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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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06-04-2012, 12:55 PM | #29 |
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Generally speaking for this kind of system you can't spray during the compression stroke when the engine is warmed up unless it's going to be lean burn stratified charge. The 2JZ-FSE did that. We'll have to wait and see what people figure out for injection timing on the FA20. You would expect port injection to commence during the exhaust stroke (spraying on the back of the intake valve) and direct injection to spray during the intake stroke only.
Rule-of-thumb for injection timing on a single-injection-event GDI systems: spray too early, you hit the piston. Spray too late, there isn't enough time for mixture formation. It's going to vary with RPM and torque output. Of course the really expensive piezoelectric gasoline direct injection systems (Mercedes, BMW) are capable of 3-5 injections per stroke, but you won't see that on a cheap car like this. |
07-16-2012, 10:38 PM | #30 |
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As many of you know we are developing the the Hydra EMS for thethe FA20 and therefore we must first understand the oem DI strategy. I know more specifics about exact timing and durations than I will share but for the FA20 the direct injection under a WOT pull only fires on the intake stroke both BTDC and ATDC and injection timing is shorter at low RPM vs. High RPM as you would imagine. Now the port injection is not used under these circumstances until after 5k rpm.
At this point it doesn't appear the port injection is required for fuel delivery at high rpm in NA form and as suggested it could be related to catalyst temperature control. Until i actually try to utilize DI exclusively at these RPMs I'm only speculating from the data we've gathered. Thanks Phil Grabow |
07-17-2012, 12:12 PM | #31 | ||
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07-17-2012, 03:26 PM | #32 | ||
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Our testing just basically confirms much of how you thought this DI application is being used. |
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07-18-2012, 12:55 PM | #33 | ||
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The same type of principle applies when you are calculating cam phasing using the saw-tooth waveforms of the crank angle sensor and the high/low signals from the cam position sensors. You can calculate when the cam position sensor switches relative to the missing tooth, but you need to know baseline cam position to determine whether the cam is being advanced or retarded. So in the diagram below, where would "At certain RPM ranges the injection cycle starts BTDC (when RPM is higher). At lower RPM ranges the cycle starts ATDC" fit in? FYI again for anyone else reading: You see above some typical/representative Start of Injection (SOI) timings in terms of absolute crank angle degrees. I am referring to physical crank angle degrees. Here we see:
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07-20-2012, 12:58 PM | #34 |
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We are working on an AEM solution and similarly we are scoping the Direct injection Port injection, spill valve ETC. to verify factory operation, at this point all I can add to the discussion is that there are clearly some contradictions to how the DI is used compared to some of the early toyota papers.
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07-20-2012, 08:06 PM | #35 | |
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This is a different engine and naturally it's going to be different from a 6 cylinder luxury car. I can't stress enough that if you are comparing your own data with some other source that uses physical units (like actual absolue crank angle degrees) make sure your conversions are done correctly. Duty cycle and ON/OFF inputs are simple enough, but calculating timing can be tricky. If you are using automated software to calculate the injection timing, you have to figure out the offset between true TDC and the missing tooth of the waveform. It's also more accurate if you look at the CURRENT WAVEFORM not the voltage. Use a current probe that outputs a linear voltage signal proportional to the actual current in the injector. If you hook the scope or whatever equipment you are using up and read the raw voltage, you will pick up a ton of noise. This will be obvious if you are manually calculating injection timing at discrete points based on visually looking at the waveform. Simple automated software will be thrown off if you have it register an injection event based on some raw voltage threshold. Reverse engineering stuff with a scope is tricky and it's easy to misinterpret the data. |
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07-23-2012, 12:24 PM | #36 | |
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you are very correct sir. we are now running a patch harness, and using an AEM box to log the inputs and outputs on all channels, it is confirming some of the strangeness we were unsure of...we gained some insight into why the idle maybe is so shaky, after warm up it runs on DI only... |
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08-02-2012, 10:24 AM | #37 |
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Has anyone locked down the actual injector sizes yet? I know I estimated them based on the injector pulse widths but a oem flow number would be very helpful. If not I have found a place to test the DI injector.
You have a limited time and a fairly low maximum pulse width to get the job done with DI so timing with the port injection is critical as power is increased to the limits of the oem DI injectors. |
08-08-2012, 03:11 PM | #38 |
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So are these similar to the new VWs with a low pressure in tank pump and the high pressure on the cam?
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08-09-2012, 05:46 PM | #39 |
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10-07-2012, 12:18 PM | #40 |
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Question regarding the Denso DI EDU's which seem to be common place on all the d4-S systems in the last 4 years :-
Control of the Spill valve is done via the EDU's and from the wiring scematic the main ecu seems to supply one signal to the EDU regarding this (the other seems to be FP feed back to ECU for diagnostic purposes) After scoping can anyone confirm this is a 'fuel pressure demand' signal and thus Spill valve on/off and hence spill timing (output to rail stroke) is thus based on DI injector timing events? |
10-18-2012, 02:03 AM | #41 |
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10-22-2012, 08:14 PM | #42 | |
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