how much boost ?
08-06-2003, 11:45 PM
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how much boost ?
Viperbob and a few others can help me here...
I am having the programmable management fitted to the 993 at the moment.
Tuning is being done tommorow.
I was intending to use 1.1bar
What sort of boost levels have people used ?
Paul
I am having the programmable management fitted to the 993 at the moment.
Tuning is being done tommorow.
I was intending to use 1.1bar
What sort of boost levels have people used ?
Paul
08-07-2003, 07:04 AM
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The factory Motronic system varies the boost according to inputs - IMHO this is the best system for the 993tt engine. My reprogrammed dyno developed Motronic allows as much as 1.6bar (proper head sealing and twin plug is needed for these sort of levels) around 4500rpm (in 5th/6th gear) levelling down to 1 bar around peak power.
If you are using a fixed boost level then you are missing out on much of what the factory intended.
The factory Motronic system varies the boost according to inputs - IMHO this is the best system for the 993tt engine. My reprogrammed dyno developed Motronic allows as much as 1.6bar (proper head sealing and twin plug is needed for these sort of levels) around 4500rpm (in 5th/6th gear) levelling down to 1 bar around peak power.
If you are using a fixed boost level then you are missing out on much of what the factory intended.
08-07-2003, 07:41 AM
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KRA993tt
Some tuners (eg Andial) ditch the factory Motronic altogether and run an alternative system which will work with a fixed MAXIMUM boost, so once the turbos spool up to say 1.1 bar, a boost controller will maintain that boost level to maximum revs with the alternative system controlloing fuelling, timing etc. Protomotive specifically still use the basic Motronic but disconnect the "boost control" part of the system and use a boost controller to run a fixed MAXIMUM. This way of doing things obviously works, but it misses out on the benefits of the Motronic controlling boost which is mainly the overboost facility where the Motronic will allow more boost according to inputs (mainly temperature and fuel dependant) and offers more safety features to protect your engine (like backing off the boost in certain critical conditions) - your engine will not grenade without this feature as it has other ways (other than boost control) of protecting itself.
Some tuners (eg Andial) ditch the factory Motronic altogether and run an alternative system which will work with a fixed MAXIMUM boost, so once the turbos spool up to say 1.1 bar, a boost controller will maintain that boost level to maximum revs with the alternative system controlloing fuelling, timing etc. Protomotive specifically still use the basic Motronic but disconnect the "boost control" part of the system and use a boost controller to run a fixed MAXIMUM. This way of doing things obviously works, but it misses out on the benefits of the Motronic controlling boost which is mainly the overboost facility where the Motronic will allow more boost according to inputs (mainly temperature and fuel dependant) and offers more safety features to protect your engine (like backing off the boost in certain critical conditions) - your engine will not grenade without this feature as it has other ways (other than boost control) of protecting itself.
08-07-2003, 10:00 AM
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Originally posted by TB993tt
Q
The factory Motronic system varies the boost according to inputs - IMHO this is the best system for the 993tt engine. My reprogrammed dyno developed Motronic allows as much as 1.6bar (proper head sealing and twin plug is needed for these sort of levels) around 4500rpm (in 5th/6th gear) levelling down to 1 bar around peak power.
If you are using a fixed boost level then you are missing out on much of what the factory intended.
Q
The factory Motronic system varies the boost according to inputs - IMHO this is the best system for the 993tt engine. My reprogrammed dyno developed Motronic allows as much as 1.6bar (proper head sealing and twin plug is needed for these sort of levels) around 4500rpm (in 5th/6th gear) levelling down to 1 bar around peak power.
If you are using a fixed boost level then you are missing out on much of what the factory intended.
the management I am using interfaces with the motoroic, so no loss of factory features...
..I hope
viperbob
thanks
08-08-2003, 06:45 PM
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We are really asking two questions:
1. What is the maximum safe boost level?
2. How much boost should I run on a K24?
1. Safe boost levels really depend on many factors such as the fuel quality, the turbos you are running and how efficient they are, how cool your intake charges are, timing, etc.
What we really want to know is how much boost can we run without knocking? I think on pump gas you really cannot run more then 1.2bar on a stock setup. I should say that this will also be less then ideal since the motor will probably be pulling timing to avoid detonation.
Higher boost has a correlation to airflow. However, depending on your turbo, air temps and altitude there is a point where a turbo becomes ‘maxed out’ and once a turbo is in a overspeed condition it becomes incapable of moving more air regardless of the boost level. Furthermore, when the blades go hypersonic, they become less efficient and the compressor actually falls outside of the efficiency range. This adds heat to the intake charge.
2. According to my data logs I have seen 49-50#/min airflow from K24s turbos between 1.1-1.25bar under fairly warm conditions. Kevin, our resident turbo guru has told me that they can flow about 25#/min so this leads me to believe that the max boost we can effectively run on K24s is about 1.2bar.
Tb993tt has a good point about Motronic boost control. In general you can run more boost at lower rpms where there is less airflow – this puts less stress on the motor.
Another point in addition is the ability of the ecu to adjust boost levels based on airflow. Since the factory ecu knows the airflow and other factors it has total control over the wastegates (boost control). Therefore the ecu can adjust boost levels by choosing different maps to achieve the maximum airflow under a variety of conditions. Some Japanese ecus take this a step further. They are actually boost aware meaning that they actually know the amount of boost pressure in the engine so they can use this information in order to achieve desired boost levels. Most external boost controllers cannot control boost on such a plane since they are not aware of all the other conditions at play here. There are advantages and disadvantages to both these routes in the sense that there are compromises.
1. What is the maximum safe boost level?
2. How much boost should I run on a K24?
1. Safe boost levels really depend on many factors such as the fuel quality, the turbos you are running and how efficient they are, how cool your intake charges are, timing, etc.
What we really want to know is how much boost can we run without knocking? I think on pump gas you really cannot run more then 1.2bar on a stock setup. I should say that this will also be less then ideal since the motor will probably be pulling timing to avoid detonation.
Higher boost has a correlation to airflow. However, depending on your turbo, air temps and altitude there is a point where a turbo becomes ‘maxed out’ and once a turbo is in a overspeed condition it becomes incapable of moving more air regardless of the boost level. Furthermore, when the blades go hypersonic, they become less efficient and the compressor actually falls outside of the efficiency range. This adds heat to the intake charge.
2. According to my data logs I have seen 49-50#/min airflow from K24s turbos between 1.1-1.25bar under fairly warm conditions. Kevin, our resident turbo guru has told me that they can flow about 25#/min so this leads me to believe that the max boost we can effectively run on K24s is about 1.2bar.
Tb993tt has a good point about Motronic boost control. In general you can run more boost at lower rpms where there is less airflow – this puts less stress on the motor.
Another point in addition is the ability of the ecu to adjust boost levels based on airflow. Since the factory ecu knows the airflow and other factors it has total control over the wastegates (boost control). Therefore the ecu can adjust boost levels by choosing different maps to achieve the maximum airflow under a variety of conditions. Some Japanese ecus take this a step further. They are actually boost aware meaning that they actually know the amount of boost pressure in the engine so they can use this information in order to achieve desired boost levels. Most external boost controllers cannot control boost on such a plane since they are not aware of all the other conditions at play here. There are advantages and disadvantages to both these routes in the sense that there are compromises.
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08-09-2003, 10:17 AM
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TB993TT
Thanks for the explanation. I was under the very basic understanding that the more exhaust gas the more boost up to a certain point. I did not realize that this was mapped by the ecu at different rpm levels based on demand or input.
Thanks for the explanation. I was under the very basic understanding that the more exhaust gas the more boost up to a certain point. I did not realize that this was mapped by the ecu at different rpm levels based on demand or input.
08-09-2003, 11:25 AM
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Originally posted by viperbob
TB,
Where have you been?? I've been waiting for the Gruppe M intake photos on your car......
TB,
Where have you been?? I've been waiting for the Gruppe M intake photos on your car......
Car went in to shop for Gruppe M install + investigation of smoking on cold start. It has been 3 weeks now and apparently the Gruppe M intake fitted with a little tweaking. My turbos have been sent for investigation and apparently part of them is worn, something to do with the main bearing/shaft that runs between hot and cold side - anyway its another $600 per unit to repair which p!sses me off abit since they were supposedly fully rebuilt only 3K miles ago
Should get it back end of next week and I will post pics then
08-09-2003, 12:57 PM
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TB,
Sorry to hear about your car. Hopefully you can get it back soon to enjoy the horrible heat wave over there.
Can't wait to see the photos. That will make my decision on what to do with the cold air intake for my car.
See ya..
Sorry to hear about your car. Hopefully you can get it back soon to enjoy the horrible heat wave over there.
Can't wait to see the photos. That will make my decision on what to do with the cold air intake for my car.
See ya..
08-09-2003, 01:21 PM
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TB;
You need to get the shaft specs and you need to be firm with your builder to narrow the ring gap measurement on your turbine side sealing ring. Run it between .001-.002 not at the .006 that comes out of the factory! In order to do that you have to custom file the oversized sealing ring to fit the bearing bore. We make our own rings. I will send you a few sets for free, you pay for DHL....... This is a very common problem! Ask for the measurements, bore sizes, shaft sizes, ring gaps on both sides. Is you shaft Blue.... How much heat tranfer do you have?
You need to get the shaft specs and you need to be firm with your builder to narrow the ring gap measurement on your turbine side sealing ring. Run it between .001-.002 not at the .006 that comes out of the factory! In order to do that you have to custom file the oversized sealing ring to fit the bearing bore. We make our own rings. I will send you a few sets for free, you pay for DHL....... This is a very common problem! Ask for the measurements, bore sizes, shaft sizes, ring gaps on both sides. Is you shaft Blue.... How much heat tranfer do you have?
08-09-2003, 02:55 PM
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Originally posted by Kevin
TB;
You need to get the shaft specs and you need to be firm with your builder to narrow the ring gap measurement on your turbine side sealing ring. Run it between .001-.002 not at the .006 that comes out of the factory! In order to do that you have to custom file the oversized sealing ring to fit the bearing bore. We make our own rings. I will send you a few sets for free, you pay for DHL....... This is a very common problem! Ask for the measurements, bore sizes, shaft sizes, ring gaps on both sides. Is you shaft Blue.... How much heat tranfer do you have?
TB;
You need to get the shaft specs and you need to be firm with your builder to narrow the ring gap measurement on your turbine side sealing ring. Run it between .001-.002 not at the .006 that comes out of the factory! In order to do that you have to custom file the oversized sealing ring to fit the bearing bore. We make our own rings. I will send you a few sets for free, you pay for DHL....... This is a very common problem! Ask for the measurements, bore sizes, shaft sizes, ring gaps on both sides. Is you shaft Blue.... How much heat tranfer do you have?
I appreciate the info and the offer
The turbos are already done and back with my shop, I will consult you next time they need work, at the current rate it probably won't be too long 