Setting up Throttles (using Laptop)
Discussion
Ok i know it has been done to death, and a long thread started by me many many moons ago but nothing recently.
Lets see if i have got this right correct me if I am wrong but this is how i see it. I am no expert just trying to understand the theory.
Connect the laptop (That's the obvious part lol)
Wind the idle screw back out of the way and disconnect the linkage thus separating the two Throttle bodies.
Now set the T.Pots so that they both read (According to what I have read on these hallowed pages) aprox 14.8 - 15.0
This is the starting point where everything is now equal. Both Throttles are shut and both T.Pots are reading the same.
Connect the link bar back up and take up some slack with the idle screw head for around 19 (Again taken from these hallowed pages) due to any slack in the link bar the T.pots may now read different. Adjust the link bar so that they both read 19. Both Throttles will now still be balanced and should remain so while under tension from the throttle cable.
Have I got this right so far?
Now comes the tricky bit.
Start the engine and warm it up to operating temp. (No not that bit that's easy lol this bit...)
Now adjust the T.pots to get the adaptives as close to Zero as possible, adjusting the idle screw where necessary.
Currently I have both mine around 9 and idling around 1000 but not even sitting on the idle screw and I can't turn my pots any further so am guessing I up the idle a little more and then compensate by turning the pots is that right?
It is idling very smooth but not had any road tests yet as i feel i can get it better. It used to idle happy around 8-900 rpm.
Lets see if i have got this right correct me if I am wrong but this is how i see it. I am no expert just trying to understand the theory.
Connect the laptop (That's the obvious part lol)
Wind the idle screw back out of the way and disconnect the linkage thus separating the two Throttle bodies.
Now set the T.Pots so that they both read (According to what I have read on these hallowed pages) aprox 14.8 - 15.0
This is the starting point where everything is now equal. Both Throttles are shut and both T.Pots are reading the same.
Connect the link bar back up and take up some slack with the idle screw head for around 19 (Again taken from these hallowed pages) due to any slack in the link bar the T.pots may now read different. Adjust the link bar so that they both read 19. Both Throttles will now still be balanced and should remain so while under tension from the throttle cable.
Have I got this right so far?
Now comes the tricky bit.
Start the engine and warm it up to operating temp. (No not that bit that's easy lol this bit...)
Now adjust the T.pots to get the adaptives as close to Zero as possible, adjusting the idle screw where necessary.
Currently I have both mine around 9 and idling around 1000 but not even sitting on the idle screw and I can't turn my pots any further so am guessing I up the idle a little more and then compensate by turning the pots is that right?
It is idling very smooth but not had any road tests yet as i feel i can get it better. It used to idle happy around 8-900 rpm.
I'm sure Tanguero will come on and tell you whether this is correct. But you should really do a physical check of the airflow first, particularly if you are not getting the correct tickover. So get an airflow meter and use the airflow into the banks to get the stops set.
It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
GT6k said:
I'm sure Tanguero will come on and tell you whether this is correct. But you should really do a physical check of the airflow first, particularly if you are not getting the correct tickover. So get an airflow meter and use the airflow into the banks to get the stops set.
It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
Hmmmm.....what sort of mileage had the car with the worn spindles done?It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
It wasnt a TVR and it was SU carbs, but the same thing still happens, the throttle spindles can wear and it will upset the tickover, To some extent it might be worse with the Cerb setup as the spindle is very long with the throttle pot one end and the spring and stop on the other, presumably this is why you can by roller bearing spindle upgrades.
GT6k said:
I'm sure Tanguero will come on and tell you whether this is correct. But you should really do a physical check of the airflow first, particularly if you are not getting the correct tickover. So get an airflow meter and use the airflow into the banks to get the stops set.
It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
You called? It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
You are right though. Just setting the pots to the same value does nothing to ensure the same airflow into each bank. You need to follow the procedure in the workshop manual exactly, including measuring the airflow into each bank.
Look at it like this - the only way the ECU has of knowing how much air is going into each bank is by reading the throttle pot. If you set the throttle pot without ensuring that there really is the same amount of air going into each bank, then the ECU is getting bad information and the fueling decision taken by the ECU will then be based on bad information. Adjust the throttle rod so the airflow is the same in each bank, and only then set the throttle pot readings to inform the ECU of the fact and you will get the right fueling.
And definitely worth checking the gaps with feeler gauges too.
On my car at least (and presumably some others) the arms on the spindles are not parallel, and because of the flats on the spindles you can't change them (easily). So there is no way each bank can be the same at every throttle opening. The obvious thing to do is set them to match at idle, but then they'll be different at max throttle opening.
Edited by ukkid35 on Wednesday 17th April 11:44
Toadusmodus said:
GT6k said:
I'm sure Tanguero will come on and tell you whether this is correct. But you should really do a physical check of the airflow first, particularly if you are not getting the correct tickover. So get an airflow meter and use the airflow into the banks to get the stops set.
It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
Hmmmm.....what sort of mileage had the car with the worn spindles done?It is also worth using feeler gauges to check the individual butterfly gaps, whilst there is no easy way of changing these individually it will tell you if splindles and everything else is OK. I once helped a friend set up a car which he had spent months tinkering with and never got the tickover or balance correct, it turned out the spindles were so badly worn that the butterflies never returned to the same position twice so all his adjusting was being wasted.
ukkid35 said:
On my car at least (and presumably some others) the arms on the spindles are not parallel, and because of the flats on the spindles you can't change them (easily). So there is no way each bank can be the same at every throttle opening. The obvious thing to do is set them to match at idle, but then they'll be different at max throttle opening.
Not sure I follow you. Surely both spindles turn at the same rate regardless of the absolute position of each arm. If the arms are linked then the angle of opening should be the same on both banks. Or have I completely misunderstood you?Edited by ukkid35 on Wednesday 17th April 11:44
Tanguero said:
Not sure I follow you. Surely both spindles turn at the same rate regardless of the absolute position of each arm. If the arms are linked then the angle of opening should be the same on both banks. Or have I completely misunderstood you?
Imagine the problem (arms not parallel) taken to the extreme where they are perpendicular. Moving one arm will either exaggerate or minimise the movement on the other depending on starting position.Much easier to illustrate with a diagram though.
ukkid35 said:
Imagine the problem (arms not parallel) taken to the extreme where they are perpendicular. Moving one arm will either exaggerate or minimise the movement on the other depending on starting position.
Much easier to illustrate with a diagram though.
Even if the arms are perpendicular, so long as the linkage between them is fixed length, rotating one arm will still rotate the other arm the same amount so long as the arms are the same length as each other. We may indeed benefit from a diagram because I am not sure we are thinking the same thing!Much easier to illustrate with a diagram though.
The arms need to be parallel or you get a sort of Ackerman effect as the link is moving in a linear motion which will translate to a different rotation of the spindles if they are not moving through similar arcs. Having said that mine are within a few degrees of parallel, the difference that makes in the rotation will be some fraction of this so it will be insignificant. The butterflies need to have accurately matching closed positions but a few degrees error at large openings is not going to matter.
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