Opinions on these methods to lower knock and IDC's...

[O_ROD]

Put the AFPR in today and set it to 50psi base and seems like success! I'm now running 16psi with zero signs of knock and timing advanced 20 degrees throughout the pull. My one O2 is stuck at 0.01 volts, the other showed a max of .93v. I think the cold air might be helping me out most of all though, intake temps were only 68F. IDC's at 108%. No more mid throttle knock either.

So far so good, we'll see what happens in the warmer weather.

[dpartinvr4]

YOur idc's are still high, and it shows in your timming...

[O_ROD]

Yeah, still trying to figure out why... Haven't found a timing light to check my timing.

[dpartinvr4]

standard timing advance is 30degrees, so 20 is retarded timing. you want your idc's at 82.5%

[O_ROD]

I was hoping to see closer to those numbers with raised fuel pressure, but no luck. It didn't seem to make that much of a difference other than seeing no knock.

Hotwired walbro, 50psi of fuel pressure and a new fuel filter, should be plenty for what I need... I guess that would just leaves my injectors as the possible problem.

[dpartinvr4]

do you have a wideband? what are you afr's? and what are your fuel trims?

[DG]

My 02's were reading .94v and .95v.

That means nothing.

Seriously guys, reading O2 sensor voltages off narrowband O2 sensors was discredited in like 1998. Temperature sensitivity plus a number of other factors means that 0.94V could be anything from 14.5:1 to 9:1. You categorically, absolutely, positively, Hey Rube! no-foolin' CANNOT use a narrowband O2 sensor to detemine anything other than "rich" or "lean" with the switching point being 14.7:1. That's it. So stop it already, OK?

If you want to know AFR, you need a wideband O2 sensor and the appropriate controller. Full stop.

In the meantime, pull the plugs and have a look and see what they tell you.

I'm not super familliar with the control strategy of the 3S computer, but it is fairly common for knock to trigger both retarded timing and increased fueling. If the car really is knocking, increasing fuel pressure may throw enough fuel into the motor to stop the knock and get out of the knock control extra fuel. In that case, I'd expect to see increased fuel pressure reduce IDC.

But the other thing to consider is that the 3S has no concept of "boost" in the ECU. Instead, it uses "engine load" as a function of percent of MAF flow. When the ECU was mapped, the OEM programmers know which RPM/Load cells correspond to what boost values, and they change the programming strategy accordingly.

It is not unusual for cells in the upper load range to be programmed with maximum injector pulse width. The OEM knows that these cells will never be seen during normal operation, so they represent an "overboost" condition. That means something is wrong, so the strategy is to open up all the taps in an attempt to preserve the engine.

If you improve airflow via turning up the boost, less restrictive exhaust, etc you start seeing these load values during normal operation - but the computer doesn't know this is "normal" - so it dumps fuel in. And changing fuel pressure won't change that.

DG

[RealMcCoy]

I was hoping to see closer to those numbers with raised fuel pressure, but no luck. It didn't seem to make that much of a difference other than seeing no knock.

Hotwired walbro, 50psi of fuel pressure and a new fuel filter, should be plenty for what I need... I guess that would just leaves my injectors as the possible problem.

Why do you think that increased fuel pressure will reduce IDCs?

Steve

Pretty sad thread when Steve has to point out the obvious....

[dpartinvr4]

Tech: My take on injectors vs. timing control vs. HP with the stock ECU - 3000GT/Stealth International Message Center thats how i know it will.

[RealMcCoy]

Tech: My take on injectors vs. timing control vs. HP with the stock ECU - 3000GT/Stealth International Message Center thats how i know it will.

I've probably read that thread 200 times... Show me ANYWHERE in that thread Trevor made that claim.

Increasing fuel pressure increases the flow of the injector, which in turn ALLOWS you to make adjustments with your A/F controller... Would you put larger injectors in without fuel control? What do you think would happen then? Would the IDC's go down?