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Not sure what to think. Replaced the wide band sensor in the car as it was dead from race gas. Drove from Fort Wayne to Indianapolis yesterday and back for Street Car Takeover (didn't end up running because it became apparent my meth pump took a dump).
On the drive down, wide band was running around 13.8-14.2 while holding throttle cruising down the highway. If I lifted my foot off the gas it would dump down to 10.0, then recover when I got back on the gas to maintain speed. About 2/3 of the way to Indy, it LITERALLY flipped. It started dumping to 10.0 whenever I was holding cruising throttle, and when I'd lift on the throttle it would come up to 13.8-14.2 range.
The wide band is hooked into the left side of the exhaust, and the rich issue was confirmed by simply looking at my tail pipes as seen below.
On the way home, the EXACT same thing happened. When I pulled into my garage it was tearing my eyes up from the fumes. I'm not sure where to begin with this. I'm going to take the car for a drive today and monitor the narrow band O2's just to see if I can get a feel for what's happening. The car has an open loop speed density tune on it, so I'm wondering if this is some kind of vacuum leak presenting itself as the FAST 102 has been suspect of leaking. Just looking for some pointers or anything if someone has seen something like this before.
The only thing I found that was off with a quick inspection while in Indy was that the right side of my exhaust, the on the car for 4 years but only seen 7000 miles old LG Big 3 Exhaust has begun puking fiberglass out the back. I have several big wads I pulled out, but I don't believe it's related to this issue at all.
Any reason why you don't just put it in closed loop and let the NB O2's take care of part throttle fueling? I've never really understood leaving them in open loop permanently unless you just like trying to keep fueling right all the time on your own
Post a log that includes both front O2 sensor readings, that will at least give some idea of what's going on.
Bought it back with the tune like it is. They said they were having trouble keeping the fuel trims from splitting to polar opposite ends of the spectrum under high boost, so they shut off closed loop and tuned it OLSD. I was suspect of an internal leak in the FAST 102 but after talking with the interim owner he said that he spoke with FAST and was recommended to disassemble the manifold and use a sealer on the runners to seal it all up which he did.
I wish I could post a log but I don't have the stuff to do it. I know I was using HP Tuners recently, but that was just a basic program download on my desktop to look at a log file on my buddies car. Best I could do is use my Snap On scanner and do a video of the PIDS for the oxygen sensors.
I haven't ruled out an exhaust leak being the culprit at this point because I had noticed while cruising down the highway I was picking up a faint tick from around the bellhousing area.
Fuel trims shouldn't be active while in boost.. so that explanation you were given doesn't make much sense. At most they'd be a positive value carried into boost from just prior.
Those intakes are known for leaking so that's def. a place to start. Exhaust leak will do weird things to O2 readings also though, so that's something else to take a look at too
Honestly overall I think a competent tuner needs to spend a little time with it and truly figure out what's going on. I don't know many details on your setup but unless it's just an absurd cam, there's no reason that I can think of to not leave it in closed loop.
If you were local I'd take a look at it for you but I'm probably a bit too far away for that
Definitely appreciate the offer, but just a tad out of the local range, lol. I know the tune needs going over and polishing. It's solid enough as it's the tune the car made the 202 MPH pass at Texas with it and was stable. Just needs some serious refinement. I have a local guy, I'm just trying to tidy up any little things so I can take him a car that's 100% tunable without issue.
It's actually a baby cam in the car. LPE GT2-3 cam, which is essentially an aggressively ramped LS6 cam. Shouldn't be any overlap/reversion issues at all from it, but the car idles a lot harder than it should (in terms of overall sound/lumpiness) which is to me, just another indicator that the tune needs some serious driveability tuning work done.
So short of compression issues (which I doubt), I guess the two main things to look at/for would be manifold leaking or exhaust leak.
Only other thought I had was that the FAST fuel rails are hooked in series with the drivers side rail first in the series, then passenger, then regulator. Was thinking maybe that could have something to do with it, and was thinking of switching them to run in parallel since the regulator has dual in ports on it.
Yeah, that should be fine to tune closed loop then... I'd def. spend some time on checking out intake/exhaust leaks before going to a tuner and wasting time/money. Hopefully those two things help make the tuners job easy
That's the goal. I personally find it embarrassing to take a car to a tuner and then it's "you need to fix this, and this, and that, before I can finish tuning it." I refuse to do it that way, lol.
Looks to me like the issue is with your fueling setup. Being that it's running open loop exhaust leak issues shouldn't be causing such a difference side to side. If you put it in closed loop you are going to "fix" it by having different fuel trims side to side but that is just going to be a band aid to what appears to be differences in fuel pressure between the rails.
There "shouldn't" be any pressure difference between the rails. Fuel comes in at the back of the drivers rail, crosses over at the fronts, out the back of the passenger, to the regulator. Just a normal series setup.
I will say this is something new, or something that only presents itself after an extended amount of time. Since I've gotten the car back about a year ago, there hasn't been any period of extended driving like it had last weekend. Up until that point the exhaust tips had never looked different like that, only after driving for 1.5+ hours. Car has seen a bit of around town and some full throttle pulls and everything has been normal.
Looks to me like the issue is with your fueling setup. Being that it's running open loop exhaust leak issues shouldn't be causing such a difference side to side. If you put it in closed loop you are going to "fix" it by having different fuel trims side to side but that is just going to be a band aid to what appears to be differences in fuel pressure between the rails.
But if you put it in CL you could at least prove or disprove the fueling differences between the banks. Right now you're guessing.
There are some stupid high HP cars that run fuel rails in series--I highly doubt that's the problem. Maybe something wrong with a hose or something, but not the concept of running them in series.
I'm limited in what I have to work with. I don't have anything to modify the tune with nor do I have the typical scanning software.
Reading the plugs has backed up what the wide band sensor is telling me given it's installed in Bank 1 which is also the bank with the fouled plugs.
Something I seriously overlooked. An exhaust leak wouldn't make a difference on an OLSD tune as the NBO2's aren't being used for calibration. That donned on me today.
Due to my work schedule I won't be doing anything with it through this weekend. Next week I'll toss the plugs back in, give it a once over, and log what my snap on scanner can pick up then go over it.
I'm not guessing, I'm looking at photos of the exhaust tips and spark plugs.
Swapping the rails and injectors might be a good place to start. See if the uber rich cylinders follow anything. You'd think if it was an intake leak all the cylinders would have their fueling off not just specific ones.
Swapping the rails and injectors might be a good place to start. See if the uber rich cylinders follow anything. You'd think if it was an intake leak all the cylinders would have their fueling off not just specific ones.
I may try that if I dive in that far. I'm setting some....upgrades......into execution in the near future.
I actually have a very good idea that it's poor atomization. Base pressure is like 25 to 28 PSI at cruise, intentionally, because the previous tuner wasn't able to get a clean idle with the 95lb/hr injectors. I know that's a bit of injector but seriously, dropping the pressure like that is just a band aid. A buddy and I were discussing it and we both feel that at such a low pressure, it's just not enough for a good atomization coming out of the injector.
I haven't touched the car. Been working 2 1/2 straight weeks to help pay for the upgrades. Hint.....Tony Mamo is involved.......I'll be putting it back together Monday and checking I out then. Will report back.
05-08-2016, 11:43 AM
Wide Band Weirdness..........
