The Alchemist

iTrader: (19)

So I data log every time I drive, and have noticed a trend, my passenger side fueling is always 2-3% higher than my driver side.

I'm in closed look, speed density, and I'll notice that my fuel trims are always biased higher for the passenger side. So if the driver's side is -0.5, my passenger could be +1-2%. Sometimes it's more, say +2.0 driver's side, and +6.0% passenger side.

I've switched O2's, and no difference. I've also checked the intake manifold for leaks, and I haven't detected any. I checked for exhaust leaks, and don't see any either. My next step is to swap the injectors left to right to see if possibly I have one injector (or multiple) that aren't flowing as much as the others.

Should I continue checking this or am I simply over thinking this?

HwyStarJoe

Good question... would like to know the answer as well.

thunderstruck507

iTrader: (18)

I've been having a similar problem lately with my truck. But it's about 6% difference most of the time.

I've also been having a long cranking time issue which is intermittent. This leads me to think I might have a slightly leaking injector or something.

The Alchemist

iTrader: (19)

My car sat for a long time over the winter without running, about 7-8 months to be exact, so I'm wondering if maybe I have a partially clogged injector that isn't flowing as much as it should be.

I'm going to swap the injectors left to right and see if the fuel trims change. If it does, then I'll pull them and have them cleaned and flowed, if not, then I'll move onto ignition, maybe I have a slight missfire causing the issue.

The Dragon

iTrader: (6)

Do you mean the injector % or do you mean fuel trim %?

If it's fuel trims, that seems normal to me. Mine have always had a different % from side to side.

I've always surmised that the difference is due to cylinder port variances from driver to passenger side and unequal length headers in F-bodies.

RPM WS6

iTrader: (3)

In my tuning days, I never worried about LTFT differences of less than ~3% or so from bank to bank. This is normal for completely stock cars as well, even when they were brand new and everything was fresh.

The only real concern is that you have one bank in the positive and one in the negative, though the spread is within the range of normalcy. I would work to get them both into the negative range, but I wouldn't concern myself with a spread of 3% or less. If it starts creeping higher, and you're already sure that the O2 sensors are good and there is no vacuum or exhaust leak, then there might be an issue with injector flow and that would be my next step as well.

I wouldn't worry too much about it having sat for 7-8 months, mine does than just about every winter as well. If the fuel was already old at the time of storage and wasn't properly treated, then there might be more cause for concern. But at this point I wouldn't be too worried if there are no other symptoms and the spread doesn't creep further.

The Alchemist

iTrader: (19)

I guess my neroticism comes from being a scientist, and looking for trends in data to predict trouble. When I see that one bank is consistently adding more fuel than the other, it has me looking for a bigger issue.

The one thing is I'm running the new MSD intake, which could have a flow bias to the passenger side, I don't know.

One of these nights I will swap injectors from bank to bank just so I know and can eliminate that as a potential issue.

Before I took the car off the road, it got a full tank of gas with stabilizer in it, so that should have helped, and it was regular e10 gas, not high ethanol stuff.

HwyStarJoe

I've always had the "issue"... even after injector cleaning and flow bench test. They were all equal.
It seems whenever I read about someone noticing this, it's always the passenger side. Never found a definitive answer as to why so I guess I'm not going to worry about it.

The Alchemist

iTrader: (19)

Well, I'm glad I'm not the only one who notices stuff like this.

RPM WS6

iTrader: (3)

It's not so much a matter of "not noticing", but more a matter of what is normal (meaning a 'problem' that can't be fixed) and/or a matter of what is or is not an actual issue, or when it becomes an actual issue.

Such a small split really is meaningless in terms of vehicle operation and even power production (assuming you can keep them both negative thus having consistent WOT fueling - which would have ideally been tuned with more sensitive equipment than the factory O2 sensors.)

I've definitely noticed this with all of my LS1s going back to 1999, sometimes they are equal for a few trim cells and then sometimes the split is between 1-3%. This was true even when brand new and totally stock.

I just don't think it's something to worry about, or that can necessarily be "fixed". Someone above touched on differences in air/exhaust flow characteristics from bank to bank, perhaps also due to exhaust pulses/firing order, combined with the effect of O2 sensor placement within said flow characteristics.

RPM WS6

iTrader: (3)

Just also wanted to add that this should be no problem at all. I do the same thing prior to winter storage every year, and drive the car so rarely that often times I'll still be burning gas from the previous fall well into the following summer. This year I still have half a tank of 93 octane E10 fuel purchased in October of '14, treated with Stabil when new and kept full over the winter, and no problems at all.

With a full tank plus stabilizer, I wouldn't worry about storage related issues unless the car sat for several years or more. 12, even up to as much as 24, months isn't too much to worry about when stored under proper conditions such as described.

HwyStarJoe

True...just look at The Walking Dead...they're still driving cars\trucks that have fuel in them for over 2 years! LOL!!

Sorry...couldn't resist.

I'm not having performance issues that are obvious because of the imbalance. Unmodded (besides exhaust and CAI) it's giving me 372\372 at the wheels.

I haven't recorded a driving session yet this season but I plan to get a bunch of data soon. I did the swap in 2013, drove it for a few months, put Marine grade (blue) StaBil in the tank for the Winter and parked it. Come Spring 2014 when I scheduled its first dyno tune, the owner told me he wouldn't even put it on the dyno until that tank of gas with the StaBil in it was gone.
He said it's unnecessary and he doesn't recommend it. So I don't do that anymore. Given his reputation (with GM no less) and his track record, I'm not going to argue with him. I haven't had an issue leaving 93 in the tank for 6 months. I do run it to operating temps a couple times over the Winter though.

Like I said, I'll get new data as soon as I'm back from vacation and see where this "observation" stands. I still have the new Innovate A\F meter kit to install anyway. Just too lazy to get under there and weld up the bung. Then I'd like to get it back to the dyno because he had to use a tailpipe probe the first time. He was disappointed when I told him I didn't have one already.

RPM WS6

iTrader: (3)

From his perspective as a professional tuner, I can definitely see why he'd want you to have fresh fuel for the tune. This just makes sense as it removes a significant variable since he can't possibly know just how well (or poorly) any given customer has actually stored their car/fuel....regardless of what they might tell him.

For storage periods of <6 months, I would tend to agree that additives in general aren't really critical. Having said that, based on my personal experience of owning and storing seldom driven cars for the last two decades, I disagree with the idea that stabilizers are unnecessary/not-recommended (my experience being with E10 fuels.) I've experienced both ways on various cars, and when you get into storage periods of 12-24 months you can start to notice a difference in how well the engine starts and runs with untreated fuel as compared to stabilized fuel. Over the long term, you'll find more fuel system issues with cars that have been continually subjected to such storage conditions with untreated fuel as compared to those with regularly treated fuel.

So I think it's unwise to give a flat out recommendation against fuel stabilizers across the board for all purposes and situations, though I would agree that fresh fuel is certainly best for the purpose of eliminating variables during a dyno tune.

The Alchemist

iTrader: (19)

I worked for Sunoco as a QC/formulation chemist, so I know plenty about fuel stability over time.... hence why I topped off the tank, and put in stabilizer.

dckmn52

Here's some food for thought.

Individual corrections per cylinder, per RPM with 8 widebands.

and some more


Yes, it is worth major power depending on the application. A cam only LS, maybe not so much. But a max effort competition engine...different story.


This was the entry from last year.

The Alchemist

iTrader: (19)

Thanks for the videos....

I understand that ideally, you would have a wideband in each cylinder and adjust according per cylinder. Unfortunately, I'm on a stock pcm, so that isn't an option. I was just concerned with the fact that the passenger bank appears to be getting more airflow than the driver's side, that's all. That lead me down the path to see if it was real, or if I had another issue such as a biased O2 sensor, an exhaust leak, manifold leak, possibly an injector flow issue, or even a spark issue causing a misfire bias towards the passenger side.

If all those issues are not present, and it's simply an airflow bias, then that's something I can't control without changing intake manifolds, and I'm ok with that.

I went back and looked at logs from last year with my old build, and didn't see a bias towards the passenger side, which is why I started investigating. But I changed nearly everything from the old build to the new build.

Intake manifold went from a ported FAST 90mm to the new MSD atomic air force.

Headers went from the original style QTP's to the Speed engineering 1 7/8" headers.

Heck, how I ran my fuel rail even changed. I used to have it feed in the back of the driver's side, cross over in the front, and dead at the rear of the passenger side, and not it T's at the back of the driver's side, then feeds both rails from the rear.

On top of those changes, I went to a stroked ls3 (416ci), bigger blower, bigger cam... had the heads worked as well. But those things shouldn't have an impact on bank to bank flow.
So I will pressure test my setup to once again make sure I don't have any leaks, then I'll swap injectors, and log again. If nothing changes, then I'm going to just not worry about it.

Realcanuk

I have been trying to figure out this same issue for a long time and have pretty well decided to give up and not let it bother me. My trims are off by 5-10 percent bank to bank and have been since I started tuning and watching these things 3 years ago.
This year everything was changed in my setup......blower, injectors, fuel system, intake, plugs, wires, etc, etc. Surprise............ exact same issue with trims. I am guessing it is some differences from the porting in the heads, or something else I cant control. Since it doesn't cause me any problems, I am just going to try and ignore.

kevin87turbot

iTrader: (2)

I can tell you that the intake manifold is a big factor in Cyl to Cyl and consequently, bank to bank distribution. The best solution is to modify the intake to help distribution. Sometimes that just not an option though. It those cases where you can't modify the intake, it will help to alter individual injector flow. With an aftermarket ECM, it's pretty simple to so. With an OE ECM, you can move the highest flowing injectors to the leanest cylinders. That will certainly help. one of the Stock Eliminator LS1's that I worked on a couple years ago jumped from 530 to 542 hp with just adjusting the individual fuel trims.