and perhaps data at all operating environments would be nice...
-40C to +85C.

otherwise you only see the values at the temp/humidity/atmospheric pressure
the OP tested.


ok, getting too technical for a bigmac vs charburger thread.

 

Knock sensors are always set. They don't change; its just looking for rapping noise. Same for ignition advance. It only retards when there is a signal from the knock sensor. It does not increase advance until it detects knock and 'kicks' back. In other words, its not a variable advance curve.
Any advantage, and there is some, lies in the increased heat of cobustion from the better chemical components in gasoline. For example, adding toluene to regular will yield higher energy from combustion better than 'premium', hence more power and higher mpg but that was a trick only used by showroom stock racers. Refineries don't waste higer energy components where they aren't needed. Costs too much.

 

Is that what I'm doing?

I'm not posting any conclusions . . . because I don't have any yet. I'm just providing the data I was able to record, with conditions as controlled as possible on public streets. i.e. same temperature/weather, same tire pressure, same weight in the car, same electrical load, same stretch of road, no corners or elevation change, and all runs done in 2nd gear. For each grade of gas I made 5 runs @ WOT, 5 @ third throttle, and 5 @ half throttle. The results were so repeatable that I only bothered keeping 3 of each part throttle set.

If people have realistic suggestions for an improvement in my methodology, I'll do it. I want to revisit this for myself before the end of the summer, or maybe in cooler fall temperatures . . . but I'd put money down that the trend will be the same.

This was actually the first tank of 93 I've put in this car. Calculated mpg results are worthless because of the variables in my commute, and I didn't notice any difference in smoothness or power. But I did find differences in how far the ECU advances ignition . . . whether or not it's significant, I still don't know. I've said it before here, just because ignition is advancing, that doesn't mean it's making any more power or getting better mpg.

Mostly, yes. IAT's for the runs were all within 10 degrees of eachother, and the vast majority were within 4 or 5 degrees. For street testing, I think that's pretty good. :shrug:

 

Yeah, that was awkward wording on my part.

That's the thing - according to my data, the knock sensor is pulling some timing when running on 87. If people don't think my logs are statistically significant . . . well, they aren't. It's a pretty small sample size. But when I see the repeatability of the spark curve on all my runs, I'm believing them more and more. Even on the runs that I threw out (a couple dozen of them due to inconsistent throttle usage), I was surprised at how close the spark curves resembled the runs I kept.

I think I am going to start running 93 to see what it does to my mpg over 10 or 12 tanks compared to the last dozen. Maybe look into a finding a dyno, get baselines with the different fuels. Either that or first try mid-grade & see what sort of spark advance the ECU uses.

 

Cause then I have enough change to buy a hot fudge sundae.

 

yes, my point exactly... well... not a hot one.

use the cheap stuff when expensive stuff is not required.

but interesting experiment though.

 

Can anybody explain the sudden drop in ignition advance on the Fit between 3700 and 5300Rpm at WOT...? Sounds like there is power left on the table here!!

You have the very same conclusions then me except your program is far more precise then my scan tool in datalog mode! Congrats!!

Marko!!

 

When you change the intake opening from 'normal' to vtec there could be a change in timing to accomodate the change in the charge; however, don't know just what happened to your timing. We didn't see much change but then ours wasn't connected to a vtec ecu either.
I would expect additional advance not drop because of the higher rpm..

 

Happens on all the part throttle runs as well . . . don't know why. I'm not sure what it has to do with VTEC engagement - at WOT VTEC should kick in the second intake valve quite a bit earlier than 3700 . . .

Dynos I've seen of stock engines do have that torque dip @ 3400-3500 rpms, but from what I've read that's attributed to the intake manifold hitting a sweet spot @ ~2700.

 

From what we see the vtec kicks in about 3700 to 4000 rpm and when it does the air flow velocity drops considerably and probably is the reason for the drop in torque The bmep drops and that is usually a good indication.
Vtec needs enough rpm to cause the least change in air flow as the 'new' cam makes the valve opens and closes or otherwise the engine power would drop seriously.

 

That is a very logical observation mahout. It also makes perfectly good sense.

 

I am quite interested in this ever since I put the advance gauge on my ScanGaugeII screen. I have been wondering if the additional advance would offset the lower energy content in my hilly neighborhood, especially since I have the AT, which has taller gearing.

 

Unless you know the programmed curve you have no idea whether the advance is being retarded. You just know the advance.

 

Advance has no effect on the energy from combustion unless you advance too far or retard too much, not likely on a Fit. Any mpg differences would fail by standard deviations in statistics analyses of the data. A given push on cylinders doesn't change the mpg enough to know.

 

Spark advance isn't MEANT to change the amount of energy you get from combustion, it's meant to optimize WHEN that energy is available. For maximum power, the combustion needs to be complete (or nearly so) at about the point on the power stroke when the piston has the largest mechanical advantage with respect to the crankshaft. To get it that way, you ignite the charge a bit before TDC, since the charge takes several milliseconds to burn. As RPM increases, under general conditions, you apply more advance to complete the combustion at the right point in the power stroke. Things like the amount of throttle applied and IAT also figure in here.

Well, I have an AT Fit, which has taller gearing than the MT. Where I live, there are a lot of hills, and since I put the IGN (advance) gauge on the screen of my ScanGauge II, I've noticed that when applying extra throttle in order to maintain speed going uphill, especially if I'm in 5th gear--as I usually try to be, for max economy--the computer will significantly retard the spark, even going right up to TDC (according to the ScanGauge). Any mechanic worth his price will tell you that's no good for power. If those conditions are maintained, and the RPM continues to drop going uphill, the computer finally decides it has had enough and unlocks the torque converter, or even downshifts. That same mechanic will tell you this is no good for fuel economy.

That is why I'm interested in this discussion. My neighborhood terrain exploits the biggest weakness of the engine, bringing out the worst in my car. You have this set of circumstances where the first condition (somewhat of a tendency to knock at low RPM/higher load) leads to another condition (retarded spark), which leads to a third (loss of torque), which leads to a fourth (lower economy because of unlocking the slushbox/downshifting). I would very much like to find out if changing to 89-93 fuel will stop or delay that process enough for me to crest a larger percentage of the hills I regularly climb. I may experiment some, like the OP, to see what happens.

Oh, by the way, In My Opinion, all conventional piston engines in production cars are more or less garbage because their design inherently makes it impossible to extract a decent amount of energy from the combustion process. There are better ways to use fire to turn a shaft.

Revetec, for example, have developed an engine that still uses pistons, but uses a more efficient crankshaft to give the pistons more leverage. Independent tests have put a figure of 39.5% efficiency (in terms of kWh per gram of fuel) to the latest crude prototype. Most engines are around 25-30% efficient. And if I understand correctly, these guys are not even using fuel injection yet.
YouTube - Evolution of the Revetec Engine

Oh, well. I'm done ranting now. Back to the padded cell...

 

I have been down shifting on hills and allowing the engine to rev higher but with less throttle than I would use in a taller gear.... My fuel mileage figures are looking a lot better. ... My car has a manual transmission but the principle would apply to an automatic as well. Try it with your scan-gauge and see if the ignition timing retards..... Put premium in your car and compare the results with those that you have now.

 

If pure fuel economy is your goal, a properly designed Header and Air Intake as well as AMSoil 0w20 should be better then Premium... Maybe even those IK22 plugs we talk about in the Forced Induction Forum! Anyway i'm gonna do 400km this morning so i'm gonna see if my fuel needle will start to drop later then at the usual 180km now that there is premium gas in my tank!! I'll let you know later for the Gas and in two weeks for the plugs!

Marko!!

 

I drove 102.9 miles (166 Km) yesterday in 100+ degree weather running my A/C, after filling to the top of the filler tube...... My fuel gauge needle is still pegged out past the full mark. 90% highway at 65 to 70 MPH with a few full throttle passes and using the cruise control on flat stretches.... I am finally getting the hang of driving economically with the super charger..... Good luck with the plugs, I will be getting some also.

 

Yeah, me too.

 

Yeah, me too.