4.5 throttle pots...
Discussion
stuthe
said:
said: Hi all,
One of my pots is a bit noisy, can't see where to find a replacement for love nor money.
What are people doing about this nowadays? Modding a white throttle pot (a la jools' instruction), or am I missing something fundamental here?
Thanks in advance for any help.
Stu
There was a group buy on here not that long ago... were you asleep, Stu? One of my pots is a bit noisy, can't see where to find a replacement for love nor money.
What are people doing about this nowadays? Modding a white throttle pot (a la jools' instruction), or am I missing something fundamental here?
Thanks in advance for any help.
Stu
Perhaps someone who bought an extra couple as spares and could let one go your way?... (...sorry but mine are all 4.2 type)
Rik
I do believe that all of them are noisy on the odd bank (passenger/near side) - something to do with coupling from the high tension wires, at least that’s the myth.
Turn on the ignition and ECU (so fuel pump primes) without starting the engine, plug the odd bank wire into the throttle pot on the even bank, and the diagnostics will still show the same noise on the odd bank throttle - at least mine does. So it’s nothing to do with the TPOT itself.
Of course, that negates the myth (because there is no coupling from the high tension cables if the engine isn’t running). Go figure!
Turn on the ignition and ECU (so fuel pump primes) without starting the engine, plug the odd bank wire into the throttle pot on the even bank, and the diagnostics will still show the same noise on the odd bank throttle - at least mine does. So it’s nothing to do with the TPOT itself.
Of course, that negates the myth (because there is no coupling from the high tension cables if the engine isn’t running). Go figure!
^^ that may have been me .. I've tried all sorts of things over the years including ferrites on the Tpot signal wires ..
Petrolheadpete has been doing some stellar research into very small inconsistent running on his SP6 Tuscan .. as part of that he's running both tpot signal wires through one single pot ..
now you would reasonably expect the readouts on the diags screen to display the exact same readings for both banks (they're reading the same Tpot after all) but no! There seems to be some issue with the digital/analogue stage which means that the ecu will never see the exact same signal across the banks. It's only slight, and largely irrelevant most of the time, but for a system which relies on tpot accuracy in its inherent functioning this was unbelievable to me until I saw it with my own eyes. Well done to pete for spotting something that I had never spotted myself in 2 decades! Every day is a learning day.
On the cerbera we know it's an ecu issue of some kind because when you go to an alternative ecu (the emerald in my case) the signal is absolutely rock steady.
I stopped chasing these MBE issues years ago when I realised you can't ever seem to stop it happening.
One other thing though .. and I was reminded of this only yesterday when a cerb came in with running issues .. play in the throttle spindle causes erratic tpot signal spiking. The car in question had already had the intakes refurbished, but they obviously weren't right as the signal noise was there all the time until you loaded the spindle up one way to eliminate the play, then the signal spiking miraculously disappeared.
Don't automatically blame the Tpot until you're sure it's the culprit.
Petrolheadpete has been doing some stellar research into very small inconsistent running on his SP6 Tuscan .. as part of that he's running both tpot signal wires through one single pot ..
now you would reasonably expect the readouts on the diags screen to display the exact same readings for both banks (they're reading the same Tpot after all) but no! There seems to be some issue with the digital/analogue stage which means that the ecu will never see the exact same signal across the banks. It's only slight, and largely irrelevant most of the time, but for a system which relies on tpot accuracy in its inherent functioning this was unbelievable to me until I saw it with my own eyes. Well done to pete for spotting something that I had never spotted myself in 2 decades! Every day is a learning day.
On the cerbera we know it's an ecu issue of some kind because when you go to an alternative ecu (the emerald in my case) the signal is absolutely rock steady.
I stopped chasing these MBE issues years ago when I realised you can't ever seem to stop it happening.
One other thing though .. and I was reminded of this only yesterday when a cerb came in with running issues .. play in the throttle spindle causes erratic tpot signal spiking. The car in question had already had the intakes refurbished, but they obviously weren't right as the signal noise was there all the time until you loaded the spindle up one way to eliminate the play, then the signal spiking miraculously disappeared.
Don't automatically blame the Tpot until you're sure it's the culprit.
Thanks all.
Ill swap sides and see if problem moves or not. Sounds like TADTS based on your respective experiences.
That said...... If what you say is true I'd back myself yo fix this with an instrumentation amplifier / filter.
Does anyone have MBE circuit diagram of ecu itself, or a spare / blown MBE ECU I could gander at? Would be a fun side project...
Ill swap sides and see if problem moves or not. Sounds like TADTS based on your respective experiences.
That said...... If what you say is true I'd back myself yo fix this with an instrumentation amplifier / filter.
Does anyone have MBE circuit diagram of ecu itself, or a spare / blown MBE ECU I could gander at? Would be a fun side project...
Some progress today.
I agree that it looks like 1357 is a more noisy channel than 2468 - swapped pots over and 1357 is still more noisy. As you all suggested, I don't think swapping a new pot is likely to change much. To be honest, it may even be that it's fine as is, that the noise is just there and TDATS. (I didn't check the spindle play, that'll be for another day.)
The more interesting thing is trying to balance the banks. Before I messed with it, both channels seemed to be around -15-30 on the adaptive, so I swapped pots and have been aiming for the -10 -> 0% level. This is proving quite hard!!!
Each channel seems to have more like a 15% peak-to-peak adaptive swing depending on rev, so keeping with a 10% band looks impossible. I'm trying at idle, 1.5k and 2k rpm on the driveway, so not under load. Is this sensible?
Anyway, nudging things around I've tried to get the adaptives to average around -5 or -7.5% at 1.5 K RPM and I am able to nudge things to do that....... but just when I think I'm like "I know what's going on" I get confused.
I'm able to confirm that nudging a T-Pot on a bank adjusts the average of the adaptive, no problem. But I saw something unusual in the plot above. The adaptives on different banks seem to perfectly mirror each other. Has anyone seen something like this before? I can't think of any sane reason why this would happen unless the banks we're in some way linked, but they're not???
It's almost like Lamba crosstalk. I'd almost think the Lamda sensors were wired on the wrong banks or something, but I can 't imagine that to be the case because both banks are able to hunt for and settle on adaptive level with Lambda doing the 0-1.2V dance that we know and love.
anyway, amusing fun and games, but not super simple this adjustment I must admit. I don' think things are a long way off & they're better than before I started & I think the banks are pretty balanced too. Just impossible to get them to agree at idle and 1.5 & 2 k & all this swapping over meandering of the adaptive & mirroring has me a little questioning it all. I Suspect it's fine and I'm being silly, but some Pistonheads sanity checking appreciated!
I agree that it looks like 1357 is a more noisy channel than 2468 - swapped pots over and 1357 is still more noisy. As you all suggested, I don't think swapping a new pot is likely to change much. To be honest, it may even be that it's fine as is, that the noise is just there and TDATS. (I didn't check the spindle play, that'll be for another day.)
The more interesting thing is trying to balance the banks. Before I messed with it, both channels seemed to be around -15-30 on the adaptive, so I swapped pots and have been aiming for the -10 -> 0% level. This is proving quite hard!!!
Each channel seems to have more like a 15% peak-to-peak adaptive swing depending on rev, so keeping with a 10% band looks impossible. I'm trying at idle, 1.5k and 2k rpm on the driveway, so not under load. Is this sensible?
Anyway, nudging things around I've tried to get the adaptives to average around -5 or -7.5% at 1.5 K RPM and I am able to nudge things to do that....... but just when I think I'm like "I know what's going on" I get confused.
I'm able to confirm that nudging a T-Pot on a bank adjusts the average of the adaptive, no problem. But I saw something unusual in the plot above. The adaptives on different banks seem to perfectly mirror each other. Has anyone seen something like this before? I can't think of any sane reason why this would happen unless the banks we're in some way linked, but they're not???
It's almost like Lamba crosstalk. I'd almost think the Lamda sensors were wired on the wrong banks or something, but I can 't imagine that to be the case because both banks are able to hunt for and settle on adaptive level with Lambda doing the 0-1.2V dance that we know and love.
anyway, amusing fun and games, but not super simple this adjustment I must admit. I don' think things are a long way off & they're better than before I started & I think the banks are pretty balanced too. Just impossible to get them to agree at idle and 1.5 & 2 k & all this swapping over meandering of the adaptive & mirroring has me a little questioning it all. I Suspect it's fine and I'm being silly, but some Pistonheads sanity checking appreciated!
stuthe said:
said: Some progress today.
I agree that it looks like 1357 is a more noisy channel than 2468 - swapped pots over and 1357 is still more noisy. As you all suggested, I don't think swapping a new pot is likely to change much. To be honest, it may even be that it's fine as is, that the noise is just there and TDATS. (I didn't check the spindle play, that'll be for another day.)
The more interesting thing is trying to balance the banks. Before I messed with it, both channels seemed to be around -15-30 on the adaptive, so I swapped pots and have been aiming for the -10 -> 0% level. This is proving quite hard!!!
Each channel seems to have more like a 15% peak-to-peak adaptive swing depending on rev, so keeping with a 10% band looks impossible. I'm trying at idle, 1.5k and 2k rpm on the driveway, so not under load. Is this sensible?
Anyway, nudging things around I've tried to get the adaptives to average around -5 or -7.5% at 1.5 K RPM and I am able to nudge things to do that....... but just when I think I'm like "I know what's going on" I get confused.
I'm able to confirm that nudging a T-Pot on a bank adjusts the average of the adaptive, no problem. But I saw something unusual in the plot above. The adaptives on different banks seem to perfectly mirror each other. Has anyone seen something like this before? I can't think of any sane reason why this would happen unless the banks we're in some way linked, but they're not???
It's almost like Lamba crosstalk. I'd almost think the Lamda sensors were wired on the wrong banks or something, but I can 't imagine that to be the case because both banks are able to hunt for and settle on adaptive level with Lambda doing the 0-1.2V dance that we know and love.
anyway, amusing fun and games, but not super simple this adjustment I must admit. I don' think things are a long way off & they're better than before I started & I think the banks are pretty balanced too. Just impossible to get them to agree at idle and 1.5 & 2 k & all this swapping over meandering of the adaptive & mirroring has me a little questioning it all. I Suspect it's fine and I'm being silly, but some Pistonheads sanity checking appreciated!
I thought I was the only recently going up this learning curve!I agree that it looks like 1357 is a more noisy channel than 2468 - swapped pots over and 1357 is still more noisy. As you all suggested, I don't think swapping a new pot is likely to change much. To be honest, it may even be that it's fine as is, that the noise is just there and TDATS. (I didn't check the spindle play, that'll be for another day.)
The more interesting thing is trying to balance the banks. Before I messed with it, both channels seemed to be around -15-30 on the adaptive, so I swapped pots and have been aiming for the -10 -> 0% level. This is proving quite hard!!!
Each channel seems to have more like a 15% peak-to-peak adaptive swing depending on rev, so keeping with a 10% band looks impossible. I'm trying at idle, 1.5k and 2k rpm on the driveway, so not under load. Is this sensible?
Anyway, nudging things around I've tried to get the adaptives to average around -5 or -7.5% at 1.5 K RPM and I am able to nudge things to do that....... but just when I think I'm like "I know what's going on" I get confused.
I'm able to confirm that nudging a T-Pot on a bank adjusts the average of the adaptive, no problem. But I saw something unusual in the plot above. The adaptives on different banks seem to perfectly mirror each other. Has anyone seen something like this before? I can't think of any sane reason why this would happen unless the banks we're in some way linked, but they're not???
It's almost like Lamba crosstalk. I'd almost think the Lamda sensors were wired on the wrong banks or something, but I can 't imagine that to be the case because both banks are able to hunt for and settle on adaptive level with Lambda doing the 0-1.2V dance that we know and love.
anyway, amusing fun and games, but not super simple this adjustment I must admit. I don' think things are a long way off & they're better than before I started & I think the banks are pretty balanced too. Just impossible to get them to agree at idle and 1.5 & 2 k & all this swapping over meandering of the adaptive & mirroring has me a little questioning it all. I Suspect it's fine and I'm being silly, but some Pistonheads sanity checking appreciated!
My adaptives also mirror each other on the same way as your plot shows, but mostly when not under load. When driving around, they mostly do their own thing. I suspect it’s fine, (I assumed it was the firing order or something).
I also chose 1500-2000 rpm for setup, as allows for plenty up and down adjustment of throttle (and hence airflow), on both banks.
When adjusting a given bank for airflow, you adjust the idle stop or link bar, but as you do so, you also have a varying throttle pot and hence fueling. If one could adjust the airflow with a constant fuelling, that will get you to final setup faster. I found this can be done on the even bank by pulling out the even bank t-pot connector - the fuelling then matches the other banks t-pot, which is handy, because you’re trying to balance the 2 banks. Once the airflow matches, you can plug the even t-pot back in and adjust it to be the same as the odd bank.
See my other thread (adaptives) for my ‘procedure’ - I followed it and got to a good final setup, with relative ease. And that was after one whole day of pure frustration and not doing what the hell I was going.
I made a little crib-sheet which I kept on the windshield and thought through the various scenarios and my procedure before starting (like revising for exams!).
Honestly, it’s not rocket science, just very hot and therefore very frustrating!
After achieving a good setup, I found my link bar was crap and am ordering a new/proper one from Peter - that will really help to keep the setup nailed down.
Good luck!
Edited by Imran999 on Sunday 4th August 22:51
I've spent ages trying to find a post from Jools where he says he doesnt bother with zero adaptives anymore. I cant find it but I'm sure he's said it recently-ish. As long as adaptives aren't hitting the limits all is fine. You also need to bear in mind the idle throttle pot values affect ignition timing so in your quest for zero adaptives you may find you've set the pots in such a way that the ECU has nowhere to go in terms of ignition advance to stabilise the idle speed if it drops when the fans come on, or you select air conditioning.
I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
CerbWill said:
I've spent ages trying to find a post from Jools where he says he doesnt bother with zero adaptives anymore. I cant find it but I'm sure he's said it recently-ish. As long as adaptives aren't hitting the limits all is fine. You also need to bear in mind the idle throttle pot values affect ignition timing so in your quest for zero adaptives you may find you've set the pots in such a way that the ECU has nowhere to go in terms of ignition advance to stabilise the idle speed if it drops when the fans come on, or you select air conditioning.
I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
I would say 1500-2000 was more important than idle though for even adaptives.I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
Jhonno said:
I would say 1500-2000 was more important than idle though for even adaptives.
This was my thinking too - if I mash the pedal and go full-open-loop I'll be doing that from, say, 1.5-2krpm, not idl. I'd want stoichometry to be correct from that point. Idle is going to be a side effect of throttle bodies/ linearity of TPOT etc... and seems to be a lot more "sensitive" (drilled screws/TPOTs differ by 0.5-1% every time I open/shut Throttle) - I think air flow / TPOT repeatability seems more stable/deterministic with a few revs! I'll try setting up at around 1.5-2K rpm and backing off to a 1k idle, and the adaptives can be what they are at idle - I think I'd prefer them lock-in around driving revs.... unless I'm being MAD??
CerbWill said:
I've spent ages trying to find a post from Jools where he says he doesnt bother with zero adaptives anymore. I cant find it but I'm sure he's said it recently-ish. As long as adaptives aren't hitting the limits all is fine. You also need to bear in mind the idle throttle pot values affect ignition timing so in your quest for zero adaptives you may find you've set the pots in such a way that the ECU has nowhere to go in terms of ignition advance to stabilise the idle speed if it drops when the fans come on, or you select air conditioning.
I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
You didn't dream it I did say it.I have no idea where this idea of doing the setup at higher RPM has come from all of a sudden. If you were to get the airflow into each ITB equal at 1500-2000rpm it wont be equal at idle and adaptives will be all over the place.
It's one of those times when you wish you could delete all the old info from the net because as time has gone on what we once thought was important turns out to be not very important at all.
stuthe said:
said: This was my thinking too - if I mash the pedal and go full-open-loop I'll be doing that from, say, 1.5-2krpm, not idl. I'd want stoichometry to be correct from that point. Idle is going to be a side effect of throttle bodies/ linearity of TPOT etc... and seems to be a lot more "sensitive" (drilled screws/TPOTs differ by 0.5-1% every time I open/shut Throttle) - I think air flow / TPOT repeatability seems more stable/deterministic with a few revs!
I'll try setting up at around 1.5-2K rpm and backing off to a 1k idle, and the adaptives can be what they are at idle - I think I'd prefer them lock-in around driving revs.... unless I'm being MAD??
If you cant get a repeatable idle Tpot reading that's an issue, especially when shutting the throttle from a small opening as you're likely to do. Throttle return springs may be a bit weak, or some play in the pot(s).I'll try setting up at around 1.5-2K rpm and backing off to a 1k idle, and the adaptives can be what they are at idle - I think I'd prefer them lock-in around driving revs.... unless I'm being MAD??
The engine will run on either throttle pot.
The odd bank pot is used to provide ignition look-up for both banks and fuelling for the off bank. The even pot is used to provide fuelling for the even bank.
When running on only the even one, I do believe that will be used for both ignition and timing for both banks.
If it’s shutting down on just the even one, it means the throttle pot settings for the even bank just aren’t close enough for the odd bank. If the odd bank is flowing more air than the even one, then the pot is not calling for enough throttle opening (and therefore fuelling), then you would expect it to stall more easily.
I’m no expert, I’m sure one will comment soon though!
The odd bank pot is used to provide ignition look-up for both banks and fuelling for the off bank. The even pot is used to provide fuelling for the even bank.
When running on only the even one, I do believe that will be used for both ignition and timing for both banks.
If it’s shutting down on just the even one, it means the throttle pot settings for the even bank just aren’t close enough for the odd bank. If the odd bank is flowing more air than the even one, then the pot is not calling for enough throttle opening (and therefore fuelling), then you would expect it to stall more easily.
I’m no expert, I’m sure one will comment soon though!
Gassing Station | Cerbera | Top of Page | What's New | My Stuff