Street Tuner/Access Tuner Race Discussion Thread

[CasopoliS]

Edmundu HOOKED it up. Hitting boost again and the car is like a rocket-ship. I will do some logs later, but it is running good.

[CasopoliS]

casopolis, can you post a datalog in the datalog results thread? I would love to see what this turbo can do.

 

yea once I get back on the dyno and finish up with timing I will. Its capable of a lot.

[CasopoliS]

Here are my most recent maps, and my logs from the map.

 

right-click save as

 

www.casopolis.com/tuning/TUNER_070325160709.csv

www.casopolis.com/tuning/TUNER_070325160637.csv

www.casopolis.com/tuning/pure7d.str

www.casopolis.com/tuning/pure2d.stb

 

my boost still takes a while to come on compared to before, and is lower across the board.

 

http://www.casopolis.com/images/EU_ST_revD_boost.jpg

[mickeyd2005]

Wow. That's very impressive.

 

Is that knock between 3100 and 3200 rpm? I didn't see KC logged, but total timing is pulled by 3 degrees in both logs.

 

Maybe subtract one or two degrees of base timing between 2900 and 3200 rpm?

[CasopoliS]

Wow. That's very impressive.

 

Is that knock between 3100 and 3200 rpm? I didn't see KC logged, but total timing is pulled by 3 degrees in both logs.

 

Maybe subtract one or two degrees of base timing between 2900 and 3200 rpm?

 

well right now I am running the purple boost curve above... I want to get back to the red boost curve

[rc0032]

Wow. That's very impressive.

 

Is that knock between 3100 and 3200 rpm? I didn't see KC logged, but total timing is pulled by 3 degrees in both logs.

 

Maybe subtract one or two degrees of base timing between 2900 and 3200 rpm?

Time for WI

 

yea once I get back on the dyno and finish up with timing I will. Its capable of a lot.

Its so easy why go back to the tuner

 

 

I did around 3.5 hrs of tunning today and things are finally falling into place

[CasopoliS]

Time for WI

 

 

Its so easy why go back to the tuner

 

 

I did around 3.5 hrs of tunning today and things are finally falling into place

 

I'm a n00b. If it was not for Edmund I would have no idea what to do. Plus, the tuner is doing the rest for free. (I paid him for 2.6 hours of his time + hookup fees for yesterday). If I had a WB, I could do it better with some help from others.

[CasopoliS]

I think the turbo went out on me this morning....

 

http://www.legacygt.com/forums/showthread.php?p=1073443#post1073443

[edmundu]

well right now I am running the purple boost curve above... I want to get back to the red boost curve

 

I just looked at the details of the graphs, and the red curve was done in 14* cold dense air:eek: ! Compared to the map I sent you being logged in 80* air, huge difference. You really cannot compare the 2 with that big of an air temp delta.

 

If you graph out the latest map I had sent, it fairs even closer to the original's(red), and yet it is still in 80* temps:icon_mrgr. This temp difference also has a direct impact on what MAF grams/sec you can flow....

[CasopoliS]

sweet yea I just looked at the boost curve. Thanks man.... that is great! It is shifted to the right a bit, probably due to temps, but the slope is about the same (i.e. super fast spool once it starts).

[BlackGT]

Just wanted to chime in that I've got ST now, with a VF39 (non-sti swap), and I can't wait to get tuning, I should be starting her up this weekend.

 

Cassopolis, we met last year, I drove down from MI and bought some stuff from ya-

 

Are most of you using COBB's AVCS stage 2 levels of cam timing? What is this trick of super-quick spool that edmundu keeps hinting at?

 

Jeremy

[rc0032]

^ I am for now. If you read over Cobbs tuning progression steps thats one of the last things.

 

Are you on Stock injectors?

 

If you are having spooling issues with a VF39, never go bigger

[bugblatterbeast]

depends on your manifolds. if you have headers, you will loose some spool up if AVCS isn't adjusted a bit. FWIW, tuning AVCS on the street is a real PITA. I've found that you need to combine the data from 4-6 identical runs before you get data which is statistically valid.

[CasopoliS]

depends on your manifolds. if you have headers, you will loose some spool up if AVCS isn't adjusted a bit. FWIW, tuning AVCS on the street is a real PITA. I've found that you need to combine the data from 4-6 identical runs before you get data which is statistically valid.

 

so to the tuning guys.... I have coated headers with integrated uppipe. They are NOT equal length.

 

here is my current avcs. to get better spool, do I concentrate on the entire table, or just a certain region (i.e. lower rpms). Would I increase all the values by a certain %, or decrease? Do I increase an entire column, or row... or both? Some guidance here would be appreciated... just to get me started. I want to have an understanding here of what I am doing.

 

Christian, if you do not want the COBB values posted I can remove this image. I figured with ST being out... this stuff is fairly public at this point.

http://www.casopolis.com/images/7f_avcs.jph

[edmundu]

• Never, ever, place anything but 0's in the last row under higher loads in particular, but I would just leave it at 0 across the entire row. (Because whatever value is in the cell last, stays. Effectively you will leave AVCS On. You only want it ON during the low-mid range rpm's, not after.)
  
• Start around the center 'ish of the table, and gradually add more timing advance. Keep the existing tapering model, and it needs more added in the lower rpm's. Say 3.2k & under.
  

 

Now, the concept is simple. an engine is only an air pump. The more it can pump, the more power made. But to explain the details of AVCS is tougher, as it isn't very well understood by many, including myself.

 

Ok, so at lower rpm's, you want to minimize the pumping losses associated with expelling the exhaust gases, so if you advance the intake cam timing:

 

1. You are using the incoming charge to help blow out the burnt gases. And effectively allowing more time for the intake cam to be open, hence better cylinder filling.
   
2. And secondly, by allowing the intake cam to open earlier, you are buying more time for the cylinder to fill with a fresh mixture.
   
3. And thirdly, the bit of air/fuel mix that gets out unburnt past the exhaust valve will burn in the exhaust piping, helping to fuel the turbine blade, and this contributes to better spoolup.
   

Now, the reason for not wanting any AVCS timing after say 4.8k rpm's , is that the engine is volumetrically most efficient in this range, the engine speed itself is no longer as advantageous, mostly due to having the incoming charge go right through the cylinder, and out the exhaust valve along with the burnt gases. Wasting the precious new charge unnecessarily. Especially since it took work to get it there, only to see it get blown out the exhaust.

 

Now combine all of the above, and you have a pretty good picture of what AVCS can do.

 

Caution: By changing around the AVCS timing, you may likely also need to adjust your primary timing tables, as these AVCS changes do affect the timing needed. So you have to watch your middle cell areas on the tables, and be ready to take some out, if you get some pinging.

 

And finally, with the vfxx turbo's especially, and 18g's too, you will be getting the dreaded driveline vibration if you have tweaked the AVCS well. This is due to the increased torque being produced by the engine in the 2.5-3.5k rpm range;) I have purposely tuned this out on my setup, cause I feel I don't need that much torque in that rpm band:) And this really helps the bigger turbo's more so than the smaller ones.

[CasopoliS]

yes I get the vibrations in that RPM range. fun fun. I don't know how much of avcs my tuner plans to touch. It seems he is only going the basics and leaving everything else at COBB OTS defaults.

[rc0032]

You can do that yourself, save your $$

[CasopoliS]

You can do that yourself, save your $$

 

its free. I have already paid for 2.6 hours + setup and left without what I went in there for. Thus.... they are willing to help me out and finish the tune.

 

Plus, I really could not do it myself. If I was in the car with someone while they were tuning and the guided me.... I could pick up on it quickly. But over the internet here is not the same as face to face.

[bugblatterbeast]

Now, the reason for not wanting any AVCS timing after say 4.8k rpm's , is that the engine is volumetrically most efficient in this range, the engine speed itself is no longer as advantageous, mostly due to having the incoming charge go right through the cylinder, and out the exhaust valve along with the burnt gases. Wasting the precious new charge unnecessarily. Especially since it took work to get it there, only to see it get blown out the exhaust.

 

 

 

I agree with most of the post except for the reason for dropping the AVCS timing at high RPMs. At the higher RPMs, the turbine inlet pressure comes up quite a bit more than the intake manifold pressure. Any non zero AVCS at higher RPM + high load causes the volumetric efficiency to drop. During my tuning I found the threshold by taking a pull with zero AVCS, then one with ~4 degrees while logging MAF and RPM. The zero AVCS and 4 degree curves (for maf flow) will cross somewhere between 4 and 5k rpm. You want to drop to zero a bit before that point.

 

At low loads, AVCS can be adjusted but hooking a high speed pressure transducer into the intake manifold and looking at the shape of the pressure pulse you get in the manifold as you vary AVCS. The pressure pulse gets deeper untill you push the AVCS a little too far, then you get a really noisy looking waveform from exhaust gasses washing back into the intake.

[bugblatterbeast]

one more thing to keep in mind.... at very low RPMs (say sub 1600) there isn't much gas velocity in the manifolds. as a result, you can't count on the gas momentum to help fill the cylinder with a late IV closing event. you can raise the effective compression my moving the IV closing such that there's no back wash, but you need to keep an eye on timing

[bugblatterbeast]

so to the tuning guys.... I have coated headers with integrated uppipe. They are NOT equal length.

 

here is my current avcs. to get better spool, do I concentrate on the entire table, or just a certain region (i.e. lower rpms). Would I increase all the values by a certain %, or decrease? Do I increase an entire column, or row... or both? Some guidance here would be appreciated... just to get me started. I want to have an understanding here of what I am doing.

 

Christian, if you do not want the COBB values posted I can remove this image. I figured with ST being out... this stuff is fairly public at this point.

http://www.casopolis.com/images/7f_avcs.jph

 

which brand header are you using? if it is gruppe-s or gt-spec, send me a PM on the weekend and I'll forward you what I have.

[Christian.]

Just wanted to throw out some ideas/comments to try and help out.

Now, the reason for not wanting any AVCS timing after say 4.8k rpm's , is that the engine is volumetrically most efficient in this range, the engine speed itself is no longer as advantageous, mostly due to having the incoming charge go right through the cylinder, and out the exhaust valve along with the burnt gases. Wasting the precious new charge unnecessarily. Especially since it took work to get it there, only to see it get blown out the exhaust.

Generally speaking, once the vehicle gets into boost the exhaust gas back pressure is ~1.3-2X higher than manifold pressure so you cannot really blow through the motor to the exhaust. This is especially true on the turbo Subarus since the turbine A/R is usually smaller to help harvest the exhaust energy since the turbo is mounted much further away from the energy source (exhaust port) than normal. Look at any other turbo production car and you will notice that the turbo is very close to the exhaust port for a reason...it is more efficient there.

I agree with most of the post except for the reason for dropping the AVCS timing at high RPMs. At the higher RPMs, the turbine inlet pressure comes up quite a bit more than the intake manifold pressure. Any non zero AVCS at higher RPM + high load causes the volumetric efficiency to drop. During my tuning I found the threshold by taking a pull with zero AVCS, then one with ~4 degrees while logging MAF and RPM. The zero AVCS and 4 degree curves (for maf flow) will cross somewhere between 4 and 5k rpm. You want to drop to zero a bit before that point.

I am not saying you are wrong, just giving another perspective. The turbo inlet pressure never comes up. During WOT runs, turbo inlet pressure usually decreases in pressure to a point then flat lines to redline. This occurs even when boost drops. The turbo inlet pressure will always be lower than manifold pressure unless the motor is at idle then less pressure will be in the intake manifold vs. the turbo inlet. I have some dyno graphs with manifold pressure and turbo inlet pressure measurements if you would like me to post them?

 

An objective of AVCS is to create more VE in the lower RPM ranges. Most vehicles with AVCS (of some form) have retard built into the camshaft. This is because we do not currently have the ability to advance and retard the camshafts. Since we can only advance the camshafts, most camshafts have retard built into them so that when you shut off AVCS the camshaft goes to a retarded position...creating more VE in the higher RPM ranges. With that said, you can use camshaft advance at the lower RPM ranges to create greater VE at lower RPM ranges and you shut of AVCS in the higher RPM ranges to create greater VE through the natural camshaft retard ground into the camshaft...make sense?

At low loads, AVCS can be adjusted but hooking a high speed pressure transducer into the intake manifold and looking at the shape of the pressure pulse you get in the manifold as you vary AVCS. The pressure pulse gets deeper untill you push the AVCS a little too far, then you get a really noisy looking waveform from exhaust gasses washing back into the intake.

Just another perspective, I would suggest you use a chassis dyno to measure greater VE so you can see the effect of your AVCS changes. More torque would be a result of greater VE. You would need $$$ equipment to use the data from a high speed transducer and then you would still not be looking at what you are tuning for...more torque.

Now, the concept is simple. an engine is only an air pump. The more it can pump, the more power made. But to explain the details of AVCS is tougher, as it isn't very well understood by many, including myself.

Bingo, the engine is an air pump and with AVCS you are trying to make the air pump more efficient over a broader RPM range. Understanding that the engine is an air pump is very critical.

You are using the incoming charge to help blow out the burnt gases. And effectively allowing more time for the intake cam to be open, hence better cylinder filling.

This is only true until the exhaust gas back pressure exceeds the inlet charge pressure.

Now, the reason for not wanting any AVCS timing after say 4.8k rpm's , is that the engine is volumetrically most efficient in this range, the engine speed itself is no longer as advantageous, mostly due to having the incoming charge go right through the cylinder, and out the exhaust valve along with the burnt gases. Wasting the precious new charge unnecessarily. Especially since it took work to get it there, only to see it get blown out the exhaust.

The inlet charge air pressure is usually lower than the exhaust gas pressure so the exhaust gas is usually pushing back on into the cylinder when given the opportunity. The concept of blowing through a cylinder is changing drastically with the introduction of direct injection. With direct injection you can more efficiently blow out the dirty charge with proper camshaft design/calibration. This will allow for a cooler, cleaner charge to come in and no gas will be waisted (sprayed through to the exhaust) since the injector is not spraying on top of the intake valve...this next few years is going to be very interesting with these new technologies coming out.

 

I hope this helps,

Christian.

[CasopoliS]

Ok guys need some analysis of my logs.

 

This morning it was a little colder and I experienced fuel or boost cut... I don't know. I got 1 pull in fine, but the second pull (hotter run) caused the cut. My last log was from gunning it in 2nd, then shifting into 3rd. I experienced some knock there.

 

right-click save-as

First run:

Around 4.1k - 5.2k my DA and timing drop about 2 points.

http://www.casopolis.com/tuning/032907_3rd_gear.csv

 

Second run:

Hit boost cut but no CEL. P0244 is programmed not to show though...

http://www.casopolis.com/tuning/032907_3rd_CUT.csv

 

Third 'run':

Shifting from second to third gear in this one. Knock was shown once I hit third gear....

http://www.casopolis.com/tuning/302907_2nd_3rd_knock.csv

[bugblatterbeast]

Thanks Christian. Now I'm really confused. I think we are saying essentially the same thing but are referring to different points on the turbo. By turbine inlet pressure I was referring to the pressure before the turbo on the hot side. Based on your comment about the inlet pressure being slightly below the manifold (except at idle) I'm guessing you are talking about the cold side just before the compressor. I agree that the pressure just before the compressor will drop as flow increases and level off as one near choke flow. For the hot side, I was always under the impression that the pressure was around 2x boost at stock flow levels but possibly 2-3x boost when one abuses the turbo Are we talking about different things here?

 

Just so I'm clear (I've been trying to figure this out for a while) is this the case:

 

at very low RPMs, the dominant effect is timing the intake valve closing so that the piston hasn't had a chance to push air back into the intake

 

medium rpms, we are making a compromise between intake manifold resonant effects and catching the exhaust scavenging pulse with the right overlap

 

high rpms/loads, the exhaust back pressure/turbine inlet pressure is now higher than boost so we want to minimize overlap so we don't expose the intake side to the exaust pressure during overlap

 

 

 

Just wanted to throw out some ideas/comments to try and help out.

 

Generally speaking, once the vehicle gets into boost the exhaust gas back pressure is ~1.3-2X higher than manifold pressure so you cannot really blow through the motor to the exhaust. This is especially true on the turbo Subarus since the turbine A/R is usually smaller to help harvest the exhaust energy since the turbo is mounted much further away from the energy source (exhaust port) than normal. Look at any other turbo production car and you will notice that the turbo is very close to the exhaust port for a reason...it is more efficient there.

 

I am not saying you are wrong, just giving another perspective. The turbo inlet pressure never comes up. During WOT runs, turbo inlet pressure usually decreases in pressure to a point then flat lines to redline. This occurs even when boost drops. The turbo inlet pressure will always be lower than manifold pressure unless the motor is at idle then less pressure will be in the intake manifold vs. the turbo inlet. I have some dyno graphs with manifold pressure and turbo inlet pressure measurements if you would like me to post them?

 

An objective of AVCS is to create more VE in the lower RPM ranges. Most vehicles with AVCS (of some form) have retard built into the camshaft. This is because we do not currently have the ability to advance and retard the camshafts. Since we can only advance the camshafts, most camshafts have retard built into them so that when you shut off AVCS the camshaft goes to a retarded position...creating more VE in the higher RPM ranges. With that said, you can use camshaft advance at the lower RPM ranges to create greater VE at lower RPM ranges and you shut of AVCS in the higher RPM ranges to create greater VE through the natural camshaft retard ground into the camshaft...make sense?

 

Just another perspective, I would suggest you use a chassis dyno to measure greater VE so you can see the effect of your AVCS changes. More torque would be a result of greater VE. You would need $$$ equipment to use the data from a high speed transducer and then you would still not be looking at what you are tuning for...more torque.

 

Bingo, the engine is an air pump and with AVCS you are trying to make the air pump more efficient over a broader RPM range. Understanding that the engine is an air pump is very critical.

 

This is only true until the exhaust gas back pressure exceeds the inlet charge pressure.

 

The inlet charge air pressure is usually lower than the exhaust gas pressure so the exhaust gas is usually pushing back on into the cylinder when given the opportunity. The concept of blowing through a cylinder is changing drastically with the introduction of direct injection. With direct injection you can more efficiently blow out the dirty charge with proper camshaft design/calibration. This will allow for a cooler, cleaner charge to come in and no gas will be waisted (sprayed through to the exhaust) since the injector is not spraying on top of the intake valve...this next few years is going to be very interesting with these new technologies coming out.

 

I hope this helps,

Christian.

[bugblatterbeast]

thanks the first bit actually answers a question I've had for a long time. I've been trying to figure out if our valve overlap goes to zero or goes negative when AVCS is set to 0.

 

I wish I had access to a dyno at reasonable prices.....sigh..... I can get my paws on pressure transducers, logging equipment and almost any electronics industry related instruments for almost nothing, hence the desire to find other ways of optimizing my setup. I know I have to shell out for dyno time at some point. if you ever need something x-rayed.....

 

 

Just wanted to throw out some ideas/comments to try and help out.

 

Since we can only advance the camshafts, most camshafts have retard built into them so that when you shut off AVCS the camshaft goes to a retarded position...creating more VE in the higher RPM ranges. With that said, you can use camshaft advance at the lower RPM ranges to create greater VE at lower RPM ranges and you shut of AVCS in the higher RPM ranges to create greater VE through the natural camshaft retard ground into the camshaft...make sense?

 

Just another perspective, I would suggest you use a chassis dyno to measure greater VE so you can see the effect of your AVCS changes. More torque would be a result of greater VE. You would need $$$ equipment to use the data from a high speed transducer and then you would still not be looking at what you are tuning for...more torque.

Christian.