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Old 04-22-2009, 10:06 AM   #1
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Default 4 vs 2 injections per cycle

To people with 550 cc injectors, do you guys run 2 or 4 injections per engine cycle?

When I was NA with 230 cc injectors, I was running 4 injections/cycle and it was working great. Since I went turbo with 550s, I am only able to run 2 injections/cycle, I just can't figure out a map with 4 injections/cycle.

It just looks to me that 4 injections is the most efficient way but I tried several values and the car doesn't even Idle. I'm using high Impedance injectors.

Can someone running 4 injections with 550 post a screen shot of their fuel map? Req fuel for 550s is calculated to be 2.8.

Thanks
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Old 04-22-2009, 10:28 AM   #2
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2.8? explain that. that means you had a required fuel of 6.7 previously?
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Old 04-22-2009, 10:33 AM   #3
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550s on my 1.8
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Old 04-22-2009, 11:23 AM   #4
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I am running 550's in a 1.6. My Required Fuel is set to 4.7. That is what Scott put in my base map when he built my MS.
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Old 04-22-2009, 12:07 PM   #5
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^^ Mine is exactly like pauls. Req fuel is 5.6 with 2 Injections per engine cycle. But if I want to have 4 injections per engine cycle, the Reqfuel (greyed out value) becomes 0.5 of that, hence 2.8. Then, if you simply scale the map 2, it doesn't work anymore and the engine is hunting. I tried lowering the values but it keeps on chocking.

When I was NA, I had a reqFuel of 14 and 7 in the greyed box with 4 injections per engine cycle.

So, is anyone with 550 running 4 injections per engine cycle? What's the reqfuel you are using and what's approx the value at idle in your fuel table?
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Old 04-22-2009, 12:12 PM   #6
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I'm willing to bet there are zero (0) members that use 4 injections per cycle.
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Old 04-22-2009, 12:24 PM   #7
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And you guys don't have any issues at idle? I'm annoyed with all the popping in the exhaust and crappy idle, AFR are set to 14.2 but it's still jumping all over unless I use something low as 13 AFR.

The problem might be in the high imp injectors, too slow to open. I'll have to find a set of low imp and try that. But I've noticed that with 4 injections/cycle, the engine requires less fuel since by reducing reqfuel and doubling the values in the tables, it became pig rich.
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Old 04-22-2009, 12:27 PM   #8
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BTW, I'm using MS2 extra so the code is highres.
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Old 04-22-2009, 12:28 PM   #9
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I'm going to go with the problem is your tune.

Start by disabling barometric corrections and adding a .1uF capacitor on JS8 and GRND.
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Old 04-22-2009, 12:43 PM   #10
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My tune is ok, variable ignition timing depending on load (moves between 10 and 13 deg) to compensate for load and values in the table are similar in the idle portion, to avoid any sharp slopes. Increasing makes it richer and smooth idle, decreasing makes it leaner and more popping.

I think I have a cap on the tach input (I'll have to check), my tach signal is clean so I don't think that would solve anything, but l'll doubl check that.
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Old 04-23-2009, 03:03 AM   #11
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If you're having idle problems, then running 4 squirts per cycle vs. 2 is only going to make it worse. You're just degrading the ratio of "normal" injection duration to lag.

550s aren't that big, especially for an MS2. If you're having problems with 'em, then you've got tuning issues. Set them for 2 squirts, and then get your VE table and ASE/warmup enrichments worked out.
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