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Old 06-09-2004, 06:08 PM   #1
TexRex2002
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Default Still can't get modded injectors to run right. Ready to give up

I don't know whether to blame firmware 4.2, or the modded injectors or what.

my latest attempt:

I have injector scaling set to 860. My fuel pressure is 50 psi. I spent over an hour tuning the zero percent column by watching the fuel trims, and I have the LTFT setle in right at -3 with the AC off and +4 with the AC on, at almost all rpms

I have +14% in my zero percent column from 1500 on up +10 and +12 below that. My 10% column is then -2%, otherwise it gets way too rich, and goes all the way down to -8% in the higher load sites.

Gentle pulls followed by gentle letoffs result in massive bucking. accelerating hard and backing out of the throttle slowy (to accelate at a slightly lesser pace) results in bucking as well.

Why in the hell do I need to put +14 in the zero, and the -6 or -8 in the high load columns?

It doesn't make any freaking sense.

I used to have the injectors scaled to 740 and then ran a "tuna" tuned map, and it ran just as well under load, didn't buck ever, but would constantly stumble lean when dropping to idle and throw a CEL every day. back then the 0% values were around zero, and the map contained values approaching -18.

I am really at my wit's end. I have been fighing this GD car for months now, and I am about ready to nail a tree with it and just make the insurance claim.

WTH is wrong with my POS car?

There is NO intake leak, pre or post turbo. I have checked over 20 times in the course of the last several months.

I've cleaned the MAF. I don't really know how to check the O2 sensor, but it has only 22k miles on it and has never seen leaded gas.

The only other oddity is that it runs WAAAY lean right at about 2000 rpm when using a stock stage 4 map. I had to add in around 8% MAF or so from 2000 - 2500 in the 10, 20 and 30 % load sites. that was sort of wierd, but the additons to the map corrected it nicely. Everywhere else in the map I had to pull fuel out to bring it up to 10.9 : 1 under heavy load, like one would expect of a TXS map.
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Last edited by TexRex2002; 06-09-2004 at 06:18 PM.
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Old 06-09-2004, 06:19 PM   #2
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Your fuel pressure is 50psi at what point?

It is supposed to be 43psi when you pull the vacuum line off of the regulator at idle. Idle with the line on should be around 32-35psi.
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Old 06-09-2004, 07:26 PM   #3
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50 psi with the vacuum line off at idle.

I crushed the FPR to get a little mre out of the STi pinks, but was running high 90's IDC's and cut my stockers.

I sold the Pinks, or I would try them again just for fun to see if it solves the problem.
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Old 06-09-2004, 07:39 PM   #4
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Zero the fuel map.... Adjust the stock injector size (smaller setting) until your trims are close.. keep at it until you get those trims close.. Reset the ECU and utec each time you change it. I noticed the lower closed loop injector setting works backwards of the open loop or larger one. Once you get that scaling as close as you can you can then go into the fuel map and the 0 column and tune for RPM. Next.. Adjust the larger open loop scaling so your WOT AFR's and or your transition to open loop AFR's are "in the ball park".. Now tune your fuel map as normal.

I have been able to make these injectors work pretty well... The only issue I can see is some rich AFR on cold start. Other then that they work..

C
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Old 06-09-2004, 07:58 PM   #5
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Quote:
Originally posted by AZScoobie
Zero the fuel map....
I take it you mean in the 0% column only, correct?
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Old 06-10-2004, 09:23 AM   #6
TexRex2002
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Quote:
Originally posted by AZScoobie
Zero the fuel map.... Adjust the stock injector size (smaller setting) until your trims are close.. keep at it until you get those trims close.. Reset the ECU and utec each time you change it. I noticed the lower closed loop injector setting works backwards of the open loop or larger one. Once you get that scaling as close as you can you can then go into the fuel map and the 0 column and tune for RPM. Next.. Adjust the larger open loop scaling so your WOT AFR's and or your transition to open loop AFR's are "in the ball park".. Now tune your fuel map as normal.

I have been able to make these injectors work pretty well... The only issue I can see is some rich AFR on cold start. Other then that they work..

C

Hey thanks for the help. I have tried messing with the stock injector size. The end result is always the same: I end up with a massive jump between ecu and open loop fueling numbers, and it makes the transition difficult.

I've changed my 0% column to be +14 below 2000 rpm and then quickly scale down to 4 above that. To hell with LTFT above idle. At least the transition won't be so bad.

If that doesn't work I'll likely sell the whole damn thing. What a pita.
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Old 06-10-2004, 11:39 AM   #7
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If your jump is not right your scaling is not right... Period.. End of story.. Sorry you are having such a hard time with it Tim. This is something I do everyday and once I got the hang of it and understood what I was doing its easy.. Wish I was there to help in person.. Probably will be in a month or so. You should never need that kind of large number correction with 4.2 software though..

Cya

C
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Old 06-10-2004, 12:00 PM   #8
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Well, SQRT(50/43) = ~1.08 <= estimate of increased flow from fuel pressure)

cut stockers run 840ish?, so with the added fuel pressure they are effectively ~910. If they were 860 at 43, then ~930 at 50. That is probably the range for the injector scaling you want, 900 - 930.

Quote:
Originally posted by TexRex2002
To hell with LTFT above idle.
That could be happening, Since the LTFT is still being adjusted above idle and it is screwing with your map.

On my stock fuel system I've pulled -2 out at idle to get more consistent fuel trim. Anyway, Good luck!
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Old 06-10-2004, 02:14 PM   #9
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Quote:
Originally posted by AZScoobie
Zero the fuel map....
Do you mean the entire fuel map?

Quote:
Originally posted by AZScoobie
Adjust the stock injector size (smaller setting) until your trims are close.. keep at it until you get those trims close.. Reset the ECU and utec each time you change it.
For the STi, is your “Stock Injector Flow” field set to <480? Where did you end up at with this field? At this point did you leave the “Injector Flow” field 480 or did you put in what you thought was close (840 or …)?

Quote:
Originally posted by AZScoobie
I noticed the lower closed loop injector setting works backwards of the open loop or larger one.
Do you mean that the “Stock Injector Flow” field works backwards from the “Injector Flow” field? By backwards do you mean when you make it smaller you’re getting more fuel because the ratio between the two fields is getting bigger because the “Stock Injector Flow” field is getting smaller? If not, then what do you mean?
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Old 06-10-2004, 03:38 PM   #10
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Yes the whole map.. I start out with a zero map, set the two scaling settings until it is as close as I can get it.. Then tune the fuel map.

We are not talking about an STi..... This is a WRX with a 2.5 ect.. Scaling will be different.

He likely needs to put the stock lower lower setting to 300 if that clarifies things.

Cya

C
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Old 06-10-2004, 05:06 PM   #11
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Quote:
Originally posted by AZScoobie
Wish I was there to help in person.. Probably will be in a month or so. Cya

C
ok, I'll not sell the car for another month or so...

I am getting CELs again (too lean P0171) when the car drops to idle, stumbles around at 500 rpm and then rebounds (not always, about once a day).
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Old 06-10-2004, 05:54 PM   #12
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Quote:
Originally posted by AZScoobie
Yes the whole map.. I start out with a zero map, set the two scaling settings until it is as close as I can get it.. Then tune the fuel map.

We are not talking about an STi..... This is a WRX with a 2.5 ect.. Scaling will be different.

He likely needs to put the stock lower lower setting to 300 if that clarifies things.

Cya

C
Thank you for the answers.
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Old 06-10-2004, 05:55 PM   #13
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check your AFR reading of the factory probe... You can get that code if your AFR sensor is reading lean when the trims are maxed rich.. Sounds like its a bad probe or the Trims are way out of wack...

C
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Old 06-10-2004, 11:48 PM   #14
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Quote:
Originally posted by AZScoobie
I noticed the lower closed loop injector setting works backwards of the open loop or larger one.

It is not that it works backwards from the top one, it is that the ratio of the two numbers is all that matters. If you rase the top one the ratio increases, it also increases if you lower the bottom one. When ever they are equal the ratio is 0, so there is no scaling. That is why on a STi the numbers can both be 480/480 and no change to the 0% column occurs, and with the WRX 420/420 is no change.

I have not looked at the UTEC on an Evo, but it is the same. The ratio between the two is what determines the fuel correction.


Tim, if you are running 14% MAF correction in the 0% column your injector size is set to large. You are having to add in fuel to make it run, which means that the ECU thinks the injector is larger than it is causing it to run a lower IDC, making you run lean.

Edit: Thanks Nathan, updated.

Last edited by pegdrgr; 06-11-2004 at 10:43 AM.
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Old 06-11-2004, 12:35 AM   #15
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Quote:
Originally posted by pegdrgr
That is why on a STi the numbers can both be 480/480 and no change occurs to the map, and with the WRX 420/420 is no change.

.
Should read "...no change in the 0% column."

As for tuning modified stock injectors, I had one set that 740 seemed to work just fine, and another where we ended up putting 700 in the map and then using the select monitor to pull fuel out as needed in the 0% column. Both cars were smooth enough during the road test that you would think they were STI or stock injector cars.

On the modified stock USDM STI injectors I use 800cc as my injector flow rate.
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Old 06-11-2004, 12:45 AM   #16
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Quote:
Originally posted by pegdrgr
Tim, if you are running 14% MAF correction in the 0% column your injector size is set to large. You are having to add in fuel to make it run, which means that the ECU thinks the injector is larger than it is causing it to run a lower IDC, making you run lean.
I think this is oversimplifying the issue. I run +9 in 0%, very close to 0 in most of the rest of the map, with 850 scaling on modified injectors and stock MAF housing/2.0L, to get my trims within the min/max range in a variety of conditions. Now, +14 seems like too much, and I don't quite know what the problem is with his car as it is different than mine, but I don't believe that having to add fuel in the 0% column means the scaling ratio is too large. It probably means the factory ECU responds in a non-linear fashion to extremely low idle MAF voltages, or that there's a math problem in the UTEC that is exposed at the low end of the flow range. I really have no idea. I just have my very nicely running map with good LTFTs and smooth transitions that has a rather large amount of fuel added in the 0% column compared to the rest of the map. Now, could I run a lower scaling value with 0 in my 0% and then big negatives in the rest of the map? Sure, but the effect would be the same, and I'd rather have one column look funky than 10. With his particular setup he may need to run even more in the 0%. Going back to stock fuel pressure may be one idea that would at least make the car more representative of others running modified injectors.
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Old 06-11-2004, 09:13 AM   #17
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Quote:
Originally posted by AZScoobie
check your AFR reading of the factory probe... You can get that code if your AFR sensor is reading lean when the trims are maxed rich.. Sounds like its a bad probe or the Trims are way out of wack...

C
Well, here's another oddity: when I have a tuna monitoring the motor, my A/F column is dead on 14.7 at idle and gentle putting around. When I turn the tuna off and use just the UTEC (relying on the stock front O2 sensor) A/F is all over the place. 12.9, 14, 13.9, 15.7, 14.3, 13.1

Strange. I would think that if the probe isn't working properly the motor would struggle to run at the appropriate ratio, but the tuna probe confirms that it runs right on.
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Old 06-11-2004, 09:19 AM   #18
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Quote:
Originally posted by nmyeti
As for tuning modified stock injectors, I had one set that 740 seemed to work just fine, and another where we ended up putting 700 in the map and then using the select monitor to pull fuel out as needed in the 0% column. Both cars were smooth enough during the road test that you would think they were STI or stock injector cars.
I will try scaling down the injectors again. I was trying 860 as an injector scaling out of sheer orneriness, since with raised FP and everyone claiming 850cc flow (at stock FP) out of the de-capped injectors, I figured the scaling HAD to be at least that high.

I had run 4.2 with STI pinks, and the scaling turned out to be right on when set to 560, and later to 610 when I upped the FP.

However, with cut stockers and 50 psi fp, I remember having the scaling set at 740, and I had gigantic numbers in the fuel map at high rpm, high load. like -16 and -18

I'll report progress when it is made
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Old 06-11-2004, 10:49 AM   #19
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Quote:
Originally posted by Macabre
I think this is oversimplifying the issue.

I was just indicating the trend. If he wants to lower his 0% column he needs to decrease the injector size in the scale feature. I also say that becuase I have seen his car run MUCH better than it is now, and I do not believe he is running the ideal size.

Tim lets try swapping out your O2 sensor with one of mine, just in case that is messing with you a bit. IIRC it is a little enhanced from the motor swap.
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Old 06-11-2004, 11:47 AM   #20
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Your going to run around in circles like a cat with scotchtape on its tail if that front AF probe is not working... It should read very close to the Tuner's WB....

C
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Old 06-11-2004, 01:49 PM   #21
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I have a cat, I have scotch tape, perhaps I should try that to see how fustrating this could be...



We are going to try swapping the MAF sensor, and then the front O2 sensor today. I think the O2 is ok, since the Tuna does not show the variation, and it is not a large variation, but we will play with things and see. He has an unusual intake on it also, so that may be hurting things a bit.
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Old 06-11-2004, 02:04 PM   #22
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red flag...... Unusual intake? Monitor the idle MAF voltage.. It should be pretty steady. If its jumping around then you need to fidget with the intake.. for example.. If the intake pipe is smooth you could have this issue.. Adding in the stock convoluted rubber hose or some screen to smooth airflow might fix the problem.. Sometimes simply rotating the MAF sensor a bit or shiming it up will help.

C
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Old 06-11-2004, 02:31 PM   #23
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Funny, not 30 minutes ago I asked him what the MAF voltage looked like.

The intake is standard, but he added a pipe where the filter was to push it into the fender well.
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Old 06-11-2004, 03:42 PM   #24
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Thats a possibility... You will know in 2 seconds after watching the MAf voltage on DD...

P.S Did you try the scotchtape on the cats tail?


C
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Old 06-11-2004, 09:07 PM   #25
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We did not get to that today. Instead we installed ceramic coated exhaust manafolds, and fixed his leaky oil pan gasket. I did give him my MAF sensor to try to fix the idle issue.
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