Greetings,
So, after much debate and sitting on the fence I finally decided to give E85 a shot... Until recently it has not been available in my area but that has changed recently. Anyway, after a lot of inner debate I finally decided to give it a shot. I figured, if I like the results it will help tide me over until Nameless releases the Tri-Y long tubes...
This is not a thread to discuss the pro's and con's of ethanol, there are plenty of those around. It Is a thread to show BRZedit users how to do the "conversion" and to discuss related tuning issues.
What needs doing
Esentially, you will need to do two things:
- scale both sets of injectors for the additional fuel required with running ethanol fuels
- Tune the ignition timing for MBT
Additional Fuel Requirements
As i was getting ready to do the conversion i put together a little spreadsheet to help me figure out the additional fueling requirements of various ethanol blends. After some fine tuning, it turns out these numbers are VERY close and should prove helpful.
You will want to pickup an
ethanol content test kit so you can test the blend at your local stations. My local station turned out to be E80, i assume this will get stronger as we get deeper into the summer.
So, what you need to do is figure out how many gallons of fuel you have left at a given fuel gauge reading then look up the splash blend on the chart. I fugured out where the point was that I would have 2 gallons of E10 left in the tank. I then when and picked up three 5 gallon gas cans and headed to my local E85 pump. I put 4 gallons in each can and headed home with 12 gallons of E85. I then drove around till i got to the 2 gallons left point.
Scale the injectors
I want to give a HUGE thank you to Tony (Toni?) over at @
FA20Club.com for helping me figure out which map controls the scaling of the direct injectors. There are several suspects but it turns out
GDI Pressure Multiplier A & B are the tables we will use to scale the DI's. The Port injectors are scaled using
Injector Flow Scaling.
On to the process:
- Open up GDI Pressure Multiplier A
- From the Maps menu select Edit, Select All
- From the maps menu, select Data Mul...
- In the multiplier % box enter the additional fuel required (131 for E80, 127 for E70 etc))
- From the maps menu, select Edit, Select all, copy whole map
- Selecte GDI Pressure Multiplier B
- From the maps menu, select edit, paste
- Select Injector Flow Scaling
- From the maps menu select, Data Mul...
- Enter (100 - (0.85 * additional fuel)) For E85 this would be 72 for E70 this would be 77
- Save the map
So, with the DI's we scale up the flow rate, with the port injectors, we scale down the size to increase the pulse width. My testing showed to keep things balanced, you needed 100% change on the DI's and about 85% change on the Ports.
Go ahead and add a degree of timing globally for mixes over E70. I added 1 up to 2000 rpm and 40 load, then 2 from 2000 / 40 load and up.
Here is a screen shot of stock scaling vs E80 scaling:
Tip-In Enrichment
As many of us are noticing, the factory tip-in enrichment settings leave something to be desired... sometimes resulting in tip-in knock retard. This is an optional step, but one i have decided to use, scaling the tip-in tables up to account for the additional fuel requirements.
- Open Throttle Delta Fuel Comp A
- From the map menu, select Edit, Select All
- From the maps menu, select Data Mul...
- Enter the additional required fuel (133 for E85, 127 for E70)
- From the maps menu, select Edit, Copy Whole Map
- Open Throttle Delta Fule Comp B
- From the maps menu, Select Edit, Paste
I have also added an additional 10% from 0.00 to 5.86% delta. This will probably need some fine tuning for each setup.
Initial Tuning
I did several iterations of maps based on various mix ratios from adding 4 gallons E80 at a time to the 2 gallons of E10 i had in the tank. It does take a minute for the Ethanol blend to work it's way through the system so you have the option of pulling up the logger, starting the car on the pump gas map and watching the fuel trims until they start to swing heavily in the positive direction... at that point, shut it down, flash the E map, start it back up and wait for the trims to settle down.
You will want to watch the injection mode. 1 is port only, 2 is DI only, 3 is combined. You can free rev the engine and hold it at various modes to see how the rough scaling is working out. Based on all my testing, the numbers i posted should be very close. You will probably need to adjust the maf scaling a little bit at idle, once off idle the numbers should be bang on.
Take it for a drive, log your trims and your injection mode. Adjust as needed. You should now be ready to hit the dyno
Cold Start Tuning
Will update as it starts to get cold, There are several tables to adjust from cranking enrichment to warm-up enrichment.
MBT tuning
You can either burn through your tank of diluted E mix and fill up again or head on to the dyno, thats up to you. I waited until the 2nd tank.
Once on the dyno, dial in your AFR's. I tired several variations between low 12's (12.1) and high 12's (12.9) and did not find much difference at all so i settled on 12.6 for the first tune.
Next up is timing. Hopefully you are starting from your pump gas tune with a good timing map. You will add timing 1 degree at a time and make a pull. Once you reach the point where you stop seeing noticeable gains at a given rpm, you stop adding timing there, and back it off a little bit. Work your way up the rpm range, You will not be able to add much timing bellow 4,000 or so if you were tuned on 93 octane, but it will take a lot more timing up top. Keep working your way up, watching for knock retard and or knock correction. As you add timing you may need to add a little fuel to keep AFR's where you want them. When your done with timing, do a couple of back to back pulls to make sure there is no knock retard.
Back off the tune a degree or so (depends on your degree of confidence) and flash your final map.
attached is the plot my my best pump gas tune vs my first E85 tune. Same mods (FA20club.com CAI, Nameless catted Front / Over pipe, Nameless axle back), same dyno, 2 weeks apart.