Installed 650s, set AFC, but quick question I can't find the answer for...

[Rice Over Wheat]

Ok, I read all the tuning guides since I'm trying to learn how to do it myself for when my logger gets here. My 650s call for -30.77 baseline. Now, what the tech guides don't explain probably because it's so basic a question...

I'm wondering that at -30.77 does that mean the 650s give zero additional fuel compared to 450s (same FPR), because the equation to calculate baseline is to compensate for the larger injector size flow rate? I know the nozzle gaps are just bigger on the 650s so more fuel sprays out when held open, and I know how the AFC works. But if I set the AFC to correct for the larger flow, how does just tossing in the 650s at baseline settings change my fuel delivery? It should be same as before until I tune, right?

 

[Gromit]

Ok, I read all the tuning guys since I'm trying to learn how to do it myself for when my logger gets here. My 650s call for -30.77 baseline. Now, what the tech guides don't explain probably because it's so basic a question...

I'm wondering that at -30.77 does that mean the 650s give zero additional fuel compared to 450s (same FPR), because the equation to calculate baseline is to compensate for the larger injector size flow rate? I know the nozzle gaps are just bigger on the 650s so more fuel sprays out when held open, and I know how the AFC works. But if I set the AFC to correct for the larger flow, how does just tossing in the 650s at baseline settings change my fuel delivery? It should be same as before until I tune, right?

I think you've already got most of the concept, but I'll repeat some of the stuff from the tuning guide just so it all comes together...

The -30.77 number comes from this equation:

[1 - (stock injector size / new injector size)] * 100 = % more flow

i.e., the 650's flow approx 31% more fuel than the stock 450's. The ECU does not know that you have 650's installed now so it will see x amount of air & hold the injectors open for the corresponding amount of time. That amount of time with 650's will flow more fuel. By putting in the -31% correction to the SAFC, you trick the ECU into thinking there's that much less air so it doesn't hold the injectors open as long & ask for as much fuel. In theory, everything is balanced out as if you were on a stock set-up. The problem arises as you fool the ECU more & more by reducing the airflow numbers it sees. Bigger injectors, larger airflow correction, & now the ECU wants to use a lower map with higher timing, which usually means knock.

Bear in mind that you should not immediately start out tuning at this baseline correction - since every vehicle is different this # may result in your system being too lean. Start out with something like -25% & work your way lean from there based on your logger data.

 

[Rice Over Wheat]

That's where I was going to set the baseline, from 25 to 28%. But based on that logic, I'd be running richer than stock 450s and therefore the 650s would result in less power than before - until I tune leaner than 30.77...am I understanding that right?

 

[CanadianTSi]

No at -31 they are going to flow 650cc's.

You are not essentially turning them into 450's.

 

[tom04841]

Gromit is saying to start on the rich side and tune from there. EVERY car is different, and -31 may be too lean for YOUR vehichle. You need to start rich and TUNE your trims via the datalogger. Start out at @ -25 and take out or add more if needed. Once you have close to 0% lo trim, carry over that number to the 2k rpm setting then you hold the rpms @ 2000 and get your mid trims as close to 0% by adding or subtracting again. Then carry that number over to the 3k setting and hold the rpms at 3000 and add/subtract again til it is close to 0%.

Once you have your lo, mid, and hi trims as close to 0%, carry your 3k setting on the afc all the way up to the 7k setting on the lo and hi throttle settings on the afc.

After this is done, you can start doing some 3rd gear WOT pulls and datalog them. If you have NO knock (smooth, increasing timing curve), subtract some fuel across the board in the hi throttle settings. Keep doing this until you get knock (dips in timing curve), then add in a point or two til you get 0 knock again.

You now have a STREET tune!!!

 

[Rice Over Wheat]

Ok I set it at -25% across HI/LO until I tune. Install went smooth, seems to be running fine. I appreciate the help, thanks.

I can't believe how easy it is to install injectors. To think I was going to pay to have this done.

 

[spectr019]

hahahahaha no kidding, same exact thing I was thinking when I put mine in two days ago. Took a whole 25 minutes...I was sure that I was completely missing a step. And yeah I'm going through the same thing you are basically, except that I'm tuning on a 2G and not a 1G...Oi WTF Good luck though with your tuning.

Ben

 

[Rice Over Wheat]

Actually I am also 2G. We have similar mods. Btw, how did you build that nice cold air box? I'm about to start on that type of project myself...