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Post by silverdragon on Jun 28, 2015 8:52:17 GMT
Explain "blows fuel"?... do you not have an over-run retarder that cuts off fuel when under load from engine braking?...
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Post by c64 on Jun 28, 2015 13:04:09 GMT
Explain "blows fuel"?... do you not have an over-run retarder that cuts off fuel when under load from engine braking?... Cars don't have retarders. A retarder is a hydraulic brake converting kinetic energy to heat by churning oil. Injection engines all cut off fuel when the accelerator is released all the way but the engine must have a minimum RPM or the engine may stall when the clutch it hit out of a sudden. And on the old "big" greycast engines, this RPM is set rather high. So either you shift down which causes a lot of jake braking, often too much or the engine keeps burning fuel - with closed throttle flap at high RPM burning much more fuel than depressing the clutch and use the brake pads.
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Post by the light works on Jun 28, 2015 15:23:31 GMT
Explain "blows fuel"?... do you not have an over-run retarder that cuts off fuel when under load from engine braking?... Cars don't have retarders. A retarder is a hydraulic brake converting kinetic energy to heat by churning oil. Injection engines all cut off fuel when the accelerator is released all the way but the engine must have a minimum RPM or the engine may stall when the clutch it hit out of a sudden. And on the old "big" greycast engines, this RPM is set rather high. So either you shift down which causes a lot of jake braking, often too much or the engine keeps burning fuel - with closed throttle flap at high RPM burning much more fuel than depressing the clutch and use the brake pads. 2400 RPM is VERY high. our fuel injectd engines have sensors in the exhaust which monitor how the engine is running - if it is blowing fuel, it WILL reduce fuel volume. and now some terminology lecture: a TRANSMISSION RETARDER uses the oil churning process to apply braking force. a JACOBS (Jake) BRAKE has a third set of valves installed in the cylinder heads, which open when the piston is at top dead center to release the compressed air (on most engines it also either mechanically or electronically shuts off the fuel injection) an EXHAUST BRAKE closes a gate valve in the exhaust system, diverting the exhaust gases to a closed pressure cylinder, which causes a huge amount of back pressure on the cylinders - effectively keeping them from purging on the exhaust stroke, so every upstroke is a compression stroke. - this is only on newer engines, and also turns off the injectors. in a gasoline engine, engine braking is accomplished by closing the throttle plate, which causes the cylinders to draw against partial vacuum on the intake stroke. the MAF correctly reads the lack of intake air and reduces the fuel delivery accordingly (similarly the lack of airflow through a carburetor does not draw fuel from the jets) but I know it has been mentioned as a myth that the engine draws more fuel coasting down a hill in gear than it does coasting down the hill in neutral. I believe SRRacing confirmed to us that the myth is busted - ant time a car is pushing against the engine it is burning less fuel than if the engine was idling in neutral.
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Post by c64 on Jun 28, 2015 16:26:09 GMT
but I know it has been mentioned as a myth that the engine draws more fuel coasting down a hill in gear than it does coasting down the hill in neutral. I believe SRRacing confirmed to us that the myth is busted - ant time a car is pushing against the engine it is burning less fuel than if the engine was idling in neutral. True - unless the engine RPM is very high. With "blowing fuel" I don't mean that the fuel isn't burned. The fuel is just completely wasted. Letting the engine idle at 1000 RPM consumes less fuel than pushing it with 2000 RPM. Twice as many strokes per time (same distance) burns more fuel - unless only half as much fuel is used for each stroke and this is impossible. The Monojettronic is just a substitute for a carburettor in order to have a regulated catalytic converter. Every other injection system for this car is much more sophisticated, but the Monojettronic is the one which lasts "forever" without any maintenance and that's why I like it. When something is wrong, you instantly know since you get clear symptoms, but you always can continue to drive home or at least make a temporary fix with basic tools. My current car has a "cold run regulator". All it does is to sneak extra air into the engine when the engine is still cold. The idea is to fool the air mass sensor. And the Monojettronic doesn't even have an air volume sensor. It's simply guessing by RPM, temperature and throttle position. The Lambda sensor in the exhaust pipe is used to correct the guess and dial in the correct mixture. Works a lot better than you would expect. And the "cold run regulator" does nothing at all, the Monojettronic can't be fooled in any way. But the regulator comes with a certificate which saves me over €300 in "stinker tax".
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Post by the light works on Jun 28, 2015 21:33:11 GMT
but I know it has been mentioned as a myth that the engine draws more fuel coasting down a hill in gear than it does coasting down the hill in neutral. I believe SRRacing confirmed to us that the myth is busted - ant time a car is pushing against the engine it is burning less fuel than if the engine was idling in neutral. True - unless the engine RPM is very high. With "blowing fuel" I don't mean that the fuel isn't burned. The fuel is just completely wasted. Letting the engine idle at 1000 RPM consumes less fuel than pushing it with 2000 RPM. Twice as many strokes per time (same distance) burns more fuel - unless only half as much fuel is used for each stroke and this is impossible. The Monojettronic is just a substitute for a carburettor in order to have a regulated catalytic converter. Every other injection system for this car is much more sophisticated, but the Monojettronic is the one which lasts "forever" without any maintenance and that's why I like it. When something is wrong, you instantly know since you get clear symptoms, but you always can continue to drive home or at least make a temporary fix with basic tools. My current car has a "cold run regulator". All it does is to sneak extra air into the engine when the engine is still cold. The idea is to fool the air mass sensor. And the Monojettronic doesn't even have an air volume sensor. It's simply guessing by RPM, temperature and throttle position. The Lambda sensor in the exhaust pipe is used to correct the guess and dial in the correct mixture. Works a lot better than you would expect. And the "cold run regulator" does nothing at all, the Monojettronic can't be fooled in any way. But the regulator comes with a certificate which saves me over €300 in "stinker tax". I guess it is that german engineering again. American fuel injection systems will turn the fuel injectors off if the car is pushing the engine. - to put it in real simple terms, if I am coasting my minivan down a hill in neutral, going, say, 55 miles per hour, I get about 35 MPG on the fuel use computer. if I am in gear, I am getting 99 MPG (the highest the two digit display can show)
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Post by the light works on Jun 28, 2015 22:04:32 GMT
bottom line: if your fuel injection is putting fuel into the engine at a greater rate than the minimum necessary to stop the engine from stalling, it makes you go faster.
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Post by silverdragon on Jun 29, 2015 6:50:31 GMT
I drove Exhaust brake vehicles in the 70's....?
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Post by silverdragon on Jun 29, 2015 6:54:46 GMT
Terminology not crossing the translation test... A Retarder in any design is a device that "backs off".
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Post by the light works on Jun 29, 2015 14:22:25 GMT
I drove Exhaust brake vehicles in the 70's....? hm. I had not seen them until after 2000. al our engine braking systems I was aware of in the 70s were the Jake brake - and unmuffled, at that.
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Post by c64 on Jun 29, 2015 16:13:54 GMT
bottom line: if your fuel injection is putting fuel into the engine at a greater rate than the minimum necessary to stop the engine from stalling, it makes you go faster. It does. You feel it pretty intense when the engine passes the proper RPM. The Monojettronic uses an extra temp sensor, a switch in the endstop of the throttle lever, has a potentiometer on the throttle flap and is wired to the ignition which is autonomous. To make sure it can guess the air mass by temperature, throttle position and RPM, they use the air filter of a Diesel engine which grantees a more unrestricted air flow than the classic UFO on top of the engine. If the endstop switch is pressed and the engine RPM high (very high), the injection stops. That's all. At lower RPM, the engine risks stalling when the clutch is suddenly depressed. Most modern cars can be stalled that way but it isn't easy, you have to catch the right moment. It looks like that VW had to get rid of overproductions of the old 1.8L greycast block which was developed in the 1960 and later also used for Diesel engines. Since they lasted unusually long, they must have sat on a huge mountain of spare engines. So the basic, cheap version of the Passat 35i comes with the "RP" greycast engine controlled by the minimalistic Monojettronic. Turned out that this configuration lasts even longer so most of the original 35i's still around are equipped with this engine. Some 35i have lasted more than 1,000,000 Kilometers with just one major engine overhaul.
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Post by the light works on Jun 30, 2015 4:25:00 GMT
bottom line: if your fuel injection is putting fuel into the engine at a greater rate than the minimum necessary to stop the engine from stalling, it makes you go faster. It does. You feel it pretty intense when the engine passes the proper RPM. The Monojettronic uses an extra temp sensor, a switch in the endstop of the throttle lever, has a potentiometer on the throttle flap and is wired to the ignition which is autonomous. To make sure it can guess the air mass by temperature, throttle position and RPM, they use the air filter of a Diesel engine which grantees a more unrestricted air flow than the classic UFO on top of the engine. If the endstop switch is pressed and the engine RPM high (very high), the injection stops. That's all. At lower RPM, the engine risks stalling when the clutch is suddenly depressed. Most modern cars can be stalled that way but it isn't easy, you have to catch the right moment. It looks like that VW had to get rid of overproductions of the old 1.8L greycast block which was developed in the 1960 and later also used for Diesel engines. Since they lasted unusually long, they must have sat on a huge mountain of spare engines. So the basic, cheap version of the Passat 35i comes with the "RP" greycast engine controlled by the minimalistic Monojettronic. Turned out that this configuration lasts even longer so most of the original 35i's still around are equipped with this engine. Some 35i have lasted more than 1,000,000 Kilometers with just one major engine overhaul. that's pizza poor engineering. I would consider that undriveable if it suddenly accelerates when I am coasting. only time that happens to me is if I have accelerated above my cruise setting for some reason and then try to coast without deactivating the cruise control.
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Post by c64 on Jun 30, 2015 20:27:29 GMT
It does. You feel it pretty intense when the engine passes the proper RPM. The Monojettronic uses an extra temp sensor, a switch in the endstop of the throttle lever, has a potentiometer on the throttle flap and is wired to the ignition which is autonomous. To make sure it can guess the air mass by temperature, throttle position and RPM, they use the air filter of a Diesel engine which grantees a more unrestricted air flow than the classic UFO on top of the engine. If the endstop switch is pressed and the engine RPM high (very high), the injection stops. That's all. At lower RPM, the engine risks stalling when the clutch is suddenly depressed. Most modern cars can be stalled that way but it isn't easy, you have to catch the right moment. It looks like that VW had to get rid of overproductions of the old 1.8L greycast block which was developed in the 1960 and later also used for Diesel engines. Since they lasted unusually long, they must have sat on a huge mountain of spare engines. So the basic, cheap version of the Passat 35i comes with the "RP" greycast engine controlled by the minimalistic Monojettronic. Turned out that this configuration lasts even longer so most of the original 35i's still around are equipped with this engine. Some 35i have lasted more than 1,000,000 Kilometers with just one major engine overhaul. that's pizza poor engineering. I would consider that undriveable if it suddenly accelerates when I am coasting. only time that happens to me is if I have accelerated above my cruise setting for some reason and then try to coast without deactivating the cruise control. Why should it accelerate when the injection starts. Cars with carburettors don't cut off fuel at all and they also could slow down by just releasing the accelerator just fine. If you release the accelerator at 100kp, the car slows down very fast. Around 60kph, the engine RPM drops under the threshold where the injection starts working again, then the deceleration is just less out of a sudden. The car will hold speed by "auto-throttle" at somewhere below 50 kph (5th gear) to prevent stalling the engine.
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Post by GTCGreg on Jun 30, 2015 21:57:54 GMT
that's pizza poor engineering. I would consider that undriveable if it suddenly accelerates when I am coasting. only time that happens to me is if I have accelerated above my cruise setting for some reason and then try to coast without deactivating the cruise control. Why should it accelerate when the injection starts. Cars with carburettors don't cut off fuel at all and they also could slow down by just releasing the accelerator just fine. If you release the accelerator at 100kp, the car slows down very fast. Around 60kph, the engine RPM drops under the threshold where the injection starts working again, then the deceleration is just less out of a sudden. The car will hold speed by "auto-throttle" at somewhere below 50 kph (5th gear) to prevent stalling the engine. My Jeep idles at about 750RPM. With the throttle released, the engine will not inject any fuel above that RPM. That's pretty slow MPH in any gear but 4th or 5th. I've never tried to used engine braking below that RPM. In higher gears, the engine won't produce enough torque to accelerate at idle speed and if engine braking in a lower gear, at 750RPM, it's time to put in the clutch and use the binders.
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Post by c64 on Jun 30, 2015 22:20:33 GMT
Why should it accelerate when the injection starts. Cars with carburettors don't cut off fuel at all and they also could slow down by just releasing the accelerator just fine. If you release the accelerator at 100kp, the car slows down very fast. Around 60kph, the engine RPM drops under the threshold where the injection starts working again, then the deceleration is just less out of a sudden. The car will hold speed by "auto-throttle" at somewhere below 50 kph (5th gear) to prevent stalling the engine. My Jeep idles at about 750RPM. With the throttle released, the engine will not inject any fuel above that RPM. That's pretty slow MPH in any gear but 4th or 5th. I've never tried to used engine braking below that RPM. In higher gears, the engine won't produce enough torque to accelerate at idle speed and if engine braking in a lower gear, at 750RPM, it's time to put in the clutch and use the binders. A small engine is different. It has not much of a mass to keep it going. When it shuts down the injection and you hit the clutch out of a sudden, the engine might not catch when it ran "dry" for too long. This is a major problem of diesel engines and the reason why Jake brakes are not allowed in the EU any more. Different forms of engine brakes are used or other forms of brakes that don't use them self up. When my engine is idling at 950..1000 RPM and I turn the key, the engine fully stops in half a second or so. That's why it keeps burning fuel unless it really runs fast so it always has time to restart no matter what you do.
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Post by the light works on Jul 1, 2015 0:21:27 GMT
Why should it accelerate when the injection starts. Cars with carburettors don't cut off fuel at all and they also could slow down by just releasing the accelerator just fine. If you release the accelerator at 100kp, the car slows down very fast. Around 60kph, the engine RPM drops under the threshold where the injection starts working again, then the deceleration is just less out of a sudden. The car will hold speed by "auto-throttle" at somewhere below 50 kph (5th gear) to prevent stalling the engine. My Jeep idles at about 750RPM. With the throttle released, the engine will not inject any fuel above that RPM. That's pretty slow MPH in any gear but 4th or 5th. I've never tried to used engine braking below that RPM. In higher gears, the engine won't produce enough torque to accelerate at idle speed and if engine braking in a lower gear, at 750RPM, it's time to put in the clutch and use the binders. mine idles at about 15 MPH in high gear.
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Post by silverdragon on Jul 1, 2015 6:02:49 GMT
I have not done an idle speed test on my vehicle, but it ticks over at just under 1,000rpm, I suggest about 8-900 rpm, until I turn something on. The engine will increase rpm if I switch on a load like lights, air-con, etc. I suspect the Engine Management unit has something to do with that...?...
However, engine braking in too high a gear, waste of time. If you are going to engine brake, you should be pushing for at least twice the stalling speed of the engine (eg tickover or idle speed) to get any effective braking.... Otherwise, the engine will just jerk about on its mounts.
Plus, I have always been taught, USE the damn clutch. Thats what its there for. Slip the clutch under heavy engine braking. Its an art form, for sure,. but I cant be the only one who does that?... Of course, the bigger the vehicle the better.... Again, my own car is just under 2ltr, but bloody economical.
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Post by the light works on Jul 1, 2015 14:26:15 GMT
I have not done an idle speed test on my vehicle, but it ticks over at just under 1,000rpm, I suggest about 8-900 rpm, until I turn something on. The engine will increase rpm if I switch on a load like lights, air-con, etc. I suspect the Engine Management unit has something to do with that...?... However, engine braking in too high a gear, waste of time. If you are going to engine brake, you should be pushing for at least twice the stalling speed of the engine (eg tickover or idle speed) to get any effective braking.... Otherwise, the engine will just jerk about on its mounts. Plus, I have always been taught, USE the damn clutch. Thats what its there for. Slip the clutch under heavy engine braking. Its an art form, for sure,. but I cant be the only one who does that?... Of course, the bigger the vehicle the better.... Again, my own car is just under 2ltr, but bloody economical. depends on how urgently you need to brake. yes, if you want to shed speed aggressively, you need to downshift. on the other hand, if I am coming down one of the local hills, and I'm not behind someone, high gear does just fine.
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Post by GTCGreg on Jul 1, 2015 14:37:52 GMT
Plus, I have always been taught, USE the damn clutch. Thats what its there for. Slip the clutch under heavy engine braking. Its an art form, for sure,. but I cant be the only one who does that?... Really? That's NOT what it's there for. Engine braking is one thing, Burning up the clutch is a totally different matter. Why would you rather wear the clutch over the brakes? Well, maybe if it's on someone else's truck.
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Post by the light works on Jul 1, 2015 15:10:27 GMT
Plus, I have always been taught, USE the damn clutch. Thats what its there for. Slip the clutch under heavy engine braking. Its an art form, for sure,. but I cant be the only one who does that?... Really? That's NOT what it's there for. Engine braking is one thing, Burning up the clutch is a totally different matter. Why would you rather wear the clutch over the brakes? Well, maybe if it's on someone else's truck. I think he means as opposed to sidestapping it to reengage it.
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Post by GTCGreg on Jul 1, 2015 15:18:24 GMT
I think he means as opposed to sidestapping it to reengage it. I don't know what that means. Is there something different about the way a clutch works on a semi-tractor?
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