Ok, well I've been through a bit of a rollercoaster since my last update. As I was tuning my car before my dyno session for some power pulls, I realized that I was running out of fuel in full boost. It was very discouraging, because I was really looking forward to getting the car on the dyno... Being that I'm in NY, we have very little time before we get a snowstorm and the towns all spread salt on the roads. But after bouncing some ideas off some trusted car colleagues (thanks Andrew), I was able to determine that it's very likely that my one or both of my stock fuel pumps are failing or weak. They are just not able to keep up with my fuel demands in boost and rpms. I took a data log and you can see here in the blue is my fuel pressure and the yellow is the ECU trying to add back fuel. Fuel pressure gets down to around 22psi in full boost, but with the fuel module it ramps up the fuel pressure 1:1 with boost. So, I've definitely got a problem...
One thing that may not be clear from this graph though is Holley saved my engine. If I was running a stock ECU that didn't have the ability to add that much fuel up top in boost, I would likely be shopping for a new short block.
The solution was to contact Carl at Vaporworx and order a pair of upgraded fuel pumps from AEM. He recommended a pair of AEM 320 lph @ 43psi pumps which are a direct swap for the stock 190 lph CTS-V fuel pumps. This should provide me plenty of fuel all the way up to 60+ psi and even have enough flow if/when I run e85. Carl was able to expedite them to me and I was able to swap them out last night.
I'm getting pretty good at this by now... here's how the stock pumps attach inside the bucket.
Pop off the white retaining clip, and the fuel pumps pull right out.
Here you can see the fuel pumps are an exact direct fit for the stockers. Wiring harness and all.
One thing that does need to be swapped over is the little white spacers from the stock pumps. They go on first and I used one of the new o-rings that came with the kit.
Then they just slide right in. The fuel socks are separate, but they all fit inside the bucket nicely. Then it was all back together and ready to go. SOOO glad that I added that fuel door in the trunk. I would have gotten sick of pulling that tank by now...
Then it was time for the moment of truth. Was that really the issue??? I went out to do a little testing and tuning and found out that was exactly my problem! I took the car out for about an hour during my lunchbreak and honed in my in boost fuel VE table. It was way out of wack, but I was able to get a few data points and get it looking wayyy better.
Here I am out mingling and trying to fit in...
I played around with my fueling once I grabbed lunch, then took a log on the way home. Bingo, that's what I wanted to see! Rising fuel pressure along with the boost. Blue is fuel pressure, yellow is CL compensation, and I added green for boost. Fuel pressure stays constant, then rises with boost. Fuel trims still need work as you can see. Too rich as it's pulling 25% fuel, but I'd rather be too rich than too lean up top. Looks like for this run I topped out at just shy of 11psi.
I also got this cool shot when I brought my car to work last week.
I re-scheduled my Dyno appointment for Monday so wish me luck. I think I'm ready now. It's definitely running as strong as ever now.
Cheers,
Ryan