1st Generation (GD 01-08)The one that started it all! Generation specific talk and questions here!
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See, that's why I like these discussions. Quite informative, even considering what I already know.
Quote:
Originally Posted by mahout
Oh sure. How come my dyno curves show typically75 to 85 % efficiencies on the fuel consumed?
I'm not sure we're talking about the same thing. If I remember correctly, the efficiency you're talking about refers to completeness of combustion, no? The efficiency to which I was referring is Brake Specific Fuel Consumption (basically a measure of how much thermal energy is being converted to mechanical energy). Most conventional engines indeed do a good job in burning the fuel, but are only 25-30% efficient at converting that energy to useful work. Efficiencies in excess of ~32% have been dismissed as impossible with current designs. Quick example: the crankshaft alone is only about 65% efficient at converting recip. to rotary.
And, you're right that recip. to rotary is about the best we have. I was merely mentioning that the piston engines we have are not nearly as efficient as they could be, seeing that they are, with the exception of materials and number of valves per cylinder, virtually unchanged for the last century or more. Seriously? Can't come up with a more efficient crankshaft in 100+ years?
That Revetec engine is but a crude example of what you can come up with when you just try something truly different. They only changed the crankshaft, and achieved more than 50% better efficiency using the same piston/valve arrangement.
__________________
Best tank: 518.1 miles, 47 MPG -- Best commute: 50.3 in, 45 out
'07 NHBP Sport AT
Previous owner's mods: Tint front and back, Mugen visors
See, that's why I like these discussions. Quite informative, even considering what I already know.
I'm not sure we're talking about the same thing. If I remember correctly, the efficiency you're talking about refers to completeness of combustion, no? The efficiency to which I was referring is Brake Specific Fuel Consumption (basically a measure of how much thermal energy is being converted to mechanical energy). Most conventional engines indeed do a good job in burning the fuel, but are only 25-30% efficient at converting that energy to useful work. Efficiencies in excess of ~32% have been dismissed as impossible with current designs. Quick example: the crankshaft alone is only about 65% efficient at converting recip. to rotary.
And, you're right that recip. to rotary is about the best we have. I was merely mentioning that the piston engines we have are not nearly as efficient as they could be, seeing that they are, with the exception of materials and number of valves per cylinder, virtually unchanged for the last century or more. Seriously? Can't come up with a more efficient crankshaft in 100+ years?
That Revetec engine is but a crude example of what you can come up with when you just try something truly different. They only changed the crankshaft, and achieved more than 50% better efficiency using the same piston/valve arrangement.
Its not how complete the combustion, its how much work you get out of the input fuel. conversion of so many BTu per hour from combustion of so many grams of fuel and the Btu per hour measured at the engine
Can't access the revtec site but memory says it is a reticulating piston rod tha tsupposedly improved the transfer of push to rotary. I believe it was also tried in the early 1900's by GM and some privateers. If that was it then the problem with use was the considerable mechanical complexity and resulting poor reliability that did it in. And yes, most of the combustion heat goes out the tailpipe as heat but the conversion of pressure to rotation is impressive.Revtec doesn't solve that either in my memory.
Electric motors are the far better conversion once we learn how to convert fuel or solar to electrical power. Hopefully, the latest generation will have better luck than mine. They better.
I don't think that there is any vehicle more efficient than a high quality bicycle... The thing that contributes most to the inefficiency of motor vehicles is friction and the oil company's are creating some very slick stuff that is being used in Formula One racing.... Corporations like Toyota are the only non breathing entities that are privileged to have access to the stuff though.
Its not how complete the combustion, its how much work you get out of the input fuel. conversion of so many BTu per hour from combustion of so many grams of fuel and the Btu per hour measured at the engine
You're describing thermal efficiency (<-- I may have misused this term earlier -- not sure). Thermal efficiency is a function of how complete the combustion is, namely, how much heat energy (BTU) is released from how much fuel (grams, for instance). The more complete the combustion is, the more energy will be released from the fuel, thus increasing the thermal efficiency. (Incidentally, it is not generally possible to exceed 80% thermal efficiency with gasoline and the like, because the process of combustion itself destroys about 20% of the fuel's energy potential.)
Also, the Revetec engine seems to be different than the one you described. It uses 2 counter-rotating camshafts in place of the camshaft.
Picture = 1 kiloword: Revetec Development
From what we see the vtec kicks in about 3700 to 4000 rpm
I've read differently:
Quote:
According to Doug Macmillan of Hondata, the VTEC "window" on the L15A falls between 2200 and 3400 rpm with actuation dependent upon throttle position and load. At WOT, the second intake valve should joins the party at around 2200 rpms (the "VTEC engagement point"). At about 3400 rpm, the torque curve takes a brief dip - this is due to a momentary peak in the torque curve between 2500 and 3300 rpms which can be attributed to the long narrow runners of intake manifold.
Unless you know the programmed curve you have no idea whether the advance is being retarded. You just know the advance.
I don't get what you're saying - when timing is lower than it was before, ignition retardation is assumed . . . unless you're saying that in order to qualify for "retarded", it has to be ATDC? If that's the case, then yeah, it'd only be greater or lesser amounts of timing advance. But that's petty semantics, in my opinion.
But when the only changing variable is the fuel octane and timing adjusts by 2-4 degrees (and timing curves are identical in shape), I think it's safe to say that ignition timing is affected by octane in this engine. Believe me, I was surprised as anyone, but the logs are pretty clear. I still plan on testing again before the summer is over - and I'd love to see someone else's results as well.
I don't get what you're saying - when timing is lower than it was before, ignition retardation is assumed . . . unless you're saying that in order to qualify for "retarded", it has to be ATDC? If that's the case, then yeah, it'd only be greater or lesser amounts of timing advance. But that's petty semantics, in my opinion.
But when the only changing variable is the fuel octane and timing adjusts by 2-4 degrees (and timing curves are identical in shape), I think it's safe to say that ignition timing is affected by octane in this engine. Believe me, I was surprised as anyone, but the logs are pretty clear. I still plan on testing again before the summer is over - and I'd love to see someone else's results as well.
I guess that you know that I am in agreement with you.... Thank you for being a reasonable person..... I would give you a Rep but they won't let me give you another one today.
it's like a bj from a female supermodel vs a bj from a homeless guy with your eyes closed
BIG DIFFERENCE
A psychologist would refer to your analogy as a very loose association.... When your arteries are clogged from fast food and you are on high blood pressure medication you can forget about B.J.s even if it was with a super model.
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!!
OK, the Needle started to drop around 210km... definite improvement!!
Your car does that on premium fuel too?.... Why am I not surprised?.... Mine doesn't come off the peg for over 100 miles of 70 MPH driving with the A/C/ on in 100+ temperature..... For accurate mileage figures I fill to the top.
I fill to the top too for more accurate results... Just returned from the trip, the needle did start to gown at 215km this time Vs the usual 180 190km on Regular and on the very same route...
To check my theory on the benefit to performance and fuel mileage gains, I have also added some pricey octane booster..... Try it, you will be surprised and be even more aware of the ECU's ability change A/F ratios and timing....I am not 100% sure but I believe the O2 sensor is what is providing the signal to the ECU.
I know the O2 sensor signal is used to determine A/F ratios, but I don't know about timing. Knock sensor?
Just extrapolating, I can imagine the O2 sensor signal catching lower than normal O2 in the exhaust, since the extra octane rating causes the fuel to burn more slowly, then the ECU leans the mixture while adding extra advance to make sure the leaner mixture gets completely burned.
Just guessing at this point...I have some knowledge of the principles, but I don't really know what determines what timing gets used, besides the semi-hardcoded maps in the ECU and the knock sensor.
__________________
Best tank: 518.1 miles, 47 MPG -- Best commute: 50.3 in, 45 out
'07 NHBP Sport AT
Previous owner's mods: Tint front and back, Mugen visors
To check my theory on the benefit to performance and fuel mileage gains, I have also added some pricey octane booster..... Try it, you will be surprised and be even more aware of the ECU's ability change A/F ratios and timing....I am not 100% sure but I believe the O2 sensor is what is providing the signal to the ECU.
Personately i believe the ECU is tuned according to far better gas then here in North America and that the knock sensor maybe very sensitive to retard quickly in case of using cheapo gas!! I also believe that the ECU, sometimes, gives advance until it exibit just a little pinkage and then saves the data to give the maximum possible Ignition Advance!!
My guess...
Marko!!
P.S. I recieved my Spark Plugs today... I think i wil install then right now... I'm too curious!!
Interesting thread from last year on the same subject. A few very good posts. wrussi, who said he's a tuner, thinks the Fit ECU is designed to adjust timing on-the-fly.
P.S. I recieved my Spark Plugs today... I think i wil install then right now... I'm too curious!![/quote]
I hope that you get positive results..... The fuel mileage you are getting is unbelievable compared to what some guys have told me they are getting in Automatic transsmission equipped Fits..... Are you using Amzoil transmission fluid and if so can you tell any difference in the operation of yours ???
I don't get what you're saying - when timing is lower than it was before, ignition retardation is assumed . . . unless you're saying that in order to qualify for "retarded", it has to be ATDC? If that's the case, then yeah, it'd only be greater or lesser amounts of timing advance. But that's petty semantics, in my opinion.
But when the only changing variable is the fuel octane and timing adjusts by 2-4 degrees (and timing curves are identical in shape), I think it's safe to say that ignition timing is affected by octane in this engine. Believe me, I was surprised as anyone, but the logs are pretty clear. I still plan on testing again before the summer is over - and I'd love to see someone else's results as well.
In science and politics, semantics is everything.
The term retarded is indeed the problem here. To retard is to drop ignition after top dead center (ATDC) and advance is before top dead center (BTDC). When you say the spark is retarded to me its just less advanced. And in most of the fuel injection maps there are many parallel ignition curves. Curves side-by-side so it looks like a blanket with 3D 'bumps' all through the blanket. (Thats why its a map and not a curve) Each curve is selected by load and rpm observed by the engine and will switch back and forth rapidly. Thats the advantage of modern computer control over the old mechanical advances. And if the ignition point follows the map is it retarded when it increses or decreases by design?
When engine demands change the ignition point selected will slide across the parallel curves and in fact will increase or decrease according to the curve it ends on by the computer selection. Unless you do this on a dyno it will be extremely difficult to monitor.
I have been prying into my Fit ECU programming to see if it will advance until it detects knock and then using that as a increase automatically added to the selected curve to 'perhaps optimize' my ignition advance. However. I have found nothing yet that reacts to increasing advance until knock is detected by fudging signals to the ecu.
Worse, from past experience its not always advantageous to advance the ignition signal. And often its disadvantageous.
Perhaps that is another difficulty in assuming that more advance is always better for more power.
And in the case of modern engines that little 'emissions' requirements has a death hold.
Cheers.
PS heats of combustionare theoretical and always on 100% complete combustion.
Linear Mode
