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Old 11-04-2007, 06:41 PM   #301
root
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I was looking over some compressor maps a while back and found that a case could theoretically be made for advancing AVCS at the top end, depending on the turbo and engine combination. Whether or not I'll ever have the opportunity to test things out on a dyno is doubtful. My thinking could be way off base (not the first time).
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Old 11-04-2007, 06:48 PM   #302
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Ok. When on that note, what you can do it take it with step, tuning avcs, fuel and timing within that particular range.

Example, 1000rpm ranges after that point.

If you have access to a dyno, that would be great, but if not, reviewing the VE can help.

The only problem is the environment that is not controlled.

We look forward to your results and success.

Last edited by west_minist; 11-04-2007 at 07:15 PM.
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Old 11-04-2007, 06:59 PM   #303
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I don't think there is a set rule to always taper by a given RPM. It doesn't make sense.

Here's my understanding of how it works, hopefully, it will give you some direction in things to try. It's kind of a cliff's notes for this thread......

Advancing the intake cam will effectively raise the compression of the motor, however, as backpressure increases, the mixture in the cylinder becomes contaminated with recycled exhaust as opposed to fresh air.

Backpressure depends largely on the turbo, specifically the hotside size. A different header could also affect things if it is better-designed than the stocker. In any case, the more you relieve backpressure at the exhaust port, the more you will be able to take advantage of adjusting the intake cam.

Running a 35r with a 1.06 hotside should flow very well and allow for advancing the cam later in the RPM range. On the contrary, a stock turbo will become a restriction and advancing the intake cam will not yield any benefit.

I haven't been able to play with different cams, however, different cam efficiency will play into whether or not advancing the intake cam will yield any good results. I am guessing this has to play into Jay's findings.

Remember since you are affecting the efficiency of the motor, you may need to change AFRs and timing to optimize the new settings. For example, if you can make the same power by changing AVCS but removing a few degrees of timing, you are on the right track since you've improved the VE of the motor.

If you were to draw out the 4 stages of a combustion motor, it might make more sense. Think about what happens as the stages get faster and faster.

Hope that helps. Again, this is what I've come to understand and it seems to work for me.


Mike
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Old 11-05-2007, 01:53 AM   #304
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^^^This actually tracks well with what I've started seeing on the dyno since tuning on one. The AVCS for a VF39 is far different than for a FP Red, or even a TD04 for that matter. Seeing a bigger torque plateau and a bit more peak torque makes people happy thats for sure. Haven't had too much time to play with AVCS yet, takes too long to tweak without realtime tuning when you've got 2 hours to finish a tune.
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Old 11-05-2007, 07:47 AM   #305
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My header cracked [again] but I have provisions for a backpressure gauage now. I'm going to see if I can find an electronic sender than can handle enough heat and pressure so that I can log backpressure in the uppipe and relate it to manifold pressure. That should give me a big hint in how to map AVCS. Once I get the header situation resolved, I can get back to tuning.
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Old 11-05-2007, 09:09 AM   #306
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Here is my present AVCS map. Important mods are a .82ar gt35r and cosworth 278/274 avcs cams.



Lately I've been playing with AVCS advance under light throttle / low load. Advance in the 0.85-1.15 load area has a nice effect on responsiveness (i.e. the turbo is spooling as soon as you lean into the throttle).
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Old 11-05-2007, 09:30 AM   #307
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Jay,

What happened when you added advance after the turbo spooled up? Did you boost increase? Did your load decrease?

Thanks,
Mike
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Old 11-05-2007, 09:34 AM   #308
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Boost goes down, but I only tried adding AVCS under boost up till about 6k rpms. I pulled out AVCS in that region and bam, overboost.
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Old 11-05-2007, 09:41 AM   #309
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Quote:
Originally Posted by jays05 View Post
Boost goes down, but I only tried adding AVCS under boost up till about 6k rpms. I pulled out AVCS in that region and bam, overboost.
If boost goes down but you are making the same engine load, you have done a good thing, so you might want to try retuning with some cam advance and see what happens. Less boost and/or less timing yielding the same power is the direction you want to move in.

Boost is a measure of restriction, and by advancing the cam, it's quite possible you are allowing the engine to breathe better and make power more efficiently.

Mike
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Old 11-05-2007, 03:33 PM   #310
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I agree with what crazy mikie has posted with regards to backpressure. I generally only get away with adding a bit of advance at lower rpm on stock turbo cars, and relax timing at the same load/rpm. I can get away running way lean on my own GT30 .82 at low rpm with lots of advance, I can run 14.0:1 up to 4-5 psi no problem (no knock), but that doesn't work on smaller turbo cars, which will exhibit hesitation if they're run too lean or with too much advance. Running that lean seems to hurt torque a lot even though it does move boost threshold down. Overall my own car is running just a butt load more advance overall than I seem to be able to get away with a larger bolt on, say, like an FP Green 8cm IW. It's probably +8-10 CA more from 2800 to 5500. Granted, I've had far more time to mess with my own car as well, and I've spent more time actually attempting to run more advance while avoiding the hesistation/misfire behavior that seems to accompany running too much cam advance in the lower ranges.

In upper ranges, like 6000+, running more advance seems to hurt airflow and require more WGDC to maintain boost. I've made no attempts to run extra advance above the range where I find I'm moving back to zero. I guess the trend could reverse itself, but it doesn't seem to make sense that it would.

I'll probably post some maps later. I'm very interested to pick up a EL header and see how it affects what I can get away with. I want to get one for next season.
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Old 11-05-2007, 05:05 PM   #311
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Quote:
Originally Posted by Freon View Post
In upper ranges, like 6000+, running more advance seems to hurt airflow and require more WGDC to maintain boost. I've made no attempts to run extra advance above the range where I find I'm moving back to zero. I guess the trend could reverse itself, but it doesn't seem to make sense that it would.
That's kind of a contradiction- if you are seeing less boost with the same wgdc, then you are removing a restriction and you might be moving more air. Do your engine load and MAF voltage drop as well or does boost drop while the others stay the same?
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Old 11-05-2007, 07:24 PM   #312
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Eh, yeah I think you're right. I'll go back and look at the logs.

Anyway, here's my suggestion to start with for a basic stage 2 car compared to stock:

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Old 11-05-2007, 07:42 PM   #313
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I'll try to get some logs up this week too- I have an interesting combination (ej207 with td06h-20g 8cm^2). The hotside of that turbo is relatively large so it will be interesting to see what I can do in the upper ranges.
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Old 11-06-2007, 03:11 PM   #314
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If I posted my AVCS maps for each bolt on and rotated turbo the next day ever single tuner out there would copy and paste them into the maps. I help just about every tuner out there as it is now and I have trained more then 50% of them in person. I continue to help armchair tuners and even Book smart NO EXPERIENCE engineer types as a service to this community.

That being said I am always glad to help and you can always ask questions. But my AVCS map that makes 20whp more then anyone in the biz will not be posted. Sorry. I spent years fine tuning it.

Clark

Quote:
Originally Posted by west_minist View Post
Guys,

I cannot speak for AZScoobie, but I may be right in staying this.

I believe he would like to post his findings, but because it is a very competitve environment and you need the edge, you do not want to give away detail trade secrets.

The same will go for others, including myself.

Where I am located, there is strong competition and people takes other people work and call it theirs.

I hope everyone understand this and not to be hard upon us.

Cheers,
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Old 11-06-2007, 09:27 PM   #315
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I would love to see a dyno comparison of a protuned car before and after the AZScoobie AVCS maps (with that being the only change between runs). 20whp is a pretty bold statement.

Not saying it's impossible, but plenty of other tuners have also spent considerable time experimenting with, learning, and improving the avcs values.

BTW, what's your rate for helping armchair tuners over email?

We definitely appreciate the help you've given us thus far in this thread alone.
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Old 11-06-2007, 10:22 PM   #316
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I dont charge anything for help man. I get 2 to 5 emails a day with dyno plots and logs. I always respond with advice. It may work or it may not. I am here for this community. Ask away. I might know the answer or I might not. I have the lux of having alot of experience that might be helpfull.

C
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Old 11-06-2007, 10:30 PM   #317
Evan
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Quote:
Originally Posted by varmint007 View Post
I would love to see a dyno comparison of a protuned car before and after the AZScoobie AVCS maps (with that being the only change between runs). 20whp is a pretty bold statement.
Me too! It would help me justify using STi heads w/ AVCS when I put a 2.5L in my 02 wagon instead of using stock WRX heads. I will be going to Clark for a tune when the time comes.
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Old 11-07-2007, 02:02 PM   #318
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Eh, ignore that errant 1.0 at 7600rpm... It should be zero.
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Old 11-07-2007, 02:13 PM   #319
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I was gonna say, that 1 degree at 7600 must be helping a lot
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Old 11-07-2007, 09:47 PM   #320
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After playing with AVCS for awhile I only see improvements in the mid torque range (yes it could be 20 hp there) and with boost onset (picked up about 200 RPMs with more aggressive advance on a GT65). One has to be careful not to induce knock with the increase in dynamic compression at low RPM. Bigger cams help on the top end, but I've not more with intake advance at high RPM.
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Old 11-07-2007, 11:52 PM   #321
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...after having played with this for a while, now......I think 20whp across the midrange is well within reason for optimized AVCS.....my car with the stock turbo seems to pull pretty well....

....much to the consternation of some of the locals
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Old 11-08-2007, 02:59 AM   #322
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So what do you guys think of this one, and Clark I want your opinion too


This is NOT my map by the way, this is by a open source tuner who works at a shop that has also created the ugliest ignition timing table I've ever seen as well (25 degrees of timing at idle? Why not?)
Anyway this is supposed to be from a Stage 2 STI with upgraded TMIC running 22 psi of boost. IMO there is way too much advanced here, in my experience on the dyno so far adding any AVCS after 5200 has hurt power/torque and had a noticeable increase in EGT. There might be some thing to adding a bit over 5200 with the right timing and fuel if I had enough time to play around with it, but this map just looks crazy.
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Old 11-08-2007, 10:17 AM   #323
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The scaling in the last few columns is funny.

I've had similar experiences to you- advancing the intake cam on that small turbo doesn't really help at higher RPM. I've never been able to try it on a dyno, but all of the logging on the street I've seen points to less power.
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Old 11-08-2007, 12:09 PM   #324
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I am currently trying to sort knock issues that may or may not be related to AVCS tuning. I would like to get a few more eyes looking at my problem.
My set up is:
02 WRX
V7 EJ207 W/ECU and AVCS
Everything else is stock USDM WRX (Turbo/Injectors/Intercooler)
Catless UP/DP

The AVCS map that I have been running was a stock JDM WRX 2.0 map. I have been getting knock only in 5th gear from 2500 rpm up to about 3000 rpms in the 1.3 - 2.3 load range. I can see boost any where from 7-18 psi in this range but the knock has been independent of any particular manifold pressure. My timing is pretty low in this area and AFR's are in the 11.5:1 range. I pulled a couple of degrees of advance out of the map and flattened out a spot in the problem area but this didn't help a whole lot. It actually seemed to result in boost spiking, so I need drop my WGDC's even further, this engine can spool the TD04 ridiculously fast. At this point I am not really sure what to do or if this AVCS map is way off.
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Old 11-08-2007, 12:53 PM   #325
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aren't the EJ207s usually designed for the Japan 96 octane? The AVCS could be an indicator.
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