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Any tricks for leaning out with big injectors?


rags

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I swapped out the 50lb injectors for a set of 72lbr's to fix the lean out condition at 20 lb of boost and +6k rpm. This worked well and I can now hold 11.8-1 all the way to 7k. My problem is I can't get the AFR's any leaner than 12.6/8-1 at idle. My Min Injector on time is already set very small at 1ms and since I'm pulling 45 or so Kpa at idle the injector offset won't do anything (Already below Min Inj On time). I've turned down the fuel pressure to 38lbs at idle. It still idles pretty well like this but I'd like to know if there are any tricks to get it to idle any leaner at idle.

 

Joe

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Ron,

 

Yes I did have it set with the vacuum line connected. :redface: Once I removed the vacuum line and reset it to 38 all is now well. I was even able to increase the Minimum Injector On Time slightly and I can still get it down to 13.5/6-1 at idle which is fine. Thanks!

 

Joe

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Another trick is to retard your initial timing number. This slows your idle speed so you can set your idle screw for a bigger throttle opening. This will enable leaning out the idle mixture.

 

I can idle my L at stoic with 75 lb injectors using this technique.

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Another trick is to retard your initial timing number. This slows your idle speed so you can set your idle screw for a bigger throttle opening. This will enable leaning out the idle mixture.

 

I can idle my L at stoic with 75 lb injectors using this technique.

 

 

Thanks Rick. Makes perfect sense. I'll try that tonight. What are you using for initial timing? Do you get any hunting with the lower initial setting at stoic?

 

Joel, I have an idea for what's causing the fireballs :shock: but I'll let one of the "Big Dogs" answer first. :) I don't think it has to do with Min Injector on time.

 

Joe

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Thanks Rick. Makes perfect sense. I'll try that tonight. What are you using for initial timing? Do you get any hunting with the lower initial setting at stoic?

 

Joel, I have an idea for what's causing the fireballs :shock: but I'll let one of the "Big Dogs" answer first. :) I don't think it has to do with Min Injector on time.

 

Joe

Joe...

The method that Rick suggested is what I was going to suggest, too. Try running around 10 degrees or so at idle, then just ramp back it in once you are off idle. It is a good idea to "isolate" the idle timing by a cell on each side, just to keep the timing from moving around at idle. Another thing you might try is setting the bottom breakpoints above idle and just using the initial timing setting. I'm pretty sure the interpolation doesn't start until you are on the map.

 

The popping on decel is usual due to some sort of rich-to-lean transition. Usually you are a bit rich on WOT and you end up putting unburned fuel into the exhaust. The fact that you were rich says that there was no oxygen left for that fuel to burn. Then when you drop throttle, the mixture goes lean, which basically introduces a bunch of hot oxygen into the exhaust and that ignites the fuel that was sitting there.

 

So, this can happen for several reasons. If your Min injector on-time is too low, then it's possible that the system is commanding a PW that's just too small for the injector to open. The decel fuel cut will also do this, if you have it enabled. It's also possible that the fuel map could just be set too lean at those points.

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  • 1 month later...
Another trick is to retard your initial timing number. This slows your idle speed so you can set your idle screw for a bigger throttle opening. This will enable leaning out the idle mixture.

 

I can idle my L at stoic with 75 lb injectors using this technique.

 

Rick, What type (brand and p/n if you have it) injectors are you running? Also, what pulse width do you have to use to get a stoic idle? Thanks!

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It is a good idea to "isolate" the idle timing by a cell on each side, just to keep the timing from moving around at idle. Another thing you might try is setting the bottom breakpoints above idle and just using the initial timing setting.

 

How did I miss this post??

 

I'm going to give this a shot. My idle is fairly stable after dropping the initial timing and opening the throttle plate a bit but will still hunt every once in a while. Thanks!

 

Joe

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Rick, What type (brand and p/n if you have it) injectors are you running? Also, what pulse width do you have to use to get a stoic idle? Thanks!

 

I'm using Delphi injectors from Racetronix. $59.00 each and they flow match the the set when you order. My idle pulse width is very close to the minimum controllable - about 1.3-4 Msec. If you go too low on this ( below what the injector can support) your idle will be unstable.

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I'm using Delphi injectors from Racetronix. $59.00 each and they flow match the the set when you order. My idle pulse width is very close to the minimum controllable - about 1.3-4 Msec. If you go too low on this ( below what the injector can support) your idle will be unstable.

 

Thanks Rick.

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