Discussion
Hi experts, since I am still mapping my engine, I noticed that it significantly runs better with lambda values around 0,85 and 0.9. Especially under hard accelerating closded loop lambda 1 is not really working at all. I also got the idea that the lambda values can not really the fast changes when accelerating, more likely they work if the engine is in a more stable RPM condition ?
For cruising on highways lambda 1.0 is no problem and works well. I am using a DTAFAST S80 with MAP as load. It seems that oem motor controllers have a lot more control in them since I think I am reaching a limit with the S80 that is not really as smooth as I am used from production cars. Not that I have a problem with it, but since I am no expert, I would really like to know if I am close to what can be achieved with a motorsport oriented ECU. I must say also under hard acceleration the 0,87 - 0.9 delivers best results.
I have now a powerful map which makes me thinking how much longer before the car is killing me and I have a dash switch that lets me enter closed loop for traffic and highway cruising. Probably the best idea to have both option, maximum power and maximum economy with this setup ?
Comments ?
For cruising on highways lambda 1.0 is no problem and works well. I am using a DTAFAST S80 with MAP as load. It seems that oem motor controllers have a lot more control in them since I think I am reaching a limit with the S80 that is not really as smooth as I am used from production cars. Not that I have a problem with it, but since I am no expert, I would really like to know if I am close to what can be achieved with a motorsport oriented ECU. I must say also under hard acceleration the 0,87 - 0.9 delivers best results.
I have now a powerful map which makes me thinking how much longer before the car is killing me and I have a dash switch that lets me enter closed loop for traffic and highway cruising. Probably the best idea to have both option, maximum power and maximum economy with this setup ?
Comments ?
Closed loop is only possible in constant mode, maximum to 4000rpm.
Accelerating, above 4000rpm closed loop is rubbish and will probably do more harm then good if you tried because it will lean the conditions too much.
I think that even a Prius doesn't run closed loop all the time when the engine is running.
Don't know the DTA, but with my Motec I can just switch between closed loop and open loop.
Forget about the tweaking when the car runs as you expect.
Accelerating, above 4000rpm closed loop is rubbish and will probably do more harm then good if you tried because it will lean the conditions too much.
I think that even a Prius doesn't run closed loop all the time when the engine is running.
Don't know the DTA, but with my Motec I can just switch between closed loop and open loop.
Forget about the tweaking when the car runs as you expect.
Firstly, what type of lambda sensors do you run?
The options are "narrow band = switching type" and "wide band = pump current type".
The narrow band sensors can only recognise the exhaust AFR switching either side of stoichiometric (lambda = 1, and for most normal road fuels an AFR of approx 14.7 : 1)
The wide band type output a signal in proportion to exhaust AFR, and so can be used to control AFR (in a "closed loop" fashion) to values other than Lambda 1.
Lambda 1, where exactly enough fuel is added for every last air molecule to meet and oxidise a corresponding fuel molecule is an optimum condition for general light load operation. It produces lowish exhaust polutant emissions, and returns decent fuel economy (ideally, you would run lean of lambda 1 for ultimate fuel economy, but emissions of NOx increase rapidly and catalyse performance falls rapidly, so OEM vehicles cannot take benefit of this, although a "home mapped" car can ;-)
Once you ask for significant torque output from the engine, then you will aim to run rich. Again, typically, for a normally aspirated engine, running at approx 0.85 to 0.9 lambda when manifold pressures rise above approx 60-65kpa (>65% of max load). This richer condition allows more complete utilisation of the airmass within the combustion chamber and hence provides more torque.
Further enrichment beyond approx Lambda 0.85 may be necessry as engine speeds increase in order to limit component thermal loadings. As you inject more fuel, more heat is removed from the air charge as said fuel evaporates, lowering combustion temperatures.
For an OEM vehicle, typically running will broadly be split into the following areas:
1) light load / emissions regions = Lambda 1
2) >65% load & < approx 4500rpm = LBT (lean best torque, typically 0.87 lambda)
3) >65% load & >4500rpm = Thermal limit enrichment (as rich as 0.7 lambda on some engines with close coupled catalysts)
If you are mapping your own engine, then i would suggest some exhaust port (and pre cat if you have them) thermocouples are used to monitor EGT's at high loadings to identify the area when thermal loading become excessive.
Further to all this, the effects of ignition timing at crucial. Enrichment and hence cooling of the charge results in the possibility to advance ignition angle, (and vise-versa). Most engines i see that seem "flat" are due to a lack of ignition advance rather than a lack of fuel.
SO:
If you have wide band lamda sensors, you can ask (and get) and sensible AFR target whilst staying in "closed loop fuel control", however if you have narrow band sensors, you must exit closed loop fuelling as soon as you need to enrich the mixture away from lambda 1.
The options are "narrow band = switching type" and "wide band = pump current type".
The narrow band sensors can only recognise the exhaust AFR switching either side of stoichiometric (lambda = 1, and for most normal road fuels an AFR of approx 14.7 : 1)
The wide band type output a signal in proportion to exhaust AFR, and so can be used to control AFR (in a "closed loop" fashion) to values other than Lambda 1.
Lambda 1, where exactly enough fuel is added for every last air molecule to meet and oxidise a corresponding fuel molecule is an optimum condition for general light load operation. It produces lowish exhaust polutant emissions, and returns decent fuel economy (ideally, you would run lean of lambda 1 for ultimate fuel economy, but emissions of NOx increase rapidly and catalyse performance falls rapidly, so OEM vehicles cannot take benefit of this, although a "home mapped" car can ;-)
Once you ask for significant torque output from the engine, then you will aim to run rich. Again, typically, for a normally aspirated engine, running at approx 0.85 to 0.9 lambda when manifold pressures rise above approx 60-65kpa (>65% of max load). This richer condition allows more complete utilisation of the airmass within the combustion chamber and hence provides more torque.
Further enrichment beyond approx Lambda 0.85 may be necessry as engine speeds increase in order to limit component thermal loadings. As you inject more fuel, more heat is removed from the air charge as said fuel evaporates, lowering combustion temperatures.
For an OEM vehicle, typically running will broadly be split into the following areas:
1) light load / emissions regions = Lambda 1
2) >65% load & < approx 4500rpm = LBT (lean best torque, typically 0.87 lambda)
3) >65% load & >4500rpm = Thermal limit enrichment (as rich as 0.7 lambda on some engines with close coupled catalysts)
If you are mapping your own engine, then i would suggest some exhaust port (and pre cat if you have them) thermocouples are used to monitor EGT's at high loadings to identify the area when thermal loading become excessive.
Further to all this, the effects of ignition timing at crucial. Enrichment and hence cooling of the charge results in the possibility to advance ignition angle, (and vise-versa). Most engines i see that seem "flat" are due to a lack of ignition advance rather than a lack of fuel.
SO:
If you have wide band lamda sensors, you can ask (and get) and sensible AFR target whilst staying in "closed loop fuel control", however if you have narrow band sensors, you must exit closed loop fuelling as soon as you need to enrich the mixture away from lambda 1.
You should be able to set your system to drop out of closed loop under acceleration.
14.7 AFR = Lambda 1 = stoichiometric. This is the best compromise of power, economy, emissions.
For best power you want to be about 12.5 AFR (Lambda .85)
In cruise you may be able to go out to 15.5 AFR (Lambda 1.05)
In overrun go out to 16 AFR or cut fuel completely.
You should be able to map all of these conditions.
Steve
Max T beat me to it and covered it much better.
14.7 AFR = Lambda 1 = stoichiometric. This is the best compromise of power, economy, emissions.
For best power you want to be about 12.5 AFR (Lambda .85)
In cruise you may be able to go out to 15.5 AFR (Lambda 1.05)
In overrun go out to 16 AFR or cut fuel completely.
You should be able to map all of these conditions.
Steve
Max T beat me to it and covered it much better.
Edited by Steve_D on Thursday 29th March 22:47
Further points of note:
1) Closed loop control is just that, a "control" system. it is a response to an error, so cannot be 100% accurate during transient events. You must get the "open loop" mapping accurate first, otherwise the closed loop system will just chase large errors, and the phase lag will lead to all sorts of issues. Read up about PID control for referrence.
2) EGT's vs Rpm: Broadly speaking exhaust gas temperatures in the engine after the power stroke do not vary that much with engine speed. (only a few 10's of degC). What does change is the "temperature duty cycle" which components are exposed to. In effect, at low rpm, there is sufficent time for any given component to radiate or conduct away the heat that is absorbed during the combustion/exhaust event. As rpm rises, more and more heat release events occur per unit of time.
Hence, a thermocouple in the exhaust manifold poking into the gas stream will read just say 600degC at 1500rpm, but over 800degC at 4500rpm. The actual temp of the gas hasn't changed at lot, but the "mean heat flux" which the thermocouple is reading HAS increased (this is due to the cyclic nature of IC engines). As you look at thermocouples further away from the engine, the temps become more constant with rpm as the gas flows become less intermitent (more cylinders contribute). Luckily, we don't actually care what the real gas temp is, only what temperatures components in the engine system reach (eg. combustion chamber gas temps reach well beyond the melting point of the ally cylinder head, but the engine doesn't melt because the "bulk" metal temps do not have time to reach the same temperature (due to their thermal inertia and forced cooling)
3) Catalysts and Exotherm:
Catalysts are "active". They use a catalytic process to convert exhaust pollutants into CO2. This releases heat. When you enrich the engines AFR you cool the exhaust gas stream and lower the catalyst substrate temperature. But, if the catalyst, now loaded with a very rich (lots of unburnt but vapourised hydrocarbons) mixture, is exposed to a sudden lead spike (such as during a deccel fuel shut off event) that catalyst can exotherm. In effect, a runway catalyitic reaction, that can cause temperatures to spike well above 1200degC. This can easily damage the cataylst substrate. On production cars, DFSO (Deccel Fuelling Shut Off) is suspended when Cat temps exceed certain limits.
1) Closed loop control is just that, a "control" system. it is a response to an error, so cannot be 100% accurate during transient events. You must get the "open loop" mapping accurate first, otherwise the closed loop system will just chase large errors, and the phase lag will lead to all sorts of issues. Read up about PID control for referrence.
2) EGT's vs Rpm: Broadly speaking exhaust gas temperatures in the engine after the power stroke do not vary that much with engine speed. (only a few 10's of degC). What does change is the "temperature duty cycle" which components are exposed to. In effect, at low rpm, there is sufficent time for any given component to radiate or conduct away the heat that is absorbed during the combustion/exhaust event. As rpm rises, more and more heat release events occur per unit of time.
Hence, a thermocouple in the exhaust manifold poking into the gas stream will read just say 600degC at 1500rpm, but over 800degC at 4500rpm. The actual temp of the gas hasn't changed at lot, but the "mean heat flux" which the thermocouple is reading HAS increased (this is due to the cyclic nature of IC engines). As you look at thermocouples further away from the engine, the temps become more constant with rpm as the gas flows become less intermitent (more cylinders contribute). Luckily, we don't actually care what the real gas temp is, only what temperatures components in the engine system reach (eg. combustion chamber gas temps reach well beyond the melting point of the ally cylinder head, but the engine doesn't melt because the "bulk" metal temps do not have time to reach the same temperature (due to their thermal inertia and forced cooling)
3) Catalysts and Exotherm:
Catalysts are "active". They use a catalytic process to convert exhaust pollutants into CO2. This releases heat. When you enrich the engines AFR you cool the exhaust gas stream and lower the catalyst substrate temperature. But, if the catalyst, now loaded with a very rich (lots of unburnt but vapourised hydrocarbons) mixture, is exposed to a sudden lead spike (such as during a deccel fuel shut off event) that catalyst can exotherm. In effect, a runway catalyitic reaction, that can cause temperatures to spike well above 1200degC. This can easily damage the cataylst substrate. On production cars, DFSO (Deccel Fuelling Shut Off) is suspended when Cat temps exceed certain limits.
Thanks a lot, you really have confirmed what I noticed during mapping the car. I have wideband and I am also running a target lambda
table, that I will make a little richer to the end of what you have told me about top end lambda to be more like 0,7.
I have turned the transients off to map the engine without fuel enrichment and also have the closed loop deactivated. It seems that I am finally coming there, it is really like "give the engine what he wants......".
I can also confirm that with a lambda reading around the 0,85 it feels like giving the best torque !
I have quite some advancing and recently tried 5 degrees more than there was initially, and I really could tell the torque increase, have now retarted it back by 3 degrees as the sound was quite harsh. I must say the car still can easily can kill in its current setup, so enough for me........rather give the engine a little less stress.
table, that I will make a little richer to the end of what you have told me about top end lambda to be more like 0,7.
I have turned the transients off to map the engine without fuel enrichment and also have the closed loop deactivated. It seems that I am finally coming there, it is really like "give the engine what he wants......".
I can also confirm that with a lambda reading around the 0,85 it feels like giving the best torque !
I have quite some advancing and recently tried 5 degrees more than there was initially, and I really could tell the torque increase, have now retarted it back by 3 degrees as the sound was quite harsh. I must say the car still can easily can kill in its current setup, so enough for me........rather give the engine a little less stress.
I have to add it is and was a great pleasure to make my own tune on the ECU as I have learned quite a lot doing so, just to give you an idea, already clocked 6060km on the odometer and still mapping the engine......that also includeds start fueling conditions and other settings.
It is a pity that Stoneleigh is such a long drive.....would kill me in the Ultima from Germany. I would love to hear the expert opinions on the mapping and power of the car.
It is a pity that Stoneleigh is such a long drive.....would kill me in the Ultima from Germany. I would love to hear the expert opinions on the mapping and power of the car.
Running excessively rich (0.7 lambda) at high engine speeds will deffinately hurt your engines power output. Peak power, like peak torque generally occur at LBT (0.85lambda) unless heavily detonation limited (for example a forced induction engine).
But, if you have to run rich to prevent parts failing, then you have no option (this is the case for OEM's. They must overfuel to achieve the necessary durability. A lot of aftermarket tuners simply take all the fuel out, find a couple more bhp, and say "silly manufacturers, why do they put all the "excess" fuel in ??". In reality that excess fuel is there to allow the cataylst system to still meet the 160,000Km durability requirements (basically, the manufacturer must demonstrate that the catalyst efficiency does not degrade excessively as the car ages) These effects typically start to occur well before more obvious ones such as exhaust valve failure due to overtemp etc.
As a personal and specialised car, you may choose to accept some ultimate durability reduction to return a higher power output. Only you can decide this trade off. However, the first step is to know where you are actually running, hence the recommendation for exhaust tmeperature monitoring !
(for some reason, loads of people now fit AFR meters, but very few EGT sensing, which is just as important)
If i had to stick a finger in the air, running approx 0.75 lambda at peak power rpm would be a reasonable place to start with an NA engine. You are not so far down the excess fuel/reduced torque curve to be limiting power significantly, but you have some protection due to the rich mixture.
The other advantage of running rich is one of accuracy and repeatability. Generally speaking again, aftermarket and tuned cars will not have the precision and repeatability of an OEM calibrated one. This leads to larger uncorrected lambda excursions, so if you start a bit rich, you have a safety net in place to buffer any unexpected lean spikes.
A final note of caution. Lambda sensors read "excess oxygen" not "excess fuel" so when running rich (generally below approx 0.65Lambda) they tend to become inaccurate (as there is so little oxygen remaining in the exhaust to measure). A typical NA engine will experience a rich misfire below ~0.6 Lambda, and i have seen engines doing this even when the lambda sensor is reporting things as much leaner than they really are.
But, if you have to run rich to prevent parts failing, then you have no option (this is the case for OEM's. They must overfuel to achieve the necessary durability. A lot of aftermarket tuners simply take all the fuel out, find a couple more bhp, and say "silly manufacturers, why do they put all the "excess" fuel in ??". In reality that excess fuel is there to allow the cataylst system to still meet the 160,000Km durability requirements (basically, the manufacturer must demonstrate that the catalyst efficiency does not degrade excessively as the car ages) These effects typically start to occur well before more obvious ones such as exhaust valve failure due to overtemp etc.
As a personal and specialised car, you may choose to accept some ultimate durability reduction to return a higher power output. Only you can decide this trade off. However, the first step is to know where you are actually running, hence the recommendation for exhaust tmeperature monitoring !
(for some reason, loads of people now fit AFR meters, but very few EGT sensing, which is just as important)
If i had to stick a finger in the air, running approx 0.75 lambda at peak power rpm would be a reasonable place to start with an NA engine. You are not so far down the excess fuel/reduced torque curve to be limiting power significantly, but you have some protection due to the rich mixture.
The other advantage of running rich is one of accuracy and repeatability. Generally speaking again, aftermarket and tuned cars will not have the precision and repeatability of an OEM calibrated one. This leads to larger uncorrected lambda excursions, so if you start a bit rich, you have a safety net in place to buffer any unexpected lean spikes.
A final note of caution. Lambda sensors read "excess oxygen" not "excess fuel" so when running rich (generally below approx 0.65Lambda) they tend to become inaccurate (as there is so little oxygen remaining in the exhaust to measure). A typical NA engine will experience a rich misfire below ~0.6 Lambda, and i have seen engines doing this even when the lambda sensor is reporting things as much leaner than they really are.
ok thanks I have been told the LS7 will run 0,67 at WOT with the factory ECU.
Since I hardly see WOT at all, WHERE ? I will not go that rich, have no cat installed at all, see attached link to my new exhaust system...............
https://www.youtube.com/watch?v=5gEVgHLL3Y4
Since I hardly see WOT at all, WHERE ? I will not go that rich, have no cat installed at all, see attached link to my new exhaust system...............
https://www.youtube.com/watch?v=5gEVgHLL3Y4
0.67 lambda sounds bang on the money for a US tuned (and CARB/EPA regulated) catalysed production engine.
Without catalysts, and with a low restriction exhaust (like yours) you will find that you can run significantly more ignition advance than the std engine (exhaust backpressure causes exhaust gas residuals to remain in the cylinder, contaminate and heat the incoming fresh charge and result in the early onset of detonation phenomina). This extra advance reduces EGT (as the heat is put into the piston as work rather than being blown out the exhaust, as a greater proportion of the charge is burnt at an earlier crank angle). Typically, for not engines without catalystic converters, runing LBT at peak power is possible (0.85lambda) is you really are chasing ultimate peak power outputs.
You may decide, for reasons i listed earlier, to settle for a more robust and conservative lambda, maybe of approx 0.78 etc.
Without catalysts, and with a low restriction exhaust (like yours) you will find that you can run significantly more ignition advance than the std engine (exhaust backpressure causes exhaust gas residuals to remain in the cylinder, contaminate and heat the incoming fresh charge and result in the early onset of detonation phenomina). This extra advance reduces EGT (as the heat is put into the piston as work rather than being blown out the exhaust, as a greater proportion of the charge is burnt at an earlier crank angle). Typically, for not engines without catalystic converters, runing LBT at peak power is possible (0.85lambda) is you really are chasing ultimate peak power outputs.
You may decide, for reasons i listed earlier, to settle for a more robust and conservative lambda, maybe of approx 0.78 etc.
Hello Spatz
-As mentioned by the very knoweldgable contributors before, enriching the Lambda under high load gives the benefit of a cooler combustion process. Another important point is that this has the side benefit of reducing the possibility of Knock. In this vain, its advisable to enrich when running with high intake air temps to reduce the possibility of kocking
-dont forget to retard the igition significantly and run rich with lots of air on trailing throttle, so you get that nice snap crackle and pop sound.
If your lucky and you ECU offers the functionality youll be able to cut off some cylinders as well on the overrun (in a random fashion for the natural sounding effect) and you will get a few bangs too..
PS going to TÜV Lüdwigsburg on Monday to ask about registering a Used UK GTR hier. Any tipps?
Cheers Luke
-As mentioned by the very knoweldgable contributors before, enriching the Lambda under high load gives the benefit of a cooler combustion process. Another important point is that this has the side benefit of reducing the possibility of Knock. In this vain, its advisable to enrich when running with high intake air temps to reduce the possibility of kocking
-dont forget to retard the igition significantly and run rich with lots of air on trailing throttle, so you get that nice snap crackle and pop sound.
If your lucky and you ECU offers the functionality youll be able to cut off some cylinders as well on the overrun (in a random fashion for the natural sounding effect) and you will get a few bangs too..
PS going to TÜV Lüdwigsburg on Monday to ask about registering a Used UK GTR hier. Any tipps?
Cheers Luke
thanks have no tips for that but would be very interested to hear about the experience.
For the misfiring I noticed that if you close throttle from high revs and too lean mixture you get these
pops and bangs whatever you call them quite easily. I added more fuel for high revs and closed throttle to remove
this as I am not sure if this is somehow hurting the engine or throttle body.
For the misfiring I noticed that if you close throttle from high revs and too lean mixture you get these
pops and bangs whatever you call them quite easily. I added more fuel for high revs and closed throttle to remove
this as I am not sure if this is somehow hurting the engine or throttle body.
I run an earlier DTA S80 on my procharged car, Closed loop is according to my tuner a near waste of time (even with Innovate LC1 Lambda sensor controllers on each bank) with the S80, and the wide band control needs to be lied to to get the right result.
I have spent a while with a couple of very reputable tuners and a rolling road getting my car to fuel cleanly, it is all but perfect for me now (cold/hot start,Idle,transition and cruise) but I think another 5 hours or so on the rolling road will nail it properly for the higher boost control.
I have spent a while with a couple of very reputable tuners and a rolling road getting my car to fuel cleanly, it is all but perfect for me now (cold/hot start,Idle,transition and cruise) but I think another 5 hours or so on the rolling road will nail it properly for the higher boost control.
F.C. said:
Closed loop is according to my tuner a near waste of time
Get a better tuner??? ;-)If closed loop control was pointless, why does every single car made after about 1990 now have a lambda sensor in a feed back control loop?
What your tuner may have meant to say is that "without a properly and consitantly calibrated open loop base map, closed loop is a waste of time"
lukeschwartz said:
Hello Spatz
-As mentioned by the very knoweldgable contributors before, enriching the Lambda under high load gives the benefit of a cooler combustion process. Another important point is that this has the side benefit of reducing the possibility of Knock. In this vain, its advisable to enrich when running with high intake air temps to reduce the possibility of kocking
-dont forget to retard the igition significantly and run rich with lots of air on trailing throttle, so you get that nice snap crackle and pop sound.
If your lucky and you ECU offers the functionality youll be able to cut off some cylinders as well on the overrun (in a random fashion for the natural sounding effect) and you will get a few bangs too..
PS going to TÜV Lüdwigsburg on Monday to ask about registering a Used UK GTR hier. Any tipps?
Cheers Luke
Depending on the method with which air temperature correction is applied, you probably have an "enrich with high temp" effect already. High intake charge temperatures reduce air mass (as air density falls), if you inject the same mass of fuel as when at normal air temps then you will automatically have a rich shift. Generally, your air temp correction map for fuel mass would be removing fuel with increasing intake air temp to maintain the same AFR. Some people modify this table with a lower overall gain, so that the system undercompensates for elevated air temperature, and in effect results in a rich shift. If you are running closed loop however, and the lambda target map is not also rich shifted, then the closed loop controller will negate this rich shift.-As mentioned by the very knoweldgable contributors before, enriching the Lambda under high load gives the benefit of a cooler combustion process. Another important point is that this has the side benefit of reducing the possibility of Knock. In this vain, its advisable to enrich when running with high intake air temps to reduce the possibility of kocking
-dont forget to retard the igition significantly and run rich with lots of air on trailing throttle, so you get that nice snap crackle and pop sound.
If your lucky and you ECU offers the functionality youll be able to cut off some cylinders as well on the overrun (in a random fashion for the natural sounding effect) and you will get a few bangs too..
PS going to TÜV Lüdwigsburg on Monday to ask about registering a Used UK GTR hier. Any tipps?
Cheers Luke
Regarding the "snap, crackle, pop" on overrun, this is unlikely to damage your engine. You get this effect when unburnt but vapourised hydrocarbons are ejected into the exhaust, mix with an oxygen rich condition and spontaneously ingite. It can be brought on either by a rich or lean misfire. If you have exhaust catalysts, then it is best avoided to prevent catalyst exotherm from damaging the substrate bricks.
Hello Spatz,
so how did you get your 2 Ultimas registerd?, Rote kennzeichen?, Still with Eng. Registration?, Temporary registration?
Would really appreciate your help Here! (please)
The exhaust bangs shouldnt be a Problem if they are kept to a sensible level. Just observe the AMGs Porsches and Mini Cooper Ss they all do it and have cats.
Luke
so how did you get your 2 Ultimas registerd?, Rote kennzeichen?, Still with Eng. Registration?, Temporary registration?
Would really appreciate your help Here! (please)
The exhaust bangs shouldnt be a Problem if they are kept to a sensible level. Just observe the AMGs Porsches and Mini Cooper Ss they all do it and have cats.
Luke
Max_Torque said:
F.C. said:
Closed loop is according to my tuner a near waste of time
Get a better tuner??? ;-)If closed loop control was pointless, why does every single car made after about 1990 now have a lambda sensor in a feed back control loop?
What your tuner may have meant to say is that "without a properly and consitantly calibrated open loop base map, closed loop is a waste of time"
what I said was: Closed loop is according to my tuner a near waste of time (even with Innovate LC1 Lambda sensor controllers on each bank)with the S80
Max_Torque said:
Regarding the "snap, crackle, pop" on overrun, this is unlikely to damage your engine. You get this effect when unburnt but vapourised hydrocarbons are ejected into the exhaust, mix with an oxygen rich condition and spontaneously ingite. It can be brought on either by a rich or lean misfire. If you have exhaust catalysts, then it is best avoided to prevent catalyst exotherm from damaging the substrate bricks.
Overrun ? is this when you close throttle from high revs ?Gassing Station | Ultima | Top of Page | What's New | My Stuff