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Old 08-18-2017, 01:09 AM   #551
hondaeater69
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unfortunately i didn't get a fuel pressure reading from when the stock FPR was in there. base pressure should be around 42-45 though... i'm running 52 psi base now and my idcs are still higher. and my Fuel pressure maxes out at 60 WOT. at 18#s of boost with 52 base should be more like 70. and it begins to fall while i'm still WOT. kind of sounds like FP not feeding enough, weird part is, i'm running RICHER than when i was running the OEM FPR. hitting low 10's AFR wise WOT. richer and higher IDCs make sense, but why it's reporting a such low fuel pressure is puzzling.
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Old 08-18-2017, 08:17 AM   #552
no694terry
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im confused on how the IDC changed. Those are set off airflow unless you have open loop fuel correction enabled. Without OLFC, the only way you should get more IDC is either more air or cooler air, or a fuel change. Also a changed in fuel pressure will need a retune. Can you share more info, like fuel pump used, fuel type, how its tuned etc..
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Old 08-22-2017, 03:25 AM   #553
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i've been messing with different fuel pressures is how the IDCs are changing. problem is, they're going the wrong way. with higher base pressure they should be falling to give me headroom for E85, but they're going up.

mods: 06sti engine, 20g turbo, stock side feed tgvs and oem fuel lines, 1000cc dw side feeds, 300dw FP. during one install, installed both aeromotive FPR and cobb flex fuel unit with fuel pressure sensor. the idea was to go to E85 and bump base pressure a bit so that i can use these injectors and not max them out.

after the install, i was instructed by my tuner to set base FP to 52 psi. the plan was to increase fuel pressure, run the base map, then he will revise and send back etc. but i ran into fuel pressure problems, indicated pressure was only going up to 60 or so under 18# of boost at 52 psi base (42 under full vacuum). my first thought was that i'm running out of pump, that doesn't really make sense considering people are making 500HP with the dw300FP. with 52 psi base pressure only going up to 60psi under full boost, my IDCs were higher than with the OEM REG. OEM i never saw 70% IDC. i can get into the 80's now easy, and if i turn the base pressure back down to OEM levels my IDCS go up into the 90"s, with ONLY changing that. this is where it gets weird: my afr's are richer with less indicated fuel pressure. i'm seeing low 10's, and a lot of popping and backfiring under WOT. IDCs going up when it's running richer makes sense, but how it's running richer if i'm running out of FP/pressure doesn't make sense.

maybe i just got a bum regulator.. however, i put the OEM reg back on in the strut tower position (where the aeromotive unit is installed now), and the car breaks up under any positive pressure. this leads me to believe the problem lies outside the regualtor, since neither are working as they should.

i've wanted to go top feed conversion anyway, and have a line on some top feed TGVs, ID1000's and fuel rails. i'm going to go this route and bring it to a tuner/shop. i'm tired of fugging with it.
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Old 08-22-2017, 08:36 AM   #554
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Originally Posted by hondaeater69 View Post
i've been messing with different fuel pressures is how the IDCs are changing. problem is, they're going the wrong way. with higher base pressure they should be falling to give me headroom for E85, but they're going up.

mods: 06sti engine, 20g turbo, stock side feed tgvs and oem fuel lines, 1000cc dw side feeds, 300dw FP. during one install, installed both aeromotive FPR and cobb flex fuel unit with fuel pressure sensor. the idea was to go to E85 and bump base pressure a bit so that i can use these injectors and not max them out.

after the install, i was instructed by my tuner to set base FP to 52 psi. the plan was to increase fuel pressure, run the base map, then he will revise and send back etc. but i ran into fuel pressure problems, indicated pressure was only going up to 60 or so under 18# of boost at 52 psi base (42 under full vacuum). my first thought was that i'm running out of pump, that doesn't really make sense considering people are making 500HP with the dw300FP. with 52 psi base pressure only going up to 60psi under full boost, my IDCs were higher than with the OEM REG. OEM i never saw 70% IDC. i can get into the 80's now easy, and if i turn the base pressure back down to OEM levels my IDCS go up into the 90"s, with ONLY changing that. this is where it gets weird: my afr's are richer with less indicated fuel pressure. i'm seeing low 10's, and a lot of popping and backfiring under WOT. IDCs going up when it's running richer makes sense, but how it's running richer if i'm running out of FP/pressure doesn't make sense.

maybe i just got a bum regulator.. however, i put the OEM reg back on in the strut tower position (where the aeromotive unit is installed now), and the car breaks up under any positive pressure. this leads me to believe the problem lies outside the regualtor, since neither are working as they should.

i've wanted to go top feed conversion anyway, and have a line on some top feed TGVs, ID1000's and fuel rails. i'm going to go this route and bring it to a tuner/shop. i'm tired of fugging with it.
The IDC in open loop still shouldnt change no matter what you set base pressure to.

The pulse width is controll by the tune. For example if MAF is reading 3.0 volts at 4,000 rpm (plus compensator, temps etc) it will inject say 15ms of fuel (depending on injector sclae,latency etc). The only impact fuel presure will have is have much fuel gets past the injector in the 15ms. But thd Duty cycle stays per the tune.

Now in closed loop, the o2 sensor will pick up the extra fuel from the extra pressure and reduce IDC to get back to target. This will show up in the AF learning values as a negative number.

I'd be wary going to high on base pressure with sidefeeds. They are already pretty slow, too much base presure may cut you idle and cruise IDC's to the point of misfires. I use to run DW850's sidefeeds and went to top feeds. no regerts
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Old 08-22-2017, 12:41 PM   #555
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The IDC in open loop still shouldnt change no matter what you set base pressure to.

The pulse width is controll by the tune. For example if MAF is reading 3.0 volts at 4,000 rpm (plus compensator, temps etc) it will inject say 15ms of fuel (depending on injector sclae,latency etc). The only impact fuel presure will have is have much fuel gets past the injector in the 15ms. But thd Duty cycle stays per the tune.

Now in closed loop, the o2 sensor will pick up the extra fuel from the extra pressure and reduce IDC to get back to target. This will show up in the AF learning values as a negative number.

I'd be wary going to high on base pressure with sidefeeds. They are already pretty slow, too much base presure may cut you idle and cruise IDC's to the point of misfires. I use to run DW850's sidefeeds and went to top feeds. no regerts

interesting i didn't realize that regarding IDC's. i assumed when i bumped pressure the IDC's would fall since the ecu now now needs to allow the injector open time less to hit xyz fuel target. i'm assuming the ecu doesn't know or care or what the fuel pressure is, it's just trying to a hit final fueling number.

just got a revised map with less fuel in it, and my afr's came back to normal in the low 11's. idcs were less at 60%, less than what the OEM reg was showing. this is good news. AFRs are the same as they were before but IDC's have dropped, which was my intention all along. problem is my indicated pressure is still way way off. at 18#'s it maxed out at 63 and was falling during the pull into the 50's.

i'm beginning to think the fuel pressure reading is simply not correct. at this point everything seems fine with AFR and IDC is acting the way it should, but reported fuel pressure is low. i just don't know why.

i orignially had the FP sensor in the aermotive bung. thought maybe that was the issue, so i put it in the feed line on the cobb ethanol sensor unit. however it still reads the same low bunk readings. maybe it's not calibrated properly but i asked the tuner and he assures me it is.
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Old 08-22-2017, 01:23 PM   #556
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interesting i didn't realize that regarding IDC's. i assumed when i bumped pressure the IDC's would fall since the ecu now now needs to allow the injector open time less to hit xyz fuel target. i'm assuming the ecu doesn't know or care or what the fuel pressure is, it's just trying to a hit final fueling number.

just got a revised map with less fuel in it, and my afr's came back to normal in the low 11's. idcs were less at 60%, less than what the OEM reg was showing. this is good news. AFRs are the same as they were before but IDC's have dropped, which was my intention all along. problem is my indicated pressure is still way way off. at 18#'s it maxed out at 63 and was falling during the pull into the 50's.

i'm beginning to think the fuel pressure reading is simply not correct. at this point everything seems fine with AFR and IDC is acting the way it should, but reported fuel pressure is low. i just don't know why.

i orignially had the FP sensor in the aermotive bung. thought maybe that was the issue, so i put it in the feed line on the cobb ethanol sensor unit. however it still reads the same low bunk readings. maybe it's not calibrated properly but i asked the tuner and he assures me it is.
Theres a lot of factors in IDC. Load, coolant temp, intake temps, etc... There's some pulls i'll hit 29psi at 94% duty cycle then the next morning I do the same pull on same on ramp and hit 105% duty cycle and the same 12:1 AFR. Just depends on the air density and how you taught the ecu to account for it. My peak IDC is at redline, the borg just never quits
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Old 08-22-2017, 01:42 PM   #557
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Theres a lot of factors in IDC. Load, coolant temp, intake temps, etc...

i get that. just trying to understand from a diag perspective, if my changing the base fuel pressure should be affecting IDC's. you're saying, all else equal, changing the base fuel pressure should have no affect on IDC's... right?
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Old 08-22-2017, 02:02 PM   #558
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i get that. just trying to understand from a diag perspective, if my changing the base fuel pressure should be affecting IDC's. you're saying, all else equal, changing the base fuel pressure should have no affect on IDC's... right?
It would only effect closed loop fueling where the O2 sensor can see the effects of the pressure change. For example, on my car when i bumped the fuel pressure up to 58psi. I went into the injector scaler and "corrected" it. I used some deatchwerks flow sheets to make an educated guess on static flow for 950cc's injectors. The injectors were 950cc at 3bar (43psi) at 4 bar, they flow like 1100ish. So i changed my scaler to 1100. This kept my fueling on target without a complete were work of my VE table. The computer will calculate the new IDC based off the the 1100cc input. So in theory the IDC will go down, since 1100cc flows more than 950cc per cycle. Then the only corrections I needed were around idle and cruise where latency would com into play.

and by IDC, i mean injector pulse width. IDC is just the percent of time the injector is open during each 2 strokes.

So yes, all being equal, changing the pressure should not effect IDC. The computer is unawre of any pressure chnage and thus makes no corrections on its own (only in closed loop). I assume the computer is basing everything of 3bar fuel pressure, and uses the MAP sensor as part of its fuel correction. There may even very well be a table inside the ECU for changing the factory fuel pressure calculation, i just dont think anyones ever defined it, if it exists.

Last edited by no694terry; 08-22-2017 at 02:11 PM.
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Old 08-22-2017, 02:31 PM   #559
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ok thanks for explaining that.
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Old 11-27-2017, 09:57 PM   #560
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So for those running Cobb Flex Fuel what are the issues if any? Looking for GD 2004-2007 results/issues. Searched and no thread(s).
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Old 11-28-2017, 12:01 AM   #561
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So for those running Cobb Flex Fuel what are the issues if any? Looking for GD 2004-2007 results/issues. Searched and no thread(s).
Assuming you have a competent tuner... it works perfectly - good as stock FlexFuel.
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Old 12-07-2017, 07:52 PM   #562
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Hey can any of you GD guys help me out please. Iím trying to install the Cobb flex fuel. I have aftermarket fuel lines and aeromotive FPR so Iím not actually sure how I need to connect the fuel lines. Thanks!
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Old 12-08-2017, 10:43 AM   #563
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You'll need to plumb in aftermarket fittings. The Cobb kit isn't designed for anything but stock nor do they sell you want you need and leave out the crap you don't need if you have an upgraded fuel system. It gets expensive for the little converter box you need...
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Old 12-08-2017, 11:10 AM   #564
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id just buy the innvate kit. comes with a eca, sensor, gauge, wideband and fuel pressure sensor which im almost certain is completely compatible with the accessport. its just not "plug n play" youll actually have to wire it
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Old 12-26-2017, 12:23 AM   #565
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Hey can any of you GD guys help me out please. I’m trying to install the Cobb flex fuel. I have aftermarket fuel lines and aeromotive FPR so I’m not actually sure how I need to connect the fuel lines. Thanks!
Easiest placement would be to put it on the return after the AFPR. I asked this question a page or 2 back...but yea I bought all types of fittings to fit the COBB kit to turn everything into -AN.
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Old 04-01-2018, 11:29 AM   #566
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Is it worth it to buy the whole kit from cobb or just buy bits and pieces from them and source the rest yourself?
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Old 04-04-2018, 11:15 AM   #567
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Is it worth it to buy the whole kit from cobb or just buy bits and pieces from them and source the rest yourself?
I don't work for Cobb, but really love their military discount!!! I am having my flex fuel kit, 1050x injectors, AEM fuel pump and Fuel Pressure Regulator (FPR) installed tomorrow with a tune.. The downside is having to drive 3.5 hours to get it done. Found a Cobb certified "Pro-Tuner" just outside of NYC and I live in Syracuse But I'm stoked about going full Stage 3 with the added Flex Fuel E85 option for "Feeling Spunky" day's....

I would recommend getting Cobb kit's for peace of mind and customer support...Granted my STi has less than 2K miles on it, but I'd rather keep everything within the same manufacturer for ease of troubleshooting (should there be any) and tried and true combo's... But I'm sure there are other options out there that will save a few pennies !!
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Old 04-06-2018, 03:31 PM   #568
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x2 their FF + FP kits are literally plug and play and worth it - quality is top notch. I pieced together the fuel lines and fueling (I went with the DW300 FP and ID1300X injectors). The rest is worked out by the Pro-Tune.
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Old 04-13-2018, 12:19 PM   #569
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Easiest placement would be to put it on the return after the AFPR. I asked this question a page or 2 back...but yea I bought all types of fittings to fit the COBB kit to turn everything into -AN.
It's always best to put the ethanol sensor on the pressure side of the regulator (Feed Side), if possible. This is because the return side fuel flow can be reduced to a trickle in high boost situations (especially if you have a borderline fuel system), causing erratic ethanol content readings.

However, the Cobb flex fuel ecu allows a compensation for this, freezing the ethanol content above certain levels (boost, maybe RPM, can't remember all the possible choices), so even if you are getting low amounts of fuel through the sensor, it will use the ethanol content it measured before you went over those levels.
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Old 08-17-2018, 03:46 PM   #570
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This is a great thread, so much info
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