Help with injector timing table

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240sx-venezuela
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Help with injector timing table

Post by 240sx-venezuela »

Hi folks, I was wondering if anybody could help me with this injector timing table, is from an Aem basemap and I want to set it up in tunerstudio (Megasquirt)

Image

Could somebody help me with the corresponding values? AFAIK negative values in tunerstudio correspond to BTDC, but my logic says that the AEM table in injecting in some points when exhaust stroke is ocurring, sorry for this stupid post LOL, but I need to clarify this.

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BigLoukaT
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Re: Help with injector timing table

Post by BigLoukaT »

General consensus is that all fuel should be injected before the intake valve opens.
Unless there's a map missing from your view, aem treats this as a 2d table (rpm vs injection timing) vs megasquirt treating this as a 3d table (map vs rpm vs injector timing).
Generally speaking, as rpm increases, time for fuel to dwell against a hot intake valve should increase too. Your tuner studio table shows the opposite.

It would be hard to correlate the megasquirt value to the aem value without knowing the timing point... ie, is the injector timing staged at end of pulse vs start of pulse. My recommendation is to setup the table at end of pulse, and megasquirt will back up enough to inject accordingly.

And injecting on the exhaust stroke is likely better than injecting during a valve open event FYI
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npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.
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240sx-venezuela
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Re: Help with injector timing table

Post by 240sx-venezuela »

I did this table with the guidance of the AEM table

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I was wrong with the info on megasquirt table, negative values correspond to ATDC and positive values for BTDC
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BigLoukaT
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Re: Help with injector timing table

Post by BigLoukaT »

What is your timing point (start, middle, end of pulse) set to?

I would set to injection timing at end of pulse (meaning injection ends at the crank angle specified in the table), and values starting at 380 degrees (assuming a cam with intake valve opening no more than 20 degrees btdc exhaust stroke) and increasing as rpm increases.

But there's multiple ways to set up the table and start/end pulse to shoot fuel at the closed intake valve most times.
1990 S13
Boosted single slammer
MS DIYPNP
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.
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240sx-venezuela
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Re: Help with injector timing table

Post by 240sx-venezuela »

End of pulse
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BigLoukaT
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Re: Help with injector timing table

Post by BigLoukaT »

Looks reasonable. It makes more sense to me to speak in terms of btdc, so my table would be 720 degrees added across the board (to result in positive numbers throughout the table).

I would probably give a little more time at 600 rpm (-340). And the other rule of thumb I've heard is to add 10deg per 1000 rpm for a swing of approx only 60 degrees across the whole rev range as a starting point. But then again, it will become less and less important as engine speed and pulse width increases.
1990 S13
Boosted single slammer
MS DIYPNP
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.
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