Can anyone tell me what the threshold of concern is for bank to bank deltas for WB readings and/or STFTs?
I am seeing differences of up to a full AFR point or so at WOT on the widebands; I have seen one bank at 12.5:1 and the other at 11.5:1 and after a few other adjustments I now start to see 10.0:1 or even lower in one bank and 11:0 AFR in the other. I say start to see because it bucks and falls on its face at WOT with the current tune. We are still working that issue..
On the last motor that blew, I had two widebands, one an innovate MTX-L, the other a really old PLX unit; on the previous setup, these WB units tracked pretty closely together in the logs.
Since seeing the bank to bank deltas on the new motor, I went ahead and bought another new MTX-L WB unit so both banks have new WBs.
Since the build, the STFTs have never been right at idle or at part throttle either, at one point they were at .75-ish in one bank and .90-ish in the other. After more tuning adjustment, one trim remains close to 1.00 and the other closer to .85; but seems to vary quite wildly with 10-15% delta between banks.
The LTFTs are stuck at 1.00 and I am told the adaptive has been disabled.
The tuner didn’t seem to be concerned with the deltas, which does not seem quite right to me. I could see 5% trim delta being within reason. Maybe a WB AFR delta being a quarter to a half a point maybe?
He told me I could go crazy chasing some of these little details. So am I being too particular, or is my car and/or my tune crap?
I just don’t know? Can anyone give an opinion on what the acceptable thresholds are for either reading?
Fuel economy is also garbage since the rebuild, not that gas mileage is the major concern, but it makes me think something is wrong with the tune and/or a mechanical issue...
The car is a Merc Marauder DOHC 4.6 with a Paxton novi1200 spun fairly close to the max recommended impeller RPM and comes up to about 12-13 PSI, has new 60lb semens deka injectors, still a returnless fuel system, new aeromotive stealth 340 , KB boost a pump, and mild intake cam swap with aftermarket valve springs. This is in a teksid block with forged bottom end at what I was told is 9.5:1 CR.
This is all in a relatively new build, except for the blower was already on the car when the last engine blew.
Not sure why old motor blew, other than head gaskets and overheating one day on the way to work. So I replaced everything I thought might could have contributed.
Before it blew, STFTs were always very close to 1.00 in both banks, like always .98-1.02... but I got too comfortable with the car and kinda got lazy on monitoring things and datalogs, so I have no datalogs from close to the time period when it blew.
Since the new build, the shop gave some potential reasons for the deltas, which I have addressed without correcting the issues:
Could have been HEGOs, so I just re-replaced with new motorcraft O2s (previous ones had less than a year on them).
Could have been a weak coil, so replaced those with a new set of MSD coils; and threw in a set of new TR6 plugs for good measure.
Could have been that "the widebands are lying to you"... so I replaced an older PLX wideband unit with a new innovative MTX-L yet the problem remains. So now there is a matching set of MTX-L WBs in each bank. I could theoretically change the o2 sensor on the 8-9 month old WB MTX-L unit, but I don't think its the culprit because the STFTs and WBs both show the imbalance.
Could be one of the new injectors. So my next step will be to swap injectors from one bank to the other to see if the readings swap banks with the injectors...
The thing he did not bring up was the possibility that the cams could be out of phase, which I am beginning to worry about?
This *should* not be the issue, as he claimed that he was going to degree the cams when he put the motor together. Kinda wondering if he did indeed degree the cams??
I addressed every potential issue he mentioned in hopes that if the issue remains, he will be forced to address it.
Just for more background... I have had all kinds of tuning and mechanical issues since I got it back from the builder and it has been back several times for this and that.
When I am satisfied there are no major mechanical issues for him to correct, I will be taking it elsewhere for a re-tune.
I am pretty confident that the MAF xfer is all kinds of wrong. He built a custom intercooler from a Bell core (which has a very small pinhole leak by the way, which I found when checking for vacuum leaks by pressurizing the intake tract). As part of this additional custom work, he also agreed to make an air divider for the conical air filter and re-route the intake tube a bit. He tuned the car on the dyno prior to building the air divider, which also involved lengthening a section of the intake tube right at the MAF sensor. The MAF sensor was previously 1" from the end of the intake tube, but is now a more correct 4-5" from the end of the tube. So I cannot imagine that airflow was not affected by this change, requiring a remapping of the MAF xfer function. I am pretty sure he never got the car back on the dyno to adjust the tune after this change. He also swapped fuel pumps from my old Ford GT pump to the new Aeromotive Stealth 340 after he dyno tuned the car. I believe most of the tuning changes he has made since the original dyno tune were from the hip, not on the dyno, and without reviewing datalogs.
As a matter of fact, the last time it was in the shop, he told me I might need to retard the timing 2* and add 6% fuel accross the board. These seem like stab in the dark kinds of adjustments...
I would like to hear some opinions on this, as I admit I can be a mite particular; I just want the car to be right, with a safe tune after spending 10K since the engine blew earlier this year.
I am seeing differences of up to a full AFR point or so at WOT on the widebands; I have seen one bank at 12.5:1 and the other at 11.5:1 and after a few other adjustments I now start to see 10.0:1 or even lower in one bank and 11:0 AFR in the other. I say start to see because it bucks and falls on its face at WOT with the current tune. We are still working that issue..
On the last motor that blew, I had two widebands, one an innovate MTX-L, the other a really old PLX unit; on the previous setup, these WB units tracked pretty closely together in the logs.
Since seeing the bank to bank deltas on the new motor, I went ahead and bought another new MTX-L WB unit so both banks have new WBs.
Since the build, the STFTs have never been right at idle or at part throttle either, at one point they were at .75-ish in one bank and .90-ish in the other. After more tuning adjustment, one trim remains close to 1.00 and the other closer to .85; but seems to vary quite wildly with 10-15% delta between banks.
The LTFTs are stuck at 1.00 and I am told the adaptive has been disabled.
The tuner didn’t seem to be concerned with the deltas, which does not seem quite right to me. I could see 5% trim delta being within reason. Maybe a WB AFR delta being a quarter to a half a point maybe?
He told me I could go crazy chasing some of these little details. So am I being too particular, or is my car and/or my tune crap?
I just don’t know? Can anyone give an opinion on what the acceptable thresholds are for either reading?
Fuel economy is also garbage since the rebuild, not that gas mileage is the major concern, but it makes me think something is wrong with the tune and/or a mechanical issue...
The car is a Merc Marauder DOHC 4.6 with a Paxton novi1200 spun fairly close to the max recommended impeller RPM and comes up to about 12-13 PSI, has new 60lb semens deka injectors, still a returnless fuel system, new aeromotive stealth 340 , KB boost a pump, and mild intake cam swap with aftermarket valve springs. This is in a teksid block with forged bottom end at what I was told is 9.5:1 CR.
This is all in a relatively new build, except for the blower was already on the car when the last engine blew.
Not sure why old motor blew, other than head gaskets and overheating one day on the way to work. So I replaced everything I thought might could have contributed.
Before it blew, STFTs were always very close to 1.00 in both banks, like always .98-1.02... but I got too comfortable with the car and kinda got lazy on monitoring things and datalogs, so I have no datalogs from close to the time period when it blew.
Since the new build, the shop gave some potential reasons for the deltas, which I have addressed without correcting the issues:
Could have been HEGOs, so I just re-replaced with new motorcraft O2s (previous ones had less than a year on them).
Could have been a weak coil, so replaced those with a new set of MSD coils; and threw in a set of new TR6 plugs for good measure.
Could have been that "the widebands are lying to you"... so I replaced an older PLX wideband unit with a new innovative MTX-L yet the problem remains. So now there is a matching set of MTX-L WBs in each bank. I could theoretically change the o2 sensor on the 8-9 month old WB MTX-L unit, but I don't think its the culprit because the STFTs and WBs both show the imbalance.
Could be one of the new injectors. So my next step will be to swap injectors from one bank to the other to see if the readings swap banks with the injectors...
The thing he did not bring up was the possibility that the cams could be out of phase, which I am beginning to worry about?
This *should* not be the issue, as he claimed that he was going to degree the cams when he put the motor together. Kinda wondering if he did indeed degree the cams??
I addressed every potential issue he mentioned in hopes that if the issue remains, he will be forced to address it.
Just for more background... I have had all kinds of tuning and mechanical issues since I got it back from the builder and it has been back several times for this and that.
When I am satisfied there are no major mechanical issues for him to correct, I will be taking it elsewhere for a re-tune.
I am pretty confident that the MAF xfer is all kinds of wrong. He built a custom intercooler from a Bell core (which has a very small pinhole leak by the way, which I found when checking for vacuum leaks by pressurizing the intake tract). As part of this additional custom work, he also agreed to make an air divider for the conical air filter and re-route the intake tube a bit. He tuned the car on the dyno prior to building the air divider, which also involved lengthening a section of the intake tube right at the MAF sensor. The MAF sensor was previously 1" from the end of the intake tube, but is now a more correct 4-5" from the end of the tube. So I cannot imagine that airflow was not affected by this change, requiring a remapping of the MAF xfer function. I am pretty sure he never got the car back on the dyno to adjust the tune after this change. He also swapped fuel pumps from my old Ford GT pump to the new Aeromotive Stealth 340 after he dyno tuned the car. I believe most of the tuning changes he has made since the original dyno tune were from the hip, not on the dyno, and without reviewing datalogs.
As a matter of fact, the last time it was in the shop, he told me I might need to retard the timing 2* and add 6% fuel accross the board. These seem like stab in the dark kinds of adjustments...
I would like to hear some opinions on this, as I admit I can be a mite particular; I just want the car to be right, with a safe tune after spending 10K since the engine blew earlier this year.
