Singlepoint To Multipoint Injection

[pug_ham 241 3 Cars]

I'm currently tempted by getting a late cat model non sunroof 205 Auto that has the MM G6 ecu / management system fitted & junking all the auto stuff to turn it into a rallye look-a-like L reg or newer GTi model but because this system is only single point injection can I make it multipoint simply by crimping extra plugs into the injection loom?

 

After stripping several jetronic looms & a couple of motronic ones thats all they have, one wire from the ecu for the injectors that just splits into four plug at the engine end.

 

If it really is that simple then it looks like I could be a step closer to making this idea a reality but I need to ask Wayne at Chipwizards if this system is mappable because that is the main concern.i It isn't this idea could stop before its started.

 

Graham.

[welshpug 1,626]

I see your logic Graham! I cant see any reason why not, bar the fact that 4 injectors need rather more power to drive them than one? allbeit a slightly larger one as its doing 100% of the fuelling rather than 25%.

 

would the same pulse through 4 smaller injectors do the same job as one through the single injector? need to look at stats and specs to determine any further

[benje 0]

Welsh pug has a good point there.

 

By putting 4 injectors in parallel you will effectivly be lowering the impedance the ECU see's. For example 3Ohm injectors (low impedance) in parallel will give 0.75Ohms. So at 12V they would draw circa 16 Amps (This is all speculation as I'm not sure how injectors are driven) instead of the 4 Amps required to drive just one. As you can see this is a 4 fold increase in current which may fry the ECU. You could probably knock some sort of driver circuitry up but is it worth the hassle?

 

Ben

[petert 554]

Four 15ohm (high impedance) injectors in parallel is 3.75 ohms. That will be fine if your existing injector is a low impedance (3-5 Ohms).

[benje 0]

Good point there petert, so that solves the problem in my post. What are standard peugeot injectors, high or low impedance by the way?

[snillet 1]

The MM G5/G6 injector is a low impedance 1.6-2ohm (depending on type) which is from the ECU driven in a peak-hold way.

 

I still have the G5 loom in my car running the MS on it with the JAZ inlet manifold.

 

I tried earlier to run the XU5M (BDZ) engine with the JAZ manifold and the JAZ injectors but that did not work properly as it should, since it´s a map based system it´s very sensitive for changes in the manifold volume....

 

And also the peak-hold injection driving is probably not doing a good job with 4 paralelled hi-z injectors.

 

Think the G6 has a stepper motor idle control to which will have to be rerouted somehow, perhaps replaced by an auxillary stepper valve controller since the stock one is in the TBI unit.

[pug_ham 241 3 Cars]

So by splitting from single to multipoint I might induce some injection issues.

 

Would it be a case of changing a resistor in the ecu for a different value or value burnt into the chip?

 

You can get different map sensors easily enough but I''ll check if the one for the G6 ecu is the same as fitted to the MM8P multipoint system.

 

I wouldn't be looking to use the ISC in the system with the GTi plenum.

 

If it's all controlled in the ecu chip, I'd be looking at having the system remapped.

 

I've just had a chat with Wayne at Chipwizards, even though it would be possible & G6 can be rempapped, it would be far easier to start with a multipoint loom rather than try to sort the issues changing one from single to multipoint.

 

Shame really but nothing to major.

 

Graham.