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Old 04-08-2005, 02:43 PM   #1
WRXout
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Default utec injector scaling question.

I got tuned with my utec injector size set to 590 and my stock at 550, its a 05' sti with downpipe and catback, and utec.......
so if i change my injectors the utec ones to 550 instead of 590 what would happen? qould my afrs go all wack?
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Old 04-08-2005, 03:01 PM   #2
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If you got tuned, why would you want to mess with what your tuner did? Are you unhappy?

And the answer to your question is yes, there would be a change to your a/f.
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Old 04-08-2005, 07:19 PM   #3
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Changing the UTEC injector size from 590 to 550 will meake you run rich!

What is the issue you think you are correcting?
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Old 04-08-2005, 07:47 PM   #4
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my car starts up funny sometimes , likes its about to stall.....and thats it really, i remmever putting them to 550 and the car turned on alot smoother and im idleing low like around 650 the 3rd bar starting from 0, below the 1k

I'm thinking spark plugs?
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Old 04-09-2005, 11:43 AM   #5
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Try setting the factory injector size to 590 as well, and see if the startup improves.

This change will prevent the UTEC from applying any MAF scaling while under the TPS crossover, but still allows the UTEC to use the "590" OLF fueling.
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Old 04-09-2005, 12:42 PM   #6
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but isnt that bad for the injectors? wont my afr's change?
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Old 04-09-2005, 02:04 PM   #7
dosage0
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Quote:
Originally Posted by x99percent
Try setting the factory injector size to 590 as well, and see if the startup improves.

This change will prevent the UTEC from applying any MAF scaling while under the TPS crossover, but still allows the UTEC to use the "590" OLF fueling.
Quote:
Originally Posted by WRXout
but isnt that bad for the injectors? wont my afr's change?
This is how I understand it. Your stock ECU can adjust itself for ~ 25% change in fueling on its own. That means it can pull enough fuel to handle stockers/pinks/etc. Thats great for most of us, but for the people with much larger injectors, the UTEC needs to "help" the stock ECU out pulling more fuel under the crossover point that you set in your parameters. So there are two levels to do this. The Factory injector size is usually 540 and your aftermarket injector size goes in the other injector size slot in the UTEC. Its like a ratio that helps the ECU control fueling below the TPS crossover point. IE: If you put in 540/1080 (dont do that haha) the UTEC would half the signals to the ECU and the ECU would put in half the fueling under the crossover point.

Once the UTEC takes over control it uses the second number for OLF (1080) which should be the actual size of your injectors.

What X99 is saying you should do is up your stock injector size to 590/590. That would make your car put in more gas while the ECU is in control, but still use 590 when the UTEC takes over in OLF once you pass the crossover point.

Your AFRs will change, but they will only change under the crossover point where you say you are having problems with spuddering / stalling.

EDIT: As to the question of being bad for your injectors? An injector is like a faucet.. you can turn it on 25% -- 50% --- or full blast. I dont think any % is any worse or better. Although you wouldnt want them to stick at 100% for any length of time.

Before you take this as fact though, I'd rather have a few more experienced people look over what I've written. I'm pretty sure its correct, but its just my understanding and I don't do this for a living

Rob
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Old 04-09-2005, 02:15 PM   #8
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Quote:
Originally Posted by WRXout
but isnt that bad for the injectors? wont my afr's change?
No and no.

The OLF "injector flow" parameter determines the scaling of the OLF fuel map. A larger number = shorter pulsewidths overall, while a smaller number = longer pulsewidths. This is why Mick stated that changing this number from 590 back to 550 will make your car run richer.

The "split" between the two numbers determines the amount of correction applied to the MAF signal that the ECU sees. On most setups, this only matters when you are below the TPS crossover. Since you are running the stock injectors and intake, you shouldn't need any "split". This is why I suggested changing the "stock injector flow" parameter to 590. I think that making this change should have no effect on your tuned AFRs.
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Old 04-09-2005, 02:25 PM   #9
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Quote:
Originally Posted by dosage0
What X99 is saying you should do is up your stock injector size to 590/590. That would make your car put in more gas while the ECU is in control, but still use 590 when the UTEC takes over in OLF once you pass the crossover point.
Not "more gas", but the ECU will see a higher MAF signal (more airflow). It is very likely that the ECU will need to apply less fueling correction with the new, higher MAF signal than with the UTEC-reduced MAF signal it is seeing now.

Quote:
Originally Posted by dosage0
Your AFRs will change, but they will only change under the crossover point where you say you are having problems with spuddering / stalling.
The UTEC cannot change AFRs while the ECU is in control. Typically, the ECU targets ~14.5-14.7:1 AFR while idling or cruising. It does this based on feedback from the front O2 sensor (a closed-loop feedback system).

The point of making changes with the UTEC to ECU-controlled areas of the fuel map (e.g. the 0% column) is to provide a MAF signal to the ECU that doesn't make the ECU have to use large fueling corrections. Under "normal" driving conditions (cruising, idling), the ECU almost always applies fueling corrections to achieve the AFRs it wants to run. It is thought that the smaller those corrections are, the better the car will start/run/drive/feel.
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Old 04-09-2005, 03:17 PM   #10
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Quote:
Originally Posted by x99percent
Not "more gas", but the ECU will see a higher MAF signal (more airflow). It is very likely that the ECU will need to apply less fueling correction with the new, higher MAF signal than with the UTEC-reduced MAF signal it is seeing now.

The UTEC cannot change AFRs while the ECU is in control. Typically, the ECU targets ~14.5-14.7:1 AFR while idling or cruising. It does this based on feedback from the front O2 sensor (a closed-loop feedback system).

The point of making changes with the UTEC to ECU-controlled areas of the fuel map (e.g. the 0% column) is to provide a MAF signal to the ECU that doesn't make the ECU have to use large fueling corrections. Under "normal" driving conditions (cruising, idling), the ECU almost always applies fueling corrections to achieve the AFRs it wants to run. It is thought that the smaller those corrections are, the better the car will start/run/drive/feel.
so by changing my ecu injector size to 590, it can allow myidle to be better, and maybe fix the hesitation going into the "transition point"? and the ecu wont be confused of this?are thier chances of running lean?

Last edited by WRXout; 04-09-2005 at 04:27 PM.
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Old 04-09-2005, 05:58 PM   #11
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Quote:
Originally Posted by WRXout
so by changing my ecu injector size to 590, it can allow myidle to be better
More than likely.

Quote:
Originally Posted by WRXout
and maybe fix the hesitation going into the "transition point"?
I have no way of knowing. That depends heavily on how your UTEC map is set up.

Quote:
Originally Posted by WRXout
and the ecu wont be confused of this?
If anything, less confused.

Quote:
Originally Posted by WRXout
are thier chances of running lean?
Not that I am aware of.
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Old 04-09-2005, 07:36 PM   #12
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cool i was talking to a tuner friend from EQ, and i understand that if its OLF then scaling the stock injectors to 590 cc to match the utec injector sizes, its ok.
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Old 04-09-2005, 10:42 PM   #13
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you seem surprised the advice you got here was legit!

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Old 04-10-2005, 06:18 PM   #14
dosage0
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Quote:
Originally Posted by x99percent
Not "more gas", but the ECU will see a higher MAF signal (more airflow). It is very likely that the ECU will need to apply less fueling correction with the new, higher MAF signal than with the UTEC-reduced MAF signal it is seeing now.

The UTEC cannot change AFRs while the ECU is in control. Typically, the ECU targets ~14.5-14.7:1 AFR while idling or cruising. It does this based on feedback from the front O2 sensor (a closed-loop feedback system).

The point of making changes with the UTEC to ECU-controlled areas of the fuel map (e.g. the 0% column) is to provide a MAF signal to the ECU that doesn't make the ECU have to use large fueling corrections. Under "normal" driving conditions (cruising, idling), the ECU almost always applies fueling corrections to achieve the AFRs it wants to run. It is thought that the smaller those corrections are, the better the car will start/run/drive/feel.

a higher maf means more airflow to the ECU right? I was just assuming that a higher MAF would lead the ECU to add more gas to compensate for the greater amount of air.

IE: If the ECU puts in X amount of fuel when the maf is 3.5, wouldnt it put in more fuel to obtain the same ratio 14.5 when the MAF is 3.7?

I guess then im leaving out the front o2 sensor. But why would it matter at all what the UTEC throws at the ECU if the ECU is just going to do corrections based on the front o2 sensor?

Rob
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Old 04-10-2005, 10:26 PM   #15
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bump so someone smarter than me reads this.
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Old 04-10-2005, 11:52 PM   #16
x99percent
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Quote:
Originally Posted by dosage0
a higher maf means more airflow to the ECU right? I was just assuming that a higher MAF would lead the ECU to add more gas to compensate for the greater amount of air.
Yes, until the ECU makes corrections to attain the proper AFR.

Quote:
Originally Posted by dosage0
IE: If the ECU puts in X amount of fuel when the maf is 3.5, wouldnt it put in more fuel to obtain the same ratio 14.5 when the MAF is 3.7?
Until the ECU learns (a few minutes), yes.

If the ECU is injecting X fuel for an AFR of 14.5:1 with a MAF voltage of 2.0, then it is going to inject *more* fuel (X + ??) when it sees a voltage of 2.2... but then, thanks to the O2 sensor, the ECU will realize that it is running rich. Next, the ECU will begin making negative corrections to the fueling until it sees that same 14.5:1 AFR again. In the end, the ECU should be injecting the same X fuel that it was before the change was made.

Quote:
Originally Posted by dosage0
I guess then im leaving out the front o2 sensor.
Yep.

Quote:
Originally Posted by dosage0
But why would it matter at all what the UTEC throws at the ECU if the ECU is just going to do corrections based on the front o2 sensor?
It is considered "better" if the ECU doesn't have to make large corrections.
It is definitely considered to be A Bad Thing™ if the ECU has to correct so much such that it ends up throwing a CEL ("system too lean" or "system too rich").
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