Danger associated with setting injector scaling too low?
 

Is there any danger in this? Or does will this just cause a little more difficulty tuning? I have 440cc injectors scaled at 390. Everyone says I should raise it but I cant hit my target afrs as it is. I am only running 10psi on a evo 8 16g My maf scaling and fuel map are both maxed in the problem area and I have a walbro 255 and IDC are only about 60% in this area. Dunno what the deal is I want to just drop my scaling to like 350 and adjust maf scaling to get trims back in check but keep getting told this is not a good idea but no one gives me specific problems that would be associated with this.

Your injectors will NEVER be scaled to their flow rating. Search for tips on injector scaling. I would be more helpful, but I'm on my phone and internet is being slow.

Thanks for the input. From what I understand its usually around 10% less than rated flow. I said heck with it and dropped it to 348. Did some adjusting to get the trims back and might be getting somewhere.

If your MAF compensation and fuel map are maxed rich, then that is definitely more dangerous than lowering your injector scaling.

Normally the scaling is ~70% of rated flow (not 90% as you suggested, though this seems to be the case for some FIC injectors).

There should be no danger in adjust a factor (injector size scaling) in an equation based system. There are innaccuracies, and some assumptions made in the ECU will not apply correctly to a car with modified parts.

You should tune MAF compensation tuned for a completely stock setup with only the MAF changed (which may be difficult since it seems you are pioneering a bit), then use injector latencies to get LTFTs in check.

Edit: See below.

Fostytou, I'm kinda puzzled by your recommendations for injector scaling. If going by what you are saying, that would make my PTE 680s scale smaller than the factory injectors. Now, I can see the 70% scaling if I was running E85, but on gas, not so much.

03lances, I see that you're adjusting the scaling and the maf/fuel maps, but have you adjusted the latency values? If you scale the injectors out, but don't adjust latency, you end with fueling issues. I know that when I switched over to the V7 rom, I forgot to adjust the latency values and I had some lean spots b/c of it.

Not sure where my head was at. 10-15% smaller is typical (stock difference is 8.4% between scaling / real).

Ok, I've been pondering this for the last couple of hours. 03lances, now I know I've already suggested that you change the latency values if you haven't done so yet, but I have a one question to ask you. Why are you using the maf to tune for a fuel issue? Honestly speaking, you should have tuned your MAF with the factory injectors still in the car. From my experience, you only tune the MAF to compensate for increased airflow not increased fuel. If you can put your factory injectors back in the car and drive it around normally(no power pulls) for a few hours, you should have enough data to adjust your MAF to fix the trims with regards to the intake/turbo setup. Once the MAF is tuned for the increased airflow, you don't want to touch it again. I say that b/c it will one less variable when trying to tune the injectors.

Thank you streetevo you are absolutely correct. As a matter of fact I have been suggesting to everyone asking me for help to do just that wait to install the injectors until after your tur o and have the maf tuned correctly. I have adjusted latencys, the maf scaling is for minor tweaks now. I was unaware of this type of tuning issue when I did my install and have debated several times about installing my stockers back in I guess I have just been hoping I can get it to fall into place. But idk. Its a lot better now but still A work in progress. I am in my phone right now so please excuse the horrible typing ill fix it later lol. I will be. Little more specific when I get home to my computer thanks everyone for the input so far. :)

l=StreetEvo;8225052]Ok, I've been pondering this for the last couple of hours. 03lances, now I know I've already suggested that you change the latency values if you haven't done so yet, but I have a one question to ask you. Why are you using the maf to tune for a fuel issue? Honestly speaking, you should have tuned your MAF with the factory injectors still in the car. From my experience, you only tune the MAF to compensate for increased airflow not increased fuel. If you can put your factory injectors back in the car and drive it around normally(no power pulls) for a few hours, you should have enough data to adjust your MAF to fix the trims with regards to the intake/turbo setup. Once the MAF is tuned for the increased airflow, you don't want to touch it again. I say that b/c it will one less variable when trying to tune the injectors.[/QUOTE]

Do you know what your latencies are at currently?


edit:What year did your wrx injectors come out of? That'll help answer some future questions.

They came from an 03-05 not sure exact year. I believe at 14v its at .8ms but will confirm when I get home. I have not only the stock latencys but several full wrx roms looking at how they are setup.

0.792 at 14.06v and .960 at 11.72v, my trims are within the +/-5% range, scaled at 348. I bought my injectors used off nasioc and never got them flow tested, lesson learned lol. Also looked back on my purchase and looks like they were from an 02 EJ205 WRX. My stockers are 240cc and scaled to 232 in the rom.

Are they the light blue ones? Your scaling seems awfully low for a set of 440s. When you say you can't hit your target AFRs, how far are they off? Also, what wideband are you using since it's no listed in your sig?

Aem Uego, yes light blue, and yes everyone tells me the same thing. If I had no wideband I would not even know I was leaning I cant feel any fuel cut or anything. If I set the 440s to around 396-410 and get my trims in check then even with my fuel map bottomed out and maf scaling maxed out in the trouble area I hit 13afr at WOT, my target for this area is 11.5

Care to post a rom? I'm curious to see what the fuel table and maf scaling for you look like. You say maf scaling but it sounds like you really mean maf compensation rather than the value of the maf's size or the scaling of the hz to load table.

I could take a wild ass guess that the readings on the car say the load is lower than it should be making the fuel problem in your trouble area happen. The computer determines load by the size of the maf and the airflow readings it shows so a log of airflow hz would easily prove or disprove that theory.

Went through the insanity of that turbo thread of yours seems like you covered all the major bases in fuel pressure so i'll leave those alone.

Good call RoadSpike. Rom and logs would be helpful.