IDC's seem to be a little high for a 16g and 550's??

[JayRolla]

Ok finally fixed some more boost leaks after dropping the motor in my new shell. I had a buddy through on a wbo2 and tune the car to about 10.9 afr. This was at only 9psi. I turned boost up to about 13psi and started logging.

Car will not knock untill about 5800-6000rpm when the IDC's hit about 96% and then causes 4-6 counts of knock till redline.

Now if I pull fuel and get the idc's lower I still get knock, if I add fuel the idc's go to high and I get knock.

Now what would cause the 550's to max out at only 13psi on a 16g?? My buddy says that 550's are way to small for my setup but many of people have made more power on 550's and a 16g.

 

[alex99gst]

Your profile says that your only fuel mods are the 550's and a 190lph pump. Have you rewired the pump? I would think that freeing up some of the major restrictions in the fuel system would help if you wanted to keep the 550's.

The fuel filter and the line to the rail are really restrictive. Replacing that plus an AFPR should help bring the trims down somewhat while keeping the 550's.

I had similar trims with my evo 560's at 18psi on a 14b. I only had an AFPR and a rewired 255.

 

[JayRolla]

Even if I rewire the fuel pump that wouldnt lower the IDC's would it. I thought if the fuel pump was loosing voltage at high rpm I would run lean and IDC's would lower. If I had a fuel pressure regulator maybe I could bump up the FP but I dont know if that would help or make it worse.

I took the mbc off and running 9-10psi and still seeing high IDC's. Im just trying to get a tune for now till I get some big injectors and a 255 so I can run e85 but thats a few months out.

 

[Nofear20]

Something is def not right there. My friend and I are both running 14 psi on the 16g on stock injectors with no issues. I have an AFPR and 255lph fuel pump, but my friend does not (hes on 100% stock fuel system still).

 

[architechnik]

The IDC only shows when it opens up the "flood gate" on the injectors. They are basically little solenoids that let the fuel into the ports; they do not create any additional pressure with higher IDC's, just a greater duration to allow more flow. Contrary to what the name "injector" suggests, it doesn't really inject.

With lower fuel pressures, the injectors will try to stay open longer to compensate for the lack of fuel flow. It appears that your primary problem is fuel pressure behind the injectors, a result of lowered voltage to the pump or restrictions, as Alex noted.

Either rewiring your fuel pump (roughly $10-25 in parts) or removing some restrictions ($60 - $100) or upgrading your pump ($60-$100 and a PITA) should resolve the problem. It may even just be the fuel filter is clogged ($6 - $15).

 

[JayRolla]

They are old injectors and may need cleaning. I will rewire the fuel pump since I have pretty much all the parts laying around. Im about to upgrade to a 255fp, 1150's, Metal fuel filter w/6an line to rail, maf-t and some good old e85. 28psi here I come, hoping to break 380whp on stock cams if possible.

I still need to get a wbo2 which is next and all I need after that is the fuel line, injectors and pump. I was just wondering if anything else could cause it for now, but I guess I will just have to stay off the gas untill I have my new fuel system installed.

Thanks for the info guys.

Jason

 

[architechnik]

Oh, one other thing. The Stock FPR might have gone out and isn't raising pressure when the boost increases. You could also check the vac line going to it to be sure.
On late 1g's with emissions there's a little controller that not too many people are aware of that works similar to the boost solenoid that is adjustable. You can actually change the fuel pressure through that little controller. It's in the bay by the driver's side wipers. Try giving it a couple turns to see what happens if you want to check it out.

EDIT: Never mind about the solenoid. It only works for starting and just keeps the pressure at nil by cuting off the vacuum when you turn the engine over. I suppose it could be stuck and cause it to not deliver the boost pressure when the turbo kicks in, though.

http://members.shaw.ca/dsm.1000q/Engineprimer/1G/solenoids.htm

 

[wishihadatalon]

yeah the 190 is really funny with 550s compared to the 255. For reference I had a 255 in my car and a 22psi on a 16g I was at 88% duty cycle. We put my motor and turbo into my buddies colt, but had to use a 2g fuel pump because it is a little different. It ended up being a 190 and at 21psi I was hitting 101-102% duty cycle on the same 550s.

 

[JayRolla]

Hmm that is wierd. I will have to maybe buy the fuel pump next and see how that helps. Rewire cant hurt either.

 

[matthewdesigns]

Your pump's ability to keep up with flow is going to diminish not only with increased boost psi, but also, as you noted, because the voltage to the pump typically drops at higher rpm's. I have an E316g and have no problems running 18-20psi boost on a rewired 190 and 550's on pump91 (anything above 21psi on my car, and I throw a fuel trim code, b/c I'm running out of fuel at that point). I can't log knock or IDC's on my 2g, but I'm not dropping any timing on my logs. Go ahead and rewire your pump and you'll buy a little more time, and a little more fun in the interim. That way, it's already done when you are ready to install your 255, and you'll need it for using that pump with e85 (and your other fuel upgrades) anyway.

 

[Gamble97]

What if you tried a 2g stock fpr? It's base pressure is slightly higher than the 1g.
I would recommend you change the fuel filter first though.

 

[Black_Bullet]

What if you tried a 2g stock fpr? It's base pressure is slightly higher than the 1g.
I would recommend you change the fuel filter first though.

To properly just increase fuel pressure he'd have to have link or a eprom chip to tell the ecu to compensate for larger injectors...

For example I run the non turbo 1g FPR which has a base fuel pressure of 47.6
yet it still rises 1:1 with boost... ( Dozens of them in the junkyard. I have like 2 extra.)

Back when i had still had the stock 450s this caused my injectors to flow with 505cc characteristics.
Therefore we told the chip that i had 505cc injectors and i was able to get away with up to 18psi on the evo316g with stock cams for a while and the car did a 12.4 at 109 back then on pump gas.

I have 850s now and i am still using the nt fpr to were now i have over 900cc worth of fuel flow at my disposal...

I agree that you need to rewire the pump asap.
Your future fuel mods lists looks good for the e85 though, but if you dont plan on getting a AFPR, then i would consider getting a 2g FPR for the 43psi base pressure when you install all that new stuff because i think most injectors you can buy are all rated at the 2g fuel pressure not the 36psi 1g pressure.
It will allow you to use the injectors to the fullest when you get e85 and not under use them with a lower fuel pressure.

I also believe that increasing fuel pressure lowers the amount/ severity of fuel pressure overrun since your starting your rail pressure at a higher base pressure to begin with.
I recall reading that someone taking note of fuel pressure over run saw it over ran to around 48 psi every time and since i start at roughly 48psi then overrun should be minimum for my setup?
Unless my whole theory is wrong and it will just over run to a higher psi, but i havent found any info yet that would suggest that otherwise.

Im sure people will disagree with something somewhere in there, but thats just my input

 

[alex99gst]

This thread has some good info and links as well.

http://www.dsmtuners.com/forums/bol...-fuel-system-upgrade-installation-review.html

 

[JayRolla]

Well I installed a 255HP fuel pump and IDC's stayed the same. Car is at 15psi now. So I went out and found a n/a FPR and installed that. Went out to do a log and she studdered from being rich. I pull 5% fuel accross the rpm band and it feels great. IDC's hit 91% at highest before I took any fuel out so its much better.

Actually even witht the higher fp, I didnt have to change my lo settings at all to keep the fuel trims good. It runs so much better. Only thing I was confused about is the n/a FPR shows 48psi with the vaccuum line attached. Removed it reads near 60psi!! Is this normal.

 

[aero_sallee]

Well I installed a 255HP fuel pump and IDC's stayed the same. Car is at 15psi now. So I went out and found a n/a FPR and installed that. Went out to do a log and she studdered from being rich. I pull 5% fuel accross the rpm band and it feels great. IDC's hit 91% at highest before I took any fuel out so its much better.

Actually even witht the higher fp, I didnt have to change my lo settings at all to keep the fuel trims good. It runs so much better. Only thing I was confused about is the n/a FPR shows 48psi with the vaccuum line attached. Removed it reads near 60psi!! Is this normal.

Sounds like it could be fpr overrun to me.

 

[JayRolla]

Sounds like it could be fpr overrun to me.

FP over run does not affect WOT tuning so that cant be the issue. My fuel trims are all in order. The 3000gt 180lph I had in before wasnt over running either and I had the same issue. Its fine now, Im getting 85% IDC's at 18psi now on the 550's which is good.