LTFT's with E85 and Cooler Temps

[sallyspeed3]

Hey guys. I'm tuned for E85 and everything has been great but now that it's getting colder the car isn't running as good. WOT AFR targets are lean and my LTFT's have gone positive. I know that once it gets colder they switch to E70, has that already happened and maybe why I'm seeing this difference? Also, could it just be the colder air?

Right now my fuel gravity is .7520 and Scalar is set to 1.11

I put 4 gallons of Eth along with 8 gallons of 93 for every fill up. Are my settings off? I've looked at several threads about this but can't find a definitive answer on what to do.

[Sweetsandman]

Not that it really matters...but back when I had my Cobalt on E85...the fuel trims would go crazy in the winter. Anything from +12 to -12...could never seem to get it consistent no matter what...that was when I had Vince at Trifecta tuning it to. Ran fine with no knock or any lean/rich spikes...but would occasionally take 2 tries to start up in the morning.

I Tapped that

[Enki]

A reduction in E content in the fuel leads to a richening of the fueling; all else being equal.
I'd start checking for leaks/cracks/etc.

[sallyspeed3]

Well for comparison, I switched to my prior map which was tuned for 93, I'd like to add that this map was made during the winter months when it was cold. Filled it up with 93 and drove for a while that way. Trims stayed within spec which makes me think there aren't any leaks. At about 1/4 tank I put in 4 gallons of E85. At that point I started to notice the fuel trims going back up. Since then I've switched back to the E85 map just so that I'm not effing anything up. I guess I should have mentioned that info in the OP.

[Enki]

Are your maps scalar adjusted or maf adjusted for the E content?

[sallyspeed3]

Scalar is set to 1.11

[Enki]

And you changed the specific gravity too right?

[Boost_creep]

I would try .754, and a 1.12 scaler.
I think this closer matches your mix, and might help.

That is of course, if you are absolutely positive that you have no boost/vacuum leaks. Tuning around a mechanical issue will only cause much more aggrevation down the road

[sallyspeed3]

yeah, .752

[Enki]

If your E map scalar/FSG numbers are off, changes in airflow density could conceivably alter trims. You sure those numbers are right for the blend of E you're on right now?

[sallyspeed3]

I'll try that and see what happens. Obviously if the trims keep going up there is a leak, but as stated on the regular 93 map they stayed the same for 50 miles. thanks.

Originally Posted by Boost_creep I would try .754, and a 1.12 scaler. I think this closer matches your mix, and might help. That is of course, if you are absolutely positive that you have no boost/vacuum leaks. Tuning around a mechanical issue will only cause much more aggrevation down the road

[Boost_creep]

50 miles generally is not really enough time to fully settle.
A tankful is more like it. Lol.

[silvapain]

Winter blend. E85 is usually more like E70 in the winter, as too much Ethanol leads to cold start issues.

Conversely, pump gas has a higher Ethanol content in winter to reduce emissions.


Tapadatass

[ms3blackmica]

funny that you posted this up...

after leaving gerry's house the other night, i noticed my trims at idle were about +6% when i had them dialed in at about 0.8%

I did nothing to the car. Gotta check for leaks now !!

But i am seriously considering testing my local 93 to see if the ethanol content is higher now.

[phate]

In the winter, ethanol content is decreased in some places. This will shift your actual fueling RICHER, meaning your trims and AFR's have gone the wrong way to consider it a tuning issue. Definitely sounds like a leak to me.

Edit: OR, you put in too much e85 at your last fillup Since you're gas tune didn't change, this is a likely culprit.

[Enki]

Trims at idle are out the window. I've long since given up trying to get them perfect on ANY fuel, as it seems it will adjust based on ambient temp, engine coolant temp and boost temps (yes, even at idle).

[sallyspeed3]

All good points. I think I need to get a leak test done just for peice of mind. Would a place like midas be able to do something like that? No good "race shops" around here

[silvapain]

Originally Posted by phate In the winter, ethanol content is decreased in some places. This will shift your actual fueling RICHER, meaning your trims and AFR's have gone the wrong way to consider it a tuning issue. Definitely sounds like a leak to me. Edit: OR, you put in too much e85 at your last fillup Since you're gas tune didn't change, this is a likely culprit.

Whoops. Read OP backwards.

[sallyspeed3]

Going to try and get under the hood tonight and check for leaks. Would this leak be pre-turbo? I was always told post-turbo leaks would cause a rich condition since air is escaping, not being drawn in. Someone please correct me if I'm wrong.

[Enki]

That sounds about right, yeah; somewhere between the MAF and the turbo. If any portion of your intake is made from silicone, you should probably pull it completely out and check for tears/rubbing; a while back my CPE inlet had some issues which I was able to easily patch with RTV.

[sallyspeed3]

Okay, so a month later I'm finally going to get my car checked out. Shop I'm taking it to has a "smoke machine" which after doing some research seems like a good way to detect any leaks in my system.

I've also been getting the infamous P0401 code for my EGR over the last couple of months. I know sometimes the EGR can get stuck open, could that be causing positive fuel trims?

[ms3blackmica]

Originally Posted by sallyspeed3 Okay, so a month later I'm finally going to get my car checked out. Shop I'm taking it to has a "smoke machine" which after doing some research seems like a good way to detect any leaks in my system. I've also been getting the infamous P0401 code for my EGR over the last couple of months. I know sometimes the EGR can get stuck open, could that be causing positive fuel trims?

When you first started seeing this issue, my fuel trims went positive right around the same time. I boost leaked test my car and no leaks. Air tight.

I do believe we are now running on a winter blend of fuel. I remember years ago winter blend fuels had oxygen based compounds in the fuel to help with combustion in the winter such as methyl tertiary butyl ether (MTBE) and Ethyl tertiary butyl ether (ETBE) which bring oxygen into the combustion chamber through the fuel, however I believe it is no longer used..I am not certain what is used currently for winter blends of fuel but it has thrown my trims positive by a significant amount. I thought it was funny that we both live in North Jersey and saw the same symptons at the same time.

Regardless I have boost leak tested my car and my entire system holds pressure. I re-did my MAF calibration and all is well (although technically it was not necessary, I think i just had ADD lol). But i am certain I was not tuning aroud any leaks.

[sallyspeed3]

Originally Posted by ms3blackmica When you first started seeing this issue, my fuel trims went positive right around the same time. I boost leaked test my car and no leaks. Air tight. I do believe we are now running on a winter blend of fuel. I remember years ago winter blend fuels had oxygen based compounds in the fuel to help with combustion in the winter such as methyl tertiary butyl ether (MTBE) and Ethyl tertiary butyl ether (ETBE) which bring oxygen into the combustion chamber through the fuel, however I believe it is no longer used..I am not certain what is used currently for winter blends of fuel but it has thrown my trims positive by a significant amount. I thought it was funny that we both live in North Jersey and saw the same symptons at the same time. Regardless I have boost leak tested my car and my entire system holds pressure. I re-did my MAF calibration and all is well (although technically it was not necessary, I think i just had ADD lol). But i am certain I was not tuning aroud any leaks.

Well that makes me feel better. I really don't think I have a leak either because other than positive LTFT's I have no symptoms of a leak, but I'm still going to get it checked out just for peace of mind. I also want them to check for an exhaust leak where the downpipe connects to the turbo. If all checks out I'll just readjust my MAF calib. and save it is my "winter map" and hope come spring time that things go back to normal.

Still a question for anyone out there, could the infamous P0401 have anything to do with my problem?

[ms3blackmica]

Originally Posted by sallyspeed3 Well that makes me feel better. I really don't think I have a leak either because other than positive LTFT's I have no symptoms of a leak, but I'm still going to get it checked out just for peace of mind. I also want them to check for an exhaust leak where the downpipe connects to the turbo. If all checks out I'll just readjust my MAF calib. and save it is my "winter map" and hope come spring time that things go back to normal. Still a question for anyone out there, could the infamous P0401 have anything to do with my problem?

I'm really not too sure about the EGR issue making an effect. I have my EGR blocked off so I really don't know.

Deff just make sure you don't have any leaks both on the intake side and the exhaust side (before the primary 02 sensor). If either side has a leak it will throw it off.

Fuel trims will always be changing throughout the year, but for me, it was all of a sudden +7-8% right after getting a fresh tank of gas so I knew something was up

[sallyspeed3]

Well Midas smoked my intake and inter cooler pipes. Found a leak at the bpv and a leak at the coupler coming off my fmic. Going to disconnect the battery to allow ecu to reset and see what happens. Hopefully they'll come back down.

[ms3blackmica]

Originally Posted by sallyspeed3 Well Midas smoked my intake and inter cooler pipes. Found a leak at the bpv and a leak at the coupler coming off my fmic. Going to disconnect the battery to allow ecu to reset and see what happens. Hopefully they'll come back down.

Finding a leak is always great to hear (Sounds weird right?)

Because now you can fix it !

[sallyspeed3]

Well fuel trims are better while driving. I'm now at 9,7, and 5 opposed to 14,12, and 7 from before. But still 19 at idle so obviously they missed something. Car smells like shit when it idles. I told them to check everything before and after the turbo plus exhaust leaks. I have a feeling they found those leaks and then called it quits. Will be taking it back, so aggravating.

[sallyspeed3]

Okay, Im hoping some of the guru's on here can start chiming in here cause now I'm freaking stumped. Please read this and see if you can figure this shit out.

Unplugged the battery yesterday before a long drive to east rutherford and back, between that and driving my wife to work tonight I put about 150 miles on the odometer. Plenty of mileage for things to settle. During that time my trims did not change from what I posted last other than the idle trims staying at about +15.

I knew before the trip that I needed some more e85 so I brought along my containers and filled them up at Power Gas in east orange. Figured while I was there I should put some in the tank as well but I wasn't on empty. I put in 2 gallons of E85 and 4 gallons of regular. For reference when my gas light comes on I put in 4 gallons of E85 and 8 gallons of regular, so the ratio is the same.

Not even 1 minute down the road I noticed my trims starting to come back down. By the time I got home my LTFT's are close to zero except for one breakpoint that barely gets used so it's still high. Idle trims are also down to +7 and staying steady. Does this mean that I've been getting bad gas for the last 2 months? WTF?

[phate]

Try to reproduce it by going back to the original station next time. If you get consistent results, it could definitely be the fuel source.

But, when crazy things happen after a fillup, I usually think evap pump or purge valve going bad.

[silvapain]

Buy an Ethanol test kit and check the fuel at the station you usually use.


Tapadatass

[fooqr]

I actually had something very similar just happen to me. Got E85 from a different gas station than I usually do, and it affected my fuel trims. I dunno whether I've been getting bad gas all along, or whether one station is on summer E85 while the other has switched over to the winter blend.

[sallyspeed3]

Originally Posted by phate Try to reproduce it by going back to the original station next time. If you get consistent results, it could definitely be the fuel source. But, when crazy things happen after a fillup, I usually think evap pump or purge valve going bad.

I always get my E85 from Power Gas, so it's not their gas I'm questioning. I'm thinking it's the gas stations around here that are "bad". But yeah, I guess I'll know for sure if when I fill up around my area my trims start to go positive. And I actually just replaced the purge valve a few months ago just for shits.

Originally Posted by silvapain Buy an Ethanol test kit and check the fuel at the station you usually use.

will do, thanks. If it is in fact due to winter blends would lowering my E85 content by a gallon or two during the winter help?

[silvapain]

If station variance or winter/summer blends are affecting your car, you can offset this by modifying your E85/pump gas filling ratio, based on testing the Ethanol content in the E85.


Tapadatass