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04-24-2014, 01:26 PM | #76 |
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Take a look at Wikipedia
http://en.wikipedia.org/wiki/Gasoline_direct_injection No throttling lossess=no pumping losses, without a throttle plate... Seems like there are three types of direct injection: There is one with throttle, Toyota uses it and seems like Subaru uses it as well. One with auxiliary throttle, needed at low load One with no throttle, that uses a concept called stratified charge. This provides fuel savings at low loads. Audi seems to use this, but possibly not for the US market.
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Last edited by Vlad; 04-24-2014 at 01:53 PM. |
04-24-2014, 02:32 PM | #77 | |
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Quote:
Other manufacturers may reference the mechanism as throttle, likewise. Can we agree its mechanism semantics? |
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04-24-2014, 02:48 PM | #78 |
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Diesel engines have a throttle now, basically for EGR/emissions control. However the load is still basically controlled by fuel mass injected (in addition to EGR rates).
When they talk about "dethrottling" on a gas engine, whether it's through valve events or through lean stratified combustion, it's really running a higher manifold absolute pressure. The goal is lower pumping mean effective pressure--you'll see it in a cylinder pressure trace. This is something that can't easily be done without careful coordination of an electronic throttle, spark control, and other actuators. You still need a throttle valve for failsafe operation and certain conditions where the engine won't tolerate dethrottled operation. The software uses a gasflow model (Ideal gas law and/or saint venant flow equation, basically variation of navier-stokes) to control the AVCS/cam phasers and throttle valve for a target MAP. So if normally you'd run around 40 kPa MAP fully throttled, you can raise your MAP to anywhere between 40-90 kPa at a given speed and load point. The simplest way to do that is with internal EGR from dialing in overlap by phasing the cams. You might get 60 or 70 MAP, maybe higher, with cam phasing alone. Your upward limit on MAP is about 90 kPa on a gas engine, because some vacuum is still required to drive evaporative purge, PCV, and other functionality. 90 kPa is typical on a lot of systems with continuously variable valve lift. However, in reality the dethrottling is limited by combustion stability. Combustion stability depends on a bunch of parameters like DI rail pressure, injection timing, spray pattern, intake port tumble characteristics, and piston bowl design. Lean stratified combustion might run at lower MAP than 90kPa but the charge air is highly diluted like a diesel and thermal efficiency is higher. |
04-24-2014, 04:14 PM | #79 |
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I had a thought that some kind of plate made its way into diesels.
My 1982 Mercedes 300SD had the compressor outlet bolted to the intake manifold with no in-between anything. Inside the manifold there was the engine shutoff flapper, but that's different. You can call the accelerator linkage to a diesel throttle linkage, but it in fact links to the fuel injection pump, where in a mechanical pump, the flow is controlled. Maybe that can be called fuel throttling. The factory manual for that old boat was in German, so it has a name consisting from numerous letters... |
04-24-2014, 04:57 PM | #80 |
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Talking about common rail diesels for passenger vehicles: Besides controlling the cooled EGR loops (high and low pressure on some engines) on a diesel engine you have to do a bunch of stuff to regenerate the particulate filter and NOx catalyst if applicable. That's where the throttle valve fits in.
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04-24-2014, 06:00 PM | #81 | |
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http://www.subaruforester.org/vbulle...t-poll-259170/ -Dennis |
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04-24-2014, 10:12 PM | #82 |
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04-24-2014, 10:13 PM | #83 |
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so do we have throttle bodies or not? I suppose i could pull the cover off and look
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04-24-2014, 10:21 PM | #84 |
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Please do.
The info I found refers to the BRZ and you can see that it has a TB. Then that injection system is linked to a Toyota direct injection that does have a TB. Now that partial FA20DIT teardown from the Japanese site that someone linked, showed something similar with composite TGV housings. The point I was trying to make is that with a DIT, these could be a lot more than just TGV. I wonder if these become the .. part time throttle plates? Then maybe you won't find a central unit. Also, the DI field seems to be moving fast, new things come out often. |
04-24-2014, 10:24 PM | #85 |
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These engines do have a throttle like normal
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04-24-2014, 10:25 PM | #86 |
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saved me the trouble
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04-25-2014, 07:43 AM | #87 | |
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Quote:
I know it sounds weird, but you can't have an "unthrottled" gasoline engine without a throttle. You're still using the throttle even when the valve events are limiting load. You also use it during starting and as another form of torque control during various events. I |
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04-25-2014, 08:13 AM | #88 |
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I'm going to venture a guess that everybody here knows what TGV's do, it's not necessary to repeat that... again.
I was talking about ... new... TGV ... additional... assignments. An engine with no throttle plate is possible. Here's a quotation from BMW: "This highly advanced technology replaces the conventional throttle butterfly with a electrical mechanism that controls the amount of lift of the individual intake valves on each cylinder. Your engine is able to breathe freely, delivering better performance while using less fuel. The performance of the engine is more efficient and immediate, thanks to the elimination of the pumping losses and air-flow disturbance caused by a conventional throttle butterfly. Instead, air can flow through the intake manifold freely, and Valvetronic precisely regulates the quantity of air entering the cylinders" So yes, it is possible, not only possible, but one is currently in production. And the whole point of this engine is to achieve control with a method other than using a throttle. It's not semantics, it's real pumping losses savings. Here's a quotation from Wikipedia: "The cited gains are achieved by the precise control over the amount of fuel and injection timings that are varied according to engine load. In addition, there are no throttling losses in some GDI engines, when compared to a conventional fuel-injected or carbureted engine, which greatly improves efficiency, and reduces 'pumping losses' in engines without a throttle plate. Engine speed is controlled by the engine control unit/engine management system (EMS), which regulates fuel injection function and ignition timing, instead of having a throttle plate that restricts the incoming air supply" As always, they base info on articles and one can research the notes that lead to the articles. So at this point, let's go back to the FA20DIT. Last edited by Vlad; 04-25-2014 at 09:40 AM. |
04-25-2014, 12:55 PM | #89 |
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Can anyone list all of the different things that are connected to the crank pully? A/C compressor, alternator, etc.
Last edited by Sinsear; 04-25-2014 at 01:07 PM. |
04-25-2014, 01:58 PM | #90 |
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A/c, alternator, power steering. Just like any other car, unless they switched to electronic power steering.
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04-25-2014, 02:00 PM | #91 |
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04-25-2014, 02:03 PM | #92 |
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you can sort of see what the belt is doing 8 mins into my monotone walk around vid
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04-25-2014, 02:28 PM | #93 |
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04-25-2014, 05:46 PM | #94 |
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04-25-2014, 05:52 PM | #95 |
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04-26-2014, 07:35 PM | #96 |
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Anybody seen or try any TMIC setups yet?
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04-26-2014, 11:17 PM | #97 |
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04-29-2014, 11:12 AM | #98 |
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I can't wait for the first FA20DIT GC8 swap.
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04-29-2014, 12:54 PM | #99 |
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07-08-2014, 10:42 PM | #100 |
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I've been searching the past few days for info on fa20dit interchangeability with the old ej platform. I'm guessing the fa and ej platforms can't be used for a hybrid setup like we did with the ej205 heads and ej25 short block. Can anyone point me to post where people have looked using fa20dit heads on an ej25 short block? Or... Any threads about bolting the STi 6speed to an fa20 short block? The previous wisdom was any ej trans would bolt to any ej short block.... So I'm wondering if the fa bell housing bolt pattern is now different.
Last edited by EVL RS-T; 07-09-2014 at 07:25 AM. |
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