Balancing throttle bodies
Discussion
Hello,
I have a 4.2 cerbera that has unbalanced throttle bodies. For instance, on the driver bank, the body that is up front is displaying 7 on the balancer at idle, the other 3 are displaying 5. I don't want to increase the flow of the 3 less flowing cylinders as I don't think a hole in a screw is the solution. I would prefer to decrease the one cylinder that is flowing too much.
Do you have any idea how to do this? Make new butterflies?
Thanks in advance.
Julien
I have a 4.2 cerbera that has unbalanced throttle bodies. For instance, on the driver bank, the body that is up front is displaying 7 on the balancer at idle, the other 3 are displaying 5. I don't want to increase the flow of the 3 less flowing cylinders as I don't think a hole in a screw is the solution. I would prefer to decrease the one cylinder that is flowing too much.
Do you have any idea how to do this? Make new butterflies?
Thanks in advance.
Julien
The accepted way to synchronise flows on any one bank is by the use of drilled screws.
But I would suggest that there is a more fundamental problem here with the one cyl considerably higher than the others, something is physically wrong e.g. bent or badly fitted butterfly, as it's more probable for one cyl to be 'wrong' than three...
But I would suggest that there is a more fundamental problem here with the one cyl considerably higher than the others, something is physically wrong e.g. bent or badly fitted butterfly, as it's more probable for one cyl to be 'wrong' than three...
pmessling said:
I’d check the throttle body to heat barrier O rings as well.
This. In reply to your previous Q, I meant check that they are all seating in exactly the same way when closed as there is usually wiggle room before nipping the screws up... but, thinking further about it and because they are on a common spindle, if one isn't seating correctly then it's probably holding the others open too, unless either the disc is bent or the spindle is twisted.
But I think Peter is on to something more likely with the intake leak idea.
Rik
Very common, the tolerances required are tiny so airflow variations are commonplace.
Investigate for any air leaks as mentioned already, but there's an easy way to deal with this though you may already have inadvertently done something that means it will be a long process ..
I suspect that as part of your throttle balancing routine you may have cleaned all the butterflies and throats, if so the best plan is to use the drilled screws and bring the low flowing pots up .. assuming you have good enough sealing butterflies you should still be able to wind the throttle stop back to gain an acceptable idle speed.
The way I've been doing it for yonks is to NOT clean the butterflies but to set everything up as best I can and see which butterflies are flowing low, then very briefly spray those butterflies with carb cleaner .. use it very sparingly as you don't want to over clean them and make them flow higher than the already high flowing pots. This process works better the dirtier the butterflies are, so resist the temptation to clean everything in sight to a bright shiny finish, you're actually making life difficult for yourself by doing that.
It's a really easy way to get the airflows balanced, takes literally a few minutes to get it all sorted. And it sounds like you do your own maintenance so each time you have the airboxes off just go through the airflows and only spray the lowest flowing pots to keep everything running evenly.
Note that sadly you can't do this on the 4.5 as the injectors are constantly cleaning the butterflies .. and the SP6 cars have have individually adjustable butterflies anyway.
Investigate for any air leaks as mentioned already, but there's an easy way to deal with this though you may already have inadvertently done something that means it will be a long process ..
I suspect that as part of your throttle balancing routine you may have cleaned all the butterflies and throats, if so the best plan is to use the drilled screws and bring the low flowing pots up .. assuming you have good enough sealing butterflies you should still be able to wind the throttle stop back to gain an acceptable idle speed.
The way I've been doing it for yonks is to NOT clean the butterflies but to set everything up as best I can and see which butterflies are flowing low, then very briefly spray those butterflies with carb cleaner .. use it very sparingly as you don't want to over clean them and make them flow higher than the already high flowing pots. This process works better the dirtier the butterflies are, so resist the temptation to clean everything in sight to a bright shiny finish, you're actually making life difficult for yourself by doing that.
It's a really easy way to get the airflows balanced, takes literally a few minutes to get it all sorted. And it sounds like you do your own maintenance so each time you have the airboxes off just go through the airflows and only spray the lowest flowing pots to keep everything running evenly.
Note that sadly you can't do this on the 4.5 as the injectors are constantly cleaning the butterflies .. and the SP6 cars have have individually adjustable butterflies anyway.
YOU'RE THE BEST!
I've cleaned the 3 less flowing bodies and now they are all equal at around 6.5/7. I'm doing some little things by myself, more because no-one know Tvrs here in Bulgaria than anything else, but I'm very slowly learning and didn't knew the throat had to be cleaned when setting the car.
Thanks a lot for the tip! As I've very little available time, I'll finish the cleaning and will set the car properly and will tell you what's the final result.
For now I'm enjoying my little victory on the car
Julien
I've cleaned the 3 less flowing bodies and now they are all equal at around 6.5/7. I'm doing some little things by myself, more because no-one know Tvrs here in Bulgaria than anything else, but I'm very slowly learning and didn't knew the throat had to be cleaned when setting the car.
Thanks a lot for the tip! As I've very little available time, I'll finish the cleaning and will set the car properly and will tell you what's the final result.
For now I'm enjoying my little victory on the car
Julien
Good evening!
I've cleaned the other bank today and all cylinders went from 4-5 to 7... So a good clean was really needed.
I still have discrepancies between cylinders, though à lot better than before, and now all manifolds are heating at the same rate,which is good. What is the acceptable difference between the most and least flowing cylinder on one bank?
Thanks in advance!
Julien
I've cleaned the other bank today and all cylinders went from 4-5 to 7... So a good clean was really needed.
I still have discrepancies between cylinders, though à lot better than before, and now all manifolds are heating at the same rate,which is good. What is the acceptable difference between the most and least flowing cylinder on one bank?
Thanks in advance!
Julien
If you can get it within 0.5 kg/hr that will be fine. To be fair though they can run fine with far more variation than that, but if you aim to get them all pretty equal you stand the best chance of smoother running. Always remember to never clean out the highest flowing butterflies however tempting it might be, and use the "clean the lowest flowing butterflies" method to bring their airflows up and you'll not go too far wrong.
Hello,
I need your help again!
The car is now a lot smoother, responsive and easy to drive, but it's impossible to get tje adaptatives set properly!
Basically, both adaptatives are to the max around 30 but I can't increase anymore the value at the potentiometers.
All cylinders are sucking an equal amount of air (tested before, not after messing with the engine). Idle set at 1500 rpm for setting the adaptatives without stalling, pots are around 17/18. When I remove all stops, butterflies are closed at 14.4 and 16.9. Adaptatives at 30 at idle à d lambda at 0. When I give gas, lambdas move so apparently not shot?
My gut feeling is that my induction is leaking air. Am I right? How to test that? Spraying wd40? Where?
Thank you in advance for your help.
Julien
I need your help again!
The car is now a lot smoother, responsive and easy to drive, but it's impossible to get tje adaptatives set properly!
Basically, both adaptatives are to the max around 30 but I can't increase anymore the value at the potentiometers.
All cylinders are sucking an equal amount of air (tested before, not after messing with the engine). Idle set at 1500 rpm for setting the adaptatives without stalling, pots are around 17/18. When I remove all stops, butterflies are closed at 14.4 and 16.9. Adaptatives at 30 at idle à d lambda at 0. When I give gas, lambdas move so apparently not shot?
My gut feeling is that my induction is leaking air. Am I right? How to test that? Spraying wd40? Where?
Thank you in advance for your help.
Julien
If you're sure the lambdas are working correctly then no reading from them and high adaptives is an excess of air for the fuel being supplied. In that case you need to increase your throttle position sensor positions relative to your throttle shaft position. This moves the point in the fuel map richer for any given throttle shaft position.
It also increases the ignition advance, so whereas your previous airflow might have supported 1000rpm on a weak and retarded map point, adjusting the position sensors higher will increase your idle speed, so you will have to go back and reduce that as appropriate.
It also increases the ignition advance, so whereas your previous airflow might have supported 1000rpm on a weak and retarded map point, adjusting the position sensors higher will increase your idle speed, so you will have to go back and reduce that as appropriate.
Jooles81 said:
Hello,
I need your help again!
The car is now a lot smoother, responsive and easy to drive, but it's impossible to get tje adaptatives set properly!
Basically, both adaptatives are to the max around 30 but I can't increase anymore the value at the potentiometers.
All cylinders are sucking an equal amount of air (tested before, not after messing with the engine). Idle set at 1500 rpm for setting the adaptatives without stalling, pots are around 17/18. When I remove all stops, butterflies are closed at 14.4 and 16.9. Adaptatives at 30 at idle à d lambda at 0. When I give gas, lambdas move so apparently not shot?
My gut feeling is that my induction is leaking air. Am I right? How to test that? Spraying wd40? Where?
Thank you in advance for your help.
Julien
4.2 Cerb should be set to 19% at idle iirc.I need your help again!
The car is now a lot smoother, responsive and easy to drive, but it's impossible to get tje adaptatives set properly!
Basically, both adaptatives are to the max around 30 but I can't increase anymore the value at the potentiometers.
All cylinders are sucking an equal amount of air (tested before, not after messing with the engine). Idle set at 1500 rpm for setting the adaptatives without stalling, pots are around 17/18. When I remove all stops, butterflies are closed at 14.4 and 16.9. Adaptatives at 30 at idle à d lambda at 0. When I give gas, lambdas move so apparently not shot?
My gut feeling is that my induction is leaking air. Am I right? How to test that? Spraying wd40? Where?
Thank you in advance for your help.
Julien
Hello,
Thanks for your inputs.
My problem is precisely that I can't move the throttle pot enough to increase the tpots value enough to have good adaptatives.
Said another way, my butterflies are so closed at idle that I have 1200rpm and tpots value of 17 and can't move the tpots to a higher value. I can close the butterflies a bit though.
Julien
Thanks for your inputs.
My problem is precisely that I can't move the throttle pot enough to increase the tpots value enough to have good adaptatives.
Said another way, my butterflies are so closed at idle that I have 1200rpm and tpots value of 17 and can't move the tpots to a higher value. I can close the butterflies a bit though.
Julien
Jooles81 said:
Hello,
Thanks for your inputs.
My problem is precisely that I can't move the throttle pot enough to increase the tpots value enough to have good adaptatives.
Said another way, my butterflies are so closed at idle that I have 1200rpm and tpots value of 17 and can't move the tpots to a higher value. I can close the butterflies a bit though.
Julien
Slot or enlarge the holes on the TPS.Thanks for your inputs.
My problem is precisely that I can't move the throttle pot enough to increase the tpots value enough to have good adaptatives.
Said another way, my butterflies are so closed at idle that I have 1200rpm and tpots value of 17 and can't move the tpots to a higher value. I can close the butterflies a bit though.
Julien
Closing the throttles won't help if you can't move the throttle position sensor relative to the spindle.
Have you checked your fuel pressure? The ecu can trim to 37 percent, so that's a LOT of extra fuel it can add, so if you're still weak running even allowing for that massive trimming ability there's something else amiss.
There's a couple of tweaks you can try to get yourself up and running if you want in the meantime .. try using a small file to elongate the holes in the throttle sensor body to allow you to rotate it further.
With an idle speed of say around 900-950 rpm you should be looking at throttle percentages of around 18 percent sp for your idle speed of 1200 you'd want to see , say, around 21 percent?
Try also clamping off the small pipe that goes to the airbox oil catch tank (it's supposed to have a restrictor in it, but people replace the hose not realising it's supposed to be restricted and end up with that pipe as a source of a big air leak.)
Have you checked your fuel pressure? The ecu can trim to 37 percent, so that's a LOT of extra fuel it can add, so if you're still weak running even allowing for that massive trimming ability there's something else amiss.
There's a couple of tweaks you can try to get yourself up and running if you want in the meantime .. try using a small file to elongate the holes in the throttle sensor body to allow you to rotate it further.
With an idle speed of say around 900-950 rpm you should be looking at throttle percentages of around 18 percent sp for your idle speed of 1200 you'd want to see , say, around 21 percent?
Try also clamping off the small pipe that goes to the airbox oil catch tank (it's supposed to have a restrictor in it, but people replace the hose not realising it's supposed to be restricted and end up with that pipe as a source of a big air leak.)
OK, thanks.
Am I right thinking that this may also be a leak at the thermal barrier?
I've clamped the hose that goes from the catch tank to a splitter to the fuel rails without results. I also sprayed the whole induction with carb cleaner without change of rpm...
How could. I check the fuel pressure? I have doubt this would be the problem as the car is pretty nice at full throttle and high rpms...
Julien
Am I right thinking that this may also be a leak at the thermal barrier?
I've clamped the hose that goes from the catch tank to a splitter to the fuel rails without results. I also sprayed the whole induction with carb cleaner without change of rpm...
How could. I check the fuel pressure? I have doubt this would be the problem as the car is pretty nice at full throttle and high rpms...
Julien
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