1.1.81 VEMS boost control

[A80Avant]

what is everyone using hardware wise and PID settings wise?

so far i have tried using 16hz and 21hz. I had asked in the past about this people at turbosmart and searching the emails found that their recommendation was to use 10hz. I havent tried this yet, but ill give it a go.

on 21hz boost builds up fast and oscillates until hitting the target for a few rpm.

PID that i have tried so far are: 200+/30-70/30-80. In all configurations i get the same result.

what is everyone else using? I have also tried marc's and Mattias PID config without any success.

[A80Avant]

it used to be that with the P high, you could get the boost to rise up fast. I suppose if you use 31hz you dont need so big P.

do you get the boost oscillating at all before reaching target? and how much boost have you tested so far?

[A80Avant]

i have tried to configure the boost without the PID first after instruction from various different tuners. With a DC of about 77% i get 290-300kpa BUT it comes on fairly later than what the turbo is capable of. On 3d gear instead of 4000-4100 which i used to have, it comes on to about 4700rpm. I will try increasing the DC on the rpms before the actual peak boost to see what happens.

I guess there is no easy way as to try introducing some PID in there and see the reaction. Perhaps i will lower the boost to something like 1.5bar (250kpa) and play around that area so that i dont have any unecessary stress to the engine doing fast runs everyday, and configure it. Boost control was much easier on megatune and pity vems hasnt come up with a guide for the pid tuning of that.

i can see an electronic boost controller smilling at me from the corner....

Actually, other than vems being able to lower boost as a safety feature, what else is there involved with boost and safety in VEMS? In otherwords, someone using a simple bleed valve or an electronic boost controller, is the only downside this above feature? Cause VEMS can be safer by adding more fuel as well, which does not affect the use of an external boost controller. Boost cut should still work, as VEMS will be seiing boost levels anyway.

[A80Avant]

after some more tests yesterday, here are the results:

1) PID=0 : increased DC from 85-100% from 2500-3500rpm---> boost was slightly improved on 3d gear, but overshot all higher gears.

2) After several attempts and tests, settled to PID: 90/6/28 and DC around 80 up to 3600 then 77 thereafter. This started bringing up boost a bit faster(unfortunatelly log failed and i cannot see the difference as i was looking at the road and rev counter at the time!) . It proved to me after restudying PID control, that once you set a P value, if you have a large I the most likely thing to happen is to overshoot. D can suppress that, but at the end of the day it wont work all the time and you will have to sacrifice your I.

Towards the end of my runs i started increasing the P values with having the I fairly low and it seemed that, that was the way to go. So i will retest all this.

When reading through manuals of electronic boost controllers, it seems that there is a function in them that is called Gate Pressure(turbosmart) and that may well be part of a PID system along with another function called Sensitivity(which eliminates oscillations). However you get the impression that the only way to tackle the problem with boost control on vemstune is to just fit a stiffer spring. I hope this is not the case, as megatune did give me better results with the current spring (about 0.5bar) and no fuss.

What i havent tried yet is the ANYTRIM control that Marc has hooked up for me. Once i reach the levels of PID control that are acceptable, i will connect that to see if there is any improvement on this. Im hoping to resolve this one way or the other. I know its not a big difference (now about 100-200rpm) but i hate to loose something like spool, esp on laggy turbos!! haha

anyway, im happy reporting here on vemstune attempts. I hope others do the same. I havent seen too much activity lately...

[A80Avant]

although the theory above is correct and confirmed to me by 1-2 people apparently it doesnt seem to work in practice.

i have tried all possible combinations i can think of and boost just doesnt build up any sooner, even with a PID combination that was tried before and did produce better results! So i am at a loss with this one on vems.

I tried the anytrim yesterday unsuccesfully for the first time. I used PID settings which without anytrim they give me a fair result, later boost but high and stable, but with anytrim no matter what the position of the potentiometer was, no matter how big the multiplication was, i reached it up to 200% and only then it managed to reach 260-270 kpa. Tried changing the PID settings a bit, and it oscillated. SO anytrim needs to be explained to me a bit further to understand it's functionality otherwise it seems stupid to me to have to still use PID to use anytrim, and even then not be able to do as good or better than before. Boost multiplication as i understand it should multipply DC or something to generate more boost reaction etc. On logs i saw DC being 100% and boost being as high as my wastegate spring! As if the solenoid valve was off or something. Maybe that is how it works,but i dont understand it still...

i tried a second solenoid as well just in case i was wrong, but it gives me same results.

Next step would be to go to a stiffer spring+ solenoid
Then turbosmart boost tee +/- stiffer spring.

[diesel des]

Is your boost control output inverted? It was with mine and 100% gave spring boost value....

[Reidar]

I`ve only tuned the N75 valve, but tuned it on several cars.

What I dont fully get is your DC table. you say 80% up to 3600 and 77% thereafter.
Why dont you run 100% untill your turbo would actually start to kick in? and then lower the DC?

My biggest problem tuning these is when running a big turbo in the 650-700hp range. In firstgear I dont expect much boost at all on low revs, but in third gear the turbo would spool at much lower revs. Here it`s difficult to gain maximum spool at first and secondgear, without overshooting in third. This is where the PID control gets usefull.

Since we are sharing experiences here, I`ll type a quick "how I do it"

First off.. I ALLWAYS adjust the WG springpressure to aprox 2/3 or 3/4 of maximum boost. I do this by simply removing the N75 valve and running a hose directly from the turbo to the WG. We can allso just set the Ref-DC table to 0%, atleast if we dont got an inverted output and if the valve is completly open at "power off".
Let`s make an example: I want maximum boost to be 2 bar, so i then set the spring pressure to 1.5bar.

I often dont got a clue how fast the turbo will spool on different cars/engines. There are simply just to many factors to just know this without testing I think. So my next step in line is to find out how fast it will spool with a completly shut WG. I do this by simply removing the hose to the WG or set the ref-dc table to 100%.
If I`m not driving my self i set a fuelcut at boost above 2bar.
Now I`m ready to do a LOG and see how fast the turbo will spool, and it will give me an ide of how my ref-dc table should look like. By shutting the WG i will know how fast the turbo will spool at this setup, it`s not possible to have it spool any faster without doing changes to the engine or map. I do this test in 3.gear and maybe going a bit uphill.

Now it`s time to analyze the log, and check out at what revs the turbo kicks in for real. Let`s say we got 1.5bar of boost at 4000 rpm and 2bar at 4200rpm.
I will then know that my ref-dc cant be 100% at any more than 3800rpm or so. I do this with the PID disabled offcourse, so I dont get any interference from it.
By setting the ref-dc to 100% all the way to 3800rpm, we will keep the WG shut and we would gain maximum spool in this gear. We dont want an airleak to the WG when spooling the turbo, that will only slow things down.

I do some pulls in higher gears just to check that it wont overshoot to much. Now third, fourth, fifth and sixthgear pulls should be quite good, but first and second might lack some spool cause we now flow air to the WG after 3800rpm, and that is to early in first and second. This is where i start to tune the PID settings. I never seem to get the same settings on cars, so I cant give a good answer how a prefect PID tune shuld look like. But when I`m done, it`s usually quite good I think compared to bleedvalves and such

Reidar

[A80Avant]

good info Reidar,

i have tried using 100% DC and it didnt work. It overshoot and spiked most of the times on higher gears. I also do not use the WG spring in that sense that you do, and i find no difference. I use a heavy duty WGFV instead of the N75 same as those that electronic boost controllers use, and i also plug the top chamber of the WG, so i dont bother making the spring stiffer.

I did the test to see how fast is my spool on the turbo with direct connection of the hose that goes from the turbo to the top chamber of the WG and got excactly the same spool

By keeping the initial DC to around 88% PID is taking care if it needs to be 100% on lower gears or less. But that is only my car with my turbo and setup. It may be that other cars may need to be tuned differently.

[Reidar]

I`m not sure how that will work with the top champer blocked, compared to the way I do it. The reason I use a spring pressure at 3/4 of max boost, is to make the aerea of adjustemnts from the boostkontroller smaller. This way I can use the boostcontroller to "fine tune" the boost, and not to totally control it over the whole rev-range. Now my valve need to controll 0.5bar of boost insted of 1.5bar, and perfect the spool, if you understand what I`m thinking

I think it`s important that when setting the DC to 100%, you cant set it at a place where your turbo would actually spool in heavy load/high gears. If your turbo is able to reach 2bar at 3500rpm in 6th, you cant have 100% DC at 3500 rpm. Then it will spike for sure, since the valve is closed.

I did some testing on the valve Fhz. I ended up using 25hz, on the n75 valve. But I`m not sure if that`s the best value for that valve, all i know is-> it works for me I allso got some valves laying around for other electronic boostcontrollers, but I never bothered changing them since the n75 worked so good.

I allso think it`s importatnt that the boost targert is quite equal to the actuall boost you get from your ref-dc. so at low revs, you dont set the target to 2bar, since it`s impossible to reach 2bar at 2000rpm.
This is from a car i did a whileback, running a 3071 on a 2.5liter



Reidar

[dkw_dude]

I am pretty much doing the same. WG spring to ~0,8-1 Bar, then n75/PID controller in VEMS to adjust the last bit of boost (running 1,5 Bar). From memory I think P=110 I=45, D=0. And DC ref table adjusted after some logged runs to see where actual DC ends up. I have ~0,1 bar or so of overshoot (?) before it settles quite ok on boost target.

[A80Avant]

yes, the target boost is supposed to be there so that the PID knows where the boost is supposed to go.

if you use target boost curve =0 then the boost is only managed as an open loop on the DC alone.

As you said, with the PID settings i have so far, i am able to get the DC 100% but because the PID is doing so, not because my ref DC is 100. This way i am giving PID the option to reduce it on higher gears and not spike.

i use a 0.5-0.6bar spring and works nice at the moment.

anyone had to change boost settings when going from 1.1.81 to 1.1.88?

[Jamo]

What have you used for settings at the moment? boost target in 0 and the PID and ref DC or still got values in boost target?

[A80Avant]

At the moment I use values in all fields, PID,refDC,boost Target.

However the car has developed some increased backpressure forbsome reason and boost is tailing off fast after 5500rpm. I have to investigate why that is. Could be a blocked exhaust, cats, or blown turbo? Or something relating to the poor PCV configuration I have....

Possibly may not even make the dynoday...