E85 idle issues

[Super73]

So I have decided to switch to E85 since the new combo has a bit more compression in it. Here is the skinny.

418ci motor
13-1 compression
TSP 237 heads
254/260 cam
Super Vic Intake
4150 plate
4150 to dominator adapter
Dominator TB
Edelbrock 1 3/4 stepped to 1 7/8 headers (will swap out at some point)


Prior to this new combo, I had AFR 225's (11-1cr) and a 245/260 cam in it. I have always run that combo with the IAC hole plugged. Cold start always required 2% throttle via turning the idle screw on the TB. As it warmed up I was able to bring it down to 0% TPS.


I fired it up on 91 on Friday and Saturday just to check for leaks etc. I did my idle screw trick and no issues.

I switched to E85, added roughly 40% fuel and fired it. It would not hold idle and I spent 30-60 minutes in nuetral adjusting AFR getting it close to stoich (14.7). I know, I am still tuning with the gas equation and will eventually switch over to Lambda.

After getting the AFR closer to stoich, it will run on it's own (even though it is a bit rich with no throttle and a bit lean with throttle, still needs work). But I can not get it to idle down from almost 1,900rpm.

I have check for vacum leaks. I plugged the factory fitting on the valley cover going to the throttle body spacer to help with crank case pressure just to see if I was getting too much air through it. Again, the IAC hole is plugged so no leak there.


Attached is my tune, .cfg and a short log.


Any help, ideas, info would be great.

[98Camarod]

Are you able to change your wb to e85? I'd change your stoich to whatever blend of e85 you have. Probably around 9.7 for stoich. Did you try backing down the throttle to actual 0%?

[Super73]

I wil adjust the wideband soon and tune off lambda in the near future.

I had to leave the house, but decided to look for a vacum leak on the intake. Nothing. Then I decided to fire it and put my hand over the primaries of the TB. It pulled a ton of vacum against my hand. So I double checked the screw. 0% does not seem to be right. Backed it out even further and truck dies as the rpm drops. Might need to recalibrate the tps. I will try that tomorrow.

[vltrb-0]

i think 98camarod means change your stoich value in your tune, adding 40% to your fuel tables is not the way to add more fuel

depending how you swap fuels also consider contamination with gas

[Super73]

Not sure that I will be running anything but e85, drained the tank completely before filling it with e85.

Being I run a 1bar sd tune with the o2's deleted, I see no issue tuning by adjusting the ve table right now. I can try to change the stoich value later, just trying to get it close.

[Atomic]

I recommend changing your VE table back to what it was when you run it on gas, then only change the stoich afr value to e85.

[vltrb-0]

Not sure that I will be running anything but e85, drained the tank completely before filling it with e85.

Being I run a 1bar sd tune with the o2's deleted, I see no issue tuning by adjusting the ve table right now. I can try to change the stoich value later, just trying to get it close.

if you had a good tune on gas fuel, then switching your VE back to gas setup and changing your stoich value to suit E85 will result in a better basis to tune

[Super73]

But I didn't have a perfect tune for gas on the new head/cam combo. AFR was not dialed. Just fired it up, it idled, just not perfect.

[vltrb-0]

But I didn't have a perfect tune for gas on the new head/cam combo. AFR was not dialed. Just fired it up, it idled, just not perfect.

fair enough

still seems like a better place to start then not idling

each to their own but if you want to change fuels in the future to a race fuel all you have to do is change the AFR's and do fine tuning again as you will have dialed in your VE's

[98Camarod]

Or you can make a thread to ask for help and not take the advice of others that posted. What's the point of the thread then? It takes maybe 2 mins to swap the ve back, change the stoich value, and write the calibration. You'll be in a much better spot then where you are now, AFU.

[Super73]

Regardless of what method I use to reach stoich, stoich is stoich and that is not the underlining issue. I am not asking how I can get to stoich. I am asking for help on a high idle issue after swaping the fuel.


What you guys aren't understanding is it idled, sure, but pretty lean at 16-1afr with 91 in it and the gas tune. The new heads and cam really through the tune for a loop from the old set up.

It would take just as much time to swap back to the gas tune, change the stoich reading and adjust for stoich on the e85. Right now as it sits, it is a lot closer to e85/stoich than it would be going back to the other way.


I appreciate peoples help, I really do. I am happy to listen to the reason for going back to the gas tune, changing to 9.7 vs the way I have done it adding to the VE. But I think that is for another thread.

[carlrx7]

I run E85 in my car. when i want to run 93 for any long distant trips, i simply change stioch from 9.765 to 14.13, then pull 5 degrees of timing using the PE spark table.

boom, done.

-Carl

[Super73]

So lets say i change the stoich setting and go from there.

Will the comanded afr change?
If so, would that not require me to adjust how hptuners logs the new commanded afr and the afr error that I currently use?
If I need to, what needs to be changed in the afr error string?

I like being able to cut and paste the ve table from the tune, afr error from the scanner in to a spreadsheet that I made. Copy it from the sheet back to the tuner and rinse/repeat till afr is in line.

I understand my wideband will still read 14.7 is stoich, but if commanded afr is 9.7 and hptuners is wanting to see 14.7, my afr error will be skewed.

I see the advantages, ie 3/4 tank 91 and 1/4 e85, adjust stoich requirement and done. Being in CA, I don't think I want to drive the truck on straight 91.



That still doesn't address the high idle issue that everyone is looking past. I will try resetting the tps and make sure the tb is completely closed. I hope that it was that simple of an over site.

[tommytuner]

the main reason to adjust stoich and not cheat the VE tables is because all of the pcm's math is based on the actual stoich of the fuel. 14.7 gas is equal to about 9.7 E85, so a "close" gas tune would result in an equally "close" E85 tune simply by changing stoich. leaving stoich set for gas and "cheating" VE will leave you lying about PE and spark as well.....

my question is, when you fired it on gas, did it idle at 1900-or were you able to get a decent idle?

[Super73]

It idled lean at 1,200ish on 91 and gas tune.


I took in to account the change wit hthe PE multiplyer and adjusted the EQ ratio to 1.24 from 1.18.


Can anyone tell me how to adjust AFR Error if Stoich is changed? I don't see how it could work properly is the WB is reporting 14.7 AFR to HP tuners and the PCM is commanding 9.7.

[Super73]

The good new is the throttle position was not closed all the way and it will drop in rpm now. AFR is much better. I am still cheating the VE..

Bad news is for some reason TQ Management is now wanting to pull timing even though it should be completely disabled. It's pulling about 20*.. Not too sure why or how.

Most recent files attached.

[Atomic]

for your error function, just use the stoich you used in the tune instead of 14.7 or whatever you used now.

[vltrb-0]

It idled lean at 1,200ish on 91 and gas tune.


I took in to account the change wit hthe PE multiplyer and adjusted the EQ ratio to 1.24 from 1.18.


Can anyone tell me how to adjust AFR Error if Stoich is changed? I don't see how it could work properly is the WB is reporting 14.7 AFR to HP tuners and the PCM is commanding 9.7.

the wideband doesn't report 14.7:1 to hp tuners it reports a voltage, 0-5volts

you can use that to display what ever you like with your equations

your wideband reads in lambda and has a multiplier put on it, in the case of gas if lambda = 1, then 1 x 14.7 = 14.7afr

your better off setting your car up for lambda, run off lambda error then no matter what fuel you run all you have to do is change the stoich value and make small adjustments

you won't have to change any afr error calcs either, have a read on the forum there is an abundance of information on here

[Russ K]

You need to change your Stoich to 9.765. Also multiply your VE table by .665 to get your AFR close.

Then to correct the wide band, set up a custom AFR pid; [AUX.20005]*.665. You will need to set up a custom AFR Error pid.

Russ Kemp