Double Stoich -half IFR; Triple Stoich-third IFR?

[reconscout]

I've read a few times that the simple way for large injectors to get past the hard coded 63lb/hr in E38 for example is to double stoich and half the IFR. Then log in lambda to make adjustments to fuel trims etc. From the searches Ive seen this referenced for less than 127lb/hr injectors.
Does this method work for larger injectors? I was playing around with the injector dynamic spreadsheet for ID 1300cc/3 bar injectors and had to scale to 33% to get under the 63lb/hr limit.

Question is, if I had to go with 1/3 for IFR, could I multiply Stoich by 3 and have similar results as the double/half method?

[mowton]

Stoich AFR can't be increased beyond 30.....hardcoded limit in PCM.

Ed M

[GHuggins]

Keep in mind that your IFR doesn't need to go beyond the 480kpa cell and not all, but some OS's you can use the injector V multiplier to halve them again... This isn't allowed on all OS's, so check before your purchase...

[mowton]

Keep in mind that your IFR doesn't need to go beyond the 480kpa cell and not all, but some OS's you can use the injector V multiplier to halve them again... This isn't allowed on all OS's, so check before your purchase...

But if you decrease the IFR without a corresponding AFR increase you will throw off the AFR model and have to essentially "scale" all the Air based tables/cells (including tables using air as an axis) as well as the torque. parameters.....

Ed M

[GHuggins]

Not the air model or anything else - just the torque model... That's if the OS even supports it...

[reconscout]

Ed- Good looking out. I went back in to the editor and sure enough it shows the limit on the explanation. Missed that before, thanks. Looks like might be leaning towards scaling most/all the tables that are air referenced?

GHuggins- I ran across a few threads about people running out of injector when swapping to e85. I found plenty of 850cc, and 1000cc for sale used so it made me think that I should be buy the larger 1300s. I was sent 127lb 4 bar, and contacted the company and they sent out a set of 1300cc 3 bar. The broker contacted me and said not to go with the 1300cc because they are harder to tune. Im sitting here next to both sets, so its a little late not to purchase, however I have some flexibility since neither have been used.
The OS is from an E38 early 2009 Pontiac G8. It does have the table for injector volt multiplier set at 1 across the table. Not sure if this OS actually will work with that table being modified. Read a few places for other vehicles that modifying that table didnt have any results. I wonder if anyone with a G8 has tried?

So several potential courses of action here:
Send back the 1300cc/3 bar, and use the half/double method with the 127lb/4bar.
Use 1300cc/3bar, use half/double method and volt multiplier set to .779 (spreadsheet 50% value at 480kpa = 80.798... 63/80.798=.79)
Use 1300cc/3bar and scale everything mentioned on a write up from DStek on the Injector dynamic website

Any suggestions?

[mowton]

Not the air model or anything else - just the torque model... That's if the OS even supports it...

Greg, how can you arbitrarily lower the ifr without a corresponding air mass change and keep the air to fuel ratio correct? What am I missing?

Ed M

[GHuggins]

You still have to scale spark tables to a degree, but if you're at the point of requiring this then your probably doing it already anyway.

[jsbaugh]

You are not scaling the injectors correctly for 1300cc

[mowton]

You are not scaling the injectors correctly for 1300cc

They need to incorporate a .40 scale factor (63.5/161.595) to fit within the 63.5 limit at 480 kPa. The only way to make that happen in that OS is to perform the "Full Scaling approach"....Using the "Double/Half approach" and adhering to the 30 AFR limit, you can get to .47 factor (14.2/30) which is close but still like 15% away.....then you would have to make those adjustments to the other tables like spark, MAF, VE, torque etc. anyways....

Ed M

[veee8]

DSX tuning has replacement plug and play E38 ECM's for the earlier cars that have the 63# injector limit. He uses the later 2010+ E38 with the 127# limit.

[GHuggins]

^^^^ Yes, that would make things much easier for you...

[mowton]

$350 includes licensing.....does make it easier though....

Ed M

[reconscout]

Thanks for setting me straight and giving me another option. I had to be realistic about my own limited tuning experience/capability and choose to use the 127s.