Forced Induction and SwapsPost information/questions about Forced Induction methods (Turbos & Nitrous Oxide) and swaps here.
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Ok all of you boosted fanatics! I received my digimoto ODBII scantool today and did a little playing around / investigating! For those of you who did not know I bought the digimoto datalogger / scantool for my laptop (http://www.digimoto.com). Only cost $100, and its a great deal because it does dynos as well (sort of like G-tech).
I drove around with my laptop logging data. Here are some results. The ECU goes into OPEN LOOP mode only on three different occasions:
1. Under accelleration, if the engine load is great enough the ECU will go into open loop. I don't know how great the load has to be, but under soft acceleration the scantool said the ECU remained in closed loop. Only when I applied a more vigorous throttle did the ECU go into open loop. My guess is that it is using feedback control analysis (ie, if the car load is a certain % or the RPM vs vehicle speed is greater than a certain # the ECU will revert to open loop).
2. Upon ANY deceleration. If you are driving, and take your foot off the gas, the ECU goes into open loop. Fuel injector duty cycle at this point is 0, the car stops dumping fuel into the cylinders. I'm guessing this is also based on the tach signal, as when I down shifted, the injectors started injecting fuel again.
3. WOT - again, this is sort of like #1.
I also logged fuel trims as well. It appears that our cars attempt to maintain a -10 long term fuel trim. Mine bounced around from -10 to -11 once in a while. The short term fuel trim was all over the place. As I stepped on the gas it would shoot up, meaning rich. As I dropped off of the gas, it went to 0, as it stopped injecting fuel into the engine. This makes me wonder (and wish) that the E-manage could do this based upon RPM signal as well - it can if you plot RPM vs the TPS signal, but I will be basing my fuel injector signals upon boost.....hmmm.
The cool thing about this tool is that it allows you to log the data, and export it as a TXT document. I took the data, cleaned it up a little, and plotted the O2 sensor voltage (from the front O2 sensor) vs the short term fuel trim. The results are interesting! The short term fuel trims mimiced the O2 sensor voltage a bit. The plot shots that when the O2 sensor voltage rises, the fuel trim begins to rise. Like I said before, the STFT is all over the grid - but its mostly centered around -10 to -15 A/F.
I plan on trying to log some more before installing my turbo to see exactly where things are beforehand......
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sweet post thanks...there is also a good one at www.scantool.net
Brandon
__________________ Knowledge is the key to success as a racer no matter what your racing preference is: the best drivers know their car intimately and it's a passion only known to them....
someday id like to get one with a small pc in the car perm mounted and be able to display the data via my alpine iva-d900 deck. There are some sweet programs available for free that if your interested ill try to locate them.
__________________ 169.8whp / 154 ft lbs tq @ 7psi with an auto trans! Click Image for my turbo install!
After this, it seems you have a good starting knowledge of how the ECU actually works. There are an amazing amount of fuel enrichment and spark retarding maps in there.....
Just a few things: when on closed throttle, are you implying zero fuel is being delivered? If this were so, you would lose combustion... There is gas, albeit very little, being put into the motor upon deceleration... Think about if you ever started a car by popping the clutch while rolling (damn starters)... The throttle is closed, but gas is still getting delivered to start it....
Very good points on open loop, which is what one would be tuning for max power (WOT)... switching between open and closed loop really are based off TPS voltage and motor temp. When you first start a vehicle it starts in open loop until it reaches temp... Again, another fuel and spark curve...
Closed loop maps are very interesting as you can really improve driveability (sp?) on modded motors... You can adjust for things like larger cams, port work, larger injectors, etc.... It helps with things like gas mileage (who cares on honda's, right???), idle surge, fuel pooling on warm starts, etc.....
The A/F ratio is another huge part that the ECU controls.... This is all based on O2 sensor info.... Think of how any A/F meter works (voltage changes in O2 sensor).... Again, based on O2 voltage, the ECU can adjust fuel and spark to compensate....
Keep up the learning, there are tons of sites out there with this type of ECU info, including maps....
Originally posted by Havok2k1 After this, it seems you have a good starting knowledge of how the ECU actually works. There are an amazing amount of fuel enrichment and spark retarding maps in there.....
Just a few things: when on closed throttle, are you implying zero fuel is being delivered? If this were so, you would lose combustion... There is gas, albeit very little, being put into the motor upon deceleration... Think about if you ever started a car by popping the clutch while rolling (damn starters)... The throttle is closed, but gas is still getting delivered to start it....
According to the Helms manual, upon decelleration the fuel injectors shut off - to conserve fuel. logging with this confirms it (as well as the E-manage, which can track injector duty cycle whereas this cannot directly monitor the injector duty cycle).
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Very good points on open loop, which is what one would be tuning for max power (WOT)... switching between open and closed loop really are based off TPS voltage and motor temp. When you first start a vehicle it starts in open loop until it reaches temp... Again, another fuel and spark curve...
Yes and no. The Scantool even says - whether its in open loop or closed loop, due to driving conditions such as accel or decel. The IAT pretty much remained the same throughout the test. It varied by about 10 degrees at most. At idle I measured 190....It appears that the ECU takes into account a few of the sensors, such as TPS, RPMs, and Speed. This may all correllate to how it calculates the engine loading, which in the end could determine the actual transfer from closed loop to open loop.
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Closed loop maps are very interesting as you can really improve driveability (sp?) on modded motors... You can adjust for things like larger cams, port work, larger injectors, etc.... It helps with things like gas mileage (who cares on honda's, right???), idle surge, fuel pooling on warm starts, etc.....
Actually it is open loop maps you are thinking about - the ECU will run in open loop when the car is cold (ie as you stated before - until it reaches operating temperature). It does not depend on the readings from the front O2 sensor at this time, only the hard programmed fuel maps. Once it reaches optimal conditions it jumps to closed loop, which allows the O2 sensor feedback to control fuel (in addition to the other sensors).
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The A/F ratio is another huge part that the ECU controls.... This is all based on O2 sensor info.... Think of how any A/F meter works (voltage changes in O2 sensor).... Again, based on O2 voltage, the ECU can adjust fuel and spark to compensate....
Which is why a wideband is sooooo much better (0 to 5 volt output vs 0 to 1 volt for a narrowband) - much more precise measurements of A/F ratio.
Originally posted by opto_isolator According to the Helms manual, upon decelleration the fuel injectors shut off - to conserve fuel. logging with this confirms it (as well as the E-manage, which can track injector duty cycle whereas this cannot directly monitor the injector duty cycle).
But if you have no fuel, how can your motor continue to run? If there is no fuel, there is no combustion--no combustion means the crank is not rotating or you are seriously leaning out. You know that if you have-say 730 rpm while in idle or anytime that the clutch is depressed then you have to have crank rotation. The crank won't spin on it's own, it has to have combustion.
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Which is why a wideband is sooooo much better (0 to 5 volt output vs 0 to 1 volt for a narrowband) - much more precise measurements of A/F ratio.
I take it you are using the stock narrowband sensor then? I agree 100% on this though, a wideband unit is the optimal piece to use but using a wideband with this datalogger sounds like it would work great. Thanks for the info and review on the part, this can make tuning much easier with a good datlogging tool.
Andyman is correct on the deceleration fuel issue....
On the others, we are essentially saying the same thing...
The IAT has a small portion to do with open and closed loop, the actual engine temp does. This was in reference to the warmup mode you spoke of. Obviously this varies as the termostat and ECU-controlled electric fan will keep operating temp within the specified range...
Again, closed loop comes into play when the vehicle is up to temp and you are driving "normal." Closed loop utilizes more information and therefore you can adjust for daily driveability issue on built motors... Open loop is again only for the situations above which is basically WOT (or close to it) and warmup.... Two compltely different things with two different purposes....
I've been dealing with ECU's fuel, spark, and sensor correlations for 10 years. Obviously not every ECU is exactly the same, yet they all utilize the same set of sensors and principles....
Opto, I think something that you may be overlooking by reading what the Helm's says or what the datalogger is indicating is that it may register at 0 for the injector pulse due to the fact that the amount of fuel consumption is so low that it either registers at 0 or 0 is the amount of the duty cycle for idle or deceleration. Reading at 0 may not necessarrily mean that the injectors are closed but they aren't opening as they would if you were under acceleration.
Originally posted by Havok2k1 Andyman is correct on the deceleration fuel issue....
On the others, we are essentially saying the same thing...
The IAT has a small portion to do with open and closed loop, the actual engine temp does. This was in reference to the warmup mode you spoke of. Obviously this varies as the termostat and ECU-controlled electric fan will keep operating temp within the specified range...
Again, closed loop comes into play when the vehicle is up to temp and you are driving "normal." Closed loop utilizes more information and therefore you can adjust for daily driveability issue on built motors... Open loop is again only for the situations above which is basically WOT (or close to it) and warmup.... Two compltely different things with two different purposes....
As I've stated above, I've noticed that the D17 ECU goes into open loop when the throttle is released, or when there is a large enough difference in speed or load. I've witnessed this. Other ECU's may be different. I can take a picture of it if you want to....The ECU also bases its changeover from open loop to closed loop based on coolant temp.
I am just reading what the manual (and the empirical data) are telling me....Most likely you are correct, the injectors are probably at like a 1% duty cycle.....
ODBII Datalogging experiment 
