330i injector duty cycles

belixxx · 08-03-2010, 07:45 AM

Does anybody know what injector duty cycles is the 330i running at most in its oem state? (Can this be logged with the BT tool or any other scanner the forum members are using?) OBDII cars can all have long term fuel trims of +30% before throwing any codes, so if fuel presure is fix it is obviously lower than 0.7 but by how much?

My other question would be is someone familiar with how the fuel pressure is controlled in the system? Most returnless systems I know have a built in mechanical fuel pressure regulator in the tank with the fuel pump. However I have also seen ones that have variable fuel pressure controlled by the ecu solely electronically (I'm not talking about a high pressure piezo type system but a conventional 3-5 bar system).

I'm interested in the above because it would be fun to try e85 without phisically modifying hardware (let alone a nitropropane+touol mix). E85 would require about 50% more flow from the injectors than gasoline. E85 has 96 octane (summer blend) or 94 octane (winter blend, which is actually e70), at least here in central europe. And the use of it should result in something like 12-13% power increase which translates to around 30hp in a 330i. I have already tried 50/50 blend of e85 and gasoline which results in fuel trims going up to +25% (as it should be) which is within the factory limits. Theoretically this should result in something like 10hp increase, which I fully admit I couldn't feel at all

Oh please spare the e85 will melt your fuel system/kill your fuel pump/sell your wife and kids as slaves and other comments, as I would like to focus on the fuel delivery part here...

mike-y · 08-03-2010, 11:44 AM

E85 produces LESS energy than gasoline. So you'll burn more of it and make less power. That's why you didn't feel any power increase - there was none. As you discovered, you get about 20% or more reduction in gas mileage when using E85. In order to truly take advantage of E85, you'd need to increase your compression ratio and timing to a point where you wouldn't be able to run regular gas anymore.

Since it burns at a much cooler temperature than gasoline, it makes less power, that's why you need to burn a lot more of it. But it can be used in turbocharged applications to help "cool" down the combustion temps at high boost levels. It's really more of a band-aid when used in this manner though.

and for the original question about injector duty cycle - sorry, I don't have an answer for that

belixxx · 08-03-2010, 12:32 PM

Quote:

Originally Posted by mike-y

E85 produces LESS energy than gasoline. So you'll burn more of it and make less power. That's why you didn't feel any power increase - there was none. As you discovered, you get about 20% or more reduction in gas mileage when using E85. In order to truly take advantage of E85, you'd need to increase your compression ratio and timing to a point where you wouldn't be able to run regular gas anymore.

Since it burns at a much cooler temperature than gasoline, it makes less power, that's why you need to burn a lot more of it. But it can be used in turbocharged applications to help "cool" down the combustion temps at high boost levels. It's really more of a band-aid when used in this manner though.

and for the original question about injector duty cycle - sorry, I don't have an answer for that

Hi,

What you've written is true. For engines with carbs, or open loop injection systems. Our cars however have closed loop. This meaning the ecu tries to get the same voltage reading from the O2 sensors. As a result of this the mixture richens. Now, the same weight of E85 truly produces LESS energy than gasoline. Approximately 27% less. However if you look at stoichiometric ratios of the two fuels (or better: "power lean" air to fuel ratios) you'll se, that with the same amount of oxygen present you can burn ~50% more(keeping the lambda reading the same). That results in power INCREASE. Also note that I had 50/50 mix of gasoline and e85 to stay within the limits of the ecu (30%). So the increase in fuel trims was carried out via the closed loop fuel system to keep the air/fuel ratio where it should be.What you were talking about with the reduction of gas milage is for straight E85 based on the fact that "if you would drive the same way as before, the car would need this much more fuel to provide the same power for moving, blah blah...". But during for examlpe a drag race the car if the ecu and fuel system could keep up would use 50% more e85 than gasoline (again we are talking about weight, not volume). And producing 1,5*(1-0.27) times more power.
I also said that the summer blend of e85 has 96 octane ( I will be using AKI numbers throughout) which is 2 more than the 94 octane premium gasoline they come calibrated for in Europe. So raising the compression for 94->96 would be quite dumb. You only need ignition advance. (Note that I still used 50/50 mix, so it is actually 94->95 for me...). Now regular gas is 92 around here so we are not talking about that much of a difference that having the ecu optimized for 96 it wouldn't run on 92 anymore (from factory the car can run anything above 89 thx to knock detection, so if I would increase this with 2 points I would still be under 92 which is regular gas )

mike-y · 08-03-2010, 02:58 PM

If your car isn't turbocharged, you really won't be able to utilize the potential power gains of using E85 (imo). And you'd need to be able to change the engine tuning on the fly. How are you planning on changing your ignition timing when you run E85? There are cars here that are able to run on 100% E85, and I assure you, they aren't making more power than their gasoline counterparts. Here are the results of of a 'flex-fuel' vehicle (Chevy Tahoe) that are designed to run 100% E85 and also gasoline. The computer and fuel system compensates for the E85 as necessary:

Final results Gasoline E85
0-60 9.3 9.7
1/4 mile 16.7 17.0

But if you believe you can find a way to make your car run better on E85, then I wish you the best of luck.

belixxx · 08-03-2010, 03:23 PM

Well there could be a number of reasons it doesn't produce more power on E85. For example it can be tuned to produce maximum fuel efficiency or minimum pollution (aka stoich.) on E85 not for max power. As probably a nonsport flexfuel buyer wouldn't be interested in gaining 12% of power with 50% more fuel consumption. Do you know the fuel consumption datas for that same car?

Imagine the same thing in a gasoline only car. For example the Prius stays at 14.7 even at full throttle which leaves serious amount of power in talon with simply modifying the a/f ratio to 12.5 eventhough it is an n/a car.

The car can be simply chipped to 96 octane and if there is no E85 available the knock sensor will do it's job. Just like when using the regular 92 instead of the premium 94. The bigger question is the original one. Has the factory fuel system enough headroom for flowing 50% more fuel or not...

mike-y · 08-03-2010, 03:51 PM

They said on gas, they got 18.3mpg, and on E85 is was 13.5mpg. so 26% less (assuming I calculated that correctly). E85 is rated at 103 octane in the US, btw.

They also mentioned that even though E85 was cheaper at the pump, it ended up costing more money to fill up with E85 because of the worse mileage. And just in case someone asks about the environmental effects of E85 vs Gasoline, they found that the CO2 emissions between the two, based on that test was 0.5% less for E85, which doesn't sound too promising for green types.

Also, they did say that due to the nature of designing a Naturally aspirated flex fuel engine, you can't optimize power for E85 and still run gasoline. So you might not be able to get to 50% additional ethanol. In my experience, the "sweet spot" for NA power is around 13.2 - 13.5 AFR. I usually see turbo cars run richer though, mostly for safety and EGT's (direct injection cars excluded).

5erman · 08-04-2010, 12:31 AM

I am not seeing where you are getting the 50 percent more number? All you would be doing by adding e85 is trying (to no evail) to tune your car by using the closed system-basically making the o2 sensors read lean due to burning the e85, it will call for more fuel and increase the fuel injector pulse and start consuming more fuel etc-however the injectors have a limited capacity to increase and cannot increase enough fuel to make up for the deficit in how much less power you burn with e85.

If the fuel injectors could cyle 3 times longer than theoretically you would be dumping enough fuel and thus energy to put out more hp-a rich ratio.

However lets say for simplicity the stock injectors can only double in cycle length and not triple-than they can only flow 20 percent more E85-that is not enough tcompensate for the powerloss.

By doing this you are essentially trying to "richen" the mixture by using e85 as the "trickster" rather than a piggyback tune using a resistor as the "trickster". Just get a PBX tune-that does this with resisters-makes the mixture rich and advances spark timing.

You would need new injectors to go any further with that theory and then you start being limited by airflow-not enough air to keep up with that much fuel, even at a richer mixture.

Sorry to rain on your parade.

The best "bang " for your buck is to use e85 and live with less power and fuel for half a tank-that will change the LTFT in favor of richening mixture-then ad 93 octane straight gas and you will run rich for a half a tank until the ltft recompensates and see some "power"gains which is nothing more than LTFT correction.

But remember too rich is nto good either-so at WOT with a LTFT trying to further richen things-you run wayyy too rich and performance suffers.

Remember LTFT is calculated from the normal (non WOT ) driving based on STFT values every second/minute-then when you hit WOT-the LTFT number is "added" to the set WOT ratio that is richer than the cruising/normal ratio-which is good if the LTFT is zero but not if you are already at an LTFT that is richening you by 30percent

belixxx · 08-04-2010, 04:58 AM

Quote:

Originally Posted by mike-y

They said on gas, they got 18.3mpg, and on E85 is was 13.5mpg. so 26% less (assuming I calculated that correctly). E85 is rated at 103 octane in the US, btw.

They also mentioned that even though E85 was cheaper at the pump, it ended up costing more money to fill up with E85 because of the worse mileage. And just in case someone asks about the environmental effects of E85 vs Gasoline, they found that the CO2 emissions between the two, based on that test was 0.5% less for E85, which doesn't sound too promising for green types.

Also, they did say that due to the nature of designing a Naturally aspirated flex fuel engine, you can't optimize power for E85 and still run gasoline. So you might not be able to get to 50% additional ethanol. In my experience, the "sweet spot" for NA power is around 13.2 - 13.5 AFR. I usually see turbo cars run richer though, mostly for safety and EGT's (direct injection cars excluded).

Hey, that's what I'm talking about... That air fuel ratio is lean, calibrated for the best milage. So it only aims to have ruffly the same power like on gasoline.

Interesting that the pricing on gasoline must differ in the US then, because if E85 costs X around here, than premium gas costs 1.51X so at only 26% more fuel consumption it would actually be cheaper to operate on E85 here (note: I couldn't care less about this feature of it).

belixxx · 08-04-2010, 05:39 AM

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