Motor upgrade for track days
07-05-2006, 10:17 PM
#46
Nordschleife Master
"No further input from the Motec tuners, so I guess that debate is finished."
This thread seems to have degraded to the point of "pissing into the wind"
This thread seems to have degraded to the point of "pissing into the wind"
07-05-2006, 11:21 PM
#49
Nordschleife Master
FWIW, the OEMs use MAF because they are required to meet emissions regulations for 100k and as the engine wears, the MAF, because it measures the acutal air mass provides the best fuel management for that purpose. When combined with knock detection and closed loop lambda, they are able to meet fuel economy and emissions requirements. In the performance world, objectives are different which is why you see Alpha-N and MAP used over MAF.
07-06-2006, 10:55 AM
#50
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Geoffrey,
I certainly dont want to drag this out just for the sake of it !
MAF measures actual air mass so the optimum fuel can be added under all conditions ?
Knock is a powerful motor safety aid and allows running ignition timing right up to the edge of detonation for optimum ignition timing and therefore power ?
Closed loop lamda holds the fuelling at a very reasonable level under part load conditions . Motronic, like Motec, ignores lamda at full load so that maximum power can be obtained .
If desired 964 Motronic can be run open loop under all conditions.
Your race motor is running completely seperate intake runners for each cylinder so Alpha N is the obvious choice.
What puzzles me is the claim that Motec can do something so different compared to Motronic on a standard intake 964 motor !
I cannot see any fuel or ignition parameter that cannot be replicated with the standard Motronic.I was hoping you would tell me where I was wrong !!
All the best
Geoff
I certainly dont want to drag this out just for the sake of it !
MAF measures actual air mass so the optimum fuel can be added under all conditions ?
Knock is a powerful motor safety aid and allows running ignition timing right up to the edge of detonation for optimum ignition timing and therefore power ?
Closed loop lamda holds the fuelling at a very reasonable level under part load conditions . Motronic, like Motec, ignores lamda at full load so that maximum power can be obtained .
If desired 964 Motronic can be run open loop under all conditions.
Your race motor is running completely seperate intake runners for each cylinder so Alpha N is the obvious choice.
What puzzles me is the claim that Motec can do something so different compared to Motronic on a standard intake 964 motor !
I cannot see any fuel or ignition parameter that cannot be replicated with the standard Motronic.I was hoping you would tell me where I was wrong !!
All the best
Geoff
07-06-2006, 12:16 PM
#51
Nordschleife Master
Geoff,
Lets talk specific to the 964.
A) The 964 measures air flow, not air mass. It has an Air Temp sensor that allows for some compensation based on air temp. It does not compensate for altitude. In my opinion, air flow is the least accurate method of metering fuel and certainly is not the best indication of engine load for ignition timing.
B) Knock is a powerful safety aid for sure. However, it still allows knock, and in the 964 implementation uses early technology and will only REDUCE ignition timing from the stock table. It does not work to find the optimum ignition timing like the latest ECUs in 2006 cars. The main ignition tables in the 964 Motronics are set conservatively for a specific fuel quality, 91 octane here in the US. Running 93 octane will not add performance, nor is the ECU capable of recongizing and advancing the ignition timing. In order to improve performance for higher fuel quality, or to run the engine more towards the edge, the main ignition table needs to be changed. This is effectively the difference between a 964 Cup chip and a standard 964 C2/C4 chip. Detonation is never a good thing in my opinion and knock sensors do allow a small amount of knock.
With MoTeC, there is a knock sensor option, however, I opted not to install this with my new engine. I used a dyno with steady state capability to determine the minimum timing value that would produce the maximum amount of torque in each cell of the ignition table. I know my engine will not detonate with these values and I know it is producing the maximum amount of torque it can. There is no additional performance to be gained with my engine (or any engine I tune) from ignition timing. It will also not detonate either as long as the exact same fuel is used. In my race car, I use 93 octane Mobil fuel from the same gas station so I feel fairly confident that it will be fine. Would it work the same with Shell 93 or Hess 93? I don't know and wouldn't try it. I ran my 700hp 911 turbo this way for 8 years at various boost pressures and had no issues of detonation, and it ran on Sunoco 94 in the early years when it was available in NY, and retuned later for Mobil 93 when Sunoco was no longer available.
B) Closed loop lambda in the 964 is designed to keep the engine running at 14.7:1 AFR for emissions reasons and for the cat converer performance and longevity. It uses a narrow band sensor which is only accurate between about 14:1 and 15.2:1. It cannot be used to properly meter fuel under all conditions because it does not have enough accuracy beyond the ranges listed above. Under full power the 964 engine needs to be in the 13.2:1 AFR range to keep from melting itself. MoTeC uses a wide band lambda sensor and can use 1 of three different types with a response range from 100ms to 500ms between the three. You can use the MoTeC to perform wide band lambda control under all engine operating conditions including full throttle. However, this does not alleviate the tuner from producing a main fuel table that is near perfect to begin with. It is not a band-aid for poor tuning practices. The GT3RSRs use the same Bosch LSU4 as one of the MoTeC Wide Band options. Power is not going to vary much between different AFRs within range. In other words, the engine will make the same power at 13:1 as it does at 13.5:1 AFR. The excess fuel is used only for cooling. I do not use closed loop lambda control and my engines run stable AFRs because I have taken the time to properly tune the main fuel tables and compensation tables. I don't run closed loop because if a lambda sensor goes bad, it will provide erroneous information to the ECU and I don't want to take that chance. I have not had a lambda sensor go bad though.
C) Fundamentally, Motronics has similar capability as MoTeC. MoTeC is newer than the 964 Motronics and has better table resolution, more features, and enhanced technology. However, they both use tables to control the engine. The difference is that the Motronics is designed for an Air Flow Meter where MoTeC can use a variety of different strategies and with the 964 engine in stock form, I would use TPS with Manifold Absolute Pressure (MAP) compensation, exactly as I have done with my race engine. For ignition timing, MAP/Barometric Pressure (BAP) is used which I believe is a better indication of load than an air flow meter and compensates for altitude and weather conditions. This allows for better ignition timing control and does not have the air flow meter in the air stream which is a restriction any way you look at it. An engine is an air pump and the more air that you can pull into the cylinder, the more power it will make. Any restriction will hurt power.
All of the above has been said before in this thread and others.
Lets talk specific to the 964.
A) The 964 measures air flow, not air mass. It has an Air Temp sensor that allows for some compensation based on air temp. It does not compensate for altitude. In my opinion, air flow is the least accurate method of metering fuel and certainly is not the best indication of engine load for ignition timing.
B) Knock is a powerful safety aid for sure. However, it still allows knock, and in the 964 implementation uses early technology and will only REDUCE ignition timing from the stock table. It does not work to find the optimum ignition timing like the latest ECUs in 2006 cars. The main ignition tables in the 964 Motronics are set conservatively for a specific fuel quality, 91 octane here in the US. Running 93 octane will not add performance, nor is the ECU capable of recongizing and advancing the ignition timing. In order to improve performance for higher fuel quality, or to run the engine more towards the edge, the main ignition table needs to be changed. This is effectively the difference between a 964 Cup chip and a standard 964 C2/C4 chip. Detonation is never a good thing in my opinion and knock sensors do allow a small amount of knock.
With MoTeC, there is a knock sensor option, however, I opted not to install this with my new engine. I used a dyno with steady state capability to determine the minimum timing value that would produce the maximum amount of torque in each cell of the ignition table. I know my engine will not detonate with these values and I know it is producing the maximum amount of torque it can. There is no additional performance to be gained with my engine (or any engine I tune) from ignition timing. It will also not detonate either as long as the exact same fuel is used. In my race car, I use 93 octane Mobil fuel from the same gas station so I feel fairly confident that it will be fine. Would it work the same with Shell 93 or Hess 93? I don't know and wouldn't try it. I ran my 700hp 911 turbo this way for 8 years at various boost pressures and had no issues of detonation, and it ran on Sunoco 94 in the early years when it was available in NY, and retuned later for Mobil 93 when Sunoco was no longer available.
B) Closed loop lambda in the 964 is designed to keep the engine running at 14.7:1 AFR for emissions reasons and for the cat converer performance and longevity. It uses a narrow band sensor which is only accurate between about 14:1 and 15.2:1. It cannot be used to properly meter fuel under all conditions because it does not have enough accuracy beyond the ranges listed above. Under full power the 964 engine needs to be in the 13.2:1 AFR range to keep from melting itself. MoTeC uses a wide band lambda sensor and can use 1 of three different types with a response range from 100ms to 500ms between the three. You can use the MoTeC to perform wide band lambda control under all engine operating conditions including full throttle. However, this does not alleviate the tuner from producing a main fuel table that is near perfect to begin with. It is not a band-aid for poor tuning practices. The GT3RSRs use the same Bosch LSU4 as one of the MoTeC Wide Band options. Power is not going to vary much between different AFRs within range. In other words, the engine will make the same power at 13:1 as it does at 13.5:1 AFR. The excess fuel is used only for cooling. I do not use closed loop lambda control and my engines run stable AFRs because I have taken the time to properly tune the main fuel tables and compensation tables. I don't run closed loop because if a lambda sensor goes bad, it will provide erroneous information to the ECU and I don't want to take that chance. I have not had a lambda sensor go bad though.
C) Fundamentally, Motronics has similar capability as MoTeC. MoTeC is newer than the 964 Motronics and has better table resolution, more features, and enhanced technology. However, they both use tables to control the engine. The difference is that the Motronics is designed for an Air Flow Meter where MoTeC can use a variety of different strategies and with the 964 engine in stock form, I would use TPS with Manifold Absolute Pressure (MAP) compensation, exactly as I have done with my race engine. For ignition timing, MAP/Barometric Pressure (BAP) is used which I believe is a better indication of load than an air flow meter and compensates for altitude and weather conditions. This allows for better ignition timing control and does not have the air flow meter in the air stream which is a restriction any way you look at it. An engine is an air pump and the more air that you can pull into the cylinder, the more power it will make. Any restriction will hurt power.
All of the above has been said before in this thread and others.
07-06-2006, 01:22 PM
#52
Three Wheelin'
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Geoffrey,
The 964 Motronic does not use lamda at full load . Fuelling is completely under the tuners control as is Ignition timing. The number of points in the look up tables can be made of any practical size with break points to suite.Whether the 964 knock system operates or not is a question of fuel quality and ignition timing mapping .
Agreed that the flow meter just looks nasty in airflow terms but does a reasonable job .It can be replaced by a Hot Film mass sensor .
I guess this is a "each to his own " situation !!
I know a few serious tuners who are delighted with Motec mainly because they are 100% on top of the system mapping .Makes sense.
All the best
Geoff
The 964 Motronic does not use lamda at full load . Fuelling is completely under the tuners control as is Ignition timing. The number of points in the look up tables can be made of any practical size with break points to suite.Whether the 964 knock system operates or not is a question of fuel quality and ignition timing mapping .
Agreed that the flow meter just looks nasty in airflow terms but does a reasonable job .It can be replaced by a Hot Film mass sensor .
I guess this is a "each to his own " situation !!
I know a few serious tuners who are delighted with Motec mainly because they are 100% on top of the system mapping .Makes sense.
All the best
Geoff