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Old 05-20-2008, 05:10 AM   #81
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Originally Posted by R.I.D.E. View Post
I could easily stop the car with my thumb
I once had a car like that. There were big holes in the floorboard. But I eventually figured out that it hurt less if I just dragged my feet on the ground, instead of my thumb.
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Old 05-20-2008, 06:21 AM   #82
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Originally Posted by monroe74 View Post
does it have points? Any self-respecting old-fashioned distributor has a nice set of points. Are you old enough to know what points are?
Nope, electronic ignition. I do know what points are, we covered those in my high school shop class though the engine I brought in had electronic ignition. That was a nice engine, it really didn't need much and it dynoed really well so I got an A.

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Anyway, is that a picture of your coil?
Distributor cap.

Every time you say coil, I think of the modern coil found in a distributorless ignition system, one for each cylinder. I think I had a problem with one and fixed it myself once but I've since forgotten.

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You're tempting me to make a list of rock songs that use engine noise as a sound effect, but I'm not going to take the bait.
I'll get you started:

Jackyl - The Lumberjack Song (Chainsaw as lead guitar)
Motley Crue - Girls Girls Girls (Intro to song is an engine starting) (I'm not sure I remember this right)
Van Halen - Hot For Teacher (Not actually an engine, but a damn fine impression of one using drums to simulate a burbling exhaust)

I know there's a whole lot more, and many that are much older, but those are the ones I can think of off the top of my head.
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Old 05-20-2008, 07:24 AM   #83
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I know there's a whole lot more, and many that are much older
Exactly. I'll restrain myself and mention just one:

"According to legend, to add the authentic sound of a motorcycle engine, one was driven through the lobby of the hotel and up to the floor of the recording studio. No one was arrested, but a ticket was issued. However, in an interview four decades later, Shangri-Las lead singer Mary Weiss scoffed at this story, and said that the motorcycle sound was simply taken from an effects record. The Zombies' drummer Hugh Grundy recalls being the one revving up a real motorcycle backstage, when the Shangri-Las performed the song on a U.S. tour."
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Old 05-20-2008, 05:26 PM   #84
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I'd say a PIC is a whole lot better and lighter than using a Arduino board
I'd say something that works is a whole lot better than nothing Well, it is in alpha anyway (about $40):

http://forum.ecomodder.com/showthrea...pace-2115.html

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Old 05-20-2008, 06:17 PM   #85
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Actually not hard at all. Two screws and the side panels below the hood come out. Stand on the running board and adjust away LOL. One hand on the wheel the other on the screwdriver Ha Ha.

The 37 also had floor boards, so you could just take them out and use your feet.

The brake cables were original 72 years old, at the time.

regards
gary
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Old 05-24-2008, 04:34 PM   #86
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Quote:
Originally Posted by monroe74 View Post
"What and where do I probe to read injector duty cycle?"

My ECU has 4 pins, one for each injector. I just picked one. Positive lead of DMM attaches here. Other lead of DMM attaches to chassis ground.

"What setting do I use on the DMM?"

I set mine to 4 cylinder. That means full scale is 90 degrees (a quarter of 360). When you're in the world of dwell, you're speaking degrees of rotation.

When my dwell meter indicates 10, let's say, it thinks it's telling me that my points are open 10 degrees out of each 90. But here's what it's really telling me: my injectors are open 10/90th of the time.
News: I did it! It works great. I'll post my findings in another thread.

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FWIW, an LED does indeed respond to pulse width as long as the current is kept quite low, a 5K ohm series current limiting resistor and a schottky diode would do the trick.

The circuit would look like this...

Injector positive---->LED--->5K resistor--->schottky diode--->injector ground.

A regular diode would probably work just fine but a schottky diode is high speed and might respond to narrow pulse widths better.

You could pick up everything at Rat Shack for less than $5..

I would get 2K, 5K, 10K and 20K resistors and see which one gives the best brightness variation.. Or just use a variable resistor and play with the settings ..
I was unable to make any circuit like this work. I think I had too many wrong components. I tried a non-superbright LED from a computer case, and I failed to find schottky diodes so I tried zener and unidentified common diodes.. Can you suggest what I might be able to scavenge them from, and how to recognize them? Radio Shack didn't have them.
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Old 05-25-2008, 05:08 PM   #87
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Zener diodes probably won't work..

LEDs burn out in a couple of microseconds if reverse connected with no current limiting..

Regular diodes do work, I would try them.

Check out your circuit with a 1.5 volt battery or maybe a 3V battery.
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Old 05-26-2008, 07:32 AM   #88
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So, whether I'm using LEDs or the dwell meter, am I measuring the amount of fuel injected each revolution, or the actual fuel rate? In other words am I measuring gallons per hour or gallons per revolution (obviously not the best unit choices but they demonstrate the question)?
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Old 05-26-2008, 07:45 AM   #89
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So, whether I'm using LEDs or the dwell meter, am I measuring the amount of fuel injected each revolution, or the actual fuel rate? In other words am I measuring gallons per hour or gallons per revolution (obviously not the best unit choices but they demonstrate the question)?

You are measuring the length of time the injector is open, since the injector fuel flow is directly proportional to the length of time the injector is open then you are indirectly measuring fuel flow.

Gallons per hour would be a decent way to think of it. Since your measurement is not calibrated, all you are getting is a qualitative view of "more gas per unit time" or "less gas per unit time".
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Old 05-26-2008, 10:28 AM   #90
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You are measuring the length of time the injector is open
Yes. And it's helpful to understand that this is in relative terms, not absolute terms. The LEDs and the dwell meter are measuring duty cycle. That means the ratio of time spent open, as compared with time spent shut.

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Since your measurement is not calibrated
It's actually possible to do some calculations. Injectors have a known, fixed capacity. For example, for Hondas I think it's 240cc/minute. It's easy enough to convert that to gph. Then just factor in the number of injectors, and the observed duty cycle.

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am I measuring gallons per hour or gallons per revolution
The former. The concept of duty cycle automatically accounts for rpm. You don't have to worry about it separately.

Here's a way to think about it. The absolute duration of each injector pulse generally corresponds with throttle setting (load). Imagine WOT at 1000 rpm. Each injector pulse has a long duration, but there aren't that many pulses, per minute. This would be a relatively low duty cycle (maybe the injector is open 10% of the overall time). Now imagine WOT at 6000 rpm. The absolute duration of each injector pulse is probably about the same, but the pulses are happening much more frequently. So now the duty cycle is probably 60%.

If you imagine the revs going higher and higher, you would eventually reach the point (at least in theory) where there is no interval between one pulse and the next. Then your duty cycle is 100%. But the absolute duration of each pulse is the same as it was at 1000 rpm (assuming WOT at all times).

Opening the throttle makes each pulse longer. Raising RPM makes the pulses more frequent. If I make the pulses more frequent, without reducing the absolute duration of each pulse, then I'm increasing the duty cycle. So you can look at a duty cycle measurement and translate this into gph, without making any adjustment for rpm.

Some instruments report pulse width, instead of duty cycle. If you were measuring pulse width, then you would indeed have to factor in the frequency of pulses (i.e., rpm).
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