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09-20-2006, 10:59 AM | #101 |
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[quote=bboy;15059943]If AVCS is off, the cams are at a normal state of fully retarded. AVCS only advances the intake cam by up to 20 degrees, there is is no retarding of the intake cam from the 0 position.
QUOTE] Looking at one of my datalogs via delta dash: (AH581 Ver8 JDM ECU on a Ver8 EDM MY05 STi engine.) VVT Angle R MIN 0 MAX 23 VVT Angle L MIN 0 MAX 24 OVC R % MIN 43.9 MAX 55.7 OVC L % MIN 41.2 MAX 54.1 OCV Current MIN 512 MAX 640 OCV Current MIN 480 MAX 640 MAP 15 Richard Bulmer, MD of Tracktive Solutions & former MD of MOTEC UK says remapping a car to MAP 15 results in faster knock correction or something like that. I dunno he lost me when he started talking ECU gibberish. Anyway he is the one that mapped my WRX. Any of this help? I can add more info from my datalog if you think it will help.
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09-20-2006, 11:27 AM | #102 |
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Hydra can do open loop or closed loop. Mine runs in closed loop. As long as RPM and oil pressure are fairly consistant I would not think it would matter a whole lot either way.
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09-20-2006, 11:41 AM | #103 | |
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AFR is a poor predictor of torque if you are changing dynamic compression via camshaft changes, especially if you have boost blowing thru the intake and out the exhaust valve. No one has "duplicated" Clark's results, that is increased power/torque output at high RPM by advancing the intake cam......but they may in time. |
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09-20-2006, 01:03 PM | #104 |
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I just ran a little test using the DeltaDash dyno. Not a great scientific test (especially since I can't log timing, etc. at the same time), but still a reasonable test as DeltaDash has generally been consistent over runs for me.
In one run I set all AVCS points to zero, and in the next run I set all AVCS points to 30. These are third gear pulls because I don't have a place I can safely do fourth gear pulls from 2000RPM to redline in a timely manor (i.e. without have to circle the area many times to get free of cars, etc., etc.). The results show that on my car (with an SZ55) and with my current tune (poorly done by me), I generated more power below 4400RPM with AVCS set at 30 and more power above 4400RPM with the AVCS set at zero. It is very clear and the difference in power is wider at the RPM extremes and narrows the closer to 4400RPM I get. The difference (according to DeltaDash) is about 20ft-lbs on the low and and 40hp at the top. Again your car and tune may be different. But for me, running AVCS after 4400 seems to be a bad idea. I suppose I should also make a pull with AVCS at 15 across the board to see if that power line goes right through the middle of the ones I just did. Last edited by root; 09-20-2006 at 01:56 PM. Reason: Fixed cross over RPM |
09-20-2006, 01:13 PM | #105 |
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Be carful guys. Blindly advancing the cams like that can be dangerous. Remember that the Dynamic compression is changing. You can put yourself right into Knock city in no time just doing that. Baby steps!
The Hydra for the WRX is open loop. It is pulsing the Solenoids but has no idea the actual cam advance. The Stock ECU runs an alignment to zero the cams. It is closed loop and constantly adjusts to keep the cams with in a degree or two from bank to bank. Clark |
09-20-2006, 01:50 PM | #106 |
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Aye Clark. I did this on an already conservative map (and my eye on my knock light).
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09-20-2006, 01:54 PM | #107 |
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Clark, in previous posts you seem to imply that what I found here isn't really correct with regards to the AVCS values that make the most power. Yet most others think it is (it seems). Is there something wrong with my test? I'm not sure how I can see you getting those huge power gains by just changing AVCS since the stock already has zero in the top end. Unless it has more to do with the VF39 running out of breath. Do you use the same AVCS for larger turbos?
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09-20-2006, 02:25 PM | #108 |
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Just ran the same test using 15 degrees across the board. Interesting. It wasn't sandwiched between the 0 and 30 tests. In fact, it made more power than either the 0 or 30 from about 3800RPM to 5000RPM (give or take a 100 or so). We aren't talking about huge differences in power (until the upper RPMs), but they appear to be there.
FWIW, the IATs for the three tests (as reported by DeltaDash) were within a few degrees of each other (100F for zero, 99F for 15, and 102 for 30). I guess the 15 degree test had the coolest air, which is worth a little power, possibly. I think they are close enough though not to have really altered the result. I am running a FMIC for the record. |
09-20-2006, 02:36 PM | #109 |
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With larger turbos I run a different map to aid in spool up. A larger turbo provides more air at a later rpm... So you need different values.
I believe your test is flawed because you are only changing one variable.. The AVCS timing.. You are not changing Ignition timing or fuel. You must change all three to get the gains I see. Clark |
09-20-2006, 02:42 PM | #110 | |
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Are you suggesting that you can get more power up top by advaning AVCS, which in turn lets you pull fuel or add advance, then you can by tuning fuel and ignition using zero values for AVCS up top? (How's that for a long sentence?) |
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09-20-2006, 03:13 PM | #111 | ||
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Of course, this starts looking similar to the stock AVCS maps... |
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09-20-2006, 03:34 PM | #112 |
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I wonder why the wrx is open loop if they have the sti hydra doing closed loop maybee needs an update??
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09-20-2006, 04:04 PM | #113 | |
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TMS, You lost me. Please explain (if you have the time). To me, if I am using the same WGDC and the boost is more, then VE is better. VE is basically how efficient the air pump is. More VE means more air. ... wait ... UNLESS you are referring to the possible idea that boost is going straight through the motor (raw boost, not utilized in the ignition event). This could theoretically spin the turbine faster and create more boost. But, then again, you could also say that more air was trapped during the combustion even that that TOO would end up yielding more boost. The MAF voltage did go up. t |
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09-20-2006, 06:28 PM | #114 | |
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I'd never heard compressor surge at this low of a load/RPM, but now I know. Edit: I take it all back. Engine is now dead. I'll post back if I find that the pistons were hitting the valves. Last edited by bboy; 09-26-2006 at 04:06 PM. |
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09-20-2006, 06:33 PM | #115 | |
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09-20-2006, 06:35 PM | #116 | |
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TMS |
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09-20-2006, 06:50 PM | #117 |
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Thanks to all who have contributed to this thread.
It's clarified my thinking a lot. I'm back at the air pump model of an engine and AVCS ends up being an extremely sophisticated valve that lets air into the engine. Boost and exhaust back pressure play a critical role. If the exhaust pressure exceeds the manifold pressure, AVCS hurts power. If the manifold pressure exceeds exhaust pressure, AVCS can help power, but more advance is not always better, at some point you are throwing away your induction charge. Off boost AVCS follows some similar rules, but there AVCS can help more with induction gas velocity as bigger cams do in general on NA cars. In general AVCS is permiting an induction charge with more oxygen and less exhaust dilution by either blow thru or scavenging. Either way, with more pure air the dynamic compression ratio is improved. Higher dCR means more efficient burning of the existing fuel, higher peak cylinder pressure (power), and larger exhaust gas volume (possibly velocity as well). The OEM AVCS map may be used to some degree as an exhaust gas recirculation system. This has nothing to do with power, but does improve economy and NOx emissions. Other than that summary, get to a dyno cause your never be able to guess how to tune more power. |
09-20-2006, 08:40 PM | #118 | |
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If the above is true in our cars, then more AVCS advance means higher compression and less AVCS advance means lower compression. Which almost doesn't sound right given my earlier tests (assuming increasing compression would yeild a bit more power, but I made more up top with less advance (everything else being equal in the tune)), but this is all just hurting my brain... so someone please set me straight. |
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09-20-2006, 08:41 PM | #119 | |
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It was offered to me for my personal WRX but never felt the need as I was able to get maxium peformance out of the system. It's like a manual boost controller vs. a complex electronic. They both have their respective advantages but sometimes simple is better. I perfected my open loop AVCS map gettinga 75 lbs compressor to hit 20 psi by 4100 rpm. I always warm my car up as should most before jumping on it so the cold oil issue wasn't a factor. My STI runs the closed loop AVCS Hydra and that's great also Thanks, Phil www.elementtuning.com |
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09-20-2006, 09:47 PM | #120 | |
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09-21-2006, 06:37 AM | #121 | |
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If you have bigger cams with more overlap, I'd say retarding them fully is likely the way to go at high RPMs - smaller factory cams might like a small amount of advance to achieve both exhaust scavenging and allowing more charge into the cylinder... |
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09-21-2006, 12:10 PM | #122 |
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That's where I am. The aftermarket cams already have about as much overlap as the owner wants -- if I wanted more, I would have bought bigger cams. The whole cam design is geared toward high end power. With the stock cams you are looking a virtually no overlap, so introduction of some, I could see as beneficial.
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09-21-2006, 12:17 PM | #123 | |
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09-21-2006, 01:11 PM | #124 | |
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Boost is not the air that the ingine is not ingesting. Boost is fresh air. Period. Boost is created via a spinning turbine. The faster you spin the turbine, the more boost you create. Simple as that (yes, I know that you are aware of all of this ). So, we need to answer the question as to why advancing the intake cam allows for the turbine to be spun faster and how THAT relates to the VE of the motor. More airflow in the preturbo exhaust means a faster spinning turbine (assuming static WGDC). More exhaust airflow CAN be due to consuming more air/fuel during combustion do to trapping more of the intake charge (and the exhaust helping to pull in the new charge a tad bit). That would mean a higher VE since we are trapping more air/fuel during the combustion stroke. So, in relation to a faster spinning turbine, how are you determining that you have LESS VE?. t |
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09-21-2006, 01:24 PM | #125 | |
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there isn't a doubt in my mind that this is true. |
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