Bigger maps to siamese sequential injection timing

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Bigger maps to siamese sequential injection timing

Postby Vauxi » Tue Jun 13, 2017 8:12 am

Hello.
Is it possible to make like 12x12 injection timing maps instead of 8x8? Code works okay now but 8x8 is not even near enough. I don't have a clue when it comes to coding at this level.
Vauxi
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Re: Bigger maps to siamese sequential injection timing

Postby racingmini_mtl » Tue Jun 13, 2017 9:54 am

That's not going to happen. That would take a huge amount of memory which is simply not available. Also, that's the first time I've heard such an issue. Timing should be relatively linear so it should not require that many cells. Which engine are using it for?

Jean
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Re: Bigger maps to siamese sequential injection timing

Postby Vauxi » Tue Jun 13, 2017 11:39 am

I kinda knew the answer unfortunately :( But had to ask. Vauxhall ohv engine. I have a bit agressive cam in it. Cam and throttlebody makes big differences within cells. It smooths out when engine "gets on" with the cam.
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Re: Bigger maps to siamese sequential injection timing

Postby racingmini_mtl » Tue Jun 13, 2017 1:16 pm

I didn't know that Vauxhall had a siamese port engine (but I don't know anything about Vauxhall).

If you haven't done so, you should try to use most of the table for the transition area and have as few values as possible before and after. The timing will be less critical at lower RPM since the injection window is much longer. Unless you're using the single injection pulse method (which I wouldn't recommend with a big cam).

Jean
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Re: Bigger maps to siamese sequential injection timing

Postby Vauxi » Wed Jun 14, 2017 9:50 am

Image

There you go. One Vauxhall siamese cylinder head fresh from the machine shop. With this setup at low rpm range its more like doesn't matter what you input than less criticall. :D It just steals the mixture to the inner cylinders no matter what you do. :lol: Single pulse is not in use.
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Re: Bigger maps to siamese sequential injection timing

Postby racingmini_mtl » Wed Jun 14, 2017 12:38 pm

Vauxi wrote:[With this setup at low rpm range its more like doesn't matter what you input than less criticall. :D It just steals the mixture to the inner cylinders no matter what you do.

That's strange. That would point to a setup that has a lot of wall wetting contribution. What does your intake manifold look like and what's the position of the injectors? Could you change the aiming of the injectors?

As I said, you should have a large margin for the injection timing at low RPM. But if you have a large wall wetting contribution, you will still have a large AFR difference due to charge stealing even with a perfect timing. Don't forget that you can use dual table or the trim tables to minimize the AFR difference; of course that won't work if the wall wetting contribution is too significant.

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Re: Bigger maps to siamese sequential injection timing

Postby Vauxi » Thu Jun 15, 2017 7:50 am

Image

Injectors are in the middle of the intake runner as intake divider is inside the head and they are pointed straight to the midlle of the channel. Injector spray type is one wide cone. I did a lot of thinking between cone and two spray type injectors and decided to go with one cone type. Wall wetting sounds good theory just because when head is cold. The stealing cylinders switch places. When clt is like less than 25'C, inner cylinders tend to go way lean in certan load points. And like from 40'C situation is back to normal outer being leaner. I grinded manifold channels as smooth as I could after welding. Surface is left rough as intake is cast aluminium. I'm using dual table and trim tables. Trim is here and there the only way to make mixtures more close each other. Another thing is to use ego as I have dual lambdas and dual inputs used in ecu. I guessed that with this setup it is not even possible to achive always same mixture all the way. Not even close. It just would be nice to have :) Atleast mixture differences calms down to the upper rpms and injection adjustments starts to make more sense.
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Re: Bigger maps to siamese sequential injection timing

Postby racingmini_mtl » Thu Jun 15, 2017 9:21 am

I hadn't realised in the first picture that these were the intake ports. You seem to have a good setup and you seem to have a good handle on what is needed to try to make it work.

That doesn't look like the easiest physical configuration to work with and it might be possible to have the injectors closer to the valve and with a slightly different angle. But you already gave a lot of thought to come up with a good solution and I don't know if what I mention would make a significant improvement.

While the increase in the timing table size could make it easier to tune, I think you would also need other changes to the code that would take into consideration the wall wetting factor. And unfortunately, there is no space for the table and even for much more code.

Having said that, I'm glad to see a different setup being used and I hope you find a way to make it work a bit better even with the current code constraints.

Jean
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Re: Bigger maps to siamese sequential injection timing

Postby Vauxi » Thu Jun 15, 2017 11:15 am

Yeah.
There are not many us who squirt this Vauxhall engine at this level. I know few others who had tried basics and leaved them there.. I did consider to install injectors few centimeters closer to valves but I was afraid that fuel spray amount then isn't going to be even for both inlet valves. As you likely know injector spray, cone or not doesn't get wide straght away from the tip. Moving injectors few cm more away from valves does increase wall wetting a lot. What is significant factor too is camshaft. As it is big cam with 103 lobe angle. It does pump air backwards at low rpm what makes tuning notably more difficult. =)

Yes. I'll try tune it to perfect as it reasonably makes sense. :lol:
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