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Old 03-17-2005, 10:05 PM   #1
scooby24
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Default Scale mod injector size on stock injectors?

Hey I've got a STi with Utec and always had a problem with base maps and such running wayyyy too rich. IDC was maxed out on 16 psi of boost on the base Stage 2 TXS map.

Well I ended up tuning my own map on a wideband and fuel was like -5 percent in most spots and on 18 psi it was hitting around IDC of 88 to 90 except at 6500 and up it was like 95.

Well a buddy of mine's tuner scaled up the mod injector size in the parameters in his because his fueling wasn't right to. Set it to 590.

So I load a map I had with fuel at 2% above stock (would have been rich as hell). Put the mod injector to 590 and boost to 19 psi. Still a little too rich as my IDC was around 95 all over the place.

So I ended up setting it to 620 and now IDC is about 90 all over and when I widebaned my car at about that same boost and IDC of 88, my AFR was 11.4:1 (right where I wanted it)

Wow that was a lot longer than I thought.

CLIFF NOTES::::: Has anyone heard of having to scale up the mod injector size in the parameters on stock injectors? I sold my wideband so I can't get AFR but according to my IDC I'm right where I was before...maybe even a little richer.
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Old 03-18-2005, 07:32 AM   #2
happasaiyan
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so you sold your wideband before tuning your fuel map why?
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Old 03-18-2005, 09:33 AM   #3
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Quote:
Originally Posted by happasaiyan
so you sold your wideband before tuning your fuel map why?
No I tuned my fuel map on another map I was using that was at 11.4:1. Wanted to try out the scaling thing and figured if IDCs were about the same AFR should be too..

And I have a buddy who has a wideband I can borrow this weekend...just was hoping someone else had the answer first.
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Old 03-18-2005, 09:39 AM   #4
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you could figure it out theoretically, but its not cut and dry.

ie- if you know exact airflow (g/s) at the given rpm and IDC, you would know AFR X.
if the other map had the same exact airflow (g/s) at the given rpm with a lower IDC, it would be leaner. but its not exact. so you cant say for sure.
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Old 03-18-2005, 12:40 PM   #5
ride5000
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i'm not getting the point of your question.

scaling the injector with open loop fueling does exactly the same thing as altering maf voltage, just in a different way.

personally i use the injector scaling as a global fueling adjustment and then fine tune with the maf offset matrix... but i have a wideband on all the time, and started with a zeroed fuel map!
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Old 03-18-2005, 03:19 PM   #6
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Quote:
Originally Posted by happasaiyan
you could figure it out theoretically, but its not cut and dry.

ie- if you know exact airflow (g/s) at the given rpm and IDC, you would know AFR X.
if the other map had the same exact airflow (g/s) at the given rpm with a lower IDC, it would be leaner. but its not exact. so you cant say for sure.
Well my MAF is staying consistently around 4.5 volts as it had on the other map that I did have AFR tuned for and my IDC is still about 5 to 10% higher so i think I could scale the injectors up a bit more.
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Old 03-18-2005, 03:24 PM   #7
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Quote:
Originally Posted by ride5000
i'm not getting the point of your question.

scaling the injector with open loop fueling does exactly the same thing as altering maf voltage, just in a different way.

personally i use the injector scaling as a global fueling adjustment and then fine tune with the maf offset matrix... but i have a wideband on all the time, and started with a zeroed fuel map!
I'm not the most knowledgeable in the working of the Utec parameters. I'm stage 2 and have never really adjusted anything oustide the original setup process needed on the Utec so I wasn't sure about the scaling function.

If it's a global scaling that's really what I need for open loop as I've found for whatever reason all the STi's in the area run EXTREMELY rich. On the stock TXS map my car only put down 260 whp and AFR was below 10:1. The wideband was actually reading 7.3:1 but I don't know how accurate that was. When I leaned it out to 11.4:1 afr I ended the day with 293.4 whp. Biiiiiig improvement but it took a long time of playing with the numbers to get AFR right.

I have a TXS map tuned for 19 psi and dyno proven 300whp and it feels smoother than my map so I was hoping scaling the injectors would simply allow for me to leave the fuel map basically the same (will need a hair of fine tuning) but at least get me near the AFR that it is supposed to be (11:1). Right now, based on my IDC I would say I'm around a low 10:1 AFR. After I get off work I'm going to scale the injector size to 640 and I think that should put me right where I want on my IDC. Tomorrow I'll borrow my buddies wideband and get a reading and see if my theory was correct.

Thank you for your guys' help.
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Old 03-18-2005, 03:55 PM   #8
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scooby bro, he made my injec 590 so he didnt have to go back and fine tune everything lol, but he still kept it the same and finer tuned it now my car makes **** loads of torque, but dude how can you change loads? and WOT my loads change drasitaclly
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Old 03-18-2005, 04:08 PM   #9
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Originally Posted by WRXout
scooby bro, he made my injec 590 so he didnt have to go back and fine tune everything lol, but he still kept it the same and finer tuned it now my car makes **** loads of torque, but dude how can you change loads? and WOT my loads change drasitaclly
yeah that's basically what I'm hoping to do. I'm going to scale the injectors so my AFR is roughly what it was designed to be (11:1) and then I'll fine tune the map to work with my car to give me the best power.

As far as changing loads that is based on the amount of boost you're running. So as your boost falls your load column is going to fall as well. Mine will hit 100 load in the lower RPM's when my boost is hitting the max. As the boost falls and RPMs rise the load column will decrease. So it'll go from 100 load and will end up at 60 load at redline. This is normal and nothing you can change...
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Old 03-19-2005, 09:26 PM   #10
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Bump for an update.

Okay well I got a wideband reading and here are the results. I was a hair richer than my last map but was dead on with the AFR the map was designed for.

Scaled injectors to 680cc

Used a TXS map tuned for 19.4 psi and was 305 whp proven. Without scaling IDCs were maxed and AFR was below 10:1.

After scaling AFR couldn't be more perfect. From 3k to about 5k it's at around 11.3:1 and then from 5K to redline it's a new completely consistent 10.9:1.

Pretty pleased...just surprised I had to scale my injectors so high to get the same AFR the map was designed for.
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Old 03-19-2005, 10:33 PM   #11
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rides point was that scaling the injectors higher is the same as puting negative numbers everywhere in the fuel map. You could have just had really negative numbers(like -5 everywhere as you said) and left the scaling the normal, or changed the scaling and left the numbers close to 0. Either way you will want to fine tune the fueling map.......

peace
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Old 03-19-2005, 10:39 PM   #12
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Quote:
Originally Posted by hippy
rides point was that scaling the injectors higher is the same as puting negative numbers everywhere in the fuel map. You could have just had really negative numbers(like -5 everywhere as you said) and left the scaling the normal, or changed the scaling and left the numbers close to 0. Either way you will want to fine tune the fueling map.......

peace
Yeah I that's what I had done previously but for myself I prefer not having to modify the map but rather just scale the injectors. This map is running better than the one I had tuned so I'll stick with it. It's so much less knock sensitive even though I'm running 19.5 psi instead of 18.5. I'm diggin it.
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