Rod's build thread - new title - TSCi
Turbo Mini Forums

Paul,

I obviously need to go away and do the maths properly - and thanks for forcing me to do so... - but when I had an oscilliscope on my Weber/Marelli box a few years ago (an unrelated ignition fault), the injectors seemed sequential and nowhere near 80%duty as they never overlapped. I only had a two beam scope but did a fair bit of the testing on the road (ie, at high engine loads) and never saw an overlap between the two injectors I was watching.

Maybe the Weber/Marelli is only semi-sequential and I just happened to have picked the "even" pair when I connected up the scope ???

Back to the drawing board to make sure, but I'm so far behind you I can easily add another two bosses to my "manifold" as I build it.

However, that brings in other questions about whether we need four injector drivers for the code as Jean intends it - I'm not sure I like the MS mod to give four drivers as it seems to lose the 4 pole stepper motor ICV drive....

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

As mentioned, the problem is duty cycle. However, the available duty cycle is about 40-50%. Don't forget you need to inject on an open valve which lasts for about 25% of the cycle but you feed 2 cylinders hence the 40-50%.

Basically, the rule of thumb for sizing the injectors is to multiply by 4 what you would use in a normal 4-cylinder port injected engine: a factor of 2 due to having only 2 injectors and another factor of 2 for the duty cycle.

So to get 140HP, you need about 860cc/min. And it will be quite a job to get a decent idle from those which is why staged injectors are needed if you want to use your car on the street. And if you get staged injectors then the best thing to do is to go from a small injector and a big one so you have very good low load behaviour and you still make all the needed power at the top end.

As for the mods needed for the four injector drivers, you don't lose the IAC stepper motor. What you lose is the ability to use PWM to control the low-impedance injector's peak and hold phases. So you need an external driver that doesn't use PWM which is what my board does. The standard MS injector drivers already use 4 CPU pins. I just change how these are used. And there is a need to bypass a chip on the MS2 card which combines signal from the 4 pins (NAND gate). I'll have more details on the mods in the coming days and I'll take pictures.

Jean

http://www.jbperf.com/

Aaarrrggghhh......

Just when I thought I understood it.....

So I assume from this that on a basic 4 cylinder sequential injection system, the injectors are open longer than the valves (ie, greater tha 25% of the cycle)...

So halve it for one injector feeding two valves only when they are open and halve it again for two runners only.

So this makes the siamese code a true sequential system where only an OPEN valve is injected to...

So, Paul, how have you been running your trials on the Extra code, and first version of the siamese code, with only two injector drivers ???

PS, all this techy stuff would probably be best in the FI part of the forum, should we start a new topic there ???

Rod.

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

I've been running the injectors in pairs, timed to coincide with the outer inlet valve opening. The other port fires at the same time and the fuel sits in the port for 180 degrees before going into the inner cylinder.

That's the only way to do it without the phase/cam sensor.

I also think that this is the reason that I'm getting poor AFR distribution. I think that the fuel injected in advance of the inlet valve opening is part vapourised before going into the cylinder. I do not think that it is purely due to VE issues.

We need to purely inject against an open valve in my opinion. With two injector drivers, this can be done by timing the injector pulse to coincide with the overlap of the two inlet valves in the port.

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."

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

Sequential injection on a non-siamese port engine has only an effect at low-RPM/load because at higher load/RPM, the injection will happen partly with an open intake valve and party with it closed which is no better than batch injection.

What true sequential injection also usually brings is the ability to trim each cylinder which will have an effect at all rpm/loads and is the true benefit of sequential injection in a "normal" engine. With the siamese-port engine, the sequential part is essential and we are finding out that the trim part is also needed.

As for the reason for poor AFR distribution, I think it's a mix of different VE (due to the dynamic interaction of the 2 cylinders), different vaporisation characteristics, and different contribution from wall wetting. There are probably other factors but I assume that all these can be compensated for once a true sequential code is there with trim capabilities and individual injector drivers.

Jean

http://www.jbperf.com/

http://www.jbperf.com/

OK Jean,

That makes sense now... (I think).

So for what we need for different pulse widths is the phase sensor (both Paul and I now have one), but for the full range of output for a decent road car (ie, low RPM metering) is staged injection as well, so, unless I'm totally lost, four injector drivers will ultimately be required ???

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

You will only need staged if your injectors cannot give a reasonable idle with all four in use.

I have had all four of my 480cc/min injectors running at idle without a problem, certainly no discernable difference with just two.

I'm going to need to stage in some whopping big injectors in the 1293 Turbo.

If we inject at the inlet valve overlap, we can accomplish the trim with the timing of the pulse rather than just pulse width.

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."

OK,

To save clogging up the "show us yours" part of the site over the latest developments with the siamese code and Megasquirt, if neither Jean or Paul have any objections, I'll start a thread in the "A Series injection" part of the forum (some interested people may only look there, not here) ....

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

Ok with me.

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."

:S

OK Back to the original topic.

The attached is the design of manifold that I'm going to fabricate for the Miglia. We have the benefit of the big air box so have plenty of space. Also, my turbo manifold is lower at the inlet branches than the standard Metro item.

You may be able to move the plenum up and closer to the head.

Attachments:

13.77kb

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."

Thanks Paul,

I went and played with my Blue Peter cardboard mockup again last evening.

My problem is still clearance in two places, one the turbo compressor outlet (even reversed) stops me going further backwards without going up, and I can't go up because the air inlet to my "plenum" and the throttle body hit the bonnet (or flip front).

I also don't want to go up anyway, I would prefer to be lower, as the angle of the runners (plenum to head face) is already too steep because of the metro manifold so the best angle I can get on the injectors has them pointing at the floor of the inlet tract, not the valves.

Now that I'm having to fit 4, I can only get them in side by side (at an angle rotationally) so they will also be pointing to alternate sides of the ports - even more unknowns to throw into the flow logic !!!

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

You can then see how I ended up like this:

http://www.turbominis.co.uk/forums/index.p...id=129557&fr=25

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."

Yes, I remember that thread - part of the inspiration to get on with mine.

But I made a concious decision to use the standard T3 and standard exhaust manifold and that's where my problems lie at the moment, my compressor outlet is a lot higher than yours.

I did consider the "S" bend approach (I could turm my plenum design upside down and achieve it) but it would put my injectors very close to the exhaust manifold and turbine body (T3s are not small).

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

I've started building up the "plenum" and fuel injection runners, not really much to show yet but I am depriving the world of aluminium...



Although not all the parts are in the piccy, I'm doing two at once, one for the N/A test mule and one for the final turbo.

What you see will become this....



except the fuel injectors will be re-positioned as I now will be going with four......

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

nice!

somthing i can appreciate :)

That is going to look amazing. I can't wait to see some progree on it.

Joe, I did think of your thread when I saw this :)

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

lol

Rod is actually an engineer though!

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

I'm watching with interest. My next one will probably be aluminium if I can get some decent practice welds done.

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."

I however don't have a peice of paper! I just have a go....

I've probably said it before but... I actually found ally slightly easier to weld once you get a few simple tricks down. the main difference is you cant get a small fillet of weld with ally like you can with stainless due to the different heat transfer.

i found there wasnt too much between the two for distortion either,

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

A solution would be to open up the area around the studs and then machine the manifold for the standard location rings.

I guess that this is why BL always machined the recess in the inlet ports.

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."