Zilla's rebuild (exhaust mod revealed, gauges going in.....) - Page 53 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Performance, Brainstorming & Tuning Talk about modifications, or anything else associated with performance enhancements. Have a new idea for performance/reliability? Post it here. No idea is stupid! (please use Detailing and Appearance for cosmetic ideas)

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Old 06-27-2007, 11:40 AM   #521
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just curious but how do you change your fueling when you change your pulley sizes
everytime i swap pulleys it takes a couple of minutes of heart to heart with my afc!
and it doesnt hurt the i have bigger injectors to start off with.
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Old 06-27-2007, 12:09 PM   #522
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Your PROBLEM is the AFC. It'* a diagnostic tool to be used to gain data in order to have a custom PCM burned. Additionally, your injectors are FAR too big for your application, causing you further issues.

If your injectors are properly sized, your PCM can still adapt with minor tweaks. The tweaks I use are from an AFPR. By increasing the pressure, the effective lb rating of my injectors increases, and I benefit further from better atomization of the fuel. This is why I'm still running stock injectors.

In addition, besides your horribly oversized injectors, your FPR is only a 2.7bar regulator. Only the 94/95 L67'* got it. Which puts you at a further disadvantage with your injectors being too big for your application.

There is no power to be gained in going larger on the injectors unless you're outflowing your existing injectors, which you are not.

I ran a 2.0" pulley with zero KR last year on stock 29lb injectors. I don't have to make any changes to my fueling when switching between the ranges of 2.5-2.0" pulleys. Your PCM should be able to adapt to it if your injectors are properly sized for your application.
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Old 06-27-2007, 12:23 PM   #523
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your right i do have a 2.7 in it now
what would change if i put a 3.0 in it??
and what is an AFPR do you have a pic??
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Old 06-27-2007, 12:40 PM   #524
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2.7bar is 39psi
3.0bar is 43.5psi

Going to a 3.0bar regulator with those grossly-oversized injectors are going to cause you even more problems. Your fuel is already virtually drooling out of them with poor atomization as it is. If you upped your pressure, the PCM would have to back your injectors off to manage proper AFR. They're too big. You're probably over-fueling right now, or just on the border of it.

Go back to stock injectors.

I'm running a Walbro 255 fuel pump, but a new OEM stock Series 1 L67 fuel pump will still support 400hp. I'm also running a Casper'* AFPR, which is an adjustable that goes up to 4bar (58psi). They are no longer available.

By this method, I can make my 29lb injectors flow at the same rate as a 33.5lb injector with no changes to PW or DC from the PCM necessary. And gain the benefits of better fuel atomization, which gives me better efficiency and power.

Low fuel pressure on over-sized injectors is FAR worse than higher fuel pressure on properly sized injectors.
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Old 06-27-2007, 12:42 PM   #525
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I see
thanks for the advice
JJ
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Old 06-27-2007, 12:50 PM   #526
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Your biggest problem is that you oversized your injectors, and now survive with the AFC. That shouldn't be necessary. You need to tune properly using MECHANICAL methods (proper selection of parts) before you resort to 'electronic' tuning. This is ALWAYS true.
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Old 06-27-2007, 12:53 PM   #527
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i still have my stock injectors and i found a 3.0 bar FPR so I'll give that a go as soon as i have a chance

do you have your wide band hooked up yet, with readings to share/compare
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Old 06-27-2007, 12:53 PM   #528
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As a little more info, my third AFC has recently failed. I think it still "works", but the display has scrambled and I don't have a clue how my settings are or if I'm in advanced or standard mode.
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Old 06-27-2007, 02:03 PM   #529
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Buickman, read the previous page of this topic for the update on my wideband.
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Old 06-27-2007, 05:08 PM   #530
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Quote:
Originally Posted by willwren
Needless to say, the car was much improved this morning with the new plugs and plugged in O2 (even though it'* probably slowly dying now).
I think O2 sensors are more resilient than you think. I ran a full tank of leaded av gas through my car last year, and my O2'* still clickin' along. For some reason or another, I got massive KR when I was running it, but other than that......
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