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Andy

Yet another XU9/10 engine build

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petert

There's definitely a table called "Injection Timing". The default value is 316 deg. over all RPM and loads.

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Andy

Found it, in the ‘additional maps ‘ section under injector timing. As you say, the table is set to default 316 degrees as the closing point. The table allows that to be changed to trigger on opening if preferred. I will consult Mr Walker . The logic suggests that I want the injector to begin to fire as the valve opens , which in Emerald speak will be 690 degrees ( ie 30 degrees btdc) . This is getting interesting, and I have not built the engine yet !!!

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Andy
8 hours ago, Biggles said:

No offence intended but I would suggest some more research is called for.  As Petert posted above, the injection window relative to valve opening is significant (which requires cam position to be known).  Having spent many an hour on the dyno being paid by a major OEM to look at such things, take it from me that even at WOT the effects are measureable and at part load the opportunity for getting it badly wrong is significant.

No offence taken. I have a lot to learn . That is what makes all this so interesting ( and often expensive) 

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petert

The injector always needs close at a similar time, ie approx. 420 deg in my examples, which is approx. 60 deg ATDC, approaching the maximum inlet lift point. The injector opening point is what needs to change. It will be interesting to hear what 316 deg. actually is.

 

I notice the K6 has a 3D map. Mine is flat for all loads at an RPM point. Maybe later ECU's are 3D.

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Andy

Right. Just spoken to Dave Walker. Default position for the tang on the cam should be 0 degrees, ie tdc, as the actual timing points as adjustable in the injector timing table. The bit that surprised me was when Dave explained that the injector needs to fire onto the back of a closed valve, the idea being that the heat from the valve helps vaporise the fuel and reduce HC emissions . I had assumed the opposite. Even more to learn than I thought. This is counter intuitive, although I see the vaporising argument

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petert

That sort of suspects what I'd suspected, that the Emerald is incredibly similar to the Autronic SMC. ie the tang has to trigger between cyl. 4 and cyl. 2 firing events. Attached is the default table from the SMC. You can add axis in either direction as required.

Inj Angle End Autronic.PNG

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Andy

Cheers for this. I see what you mean. I think that on the Emerald, 316 degrees is is 44 degrees btdc on the compression stroke ( 0-180 = induction etc ) , so the injector completes its firing cycle on a firmly shut valve . On that basis , at low rpm , it will be firing onto the back of a closed,,or nearly closed valve , if I have understood correctly 

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Biggles
9 hours ago, petert said:

The injector always needs close at a similar time, ie approx. 420 deg in my examples, which is approx. 60 deg ATDC, approaching the maximum inlet lift point. The injector opening point is what needs to change.

And that nicely illustrates the minefield that this is - on one of the engines I worked on (not a Peugeot), at part load having end of injection near inlet max opening was the one place you did not want it as the combustion stability went to absolute s@£& !

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DrSarty

So while I watch this (and learn) with interest, I have 2 key and related points:

 

1) Is this level of effort really worth it for Andy? *Actually, this is the main point*, and;

 

2) How genuinely worth it is it - I mean sequential fuel injection - for several broader communities such as main vehicle manufacturing and motorsport, in terms of emissions, fuel economy and/or performance?

 

I'm not for one second saying it's pointless, but I'm perhaps likening it to cyclists shaving their legs...

 

In other words, could you (Andy) gain more by spending time in other areas such as building a higher revving engine and/or gaining more component reliability?

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petert

I thought it was 44 BTDC on the exhaust stroke. ie inlet valve closed, just about to open.

 

I think it's worth the effort if you have the desire/effort/ability to make the engine as nice as possible over the entire rev range. And I really should shave my legs. I've just never been able to work out where to stop.

Edited by petert

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petert

Try this:

 

"The main concern is that the injector closes before the overlap period of the intake and exhaust valves. Otherwise some of the fuel would be purged right out of the exhaust port. On low loads and rpm's this can be a significant amount of fuel. This leads to different issues, like inconsistent fuelling at low loads and low rpm's, that makes the engine run rough because it will either run lean or rich depending on how much of the fuel got wasted in the overlap.

When the exhaust port is about to close, and the intake port opens, there will be fuel in the intake port waiting to be sucked in with the air.

If the injector is still spraying, that fuel will mostly just follow the air stream into the cylinder and to a high degree go out the still opened exhaust port.

Fuel that is lying around in the intake port, waiting for the intake valve to open, will partly condense, and stick to the surface of the port wall and the valve top. And it will partly be a vaporized fine mist due to the temperature in the intake port. The fuel mist will, and particularly the fuel condensed to the port wall will, to a much lower degree exit the exhaust port in the overlap period, compared to a jet spray of fuel from the injector. This makes for good mileage and good driveability at low loads and low rpm's.

If the fuel is injected very early before the intake valve opens, more of the fuel will be condensated to the port wall. This gives bad driveability and lower power. The fact that the fuel will be heated up by the heat of the intake valve and port wall will rob the engine of power, and the fuel, (at least petrol), will loose some of its octane rating. So one does not want to inject the fuel to early.

The engines rpm does also come into play, since it takes a while for the fuel to reach the intake valve.

Another factor to keep in mind, is that one does not want the injector open time to span over the overlap period. If unlucky, the variations in fuelling can be so much that the engine stumbles on power. So therefore one wants to place the injector end angle so that the injector will not open before the overlap. It is good to keep the overlap outside the injector open time if it is possible. Also, the turbulence created when the inlet valve opens helps fuel preparation. The lower turbulence in the end of the inlet phase is not helping to mix the air/fuel, and the fuel injected at that point will not be mixed with the air as well as the fuel injected prior to, or when the inlet valve starts to open. Unless one has some very fancy injectors.


In shortform: One normally wants the injector end angle to be just a bit before the intake valve opens. Like some 200 to 280 degrees to be on the safe side.

In longform this topic can produce bookstores of theory. When we start talking about effects of turbulence and induction pulsation on fuel vaporization, stratified charge, pre-emulsion, monolith injection, cylinder wetting, etc... " Autronic Forum

 

 

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Andy
12 hours ago, DrSarty said:

So while I watch this (and learn) with interest, I have 2 key and related points:

 

1) Is this level of effort really worth it for Andy? *Actually, this is the main point*, and;

 

2) How genuinely worth it is it - I mean sequential fuel injection - for several broader communities such as main vehicle manufacturing and motorsport, in terms of emissions, fuel economy and/or performance?

 

I'm not for one second saying it's pointless, but I'm perhaps likening it to cyclists shaving their legs...

 

In other words, could you (Andy) gain more by spending time in other areas such as building a higher revving engine and/or gaining more component reliability?

Morning Richard. I take your point, but as the engine I am building will be fully balanced, forged rods and pistons, solid Petert cams, solid lifters, 6mm stem Supertech valves , 85mm liners and 11.0:1 cR , well on my way to a reliable high revving engine .  Because of the above, I think it is worth the effort of optimising the fuel injection , although I accept it is no trivial matter 

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Andy

Peter,

 Thank you for that . A salutary read, in the sense that injector firing angle is a non trivial exercise .

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welshpug

solid tappets but only 11-1??

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petert

DFZ 205 GTi is only 8.4:1 with solids. B)

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Andy
6 hours ago, welshpug said:

solid tappets but only 11-1??

Yes. With the cams I am using, that gives a dynamic compression ratio that is not extreme .

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welshpug
11 hours ago, petert said:

DFZ 205 GTi is only 8.4:1 with solids. B)

touche :lol:

 

seems odd to see such a low compression with solid tappets, I'm in the mid 12's on a hydraulic cam in a 16v xu.

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petert

There's all different ways to skin a cat. At the end of the day however, we didn't want the DCR to be >9:1 so it runs on 98 RON with sensible ignition timing.

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Andy

Manifold back from Zirotec. I am now significantly poorer but hope to have a cool engine bay!!!  Something I mentioned in Dr. Sarty’s turbo thread 

B4719707-9D8C-4535-ABE4-A98BC9A526A2.jpeg

7E91E79B-39EE-4973-8DD4-0F430AC7B8E9.jpeg

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Andy

About 5000 years ago, Peter Taylor sent me an extension plate for my Xu10j4 pump. I finally managed to get the plate tig welded in place yesterday . Next job is to rebuild said pump, so that it can join its friends the gti6 trapdoor Sump, the 1.9gti spacer plate and the gti6 windage tray . Having read through past threads from 2006/7/ 8 over the past couple of months, I had noticed the odd word or two on oil surge in the XU9J4 so I will add no more to the subject .

More to follow when I have had my coffee break !

4A8FCDD0-1406-4B41-9CAC-5A1D17384892.jpeg

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Andy

Coffee over. All the components cleaned with jizer, followed by hot wash ( dishwasher ) , brake and clutch cleaner and an airline. I did a little careful de-burring with a fine carborundum stone and checked the mating faces for flatness . Gear clearance in the housing checked as per photographs , and I also checked the gap between the gears and the end plate. It was less than 2 thou  which is satisfactory The gear to casing clearance was 3 thou on the drive gear and 2 on the driven, so again absolutely fine. 

46BD9176-C3FB-4BFD-A0C3-A3BC08B476FA.jpeg

F0913FB1-BBC5-4519-B14E-4127263EF1E7.jpeg

0F3371B9-3CEC-4B2C-B6A9-00F494389E49.jpeg

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Andy

Next. New 6 bar spring and piston ( from Peugeot) , then a smear of molybdeum disulphide grease ( these pumps will not self prime, so use oil only at your peril he said self importantly ) between the gear teeth and then bolt together .More photos to follow as soon as the site allows me to upload  them.

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Andy

Completed pump ready to be put in a sealed bag until needed. The gear end clearance is from another pump  but shows the idea . 

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DrSarty

It's not a 'spacer', but I'm sure you know that. It's a stiffener for the alloy block.

 

However: it can be used - usually with some mods to or removal of the ribs to accomodate the optional windage tray - to effectively 'space' the sump from the block, therefore upping oil capacity, at the expense perhaps of risking sump to ground impact. This works with or without the extended pick-up and even the windage tray; but why do one without the others?!

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Tom Fenton

Andy just a quick tip for you, I see you like to work on newspaper, keeps things tidy however I find it can be a pain sliding about etc

Top tip, when passing a decorating shop go in and ask for their most lurid horrid wallpaper that no one will buy, it’s usually very cheap or free! And it makes a super bench lining material, my bench tops in certain places are mdf so I fasten it down with a staple gun. Just like newspaper you bin it after use. But it’s much more user friendly and durable to be honest. I always use it when building engines.

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