What's better on hills: DWL or Pulse up, Glide down?

[DifferentPointofView]

^ in theory, but this would only work if gravity and rolling resistance weren't a factor.

Gravity works on your side when your using the gasoline, on the pulse, and you defy gravity by gliding up and not using gasoline.

[Duffman]

Originally Posted by monroe74

duff: "you just have to ask the right questions"

Then maybe I should start with this question: what's the right question that you think I need to ask that I haven't already asked?

"you car should have one?"

Yes, my car has a TPS.

"you can map out the A/F ratio which may help find efficient vs inefficient operating regions."

I don't know what you mean.

The trick is to create a BSFC map, or the equivalent, without the use of a dyno. I don't know how to do that, but maybe you do.

To assess "inefficient operating regions," I have to do more than just know the throttle position, and the AFR. I also have to have the engine under a known load, so I can maintain a steady state and monitor how much work is being done per unit of fuel consumed. Dynos were invented to solve this sort of problem.

What I meant by the “right questions” wasn’t that I had all the answers but just to ask questions. Having never met you I don’t know your knowledge base or your technical abilities. “How do I do that” is a great question if you really don’t know. I frequent a few different boards and this board by far has the most knowledgeable people, I am not sure how many actual mechanics there are here but there is at least one that I that I have been able to discern. There are many engineers though for sure.

With a voltmeter tied into your TPS go out and drive your car. If you can get a friend with a clipboard to come along and record data great, if you cant talk into a tape recorder as you drive. Record TPS voltage, RPM and A/F ratio and build a map like a BSFC map. The RPM that peak torque occurs at is a published value. That will be the sweet spot for fuel economy for your engine. More data around this region would be more valuable. Maybe just do that RPM alone, as the A/F ratio might stay constant against TPS for all RPMs. You will need an open area that you can vary speed and accelerate free of traffic as some TPS reading will accelerate the car.

[monroe74]

diff: "Gravity works on your side when your using the gasoline, on the pulse, and you defy gravity by gliding up and not using gasoline."

I think it's six of one, half dozen of the other. Momentum is momentum. I'm converting chemical energy into motion, and the amount of work required to send the car over the hill is the same, regardless of when I do the conversion.

"this would only work if gravity and rolling resistance weren't a factor."

I don't understand how RR becomes a factor, because it's the same whether I'm going up or down, and it's the same whether I'm coasting or under power.

[monroe74]

duff: "The RPM that peak torque occurs at is a published value."

Yes, 4500 rpm.

"That will be the sweet spot for fuel economy for your engine."

I don't think so. Peak torque is not the same thing as optimal BSFC. And the graphs we've been looking at seem to indicate that optimal BSFC occurs at low rpm. That's not usually where peak torque is.

"More data around this region would be more valuable."

I'm not very interested in what happens at 4500 rpm, because the amount of time I spend doing 4500 rpm is essentially zero.

"Record TPS voltage, RPM and A/F ratio and build a map like a BSFC map."

I would be looking at injector activity, not AFR, because the former is a direct measure of fuel consumption, and the latter is not. But I still wouldn't be getting useful data, because I would only be observing that injector activity is directly proportional to throttle angle. We already know that. What we want to know is how much power the engine is actually producing, at a given rpm and fuel input. That's why a dyno is needed.

[PaleMelanesian]

I agree that 4500 rpm is too high. I haven't seen that in over a year.

The advantage of pulsing uphill is that it's easier to put the engine into a high-load operating range. You have to accelerate very quickly to get that load downhill, or you use a lower-load, less efficient range. Also, like mentioned above, aero drag and reasonable speeds become an issue with pulsing downhill.

[Duffman]

Originally Posted by monroe74

duff: "The RPM that peak torque occurs at is a published value."

Yes, 4500 rpm.

"That will be the sweet spot for fuel economy for your engine."

I don't think so. Peak torque is not the same thing as optimal BSFC. And the graphs we've been looking at seem to indicate that optimal BSFC occurs at low rpm. That's not usually where peak torque is.

"More data around this region would be more valuable."

I'm not very interested in what happens at 4500 rpm, because the amount of time I spend doing 4500 rpm is essentially zero.

"Record TPS voltage, RPM and A/F ratio and build a map like a BSFC map."

I would be looking at injector activity, not AFR, because the former is a direct measure of fuel consumption, and the latter is not. But I still wouldn't be getting useful data, because I would only be observing that injector activity is directly proportional to throttle angle. We already know that. What we want to know is how much power the engine is actually producing, at a given rpm and fuel input. That's why a dyno is needed.

Yes 4500 is too high, I forgot we were dealing with hondas. But that said the lowest BSFC can still be at 4500, and not be your best cruise RPM.

Measuring injector activity doesnt tell you much because you do not know the power generated for the fuel injected. The fuel injected is not entirely proportional to throttle angle as you are saying that the ECU is changing the A/F ratio with throttle angle. I dont know what else to say, if you dont want to try it I understand because it is your time after all.

[JohnnyGrey]

Torque peak does not equal efficiency peak.

[monroe74]

duff: "Yes 4500 is too high, I forgot we were dealing with hondas."

You're suggesting that other cars generally have peak torque at lower RPM than that. Really? I just tried to imagine the most un-Honda vehicle I could: Chevy Suburban. I looked it up. Peak torque is at 4400 RPM. They must have hired some Honda engineers!

"Measuring injector activity doesnt tell you much because you do not know the power generated for the fuel injected."

It's true that I'm not measuring "the power generated for the fuel injected." That's because I don't have a dyno. I don't know how to do that without a dyno. Do you? I'm open to the possibility that you know a method I never heard of.

Nevertheless, it's still quite helpful to monitor injector activity, because it's a measure of instantaneous fuel consumption. There isn't much to analyze if I don't have a handle on fuel consumption, and it's nice to see numbers without waiting until I have a chance to fill the tank.

"The fuel injected is not entirely proportional to throttle angle as you are saying that the ECU is changing the A/F ratio with throttle angle."

It doesn't matter that throttle angle and fuel use aren't perfectly proportional. That would only be a problem if we had no way to monitor injector activity, and were instead using throttle angle as a proxy for fuel use. Fortunately, we're not obligated to do something that crude, because we can monitor true fuel use directly and instantaneously. One of the many nice things about not having a carb.

"if you dont want to try it I understand"

I like trying all sorts of things, but so far I don't clearly understand what it is that you're suggesting I try.

[monroe74]

One more thought about throttle angle. My casual observations so far seem to indicate that for any given RPM, throttle angle and fuel use do indeed seem to have a nice, smooth, linear relationship. It seems that fuel use is a direct function of those two things: throttle angle and RPM.

[Duffman]

It is possible to calculate power without a dyno (a few ways actually) but the accuracy is not sufficient to do BSFC calculations IMO. I don’t think we are having a meeting of the minds, I think we should each go back and reread the thread, that has been a help for me before.