Fuel Delivery on a high compression N/A 2UZ

[scribb]

I’m nearing the end of a 2UZ-FE VVTi rebuild, Link ECU install and run-in, and running into some trouble figuring out the fuel delivery.

Here’s the build:

10.5:1 compression, forged internals
Kelford 208-B cams
650CFM Victory injectors (for flex fuel down the road)
Deatschworks 255 Lph fuel pump
Link ECU piggyback (with a VR crank position unity gain buffer to split the signal for the ECM)
**Stock fuel pressure regulator and pulse damper

The motor starts and I've been able to time it, but it runs far too rich, even after dialing my VE table way back; it seems like it's flooding during cranking. The Link also reported strange injector pulse widths—mostly nominal (10-15ms), but with brief spikes up to 20-30ms. I suspect the stock fuel pressure regulator may not be able to regulate the flow from the upgraded pump, and the pressure at the injectors is greater than 3 bar. I have a pressure sensor on the way which I’ll use to confirm this, and add to the Link input to improve injector deadtime accuracy.

In the meantime I'm trying to figure out the right regulator and pulse damper upgrade, assuming that's the problem. It looks like I could retain the stock rails and add an Aeromotive or Radium pulse dampener and regulator to the passenger rail via the port on the front. Is it much better to just upgrade the rails as well?

Any feedback on optimizing the fuel delivery is welcome. Thank you!

 

[ivan129]

Try dialing back your fuel prime to the point where it just won't start. Keep in mind multiple hits of the key will make use of some of the fuel that wasn't used during the previous attemp to start. It might also be a good idea to take a log file from the ECU and send it off to Link for support. Fuel pressure on an NA engine should sit around 3 bar (say 40 - 43psi). If you're running sequential you don't need a fuel pressure dampner as they are primarily used to smoothen out the pressure fluctuations that can occur when running group and or bank injection. Sequential injection should not suffer with varying fuel pressure. Larger volume rails also help 2. Its always a good idea to have a mechanical fuel pressure gauge fitted before the FPR in the fuel rail just to keep your pressure sensor honest. Inj. deadtime is usually mapped against battery voltage, not so much against fuel pressure. Link should have the inj info in one of their libraries, I'll bet. Once you've nailed the above, it'll be time to tweat the post start which again you can start by dialing back to the point where the engine won't keep running. Then start adding lots of 5% till it stays running. All this stuff is temp sensative too. Colder temp starts will want a little more fuel. Good luck.

 

[scribb]

Thank you! Okay, we got a fuel pressure gauge on it, and it's running at 40-41.

I think we’re struggling with the size of the injectors, we’ve got 650cfm on an N/A build, and the pulse width requested by the ECU is approaching the minimum pulse width of the injectors at low load/idle. We gotten it to run for a few minutes and it sounds great, but when we open the throttle it shuts down and is hard to start again.

We'll post a log to the Link forum. Thank you!

 

[ivan129]

650cc injector wil be fine. There are guys here running bigger injectors than that. When you say it shuts down and difficult to start, did you pull plugs and check for an over fueling condition. (wet plugs). Being difficult to start again suggest flooding. Have you checked to make sure you have the injectors configured correctly and flood clear is enabled? Do you have an O2 setup? If so, What lambda or AFR were you reading? Do you have EGTs installed, a reasonable idle at 14.7:1 should give you low to mid 500's C @ idle. Assuming fuel is petrol.