I want to try E85 so I am setting up a tune with TunerCat that I could load when I want to run E85. Going off the thread from LS1Tech about "How to run your LS1 on E85" it states changing the Stoich AFR to 9.765 instead of 14.7 for gas. How is this done using TunerCat?

 

You don't have A/F sensors, you have lamba sensors.

 

I know they are narrow band O2's. I just didn't know if they would read stoich (lambda) with the E85 as well, even though lambda with E85 is around 9.7 vs 14.7 with gas? If so, then I don't need to change anything other than the injector constant (for more fuel) and maybe add 2* of timing at higher RPM's (to compensate for the slower burn of the E85).

BTW, here is the link on LS1Tech.com about converting to E85: http://www.ls1tech.com/forums/showthread.php?t=602091

 

Adjust your injector constant, and then maybe get yourself on the dyno to retune pe. I would also spend a little time in speed density mode to see how things look there and maybe run the logs through ve master.

I've never done it with an lt1 before but I am considering it. That is how I would start.

 

Yeah, for the OBD1 PCM your just going to have to trick it into running rich, since E85 has a different optimal A/F ratio. I've been looking into this as well, since E85 is abudant where I live and much cheaper than premium right now. You will probably also want to look into using a BLM locker (setting it for a richer area than the standard 128) for when it the car goes into closed loop. Unless you plan on just running in open loop all the time, then you can just adjust the tables to the A/F ratio you want.

You'll definitely want to get yourself a wideband O2 as well. Maybe even 2 of them, one for each bank. That will be very important for WOT, definitely don't want to be running too lean and damage the motor.

 

Your o2 sensors just read o2 in the exhaust to determine what stoich is in closed loop. Manipulating the injector constants is just going to get the blm into the area where it can still adjust in closed loop (otherwise it would be at/near the limit of 160 almost constantly). Closed loop will probably be the simpler mode to run in. If you get your injector constants functioning properly you should not have to do much to open loop target a/f values unless some sort of startup issue arises. Because when you change the injector constant, you skew the a/f ratio that its actually targeting by the percentage of error from your incorrect injector constants, and unless he has messed with them they're already fairly rich.

Startup will still be the toughest area to deal with imo. I plan on trying this sometime during this summer if i get time, it should be good for 100+ degree days coming. You will need a very stout fuel system and plenty of spare injector duty cycle to run e85 over gasoline at wot. I have 42lb injectors and a rather large fuel pump I can also raise the fuel pressure if need be to increase capacity further. I only plan on running this during the summer months when its in the 90's. You should also be aware you're going to have about a 35% reduction in mpg if everything runs at stoich. Make sure you're really saving something by doing this. There are also incentives for cars that burn e85 at least 50% of the time (must have reciept proof).

If you go to the dyno if they dont have an alcohol wbo2 sensor, you can use the gas one but they have to set it up to read in "lamda" mode and you can convert from there to a/f ratio and still get good data.

Good luck and let us know how it goes.

 

I just installed the 30# SVO injectors (31.68# @ 43.5 psi) last night. I plan on running an extra PCM just for E85 that I can swap out when I want to run it.

So I should just need to change the injector constant to 27-30% (24.95-24.37#) to allow for the increase need in fuel, then possibly add 2* timing up top (3600+). I'll use that as a starting point then see how that turns out.

 

Your blms will tell you how you're doing while cruising around and at idle. I would probably toss a few more degrees of closed tps advance at it as well for e85. It burns at a similar rate to gas but has a slower light off.

I wouldnt fool around with the wot until I saw how it did for cruise and part throttle first. might add 2* of timing to the table everywhere just for starts though. When you do your wot tuning remember that the pcm adds a degree of timing for every 1000 rpm or so over 3-4000 rpm, this will show on the scanner. I wouldnt get too harry with the timing 1-2 degrees is about all i would go.

After your blms stabilize you can check out what needs to do based on the percent error from 128. This will have more effect on lower airflow areas than higher ones. For the higher ones you will likely have to mess with the maf calibrations at higher airflows. Its going to take you some time to get all the kinks worked out of it.

 

I figure it will take a lot of fine tuning to get it optimized, but to start, changing the injector constants and adding 1-2* timing across the board should be a good start then, right?

 

Last summer I used E85 for a couple of months and I really like it. I changed my 60# injector constant to 39# and bumped the timing a couple of degrees for startup and had planned on changing my PE to get it richer on the top end but it ran so good and my wideband was showing 10.9 at WOT so I just left it. BLM's were also within 5% so it seems pretty easy tune to me. I will be trying it again this summer once it's running again.

 

So basically the stock O2's read stoich (lambda), no matter if its gas or E85?

If this is true, it will make it much easier to get everything dialed in correctly, given that the process to tune would seem similar.

 

O2 sensors pick up O2 in the exhaust stream, when you're lean theres excess O2 in the stream. This is true of any fuel. They just switch back and forth past lamda the way they're set up. They could give a rip what the composition of co and co2 and nox are in the exhaust they just read o2 after combustion to determine how the process is going.

The whole reason of adjusting the injector size is to screw up the calculation and get it nice and close with e85 and to a point where it still has good adjustment of the air/fuel within the limits set in the pcm.

The only thing about the stock o2's is that they are temp sensitive, so that may be a snag, I dont see it causing a huge problem (maybe rich idle especially with lt's and a cam). A wideband would tell the tale on that. Have to set it to display lamda and convert back to a/f with the e85.

 

So logged my drive to work with DataMaster today and with the injector constant set to 24.75 (vs 31.68 on gas for the 30# SVO's) the BLM's stayed in the 130's range for the whole 25 min drive, so I assume that it is still running too lean?

I have it set for 24.75# aiming for 28% more fuel, was this calculation correct?
For adjusting the injector constant for more fuel at 30% more instead of the 28%, should I:
1. Divide the 31.68 by 1.3 = 24.36#
2. Or muliply it by .7 for 22.17#?

 

Do this: average your blms for the trip if they're all in the 130 range, or look at what they generally settled on for the cruise portion of your trip on the highway. Find whatever your blm settled to during cruising avg the values in the log or just eyeball it to see where you're at during cruise and steady state. Lets say its 135 and you picked 126 for a target blm.

Use this equation for the case of them still adding fuel.
2 - (135/126) = 0.92

Now multiply your current injector value by the number you calculated above to get to your target blm.

24.75*.92 = 22.77lb/hr

that should make pretty quick work of your blm's for that area, of couse the caveat is programming has always been a cut and check routine. Thats simply how I would go about trying to get it close. You can always back it off later if its too much. Remember though use YOUR numbers not my example.

I wanna see the log from after you run this change so post it or email it to me.

 

I found the average BLM while crusing was 134.5 so using your equation, I am going to change my injector constant to 23.46 from 24.72. I will log again tonight then email the
results.