a dog.

[classicswede]

I would say mixer is the way to go for you. I have done 100's of 1000's of miles on mixer systems and only ever had a couple of backfires including some sets ups that were not ideal in terms of manifold and mixer locations. Even so there are no performance issues but they can need tweaking now and again. You will want the correct plate mixer for the job.