A/F mixture?
02-17-2013, 12:25 PM
#21
This is a bit off of the subject, but I'd be remiss if it weren't mentioned.
My injectors are resized from stock 28.8lbs, to 36lbs.
Steve @ Frost, who did the mailorder tune, cautioned me that the business who resized the injectors, has been noted for large errors in the resized flow rate. For example, Steve said that it wasn't out of the ordinary for injectors to flow up to 30% more than they are rated.
Because I don't understand the full implications of this, I'll make a guess that the injectors only know that they should be open for a duration dependant upon the ECM being set for just THAT size injector (36lbs). So, if the injectors do indeed flow 30% more, for example, the engine will receive 30% more fuel than necessary.
At this point, would the O2s come into play, to keep A/F according to what had been programmed in the tune?
When the heads are removed for porting, the injectors will be flow-rated at an independant facility.
My injectors are resized from stock 28.8lbs, to 36lbs.
Steve @ Frost, who did the mailorder tune, cautioned me that the business who resized the injectors, has been noted for large errors in the resized flow rate. For example, Steve said that it wasn't out of the ordinary for injectors to flow up to 30% more than they are rated.
Because I don't understand the full implications of this, I'll make a guess that the injectors only know that they should be open for a duration dependant upon the ECM being set for just THAT size injector (36lbs). So, if the injectors do indeed flow 30% more, for example, the engine will receive 30% more fuel than necessary.
At this point, would the O2s come into play, to keep A/F according to what had been programmed in the tune?
When the heads are removed for porting, the injectors will be flow-rated at an independant facility.
02-17-2013, 10:09 PM
#22
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You are correct that if the ECU is programmed to think the injectors are a certain size, they will hold them open to inject enough fuel for that flow rate. If the actual flow does not match the Injector Flow Rate table in the ECU, there will be o2 corrections. However, the o2 sensors can only add or subtract a certain percentage of fuel. I don't know what this limit is on the LS1 PCM, but in other cars I've tuned it's about +or- 25%. If the error is beyond that, then the o2's cannot correct enough to make the engine run properly.
Of course the objective of tuning is to minimize errors and have the corrections as close to 0 as possible, so the only way to know how all this is affecting your tune is to take a datalog.
Of course the objective of tuning is to minimize errors and have the corrections as close to 0 as possible, so the only way to know how all this is affecting your tune is to take a datalog.
02-17-2013, 10:44 PM
#23
Ok, the LTFTs are almost 0 (zero) on one bank, and +1.3 on the other.
Would this be a verification that the injectors are flowing the (almost) exact amounts in proportion to their rating (36lbs), to achieve the programmed A/F ratio?
I read somewhere that a 98 year ECM will allow 30%>33% addtl flow, if necessary. I don't know if the amount is correct.
Would this be a verification that the injectors are flowing the (almost) exact amounts in proportion to their rating (36lbs), to achieve the programmed A/F ratio?
I read somewhere that a 98 year ECM will allow 30%>33% addtl flow, if necessary. I don't know if the amount is correct.
02-18-2013, 07:33 PM
#24
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Assuming your VE table and MAF calibration are also accurate, then yes, that would indicate that your injector flow rate tables are set correctly.
