[MidlifeCrisis]

Originally Posted by Christian.

You should not have to adjust latency for the PE 850s. Start with 3034 for the scaler value and the vehicle should start right up. .......
Christian.
AccessECU Trainer

Christian,

By using the recommended math in the StreetTuner manual, I get 3476 for the PE850s.

This is based on the following assumptions:
Stock inj. flow rate: 550
PE850 flow rate: 850
Stock Inj. Scale Value: 5372

5372 * (550/850) = 3476

Why are you recommending 3034?

Thx, Bruce

[Christian.]

Your stock injector flow rate = 480. I am out of town tuning in TX, I will try to get back to follow up. If I cannot, I sholuld be back in the office on Friday.

[RacerXS]

I am pretty sure the stock STi flow rate is 550.

[MidlifeCrisis]

I can find lots of posts that say the flow rate for the stock injectors in the 2004 STi is 550. Does anyone know of a definitive source for this information?

[04stiguy]

USDM injectors are supposed to be 480's and all other are 550's. The "STI pink" injectors that 2.0L WRX guys upgrade to are the 550's.

[MidlifeCrisis]

Interesting. It appears that Perrin believes our stock injectors are 550s.

....Stock STI injectors flow 550cc of fuel or 52.4lb/hr. Once modified by PERRIN™ your injectors will flow 816cc/min or 77.81 lb/hr. Almost a 50% gain in flow. At the stock injector flow of 550cc your car will max out at 320hp-380hp (Crank HP) At the new PERRIN modified 816cc fuel flow rate your engine now has enough flow for 480hp-550hp. Each fuel injector is precision machined to flow in excess of 816cc. Injector "on time" is not affected by modifying OEM STI injectors.

[04stiguy]

That is interesting.
From the APS site:

"The 2004 model US Specification STI is a unique model in many ways. Just some of those already identified are as follows:

Side feed 480 cc injectors (350 flywheel horsepower at 11.0:1 A/F ration, 100% duty cycle). This is in stark contrast to the International Specification vehicle with its 565 cc top feed units."

[Siegel Racing]

The ecu sort of "thinks" the stockers are 456cc's. Ecutek does a calculation on the 4 digit injector sizing number to arrive at 380 for USDM WRX stock injectors and 456 for USDM STi injectors.

The first step in tuning some cars is to get the injector sizing right. It's similar to doing global MAF scaling. Even on stock injectors and stock air boxes I usually end up anywhere from 440 to 465cc's.

There is discussion about the fact that according to the ecu the injectors keep adding fuel up to 118 to 120%. Many people believe that the ecu may auto scale to 80% or so. That makes the supposed 550 or so USDM STi's the 456. Often the Perrin 816's and even the PE 850's run well from 720 to 760 set in the ecu.

If you have a stock air box, or other well designed intake you may notice that the fuel trims are always positive or negative. If they are always in one direction, you can scale the injectors to get them closer to 0.

SS

[MidlifeCrisis]

OK, then as a starting point, Christian's value of 3034 sounds right. Unfortunately (for baselining one thing at a time) I have a Typhoon installed and with my FMIC I can no longer put the stock airbox back in order to tweak the injector scale value in isolation. Thanks for the input Scott, that helps in building the model in my head about how it all fits together and works.

By the way, are you coming back out to Colorado? For whatever reason we did not hook-up when you were here in August. I visited with Rob about it some. I'd still like you to have a go at my car. -Bruce

[RacerXS]

This is interesting info Scott. Based on what you are saying, just to be clear, we do have 550's but the ECU "thinks" that its more like 450's (approx). And that it would be wise to tune say 816's as 720's as a starting point, then look at the fuel trims to fine tune it.
So, bottom line is we should base all the calculations on what the ECU "thinks" instead of the actual size of the injectors?

Originally Posted by Subaru of Gwinnett

The ecu sort of "thinks" the stockers are 456cc's. Ecutek does a calculation on the 4 digit injector sizing number to arrive at 380 for USDM WRX stock injectors and 456 for USDM STi injectors.

The first step in tuning some cars is to get the injector sizing right. It's similar to doing global MAF scaling. Even on stock injectors and stock air boxes I usually end up anywhere from 440 to 465cc's.

There is discussion about the fact that according to the ecu the injectors keep adding fuel up to 118 to 120%. Many people believe that the ecu may auto scale to 80% or so. That makes the supposed 550 or so USDM STi's the 456. Often the Perrin 816's and even the PE 850's run well from 720 to 760 set in the ecu.

If you have a stock air box, or other well designed intake you may notice that the fuel trims are always positive or negative. If they are always in one direction, you can scale the injectors to get them closer to 0.

SS