Fuel!
This is the final thing I got done before this past weekend’s track day.
So far the car has been running on V8R’s ’93 octane’ tune. Since we only have 91 at the pump here in CA I have been mixing Torco octane booster to bring it up to ~95, or using 100 from the pump at the track. I’ve been looking forward to changing over to E85 for all the benefits that fuel provides.
As cool as E85 is, the really cool thing is that instead of having to change injectors, do a permanent change over to E85 and a ground-up tune for that fuel, GM already did the hard work for us. Even though the Camaro never sold with a flex fuel feature, some of the other cars that the LFX came in did, and so the engine was designed from the beginning to run E85 and there is a full ethanol tune just laying dormant in the Camaro’s ECU waiting to be turned on. That means smooth driveability and reliability of a factory tune, AND with flex fuel the ECU is always monitoring the ethanol content of the fuel and adjusting the tune accordingly, so in a pinch if you can’t find E85 you can pour regular fuel right in and the car with sort things out on its own.
To enable flex fuel, there is one missing puzzle piece; we need to add a flex fuel sensor in-line with the main fuel supply line. I took this opportunity to replace my stainless fuel line with a pair of fancier – and lighter weight – kevlar braided lines with crimped hose ends. These lines saved a half pound over the stainless line:
The flex fuel sensor is an OEM part number 13577394. You also need a wiring pigtail which can be found all over eBay.
Wire colors on the eBay pigtails may vary, so here are the factory colors at the sensor connector:
pin 1 (Pink/Black): +12v power
pin 2 (Black): Ground to chassis
pin 3 (White): Signal to ECU
1 and 2 are very straightforward. Remember to fuse the power wire.
The signal wire is straightforward but takes a bit of time. This goes directly to the ECU at pin 38 of the X1 connector. Because the Camaro didn’t had a flex sensor, that pin is vacant in the Camaro’s wiring harness. So, you need a factory pin with a wire tail to add to the connector. If you modified your own engine harness and eliminated some wires, you may have a spare to use here, but I didn’t. My overkill approach to this was to buy a second full engine wiring harness from a junk yard and from that I pulled one donor pin and wire from that harness’ ECU connector to use on mine. Now I have a spare but incomplete harness I can scavenge anything from if I need it. If anyone else is doing this same thing and needs an ECU pin/wire to add flex fuel, just shoot me an email and I can pull one from my donor harness for you.
Disassembly of the X1 connector is a little tricky, this youtube vid helped me figure it out:
With sensor installed, all that’s left is to turn on the flex fuel sensor in the ECU. This is done in HPTuners or similar tuning software. Since the software side isn’t my area of expertise, I took the car to Church Automotive Testing in Los Angeles. They’re familiar with tuning these high feature GM motors, and using their dyno would enable us to monitor everything to make sure it was working right before I get out to the race track.
For the dyno tuning, I added a pair of AEM UEGO wideband sensors – one for each bank of the exhaust. This allows us to precisely monitor the air/fuel ratio and make sure everything is running correctly.
As the final step of preparation, I drained the tank and then re-filled it with just 1 gallon of 100 octane; just enough to do a baseline run on before switching to E85. At the dyno, we began with the baseline run on the existing fuel and then poured 5 gallons of E85 in. Then the tuner switched on the flex fuel sensor in the software and ran the engine at low rpm waiting for the new fuel to work its way down the line until we began to see the ethanol content rising on the sensor’s signal. Once there was a good 75% ethanol at the sensor he did a few more pulls which showed an immediate jump in power. He made a couple minor adjustments to fuel and timing which pulled a couple more hp out of it and improved the low-end torque. More timing beyond that didn’t make any more power so we backed it down to the previous timing values and called it great. The good news there is that the E85 tune from GM was already 98% there to max power, we only made tiny refinements. If I was doing it again I’d be confident in just switching on the flex fuel sensor and pouring E85 in the tank. After verifying that the sensor is operating correctly and reading the ethanol, it’s good to go drive – no need for dyno tuning or air/fuel ratio monitoring.
So what did we gain? From baseline to final run on E85, +18 whp and +20 ft-lbs at the wheels. And E85 costs ~$2.20 per gallon compared to $9/gal for 100. Works for me.