Throttle response
Discussion
After some advice.
For years now my throttle response has been poor. When I tap throttle I get a dip in revs before it picks up.
The problem is that I can't remember if it did this on the original ECU or since I've upgraded it.
Can anyone with a 2.5 on an MBE let me know it theirs does it?
My mapper has improved it (going to pop over and test it tomorrow) but he thinks it not quite where he believes it should be. One thing he did do was shorten pipe work to MAP sensor.
Thanks
For years now my throttle response has been poor. When I tap throttle I get a dip in revs before it picks up.
The problem is that I can't remember if it did this on the original ECU or since I've upgraded it.
Can anyone with a 2.5 on an MBE let me know it theirs does it?
My mapper has improved it (going to pop over and test it tomorrow) but he thinks it not quite where he believes it should be. One thing he did do was shorten pipe work to MAP sensor.
Thanks
My latest Motec map does this when warm... it didnt do it previously and its some kind of thottle delay setting, rather complex in the motec as its a number of tables and parameters.
I fitted an idle control valve at the latest map which is I suspect why all the parameters had to be reset and start all over again, Im loath to play with it as its still better than it was lol.
Basically if I am off the throttle and I blip it the revs die briefly and then it revs... its only minor on mine but with my clutch it makes it horrible in stop start traffic.
If I have part throttle and blip it it doesn't have the hesitation.
I fitted an idle control valve at the latest map which is I suspect why all the parameters had to be reset and start all over again, Im loath to play with it as its still better than it was lol.
Basically if I am off the throttle and I blip it the revs die briefly and then it revs... its only minor on mine but with my clutch it makes it horrible in stop start traffic.
If I have part throttle and blip it it doesn't have the hesitation.
Forget when it's cold as it would normally die but the mapper has improved this.
It does it when warm and as far as I can remember it has always done it. He says he has got it much better and when I try it I may think wow but to him it's still not quite right.
I can't do to verbal explanation on here that he gave
but a Honda engine is very quick response and rev rise as its a light engine. A Evo is a slower pick up as its a heavy engine, he expects the ford to be in the middle. If that makes sense.
But it's sounding it might be a Noble thing
It does it when warm and as far as I can remember it has always done it. He says he has got it much better and when I try it I may think wow but to him it's still not quite right.
I can't do to verbal explanation on here that he gave
but a Honda engine is very quick response and rev rise as its a light engine. A Evo is a slower pick up as its a heavy engine, he expects the ford to be in the middle. If that makes sense. But it's sounding it might be a Noble thing
This happens because the transient fueling is not calibrated correctly. With a closed throttle at low / mid engine speeds, the "puddle fuel mass" (the fuel that has been injected into the intake manifold and is now sitting as small "bubbles" or "lumps" of liquid fuel, generally stuck to the sides of the rough manifold walls) is small because the absolute pressure is low (low pressure results in liquid fuel boiling off to vapour easily). When you snap the throttle open, the intake manifold pressure rapidly climbs up towards atmospheric pressure, and this results in the puddle mass growing significantly. If you are only injecting the same volume of fuel then if the puddle mass is growing, the actual fuel delivered to the combustion chamber must be falling! Hence, for a few cycle, you get a lean spike, which results in less torque, and hence an rpm drop (in really bad cases you get a full lean misfire and the potential for a full stall from idle).
For this reason most EMS systems use the rate of change of throttle position to add or reduce the injected fuel transiently (the so called "transient fuel correction"). This can be slightly tricky to calibrate as too much fuel is just as bad as too little fuel in terms of torque output. Mosty aftermarket EMS systems have a very basic multiplier and clamp value that adds fuel mass on tip-ins and reduces fuel mass on tip-outs (on tip-outs, the puddle mass gets reduced and the fuel sucked into the chamber resulting in a rich shift).
Generally, if you have access to your EMS, spending 20mins bliping the throttle from idle or low rpm is enough to sort out this problem when fully warm. Typically when cold, the fuel puddle mass is larger and more correction will be required to give a smooth performance.
For this reason most EMS systems use the rate of change of throttle position to add or reduce the injected fuel transiently (the so called "transient fuel correction"). This can be slightly tricky to calibrate as too much fuel is just as bad as too little fuel in terms of torque output. Mosty aftermarket EMS systems have a very basic multiplier and clamp value that adds fuel mass on tip-ins and reduces fuel mass on tip-outs (on tip-outs, the puddle mass gets reduced and the fuel sucked into the chamber resulting in a rich shift).
Generally, if you have access to your EMS, spending 20mins bliping the throttle from idle or low rpm is enough to sort out this problem when fully warm. Typically when cold, the fuel puddle mass is larger and more correction will be required to give a smooth performance.
Max_Torque said:
Generally, if you I have access to your EMS, spending 20mins bliping the throttle from idle or low rpm is enough to sort out this problem when fully warm. Typically when cold, the fuel puddle mass is larger and more correction will be required to give a smooth performance.
correct the mistake for you 
It's not difficult to do, honest!
When you get it right, you know:
MT's rally car on electronic port throttles is too quick for the rev counter !
When you get it right, you know:
MT's rally car on electronic port throttles is too quick for the rev counter !
Tuning Transient Throttle
Return to Contents
Transient Throttle Enhance
The manifold pressure sensor used with the ECU is very fast. It can respond much faster than is required to track any sudden changes in load on your engine. However, the manifold pressure seen at the sensor input may not change as quickly as what is seen by the inlets to the combustion chamber, due partly to the length of the connecting pipe. This delay can be reduced by keeping the length of vacuum hose between the inlet manifold and the pressure sensor as short as possible. Even with very short vacuum hose lengths there may still be a lag between a transient pressure occurring and the pressure reaching the sensor.
Further, when the throttle is cracked open, the sudden change in pressure forces fuel out of atomisation and onto the manifold walls, so it fails to enter the combustion chamber properly atomised, and the engine hesitates. This can be corrected by adjustment of the Transient Throttle Enrichment tables. To overcome any lean out during sudden throttle movement, a Transient Throttle Enrichment function is used to deliver the extra fuel required.
Note that throttle response can also be affected by poor manifold design. This will occur if the fuel injectors are poorly positioned and the fuel is wetting down the walls of the inlet manifold rather than remaining as a mist.
Asynchronous vs. Synchronous Enrichment
The Transient Throttle Enahncement works by adding additional fuel. It can achieve this by adding:
Asynchronous Enrichment - Additional injection pulses
Synchronous Enrichment - Enriching the current fuelling pulses
Delta Load
The Delta Load is the change of throttle position over a 10ms time frame. This is the rate of throttle position movement.
A fast throttle movement could have a TPS rate of change of 15% this means that in a time frame of 10ms the throttle position moved 15%. A slow throttle movement could have a TPS rate of change of 1%, which means that in a time frame of 10ms the throttle position only moved 1%.
Tuning Transient Throttle Enrichment
Settings
The Transient Throttle Enrichment can be enabled from the Advanced Setup settings.
The explanations of settings can be found in the Advanced Functions section under Transient Throttle.
Tuning
The Transient Throttle tables should be set up after the fuel and maps are correctly tuned for steady load running. Attempting to smooth out engine transients before the fuel maps have been optimised for steady state running may become confusing. Also ensure that you have tuned your injection angles for optimum response without any Transient Throttle Enrichment.
The Transient Throttle Enrichment setup allows the tuning of:
Enrichment Sensitivity - How much enrichment is needed for a given RPM & Throttle position
Percentage Async - The balance between Asynchronous and Synchronous enrichment over RPM
Percentage Enrichment - How much enrichment is needed for a given TPS change, known as Delta Load
Coolant Temp Correction - The amount of extra enrichment vs. coolant temperature
Enrichment Decay Rate - The speed at which the synchronous enrichment decays
Before You Begin Tuning:
Ensure that the engine is up to normal operating temperature.
Leave all the settings at their default values. Leave all tables at their default values except for Percentage Enrichment, which should have all cells set to 100%.
Tuning Enrichment Sensitivity
The Enrichment Sensitivity table defines the amount of enrichment for large throttle changes. So while the engine is idling, open the throttle as quick as you would ever open the throttle, and with large movements as large as you would ever use. You do not need to hold the throttle down for any period of time, that way the engine RPM can be minimised and stress on the engine can be reduced.
Display the Transient Throttle Delta Load channel on a display or gauge to determine the magnitude of maximum Delta Load that you can achieve and note this value, as you will use this when tuning Percentage Enrichment.
Adjust the cells in the RPM band closest to your idle speed. The default table begins at 1000rpm.
The Transient Throttle Load Source axis is the throttle position that you begin your throttle opening from. When tuning the response from idle, you will be opening the throttle from fully closed, or the 0% position. You may not be able to tune all the cells in this RPM row since you may not be able to hold near 1000rpm with 10% throttle before performing your transient throttle opening.
Adjust these cells until the best throttle response is achieved.
Repeat for each RPM row and starting throttle position to fill out the table.
Tuning Percentage Async
At low engine speeds, a high amount of asynchronous enrichment usually helps with engine responsiveness. As engine speeds increase, the amount of asynchronous will need to be reduced to better distribute the enrichment. Adjust these for best throttle response across all engine speeds. You will typically only need to vary the Percentage Async across the lower half of your engine operating range.
Tuning Percentage Enrichment
The Percentage Enrichment table characterises the reduced amount of enrichment required for part throttle movements. The Enrichment Sensitivity table above is tuned for the fastest and largest throttle changes (Delta Load) that you expect to use.
The Percentage Enrichment table determines what fraction of that amount of enrichment is required when you move the throttle more slowly, or only make small changes in throttle. The slower throttle changes or smaller throttle changes, results in a smaller Delta Load.
To tune this table, setup the far right hand column Delta Load value in the axis, to be the largest Delta Load value that you acheived when tuning the Enrichment Sensitivity table above. The table value should already be set to 100%. If not, set the table value to 100%. In the example below, the largest Transient Throttle Delta Load that was achieved was 25%.
With this table set to all 100%, the partial throttle openings will be too rich. Now vary the throttle opening speeds and throttle opening amount to achieve Transient Throttle Delta Load values less than the maximum, and adjust each cell in the table to achieve the best throttle response. In the example below, when Transient Throttle Delta Load is 10%, then 80% of the enrichment of a full speed, full throttle hit will be used.
Tuning Enrichment Decay Rate
Increase or decrease the Enrichment decay rate to shape the duration of the enrichment period. If the enrichment lasts for too long, then you need to increase the value in this table. If the enrichment does not last long enough, then decrease the values in this table.
The decay rate is difficult to tune without some form of exhaust gas oxygen meter. If you have access to an exhaust gas oxygen meter, then you may wish to use this to assist in tuning this table.
Tuning Coolant Temp Correction
To tune this table, the engine must be started cold. An engine changes temperature rapidly when started from cold, so be prepared with with laptop online and read to tune before starting the engine and beginning to tune this table.
Start the engine and check the cold throttle response. Adjust the enrichment for best throttle response across the coolant temperature while the engine is warming up.
Return to Contents
Transient Throttle Enhance
The manifold pressure sensor used with the ECU is very fast. It can respond much faster than is required to track any sudden changes in load on your engine. However, the manifold pressure seen at the sensor input may not change as quickly as what is seen by the inlets to the combustion chamber, due partly to the length of the connecting pipe. This delay can be reduced by keeping the length of vacuum hose between the inlet manifold and the pressure sensor as short as possible. Even with very short vacuum hose lengths there may still be a lag between a transient pressure occurring and the pressure reaching the sensor.
Further, when the throttle is cracked open, the sudden change in pressure forces fuel out of atomisation and onto the manifold walls, so it fails to enter the combustion chamber properly atomised, and the engine hesitates. This can be corrected by adjustment of the Transient Throttle Enrichment tables. To overcome any lean out during sudden throttle movement, a Transient Throttle Enrichment function is used to deliver the extra fuel required.
Note that throttle response can also be affected by poor manifold design. This will occur if the fuel injectors are poorly positioned and the fuel is wetting down the walls of the inlet manifold rather than remaining as a mist.
Asynchronous vs. Synchronous Enrichment
The Transient Throttle Enahncement works by adding additional fuel. It can achieve this by adding:
Asynchronous Enrichment - Additional injection pulses
Synchronous Enrichment - Enriching the current fuelling pulses
Delta Load
The Delta Load is the change of throttle position over a 10ms time frame. This is the rate of throttle position movement.
A fast throttle movement could have a TPS rate of change of 15% this means that in a time frame of 10ms the throttle position moved 15%. A slow throttle movement could have a TPS rate of change of 1%, which means that in a time frame of 10ms the throttle position only moved 1%.
Tuning Transient Throttle Enrichment
Settings
The Transient Throttle Enrichment can be enabled from the Advanced Setup settings.
The explanations of settings can be found in the Advanced Functions section under Transient Throttle.
Tuning
The Transient Throttle tables should be set up after the fuel and maps are correctly tuned for steady load running. Attempting to smooth out engine transients before the fuel maps have been optimised for steady state running may become confusing. Also ensure that you have tuned your injection angles for optimum response without any Transient Throttle Enrichment.
The Transient Throttle Enrichment setup allows the tuning of:
Enrichment Sensitivity - How much enrichment is needed for a given RPM & Throttle position
Percentage Async - The balance between Asynchronous and Synchronous enrichment over RPM
Percentage Enrichment - How much enrichment is needed for a given TPS change, known as Delta Load
Coolant Temp Correction - The amount of extra enrichment vs. coolant temperature
Enrichment Decay Rate - The speed at which the synchronous enrichment decays
Before You Begin Tuning:
Ensure that the engine is up to normal operating temperature.
Leave all the settings at their default values. Leave all tables at their default values except for Percentage Enrichment, which should have all cells set to 100%.
Tuning Enrichment Sensitivity
The Enrichment Sensitivity table defines the amount of enrichment for large throttle changes. So while the engine is idling, open the throttle as quick as you would ever open the throttle, and with large movements as large as you would ever use. You do not need to hold the throttle down for any period of time, that way the engine RPM can be minimised and stress on the engine can be reduced.
Display the Transient Throttle Delta Load channel on a display or gauge to determine the magnitude of maximum Delta Load that you can achieve and note this value, as you will use this when tuning Percentage Enrichment.
Adjust the cells in the RPM band closest to your idle speed. The default table begins at 1000rpm.
The Transient Throttle Load Source axis is the throttle position that you begin your throttle opening from. When tuning the response from idle, you will be opening the throttle from fully closed, or the 0% position. You may not be able to tune all the cells in this RPM row since you may not be able to hold near 1000rpm with 10% throttle before performing your transient throttle opening.
Adjust these cells until the best throttle response is achieved.
Repeat for each RPM row and starting throttle position to fill out the table.
Tuning Percentage Async
At low engine speeds, a high amount of asynchronous enrichment usually helps with engine responsiveness. As engine speeds increase, the amount of asynchronous will need to be reduced to better distribute the enrichment. Adjust these for best throttle response across all engine speeds. You will typically only need to vary the Percentage Async across the lower half of your engine operating range.
Tuning Percentage Enrichment
The Percentage Enrichment table characterises the reduced amount of enrichment required for part throttle movements. The Enrichment Sensitivity table above is tuned for the fastest and largest throttle changes (Delta Load) that you expect to use.
The Percentage Enrichment table determines what fraction of that amount of enrichment is required when you move the throttle more slowly, or only make small changes in throttle. The slower throttle changes or smaller throttle changes, results in a smaller Delta Load.
To tune this table, setup the far right hand column Delta Load value in the axis, to be the largest Delta Load value that you acheived when tuning the Enrichment Sensitivity table above. The table value should already be set to 100%. If not, set the table value to 100%. In the example below, the largest Transient Throttle Delta Load that was achieved was 25%.
With this table set to all 100%, the partial throttle openings will be too rich. Now vary the throttle opening speeds and throttle opening amount to achieve Transient Throttle Delta Load values less than the maximum, and adjust each cell in the table to achieve the best throttle response. In the example below, when Transient Throttle Delta Load is 10%, then 80% of the enrichment of a full speed, full throttle hit will be used.
Tuning Enrichment Decay Rate
Increase or decrease the Enrichment decay rate to shape the duration of the enrichment period. If the enrichment lasts for too long, then you need to increase the value in this table. If the enrichment does not last long enough, then decrease the values in this table.
The decay rate is difficult to tune without some form of exhaust gas oxygen meter. If you have access to an exhaust gas oxygen meter, then you may wish to use this to assist in tuning this table.
Tuning Coolant Temp Correction
To tune this table, the engine must be started cold. An engine changes temperature rapidly when started from cold, so be prepared with with laptop online and read to tune before starting the engine and beginning to tune this table.
Start the engine and check the cold throttle response. Adjust the enrichment for best throttle response across the coolant temperature while the engine is warming up.
Gadgeroonie said:
have you fitted a larger throttle body / inlet ?
it will mean the velocity of the air will be reduced compared to a smaller diameter set up making the problem worse
didn't the st24 have variable length inlets for low and top end performance
Yes and I think each port has a short and long path. Either way the transient throttle map should sort the issue. it will mean the velocity of the air will be reduced compared to a smaller diameter set up making the problem worse
didn't the st24 have variable length inlets for low and top end performance
Gadgeroonie said:
how are you switching the port from long length to short ? does it have a solenoid ?
Maybe I'm getting mixed up with what u mean. The inlet manifold has a long and short length path for each port (fixed). I think u are referring to the lower manifold. On the ST24 this had butterfly's fitted in the lower manifold for low down torque. Noble removed these so no we don't have them. Gassing Station | Noble | Top of Page | What's New | My Stuff