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Old 12-05-2012, 12:33 AM   #1
'08WRXRider
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Member#: 276361
Join Date: Mar 2011
Default HELP: What Size Fuel Injs/Pump Should I Run To Reliably Run Stage 2.52 Indefinitely?

My car is a 2008 WRX. I'm preparing to go Stage 2.52 (then, 3.52 down the road) & I can't afford to buy another engine anytime soon should this one sustain damage from lean condition upon upgrading.

So I'll be upgrading to the IHI VF-52 turbo in favor of my stock Mitsubishi TD04. With the other Stage 2 mods (Cobb AP, Invidia Catted DP, AEM CAI & tune) & running California's crappy 91 octane fuel, my research suggests I can expect approximately (I know all dynos read differently & these numbers, at best, ballpark) 275AWHP (320HP-ish at the crank) give or take.

When I do the necessary calculations to determine the appropriately sized fuel injectors for that amount of power, I always come to the conclusion that larger-than-stock injectors are necessary to safely & reliably achieve it. However, some sources suggest that the stock injectors will accomplish my goals at Stage 2.52. This has left me a bit confused & with the upgrade on hold until I can get clear, conclusive answers as to what injectors & pump combo I need to run to reliably run Stage 2.52 indefinitely.

I've been told that the stock fuel injectors on my car are rated at 565cc/min (Is that right?). I've, also, been taught not to push Injector Duty Cycle (IDC) past about 90% for any significant amount of time or the injector doesn't actually go off reliably at the end of its duty cycle. So, when you push the injectors past that point you get, essentially, 100% IDC (on). If these things are true, then it seems to me that upgrading the injectors & fuel pump (to keep up with them) are a must to really reap the benefits of Stage 2(.52) or above & maintain some real level of reliability.

BTW, my calculations are based on: desired engine power of about 320HP, 4 fuel injectors, injector duty cycle of 80 - 85% ('ideal' as recommended, for example, by RC Engineering @ http://www.rceng.com/technical.aspx), Brake Specific Fuel Consumption (BSFC) of 0.65 (for a Gasoline powered, turbocharged engine running boost of 1.3 - 1.4 BAR/18 - 19 PSI).

Based on these calculations & using the stock injectors, I only get 281.5HP at the crank. Well short of the 320HP I'm looking for.

All that considered, what size injectors & pump should I use to achieve my goals & have my engine last?

Thanks for any help/answers to these questions you can provide. I need to know the right way to go here so I can move ahead.
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