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Am I right in thinking that since I'm using wasted spark, my injection timing should be around 135deg to 225deg ?...

I recall teading somewhere on the megasquirt manual that for the ms3x, the datum of the injection timing is from the time which spark occurs. Now you guys which run individual coils, the angle of injection timing should be something around 495deg to 585deg.... but that is because each of your plugs fire in its respective stroke....

Since all of my plugs fire simultaneously at each stroke, I think my injection angle sould be around 135deg.

Am I right in this hyothesis ? I will check it out once my second wideband arrives

Hi guys, can anyone confirm if the datum of the injector timing is really at TDC of the power stroke ?

Hi guys, can anyone confirm if the datum of the injector timing is really at TDC of the power stroke ?

Hi guys, can anyone confirm if the datum of the injector timing is really at TDC of the power stroke ?

I've been out of the country so late reply.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Hey Paul :) welcome back mate... I've been doing some road testing lately and it's going along quite well. I still haven't got an exact balance between the AFR's but getting there. The car has good response, though running a little rich. I had to deduct around 10deg from your injection timing table. Could it be because of an offset between my cam sensor and yours maybe ?

It would not be the cam sensor.

More likely that we are running an uprated camshaft and a modified head.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Oh I see, but anyways I think it was a good achievement from last week.

With regards to the strategy of connecting two injector outputs to the same injector, what have you guys concluded ? I tried to read about it but never found a conclusion on it.

At higher loads, the injector drivers' outputs may overlap. During the overlap, the ECU will think it's injecting 2 injectors worth of fuel when of course only half that amount is really being injected. Things will go wrong.

By overlap you mean that the injector has to shut off and open up so rapidly in the two consecutive runs that the opening time would be less than the injector dead time ?

Assuming 4 inj drivers, once each driver goes over 25% duty cycle, there will be some period of overlap, where 2 or more inj are on at the same time.

The injections are sequential, but that doesn't mean that they cannot also be concurrent.

So then having two injectors per port would solve this problem ?

I too am out of the country so away from my notes so answers are from memory.

As Paul says, not the cam sensor. It just has to be close to the 120BTDC position, then all the actual timing is done from the 36-1 wheel.

You do not need two injectors per runner for what you perceive the problem to be.

You only need two if (a) you want to double up small ones instead of using single big ones, (b) you want staged injection for either massive power or small ones for low load to get a better idle. (there are a few other reasons as well but those are the common ones).

Back to basics, there are two ways of dealing with port injection on the 5 port.
Either send two individual pulses of fuel per runner at different injection timings so each pulse goes through its own open valve or send a single pulse at a time covering both inlet valves being open, the single pulse being timed so that the right amount of fuel goes into each cylinder.

What you are essentially trying to do is the same as Paul (I think) which is the single pulse covering both cylinders.

If you are running an MS3/MS3X this just requires two channels and you set the timing for the single pulse so it hits both open valves.
If you want two pulses with different injection timings, on an MS3X setup you have to use four channels and double them up - literately by connecting the outputs together - to drive each of two injectors but each one will be driven twice at different times.
This sounds crude but, so far as we can see from the wiring diagrams, is exactly what Rover did with the MPI MEMS ECU which was a four channel ECU from the rest of their range.

Do not get confused by some of the searches you may have done on this subject because a lot of those searches will have related to the MS2 - it has special code (usually known as the siamese code) which allows single or double pulses (or any combination of the two modes) but with only two output channels, no need to double things up.

That feature has never been replicated in the MS3 code hence you have to double up outputs if you want individually timed pulses so probably best to stick with the single pulse for the moment and get familiar with that mode.

Schrödinger's cat - so which one am I ???

Yes I am experimenting with the single pulse per injection at the moment but I just got curious on the two pulse mode.

With the single long pulse I'm struggling a little bit to get the inner cylinders leaner. With Paul's injection timing map, the outer cylinders are almost at the 14 AFR mark, however the inners are constantly kept at an AFR of 7.

Up till now I have tried adjusting the injection timing from Paul's map, however from a theoretical point of view, I guess all I should be doing is reducing the DOI provided that the outers are almost at a reasonable AFR. Am I right in this thinking ?

Firstly are you absolutely sure about the AFR 7 reading ?
Most wideband controllers don't read that low (usual ranges are 8-18, 9-19 or 10-20 depending on make)
Secondly it is highly unlikely the cylinders would actually fire if that rich, and if they misfire when excessively rich, widebands usually (wrongly) read lean.

If the inners genuinely are that rich, either your (injection) timing is way too early or another possibility is you are 360 degrees out (injectors on the opposite channel they should be). That would cause all the fuel to sit behind two closed inlet valves then the inner opens first and takes its fuel and sucks a lot of what is sitting behind the outer valve back round the corner to the inner.
It's unlikely it would run at all like that but just swap the injector plugs as a quick test to see what difference it makes (better or worse).

Schrödinger's cat - so which one am I ???

I've tried that. It runs much worse. Furthermore to be honest I feel that the engine is running quite good. Only occasional misfire but on the other side it's got power and I drove it round the block a couple of times. It accelerates really well also. Could it be that the wideband is giving false readings though ? I must say that the burn marks on the spark plugs do show that the engine is running rich, however there is no distinction between the inner plugs and the other ones.

Hi guys, its been a while since I've posted. Since then I have managed to get hold of the port injection on my NA 998cc. I drove ot daily from my house to university and back every day for one whole month. It is now fully dismantled however since I'm replacing the clutch and repairing some rust on the body.

At the time I am thinking of supercharging or turbocharging it. I'm looking mainly for low boost but over a wide range of RPM's. What is your idea on the matter ?

Also with regards to simplicity of setup, what is the most easy to fit ? I'm talking about manifolds, setting up my ms3x, etc

Hi guys, as maybe you know the 998cc was fitted with a turbocharger this summer. Its a GT1549 running with the MS3x, as guided in this thread.

I've been using the car as a daily now for almost four months. I use it mainly to go to uni and back (1hr drive maximum) in rush hour traffic.

One thing I have always wished to implement is the closed loop control over the fuel. However I'm not sure if it is possible when running one injection per two cylinders as done with the Ms3x, maybe you guys can point me in the right direction. The main concern why I wish to implement this is that, I have a small region around 1500RPM, 70% load, where the cylinders are not well balanced, and no matter how much I try to tweek the injection timing and fuelling, I still cannot achieve a balance. Apart from that region I can safely say that the inners and outers are almost well balanced, obviously with the limitations of road tuning. The car has never been on a dyno since student budgets don't allow that :p

I appreciate if someone can help regarding the matter.

Thanks in Advance,
Carl

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Hi Paul,

Yes I was referring to 1500RPM, wide open throttle (or really around 80-90kPa). Why is this range a problem then ? I know I can use the gearbox :p but sort of its part of the learning for me.


When you say 2 smaller injectors per port, how much cc are you referring to ? Currently I'm still using the original MPi's Injectors.

You're asking for too much at 1500rpm!

Low pulse widths as a percentage of the cycle total, low air velocities, potential for pooling in the manifold....... all issues that could affect it.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Hmmm ... Thanks a lot Paul :)

Adding to Paul's point above about small pulse widths, how confident are you that you have got;

battery voltage calibration,
battery voltage correction,
and injector dead time settings,
all reasonably accurate ?

These all have quite a large effect at low pulse widths and, whilst you say the issue is at WOT (where the pulsewidth should be greater) getting the above three right to start with is going to make tuning issues out a lot easier.

Schrödinger's cat - so which one am I ???