How's my LV?

[fahr_side]

Figured out why I got the P0244 error code. It was the cold weather coupled with the fact that my Init WGDC tables were mismatched to my Boost Targets. TD Integral and Proportional were both off the charts trying to compensate, capped out at 30% (Init WGDC was 0%, so 30% was the ceiling for compensation) trying to produce 10 lbs of boost. NOT happening. So when I mashed the gas pedal, boost built up quickly and Init WGDC went up to 65%, plus another 30% from TD, which capped me out at 90% based on the Max WGDC hard ceiling. When I hit target boost finally, TD integral was unable to wind down quickly enough so I was still at very high WGDC. TD proportional tried to remove some, but failed miserably. And BAM, P0244 code!

You know when you are on the right track when your initial table values get you very close to your boost targets and there's very little intervention from TD. I find that different approaches work better across the rev range.

 

At really low rpm, like up to 2k, I like to have boost targets quite a bit higher than the turbo could probably make. This makes sure timing is not pulled if say you're pulling up a hill with a full car and MAP does rise slightly into boost. You can have TD disabled at this point so it doesn't interfere and run as much as 90% initial WGDC to be sure you will get the earliest spool you can.

 

During spool I set the targets very slightly higher than what I can typically log even with WGDC up at 90%. This again makes sure timing isn't pulled when you do better than target, but the targets do not want to be unrealistically high as that just winds up TD like a coiled spring. If you let this happen, as the turbo reaches its own sweet spot boost will spike and TD will not be able wind back down to zero and go negative fast enough to keep you from a big spike there.

 

After the sweet spot I like to set initials just slightly too low to hit the boost targets and have just a few percent TD to keep on target.

 

 

Can someone answer this for me though: How do tuners determine what boost targets to run at? My peak boost is at 18PSI. But I have seen both less and more. How is it decided what to run? Like if you had no baseline to start from (i.e. we know Stage 2 LGT's go between 16.5 to 19.5 PSI peak, depending on the tuner), how would you figure it out blindly?

The work of others is very helpful. I always check to see what reputable tuners have done and what boost curve they ran with. I don't try to copy what others do but I respect their expertise and learn what I can from their work. If there is a good example out there, don't be shy to use it as a reference.

I'm no pro tuner so you could safely ignore the following. I always bear in mind that just because I can run higher boost, that doesn't mean I should. Without proper instrumentation it's hard to know when to stop and I wouldn't try to figure out the limits myself. Even with hard data to look at things can go wrong very quickly. Sure you can rely on things like WGDC being maxed out, having to pull too much timing, or add silly amounts of fuel to stop det telling you when to back off, but it's probably going to cost you an engine sooner rather than later.

 

I personally don't like the 'turbo-diesel' torque spikes you get when you tune for all-out maximum torque on the smaller turbos... I'd rather take a lower peak and smoother delivery as with my poor driving talents that makes my car quicker. I think that self-restraint and a lot of good advice have kept me out of trouble.... so far.

[iNVAR]

Thanks for your reply fahr. With regards to TD though, how do you suggest dialing it in though?

 

I did log TD this time and you can see where the spike is. It seems that TD integral is not winding down quickly enough once target boost is achieved, hence the slight overboost, which is not bad. I guess there are THREE ways to handle this:

1) adjust TD Integral so it winds down faster OR

2) adjust TD Proportional so that it instantly lops off some WG based on the overboost

3) or I could just leave it alone. I know 0.5PSI isn't a bad spike but I think I'd like to fix that anyway, or try to minimize it.

[fahr_side]

Do you have the stock BCS or a 3-port?

 

TBH, a consistent 0.5psi spike wouldn't cause me any lost sleep but I don't mind going through this.

[iNVAR]

Yeah, I'm not overly concerned with 0.5 either. Maybe I'll just leave it alone mostly and just up the TD integral limit from 15 to 20, which should allow boost to develop fully after 3600RPM. It was capping out even with TD proportional, and caused me to be short about 1PSI consistently higher up.

 

I guess the tinkerer in me just wants to mess with it and try to get it to be more precise.

[fahr_side]

Yeah, I'm also afflicted with a little OCD but try to keep it in check.

 

I like to keep initial WGDC after the saddle just a little lower than can hold the boost target... just enough to keep TD prop down in single digits and TD int at near zero.

The max TD int value I will use depends on a few things. Small turbos with 3-ports only need max 15% as it's easy to overdo it. Bigger turbo and or stock BCS can take 18 or even 20% to get proper control authority.

IMO it's best to set realistic boost targets and tune initial WGDC carefully to reduce TD intervention to very small positive values. I like to limit max WGDC to 3~5% above initial through the saddle and slowly open that out at higher rpm. Smaller turbos are especially sensitive to control input through the saddle and any clumsy intervention here from TD will see boost bouncing up and down dramatically.

One the great side-effects of per-gear boost control is being able to keep the max WGDC values much closer to the initial values because large TD interventions are never needed.

[iNVAR]

Oh, sorry, I forgot to answer that. It's stock BCS. On a side note, since I have you here and you can save me some time, I think next year I'm most likely going to get a BNR16G. (was deciding between that or BNR18G, VF52, and BNR68 but decided the 18G and 68 are too laggy, and a VF52, bleh, don't want a VF52 really :lol) I should still be fine with stock BCS on the 16G right? I'm assuming the advantages of an aftermarket BCS would be better control of the boost and... per gear boost control that you're talking about?

 

Hmm, my Max WGDC is 90% for WOT all the way till 6800RPM... If I change that, will it affect spool time?

 

I mean if I cap out Max WGDC to about 3-5% above what I'll realistically need when the turbo is already spun up (70% let's say, so I cap it at 75%), then on the occasion when I'm coasting around and the turbo's not spun up and I mash the pedal, TD it won't be able to shut the WG as much as I'd like to get things spun up.

 

Like all things, it seems like it's going to be a tradeoff between precision and speed, right? So I have to pick what's more important...?

[black318i]

Maybe I'll just leave it alone mostly and just up the TD integral limit from 15 to 20, which should allow boost to develop fully after 3600RPM. It was capping out even with TD proportional, and caused me to be short about 1PSI consistently higher up.

 

That is exactly what I had to do with TD with my Infamous tune.

 

Hmm, my Max WGDC is 90% for WOT all the way till 6800RPM... If I change that, will it affect spool time?

 

I mean if I cap out Max WGDC to about 3-5% above what I'll realistically need when the turbo is already spun up (70% let's say, so I cap it at 75%), then on the occasion when I'm coasting around and the turbo's not spun up and I mash the pedal, TD it won't be able to shut the WG as much as I'd like to get things spun up.

 

Like all things, it seems like it's going to be a tradeoff between precision and speed, right? So I have to pick what's more important...?

 

That is what I did with my own tune prior to my Infamous tune. I wound up leaving Max WGDC at 90 with my tweaked Infamous tune since TD and WGDC Comp. IAT were dialed in pretty good. I didn't notice much of a difference either way.

[fahr_side]

I was going to apologize to the OP for going so far off-topic.

Oh, sorry, I forgot to answer that. It's stock BCS. On a side note, since I have you here and you can save me some time, I think next year I'm most likely going to get a BNR16G. (was deciding between that or BNR18G, VF52, and BNR68 but decided the 18G and 68 are too laggy, and a VF52, bleh, don't want a VF52 really :lol) I should still be fine with stock BCS on the 16G right? I'm assuming the advantages of an aftermarket BCS would be better control of the boost and... per gear boost control that you're talking about?

Love my 16G!

 

Yes, you can tune boost on the 16G with stock BCS no worries, but the 3-port does make it much quicker and more accurate.

 

By per-gear boost control I mean this. Of course this approach changes the way you set up your tables and do fine tuning so let's skip this.

 

Hmm, my Max WGDC is 90% for WOT all the way till 6800RPM... If I change that, will it affect spool time?

 

I mean if I cap out Max WGDC to about 3-5% above what I'll realistically need when the turbo is already spun up (70% let's say, so I cap it at 75%), then on the occasion when I'm coasting around and the turbo's not spun up and I mash the pedal, TD it won't be able to shut the WG as much as I'd like to get things spun up.

 

Like all things, it seems like it's going to be a tradeoff between precision and speed, right? So I have to pick what's more important...?

OK, let me start by saying there is more than one way to skin a cat. I haven't seen a WGDC table that was at 90% from idle to redline but that's not to say it can't work.

 

In general, you need to keep the wastegate clamped shut for it to spool up and it's okay to allow TD make a lot of compensation there to make it happen. At high revs the (stock) turbo is quite reluctant to produce higher boost levels and quite a large increase has to be made in WGDC in order to prod it into action.

In the turbo's efficiency sweet-spot however it is ready and eager to spin up and push air. While you have to push it (via clamping the wastegate) a little to get it to spool, if you continue to push it too hard as you are approaching that point, by the time control input has started to pull back you will already have overshot the boost target and that's how you get that spike. It's a physics thing. There is inertia involved, the engine is accelerating and producing lots of gas. It takes a moment to change course.

One trick here is to limit TD input in the max WGDC table. Another is to start reducing initial WGDC before you normally see that spike.

 

This is how I do it and how I normally see it done for stock-size turbos. It's an STi stage2 tune but the principle will be the same for you. It doesn't feature per-gear boost control as the tables were not defined at that time.

 

http://i.imgur.com/YoKvz.png

 

Notice that in the initial table and in the max RT column, WGDC starts at 80% and is 80% again at 6k. In the middle there is a dip (saddle) which is centered at 3k6. This low spot coincides with the turbo and related gas-flow system's peak efficiency or sweet-spot. The turbo just wants to make boost there and doesn't need the BCS to push it much to do so, so we reduce WGDC there to avoid it just running away and overboosting. If you were at 90% initial there you can see that the TD system would have to pull back over 20% to prevent overboost.

At 6k4 the initial value is lower again because the boost target tapers off at redline as the VF-43 isn't happy pushing peak boost all the way to redline. This particular tune calls for a peak of 19.5psi at 3k6 which tapers off to 17.7psi at redline.

 

A simple way to arrive at a table like this is to log the actual WGDC values during a pull as these are what the wastegate is actually doing after all the TD and other compensations are applied. You can smooth that out and apply it to the last column and then try another pull. I usually find I don't need to make corrections as large as those suggested by actual values, something smaller will usually be enough.

 

Now take a look at the max WGDC table behind. You see the max values start at 10% over the initial values and go back to 10% over at 6k4. Through the saddle the max values come to within 4% of initial, this time from 3k6 down to 3k2 to prevent boost spiking starting there. Remember that the max values clamp the positive corrections from TD to be no more than the difference between the initial and max tables, though other compensations for atmospheric pressure, temperature etc. will still add up to a max set in the post-compensation max WGDC table. In most tunes it's set at 90%.

Again you can see how the saddle appears, this time both in absolute values but also in the amount of TD compensation that can be applied, because the turbo is just so much more sensitive to control input from the wastegate at this point. Lowering max WGDC through the sweet-spot and on into the higher rpm area cannot affect your spool. Just running 90% max WGDC right through the rev range shouldn't be necessary unless you are pushing the turbo right to the bleeding edge. It may, if the initial values are too low, allow TD to wind up too far positive. The rate at which it can unwind and head negative may be allowing some spikes to occur before WGDC can drop low enough to control it. You might have some very clever tweaking to the TD integral and prop tables which avoid this. I never feel comfortable tweaking those too far from what I know to work.

 

Remember TD max values don't have to be equal positive and negative. It's very common to use say max TDi of 8.00 and negative of -15.00 with a stock BCS.

 

Some other tricks:

 

You can always rescale the rpm axis on the table to make sure you have a cell right at the sweet spot or anywhere else that's causing particular problems. On many maps I will pack the rows more closely through the spool area just because things change so quickly as revs pass through there and more resolution often helps.

 

Boost control targets have to be realistic or TD will intervene with it's heavy hand. Enter targets in the spool area which are just slightly higher than you normally see in the logs but can be reached on a gentle uphill slope or a car full of passengers.

 

 

OK, I didn't really mean this to become a tutorial and I don't claim the right to create one. Big picture often helps understanding the details, but I may also have misunderstood the big picture somehow.

[iNVAR]

Thanks Fahr, I've been looking at my tables and comparing it to the logs and I see that my Initial WGDC table is way off from what is actually needed. I've made some adjustments to it, and need to do some pulls to test out my new changes.

 

I think you may have misread what I said earlier about WGDC being 90% all along WOT. It's 90% for Max along the WOT column. I think that should be okay, although I see what you are saying about using it to prevent hard spikes and/or overboost.

 

I think I'd personally prefer to leave it at 90% all the way through, for the rare occasion when I do mash the pedal out of idle and WGDC immediately opens up to 90% for a second to spool up. I do see that happening in my logs and right now, I think I was able to adjust TD to drop off quickly enough to not overboost/spike more than about 0.5 PSI, which I can accept. Will need to log more to see.

 

The tables you posted are weird. I guess it's different for the WRX than the LGT? In my RR, I don't have requested torque in the table. It's accelerator vs RPM, which I guess could be translated if I look at the DBW Accelerator vs Requested Torque table?

 

I don't seem to require as much of a dip in WGD in the saddle as the tables you posted either, but I guess it just varies for each car. My WGD seems kind of high... rather a lot higher than what Shamar tuned me for the last two times.

 

Also, I looked at the link you posted about Per Gear WGD, doesn't seem like that's available for my LGT.

 

Anyways, I'm still working on this, and I've been reading and rereading the stuff you've posted. Thanks so much!

 

That is exactly what I had to do with TD with my Infamous tune.

 

That is what I did with my own tune prior to my Infamous tune. I wound up leaving Max WGDC at 90 with my tweaked Infamous tune since TD and WGDC Comp. IAT were dialed in pretty good. I didn't notice much of a difference either way.

Good to know we're in the same boat... Interesting that Shamar didn't tune for that. Kind of disappointing really.

[black318i]

Yeah with all the praise here I was expecting at lease a decent tune, but I wound up having to fix several issues.

[fahr_side]

I've only worked on 5th.gen LGTs so I'm not too clear when they made the switch from throttle-angle to RT based boost control. That is an STi map btw, but general shape of the tables is the same regardless of year or model.

[Ridgeracer]

No tuner is ever going to put in the time needed to make anyone's tune consistent and knock free that the owner of the car would like. And on a side note..hta68 spools very well with a 3 port EBCS. Interrupt type EBCS removes any air pressure from the WG until you need it to open vs 2 port bleed type.

[fahr_side]

No tuner is ever going to put in the time needed to make anyone's tune consistent and knock free that the owner of the car would like.

Hehe. I am at close to 200 revisions on my own 16G tune. I don't want to think about what I'd have spent with a pro to go through five hardware revisions. :O

[iNVAR]

Okay, is there something wrong with my car or is this normal? It appears that even with 90% WGDC at WOT, 3rd gear, 4700 RPM, intake temp of 90F, I'm unable to meet boost targets. I know the VF40 runs out of steam, but... this can't be right.

 

Outside ambient about 77-82F. Feels kind of muggy so humidity's probably high. NYC elevation.

 

Log attached.

 

Normal or something wrong? WG spring too weak?

 

I pulled a log earlier this morning, on basically the same map (some minor changes to the TD... WGDC is all the same) and the temperature was cooler out. Around 67-70F. Intake read 77F. WGDC was lower and boost pressure was being met. I didn't get a pull all the way to redline in 3rd, but it's enough to do a quick comparison. What gives? Kind of feels like my WGDC are kind of high...

 

edit: Looked at some old logs from last summer... I think I may have answered my own question. The VF40 just runs out of steam huh?

edit2: From searching the forums some, some people say it's running out of steam, and that I can hold boost a bit better by getting a stronger spring.... but if I get a stronger spring, will it still be safe, as far as the turbo goes? I don't want the sucker to overheat or turn into a "flamethrower" as someone called it. My log shows that at 4500RPM, I'm already maxing out at 90% WG and unable to meet target boost of 17.5 PSI.

edit3: Did more reading, found this thread with lots of info:

http://legacygt.com/forums/showthread.php/power-level-psi-do-actually-need-bov-78034.html?p=1664598

Guess I got my answer. This is normal, VF40 is just way out of its efficiency range and flops. SO, do I need to revise my target boost tables or leave them alone? Obviously in the winter it'll probably be able to hold boost higher... so maybe just leave it?

out-of-steam.csv

morning.csv

[fahr_side]

That is probably as much as you can expect from the VF-40. Boost error is quite within acceptable range at 1.13psi maximum error after you are spooled. As you suggest, this error may well vanish with cooler weather. You can't expect the system to be able to hit the whole curve dead-on on every day of the year and under every conceivable condition.

 

If I would do anything at all to that it would be to try and tune out that slight overboost at around 3k6. That can cause timing to be pulled via knock correction, even the sensor hears nothing. You can lower your initial WGDC cycle and boost target very slightly at say 3k2 or 3k4 to avoid that. Even this could be considered to be nit-picking but with the time and tools to get it perfect I am likely to try. As with a lot of things you are going to get 90% of the way to perfection in the first couple of tries. The rest of the way takes a hell of a lot more time and effort, and truth be told not many owners are going to be able to tell the difference.

 

I haven't tuned a pre-'10 LGT or anything else with a VF-40 but this sort of boost curve is about what you'd expect from the similarly-sized TD04L-13T. It just starts falling off after about 4k5 and there isn't much you can do about it. With a lowest WGDC of 80% through the saddle and max of 90% everywhere else, I'd say you've maxed the turbo out. Yes you might make it hold out a little longer with a smaller pill, stronger spring, 3-port BCS or uprated actuator, but I wouldn't wring it's neck any further IIWY. You are still holding 12psi at redline which is 3psi more than I would tune the TD04 to do.

 

I don't know the older heads well enough to comment on your timing curve, though it's flatter and lower at high revs than what I can normally run on the D25 heads. It could easily be that Shamar had to hold back on the timing up there to allow you run that much boost. I really don't want to second-guess him as I don't know what his overall strategies are. In the big picture this looks like a very clean tune that you should be very happy with.

 

If this isn't enough then it's time for you to shop turbos!

[Infamous1]

+1

that is probably as much as you can expect from the vf-40. Boost error is quite within acceptable range at 1.13psi maximum error after you are spooled. As you suggest, this error may well vanish with cooler weather. You can't expect the system to be able to hit the whole curve dead-on on every day of the year and under every conceivable condition.

 

If i would do anything at all to that it would be to try and tune out that slight overboost at around 3k6. That can cause timing to be pulled via knock correction, even the sensor hears nothing. You can lower your initial wgdc cycle and boost target very slightly at say 3k2 or 3k4 to avoid that. Even this could be considered to be nit-picking but with the time and tools to get it perfect i am likely to try. As with a lot of things you are going to get 90% of the way to perfection in the first couple of tries. The rest of the way takes a hell of a lot more time and effort, and truth be told not many owners are going to be able to tell the difference.

 

I haven't tuned a pre-'10 lgt or anything else with a vf-40 but this sort of boost curve is about what you'd expect from the similarly-sized td04l-13t. It just starts falling off after about 4k5 and there isn't much you can do about it. With a lowest wgdc of 80% through the saddle and max of 90% everywhere else, i'd say you've maxed the turbo out. Yes you might make it hold out a little longer with a smaller pill, stronger spring, 3-port bcs or uprated actuator, but i wouldn't wring it's neck any further iiwy. You are still holding 12psi at redline which is 3psi more than i would tune the td04 to do.

 

I don't know the older heads well enough to comment on your timing curve, though it's flatter and lower at high revs than what i can normally run on the d25 heads. It could easily be that shamar had to hold back on the timing up there to allow you run that much boost. I really don't want to second-guess him as i don't know what his overall strategies are. In the big picture this looks like a very clean tune that you should be very happy with.

 

If this isn't enough then it's time for you to shop turbos!

[iNVAR]

Yeah, that's what I've been working hard to get rid of. I made some big changes today to the max and init WGDC tables as well as the boost targets, so I'll see what happens.

 

I did as you said and lowered initial WGDC in the saddle in an attempt to control the overboost. When I looked closely at my logs and traced the map, I could see that TD Int was VERY high at 25-30% throttle due to the map demanding about 12PSI, which was not going to happen at the Init WGDC that my map had... So it was trying to overcompensate. When I mashed the pedal, TD Int was still wound up and didn't wind down quickly enough and TD Prop shot up too.

 

I've since adjusted the Init WGDC table to properly match my Boost Target table, which I've also reduced at the 30% throttle/3200-3400 range. RidgeRacer had suggested this earlier on in some PMs (12PSI doesn't seem 'realistic' at 30% throttle) and I didn't really understand or want to make the adjustment then. NOW I understand a lot more and can make the adjustments.

 

Again, thanks for the input, everyone!

[fahr_side]

I've since adjusted the Init WGDC table to properly match my Boost Target table, which I've also reduced at the 30% throttle/3200-3400 range. RidgeRacer had suggested this earlier on in some PMs (12PSI doesn't seem 'realistic' at 30% throttle) and I didn't really understand or want to make the adjustment then. NOW I understand a lot more and can make the adjustments.

 

Again, thanks for the input, everyone!

Yeah, that is the sort of strategy I pursue. Get boost targets to a realistic degree, set initial WGDC to get you very close to the target and reduce TD interventions to a minimum.

Let me give you a little tip on how to get to that. Do long logs in specific load ranges... try to get as much time logged as you can say in low load / low rpm driving, then high load / low rpm and so on until you've covered all the throttle / rpm possibilities. Use Excel to filter the logged data into areas that center around the cells in the initial boost target table. So say you want to work on the 3k2 rev range, then filter data between say 3k and 3k4. Then filter the throttle angle down to a range around the column headers on your table, like say 48% to 52% to center around a 50% column. Then discard the outliers, then average the actual boost seen and revise your target to that value. Do this for all cells up to about 70% throttle and then extrapolate the values between that column and the 100% column. You'll have to go back and smooth that map and it's easiest to do that with Airboy's spreadsheet. It's okay to set the targets in the off-boost areas just a little high so you don't see timing corrections.

 

Once you've done this, you can log again and see how TD is having to intervene, then you can work on the initial WGDC table in the same way as the boost target table, except using the actual WGDC data you logged.

 

Anyway, this is basically how I do it. More than one way to skin a cat and so on. This is what makes the tune super smooth. It's a lot of work but if you're as obsessive-compulsive as I am...

[iNVAR]

Yeah, that's pretty much what I've been trying to do, except the fluctuations in temperature are throwing off my WGDC. Temperatures in the morning (when I go to work) compared to the afternoon (after work) span a range of about 15F, and intake temperatures themselves vary by almost 20F, ugh. It seems to be affecting the needed WGDC for target boost by a pretty good amount.

 

I'm wondering if I should make some further adjustments to the WGDC IAT comp table. It seems like I really should so that TD won't have to intervene so much.

[fahr_side]

Yeah, that's pretty much what I've been trying to do, except the fluctuations in temperature are throwing off my WGDC. Temperatures in the morning (when I go to work) compared to the afternoon (after work) span a range of about 15F, and intake temperatures themselves vary by almost 20F, ugh. It seems to be affecting the needed WGDC for target boost by a pretty good amount.

 

I'm wondering if I should make some further adjustments to the WGDC IAT comp table. It seems like I really should so that TD won't have to intervene so much.

Where I live we don't see a huge difference in day / night temps, maybe 12~15*C tops and then only in winter. I have never, ever had to mess with the IAT comps on any car I've tuned here. I am using Eric Minehart's atmospheric pressure comps as there are roads as high as 3,000m.

I try to do my logging drives in roughly the same temps and if it isn't possible I just add or subtract the comp values from the logged WGDC values to come up with my latest initial target. Maybe if you focus on driving a particular way one morning to grab as much data as possible on one area, and then something different the next day and so on until you have the data you need. In order to get data I have resorted to loading the car up with various stuff in the garage just to make a payload to get to higher loads, and driving waaay out of my way to climb hills etc.

 

IOW, I'd try to grab data in consistent temperatures and / or defeat the comps with simple arithmetic before messing with the IAT comps. The easiest way to lose the rabbit is to change too many things at once.

 

Work is the curse of the tuning enthusiast I'm afraid.

[bmx045]

the temps here, just recently, went from 80* F to 50* the next day. Today it's right in the middle.

[iNVAR]

Still working on the tune, slowly, but meticulously.

 

I ran into two issues that maybe someone can help me with.

1st - I seem to overboost at low RPM, 30%-45% throttle, between 2000-3000 RPM, in 3rd or higher gear and TD maxes out and still can't get boost lowered. I end up being between 1-5PSI overboosted. Target boost levels are set pretty low in that region, between 2-6PSI, Init WGDC are set between 50-65% range. I did a comparison to MickeyD's stage 2 tables and my numbers aren't that far off from his. Our target boost levels are almost the exact same, and the WGDC too. What gives? Is this normal and necessary to achieve boost in the lower gears at partial throttle?

 

Second question somewhat (but not really related) I noticed an issue:

During one of my partial throttle logging sessions, I was overboosting as described above, and TD was subtracting lots of WGDC. Check out the log:

At some point, I seem to hit a wall at 50.2% WGDC and my boost keeps rising. TD integral did NOT hit the ceiling until much later, but for some reason, WGDC refused to lower any.... Why?

 

Check it out on row 19. TD Int is -15.57, WGDC 50.2%. TD int keeps going farther negative but WGDC is stuck at 50.2%!

wgdc-stuck.csv

[Ridgeracer]

Yeah, I'm also afflicted with a little OCD but try to keep it in check.

 

I like to keep initial WGDC after the saddle just a little lower than can hold the boost target... just enough to keep TD prop down in single digits and TD int at near zero.

The max TD int value I will use depends on a few things. Small turbos with 3-ports only need max 15% as it's easy to overdo it. Bigger turbo and or stock BCS can take 18 or even 20% to get proper control authority.

IMO it's best to set realistic boost targets and tune initial WGDC carefully to reduce TD intervention to very small positive values. I like to limit max WGDC to 3~5% above initial through the saddle and slowly open that out at higher rpm. Smaller turbos are especially sensitive to control input through the saddle and any clumsy intervention here from TD will see boost bouncing up and down dramatically.

One the great side-effects of per-gear boost control is being able to keep the max WGDC values much closer to the initial values because large TD interventions are never needed.

 

Interesting to read someone else's boost strategy. I did alot of work with mickeyd setting up my boost control for my HTA68 and Prodrive 3 port. This involved alot of consistent pulls in both 3rd and 4th gear. For proportional + we used 26 and integral 15. Initial tables are set up to where proportional max out during large boost error during spool up and integral start to accumulate. Once the error decreases and I start to hit targets till redline my integral stays around 15. I can see the benefit to the per gear tables then I wouldn't have to keep integral accum max through a pull.

[fahr_side]

I seem to overboost at low RPM, 30%-45% throttle, between 2000-3000 RPM, in 3rd or higher gear and TD maxes out and still can't get boost lowered. I end up being between 1-5PSI overboosted. Target boost levels are set pretty low in that region, between 2-6PSI, Init WGDC are set between 50-65% range. I did a comparison to MickeyD's stage 2 tables and my numbers aren't that far off from his. Our target boost levels are almost the exact same, and the WGDC too. What gives? Is this normal and necessary to achieve boost in the lower gears at partial throttle?

I don't usually use that much initial WGDC in that area but every car is different and everyone has their own objectives and methods. Maybe ask Shamar why he did that? I really don't want to second-guess him.

I would just lower the initial and max WGDC values in that area to avoid TD maxing out, but that's just me.

At some point, I seem to hit a wall at 50.2% WGDC and my boost keeps rising. TD integral did NOT hit the ceiling until much later, but for some reason, WGDC refused to lower any.... Why?

 

Check it out on row 19. TD Int is -15.57, WGDC 50.2%. TD int keeps going farther negative but WGDC is stuck at 50.2%!

Remember that TD prop deals with short-term and small-value errors. TD integral is the big brother that steps in when TD prop seems to be losing the fight. TD integral is triggered when errors are large and / or persistent, takes longer to wind up and down once awoken.

 

What is your biggest negative value in the TD integral cumulative range (WGDC correction) table? If I understand it correctly, TD integral's corrections are limited by the values in this table. IIRC the stock maximum negative value is -90% which I think would be able to reduce WGDC to almost zero. If your tuner has changed this there may be a very good reason, like an attempt to stop big swings in boost. Check before you change this!

 

Initial tables are set up to where proportional max out during large boost error during spool up and integral start to accumulate. Once the error decreases and I start to hit targets till redline my integral stays around 15. I can see the benefit to the per gear tables then I wouldn't have to keep integral accum max through a pull.

Yes, that sounds healthy.

When per-gear is not used (or possible) the issue is that TD has to be able to compensate for the vastly different loads presented by all 5 gears, plus factors like hills, extra passengers etc.

When you tune boost in (say) 3rd gear you have to find that balance between getting the best spool you can in 3rd, which means setting slightly high initial WGDC values, while not seeing overboost in 4th because TD can't pull back far enough or fast enough. Tune for 4th gear and initial WGDC may be a bit low for 3rd gear and make spool slow, cause a huge TD intervention which in turn causes a spike once TD integral is all wound up positive. In this scenario you can see it would be better to have a big positive intervention to hold boost up to target in 3rd rather than have a big negative intervention in 4th to hold boost down to target.

 

A 3-port makes the problem easier to solve but the per-gear approach really is the way to go, if the tables are there and defined.

[Infamous1]

I don't usually use that much initial WGDC in that area but every car is different and everyone has their own objectives and methods. Maybe ask Shamar why he did that? I really don't want to second-guess him.

I would just lower the initial and max WGDC values in that area to avoid TD maxing out, but that's just me.

 

Every car is different and every customer wants a different type of throttle/boost response. If it isn't communicated to me I just go with the standard base which is related to the mods list given. Also partial throttle logs usually aren't conducted unless there is a glaring issue. This is now outside of your typical tuning; dyno, road or anything. This is definitely fine tuning which only an owner can and really should do. If I were paid by the hour this bill would be tremendous.