mattr66usa
Active Member
Let's keep it technical this time.....
The AO file uses the average knock sensor activity to swing a parameter knows as OAR (octane adjust ratio). It is used heavily on the 15+ trucks but was never utilized the way I use it on the SHO. The parameter selects from 3 boost maps and the way I set it up an oar of -.8 or more gives you maximum boost (UP TO THE LIMIT OF WHAT THE FUEL PUMP SUPPORTS OR YOU RUN OUT OF TURBO FLOW). The fuel pump is the limiting factor at sea level on how much boost can be run. -.8 OAR is about 91 octane and the max it will show is -.96 typically. OAR can be though of as a "long term timing trim" much like the long term fuel trim for the fuel. The knock parameter can be thought of as a short-term timing trim. The reason I allow for the inferred octane to swing the boost mapping is because if you run lots of boost but can't run timing because of bad octane, it will melt the cats in short order. Also boost without timing isn't good for the rest of the engine because of late combustion and lots of exhaust heat.
So... let's say the OAR is maxed out on 93 octane (this means the base spark is maxed as well), the knock sensors have authority to add (up to the set maximum timing at each load/rpm point) or subtract up to 7 degrees of timing over the base map dictated by the OAR base map that is added to the base borderline timing map. But if the knock sensors experience 3 degrees or more of knock for 3 seconds or more it makes adjustments to the OAR parameter. So the next time the engine is at the same load/rpm point, the knock sensor number may not even move. So you get a difference of boost and base timing with changes to inferred octane. It just doesn't rail on the knock sensor at wot like some people insinuate.
So I always tell customers that if they don't have anything more than 91 octane available, they can add 2 gallons to a full tank of premium to boost octane. In some cases, even winter blend or crap 93 octane could use a little bump in octane to achieve maximum performance if desired. This gives a great octane bump and doesn't overtax the fuel system or put metals in the mix like with MMT-based octane boosters that eventually will foul the plugs and converters (reason they removed it from the fuel at the pump a couple of decades ago).
E30-40 tuning is usually only available with a pump upgrade because you have to turn the boost down to support the increased fuel flow needed. Others will tune for E30 on the stock pump and run the same boost as a pump gas tune, but you have to set the lambda leaner, and it just isn't safe to do so IMO. Gearhead's E30 files don't use the OAR so it stays fixed fixed at the maximum inferred octane, but the knock sensors still have the availability to pull timing if necessary. I do very few E30 Files on the stock pump because it's a wash almost and not worth the 10-15 extra hp on the stock pump because of the dangers of getting the mix wrong either way where you are either lacking on octane or over-taxing the fuel system.
So where does methanol injection come into play with Gh Tuning? It depends.... It depends on what the limiting factory is.... Octane, Fuel Flow, or Temperature.
Out of the box, the customer gets a normal AO file to log the meth system with and is told to start small with the meth flow. I like seeing up to a 20% substitution for the fueling maximum on a street car. This is able to be easily compensated for by the wideband O2 sensors that are on the car. Typically however, once the customer reaches maximum octane and cooling level needed for their power level, we talk about pulling meth back if we aren't using the methanol for an additional fuel source because the fuel pump can't keep up with demand without the methanol. Once you reach the maximum octane (MBT timing point) there are only very marginal gains with more meth flow above that.
So what happens on a normal AO file if you inject methanol? if you have enough meth to need fuel pulled out of the engine's injectors, the wideband O2 sensors automatically pull the fuel out, but unless you are using a very large nozzle and non-progressive controller, the measured lambda never gets rich enough to cause any damage to the engine before the O2 sensors have a chance to pull the extra fuel out from coming from the DI fuel injectors on the engine. Typically the stock tune runs down to .78 lambda or so at WOT and tune I run .85 low rpm where the DI injection event is very long then progressing down to .82 as RPM rises this leaner mixture is safe because of the DI's awesome octane tolerance gains. If the lambda is not going richer than factory, how is that hurting the car? But..... eventually the long term fuel trim will absorb the short-term trim and learn the wot mixture requirements and the O2 sensors won't have as much adjustment to do on subsequent WOT blasts. Oh and the lambda value from the O2 sensors' perspective is the same between straight gas and gas mixed with ethanol if anyone was wondering. There is no need for a different commanded lambda when running methanol injection.
Once a datalog is taken with the meth flowing, I look for bank to bank balance (very common problem on these systems) and overall flow then have the customer make adjustments if necessary. Once enough meth exists to take advantage of a timing bump on pump gas for example, I release the knock sensor's ability to add timing up to the MBT point for whatever fuel the car is running on plus the meth. If they are running on E40 and already at MBT timing on stock turbos without methanol, there isn't any more timing or boost to be added with the meth, so in this case the meth flowing is just for some additional cooling in this case. I think this is where my non-customers and some loud voices are confused. It's a pretty simple concept. If fuel flow isn't the limiting factor and you are at MBT timing on the fuel you are running, there aren't much in the way of power gains other than from a major cooling reduction like with a stock intercooler.
Only if the customer decides to use the methanol as an additional fuel source to supplement for a fuel pump that can't keep up will additional boost be added (if additional turbo flow is available) at their request and after careful consideration of the risks.
Matt
The AO file uses the average knock sensor activity to swing a parameter knows as OAR (octane adjust ratio). It is used heavily on the 15+ trucks but was never utilized the way I use it on the SHO. The parameter selects from 3 boost maps and the way I set it up an oar of -.8 or more gives you maximum boost (UP TO THE LIMIT OF WHAT THE FUEL PUMP SUPPORTS OR YOU RUN OUT OF TURBO FLOW). The fuel pump is the limiting factor at sea level on how much boost can be run. -.8 OAR is about 91 octane and the max it will show is -.96 typically. OAR can be though of as a "long term timing trim" much like the long term fuel trim for the fuel. The knock parameter can be thought of as a short-term timing trim. The reason I allow for the inferred octane to swing the boost mapping is because if you run lots of boost but can't run timing because of bad octane, it will melt the cats in short order. Also boost without timing isn't good for the rest of the engine because of late combustion and lots of exhaust heat.
So... let's say the OAR is maxed out on 93 octane (this means the base spark is maxed as well), the knock sensors have authority to add (up to the set maximum timing at each load/rpm point) or subtract up to 7 degrees of timing over the base map dictated by the OAR base map that is added to the base borderline timing map. But if the knock sensors experience 3 degrees or more of knock for 3 seconds or more it makes adjustments to the OAR parameter. So the next time the engine is at the same load/rpm point, the knock sensor number may not even move. So you get a difference of boost and base timing with changes to inferred octane. It just doesn't rail on the knock sensor at wot like some people insinuate.
So I always tell customers that if they don't have anything more than 91 octane available, they can add 2 gallons to a full tank of premium to boost octane. In some cases, even winter blend or crap 93 octane could use a little bump in octane to achieve maximum performance if desired. This gives a great octane bump and doesn't overtax the fuel system or put metals in the mix like with MMT-based octane boosters that eventually will foul the plugs and converters (reason they removed it from the fuel at the pump a couple of decades ago).
E30-40 tuning is usually only available with a pump upgrade because you have to turn the boost down to support the increased fuel flow needed. Others will tune for E30 on the stock pump and run the same boost as a pump gas tune, but you have to set the lambda leaner, and it just isn't safe to do so IMO. Gearhead's E30 files don't use the OAR so it stays fixed fixed at the maximum inferred octane, but the knock sensors still have the availability to pull timing if necessary. I do very few E30 Files on the stock pump because it's a wash almost and not worth the 10-15 extra hp on the stock pump because of the dangers of getting the mix wrong either way where you are either lacking on octane or over-taxing the fuel system.
So where does methanol injection come into play with Gh Tuning? It depends.... It depends on what the limiting factory is.... Octane, Fuel Flow, or Temperature.
Out of the box, the customer gets a normal AO file to log the meth system with and is told to start small with the meth flow. I like seeing up to a 20% substitution for the fueling maximum on a street car. This is able to be easily compensated for by the wideband O2 sensors that are on the car. Typically however, once the customer reaches maximum octane and cooling level needed for their power level, we talk about pulling meth back if we aren't using the methanol for an additional fuel source because the fuel pump can't keep up with demand without the methanol. Once you reach the maximum octane (MBT timing point) there are only very marginal gains with more meth flow above that.
So what happens on a normal AO file if you inject methanol? if you have enough meth to need fuel pulled out of the engine's injectors, the wideband O2 sensors automatically pull the fuel out, but unless you are using a very large nozzle and non-progressive controller, the measured lambda never gets rich enough to cause any damage to the engine before the O2 sensors have a chance to pull the extra fuel out from coming from the DI fuel injectors on the engine. Typically the stock tune runs down to .78 lambda or so at WOT and tune I run .85 low rpm where the DI injection event is very long then progressing down to .82 as RPM rises this leaner mixture is safe because of the DI's awesome octane tolerance gains. If the lambda is not going richer than factory, how is that hurting the car? But..... eventually the long term fuel trim will absorb the short-term trim and learn the wot mixture requirements and the O2 sensors won't have as much adjustment to do on subsequent WOT blasts. Oh and the lambda value from the O2 sensors' perspective is the same between straight gas and gas mixed with ethanol if anyone was wondering. There is no need for a different commanded lambda when running methanol injection.
Once a datalog is taken with the meth flowing, I look for bank to bank balance (very common problem on these systems) and overall flow then have the customer make adjustments if necessary. Once enough meth exists to take advantage of a timing bump on pump gas for example, I release the knock sensor's ability to add timing up to the MBT point for whatever fuel the car is running on plus the meth. If they are running on E40 and already at MBT timing on stock turbos without methanol, there isn't any more timing or boost to be added with the meth, so in this case the meth flowing is just for some additional cooling in this case. I think this is where my non-customers and some loud voices are confused. It's a pretty simple concept. If fuel flow isn't the limiting factor and you are at MBT timing on the fuel you are running, there aren't much in the way of power gains other than from a major cooling reduction like with a stock intercooler.
Only if the customer decides to use the methanol as an additional fuel source to supplement for a fuel pump that can't keep up will additional boost be added (if additional turbo flow is available) at their request and after careful consideration of the risks.
Matt
